The fundamental objective of our work is to design, synthesise and
characterise new materials for which different physical properties
such as magnetism, electric conductivity, optical properties etc.
are combined in a synergistic way.
A new focus lies on the topic "on-surface synthesis", in strong collaboration with research teams in physics.
The following abstracts of a few selected publications give an
overview of our main research fields.
Spin Excitations of High-Spin Iron(II) in Metal-Organic Chains on Metal and Superconductor
J.-C. Liu, C. Li, O. Chahib, X. Wang, S. Rothenbühler, R. Häner, S. Decurtins, U. Aschauer, S.-X. Liu, E. Meyer, R. Pawlak, arXiv:2409.20312v1 [cond-mat.mtrl-sci], submitted on 30 Sep 2024. online version
Abstract:
We use on-surface coordination chemistry to synthesize on Ag(111) and superconducting Pb(111) iron-based spin chains that reveal low-energy spin excitations.
Nanoscale Control of Quantum States in Radical Molecules on Superconducting Pb(111)
C. Li, V. Pokorny, M. Zonda, J.-C. Liu, P. Zhou, O. Chahib, T. Glatzel, R. Häner, S. Decurtins, S.-X. Liu, R. Pawlak, E. Meyer, arXiv:2408.05115 [cond-mat.mes-hall], submitted on 9 Aug 2024. online version
Abstract:
Here we show the manipulation of magnetic states in the radical molecule 4,5,9,10-tetrabromo-1,3,6,8-tetraazapyrene on a Pb(111) superconducting surface. The presence of several molecules allows tuning of the YSR state position by altering the relative distance. This study also elucidates the interaction between molecular assemblies and superconducting substrates, paving the way for advanced quantum-state engineering.
Hexadecanuclear isobutyrate nanoclusters with a {CoII14CoIII2} core
D. Stati, J. van Leusen, V. Ch. Kravtsov, K. Krämer, S.-X. Liu, S. Decurtins, P. Kögerler, S. G. Baca, CrystEngComm, 2024, 26(32), 4264-4271 and 4251. online versionPDF
and
PDF (Front Cover)
Abstract:
A new hexadecanuclear nanocluster with a mixed-valence {Co16} core has been prepared and fully characterized. Predominantly intracluster ferromagnetic exchange interactions were measured.
Time-resolved THz Stark spectroscopy of molecules in solution
B. J. Kang, E. J. Rohwer, D. Rohrbach, E. Zyaee, M. Akbarimoosavi, Z. Ollmann, G. Sorohhov, A. Borgoo, M. Cascella, A. Cannizzo, S. Decurtins, R. J. Stanley, S.-X. Liu, T. Feurer, Nature Commun., 2024, 15, 4212/1-7. online versionPDF
Abstract:
Here we demonstrate time-resolved THz spectroscopy, utilizing intense single-cycle terahertz pulses as electric field source, whereby we verify THz Stark spectroscopy.
2023
Self-Assembly of N-Rich Triimidazoles on Ag(111): Mixing the Pleasures and Pains of Epitaxy and Strain
Aisha Ahsan, Xing Wang, Rejaul Sk, Mehdi Heydari, Luiza Buimaga-Iarinca, Christian Wäckerlin, Elena Lucenti, Silvio Decurtins, Elena Cariati, Thomas A. Jung, Ulrich Aschauer, Shi-Xia Liu, J. Phys. Chem. C, 2023, 127(47), 23000-23009. online versionPDF
and
PDF (Inside Cover)
Abstract:
Hydrogen-bonded assemblies of N-doped heterocyclic triimidazole molecules on a Ag(111) substrate were investigated using scanning tunneling microscopy (STM) and low-energy electron diffraction (LEED) techniques. The LEED data are consistent with simulations based on a distinct overlayer on the Ag(111) lattice. Density functional theory (DFT) calculations support the experimental results.
High Pressure Behaviour of the Organic Semiconductor Salt (TTF−BTD)2I3
F. Montisci, A. Lanza, M. Fisch, C. Sonneville, Y. Geng, S. Decurtins, C. Reber, S.-X. Liu, P. Macchi, Phys. Chem. Chem. Phys., 2023, 25(45), 31410-31417. online versionPDF
Abstract:
We studied TTF−BTD at temperatures ranging from 300 K to 90 K and at pressures up to 7.5 GPa, using both X−ray diffraction and Raman spectroscopy to determine the properties of the compressed sample. Periodic DFT calculations were employed to characterize the calculated structural modifications and to predict the structural changes up to 60 GPa.
Gate-tunable topological superconductivity in a supramolecular electron spin lattice
J.-C. Liu, C. Li, R. Hess, H. Chen, C. Drechsel, P. Zhou, R. Häner, U. Aschauer, T. Glatzel, S. Decurtins, D. Loss, J. Klinovaja, S.-X. Liu, W. Wulfhekel, E. Meyer, R. Pawlak, arXiv:2310.18134 [cond-mat.supr-con], submitted on 27 Oct 2023. online version
Abstract:
We showcase the supramolecular assembly of radical molecules on Pb(111). Charged molecules carry a spin-1/2 state, as confirmed by observing Yu-Shiba-Rusinov in-gap states. Low energy modes are localized at island boundaries with long decay towards the interior, whose spectral signature is consistent with Majorana zero modes protected by mirror symmetry.
Photoinduced Asymmetric Charge Trapping in a Symmetric Tetraazapyrene-Fused Bis(tetrathiafulvalene) Conjugate
P. Zhou, M. N. H. Pashaki, H.-M. Frey, A. Hauser, S. Decurtins, A. Cannizzo, T. Feurer, R. Häner, U. Aschauer, S.-X. Liu, Chem. Sci., 2023, 14(44), 12715-12722. online versionPDF
Abstract:
A detailed study of the electronic interactions between TTF and tetraazapyrene units in the ground and excited states was performed using ultrafast transient absorption spectroscopy.
Strong signature of electron-vibration coupling in molecules on Ag(111) triggered by tip-gated discharging
Chao Li, Christoph Kaspar, Ping Zhou, Jung-Ching Liu, Outhmane Chahib, Thilo Glatzel, Robert Häner, Ulrich Aschauer, Silvio Decurtins, Shi-Xia Liu, Michael Thoss, Ernst Meyer, Rémy Pawlak, Nature Commun., 2023, 14, 5956/1-8. online versionPDF
Abstract:
Electron-vibration coupling is of critical importance for the development of molecular electronics, spintronics, and quantum technologies, as it affects transport properties and spin dynamics. Here we show the vibronic excitations of tetrabromotetraazapyrene molecules directly adsorbed on Ag(111) into an orientational glassy phase.
Merging of Azulene and Perylene Diimide for Optical pH Sensors
Ping Zhou, Ulrich Aschauer, Silvio Decurtins, Thomas Feurer, Robert Häner, Shi-Xia Liu, Molecules, 2023, 28(18), 6694/1-11. online versionPDF
Abstract:
Two azulene moieties were incorporated into a PDI core either through single bonds or by fusion, leading to the corresponding triads. Their electronic and optical properties were experimentally and theoretically investigated.
{Mn6IIIMnIVDy2III} Single-Molecule Magnet Based on Cubane Subunits
Mariana Darii, Jan van Leusen, Victor Ch. Kravtsov, Yurii Chumakov, Karl Krämer, Silvio Decurtins, Shi-Xia Liu, Paul Kögerler, Svetlana G. Baca, Cryst. Growth Des., 2023, 23(9), 6944-6952. online versionPDF
Abstract:
The heterometallic mixed-valence nonanuclear cluster was prepared using Mn(II) pivalate as the starting material. The magnetic properties of the crystalline cluster compound were studied experimentally and theoretically and showed a slow relaxation behavior with an effective energy barrier of 15.2 K and τ0 = 1.4 x 10-7 s.
The Simple Geometry That Predicts Molecular Mosaics
Abstract:
By treating molecules as geometric tessellations, we devised a new way to forecast how 2D materials might self-assemble.
Atomically Well-defined Nitrogen Doping in the Cross-plane Transport through Graphene Heterojunctions
H. Zhang, P. Zhou, A. Daaoub, S. Sangtarash, S. Zhao, Z. Yang, Y. Zhou, Y.-L. Zou, S. Decurtins, R. Häner, Y. Yang, H. Sadeghi, S.-X. Liu, W. Hong, Chem. Sci., 2023, 14(22), 6079-6086. online versionPDF
Abstract:
Atomically well-defined N-doped graphene heterojunctions were fabricated, and cross-plane transport was studied to reveal the effects of doping on the electronic properties of the molecules.
Polygonal tessellations as predictive models of molecular monolayers
Krisztina Regös, Rémy Pawlak, Xing Wang, Ernst Meyer, Silvio Decurtins, Gábor Domokos, Kostya S. Novoselov, Shi-Xia Liu, Ulrich Aschauer, PNAS, 2023, 120(16), e2300049120/1-5. online versionPDF
Abstract:
Single-layer materials may be represented by a hierarchical geometric model, consisting of (parts of) polygonal mosaics on multiple scales. In the Figure below, the cell degree v counts the vertices of a polygon, the nodal degree n counts the polygons overlapping at a vertex. The model provides a different view of self-assembled molecular patterns.
Proximity-Induced Superconductivity in Atomically Precise Nanographene on Ag/Nb(110)
J.-C. Liu, R. Pawlak, X. Wang, H. Chen, P. D'Astolfo, C. Drechsel, P. Zhou, R. Häner, S. Decurtins, U. Aschauer, S.-X. Liu, W. Wulfhekel, E. Meyer, ACS Materials Lett., 2023, 5, 1083-1090. online versionPDF
Abstract:
A metal-superconductor hetero-structure was fabricated consisting of a Nb(110) substrate covered with a thin Ag film. Robust proximity-induced superconductivity was observed on the Ag layer. STM/AFM at low temperatures were used to characterize the molecular frameworks formed by on-surface reactions.
2022
Time-resolved THz Stark spectroscopy
B. J. Kang, E. J. Rohwer, D. Rohrbach, M. Akbarimoosavi, Z. Ollmann, E. Zyaee, R. F. Pauszek III, G. Sorohhov, A. Borgoo, M. Cascella, A. Cannizzo, S. Decurtins, R. J. Stanley, S.-X. Liu, T. Feurer, arXiv:2212.10333 [physics.optics], submitted on 20 Dec 2022. online version
Abstract:
We introduce THz Stark spectroscopy by using intense single-cycle terahertz pulses as the electric field source and monitoring the induced spectral response of an isotropic molecular ensemble with a coincident femtosecond supercontinuum pulse.
Polygonal tessellations as predictive models of molecular monolayers
K. Regos, R. Pawlak, X. Wang, E. Meyer, S. Decurtins, G. Domokos, K. S. Novoselov, S.-X. Liu, U. Aschauer, arXiv:2208.03964 [cond-mat.mtrl-sci], submitted on 08 Aug 2022. online version
Abstract:
Here we introduce a simple, though rigorous, hierarchical geometric model founded on the mean-field theory of 2D polygonal tessellations to predict extended network patterns based on molecular-level information. Based on graph theory, this approach yields pattern classification and pattern prediction within well-defined ranges.
Quantum Interference-Controlled Conductance Enhancement in Stacked Graphene-like Dimers
P. Li, S. Hou, B. Alharbi, Q. Wu, Y. Chen, L. Zhou, T. Gao, R. Li, L. Yang, X. Chang, G. Dong, X. Liu, S. Decurtins, S.-X. Liu, W. Hong, C. J. Lambert, C. Jia, X. Guo, J. Am. Chem. Soc., 2022, 144(34), 15689-15697. online versionPDF
Abstract:
Here we present a case of two π-stacked anthanthrene monomers in a scanning tunnelling microscopic break junction. The conductance increases by as much as 25 in comparison with a monomer, which originates from a room-temperature quantum interference.
M. Darii, E. S. Beleaev, V. Ch. Kravtsov, P. Bourosh, Y. Chumakov, J. Hauser, S. Decurtins, S.-X. Liu, O. Sultanova, S. G. Baca, New J. Chem., 2022, 46(23), 11404-11421. online versionPDF
Abstract:
Several multicomponent compounds containing [Co(NH3)6]3+ were structurally characterized. They were also tested in vitro against Rhizobium (Agrobacterium) vitis, an ocogenic bacterium that causes tumor formation in plants.
Energy Dissipation from Confined States in Nanoporous Molecular Networks
P. D'Astolfo, X. Wang, X. Liu, M. Kisiel, C. Drechsel, A. Baratoff, U. Aschauer, S. Decurtins, S.-X. Liu, R. Pawlak, E. Meyer, ACS Nano, 2022, 16(10), 16314-16321. online versionPDF
Abstract:
Here we show the mechanical coupling between an atomic force microscope (AFM) and quantum states engineered in highly crystalline nanoporous molecular networks on Ag(111). We characterize their local density of states (LDOS) using scanning tunnelling microscopy (STM).
Flexible Superlubricity Unveiled in Sidewinding Motion of Individual Polymeric Chains
J. G. Vilhena, Rémy Pawlak, Philipp D'Astolfo, Xunshan Liu, Enrico Gnecco, Marcin Kisiel, Thilo Glatzel, Ruben Pérez, Robert Häner, Silvio Decurtins, Alexis Baratoff, Giacomo Prampolini, Shi-Xia Liu, Ernst Meyer, Phys. Rev. Lett., 2022, 128(21), 216102/1-6. online versionPDF
Abstract:
Exploiting their longitudinal flexibility, pyrenylene chains are shown to be able to lower diffusion energy barriers via on-surface directional locking and molecular strain. A combined AFM and MD simulation study.
Proximity-Induced Superconductivity in Atomically Precise Nanographene
Jung-Ching Liu, Rémy Pawlak, Xing Wang, Philipp D'Astolfo, Carl Drechsel, Ping Zhou, Silvio Decurtins, Ulrich Aschauer, Shi-Xia Liu, Wulf Wulfhekel, Ernst Meyer, arXiv:2202.00460 [cond-mat.supr-con], submitted on 1 Feb 2022. online version
Abstract:
Here, we present a synthetic method to induce superconductivity to polymeric chains and NGs adsorbed on the superconducting Nb(110) substrate covered by thin Ag films. AFM and scanning tunneling spectroscopy were applied to characterize the structures and elucidate their electronic properties.
Exploiting Cooperative Catalysis for the On-Surface Synthesis of Linear Heteroaromatic Polymers via Selective C-H Activation
Xunshan Liu, Adam Matej, Tim Kratky, Jesus I. Mendieta-Moreno, Sebastian Günther, Pingo Mutombo, Silvio Decurtins, Ulrich Aschauer, Jascha Repp, Pavel Jelinek, Shi-Xia Liu, Laerte L. Patera, Angew. Chem. Int. Ed., 2022, 61(5), e202112798/1-6. online versionPDF
Abstract:
Selective C-H activation for dehydrogenative C-C couplings of hexaazatriphenylenes by Scholl reaction is reported. By combining low-T STM and AFM techniques, the formation of one-dimensional polymers with a double-chain structure could be revealed, which was also rationalized by DFT calculations.
2021
Effect of tert-butyl groups on electronic communication between redox units in tetrathiafulvalene-tetraazapyrene triads
Ping Zhou, Ulrich Aschauer, Silvio Decurtins, Thomas Feurer, Robert Häner, Shi-Xia Liu, Chem. Commun., 2021, 57(96), 12972-12975. online versionPDF
Abstract:
The electronic effect of tert-butyl groups on intramolecular through-bond interactions between redox units in tetrathiafulvalene-tetraazapyrene (TAP) triads is investigated. The TAP localized LUMO level is raised by 0.21 eV, which agrees well with DFT calculations.
Self-Assembly and Magnetic Order of Bi-Molecular 2D Spin Lattices of M(II,III) Phthalocyanines on Au(111)
Miloš Baljozović, Xunshan Liu, Olha Popova, Jan Girovsky, Jan Nowakowski, Harald Rossmann, Thomas Nijs, Mina Moradi, Fatemeh Mousavi, Nicholas C. Plumb, Milan Radović, Nirmalya Ballav, Jan Dreiser, Silvio Decurtins, Igor A. Pašti, Natalia V. Skorodumova, Shi-Xia Liu, Thomas A. Jung, Magnetochemistry, 2021, 7(8), 119/1-15. online versionPDF
Abstract:
Surface supported two-dimensional binary spin arrays on Au(111) were investigated by spectro-microscopy (scanning tunneling microscopy, X-ray absorption spectroscopy, X-ray magnetic circular dichroism) and theory (DFT calculations).
Intramolecular Charge-Transfer Dynamics in Benzodifuran-Based Triads
Stephan Keller, Jihane Hankache, Oleksandr Yushchenko, Latévi Max Lawson Daku, Qinchao Sun, Jie Ding, Silvio Decurtins, Eric Vauthey, Robert Häner, Andreas Hauser, Shi-Xia Liu, Helv. Chim. Acta, 2021, 104, e2100099/1-13. online versionPDF
Abstract:
The synthesis of new conjugated electron donor-π-acceptor chromophores is presented. A combination of cyclic voltammetry, spectroelectrochemistry, UV-vis and ultrafast transient absorption spectroscopy has been applied to reveal their excited-state dynamics.
Bis(triphenylamine)benzodifuran Chromophores: Synthesis, Electronic Properties and Application in Organic Light-Emitting Diodes
Abstract:
A series of bis(triphenylamine)benzodifuran chromophores has been synthesized and the electronic absorption, photoluminescence and redox properties were investigated. A representative compound has been applied as a dopant emitter in organic light-emitting diodes (OLEDs). A yellowish-green OLED exhibits a high external quantum efficiency (EQE) of 6.2%.
Polynuclear Clusters Based on Fe/Fe-Ln Carboxylates with Selected Magnetic Properties
Svetlana G. Baca, Susan Herringer, Shi-Xia Liu, Silvio Decurtins,
in "Comprehensive Coordination Chemistry III";
Elsevier, Reference Module in Chemistry, Molecular Sciences and Chemical Engineering; ISBN: 978-0-12-409547-2; 2021, 1-37. online versionPDF
Abstract:
This chapter in "Comprehensive Coordination Chemistry III" provides an overview about the development on design and characterization of polynuclear clusters, ranging from homometallic Fe-based carboxylate clusters of various nuclearities to heterometallic Fe-Ln carboxylate clusters with trinuclear to tridecanuclear structures.
Optically Controlled Electron Transfer in a Re(I) Complex
Egmont J. Rohwer, Yan Geng, Maryam Akbarimoosavi, Latévi Max Lawson Daku, Olivier Aleveque, Eric Levillain, Jürg Hauser, Andrea Cannizzo, Robert Häner, Silvio Decurtins, Robert J. Stanley, Thomas Feurer, Shi-Xia Liu, Chem. Eur. J., 2021, 27(17), 5399-5409. online versionPDF
Abstract:
Ultrafast optical control of intramolecular charge flow is demonstrated with a fac-[Re(CO)3(TTF-DPPZ)Cl] complex. DFT calculations, ultrafast transient absorption measurements and AC-Stark spectroscopy confirm the presence of two distinct optically active charge-transfer processes.
On-Surface Synthesis of Nitrogen-Doped Kagome Graphene
Abstract:
We report the on-surface reaction on Ag(111) for the synthesis of two-dimensional N-doped graphene sheets possessing a honeycomb Kagome lattice. STM, AFM and DFT methods are applied to scrutinize the structural and electronic properties. We demonstrate the semiconducting character of the lattice and the emergence of Kagome flat bands near the Fermi level.
Formation of Defect-Dicubane-Type NiII2LnIII2 (Ln = Tb, Er) Clusters: Crystal Structures and Modeling of the Magnetic Properties
Zhonglu You, Krunoslav Prsa, Julius Mutschler, Susan N. Herringer, Jiaqi Wang, Yingying Luo, Boyang Zheng, Silvio Decurtins, Karl W. Krämer, Oliver Waldmann, Shi-Xia Liu, ACS Omega, 2021, 6(1), 483-491. online versionPDF
Abstract:
Particular emphasis is given to the theoretical description of the magnetic behavior of the tetranuclear cluster, taking into account the Ln-Ni and Ni-Ni coupling paths and the magnetic anisotropy of the LnIII and NiII ions. The study is distinguished for its discussion of two distinct models, whereby model A relies on the uniaxial B20 Stevens term describing the lanthanide anisotropy and model B is based on point-charge model calculations. Importantly, the physical meaning of the obtained parameters for both models was critically scrutinized.
Adsorption geometry and electronic structure of a charge-transfer-complex: TTF-PYZ2 on Ag(110)
Patrick Kretz, Kay Waltar, Yan Geng, Christian Metzger, Martin Graus, Achim Schöll, Friedrich Reinert, Shi-Xia Liu, Silvio Decurtins, Matthias Hengsberger, Jürg Osterwalder, Luca Castiglioni, New J. Phys., 2021, 23(1), 013002/1-9. online versionPDF
Abstract:
Using a combination of angle-resolved photoemission and electron diffraction methods, supported by DFT-based simulations, the electronic properties and adsorption geometries of the molecular charge-transfer complex tetrathiafulvalene-dipyrazine on Ag(110) were studied. The molecules adsorb aligned with the Ag rows in the first layer, while they are slightly rotated in the second layer. Five electronic valence states have been unambiguously assigned owing to their distinctive photoemission patterns.
2020
Chemical control of photoinduced charge-transfer direction in a tetrathiafulvalene-fused dipyrrolylquinoxaline difluoroborate dyad
Ping Zhou, Ulrich Aschauer, Silvio Decurtins, Thomas Feurer, Robert Häner, Shi-Xia Liu, Chem. Commun., 2020, 56(87), 13421-13424. online versionPDF
Abstract:
The annulation of tetrathiafulvalene (TTF) to dipyrrolylquinoxaline difluoroborate (QB) leads to strong electronic interactions between TTF and QB. Distinct photoinduced charge flows within the dyad are regulated by external stimuli. TD-DFT calculations verify the experimental results.
Formation of Tetranuclear Nickel(II) Complexes with Schiff-Bases: Crystal Structures and Magnetic Properties
Zhonglu You, Yingying Luo, Susan Herringer, Yanmin Li, Silvio Decurtins, Karl W. Krämer, Shi-Xia Liu, Crystals, 2020, 10(7), 592/1-13. online versionPDF
Abstract:
Two tetranuclear Nickel(II) cubane-type structures were structurally and magnetically characterized. Dominant intra-cube ferromagnetic behavior is observed which fits well with the bond angle guideline.
Bottom-up Synthesis of Nitrogen-doped Porous Graphene Nanoribbons
Rémy Pawlak, Xunshan Liu, Silviya Ninova, Philipp d'Astolfo, Carl Drechsel, Sara Sangtarash, Robert Häner, Silvio Decurtins, Hatef Sadeghi, Colin J. Lambert, Ulrich Aschauer, Shi-Xia Liu, Ernst Meyer, J. Am. Chem. Soc., 2020, 142(29), 12568-12573. online versionPDF
Abstract:
Nitrogen-doped porous graphene nanoribbons (N-GNRs) were synthesized on Ag(111). A combination of scanning tunneling microscopy, atomic force microscopy, scanning tunneling spectroscopy and density functional theory has been applied for the characterization of the nanoribbon.
Gold-linked strings of donor-acceptor dyads: On-surface formation and mutual orientation
Abstract:
Strings of gold-organic oligomers of polar units have been formed by on-surface synthesis and investigated with non-contact atomic force microscopy. The mutual alignment of dipoles within the strings is analyzed. The fused tetrathiafulvalene-benzothiadiazole units have an intrinsic dipole moment of about 5 Debye.
Pathway selection as a tool for crystal defect engineering: A case study with a functional coordination polymer
Afshin Abrishamkar, Salvio Suárez-García, Semih Sevim, Alessandro Sorrenti, Ramon Pons, Shi-Xia Liu, Silvio Decurtins, Guillem Aromí, David Aguilà, Salvador Pané, Andrew J. deMello, Aurelian Rotaru, Daniel Ruiz-Molina, Josep Puigmartí-Luis, Applied Materials Today, 2020, 20, 100632. online versionPDF
Abstract:
We demonstrate how the properties of a spin-crossover complex, taken as a model system, can be modified employing bioinspired conditions such as controlled reaction-diffusion (RD) processes achieved inside a continuous flow microfluidic device.
Constructive Quantum Interference in Single-Molecule Benzodichalcogenophene Junctions
Masoud Baghernejad, Yang Yang, Oday A. Al-Owaedi, Yves Aeschi, Biao-Feng Zeng, Zahra Murtada Abd Dawood, Xiaohui Li, Junyang Liu, Jia Shi, Silvio Decurtins, Shi-Xia Liu, Wenjing Hong, Colin J. Lambert, Chem. Eur. J., 2020, 26(23), 5264-5269. online versionPDF
Abstract:
Here we examine the effect of heteroatom substitution into molecular cores of non-alternant hydrocarbons, containing odd-membered rings. The sensitivity or resilience of constructive quantum interference (CQI) is probed.
Sequential Bending and Twisting Around C-C Single Bonds by Mechanical Lifting of a Pre-Adsorbed Polymer
Rémy Pawlak, Guilherme de Vilhena, Philipp D'Astolfo, Xunshan Liu, Giacomo Prampolini, Tobias Meier, Thilo Glatzel, Justin A. Lemkul, Robert Häner, Silvio Decurtins, Alexis Baratoff, Rubén Pérez, Shi-Xia Liu, Ernst Meyer, Nano Lett., 2020, 20(1), 652-657. online versionPDF
Abstract:
We quantify down to the sub-molecular level the mechanical response within individual poly-pyrenylene chains upon their detachment from a gold surface with an atomic force microscope at 5 K. Computer simulations based on a dedicated force-field reproduce the experimental traces.
Aggregation of a Giant Bean-Like {Mn26Dy6} Heterometallic Oxo-Hydroxo-Carboxylate Nano-Sized Cluster from a Hexanuclear {Mn6} Precursor
Mariana Darii, Victor Ch. Kravtsov, Karl Krämer, Jürg Hauser, Silvio Decurtins, Shi-Xia Liu, Marco Affronte, Svetlana G. Baca, Cryst. Growth Des., 2020, 20(1), 33-38. online versionPDF
Abstract:
Starting from a well-known hexanuclear mixed-valent manganese cluster, we report a synthetic protocol for its extension towards very large 3d-4f clusters. One example comprises sixteen Mn(III), ten Mn(II) and six Dy(III) ions, thus leading to a plurality of intracluster magnetic exchange interactions.
On-surface Synthesis and Characterization of Triply-fused Porphyrin-graphene Nanoribbon Hybrids
Luis M. Mateo, Qiang Sun, Shi-Xia Liu, Jesse J. Bergkamp, Kristjan Eimre, Carlo A. Pignedoli, Pascal Ruffieux, Silvio Decurtins, Giovanni Bottari, Roman Fasel, Tomas Torres, Angew. Chem. Int. Ed., 2020, 59(3), 1334-1339 and 1355. online versionPDF
and
PDF (Inside Back Cover)
Abstract:
The covalent fusion of a graphene nanoribbon with porphyrins through on-surface synthetic protocol is reported. The atomically precise structure has been characterized by STM and nc-AFM. The electronic properties have been investigated by STS in combination with DFT calculations, which reveals a low electronic gap of 0.4 eV.
Abstract:
In this study, we report on the realization of a mechanically and electronically robust graphene-based molecular junction. Robustness is achieved by separating the requirements for mechanical and electronic stability at the molecular level. The molecular devices exhibit stable current-voltage (I-V) characteristics up to bias voltages of 2.0 V with reproducible transport features in the temperature range from 20 K to 300 K.
Dirac-cone induced gating enhancement in single-molecule field-effect transistors
Abstract:
Using graphene as electrodes provides an opportunity for fabricating stable single-molecule field-effect transistors (FETs) operating at room temperature. However, the role of the unique graphene band structure in charge transport of single-molecule devices is still not clear. Here we report the Dirac-cone induced electrostatic gating effects in single-molecule FETs with graphene electrodes and a solid-state local bottom gate.
Overcoming steric hindrance in aryl-aryl homocoupling via on-surface copolymerization
José I. Urgel, Marco Di Giovannantonio, Guido Gandus, Qiang Chen, Xunshan Liu, Hironobu Hayashi, Pascal Ruffieux, Silvio Decurtins, Akimitsu Narita, Daniele Passerone, Hiroko Yamada, Shi-Xia Liu, Klaus Müllen, Carlo A. Pignedoli, Roman Fasel, ChemPhysChem, 2019, 20(18), 2360-2366. online versionPDF
Abstract:
On-surface synthesis is a unique tool to grow low-dimensional carbon nanomaterials with precise structural control down to the atomic level. Here, we propose a copolymerization approach to overcome the limitations that prevent intermolecular homocoupling. We apply the strategy of using suitable linkers as additional reactants to the formation of fully conjugated polycyclic nanowires incorporating non-benzenoid rings.
Implementing Functionality in Molecular Self-Assembled Monolayers
Abstract:
The planar heterocyclic molecules 1,6,7,12-tetraazaperylene on an Ag(111) metal substrate show different charging characteristics depending on their local environment: next to vacancies in self-assembled islands, molecules can be charged by local electric fields, whereas their charge state is fixed otherwise. This enables the activation of selected molecules inside islands by vacancy creation from scanning-probe based manipulation.
Tunable Lifetimes of Intramolecular Charge-Separated States in Molecular Donor-Acceptor Dyads
Maryam Akbarimoosavi, Egmont Johann Rohwer, Ariana Rondi, Jihane Hankache, Yan Geng, Silvio Decurtins, Andreas Hauser, Shi-Xia Liu, Thomas Feurer, Andrea Cannizzo, J. Phys. Chem. C, 2019, 123(14), 8500-8511. online versionPDF
Abstract:
We report ultrafast transient UV-Vis absorption and electrochemical spectroscopies on the photoinduced charge separation dynamics in a recently synthesized family of metal-free donor-acceptor systems, where two redox-active molecules are fused into a compact and planar structure upon annulation of a tetrathiafulvalene and a benzothiadiazole as electron donor and acceptor, respectively.
A Spontaneous Condensation Sequence from a {Fe6Dy3} Wheel to a {Fe7Dy4} Globe
Olga Botezat, Jan van Leusen, Jürg Hauser, Silvio Decurtins, Shi-Xia Liu, Paul Kögerler, Svetlana G. Baca, Cryst. Growth Des., 2019, 19(4), 2097-2103. online versionPDF
Abstract:
The transition from a {Fe6Dy3} wheel cluster to a highly condensed {Fe7Dy4} globe-shaped cluster coincides with a shift of the onset of significant out-of-phase ac susceptibility components from 3.6 K up to 12 K.
Self-Assembled Molecular-Electronic Films Controlled by Room Temperature Quantum Interference
Marjan Famili, Chuancheng Jia, Xunshan Liu, Peiqi Wang, Iain M. Grace, Jian Guo, Yuan Liu, Ziying Feng, Yiliu Wang, Zipeng Zhao, Silvio Decurtins, Robert Häner, Yu Huang, Shi-Xia Liu, Colin J. Lambert, Xiangfeng Duan, Chem, 2019, 5(2), 474-484. online versionPDF
Abstract:
Here, we demonstrate unequivocal signatures of room-temperature quantum interference (QI) in vertical tunneling transistors, formed from self-assembled monolayers (SAMs), with stable room-temperature switching operations. As a result of constructive QI effects, the conductances of the junctions formed from anthanthrene-based molecules with two different connectivities differ by a factor of 34, which can further increase to 173 by controlling the molecule-electrode interface with different terminal groups.
Nanographene Favors Interactions with the Electron Acceptor Rather Than the Electron Donor in a Planar Fused Push-Pull Conjugate
Michel Volland, Ping Zhou, Leonie Wibmer, Robert Häner, Silvio Decurtins, Shi-Xia Liu, Dirk M. Guldi, Nanoscale, 2019, 11(3), 1437-1441. online versionPDF
Abstract:
A combination of a preexfoliated nanographene (NG) dispersion and fused electron donor-acceptor tetrathiafulvalene-perylenediimide (TTF-PDI) results in a noncovalent functionalization of NG. Within the in situ formed nanohybrid, the conjugate was found to couple electronically with NG preferentially through the electron accepting PDI rather than the electron donating TTF.
2018
Probing Lewis Acid-Base Interactions in Single-Molecule Junctions
Xunshan Liu, Xiaohui Li, Sara Sangtarash, Hatef Sadeghi, Silvio Decurtins, Robert Häner, Wenjing Hong, Colin J. Lambert, Shi-Xia Liu, Nanoscale, 2018, 10(38), 18131-18134. online versionPDF
Abstract:
Charge transport through an organoborane wire is regulated via Lewis acid-base interactions. It goes in line with a change from LUMO- to HOMO-dominated transport.
Microscopic Approach to the Problem of Cooperative Spin Crossover in Polynuclear Cluster Compounds: Application to Tetranuclear Iron(II) Square Complexes
Serghei Ostrovsky, Andrew Palii, Silvio Decurtins, Shi-Xia Liu, Sophia Klokishner, J. Phys. Chem. C, 2018, 122(38), 22150-22159. online versionPDF
Abstract:
A new microscopic approach to the problem of cooperative spin crossover in molecular crystals containing polynuclear complexes as structural units has been developed. The developed general approach is adapted to the case of tetranuclear square complexes.
Versatility of copper(II) coordination compounds with 2,3-bis(2-pyridyl)pyrazine mediated by temperature, solvents and anions choice
Elena Melnic, Victor Ch. Kravtsov, Karl Krämer, Jan van Leusen, Silvio Decurtins, Shi-Xia Liu, Paul Kögerler, Svetlana G. Baca, Solid State Sciences, 2018, 82, 1-12. online versionPDF
Abstract:
Eight coordination compounds based on the ligand 2,3-bis(2-pyridyl)pyrazine (dpp) were synthesized and characterized by single crystal X-ray structure determination. The influence of various synthetic parameters was studied. The magnetic exchange interaction through the bridging dpp ligand was determined.
An electron acceptor molecule in a nanomesh: F4TCNQ on h-BN/Rh(111)
Huanyao Cun, Ari P. Seitsonen, Silvan Roth, Silvio Decurtins, Shi-Xia Liu, Jürg Osterwalder, Thomas Greber, Surface Science, 2018, 678, 183-188. online versionPDF
Abstract:
Here we report the deposition of a strong electron acceptor F4TCNQ on a monolayer of hexagonal boron nitride, h-BN/Rh(111). The effect of electron transfer from the substrate to the molecule is studied.
On the Border between Low-Nuclearity and One-Dimensional Solids: A Unique Interplay of 1,2,4-Triazolyl-Based {CuII5(OH)2} Clusters and MoVI-Oxide Matrix
Andrey B. Lysenko, Oksana A. Bondar, Ganna A. Senchyk, Eduard B. Rusanov, Monika Srebro-Hooper, James Hooper, Krunoslav Prsa, Karl W. Krämer, Silvio Decurtins, Oliver Waldmann, Shi-Xia Liu, Inorg. Chem., 2018, 57(10), 6076-6083. online versionPDF
Abstract:
A linear-shaped pentanuclear CuII5 cluster is flanked by two polyoxometalate anions based on MoVI. A structural, magnetic and quantum-mechanical study is presented.
Dipole Moment and Polarizability of Tunable Intramolecular Charge Transfer States in Heterocyclic π-Conjugated Molecular Dyads Determined by Computational and Stark Spectroscopic Study
Egmont J. Rohwer, Maryam Akbarimoosavi, Steven E. Meckel, Xunshan Liu, Yan Geng, Latévi Max Lawson Daku, Andreas Hauser, Andrea Cannizzo, Silvio Decurtins, Robert J. Stanley, Shi-Xia Liu, Thomas Feurer, J. Phys. Chem. C, 2018, 122(17), 9346-9355. online versionPDF
Abstract:
Stark spectroscopy is performed to determine experimentally dipole- and polarizability change over transitions in the visible range from tetrathiafulvalene-benzothiadiazole donor-acceptor molecules. The results are compared to the results from TD-DFT calculations.
Excited Spin-State Trapping in Spin Crossover Complexes on Ferroelectric Substrates
Christian Wäckerlin, Fabio Donati, Aparajita Singha, Romana Baltic, Silvio Decurtins, Shi-Xia Liu, Stefano Rusponi, Jan Dreiser, J. Phys. Chem. C, 2018, 122(15), 8202-8208. online versionPDF
Abstract:
Thin films of Fe(II) spin crossover complexes deposited on differently poled ferroelectric [Pb(Mg1/3Nb2/3)O3]1-x[PbTiO3]x (x = 0.32) substrates were studied by X-ray absorption spectroscopy (XAS). In the soft X-ray induced excited spin-state trapping (SOXIESST) regime at 3 K large differences occur between the two ferroelectric polarizations.
Hexanuclear Fe(III) wheels functionalized by amino-acetonitrile derivatives
Victor Ch. Kravtsov, Iurii Malaestean, Eugenia P. Stingach, Gheorghe G. Duca, Fliur Z. Macaev, Jan van Leusen, Paul Kögerler, Jürg Hauser, Karl Krämer, Silvio Decurtins, Shi-Xia Liu, Ashta C. Ghosh, Yann Garcia, Svetlana G. Baca, Solid State Sciences, 2018, 78, 156-162. online versionPDF
Abstract:
Three new hexanuclear Fe(III) wheels based on amino-acetonitrile derivatives have been synthesized and characterized. Mößbauer and magnetic studies revealed antiferromagnetic interactions between metal centres.
Incorporation of Hexanuclear Mn(II,III) Carboxylate Clusters with a {Mn6O2} Core in Polymeric Structures
Mariana Darii, Irina G. Filippova, Jürg Hauser, Silvio Decurtins, Shi-Xia Liu, Victor Ch. Kravtsov, Svetlana G. Baca, Crystals, 2018, 8(2), 100/1-11. online versionPDF
Abstract:
A new series of hexanuclear mixed-valent carboxylate coordination clusters of the type [Mn6O2(O2CR)10L4] (R = CMe3; CHMe2) featuring a {MnII4MnIII2(μ4-O)2} core have been synthesized and characterized by single crystal X-ray diffraction.
Electrospray deposition of structurally complex molecules revealed by atomic force microscopy
Antoine Hinaut, Tobias Meier, Rémy Pawlak, Sara Feund, Res Jöhr, Shigeki Kawai, Thilo Glatzel, Silvio Decurtins, Klaus Müllen, Akimitsu Narita, Shi-Xia Liu, Ernst Meyer, Nanoscale, 2018, 10(3), 1337-1344. online versionPDF
Abstract:
Here, we prove by atomic force microscopy and scanning tunneling microscopy, the structural integrity of complex organic molecules deposited onto an Au(111) surface using electrospray ionisation deposition.
2017
Exploration of a Variety of Copper Molybdate Coordination Hybrids Based on a Flexible Bis(1,2,4-triazole) Ligand: A Look through the Composition-Space Diagram
Ganna A. Senchyk, Andrey B. Lysenko, Konstantin V. Domasevitch, Oliver Erhart, Stefan Henfling, Harald Krautscheid, Eduard B. Rusanov, Karl W. Krämer, Silvio Decurtins, Shi-Xia Liu, Inorg. Chem., 2017, 56(21), 12952-12966. online versionPDF
Abstract:
The coordination of the bis(1,2,4-triazoyl) ligand is probed with several Cu(I) and Cu(II) complexes, all in combination with Mo(VI) oxides. A detailed composition space analysis is presented.
Electric field control of the valence tautomeric transformation in cobalt complexes
Abstract:
The dynamic vibronic problem of the pseudo-Jahn-Teller effect is solved for a single valence tautomeric cobalt complex placed in a dc electric field. It is demonstrated that the magnetic, spectroscopic and polarization characteristics of the complex can be effectively controlled by the aid of this field.
Stimuli-responsive NLO properties of tetrathiafulvalene-fused donor-acceptor chromophores
Elena Cariati, Xunshan Liu, Yan Geng, Alessandra Forni, Elena Lucenti, Stefania Righetto, Silvio Decurtins, Shi-Xia Liu, Phys. Chem. Chem. Phys., 2017, 19(33), 22573-22579. online versionPDF
Abstract:
The second-order nonlinear optical (NLO) properties of two tetrathiafulvalene-fused electron donor-acceptor dyads have been determined by Electric Field Induced Second Harmonic generation (EFISH) technique and were theoretically rationalized.
Donor-Acceptor Properties of a Single-Molecule Altered by On-Surface Complex Formation
Abstract:
A single fused tetrathiafulvalene-dipyridophenazine molecule adsorbed on a thin NaCl film on Cu(111) is investigated by atomic force microscopy and scanning tunneling microscopy. Free and bound states are observed and the chelation effect of Na+ ions is studied.
Crystallization of a Two-Dimensional Hydrogen-Bonded Molecular Assembly: Evolution of the Local Structure Resolved by Atomic Force Microscopy
Abstract:
Surface-assisted self-assembly structures of hexaazatriphenylene were determined with sub-Å resolution by means of nc-AFM, both in amorphous and crystalline phases.
A terpy-functionalized benzodifuran-based fluorescent probe for in vitro monitoring cellular Zn(II) uptake
Abstract:
An amphiphilic benzodifuran derivative as a fluorescent Zn(II) probe has been synthesized and tested for cytotoxicity and cellular uptake behavior in human cancer derived HeLa cells. A high cell membrane permeability was found.
Thermally induced anchoring of a zinc-carboxyphenylporphyrin on rutile TiO2 (110)
Res Jöhr, Antoine Hinaut, Rémy Pawlak, Lukasz Zajac, Piotr Olszowski, Bartosz Such, Thilo Glatzel, Jun Zhang, Matthias Muntwiler, Jesse J. Bergkamp, Luis-Manuel Mateo, Silvio Decurtins, Shi-Xia Liu, Ernst Meyer, J. Chem. Phys., 2017, 146(18), 184704/1-6. online versionPDF
Abstract:
The anchoring of a zinc-porphyrin equipped with carboxylic acid groups on rutile TiO2 (110) is analyzed using scanning probe microscopy and photoelectron spectroscopy.
Long-range ferrimagnetic order in a two-dimensional supramolecular Kondo lattice
Jan Girovsky, Jan Nowakowski, Md Ehesan Ali, Miloš Baljozović, Harald R. Rossmann, Thomas Nijs, Elise A. Aeby, Sylwia Nowakowska, Dorota Siewert, Gitika Srivastava, Christian Wäckerlin, Jan Dreiser, Silvio Decurtins, Shi-Xia Liu, Peter M. Oppeneer, Thomas A. Jung, Nirmalya Ballav, Nature Commun., 2017, 8, 15388/1-8. online versionPDF media release issued by the University of Bern
Abstract:
We demonstrate the direct observation of long-range ferrimagnetic order emerging in a two-dimensional supramolecular Kondo lattice. The lattice consists of paramagnetic hexadeca-fluorinated iron phthalocyanine and manganese phthalocyanine co-assembled into a chessboard pattern on single-crystalline Au(111) substrates. These findings suggest the use of molecular frameworks to engineer low-dimensional magnetically ordered materials.
Coordination behaviour of 1-(3,2':6',3''-terpyridin-4'-yl)ferrocene: structure and magnetic and electrochemical properties of a tetracopper dimetallomacrocycle
Y. Maximilian Klein, Angelo Lanzilotto, Alessandro Prescimone, Karl W. Krämer, Silvio Decurtins, Shi-Xia Liu, Edwin C. Constable, Catherine E. Housecroft, Polyhedron, 2017, 129, 71-76. online versionPDF
Abstract:
The tetranuclear compound represents a pair of μ-Cl bridged Cu(II) dimers exhibiting a weak antiferromagnetic coupling via the bridging chloride ligands.
Dinuclear complexes formed by hydrogen bonds: synthesis, structure and magnetic and electrochemical properties
Matteo Granelli, Alan M. Downward, Robin Huber, Laure Guénée, Céline Besnard, Karl W. Krämer, Silvio Decurtins, Shi-Xia Liu, Laurence K. Thompson, Alan F. Williams, Chem. Eur. J., 2017, 23(29), 7104-7112. online versionPDF
Abstract:
A series of homo- and heterodinuclear complexes where the two metal centres are linked by hydrogen bonds is reported. The complexes were characterized by X-ray crystallography, magnetic measurements and electrochemical methods. Outer sphere electron transfer is facilitated by inner sphere proton transfer.
Forces from periodic charging of adsorbed molecules
Abstract:
Gating of molecular levels in the field of an oscillating tip of an atomic force microscope can enable a periodic charging of individual molecules. Associated force differences are analyzed in detail.
Tetranuclear {CoII2CoIII2}, Octanuclear {CoII4CoIII4}, and Hexanuclear {CoIII3DyIII3} Pivalate Clusters: Synthesis, Magnetic Characterization, and Theoretical Modeling
Ioana Radu, Victor Ch. Kravtsov, Serghei M. Ostrovsky, Oleg S. Reu, Karl Krämer, Silvio Decurtins, Shi-Xia Liu, Sophia I. Klokishner, Svetlana G. Baca, Inorg. Chem., 2017, 56(5), 2662-2676. online versionPDF
Abstract:
New tetranuclear and octanuclear mixed-valent cobalt(II/III) pivalate clusters, and a hexanuclear {CoIII3DyIII3} pivalate cluster have been prepared and characterized by single crystal X-ray measurements. Their magnetic properties together with theoretical modeling were studied.
2016
Electric-Field Control of Magnetic and Polarizability Properties of Cyanide-Bridged Fe-Co Clusters
Abstract:
We present a new microscopic approach for the description of the effects of an external direct current (dc) electric field on the magnetic, polarizability, and spectroscopic characteristics of molecular crystals containing cyanide-bridged Fe-Co clusters as structural units.
Six Flexible and Rigid Co(II) Coordination Networks with Dicarboxylate and Nicotinamide-Like Ligands: Impact of Non-Covalent Interactions in Retention of Dimethylformamide Solvent
Diana Chisca, Lilia Croitor, Eduard B. Coropceanu, Oleg Petuhov, Galina Volodina, Svetlana G. Baca, Karl W. Krämer, Silvio Decurtins, Jürg Hauser, Shi-Xia Liu, Marina S. Fonari, Cryst. Growth Des., 2016, 16(12), 7011-7024. online versionPDF
Abstract:
1D and 2D Co(II) coordination networks with dicarboxylate and nicotinamide-like ligands reveal different modes of dmf retention in the crystal lattices.
Low-Dimensional Tin(II) Iodide Perovskite Structures Templated by an Aromatic Heterocyclic Cation
Abstract:
Single-crystal X-ray diffraction demonstrates that the sterically demanding 5,6-dicarboxybenzimidazolium cation is able to template and support a two-dimensional (2D) perovskite structure based on [SnI4]n2n- layers. The latter are formed by corner-sharing SnI6 octahedra. The cation also permits the formation of [SnI5]n3n- chains composed of corner-sharing SnI6 octahedra, leading to the crystallization of a stable one-dimensional (1D) perovskite compound.
Thermal and Near-Infrared Light Induced Spin Crossover in a Mononuclear Iron(II) Complex with a Tetrathiafulvalene-Fused Dipyridophenazine Ligand
Fabrice Pointillart, Xunshan Liu, Mikael Kepenekian, Boris Le Guennic, Stephane Golhen, Vincent Dorcet, Thierry Roisnel, Oliver Cador, Zhonglu You, Jürg Hauser, Silvio Decurtins, Lahcène Ouahab, Shi-Xia Liu, Dalton Trans., 2016, 45(28), 11267-11271. online versionPDF
Abstract:
A mononuclear Fe(II) complex (1) involving a tetrathiafulvalene-based ligand exhibits thermal spin-crossover (around 143 K) with pronounced hysteresis behaviour (48 K). The chromophoric and π-extended ligand allows a Near-Infrared (NIR) sensitization (780 nm) for the light-induced excited spin-state trapping (LIESST) with T(LIESST) = 90 K.
Diversity of Spin Crossover Transitions in Binuclear Compounds: Simulation by Microscopic Vibronic Approach
Andrew Palii, Serghei M. Ostrovsky, Oleg S. Reu, Boris Tsukerblat, Silvio Decurtins, Shi-Xia Liu, Sophia I. Klokishner, J. Phys. Chem. C, 2016, 120(26), 14444-14453. online versionPDF
Abstract:
A new microscopic approach to the problem of cooperative spin crossover in molecular crystals containing binuclear complexes as structural units has been developed. The cooperative interaction arising from the coupling of the molecular mode to the acoustic phonons represents the cornerstone of the approach.
Morphology Change of C60 Islands on Organic Crystals Observed by Atomic Force Microscopy
Sara Freund, Antoine Hinaut, Rémy Pawlak, Shi-Xia Liu, Silvio Decurtins, Ernst Meyer, Thilo Glatzel, ACS Nano, 2016, 10(6), 5782-5788. online versionPDF
Abstract:
The deposition of C60 molecules on an organic layer compound was investigated by means of non-contact atomic force microscopy (nc-AFM). Three-dimensional molecular islands of C60 are formed on the substrate following a "Volmer-Weber" type of growth.
Control of Reactivity and Regioselectivity for On-Surface Dehydrogenative Aryl-Aryl Bond Formation
Nemanja Kocic, Xunshan Liu, Songjie Chen, Silvio Decurtins, Ondrej Krejci, Pavel Jelinek, Jascha Repp, Shi-Xia Liu, J. Am. Chem. Soc., 2016, 138(17), 5585-5593. online versionPDF
Abstract:
Based on a combined STM/AFM technique with full atomistic resolution, the on-surface formation of complex molecular architectures built up from a tetracyclic pyrazino[2,3-f][4,7]phenanthroline molecule has been investigated. Selective intermolecular aryl-aryl coupling via dehydrogenative C-H activation is demonstrated.
Synthesis, Characterization, and Modeling of Magnetic Properties of a Hexanuclear Amino Alcohol-Supported {CoII2CoIII2DyIII2} Pivalate Cluster
Ioana Radu, Victor Ch. Kravtsov, Karl Krämer, Silvio Decurtins, Shi-Xia Liu, Oleg S. Reu, Serghei M. Ostrovsky, Sophia I. Klokishner, Svetlana G. Baca, J. Phys. Chem. C, 2016, 120(13), 7435-7443. online versionPDF
Abstract:
A heterometallic hexanuclear mixed-valence Co-Dy cluster has been prepared and characterized. A theoretical model describes its magnetic properties over a large temperature range.
Synthesis, crystal structure, and properties of a μ3-oxo-trichromium(III) propionate cluster with pyrazole
Olga Botezat, Irina G. Filippova, Jürg Hauser, Karl Krämer, Silvio Decurtins, Shi-Xia Liu, Svetlana G. Baca, J. Coord. Chem., 2016, 69(1), 72-80. online versionPDF
Abstract:
A new μ3-oxo-trinuclear chromium(III) propionate cluster has been synthesized and characterized. Magnetic studies revealed antiferromagnetic exchange interactions and a S = 1/2 electronic ground state.
Composition Space Analysis in the Development of Copper Molybdate Hybrids Decorated by a Bifunctional Pyrazolyl/1,2,4-Triazole Ligand
Andrey B. Lysenko, Ganna A. Senchyk, Liliana V. Lukashuk, Konstantin V. Domasevitch, Marcel Handke, Jörg Lincke, Harald Krautscheid, Eduard B. Rusanov, Karl W. Krämer, Silvio Decurtins, Shi-Xia Liu, Inorg. Chem., 2016, 55(1), 239-250. online versionPDF
Abstract:
Multicomponent copper(II)-molybdate solids were investigated by a composition space approach.
From pink to blue and back to pink again: changing the Co(II) ligation in a two-dimensional coordination network upon desolvation
Diana Chisca, Lilia Croitor, Eduard B. Coropceanu, Oleg Petuhov, Svetlana G. Baca, Karl Krämer, Shi-Xia Liu, Silvio Decurtins, Hector J. Rivera-Jacquez, Artëm E. Masunov, Marina S. Fonari, CrystEngComm, 2016, 18(3), 384-389. online versionPDF
Abstract:
Heating a pink 2D Co(II) complex initiates a single-crystal to single-crystal (SC-SC) transition to a blue complex.
2015
Anthanthrene dye-sensitized solar cells: influence of the number of anchoring groups and substitution motif
Yan Geng, Chenyi Yi, Martin Peter Bircher, Silvio Decurtins, Michele Cascella, Michael Grätzel, Shi-Xia Liu, RSC Adv., 2015, 5(119), 98643-98652. online versionPDF
Abstract:
Four new dye molecules comprising an anthanthrene core with different substitution patterns were prepared. The photovoltaic properties were investigated.
Controlling Electrical Conductance through a π-Conjugated Cruciform Molecule by Selective Anchoring to Gold Electrodes
Cancan Huang, Songjie Chen, Kristian Baruël Ørnsø, David Reber, Masoud Baghernejad, Yongchun Fu, Thomas Wandlowski, Silvio Decurtins, Wenjing Hong, Kristian Sommer Thygesen, Shi-Xia Liu, Angew. Chem. Int. Ed., 2015, 54(48), 14304-14307. online versionPDF
Abstract:
We designed a new cruciform molecule and introduced a promising and operationally simple approach to tune the charge transport pathways.
Microscopic theory of cooperative spin crossover: Interaction of molecular modes with phonons
Andrew Palii, Serghei Ostrovsky, Oleg Reu, Boris Tsukerblat, Silvio Decurtins, Shi-Xia Liu, Sophia Klokishner, J. Chem. Phys., 2015, 143(8), 084502/1-12. online versionPDF
Abstract:
A new microscopic theoretical approach to the description of spin crossover in molecular crystals is presented.
Coordination-directed self-assembly of a simple benzothiadiazole-fused tetrathiafulvalene to low-bandgap metallogels
Anneliese M. Amacher, Josep Puigmartí-Luis, Yan Geng, Victor Lebedev, Vladimir Laukhin, Karl Krämer, Jürg Hauser, David B. Amabilino, Silvio Decurtins, Shi-Xia Liu, Chem. Commun., 2015, 51(81), 15063-15066. online versionPDF
and
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Abstract:
The coordination-driven gelation of a benzothiadiazole-fused tetrathiafulvalene (TTF) forming a stable metallogel is demonstrated.
Searching the hearts of graphene-like molecules for simplicity, sensitivity and logic
Sara Sangtarash, Cancan Huang, Hatef Sadeghi, Gleb Sorohhov, Juerg Hauser, Thomas Wandlowski, Wenjing Hong, Silvio Decurtins, Shi-Xia Liu, Colin J. Lambert, J. Am. Chem. Soc., 2015, 137(35), 11425-11431. online versionPDF
Abstract:
Quantum interference patterns in the hearts of polycyclic aromatic hydrocarbons (PAHs) have experimentally and theoretically been analyzed.
A hybrid electron donor comprising cyclopentadithiophene and dithiafulvenyl for dye-sensitized solar cells
Gleb Sorohhov, Chenyi Yi, Michael Grätzel, Silvio Decurtins, Shi-Xia Liu, Beilstein J. Org. Chem., 2015, 11, 1052-1059. online versionPDF
Abstract:
Two new photosensitizers featured with a cyanoacrylic acid electron acceptor (A) and a hybrid electron donor (D) of cyclopentadithiophene and dithiafulvenyl, either directly linked or separated by a phenyl ring, were synthesized and characterized.
Periodic Charging of Individual Molecules Coupled to the Motion of an AFM Tip
Nemanja Kocic, Peter Weiderer, Stephan Keller, Silvio Decurtins, Shi-Xia Liu, Jascha Repp, Nano Lett., 2015, 15(7), 4406-4411. online versionPDF
Abstract:
Individual molecules at the edges of self-assembled islands grown on Ag(111) can be deliberately switched in their charge state with the electric field from a vibrating scanning-probe tip. The integrated frequency shift yields the tip-sample force that is due to a single additional electron.
Zero-Field Splitting in {MnIII3(μ3-O)} Core Single-Molecule Magnets Investigated by Inelastic Neutron Scattering and High-Field Electron Paramagnetic Resonance Spectroscopy
Marc Sigrist, Philip L. W. Tregenna-Piggott, Kasper S. Pedersen, Mikkel A. Sørensen, Anne-Laure Barra, Jürg Hauser, Shi-Xia Liu, Silvio Decurtins, Hannu Mutka, Jesper Bendix, Eur. J. Inorg. Chem., 2015, (16), 2683-2689. online versionPDF
Abstract:
Highly resolved inelastic neutron scattering spectroscopy and high-field electron paramagnetic resonance spectroscopy yield a uniquely accurate picture of the ground-state energetics of trinuclear Mn(III)-oximate complexes and the single-molecule magnet behavior.
Luminescence and Single-Molecule Magnet Behavior in Lanthanide Complexes Involving a Tetrathiafulvalene-Fused Dipyridophenazine Ligand
Abstract:
Two series of mononuclear complexes were studied involving the TTF-fused dipyrido[3,2-a:2',3'-c]phenazine and DyIII or YbIII ion. Crystal field splitting and an ab initio constructed barrier of relaxation of magnetization provide insight into the single-molecule magnet behavior of both DyIII derivatives. Magneto-structural correlations are performed for the YbIII analogues.
Excited state interactions between the chiral Au38L24 cluster and covalently attached porphyrin
Abstract:
A protected S-acetylthio porphyrin was synthesized and attached to the Au38(2-phenylethanethiolate)24 cluster in a ligand exchange reaction. Quenching of the chromophores fluorescence is observed, which can be explained by energy transfer from the porphyrin to the gold-cluster.
Electronic transport in benzodifuran single-molecule transistors
Abstract:
Benzodifuran (BDF) single-molecule transistors have been fabricated in electromigration break junctions for electronic measurements. The inelastic electron tunneling spectrum validates that the BDF molecule is the pathway of charge transport.
A one-dimensional coordination polymer based on Cu3-oximato metallacrowns bridged by benzene-1,4-dicarboxylato ligands: structure and magnetic properties
Lilia Croitor, Eduard B. Coropceanu, Oleg Petuhov, Karl W. Krämer, Svetlana G. Baca, Shi-Xia Liu, Silvio Decurtins, Marina S. Fonari, Dalton Trans., 2015, 44(17), 7896-7902. online versionPDF
Abstract:
A one-dimensional linear coordination polymer composed of trinuclear Cu3 metallacrown cores is presented. Magnetic susceptibility measurements show strong antiferromagnetic interactions between Cu(II) centers within the trinuclear metallacrown core with J = -430 cm-1.
Magic Ratios for Connectivity-Driven Electrical Conductance of Graphene-Like Molecules
Yan Geng, Sara Sangtarash, Cancan Huang, Hatef Sadeghi, Yongchun Fu, Wenjing Hong,
Thomas Wandlowski, Silvio Decurtins, Colin J. Lambert, Shi-Xia Liu, J. Am. Chem. Soc., 2015, 137(13), 4469-4476. online versionPDF
Abstract:
Experiments using a mechanically-controlled break junction and calculations based on density functional theory demonstrate a new magic ratio rule (MRR), which captures the contribution of connectivity to the electrical conductance of functionalized graphene-like aromatic molecules.
One-Photon Near-Infrared Sensitization of Well-Defined Yb(III) Surface Complexes for NIR-to-NIR Single Nanoparticle Imaging
Giuseppe Lapadula, David Trummer, Matthew P. Conley, Martin Steinmann, Ying-Fen Ran, Sophie Brasselet, Yannick Guyot, Olivier Maury, Silvio Decurtins, Shi-Xia Liu, Christophe Copéret, Chem. Mater., 2015, 27(6), 2033-2039. online versionPDF
Graphical Abstract:
Silica nanoparticles were surface-doped with (TTF-dppz)Yb(III) as antenna ligands. These nanoparticles absorb and emit in the NIR making possible one-photon NIR-to-NIR emission optical microscopy imaging of single nanoparticles.
Exploring the Electronic Structure of an Organic Semiconductor Based on a Compactly Fused Electron Donor-Acceptor Molecule
Pere Alemany, Enric Canadell, Yan Geng, Jürg Hauser, Piero Macchi, Karl Krämer, Silvio Decurtins, Shi-Xia Liu, Chem. Phys. Chem., 2015, 16(7), 1361-1365. online versionPDF
Graphical Abstract:
The electronic structure of a Mott-type semiconductor, which as a novel aspect is based on a compactly fused electron donor-acceptor molecule, has been elucidated. The highly symmetric solid state material represents a one-dimensional electronic system revealing strong intrastack antiferromagnetic interactions.
Exploitation of desilylation chemistry in tailor-made functionalization on diverse surfaces
Abstract:
Interface engineering to attain a uniform and compact self-assembled monolayer (SAM) at atomically flat surfaces plays a crucial role in the bottom-up fabrication of organic molecular devices. Here, we present a promising and operationally simple approach to the formation of uniform SAMs not only at ultra-flat single crystal metal surfaces, M(111) (M = Au, Pt, Pd, Rh, Ir), but also at the highly oriented pyrolytic graphite surface via M-C and C-C covalent bonds, respectively, upon efficient in-situ cleavage of trimethylsilyl (TMS) end groups of the molecules. The obtained SAMs are ultrastable within a wide potential window. The carbon-surface bonding on various substrates is confirmed by shell-isolated nanoparticle-enhanced Raman spectroscopy. Application of this strategy in tuning surface wettability has also been demonstrated. The most valuable finding is that a combination of the desilylation with the click chemistry represents an efficient method for covalent and tailor-made functionalization of diverse surfaces.
Current advances in fused tetrathiafulvalene donor-acceptor systems
Abstract:
Electron donor (D) and acceptor (A) systems have been studied extensively. Among them, fused D-A systems have attracted much attention during the past decades. Herein, we will present the evolution of tetrathiafulvalene (TTF) fused D-A systems and their potential applications in areas such as solar cells, OFETs, molecular wires and optoelectronics just to name a few. The synthesis, electrochemical, photophysical and intrinsic properties of fused D-A systems will be described as well.
2014
Crystal structures of isotypic poly[bis(benzimidazolium) [tetra-μ-iodido-stannate(II)]] and poly[bis(5,6-difluorobenzimidazolium) [tetra-μ-iodido-stannate(II)]]
Iwan Zimmermann, Tony D. Keene, Jürg Hauser, Silvio Decurtins, Shi-Xia Liu, Acta Cryst. E, 2014, 70(10), 178-182. online versionPDF
Abstract:
The isostructural title compounds, {(C7H7N2)2[SnI4]}n, (1), and {(C7H5F2N2)2[SnI4]}n, (2), show a layered perovskite-type structure composed of anionic {[SnI4]2-}n sheets parallel to (100), which are decorated on both sides with templating benzimidazolium or 5,6-difluorobenzimidazolium cations, respectively. These planar organic heterocycles mainly form N-H···I hydrogen bonds to the terminal I atoms of the corner-sharing [SnI6] octahedra (point group symmetry 2) from the inorganic layer, but not to the bridging ones. This is in contrast to most of the reported structures of related compounds where ammonium cations are involved. Here hydrogen bonding to both types of iodine atoms and thereby a distortion of the inorganic layers to various extents is observed. For (1) and (2), all Sn-I-Sn angles are linear and no out-of-plane distortions of the inorganic layers occur, a fact of relevance in view of the material properties. The arrangement of the aromatic cations is mainly determined through the direction of the N-H···I hydrogen bonds. The coherence between organic bilayers along [100] is mainly achieved through van der Waals interactions.
Triazolyl-Based Copper-Molybdate Hybrids: From Composition Space Diagram to Magnetism and Catalytic Performance
Ganna A. Senchyk, Andrey B. Lysenko, Artem A. Babaryk, Eduard B. Rusanov, Harald Krautscheid, Patrícia Neves, Anabela A. Valente, Isabel S. Gonçalves, Karl W. Krämer, Shi-Xia Liu, Silvio Decurtins, Konstantin V. Domasevitch, Inorg. Chem., 2014, 53(19), 10112-10121. online versionPDF
Graphical Abstract:
The composition space diagram offers intriguing possibilities for the investigation of copper-molybdate hybrid solids. The multicomponent CuII/ MoVI-oxide / 1,3-bis(1,2,4-triazol-4-yl)adamantane system was thoroughly studied employing the concept and led to three layered copper-molybdate coordination solids. This allowed us to elucidate the relationship between initial reagent concentration/stoichiometry and the stability of the resultant structural motifs. The compounds show catalytic activity in the epoxidation of cis-cyclooctene and in the oxidation of benzyl alcohol with different oxidants.
HOMO Stabilisation in π-Extended Dibenzotetrathiafulvalene Derivatives for Their Application in Organic Field-Effect Transistors
Yan Geng, Raphael Pfattner, Antonio Campos, Wei Wang, Olivier Jeannin, Jürg Hauser, Joaquim Puigdollers, Stefan T. Bromley, Silvio Decurtins, Jaume Veciana, Concepció Rovira, Marta Mas-Torrent, Shi-Xia Liu, Chem. Eur. J., 2014, 20(50), 16672-16679. online versionPDF
Abstract:
Three new organic semiconductors, in which either two methoxy units are directly linked to a dibenzotetrathiafulvalene (DB-TTF) central core and a 2,1,3-chalcogendiazole is fused on the one side, or four methoxy groups are linked to the DB-TTF, have been synthesised as active materials for organic field-effect transistors (OFETs). Their electrochemical behaviour, electronic absorption and fluorescence emission as well as photoinduced intramolecular charge transfer were studied. The electron-withdrawing 2,1,3-chalcogendiazole unit significantly affects the electronic properties of these semiconductors, lowering both the HOMO and LUMO energy levels and hence increasing the stability of the semiconducting material. The solution-processed single-crystal transistors exhibit high performance with a hole mobility up to 0.04 cm2 V-1 s-1 as well as good ambient stability.
Interpenetrated (8,3)-c and (10,3)-b Metal-Organic Frameworks Based on {FeIII3} and {FeIII2CoII} Pivalate Spin Clusters
Olga Botezat, Jan van Leusen, Victor Ch. Kravtsov, Irina G. Filippova, Jürg Hauser, Manfred Speldrich, Raphaël P. Hermann, Karl W. Krämer, Shi-Xia Liu, Silvio Decurtins, Paul Kögerler, Svetlana G. Baca, Cryst. Growth Des., 2014, 14(9), 4721-4728. online versionPDF
Abstract:
Two new magnetic cluster-based 3D coordination polymers consisting of &my;3-oxo-centered cationic homometallic [FeIII3O(O2CCMe3)6]+ or neutral heterometallic [FeIII2CoIIO(O2CCMe3)6] coordination clusters bridged by different N,N'-donor ligands into three-dimensional networks of {[Fe3O(O2CCMe3)6(4,4'-bpy)1.5](OH)·0.75(CH2Cl2)·x(H2O)}n (1, x ≈ 8) and {[Fe2CoO(O2CCMe3)6(bpe)0.5(pyz)]}n (2) (where 4,4'-bpy = 4,4'-bipyridine; bpe = 1,2'-bis(4-pyridyl)ethylene; pyz = pyrazine) have been prepared under solvothermal conditions. Single-crystal X-ray diffraction studies reveal the existence of a 6-fold interpenetrated network with rare (8,3)-c (etc) topology for 1 and a 3-fold interpenetrated network with (10,3)-b (ths) topology for 2. The interpenetration effectively results in very low BET surface areas, and the compounds have to be regarded as nonporous. Magnetic studies of 1 and 2 point to both ferro- and antiferromagnetic intra- and intercluster exchange interactions between the isotropic FeIII and the strongly anisotropic CoII spin centers. 57Fe Mössbauer spectroscopy confirms the uniform ferric (+III) valence state in both 1 and 2, and low-temperature data for 1 point toward distinct hyperfine fields for the Fe sites.
A highly sensitive TTF-functionalised probe for the determination of physiological thiols and its application in tumor cells
Abstract:
A tetrathiafulvalene (TTF)-fused piazselenole as a novel redox-active probe for highly sensitive determination of physiological thiols by electrochemical detection has been synthesised and successfully tested in intracellular non-protein thiol detection, reaching a detection limit of 10-10 M.
The Metallofullerene Field-Induced Single-Ion Magnet HoSc2N@C80
Jan Dreiser, Rasmus Westerström, Yang Zhang, Alexey A. Popov, Lothar Dunsch, Karl Krämer, Shi-Xia Liu, Silvio Decurtins, Thomas Greber, Chem. Eur. J., 2014, 20(42), 13536-13540. online versionPDF
Abstract:
The low-temperature magnetic properties of the endohedral metallofullerene HoSc2N@C80 have been studied by superconducting quantum interference device (SQUID) magnetometry. Alternating current (ac) susceptibility measurements reveal that this molecule exhibits slow relaxation of magnetization in a small applied field with timescales in the order of milliseconds. The equilibrium magnetic properties of HoSc2N@C80 indicate strong magnetic anisotropy. The large differences in magnetization relaxation times between the present compound and the previously investigated DySc2N@C80 are discussed.
Regulating a Benzodifuran Single Molecule Redox Switch via Electrochemical Gating and Optimization of Molecule/Electrode Coupling
Zhihai Li, Hui Li, Songjie Chen, Toni Froehlich, Chenyi Yi, Christian Schönenberger, Michel Calame, Silvio Decurtins, Shi-Xia Liu, Eric Borguet, J. Am. Chem. Soc., 2014, 136(25), 8867-8870. online versionPDF
Abstract:
We report a novel strategy for the regulation of charge transport through single molecule junctions via the combination of external stimuli of electrode potential, internal modulation of molecular structures, and optimization of anchoring groups. We have designed redox-active benzodifuran (BDF) compounds as functional electronic units to fabricate metal-molecule-metal (m-M-m) junction devices by scanning tunneling microscopy (STM) and mechanically controllable break junctions (MCBJ). The conductance of thiol-terminated BDF can be tuned by changing the electrode potentials showing clearly an off/on/off single molecule redox switching effect. To optimize the response, a BDF molecule tailored with carbodithioate (-CS2-) anchoring groups was synthesized. Our studies show that replacement of thiol by carbodithioate not only enhances the junction conductance but also substantially improves the switching effect by enhancing the on/off ratio from 2.5 to 8.
Electronic tuning effects via π-linkers in tetrathiafulvalene-based dyes
Yan Geng, Flavia Pop, Chenyi Yi, Narcis Avarvari, Michael Grätzel, Silvio Decurtins, Shi-Xia Liu, New J. Chem., 2014, 38(7), 3269-3274. online versionPDF
Abstract:
Four new tetrathiafulvalene (TTF)-based dyes featured with a donor-bridge-acceptor (D-π-A) structure were synthesized and characterized. All of them undergo two reversible oxidations to form stable radical cation and dication species. The electronic interactions between the TTF donor and the cyanoacrylic acid acceptor through the different π-linkers have been demonstrated by the presence of a photo-induced intramolecular charge-transfer (ICT) absorption band in the visible region. A red shift of the ICT state can be finely tuned by the degree of aromaticity and extended conjugation of π-bridges. To some extent, the oxidation potentials of these dyes are affected by the nature of π-bridges. They have been applied in organic dye-sensitized solar cells, showing relatively low power conversion efficiencies of up to 0.87% due to substantial charge recombination losses.
A quinoxaline-fused tetrathiafulvalene-based sensitizer for efficient dye-sensitized solar cells
Anneliese Amacher, Chenyi Yi, Jiabao Yang, Martin Peter Bircher, Yongchun Fu, Michele Cascella, Michael Grätzel, Silvio Decurtins, Shi-Xia Liu, Chem. Commun., 2014, 50(49), 6540-6542. online versionPDF
Abstract:
A new quinoxaline-fused tetrathiafulvalene-based sensitizer has been prepared and characterized. The resulting power conversion efficiency of 6.47% represents the best performance to date for tetrathiafulvalene-sensitized solar cells.
Contrast formation in Kelvin probe force microscopy of single π-conjugated molecules
Bruno Schuler, Shi-Xia Liu, Yan Geng, Silvio Decurtins, Gerhard Meyer, Leo Gross, Nano Lett., 2014, 14(6), 3342-3346. online versionPDF
Abstract:
We report the contrast formation in the local contact potential difference (LCPD) measured by Kelvin probe force microscopy (KPFM) on single charge-transfer complexes (CTCs) on a NaCl bilayer on Cu(111). At different tip heights, we found quantitatively different LCPD contrasts that characterize different properties of the molecule. In the small distance regime, the tip penetrates the electron density of the molecule, and the contrast is related to the size and topography of the electron shell of the molecule. For larger distances, the LCPD contrast corresponds to the electrostatic field above the molecule. However, in the medium-distance regime, that is, for tip heights similar to the size of the molecule, the nonspherical distribution of π- and σ-electrons often conceals the effect of the partial charges within the molecule. Only for large distances does the LCPD map converge toward the simple field of a dipole for a polar molecule.
Variable-pressure luminescence and Raman spectroscopy of molecular transition metal complexes: spectroscopic effects originating from small, reversible structural variations
Christian Reber, Camille Sonneville, Stéphanie Poirier, Nicolas Bélanger-Desmarais, William B. Connick, Sayandev Chatterjee, Patrick Franz, Silvio Decurtins, Spectrosc. Prop. Inorg. Organomet. Compd., 2014, 45, 260-273. online versionPDF
Abstract:
The past ten years have seen a significantly increasing number of published crystal structures for molecular transition metal complexes at variable pressure, providing quantitative information on structural variations.
Spectroscopic measurements at variable pressure have been reported over the past 60 years for a variety of complexes, but luminescence measurements were mostly limited to intense signals until early in this century.
The combination of variable-pressure structure variations with spectroscopic trends can lead to detailed new insight on a variety of aspects of electronic structure.
This approach holds promise for the in-depth study of many categories of functional materials.
Mixed-ligand hydroxocopper(II)/pyridazine clusters embedded into 3D framework lattices
Anna S. Degtyarenko, Marcel Handke, Karl W. Krämer, Shi-Xia Liu, Silvio Decurtins, Eduard B. Rusanov, Laurence K. Thompson, Harald Krautscheid, Konstantin V. Domasevitch, Dalton Trans., 2014, 43(22), 8530-8542. online versionPDF
Graphical Abstract:
Three types of polynuclear Cu(II) clusters rely on the compatibility of short-distance hydroxo-, carboxylato
and pyridazine bridges and are applicable for the construction of 3D MOF structures.
A Compact Tetrathiafulvalene-Benzothiadiazole Dyad and its Highly Symmetrical
Charge-Transfer Salt: Ordered Donor π-Stacks Closely Bound to Their Acceptors
Yan Geng, Raphael Pfattner, Antonio Campos, Jürg Hauser, Vladimir Laukhin, Joaquim Puigdollers, Jaume Veciana, Marta Mas-Torrent, Concepció Rovira, Silvio Decurtins, Shi-Xia Liu, Chem. Eur. J., 2014, 20(23), 7136-7143. online versionPDF
Graphical Abstract:
Compact donor-acceptor dyad: A compact and planar donor-acceptor molecule 1 comprising
Compact donor-acceptor dyad: A compact and planar donor-acceptor molecule 1 comprising
tetrathiafulvalene (TTF) and benzothiadiazole (BTD) units has been
prepared for investigation of its photoinduced intramolecular charge-transfer
process. Chemical oxidation of 1 affords a partially oxidised
crystalline charge-transfer (CT) salt {(1)2I3},
and eventually also a fully oxidised compound {1I3}·1/2I2.
The former CT salt exhibits a highly symmetrical crystal structure,
forming a wire of TTF+0.5 π-stacks
with compactly bonded BTD acceptors along its ridge (see graphic). This
unique structural feature accounts for its good electrical conductivity
of 2 S cm-1 at room temperature.
A Cruciform Electron Donor-Acceptor Semiconductor with Solid-State Red Emission: 1D/2D Optical Waveguides and Highly Sensitive/Selective Detection of H2S Gas
Abstract:
In this paper, a new cruciform donor-acceptor molecule
2,2'-((5,5'-(3,7-dicyano-2,6-bis(dihexylamino)benzo[1,2-b:4,5-b']difuran-4,8-diyl)bis(thiophene-5,2-diyl))bis(methanylylidene))dimalononitrile (BDFTM)
is reported. The compound exhibits both remarkable solid-state red emission and
p-type semiconducting behavior. The dual functions of BDFTM
are ascribed to its unique crystal structure, in which there are no
intermolecular face-to-face π-π
interactions, but the molecules are associated
by intermolecular CN···π
and H-bonding interactions. Firstly, BDFTM
exhibits aggregation-induced emission; that is, in solution, it is almost
non-emissive but becomes significantly fluorescent after aggregation. The
emission quantum yield and average lifetime are measured to be 0.16 and
2.02 ns, respectively. Crystalline microrods and microplates of BDFTM
show typical optical waveguiding behaviors with a rather low optical loss
coefficient. Moreover, microplates of BDFTM
can function as planar optical microcavities which can confine the emitted
photons by the reflection at the crystal edges. Thin films show an air-stable p-type
semiconducting property with a hole mobility up to
0.0015 cm2V-1s-1.
Notably, an OFET with a thin film of BDFTM is successfully
utilized for highly sensitive and selective detection of H2S
gas (down to ppb levels).
Tetracarboxylate Ligands as New Chelates Supporting Copper(II) Paddlewheel-Like Structures
Antoine Gomila, Sylvain Duvala, Céline Besnard, Karl W. Krämer, Shi-Xia Liu, Silvio Decurtins, Alan F. Williams, Inorg. Chem., 2014, 53(5), 2683-2691. online versionPDF
Abstract:
Two new ligands, N,N,N’,N’-tetrakis(2-methylbenzoic acid)-1,4-diaminomethylbenzene,
5H4, and N,N,N’,N’-tetrakis(2-methylbenzoic acid)-4,4’-diaminomethyldiphenyl,
6H4, carrying four carboxylate groups suitable for bridging dinuclear
centres have been prepared and their paddlewheel complexes with copper(II) prepared. The
phenyl-bridged ligand 5H4 gives a cyclic octanuclear species
[(Cu2)4(5)4] while the diphenyl-bridged
ligand 6H4 gives a lantern-like tetranuclear species
[(Cu2)2(6)2]; both were characterised
by X-ray crystallography. If the amine functions of 5 are protonated, intramolecular hydrogen
bonds position the four carboxylates in such a way as to allow the formation of the unusual compound
[Cu4(5H2)2Cl]3+
in which a Cu4 square centred by a chloro ligand is sandwiched between two
(5H2)2- ligands. The magnetic properties of this compound have been studied and
show antiferromagnetic coupling between adjacent coppers (J = -33.7 cm-1).
Tunneling, remanence, and frustration in dysprosium-based endohedral single-molecule magnets
Rasmus Westerström, Jan Dreiser, Cinthia Piamonteze, Matthias Muntwiler, Stephen Weyeneth, Karl Krämer, Shi-Xia Liu, Silvio Decurtins, Alexey Popov, Shangfeng Yang, Lothar Dunsch, Thomas Greber, Phys. Rev. B, 2014, 89(6), 060406(R)/1-4. online versionPDF
Abstract:
Paramagnetic atoms inside nanometer sized fullerenes realize robust, and
chemically protected, spin systems. Changing the stoichiometry of the endohedral
clusters results in a variety of magnetic ground states, as it is demonstrated
for DynSc3-nN@C80 (n = 1,2,3).
All three exhibit distinct hysteresis and qualify as single-molecule magnets. In
zero field the magnetization of n = 1
decays via quantum tunneling, while ferromagnetic coupling of the individual
dysprosium moments results in remanence for
Dy2ScN@C80 and in a frustrated
ground state for n = 3.
The latter ground state turns out to be one of the simplest realizations of a
frustrated, ferromagnetically coupled, system.
A quinoxaline-fused tetrathiafulvalene derivative and its semiconducting charge-transfer salt: synthesis, crystal structures and physical properties
Yan Geng, Christoph Fiolka, Karl Krämer, Jürg Hauser, Vladimir Laukhin, Silvio Decurtins, Shi-Xia Liu, New J. Chem., 2014, 38(5), 2052-2057. online versionPDF
Abstract:
A quinoxaline-fused tetrathiafulvalene (TTF) derivative 1 has been
synthesized to form a compact and planar
π-conjugated donor-acceptor (D-π-A)
ensemble, and its single crystal structure has been determined by X-ray
diffraction. The inherent redox activity of 1 has been probed by cyclic
voltammetry, and UV-vis spectroscopy revealed the typical broad and intense
intramolecular charge-transfer (ICT) absorption occurring for such compactly
fused D-π-A
molecules. Reaction with iodine led to a 2:1 semiconducting charge-transfer salt
{(1)2I3}, whose single crystal
structure investigation, however, underlined the occurrence of a pronounced
charge localization in the organic lattice. Consequently, the electrical
conductivity of {(1)2I3},
measured with the four contact method on single crystals, gave only a limited
value of about 1 × 10-4 Ω-1 cm-1, and the
activation energy was determined to be on the order of 470 - 480 meV.
Electronic tuning effects via cyano substitution of a fused tetrathiafulvalene-benzothiadiazole dyad for ambipolar transport properties
Graphical Abstract:
Electronic tuning effects via cyano substitution of a fused tetrathiafulvalene-benzothiadiazole dyad, extending the optical absorption into the near-IR region and leading to ambipolar behaviour, are presented.
Large π-Conjugated Chromophores Derived from Tetrathiafulvalene
Hongpeng Jia, Jie Ding, Andreas Hauser, Silvio Decurtins, Shi-Xia Liu, Asian J. Org. Chem., 2014, 3(2), 198-202. online versionPDF
Graphical Abstract:
Make mine a large: The direct annulation of two dipyrido[3,2-a:2’,3’-c]phenazine
units to a tetrathiafulvalene core leads to a large π-conjugate as a bridging
ligand. Its coordination ability to transition-metal ions is exemplified by the
formation of a stable dinuclear Ru2+ complex. The electrochemical,
optical absorption, photoinduced intramolecular charge-transfer, and
fluorescence characteristics of the ligand and the complex are described.
The coordination chemistry of tartronic acid with copper: magnetic studies of a quasi-equilateral tricopper triangle
Gabriel Pascu, Claire Deville, Sarah E. Clifford, Laure Guenée, Céline Besnard, Karl W. Krämer, Shi-Xia Liu, Silvio Decurtins, Floriana Tuna, Eric J. L. McInnes, Richard E. P. Winpenny, Alan F. Williams, Dalton Trans., 2014, 43(2), 656-662. online versionPDF
Abstract:
The coordination chemistry of tartronic acid, 1, with copper(II) has been investigated. Structures of two complexes are reported containing respectively the complex [Cu(1-2H)2Cl]3- where 1 acts as a bidentate ligand through carboxylates, and [Cu3(1-3H)3]3- where the alcohol function is deprotonated to bridge two coppers in a triangular trinuclear complex. The latter species undergoes facile oxidation leading to carbon-carbon bond formation. The magnetic and EPR properties of the trinuclear complex have been studied in detail.
2013
Directed Metalation Cascade To Access Highly Functionalized Thieno[2,3-f]benzofuran and Exploration as Building Blocks for Organic Electronics
Abstract:
A tandem directed metalation has been successfully applied to the preparation of
thieno[2,3-f]benzofuran-4,8-dione, providing an efficient and facile
approach to symmetrically and unsymmetrically functionalize the thieno[2,3-f]benzofuran
core at the 2,6 positions as well as to introduce the electron-withdrawing or
-donating groups (EWG or EDG) at its 4,8 positions. The presence of various
functional groups makes late-stage derivatization attainable.
Benzo[1,2-b:4,5-b']difuran-based sensitizers for dye-sensitized solar cells
Abstract:
Two BDF-based organic sensitizers, as first examples for
their use in dye-sensitized solar cells, are prepared and
characterized. They yield promising power conversion
efficiencies of up to 5.5% and high open circuit voltages up to
0.82 V. This work demonstrates that the BDF chromophore
acts as an effective donor in organic sensitizers.
A Benzaldehyde Derivative as a Chelating Ligand: Helical Manganese(II) Coordination Polymers Assembling into a Porous Solid
Galina Dulcevscaia, Shi-Xia Liu, Jürg Hauser, Karl W. Krämer, Gabriela Frei, Andreas Möller, Silvio Decurtins, Cryst. Growth Des., 2013, 13(9), 4138–4144. online versionPDF
and
PDF (Cover)
About the Cover:
A fascinating porous crystalline material is constructed from helical Mn(II) coordination polymers, whereby adjacent metal centers represented by MnO6 octahedrons are alternatingly edge-shared or corner-shared.
Unprecedented Trapping of Difluorooctamolybdate Anions within an α-Polonium Type Coordination Network
Olena V. Sharga, Andrey B. Lysenko, Marcel Handke, Harald Krautscheid, Eduard B. Rusanov, Alexander N. Chernega, Karl W. Krämer, Shi-Xia Liu, Silvio Decurtins, Adam Bridgeman, Konstantin V. Domasevitch, Inorg. Chem., 2013, 52(15), 8784-8794. online versionPDF
Abstract:
New fluorinated hybrid solids [Mo2F2O5(tr2pr)]
(1), [Co3(tr2pr)2(MoO4)2F2]·7H2O
(2), and [Co3(H2O)2(tr2pr)3(Mo8O26F2)]·3H2O
(3) (tr2pr = 1,3-bis(1,2,4-triazol-4-yl)propane) were prepared
from the reaction systems consisting of Co(OAc)2/CoF2 and
MoO3/(NH4)6Mo7O24, as CoII
and MoVI sources, in water (2) or in aqueous HF (1,
3) employing mild hydrothermal conditions. The tr2pr ligand
serves as a conformationally flexible tetradentate donor. In complex 1,
the octahedrally coordinated Mo atoms are linked in the discrete corner-sharing
{Mo2(μ2-O)F2O4N4} unit in
which a pair of tr-heterocycles (tr = 1,2,4-triazole) is arranged in
cis-positions opposite to "molybdenyl" oxygen atoms. The anti–anti
conformation type of tr2pr facilitates the tight zigzag chain packing
motif. The crystal structure of the mixed-anion complex salt 2 consists
of trinuclear [Co3(μ3-MoO4)2(μ2-F)2]
units self-assembling in CoII-undulating chains (Co···Co 3.0709(15)
and 3.3596(7) Å), which are cross-linked by tr2pr in layers. In 3,
containing condensed oxyfluoromolybdate species, linear centrosymmetric [Co3(μ2-tr)6]6+
SBUs are organized at distances of 10.72-12.45 Å in an α-Po-like network using
bitopic tr-linkers. The octahedral {N6} and {N3O3}
environments of the central and peripheral cobalt atoms, respectively, are
filled by triazole N atoms, water molecules, and coordinating [Mo8O26F2]6–
anions. Acting as a tetradentate O-donor, each difluorooctamolybdate anion
anchors four [Co3(μ2-tr)6]6+ units
through their peripheral Co-sites, which consequently leads to a novel type of a
two-nodal 4,10-c net with the Schläfli symbol {32.43.5}{34.420.516.65}.
The 2D and 3D coordination networks of 2 and 3, respectively, are
characterized by significant overall antiferromagnetic exchange interactions (J/k)
between the CoII spin centers on the order of −8 and −4 K. The [Mo8O26F2]6–
anion is investigated in detail by quantum chemical calculations.
Probing Charge Transfer in Benzodifuran-C60 Dumbbell-Type Electron Donor-Acceptor Conjugates: Ground and Excited State Assays
Hui Li, Christina Schubert, Pavlo O. Dral, Rubén D. Costa, Andrea La Rosa, Jürg Thüring, Shi-Xia Liu, Chenyi Yi, Salvatore Filippone, Nazario Martín, Silvio Decurtins, Timothy Clark, Dirk M. Guldi, Chem. Phys. Chem., 2013, 14(13), 2870 and Chem. Phys. Chem., 2013, 14(13), 2910-2919. online versionPDF (Inside Cover) and online versionPDF
Graphical Abstract:
Dumbbell arrays: A benzodifuran (BDF) donor is for the first time fused to two C60
molecules by different linkers to form triads 1–3 (see figure).
Their redox behavior, absorption, fluorescence emission, and photoinduced
intramolecular charge-transfer events have been investigated experimentally and
theoretically. The lifetime of the resulting charge-separated state varies
distinctly with the polarity of the solvents and the distance between the BDF
and C60 units.
Photo-induced intramolecular charge transfer in an ambipolar field-effect transistor based on a π-conjugated donor–acceptor dyad
Raphael Pfattner, Egon Pavlica, Michael Jaggi, Shi-Xia Liu, Silvio Decurtins, Gvido Bratina, Jaume Veciana, Marta Mas-Torrent, Concepció Rovira, J. Mater. Chem. C, 2013, 1(25), 3985-3988. online versionPDF
Abstract:
A π-conjugated tetrathiafulvalene-fused
perylenediimide (TTF-PDI) molecular dyad is successfully used as
a solution-processed active material for light sensitive ambipolar
field-effect transistors with balanced hole and electron mobilities.
The photo-response of the TTF-PDI dyad resembles its absorption profile.
Wavelength-dependent photoconductivity measurements reveal an important
photo-response at an energy corresponding to a PDI-localized electronic
π-π* transition
and also a more moderate effect due to an intramolecular
charge transfer from the HOMO localized on the TTF unit to the LUMO
localized on the PDI moiety. This work clearly elucidates the interplay
between intra- and intermolecular electronic processes in organic devices.
Synthesis and Redox and Photophysical Properties of Benzodifuran–Spiropyran Ensembles
Hui Li, Jie Ding, Songjie Chen, Christoph Beyer, Shi-Xia Liu, Hans-Achim Wagenknecht, Andreas Hauser, Silvio Decurtins, Chem. Eur. J., 2013, 19(20), 6459-6466. online versionPDF
Abstract:
Two benzodifuran (BDF)-coupled spiropyran (SP) systems and their BDF reference compounds were
obtained in good yields through Huisgen–Meldal–Sharpless "click" chemistry
and then subjected to investigation of their electrochemical and photophysical
properties. In both SP and merocyanine (MC) forms of the coupled
molecules, the BDF-based emission is quenched to around 1% of the
quantum yield of emission from the BDF reference compounds. Based on
electrochemical data, this quenching is attributed to oxidative electron-transfer
quenching. Irradiation at 366 nm results in ring opening to the MC forms
of the BDF-coupled SP compounds and the SP reference compound with a
quantum efficiency of about 50%. The rate constants for the thermal ring closing
are approximately 3.4×10–3 s–1.
However, in the photostationary states the MC fractions of the coupled molecules
are substantially lower than that of the reference SP compound, attributed
to the observed acceleration of the ring-closing reaction upon irradiation.
As irradiation at 366 nm invariably also excites higher-energy transitions
of the BDF units in the coupled compounds, the ring-opening reaction
is accelerated relative to the SP reference, which results in lower MC fractions
in the photostationary state. Reversible photochromism of these BDF-coupled
SP compounds renders them promising in the field of molecular switches.
A Pt(II) complex with both a phenanthroline and a tetrathiafulvalene-extended dithiolate ligand: Synthesis, crystal structure, electrochemical and spectroscopic properties
Chunyang Jia, Jie Ding, Shi-Xia Liu, Gaël Labat, Antonia Neels, Andreas Hauser, Silvio Decurtins, Polyhedron, 2013, 55, 87-91. online versionPDF
Abstract:
The reaction of
4,5-bis(2’-cyano-ethylsulfanyl)-4’,5’-dipropylthiotetrathiafulvalene
with [Pt(phen)Cl2] (phen = 1,10-phenanthroline) with
CsOH as base in CH3OH–THF affords the target complex
1 in 44% yield. This complex
crystallizes in the monoclinic space group P21/c,
M = 790.01, a = 12.1732(12), b =
15.851(2), c = 14.5371(16) Å, β = 107.693(12)˚, V
= 2672.4(5) Å3 and Z = 4. It undergoes two
reversible single-electron oxidation and two irreversible
reduction processes. An intense electronic absorption band at
15200 cm-1 (658 nm) in CH2Cl2
is assigned to the intramolecular mixed metal/ligand-to-ligand
charge transfer (LLCT) from a tetrathiafulvalene-extended
dithiolate-based HOMO to a phenanthroline-based LUMO. This band
shifts hypsochromically with increasing solvent polarity.
Systematic changes in the optical spectra upon oxidation allow
precise tuning of the oxidation states of
1 and reversible control over
its optical properties. Irradiation of
1 at 15625 cm-1 (640 nm) in glassy solution
below 150 K results in emission from the 3LLCT
excited state.
Two-Dimensional Supramolecular Electron Spin Arrays
Christian Wäckerlin, Jan Nowakowski, Shi-Xia Liu, Michael Jaggi, Dorota Siewert, Jan Girovsky, Aneliia Shchyrba, Tatjana Hählen, Armin Kleibert, Peter M. Oppeneer, Frithjof Nolting, Silvio Decurtins, Thomas A. Jung, Nirmalya Ballav, Adv. Mater., 2013, 25(17), 2403 and Adv. Mater., 2013, 25(17), 2404-2408. online versionPDF and online versionPDF
Abstract:
A bottom-up approach is introduced to fabricate two-dimensional self-assembled
layers of molecular spin-systems containing Mn and Fe ions arranged in a
chessboard lattice. We demonstrate that the Mn and Fe spin states can be
reversibly operated by their selective response to coordination/decoordination
of volatile ligands like ammonia (NH3).
Functionalized Adamantane Tectons Used in the Design of Mixed-Ligand Copper(II) 1,2,4-Triazolyl/Carboxylate Metal–Organic Frameworks
Ganna A. Senchyk, Andrey B. Lysenko, Harald Krautscheid, Eduard B. Rusanov, Alexander N. Chernega, Karl W. Krämer, Shi-Xia Liu, Silvio Decurtins, Konstantin V. Domasevitch, Inorg. Chem., 2013, 52(2), 863-872. online versionPDF
Abstract:
Bistriazoles, 1,3-bis(1,2,4-triazol-4-yl)propane (tr2pr)
and 1,3-bis(1,2,4-triazol-4-yl)adamantane (tr2ad),
were examined in combination with the rigid tetratopic
1,3,5,7-adamantanetetracarboxylic acid (H4-adtc)
platform for the construction of neutral heteroleptic copper(II) metal–organic
frameworks. Two coordination polymers, [{Cu4(OH)2(H2O)2}{Cu4(OH)2}(tr2pr)2(H-adtc)4]·2H2O
(1) and [Cu4(OH)2(tr2ad)2(H-adtc)2(H2O)2]·3H2O
(2), were synthesized and structurally characterized. In complexes 1
and 2, the N1,N2-1,2,4-triazolyl (tr)
and μ3-OH– groups serve as complementary bridges between
adjacent metal centers supporting the tetranuclear dihydroxo clusters. The
structure of 1 represents a unique association of two different kinds of
centrosymmetrical {Cu4(OH)2} units in a tight 3D framework,
while in compound 2, another configuration type of acentric tetranuclear
metal clusters is organized in a layered 3,6-hexagonal motif. In both cases, the
{Cu4(OH)2} secondary building block and trideprotonated
carboxylate H-adtc3– can be viewed as covalently bound
six- and three-connected nodes that define the net topology. The tr ligands,
showing μ3- or μ4-binding patterns, introduce additional
integrating links between the neighboring {Cu4(OH)2}
fragments. A variable-temperature magnetic susceptibility study of 2
demonstrates strong antiferromagnetic intracluster coupling (J1
= −109 cm–1 and J2 = −21 cm–1), which
combines for the bulk phase with a weak antiferromagnetic intercluster
interaction (zj = −2.5 cm–1).
Tetrathiafulvalene–Benzothiadiazoles as Redox-Tunable Donor–Acceptor Systems: Synthesis and Photophysical Study
Flavia Pop, Anneliese Amacher, Narcis Avarvari, Jie Ding, Latevi Max Lawson Daku, Andreas Hauser, Marius Koch, Jürg Hauser, Shi-Xia Liu, Silvio Decurtins, Chem. Eur. J., 2013, 19(7), 2504-2514. online versionPDF
Abstract:
Electrochemical and photophysical analysis of new donor–acceptor systems 2 and 3, in
which a benzothiadiazole (BTD) unit is covalently linked to a tetrathiafulvalene (TTF) core, have
verified that the lowest excited state can be ascribed to an intramolecular-charge-transfer (ICT)
π(TTF)→π*(benzothiadiazole)
transition. Owing to better overlap of the HOMO and LUMO in the fused
scaffold of compound 3, the intensity of the 1ICT band is substantially higher
compared to that in compound 2. The corresponding CT fluorescence is also observed in
both cases. The radical cation TTF+. is easily observed through chemical and electrochemical
oxidation by performing steady-state absorption experiments. Interestingly, compound 2 is
photo-oxidized under aerobic conditions.
A Donor–Acceptor Tetrathiafulvalene Ligand Complexed to Iron(II): Synthesis, Electrochemistry, and Spectroscopy of [Fe(phen)2(TTF-dppz)](PF6)2
Nathalie Dupont, Ying-Fen Ran, Shi-Xia Liu, Jakob Grilj, Eric Vauthey, Silvio Decurtins, Andreas Hauser, Inorg. Chem., 2013, 52(1), 306-312. online versionPDF
Abstract:
The synthesis and photophysical properties of the complex [Fe(phen)2(TTF-dppz)]2+
(TTF-dppz = 4′,5′-bis-(propylthio)tetrathiafulvenyl[i]dipyrido[3,2-a:2′,3′-c]phenazine,
phen = 1,10-phenanthroline) are described. In this complex, excitation into the
metal–ligand charge transfer bands results in the population of a high-spin
state of iron(II), with a decay lifetime of approximately 1.5 ns, in
dichloromethane, at room temperature. An intraligand charge transfer state can
also be obtained and has a lifetime of 38 ps. A mechanism for the different
states reached is proposed based on transient absorption spectroscopy.
New copper(II) complexes with isoconazole: Synthesis, structures and biological properties
Galina M. Dulcevscaia, Victor Ch. Kravtsov, Fliur Z. Macaev, Gheorghe G. Duca, Eugenia P. Stingachi, Serghei I. Pogrebnoi, Veaceslav V. Boldescu, Steliana F. Clapco, Janeta P. Tiurina, Alexandra A. Deseatnic-Ciloci, Janusz Lipkowski, Shi-Xia Liu, Silvio Decurtins, Svetlana G. Baca, Polyhedron, 2013, 52, 106-114. online versionPDF
Abstract:
There is an increasing demand for novel metal-based complexes with biologically relevant molecules in
technology and medicine. Three new Cu(II) coordination compounds
with antifungal agent isoconazole (L), namely mononuclear
complexes [CuCl2(L)2] (1), and [Cu(O2CMe)2(L)2]
· 2H2O (2) and coordination polymer [Cu(pht)(L)2]n
(3) (where H2pht - o-phthalic acid) were
synthesized and characterized by IR spectroscopy,
thermogravimetric analysis and X-ray crystallography. X-ray
analysis showed that in all complexes, the isoconazole is
coordinated to Cu(II) centres by a N atom of the imidazole
fragment. In complex 1, the square-planar environment of Cu(II)
atoms is completed by two N atoms of isoconazole and two
chloride ligands, whereas the Cu(II) atoms are coordinated by
two N atoms from two isoconazole ligands and two O atoms from
the different carboxylate residues: acetate in 2 and phthalate
in 3. The formation of an infinite chain through the bridging
phthalate ligand is observed in 3. The biosynthetic ability of
micromycetes Aspergillus niger CNMN FD 10 in the
presence of the prepared complexes 1-3 as well as the antifungal
drug isoconazole were studied. Complexes 2 and 3 accelerate the
biosynthesis of enzymes (β-glucosidase, xylanase and
endoglucanase) by this fungus. Moreover, a simplified and
improved method for the preparation of isoconazole nitrate was
developed.
2012
Trimethylsilyl-Terminated Oligo(phenylene ethynylene)s: An Approach to Single-Molecule Junctions with Covalent Au–C σ-Bonds
Abstract:
A new and efficient approach using cleaving of trimethylsilyl groups to create
covalent Au–C anchoring sites has been developed for single-molecule junction
conductance measurements. Employing the mechanically controllable break
junction (MCBJ) technique in liquid, we demonstrate the formation of highly
conducting single molecular junctions of several OPE-derivatives. The created
junctions are mechanically stable and exhibit conductances more than two
orders of magnitude higher than their dithiol analogues. Extended assembly
and reaction times lead to oligomerization. Combined STM-imaging and gap-mode
Raman experiments provide structure evidence to support the formation of
covalent Au–C contacts and further oligomerization.
A Spectroscopic and Computational Study of a Photoinduced Cross-Dehydrogenative Coupling Reaction of a Stable Semiquinone Radical
Abstract:
Norrish-type-II reaction on a semiquinone radical:
Stable semiquinone radicals serve as novel molecular platforms on
which a Norrish-type-II photoreaction can be initiated. A detailed
reaction scheme involving a 1,5-hydrogen transfer followed by a
cyclization step that finally leads to a new C—C bond formation
could be verified. Transient absorption spectroscopy and DFT
calculations trace convincingly the intermediates and transition
states along the reaction path (see scheme).
Phthalate-Based Coordination Polymers
Svetlana G. Baca, Silvio Decurtins,
in "Phthalates: Chemical Properties, Impacts on Health and the Environment", Gerardo L. Moretti and Drago Romano (Eds.);
Nova Publishers, Hauppauge, USA; ISBN: 978-1-62081-994-4; 2012, 1-59. online versionPDF
Abstract:
Coordination polymers represent an area of growing interest in chemistry and material sciences due their unique properties and potential applications in fields such as catalysis, gas storage and separation, magnetism, photonics, and drug delivery. ortho-Phthalic acid is a versatile dicarboxylic ligand which has been widely used in the design of numerous coordination polymers. This chapter covers the progress made by this ligand in the formation of such inorganic-organic hybrid materials.
Synthesis, Structure, and Properties of the New Mixed-Valent Dodecahalogenotrimetallate In4Ti3Br12 and its Relation to Compounds A3Ti2X9 (A = K, In; X = Cl, Br)
Melanie Schroeder, Sabina Hartwig, Karl W. Krämer, Silvio Decurtins, Harald Hillebrecht, Inorg. Chem., 2012, 51(15), 8385-8393. online versionPDF
Abstract:
Black single crystals of the new dodecahalogenotrimetallate In4Ti3Br12
were obtained by reacting InBr3 with Ti-wire at 450°C in a silica
tube sealed under vacuum. In4Ti3Br12 (Pearson
symbol hR57, space group R3m, Z = 3, a =
7.3992(8) Å, c = 36.673(6) Å, 643 refl., 25 param., R1(F)
= 0.025; wR2(F2) = 0.046) is a defect
variant of a 12 L-perovskite. In+ cations are 12-fold coordinated in
two different ways: In1 as an anticuboctahedron and In2 as a cuboctahedron. In
both cases the 5s2 configuration results in 3 short, 6 medium, and 3
long In–Br distances which might be explained as lone pair effect or second
order Jahn–Teller instability. Furthermore there are isolated linear trimers [Ti3Br12]4–
consisting of facesharing octahedra similar to [Ru3Cl12]4–.
The [Ti3Br12]4–-unit has to be described as a
mixed-valent d1-d2-d1 system. According to
magnetic measurements, the Ti-atoms in In4Ti3Br12
show strong antiferromagnetic interactions (Θ = −1216(6) K) which might be
addressed as weak Ti3+–Ti2+–Ti3+ bonds. For
comparison, single crystals of K3Ti2X9 (X
= Cl, Br) were synthesized and their structures refined. The rotation of the Ti2X93–
dimers reduced the symmetry of the well-known Cs3Cr2Cl9
type from P63/mmc to P63/m and
resulted in the formation of merohedral twins. According to the unit cell
volumes In+ is smaller than K+ in all cases.
Tetrathiafulvalene-Fused Porphyrins via Quinoxaline Linkers: Symmetric and Asymmetric Donor–Acceptor Systems
Hongpeng Jia, Belinda Schmid, Shi-Xia Liu, Michael Jaggi, Philippe Monbaron, Sheshanath V. Bhosale, Shadi Rivadehi, Steven J. Langford, Lionel Sanguinet, Eric Levillain, Mohamed E. El-Khouly, Ysushi Morita, Shunichi Fukuzumi, Silvio Decurtins, Chem. Phys. Chem., 2012, 13(14), 3370-3382. online versionPDF
Abstract:
A tetrathiafulvalene (TTF) donor is annulated to porphyrins (P) via
quinoxaline linkers to form novel symmetric P–TTF–P triads 1 a–c
and asymmetric P–TTF dyads 2 a,b in good yields. These planar and
extended π-conjugated molecules absorb light over a wide region of the UV/Vis
spectrum as a result of additional charge-transfer excitations within the donor–acceptor
assemblies. Quantum-chemical calculations elucidate the nature of the
electronically excited states. The compounds are electrochemically amphoteric
and primarily exhibit low oxidation potentials. Cyclic voltammetric and
spectroelectrochemical studies allow differentiation between the TTF and
porphyrin sites with respect to the multiple redox processes occurring within
these molecular assemblies. Transient absorption measurements give insight into
the excited-state events and deliver corresponding kinetic data. Femtosecond
transient absorption spectra in benzonitrile may suggest the occurrence of fast
charge separation from TTF to porphyrin in dyads 2 a,b but not in
triads 1 a–c. Clear evidence for a photoinduced and relatively
long lived charge-separated state (385 ps lifetime) is obtained for a
supramolecular coordination compound built from the ZnP–TTF dyad and a
pyridine-functionalized C60 acceptor unit. This specific excited
state results in a (ZnP–TTF)·+···(C60py)·–
state. The binding constant of ZnII···py is evaluated by
constructing a Benesi–Hildebrand plot based on fluorescence data. This plot
yields a binding constant K of 7.20×104 M–1,
which is remarkably high for bonding of pyridine to ZnP.
Ying-Fen Ran, Martin Steinmann, Marc Sigrist, Shi-Xia Liu, Jürg Hauser, Silvio Decurtins, C. R. Chimie, 2012, 15(10), 838-844. online versionPDF
Abstract:
The explorative lanthanide coordination chemistry of
4′,5′-bis-(propylthio)tetrathiafulvenyl[i]dipyrido[3,2-a:2′,3′-c]phenazine
(TTF-dppz) is described. Thereby, four new Ln(III) complexes, [Ln(NO3)3(TTF-dppz)2]
with Ln(III) = Nd (1), Eu (2),
Gd (3), Tb (4),
have been prepared and characterized. An X-ray crystallographic study of [Gd(NO3)3(TTF-dppz)2]
(3) shows that the Gd(III) ion is coordinated
to six oxygen atoms from three bidentate nitrate ligands and four nitrogen atoms
from two bidentate TTF-dppz molecules forming a distorted bicapped square
antiprism coordination geometry. The UV-vis spectra of the four Ln(III)
complexes show very strong absorption bands in the UV region consistent with
ligand centred electronic π-π* transitions and an intense broad absorption band
in the visible region corresponding to a spin-allowed electronic π-π* 1ILCT
transition from the TTF-dppz ligand. Upon coordination, the 1ILCT
band of the free TTF-dppz ligand is bathochromically shifted. The
electrochemical studies reveal that all complexes undergo two reversible
oxidation and one (quasi)reversible reduction processes, ascribed to the
successive oxidations of the TTF moiety and the reduction of the dppz unit,
respectively. Moreover, the magnetic properties of complexes
3 and 4 are
discussed.
Cluster-Based Networks: 1D and 2D Coordination Polymers Based on {MnFe2(μ3-O)}-Type Clusters
Galina M. Dulcevscaia, Irina G. Filippova, Manfred Speldrich, Jan van Leusen, Victor Ch. Kravtsov, Svetlana G. Baca, Paul Kögerler, Shi-Xia Liu, Silvio Decurtins, Inorg. Chem., 2012, 51(9), 5110–5117. online versionPDF
Abstract:
A straightforward approach to heterometallic Mn–Fe cluster-based coordination
polymers is presented. By employing a mixed-valent μ3-oxo trinuclear
manganese(II/III) pivalate cluster, isolated as [MnIIMnIII2O(O2CCMe3)6(hmta)3]·(solvent)
(hmta = hexamethylenetetramine; solvent = n-propanol (1), toluene
(2)) in the reaction with a μ3-oxo trinuclear iron(III)
pivalate cluster compound, [Fe3O(O2CCMe3)6(H2O)3]O2CCMe3·2Me3CCO2H,
three new heterometallic {MnIIFeIII2}
cluster-based coordination polymers were obtained: the one-dimensional polymer
chain compounds {[MnFe2O(O2CCMe3)6(hmta)2]·0.5MeCN}n
(3) and {[MnFe2O(O2CCMe3)6(hmta)2]·Me3CCO2H·(n-hexane)}n
(4) and the two-dimensional layer compound {[MnFe2O(O2CCMe3)6(hmta)1.5]·(toluene)}n
(5). Single-crystal X-ray diffraction analysis reveals a μ3-oxo
trinuclear pivalate cluster building block as the main constituent in all
polymer compounds. Different M:hmta ratios in 1–5 are related to
the different structural functions of the N-containing ligand. In clusters 1
and 2, three hmta ligands are monodentate, whereas in chains 3 and
4 two hmta ligands act as bridging ligands and one is a monodentate
ligand; in 5, all hmta molecules act as bidentate bridges. Magnetic
studies indicate dominant antiferromagnetic interactions between the metal
centers in both homometallic {Mn3}-type clusters 1 and 2
and heterometallic {MnFe2}-type coordination polymers 3–5.
Modeling of the magnetic susceptibility data to a isotropic model Hamiltonian
yields least-squares fits for the following parameters: J1(MnII–MnIII)
= −6.6 cm–1 and J2(MnIII–MnIII)
= −5.4 cm–1 for 1; J1 = −5.5 cm–1
and J2(MnIII–MnIII) = −3.9 cm–1
for 2; J1(MnII–FeIII) = −17.1 cm–1
and J2(FeIII–FeIII) = −43.7 cm–1
for 3; J1 = −23.8 cm–1 and J2
= −53.4 cm–1 for 4; J1 = −13.3 cm–1
and J2 = −35.4 cm–1 for 5. Intercluster
coupling plays a significant role in all compounds 1–5.
[V16O38(CN)]9–: A Soluble Mixed-Valence Redox-Active Building Block with Strong Antiferromagnetic Coupling
Tony D. Keene, Deanna M. D’Alessandro, Karl W. Krämer, Jason R. Price, David J. Price, Silvio Decurtins, Cameron J. Kepert, Inorg. Chem., 2012, 51(17), 9192-9199. online versionPDF
Abstract:
A new discrete [V16O38(CN)]9– cluster, which
displays the hitherto unknown 8– charge on the cluster shell and is the first to
encapsulate the cyanide anion, has been synthesized and characterized by IR and
UV/vis/near-IR spectroscopy, electrochemistry, and magnetic susceptibility
measurements. Bond valence sum calculations conducted on the basis of the
crystal structure analysis of K9[V16O38(CN)]·13H2O
confirm that this new member of the polyoxovanadate series is a mixed-valence
complex. The intervalence charge transfer bands arising from intrametal
interactions reveal that a localized (class II) assignment is appropriate for
the cluster; however, a small degree of electronic delocalization is present.
Interesting possibilities exist for the incorporation of this unit into higher
dimensionality framework structures, where the redox, optical, and magnetic
properties can be exploited and tuned.
Benzodifuran-Containing Well-Defined π-Conjugated Polymers for Photovoltaic Cells
Hui Li, Peng Tang, Yan Zhao, Shi-Xia Liu, Yves Aeschi, Lijun Deng, Jörg Braun, Bin Zhao, Yunqi Liu, Songting Tan, Wolfgang Meier, Silvio Decurtins, J. Polym. Sci. A: Polym. Chem., 2012, 50(14), 2935-2943. online versionPDF
Abstract:
Two well-defined alternating π-conjugated polymers containing a soluble
electroactive benzo[1,2-b:4,5-b′]difuran (BDF) chromophore,
poly(BDF-(9-phenylcarbazole)) (PBDFC), and poly(BDF-benzothiadiazole) (PBDFBTD)
were synthesized via Sonogashira copolymerizations. Their optical,
electrochemical, and field-effect charge transport properties were characterized
and compared with those of the corresponding homopolymer PBDF and random
copolymers of the same overall composition. All these polymers cover broad
optical absorption ranges from 250 to 750 nm with narrow optical band gaps of
1.78–2.35 eV. Both PBDF and PBDFBTD show ambipolar redox properties with HOMO
levels of −5.38 and −5.09 eV, respectively. The field-effect mobility of holes
varies from 2.9 × 10−8 cm2 V−1 s−1
in PBDF to 1.0 × 10−5 cm2 V−1 s−1 in
PBDFBTD. Bulk heterojunction solar cell devices were fabricated using the
polymers as the electron donor and [6,6]-phenyl-C61-butyric acid
methyl ester as the electron acceptor, leading to power conversion efficiencies
of 0.24–0.57% under air mass 1.5 illumination (100 mW cm−2). These
results indicate that their band gaps, molecular electronic energy levels,
charge mobilities, and molecular weights are readily tuned by copolymerizing the
BDF core with different π-conjugated units.
Tetrathiafulvalene-annulated dipyrrolylquinoxaline: the effect of fluoride on its optical and electrochemical behaviors
Hong-Peng Jia, John C. Forgie, Shi-Xia Liu, Lionel Sanguinet, Eric Levillain, Franck Le Derf, Marc Sallé, Antonia Neels, Peter J. Skabara, Silvio Decurtins, Tetrahedron, 2012, 68(5), 1590-1594. online versionPDF
Abstract:
A tetrathiafulvalene donor has been annulated to 2,3-di(1H-2-pyrrolyl)quinoxaline
affording a new chemosensor 1, which shows a unique optical selectivity
and reactivity for the fluoride ion over other anions in CH2Cl2
leading to a colorimetric response. Electrochemical polymerization of 1
occurred in the presence of fluoride.
2011
2,3-Dichloro-1,4-hydroquinone 2,3-dichloro-1,4-benzoquinone monohydrate: a quinhydrone-type 1:1 donor-acceptor [D-A] charge-transfer complex
Abstract:
In the crystal structure of the title compound (systematic name:
2,3-dichlorobenzene-1,4-diol 2,3-dichlorocyclohexa-2,5-diene-1,4-dione
monohydrate), C6H4Cl2O2·C6H2Cl2O2·H2O,
the 2,3-dichloro-1,4-hydroquinone donor (D) and
the 2,3-dichloro-1,4-benzoquinone acceptor (A)
molecules form alternating stacks along [100]. Their molecular planes [maximum
deviations for non-H atoms: 0.0133 (14) (D) and
0.0763 (14) Å (A)] are inclined to one another by
1.45 (3)° and are thus almost parallel. There are
π-π
interactions involving the D and
A molecules, with centroid-centroid distances of 3.5043 (9) and
3.9548 (9) Å. Intermolecular O-H···O
hydrogen bonds involving the water molecule and the hydroxy and ketone groups
lead to the formation of two-dimensional networks lying parallel to (001). These
networks are linked by C-H···O
interactions, forming a three-dimensional structure.
Targeting π-Conjugated Multiple Donor-Acceptor Motifs Exemplified by Tetrathia-fulvalene (TTF)-Linked Quinoxalines and Tetrabenz[bc,ef,hi,uv]ovalenes: Synthesis, Spectroscopic, Electrochemical, and Theoretical Characterization
Hong-Peng Jia, Jie Ding, Ying-Fen Ran, Shi-Xia Liu, Carmen Blum, Irina Petkova, Andreas Hauser, Silvio Decurtins, Chem. Asian J., 2011, 6(12), 3312-3321. online versionPDF
Abstract:
An efficient synthetic approach to a symmetrically
functionalized tetrathiafulvalene (TTF) derivative
with two diamine moieties,
2-[5,6-diamino-4,7-bis(4-pentylphenoxy)-1,3-benzodithiol-2-ylidene]-4,7-bis(4-pentylphenoxy)-1,3-benzodithiole-5,6-diamine
(2), is reported. The subsequent Schiff-base
reactions of 2 afford large π-conjugated
multiple donor–acceptor (D–A) arrays, for example,
the triad
2-[4,9-bis(4-pentylphenoxy)-1,3-dithiolo[4,5-g]quinoxalin-2-ylidene]-4,9-bis(4-pentylphenoxy)-1,3-dithiolo[4,5-g]quinoxaline
(8) and the corresponding tetrabenz[bc,ef,hi,uv]ovalene-fused
pentad 1, in good yields and high purity. The
novel redox-active nanographene 1 is so far
the largest known TTF-functionalized polycyclic
aromatic hydrocarbon (PAH) with a well-resolved
1H NMR spectrum. The electrochemically highly
amphoteric pentad 1 and triad 8
exhibit various electronically excited
charge-transfer states in different oxidation states,
thus leading to intense optical intramolecular
charge-transfer (ICT) absorbances over a wide
spectral range. The chemical and electrochemical
oxidations of 1 result in an unprecedented
TTF·+ radical cation dimerization,
thereby leading to the formation of [1·+]2
at room temperature in solution due to the
stabilizing effect, which arises from strong
π–π
interactions. Moreover, ICT fluorescence is observed
with large solvent-dependent Stokes shifts and
quantum efficiencies of 0.05 for 1 and 0.035
for 8 in dichloromethane.
A tetrathiafulvalene-functionalized naphthalene diimide: synthesis, electrochemical and photophysical properties
Michael Jaggi, Belinda Schmid, Shi-Xia Liu, Sheshanath V. Bhosale, Shadi Rivadehi, Steven J. Langford, Silvio Decurtins, Tetrahedron, 2011, 67(38), 7231-7235. online versionPDF
Abstract:
A tetrathiafulvalene donor has been attached to the naphthalene
diimide core via a rigid bridge affording a new planar molecular
dyad. Its electronic properties have been studied experimentally
by the combination of electrochemistry and UV–vis-NIR spectroscopy.
Various electronic excited charge-transfer states are generated
in different oxidation states, leading to almost full absorption
in the visible to near-IR region with high extinction coefficients.
The observed electronic properties are explained on the basis of
density-functional-theory. In particular, the oxidized radical
species show a strong tendency to undergo aggregation, in which
the long-distance attractive interactions overcome the electrostatic
repulsions.
Two-Dimensional Manganese(II) Coordination Polymer Based on Phthalate and Pyrazine Bridges Exhibiting Antiferromagnetic Porperties
O. Gherco, T. D. Keene, I. G. Filippova, S. G. Baca, S. Decurtins, Moldavian Journal of the Physical Sciences, 2011, 10(1), 103-108. online versionPDF
Abstract:
Magnetic measurements for the 2D coordination polymer
[Mn(Pht(Pyz(H2O)2]n
(1), in which metal centres are linked together
by pyrazine (Pyz) and 1,6-bridging o-phthalate
ligand (Pht2-), revealed
antiferromagnetic interactions between Mn(II) ions.
Synthesis, Structures, Redox and Photophysical Properties of Benzodifuran-functionalised Pyrene and Anthracene Fluorophores
Stephan Keller, Chenyi Yi, Chen Li, Shi-Xia Liu, Carmen Blum, Gabriela Frei, Olha Sereda, Antonia Neels, Thomas Wandlowski, Silvio Decurtins, Org. Biomol. Chem., 2011, 9(18), 6410-6416. online versionPDF
Abstract:
Benzodifuran-functionalised pyrene and
anthracene fluorophores 1 and 2 were obtained
in reasonable yields. Their single crystal structures, electrochemical, optical
absorption, and fluorescence characteristics have been described. They show
strong luminescence with high quantum yields of 0.53 for 1 and
0.48 for 2.
Exploratory studies on coordination chemistry of a redox-active bridging ligand: synthesis, properties and solid state structures of the complexes
Abstract:
The explorative coordination chemistry of the
bridging ligand TTF-PPB is presented. Its strong binding ability to Co(II)
and then to Ni(II) or Cu(II) in the presence of
hexafluoroacetylacetonate (hfac-), forming new mono-
and dinuclear complexes 1–3, is described. X-ray crystallographic studies have
been conducted in the case of the free ligand TTF-PPB as well as its complexes [Co(TTF-PPB)(hfac)2]
(1) and [Co(hfac)2(μ-TTF-PPB)Ni(hfac)2]
(2). Each metal ion is bonded to two bidentate hfac-
anions through their oxygen atoms and two nitrogen atoms of the PPB moiety with
a distorted octahedral coordination geometry. Specifically, nitrogen donor atoms
of TTF-PPB adopt a cis-coordination but not in the equatorial plane,
which is quite rare. Electronic absorption, photoinduced intraligand charge
transfer (1ILCT), and electrochemical behaviour of 1–3
have been investigated. UV-Vis spectroscopy shows very strong bands in the UV
region consistent with ligand centred
π–π* transitions
and an intense broad band
in the visible region corresponding to a spin-allowed
π–π* 1ILCT
transition. Upon coordination, the 1ILCT band is
bathochromically shifted by 3100, 6100 and 5900 cm-1
on going from 1 to 3. The electrochemical studies reveal that all of them
undergo two reversible oxidation and one reversible reduction processes,
ascribed to the successive oxidations of the TTF moiety and the reduction of the
PPB unit, respectively.
Annulation of Tetrathiafulvalene to the Bay Region of Perylenediimide: Fast Electron-Transfer Processes in Polar and Nonpolar Solvents
Mohamed E. El-Khouly, Michael Jaggi, Belinda Schmid, Carmen Blum, Shi-Xia Liu, Silvio Decurtins, Kei Ohkubo, Shunichi Fukuzumi, J. Phys. Chem. C, 2011, 115(16), 8325–8334. online versionPDF
Abstract:
A tetrathiafulvalene donor has been annulated to the
bay region of perylenediimide through a
1H-benzo[d]pyrrolo[1,2-a]imidazol-1-one
spacer affording an extended π-conjugated molecular
dyad (TTF−PDI). To gain insight into its ground- and
excited-state electronic properties, the reference
compound Ph-PDI has been prepared via a direct
Schiff-base condensation of
N,N′-bis(1-octylnonyl)benzoperylene-1′,2′:3,4:9,10-hexacarboxylic-1′,2′-anhydride-3,4:9,10-bis(imide)
with benzene-1,2-diamine. Both the experimental and
the computational (DFT) results indicate that TTF−PDI
exhibits significant intramolecular electronic
interactions giving rise to an efficient
photoinduced charge-separation process. Free-energy
calculations verify that the light-induced process
from TTF to the singlet-excited state of PDI is
exothermic in both polar and nonpolar solvents. Fast
adiabatic electron-transfer processes of a compactly
fused, π-conjugated TTF−PDI dyad in benzonitrile,
2-methyltetrahydrofuran, anisole and toluene were
observed by femtosecond transient absorption
spectral measurements. The lifetimes of radical-ion
pairs slightly increase with decreasing the solvent
polarities, suggesting that the charge-recombination
occurs in the Marcus inverted region. By utilizing
the nanosecond transient absorption technique, the
intermolecular electron-transfer process in a
mixture of TTF-diamine/Ph-PDI has been observed via
the triplet excited PDI for the first time.
Effect of the Addition of a Fused Donor−Acceptor Ligand on a Ru(II) Complex: Synthesis, Characterization, and Photoinduced Electron Transfer Reactions of [Ru(TTF-dppz)2(Aqphen)]2+
Nathalie Dupont, Ying-Fen Ran, Hong-Peng Jia, Jakob Grilj, Jie Ding, Shi-Xia Liu, Silvio Decurtins, Andreas Hauser, Inorg. Chem., 2011, 50(8), 3295-3303. online versionPDF
Abstract:
The synthesis and the photophysical properties of the
complex [Ru(TTF-dppz)2(Aqphen)]2+
(TTF = tetrathiafulvalene, dppz =
dipyrido-[3,2-a:2′,3′-c]phenazine,
Aqphen = anthraquinone fused to phenanthroline via a pyrazine
bridge) are described. In this molecular triad excitation
into the metal−ligand charge transfer bands results
in the creation of a long-lived charge separated state with
TTF acting as electron donor and anthraquinone as terminal
acceptor. The lifetime of the charge-separated stat is
400 ns in dichloromethane at room temperature. A
mechanism for the charge separation involving an intermediate
charge-separated state is proposed based on transient
absorption spectroscopy.
Orientation dependent molecular friction on organic layer compound crystals
Gregor Fessler, Iwan Zimmermann, Thilo Glatzel, Enrico Gnecco, Pascal Steiner, Raphael Roth, Tony D. Keene, Shi-Xia Liu, Silvio Decurtins, Ernst Meyer, Appl. Phys. Lett., 2011, 98(8), 083119/1-3. online versionPDF
Abstract:
High resolution friction force maps of the benzylammonium
terminated crystalline surface of a layer compound are
presented. The lateral force map acquired with an atomic
force microscope, reveals a significant contrast between
different molecular orientations yielding molecular rows
which differ from their neighboring ones. The single crystals
are formed by stacks of copper oxalate sheets sandwiched
between stereoregular organic cations, resulting in highly
organized surface structures. Single molecular defects are
observed at small loads. The experimental results are
compared with numerical calculations which indicate a
transition from an unperturbed state at small loads to a
distorted state at higher loads.
A tetrathiafulvalene-functionalized schiff base macrocycle: synthesis, electrochemical and photophysical properties
Ying-Fen Ran, Carmen Blum, Shi-Xia Liu, Lionel Sanguinet, Eric Levillain, Silvio Decurtins, Tetrahedron, 2011, 67(9), 1623-1627. online versionPDF
Abstract:
Highly selective formation of 2+2 macrocycle 1 from
2,5-bis(3-formyl-2-hydroxyphenyl)-1,3,4-oxadiazole
and a diamine-functionalized tetrathiafulvalene
derivative is reported. Its electronic properties
have been studied experimentally by the combination
of electrochemistry and UV-Vis-NIR spectroscopy.
Particularly, its largely extended π-conjugation
renders this novel macrocycle simultaneously a good
multielectron donor and a strong chromophore, which
is rationalized on the basis of density functional theory.
Iron(III)-Pivalate-Based Complexes with Tetranuclear {Fe4(μ3-O)2}8+ Cores and N-Donor Ligands: Formation of Cluster and Polymeric Architectures
Svetlana G. Baca, Irina G. Filippova, Tony D. Keene, Olga Botezat, Iurii L. Malaestean, Helen Stoeckli-Evans, Victor Ch. Kravtsov, Iurii Chumacov, Shi-Xia Liu, Silvio Decurtins, Eur. J. Inorg. Chem., 2011, (3), 356-367. online versionPDF
Abstract:
Different synthetic routes have been used for the
preparation of a new tetranuclear [Fe4O2(O2CCMe3)8(bpm)]
cluster (1) and a one-dimensional
coordination polymer [Fe4O2(O2CCMe3)8(hmta)]n
(2) (bpm = 2,2′-bipyrimidine and hmta =
hexamethylenetetramine). For cluster 1, two
structural isomers, 1a and 1b·3MeCN,
have been found. X-ray crystallographic analysis
showed that all complexes consist of a central
{Fe4(μ3-O)2}8+
core. In 1a, metal ions in the core are
additionally linked by six bridging pivalates as two
other pivalates and a bpm ligand are chelated to FeIII
ions, whereas in cluster 1b, metal ions in
the {Fe4(μ3-O)2}8+
core are linked by seven bridging pivalates and only
one carboxylate as well as bpm are chelated to the
iron centers. In coordination polymer 2,
[Fe4O2(O2CCMe3)8]
clusters are bridged by hmta ligands to form zigzag
chains. Magnetic measurements have been carried out
to characterize these complexes and revealed
antiferromagnetic interactions between FeIII
ions with best-fit parameters of Jwb
= –72.2 (1a) and –88.7 cm–1 (1b)
for wing···body interactions.
2010
Benzodifuran-Based π-Conjugated Copolymers for Bulk Heterojunction Solar Cells
H. Li, P. Jiang, C. Yi, C. Li, S.-X. Liu, S. Tan, B. Zhao, J. Braun, W. Meier, T. Wandlowski, S. Decurtins, Macromolecules, 2010, 43, 8058-8062. online versionPDF
Abstract:
Novel π-conjugated copolymers based on a soluble
electroactive benzo[1,2-b:4,5-b′]difuran
(BDF) chromophore have been synthesized by the
introduction of thiophene/benzo[c][1,2,5]thiadiazole/9-phenylcarbazole
comonomer units. These copolymers cover broad
absorption ranges from 250 to 700 nm with narrow
optical band gaps of 1.71−2.01 eV. Moreover, their
band gaps as well as their molecular electronic
energy levels are readily tuned by copolymerizing
the BDF core with different π-conjugated
electron-donating or withdrawing units in different
ratios. Bulk heterojunction solar cell devices are
fabricated using the copolymers as the electron
donor and PCBM ([6,6]-phenyl-C61-butyric
acid methyl ester) as the electron acceptor.
Preliminary research has revealed power conversion
efficiencies of 0.17−0.59% under AM 1.5 illumination
(100 mW/cm2).
Versatile Strategy To Access Fully Functionalized Benzodifurans: Redox-Active Chromophores for the Construction of Extended π-Conjugated Materials
C. Yi, C. Blum, M. Lehmann, S. Keller, S.-X. Liu, G. Frei, A. Neels, J. Hauser, S. Schürch, S. Decurtins, J. Org. Chem., 2010, 75, 3350-3357. online versionPDF
Abstract:
An efficient synthetic approach to construct a fully
substituted benzo[1,2-b:4,5-b′]difuran
(BDF) 2a via base-catalyzed double
annulations is presented. Compound 2a can
readily undergo Suzuki, Heck, and Sonogashira
coupling reactions to afford in good yields a
manifold of extended π-conjugated BDF derivatives,
e.g., with pyridine termini (4−6) and
with different spacers. These are highly luminescent
materials that undergo two reversible one-electron
oxidations. Remarkably, their photophysical and
electrochemical properties can be largely tuned by
methylation or protonation. Consequently, they can
function as pH-dependent fluorescence switches.
Finally, the observed electronic properties are
explained on the basis of density functional theory.
Heterocyclic amine directed synthesis of metal(II)-oxalates: investigating the magnetic properties of two complete series of chains with S = 5/2 to S = 1/2
T. D. Keene, I. Zimmermann, A. Neels, O. Sereda, J. Hauser, M. Bonin, M. B. Hursthouse, D. J. Price, S. Decurtins, Dalton Trans., 2010, 39, 4937-4950. online versionPDF
Abstract:
We report here two series of coordination polymer chains: the first being [M(II)(ox)(bnz)2]n
(M = Mn 1, Fe 2, Co 3, Ni
4, Cu 5 and Zn 6; ox =
oxalate C2O42-;
bnz = benzimidazole) and the second [M(II)(ox)(btz)2]n
(M = Mn 7, Fe 8, Co 9, Ni
10, Cu 11 and Zn 12; btz =
benzotriazole). The first series displays an unusual homometallic
[–Mi–Mii–Mii–]n
chain topology and the second series is isostructural to [Fe(II)(ox)(btz)2]n,
originally reported by Jia et al. (Collect. Czech. Chem. Commun.,
2002, 67, 1609–1615). These two series allow us to make
comparisons between the spin state of each metal and the magnetic coupling
interaction within an isostructural series spanning the full range of spin
states available in 3d metals and to investigate which models are the
best to use in each case. Compound 8 is a single-chain magnet,
the behaviour through spin-canting arising from a Dzyaloshinskii-Moriya
interaction. Additionally, we have synthesised a two-dimensional coordination
polymer {[Zn(II)(bnz)4][Zn(II)2(ox)3]}n
(13), in which distorted hexagonal
[Zn(II)2(ox)3]n2n-
layers are hydrogen bonded by [Zn(II)(bnz)4]2+
cations to give an interlayer separation of 12.001(2) Å.
A Scanning Probe Microscopy Study of Annulated Redox-Active Molecules at a Liquid/Solid Interface: The Overruling of the Alkyl Chain Paradigm
B. Liu, Y.-F. Ran, Z. Li, S.-X. Liu, C. Jia, S. Decurtins, T. Wandlowski, Chem. Eur. J., 2010, 16, 5008-5012. online versionPDF
Abstract:
Overruled! The self-assembly of a
novel group of fused donor-acceptor
molecules (1) comprising
hexaazatriphenylene and tetrathiafulvalene
branches was studied by STM at the
liquid/solid interface. A 2D assembled
chiral porous network of C3
symmetry was found, which is dictated by strong
interactions of the extended
π-conjugated cores
of the fused units with the HOPG substrate
overruling the directional forces of alkyl chains.
Crystal Engineering of a Series of Arylammonium Copper(II) Malonates
T. D. Keene, I. Zimmermann, A. Neels, O. Sereda, J. Hauser, S.-X. Liu, S. Decurtins, Cryst. Growth Des., 2010, 10, 1854-1859. online versionPDF
Abstract:
We present a series of eight layered copper(II)
malonates, each with a {[HA]2[Cu(II)(mal)2(H2O)x]}n
A−B−A layer structure, where A is an ammonium cation
and B is an anionic copper malonate layer (x
= 1 or 2; A = benzylamine, 1;
S-(α)-methylbenzylamine,
2; 4-methylbenzylamine, 3;
4-carboxybenzylamine, 4;
4-trifluoromethylbenzylamine, 5;
4-trifluoromethoxybenzylamine, 6;
phenylethylamine, 7; and
4-fluorophenylethylamine, 8). The ammonium
cations used are primary amines based around
benzylamine and phenylethylamine and include several
different functional groups. The different amines
give a large array of interlayer interactions,
including van der Waals packing, hydrogen bonding,
C−H···π,
π···π,
H···F, and F···F interactions.
Despite the various functionalities on the
arylammonium groups, the different interlayer
packing interactions, and the differing degrees of
hydration in the [Cu(II)(mal)2(H2O)x]2−
group, the anionic layer structure remains the same,
indicating a high stability of this layer and its
potential for further engineering of the organic
layer components.
Annulation of Tetrathiafulvalene to the Bay Region of Perylenediimide
M. Jaggi, C. Blum, B. S. Marti, S.-X. Liu, S. Leutwyler, S. Decurtins, Org. Lett., 2010, 12, 1344-1347. online versionPDF
Abstract:
A tetrathiafulvalene donor has been annulated to the bay region of
perylenediimide affording a new π-conjugated
molecular dyad. Various electronic excited charge-transfer states are
generated in different oxidation states, leading to almost full
absorption in the visible to near-IR region with a high extinction
coefficient.
Cyclic Conductance Switching in Networks of Redox-Active Molecular Junctions
J. Liao, J. S. Agustsson, S. Wu, C. Schönenberger, M. Calame, Y. Leroux, M. Mayor, O. Jeannin, Y.-F. Ran, S.-X. Liu, S. Decurtins, Nano Lett., 2010, 10, 759-764. online versionPDF
Abstract:
Redox-active dithiolated tetrathiafulvalene derivatives (TTFdT) were inserted in
two-dimensional nanoparticle arrays to build interlinked networks of molecular
junctions. Upon oxidation of the TTFdT to the dication state, we observed a
conductance increase of the networks by up to 1 order of magnitude. Successive
oxidation and reduction cycles demonstrated a clear switching behavior of the
molecular junction conductance. These results show the potential of interlinked
nanoparticle arrays as chemical sensors.
Half a grid is better than no grid: competition between 2,2':6',2''-terpyridine and 3,6-di(pyrid-2-yl)pyridazine for copper(II)
E. C. Constable, S. Decurtins, C. E. Housecroft, T. D. Keene, C. G. Palivan, J. R. Price, J. A. Zampese, Dalton Trans., 2010, 39, 2337-2343. online versionPDF
Graphical Abstract:
The assembly of a dinuclear half-grid
[Cu2(1)(tpy)2]4+
(1 = 3,6-di(pyrid-2-yl)pyridazine) in which inter-tpy
π-stacking controls the ligand
orientations in the solid state, competes with the formation
of [Cu(1)2(OH2)]2+.
An Electrochemical and Photophysical Study of a Covalently Linked Inorganic-Organic Dyad
A. Kahnt, L.-P. Heiniger, S.-X. Liu, X. Tu, Z. Zheng, A. Hauser, S. Decurtins, D. M. Guldi, Chem. Phys. Chem., 2010, 11, 651-658. online versionPDF
Abstract:
A molecular donor-acceptor dyad comprising a hexarhenium cluster core,
[Re6(μ3-Se)8]2+,
and a fullerene moiety which are covalently linked through a pyridine ligand was
synthesized and fully characterized. The electrochemical and photophysical
properties are reported. The detailed study includes cyclic voltammetry, steady-state
absorption and fluorescence spectroscopy, radiation chemistry and transient
absorption spectroscopy. A light-induced electron transfer between the
inorganic cluster moiety and the fullerene can be excluded. However, a light-induced
energy transfer from the rhenium cluster to the fullerene is proposed.
2009
Approaches to Fused Tetrathiafulvalene / Tetracyano-quinodimethane Systems
F. Dumur, X. Guégano, N. Gautier, S.-X. Liu, A. Neels, S. Decurtins, P. Hudhomme, Eur. J. Org. Chem., 2009, 6341-6354. online versionPDF
Graphical Abstract:
Reactions between malononitrile and cyclopentadiene-protected fused
2-thioxo-1,3-dithiole-p-benzoquinones under different experimental
conditions proceed either through the expected Knoevenagel condensation
to afford the corresponding TCNQ analogues or through Michael additions
with subsequent ring opening of the 1,3-dithiole moiety, leading to
ketene imines.
Preparation of Zwitterionic Hydroquinone-Fused [1,4]Oxazinium Derivatives via a Photoinduced Intramolecular Dehydrogenative-Coupling Reaction
C. Yi, S.-X. Liu, A. Neels, P. Renaud, S. Decurtins, Org. Lett., 2009, 11, 5530-5533. online versionPDF
Abstract:
A simple and efficient photochemical reaction can be performed to
construct functionalized [1,4]oxazinium derivatives via a direct
dehydrogenative coupling between sp3- and sp2-hybridized C-atoms,
starting from easily accessible stable semiquinone radicals.
Self-Assembly of Individually Addressable Complexes of C60 and Phthalocyanines on a Metal Surface: Structural and Electronic Investigations
T. Samuely, S.-X. Liu, M. Haas, S. Decurtins, T. A. Jung, M. Stöhr, J. Phys. Chem. C, 2009, 113, 19373–19375. online versionPDF
Abstract:
The hosting properties of a close-packed layer of phenoxy-substituted phthalocyanine
derivatives adsorbed on Ag(111) were investigated for the adsorption of C60 molecules. The
C60 molecules bind to two clearly distinguishable sites, namely, to the underlying metal
substrate in between two adjacent phthalocyanine derivatives, leading to structural and
electronic properties analogous to those of C60 adsorbed on Ag(111), and to the core of the
underlying phthalocyanine derivative, indicative of the formation of 1:1 donor-acceptor
(D-A) dyads through a true host-guest interaction. The electronic properties have been
determined by scanning tunneling spectroscopy measurements on individual D-A dyads.
Synthesis and electrochemical properties of TTF modified oligodeoxynucleotides
M. Schnippering, A. Zahn, S.-X. Liu, C. Leumann, S. Decurtins, D. J. Fermín, Chem. Commun., 2009, 5552-5554. online versionPDF
Abstract:
A new approach for labelling oligodeoxynucleotides with tetrathiafulvalene (TTF) units is presented,
generating single and double strand structures with distinctive electrochemical signatures.
Structural diversity in the reactions of 4'-(pyridyl)-2,2':6',2''-terpyridine ligands and bis{4'-(4-pyridyl)-2,2':6',2''-terpyridine}iron(II) with copper(II) salts
J. E. Beves, E. C. Constable, S. Decurtins, E. L. Dunphy, C. E. Housecroft, T. D. Keene, M. Neuburger, S. Schaffner, J. A. Zampese, Cryst. Eng. Comm., 2009, 11, 2406-2416. online versionPDF
Abstract:
We have demonstrated that treatment of [Fe(1)2]2+
(1 = 4'-(4-pyridyl)-2,2':6',2''-terpyridine)
with an excess of CuCl2·2H2O
leads to competition between coordination of copper(II) by the pendant pyridine
donors in [Fe(1)2]2+,
and transfer of ligand 1 from iron(II) to copper(II) to yield
[{Cl3Cu(μ-1)Fe(μ-1)}2CuCl2(OH2)2]Cl2·4H2O
and [Cu(H1)Cl2]Cl·4H2O,
respectively. Direct reaction of 1 with CuCl2·2H2O
and variation in crystallization conditions results in the formation of either
monomeric or polymeric complexes: [Cu(1)Cl2]·4.75H2O,
[Cu(1)Cl2]·H2O·MeOH
and [Cu(1)Cl2·2H2O]n.
The reaction of 1 with Cu(NO3)2·3H2O
gives the coordination polymer [Cu(1)(ONO2)2·H2O]n.
Magnetic data for [Cu(1)Cl2·2H2O]n
and [Cu(1)(ONO2)2·H2O]n
are consistent with antiferromagnetically-coupled chains. Reactions of CuCl2·2H2O
with ligands 2 and 3 (2 = 4'-(3-pyridyl)-2,2':6',2''-terpyridine,
3 = 4'-(2-pyridyl)-2,2':6',2''-terpyridine)
lead to monomeric complexes. With the exception of [Cu(3)Cl2],
the mononuclear complexes show a propensity for the incorporation of water into
their crystal lattices; in the case of [Cu(H1)Cl2]Cl·4H2O
and [Cu(H1)Cl2]Cl·4.75H2O,
the small change in water content leads to the assembly of (5.82)2(5.6.8)4(52.6)2
or (42.62)3(4.62)6
water–chloride ion nets.
A Compactly Fused π-Conjugated Tetrathiafulvalene-Perylenediimide Donor-Acceptor Dyad
M. Jaggi, C. Blum, N. Dupont, J. Grilj, S.-X. Liu, J. Hauser, A. Hauser, S. Decurtins, Org. Lett., 2009, 11, 3096-3099. online versionPDF
Abstract:
The synthesis and structural characterization of a tetrathiafulvalene-fused
perylenediimide molecular dyad is presented. Its largely extended
π-conjugation provides intense optical absorption
bands over a wide spectral range. The planar functional molecule exhibits a
short-lived nonluminescent excited state attributed to intramolecular charge
separation.
Star-Shaped Tetrathiafulvalene-Fused Coronene with Large π-Extended Conjugation
H.-P. Jia, S.-X. Liu, L. Sanguinet, E. Levillain, S. Decurtins, J. Org. Chem., 2009, 74, 5727-5729. online versionPDF
Abstract:
A tristar shaped, planar TTF-fused coronene 1 was synthesized. Its electronic
properties have been studied experimentally by the combination of electrochemistry
and UV-vis-NIR spectroscopy. Thereby, a nanosized graphite fragment is largely
extended in its size, supplemented with a multielectron donor functionality,
and shaped to a strongly chromophoric species absorbing intensely in the visible
part of the optical spectrum.
Isolable Zwitterionic Pyridinio-semiquinone π-Radicals. Mild and Efficient Single-Step Access to Stable Radicals
C. Yi, C. Blum, S.-X. Liu, T. D. Keene, G. Frei, A. Neels, S. Decurtins, Org. Lett., 2009, 11, 2261-2264. online versionPDF
Abstract:
A rational design based on the proton-coupled electron transfer (PCET)
concept allows us to structurally characterize for the first time isolable,
air- and moisture-stable semiquinone radicals in a zwitterionic neutral form.
The presence of an alkoxy and the bulky pyridinio substituents causes only
a minor perturbation of either the redox potentials or the spectral UV-vis
characteristics of the semiquinone core but significantly stabilizes the new
radicals.
[M(OOCC6H4PO3H)(H2O)] (M(II) = Mn, Co, Ni): layered metal phosphonates showing variable magnetic behavior
J.-T. Li, T. D. Keene, D.-K. Cao, S. Decurtins, L.-M. Zheng, Cryst. Eng. Comm., 2009, 11, 1255-1260. online versionPDF
Abstract:
Three novel isomorphous transition metal phosphonate
compounds with formula [M(OOCC6H4PO3H)(H2O)]
[M(II) = Mn (1), Co(2), Ni (3)]
were prepared through hydrothermal reaction of
2-carboxyphenylphosphonic acid and metal salts. Within the
structure, the {M2O2}
dimers made up of edge-sharing {MO6}
octahedra are connected by carboxylate and/or phosphonate groups,
leading to a 2-D layer. The phenyl groups fill in the
inter-layer spaces. Magnetic measurements reveal that dominant
antiferromagnetic interactions are observed in compounds
1 and 2, while for compound 3,
the dominant ferromagnetic interaction leads to a spontaneous
ferromagnetic long range ordering below Tc
= 4.0 K.
Magnetostructural investigations into an S = 1/2 sheet and a tetranuclear butterfly cluster
T. D. Keene, Y.-H. Deng, F.-G. Li, Y.-F. Ding, B. Wu, S.-X. Liu, C. Ambrus, O. Waldmann, S. Decurtins, X.-J. Yang, Inorg. Chim. Acta, 2009, 362, 2265-2269. online versionPDF
Abstract:
We present a detailed analysis of the magnetic properties of two Cu(II)
coordination compounds with the tetrazole-1-acetate ligand (t1a),
previously reported in literature by Yu et al. [Q. Yu, X. Zhang, H. Bian, H.
Liang, B. Zhao, S. Yan, D. Liao, Cryst. Growth Des. 8 (2008) 1140] and
simultaneously synthesised independently by ourselves. We focus on methods of
describing the susceptibility and magnetisation of a ferromagnetically-coupled
S = 1/2 square network (2) and a tetranuclear
S = 1/2 ‘butterfly’ cluster (4) as well as discussion
of the energy levels of such a cluster.
Imidazole-Annulated Tetrathiafulvalenes Exhibiting pH-Tuneable Intramolecular Charge Transfer and Redox Properties
J. Wu, N. Dupont, S.-X. Liu, A. Neels, A. Hauser, S. Decurtins, Chem. Asian J., 2009, 4, 392-399. online versionPDF
Abstract:
In order to study the electronic interactions in donor-acceptor ensembles as
a function of pH, an efficient synthetic route to three imidazole-annulated
tetrathiafulvalene (TTF) derivatives 1-3 is reported. Their
electronic absorption spectra, in view of photoinduced intramolecular charge
transfer, and their electrochemical behavior were investigated, and pKa
values for the two protonation processes on the acceptor unit were determined in
organic solvents by photometric titration. The influence of the TTF moiety on
these values is discussed.
Pronounced Electrochemical Amphotericity of a Fused Donor-Acceptor Compound: A Planar Merge of TTF with a TCNQ-Type Bithienoquinoxaline
X. Guégano, A. L. Kanibolotsky, C. Blum, S. F. L. Mertens, S.-X. Liu, A. Neels, H. Hagemann, P. J. Skabara, S. Leutwyler, T. Wandlowski, A. Hauser, S. Decurtins, Chem. Eur. J., 2009, 15, 63-66. online versionPDF
Graphical Abstract:
Narrowing the gap - A compactly fused π-conjugated molecule combines a high-lying HOMO
with a low-lying LUMO (Eox-Ered=0.52 eV) and a fairly low-lying LUMO+1 on the bridging unit,
giving rise to strong optical charge transfer transitions. A facile electron transfer
has been observed by EPR and NMR spectroscopy.
2008
One-Dimensional Manganese Coordination Polymers Composed of Polynuclear Cluster Blocks and Polypyridyl Linkers: Structures and Properties
S. G. Baca, I. L. Malaestean, T. D. Keene, H. Adams, M. D. Ward, J. Hauser, A. Neels, S. Decurtins, Inorg. Chem., 2008, 47, 11108-11119. online versionPDF
Abstract:
The synthesis, crystal structures and magnetic properties of
five new manganese compounds are reported. These include a linear trinuclear
cluster [Mn(II)3(O2CCHMe2)6(dpa)2]·2MeCN
(1) (dpa = 2,2′-dipyridylamine), a tetranuclear cluster
[Mn(II)2Mn(III)2O2(O2CCMe3)6(bpy)2]
(3) (bpy = 2,2′-bipyridine), and chain coordination polymers composed of
cluster blocks such as Mn3, Mn3O, and Mn4O2
bridged by 2,2′-bipyrimidine (bpm) or hexamethylentetramine (hmta) ligands to
give ([Mn(II)3(O2CCHMe2)6(bpm)]·2EtOH)n
(2), [Mn(II)2Mn(III)2O2(O2CCHMe2)6(bpm)(EtOH)4]n
(4), and (([Mn(II)Mn(III)2O(O2CCHMe2)6(hmta)2]·EtOH)n
(5). The magnetic analysis of the compounds was achieved using a
combination of vector coupling and full-matrix diagonalization methods.
Susceptibility data for compound 1 was fitted using a vector coupling
model to give g = 2.02(1) and 2J/kB = −5.38(2)
K. To model the trimer chain, we used vector coupling for initial values of J1
and then diagonalization techniques to estimate J2 to give
g = 1.98(1), 2J1/kB = −3.3(1) K and 2J2/kB
= −1.0(1) K by approximating the system to a dimer of trimers. The analysis of
3 was made difficult by the mixture of polymorphs and the difficulties of
a three-J model, while for 4 an analysis was not possible because
of the size of the computation and the relative magnitudes of the three
couplings. Compound 5 was modeled using the same techniques as 2
to give g = 1.99(1), 2J1/kB =
+32.5(2) K, 2J2/kB = −16.8(1) K, and 2J3/kB
= +0.4(1) K. The combination of techniques has worked well for compounds 2
and 5 and thus opens up a method of modeling complex chains.
Ruthenium(II) Coordination Chemistry of a Fused Donor−Acceptor Ligand: Synthesis, Characterization, and Photoinduced Electron-Transfer Reactions of [{Ru(bpy)2}n(TTF-ppb)](PF6)2n (n = 1, 2)
C. Goze, N. Dupont, E. Beitler, C. Leiggener, H. Jia, P. Monbaron, S.-X. Liu, A. Neels, A. Hauser, S. Decurtins, Inorg. Chem., 2008, 47, 11010-11017. online versionPDF
Abstract:
A π-extended, redox-active bridging ligand
4′,5′-bis(propylthio)tetrathiafulvenyl[i]dipyrido[2,3-a:3′,2′-c]phenazine
(L) was prepared via direct Schiff-base condensation of the corresponding
diamine−tetrathiafulvalene (TTF) precursor with 4,7-phenanthroline-5,6-dione.
Reactions of L with [Ru(bpy)2Cl2] afforded its
stable mono- and dinuclear ruthenium(II) complexes 1 and 2. They
have been fully characterized, and their photophysical and electrochemical
properties are reported together with those of [Ru(bpy)2(ppb)]2+
and [Ru(bpy)2(π-ppb)Ru(bpy)2]4+ (ppb =
dipyrido[2,3-a:3′,2′-c]phenazine) for comparison. In all cases,
the first excited state corresponds to an intramolecular TTF → ppb
charge-transfer state. Both ruthenium(II) complexes show two strong and
well-separated metal-to-ligand charge-transfer (MLCT) absorption bands, whereas
the 3MLCT luminescence is strongly quenched via electron transfer
from the TTF subunit. Clearly, the transient absorption spectra illustrate the
role of the TTF fragment as an electron donor, which induces a triplet
intraligand charge-transfer state (3ILCT) with lifetimes of
approximately 200 and 50 ns for mono- and dinuclear ruthenium(II) complexes,
respectively.
J. M. Herrera, P. Franz, R. Podgajny, M. Pilkington, M. Biner, S. Decurtins, H. Stoeckli-Evans, A. Neels, R. Garde, Y. Dromzée, M. Julve, B. Sieclucka, K. Hashimoto, S. Okhoshi, M. Verdaguer, C. R. Chimie, 2008, 11, 1192-1199. online versionPDF
Abstract:
We report the synthesis, the single-crystal X-ray crystallographic structures and the magnetic properties of three new isostructural
cyanido-bridged networks: [MIV{(μ-CN)4MnII(H2O)2}2·4H2O]n
[MIV = NbIV (1), MoIV (2), WIV
(3)]. For compound 1, the magnetic properties reveal a ferrimagnetic
phase below 50 K. In contrast, compounds 2 and 3 show a paramagnetic behaviour with no magnetic ordering
down to 2 K. The only electronic difference between the two kinds of compounds is the presence of two paired electrons on MoIV
(2) and WIV (3) (d2 electronic configuration, S = 0)
with no possible exchange interactions with MnII ions (d5 electronic configuration, S = 5/2) and
one unpaired electron on NbIV (1) (d1, S = 1/2) which allows
NbIV–MnII antiferromagnetic exchange interactions and the onset of a three-dimensional magnetic ordering
under Curie temperature. These three compounds demonstrate how one unpaired electron, well located, can dramatically
change the magnetic behaviour of isostructural octacyanido-based three-dimensional networks.
An efficient one-pot synthesis of strongly fluorescent (hetero)arenes polysubstituted with amino and cyano groups
C. Yi, C. Blum, S.-X. Liu, G. Frei, A. Neels, H. Stoeckli-Evans, S. Leutwyler, S. Decurtins, Tetrahedron, 2008, 64, 9437-9441. online versionPDF
Abstract:
An efficient one-pot synthesis simultaneously results in three types
of densely substituted mono-, di- and tetracyclic π-systems
which can easily be isolated. Each chromophore presents a strong
fluorescence emission, either in the red, green or blue part of the
spectrum.
A Layered Red-Emitting Chromophoric Organic Salt
C. Yi, C. Blum, S.-X. Liu, Y.-F. Ran, G. Frei, A. Neels, H. Stoeckli-Evans, G. Calzaferri, S. Leutwyler, S. Decurtins, Cryst. Growth Des., 2008, 8, 3004-3009. online versionPDF
Abstract:
We have investigated a synthetic route as well as the molecular assembly
and the optical properties of a novel π-conjugated system, namely, the anion
(E)-3-(3-amino-2,4-dicyanophenyl)-1,1-dicyanoprop-2-en-1-ide, in the
form of its tetrabutylammonium salt (1). Through the combined actions
of directional hydrogen bonds and Coulombic interactions, a two-dimensional
molecular topology is realized whereby the extended monolayers of the
strongly chromophoric π-conjugated anions are spatially isolated by the
tetrabutylammonium cations. The chromophoric properties of the anion
originate from very intense low-energy
π–π* absorptions, with a high
oscillator strength, fexp = 0.84 at 468 nm. Further
characteristic features are a
S1S0
fluorescence emission not only in solution but also in the solid state at
room temperature. The remarkable type of organization of the organic
chromophores into a solid state sheet structure suppresses a possible
quenching of a solid state emission and, quite interestingly, allows in
principle probing of the photoexcited exciton states based on a defined
molecular geometry.
Experimental and theoretical study of the spin ground state of the high-spin molecular cluster [NiII{NiII(CH3OH)3}8(μ-CN)30{WV(CN)3}6] · 15CH3OH by polarised neutron diffraction and density functional theory calculations
B. Gillon, J. Larionova, E. Ruiz, Q. Nau, A. Goujon, F. Bonadio, S. Decurtins, Inorg. Chim. Acta, 2008, 361, 3609-3615. online versionPDF
Abstract:
Exchange mechanisms in the high-spin
molecular cluster [NiII{NiII(CH3OH)3}8(μ-CN)30{WV(CN)3}6] · 15CH3OH
have been investigated by a combination of
polarised neutron diffraction studies on a
single crystal and theoretical calculations. The
experimental spin density has been deduced from
a model refinement on the basis of magnetic
structure factors collected at 1.6 K under a
field of 5 T. Positive spin populations were
observed on both, the nickel and the tungsten
sites, which provides an evidence of
ferromagnetic NiII–WV
exchange interactions through the cyano bridge.
A positive spin density was also observed on
nitrogen atoms of the bridging cyano groups
indicating a spin delocalisation mechanism. The
mean experimental spin populations are in good
agreement with the calculated ones, obtained by
using the NBO method and the B3LYP functional.
The theoretical evidence for ferromagnetic NiII–WV
interactions was also given by calculations of
the exchange coupling constants on the whole
complex.
Homoleptic metal complexes of 4'-(5-pyrimidinyl)-2,2':6',2''-terpyridine: tetrafurcated expanded ligands
J. E. Beves, E. C. Constable, S. Decurtins, E. L. Dunphy, C. E. Housecroft, T. D. Keene, M. Neuburger, S. Schaffner, Cryst. Eng. Comm., 2008, 10, 986-990. online versionPDF
Abstract:
With iron(II) and ruthenium(II), 4'-(5-pyrimidinyl)-2,2':6',2''-terpyridine
(L) preferentially coordinates through the tpy domain to give
octahedral [ML2]2+
(M = Fe, Ru) complexes. Treatment of [RuL2][PF6]2
with CuCl2·2 H2O
leads to {[Ru(2)2][CuCl2(OH2)][CuCl3]Cl·3MeCN·7H2O}n
which exhibits a two-dimensional coordination network with
copper(II) centres interconnecting [RuL2]2+
motifs. Magnetic susceptibility data for the material are
consistent with a one-dimensional S = 1/2 antiferromagnetic
chain.
TTF-Modified DNA
N. Bouquin, V. L. Malinovskii, X. Guégano, S.-X. Liu, S. Decurtins, R. Häner, Chem. Eur. J., 2008, 14, 5732-5736. online versionPDF
I. Zimmermann, T. D. Keene, A. Neels, S. Decurtins, Acta Cryst. E, 2008, E64, m845-m846. online versionPDF
Abstract:
In the title compound, [Co2(C2H3O2)4(C7H6N2)4(H2O)],
the half-molecule in the asymmetric unit is completed by a crystallographic
twofold rotation axis to give the full molecule. The CoII
ions are approximately octahedrally coordinated with a cis-N2O4
coordination sphere. The compound features intramolecular O-H··O
hydrogen bonds between the non-bridging acetate groups and the bridging water
molecule, and intermolecular N-H···O
hydrogen bonds between the acetates and amine H atoms of the benzimidazoles
which determine the molecular packing in the crystal structure.
Two-Dimensional Multiphase Behavior Induced by Sterically Hindered Conformational Optimization of Phenoxy-Substituted Phthalocyanines
T. Samuely, S.-X. Liu, N. Wintjes, M. Haas, S. Decurtins, T. A. Jung, M. Stöhr, J. Phys. Chem. C, 2008, 112, 6139-6144. online versionPDF
Abstract:
Symmetrically substituted phthalocyanines (Pcs) with eight peripheral
di-(tert-butyl)phenoxy (DTPO) groups self-organize on Ag(111) and Au(111)
substrates into various assembly structures. These different structural
phases were studied by scanning tunneling microscopy (STM). On the basis of
high-resolution STM images, molecular models are provided for each phase
that account for the observed unequal surface densities. Notably, the
specificity of the studied Pc derivative featuring the peripheral phenoxy
groups remarkably increases its conformational possibilities. Particularly,
the rotational degrees of freedom allow all the DTPO substituents to be
arranged above the plane of the Pc core, forming a bowl-like structure,
which in turn enables the interaction of the Pc core with the metal
substrate. The proximity of the Pc core to the metal substrate together with
the steric entanglement between neighboring DTPO substituents causes
significant retardation of the thermodynamic optimization of the
conformations.
Coordination Chemistry of a π-Extended, Rigid and Redox-Active Tetrathiafulvalene-Fused Schiff-Base Ligand
J.-C. Wu, S.-X. Liu, T. D. Keene, A. Neels, V. Mereacre, A. K. Powell, S. Decurtins, Inorg. Chem., 2008, 47, 3452-3459. online versionPDF
Abstract:
A π-extended, redox-active tetradentate
tetrathiafulvalene-fused salphen [salphen = N,N'-phenylenebis(salicylideneimine)]
compound (L) was prepared via a direct Schiff-base condensation of the
corresponding diamine-tetrathiafulvalene (TTF) precursor with salicylaldehyde.
Its chelating coordination ability has been demonstrated by the formation of the
corresponding transition metal complexes in the presence of M(OAc)2·nH2O
(M = Co(II), Ni(II), Cu(II)) and FeCl3·6H2O. Three
complexes have been characterized by single-crystal X-ray diffraction analysis
showing that the TTF-salphen ligand coordinates to the metal ions in a planar
mode through the nitrogen and oxygen atoms in a N2O2
cis-configuration. In the case of Fe(III), a dinuclear oxo-bridged Fe(III)
complex is formed. These paramagnetic complexes are promising building blocks
for the construction of dual functional materials due to their unique structural
features (planarity and rigidity) as well as their inherent redox properties.
An Efficient and Facile Synthesis of Highly Substituted 2,6-Dicyanoanilines
C. Yi, C. Blum, S.-X. Liu, G. Frei, A. Neels, P. Renaud, S. Leutwyler, S. Decurtins, J. Org. Chem., 2008, 73, 3596-3599. online versionPDF
Abstract:
A one-pot procedure for the synthesis of substituted 2,6-dicyanoanilines starting from readily available ynones and
malononitrile has been developed. For instance, penta-1,4-diyn-3-one is converted into the acetylene-substituted
aniline derivative 1 in good yield. Upon photoexcitation, this chromophore shows a strong blue emission with a
high quantum yield. The ground- and the excited-state geometries, charge distributions, and excitation energies
of 1 have been evaluated by ab initio calculations.
Synthesis of new ethynylbipyridine-linked mono- and bis-tetrathiafulvalenes: electrochemical, spectroscopic and Ru(II)-binding studies
C. Goze, S.-X. Liu, C. Leiggener, L. Sanguinet, E. Levillain, A. Hauser, S. Decurtins, Tetrahedron, 2008, 64, 1345-1350. online versionPDF
Abstract:
Two new ethynylbipyridine-linked mono- and bis-tetrathiafulvalene (TTF) derivatives, together with a Ru(II) complex, were
synthesized using Sonogashira coupling reactions and characterized by UV/vis spectroscopy and cyclic voltammetry. They display a clear
electrochemically amphoteric behaviour consisting of two reversible single-electron oxidation waves (typical for TTF derivatives) and one
reversible single-electron reduction wave (bpy) and act as donor-acceptor (D-A) systems. Furthermore, for the Ru(II) complex, a quite
intense fluorescence originating from the 3MLCT state is observed.
2007
Mixed-ligand platinum and palladium complexes based on dinitrogen chelating ligands and a pyridine bearing the nitronylnitroxide radical
A. M. Shemsi, B. El Ali, K. A. Ziq, M. Morsy, T. D. Keene, S. Decurtins, M. Fettouhi Inorg. Chem. Commun., 2007, 10, 1355-1359. online versionPDF
Abstract:
Novel cationic mixed-ligand palladium and platinum complexes
based on the chelating ligands 4,7-dimethyl-1,10-phenanthroline
and 2,2′-bipyridine with a pyridine bearing the
nitronylnitroxide radical are reported. The synthesis, X-ray
crystal structures and magnetic properties of the two complexes
[Pd(4,7-dimethyl-1,10-phenanthroline)(NIT-pPy)2](PF6)2.
DMF and [Pt(2,2′-bipyridine-N,N′)(NIT-pPy)2](PF6)2 · 0.25H2O,
(where NIT-pPy = 2-(p-pyridyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide)
are described. The two metal complexes show a strained square
planar geometry. Short intermolecular contacts take place
through the nitroxide groups and weak intermolecular
antiferromagnetic interactions are dominant at low temperature.
Photoinduced Energy Transfer Processes within Dyads of Metallophthalocyanines Compactly Fused to a Ruthenium(II) Polypyridine Chromophore
M. Haas, S.-X. Liu, A. Kahnt, C. Leiggener, D. M. Guldi, A. Hauser, S. Decurtins, J. Org. Chem., 2007, 72, 7533-7543. online versionPDF
Abstract:
An unsymmetric, peripherally octasubstituted phthalocyanine (Pc) 1,
which contains a combination of dipyrido[3,2-f:2',3'-h]
quinoxaline and 3,5-di-tert-butylphenoxy substituents, has been obtained
via a statistical condensation reaction of two corresponding phthalonitriles.
Synthetic procedures for the selective metalation of the macrocyclic cavity and
the periphery of 1 were developed, leading to the preparation of the key
precursor metallophthalocyanines 3-5 in good yields. Two different
strategies were applied to the synthesis of compact dyads MPc-Ru(II) 6-8
(M = Mg(II), Co(II), Zn(II)). Intramolecular electronic interactions in these
dyads were studied by absorption, emission, and transient absorption
spectroscopy. Upon photoexcitation, these dyads exhibit efficient intramolecular
energy transfer from the Ru(II) chromophore to the MPc moiety.
A tetrathiafulvalene-tetracyanoanthraquinodimethane (TTF-TCNAQ) diad with a chemically tunable HOMO–LUMO gap
J. Wu, S.-X. Liu, A. Neels, F. Le Derf, M. Sallé, S. Decurtins, Tetrahedron, 2007, 63, 11282-11286. online versionPDF
Abstract:
An imidazole-incorporated TTF-TCNAQ diad was synthesized, which shows remarkable optical and electrochemical
responses as a function of pH.
An Original Redox-Responsive Ligand Based on a π-Extended TTF Framework
S. Dolder, S.-X. Liu, F. Le Derf, M. Sallé, A. Neels, S. Decurtins, Org. Lett., 2007, 9, 3753-3756. online versionPDF
Abstract:
The synthesis of the first π-extended
tetrathiafulvalene (TTF) ligand featuring a furanoquinonoid spacer and pyridyl
functional groups is described. This compound shows an unprecedented
electrochemical sensing behavior and excellent coordinating properties toward
selected divalent metal ions. Solid-state structures of the free ligand and its
Ni(II)Cl2 complex are described.
Fused Donor-Acceptor Ligands in RuII Chemistry: Synthesis, Electrochemistry and Spectroscopy of [Ru(bpy)3-n(TTF-dppz)n](PF6)2
C. Goze, C. Leiggener, S.-X. Liu, L. Sanguinet, E. Levillain, A. Hauser, S. Decurtins, Chem. Phys. Chem., 2007, 8, 1504-1512. online versionPDF
Abstract:
Three ruthenium(II) polypyridine complexes of general formula
[Ru(bpy)3-n(TTF-dppz)n](PF6)2
(n=1-3, bpy=2,2'-bipyridine),
with one, two or three redox-active TTF-dppz
(4',5'-bis(propylthio)tetrathiafulvenyl[i]dipyrido[3,2-a:2',3'-c]phenazine)
ligands, were synthesised and fully characterised. Their electrochemical and
photophysical properties are reported together with those of the reference
compounds [Ru(bpy)3](PF6)2, [Ru(dppz)3](PF6)2
and [Ru(bpy)2(dppz)](PF6)2 and the free
TTF-dppz ligand. All three complexes show intraligand charge-transfer (ILCT)
fluorescence of the TTF-dppz ligand. Remarkably, the complex with n=1
exhibits luminescence from the
Ru2+ dppz
metal-to-ligand charge-transfer (3MLCT) state, whereas for the other
two complexes, a radiationless pathway via electron transfer from a second
TTF-dppz ligand quenches the 3MLCT luminescence. The
TTF fragments as electron donors thus induce a ligand-to-ligand charge-separated
(LLCS) state of the form TTF-dppz--Ru2+-dppz-TTF+.
The lifetime of this LLCS state is approximately
2.3 µs,
which is four orders of magnitude longer than that of 0.4 ns for the ILCT state,
because recombination of charges on two different ligands is substantially
slower.
An Experimental and Computational Study on Intramolecular Charge Transfer: A Tetrathiafulvalene-Fused Dipyridophenazine Molecule
C. Jia, S.-X. Liu, C. Tanner, C. Leiggener, A. Neels, L. Sanguinet, E. Levillain, S. Leutwyler, A. Hauser, S. Decurtins, Chem. Eur. J., 2007, 13, 3804-3812. online versionPDF
Abstract:
To study the electronic interactions in donor-acceptor (D-A) ensembles,
D and A fragments are coupled in a single molecule. Specifically, a
tetrathiafulvalene (TTF)-fused dipyrido[3,2-a:2’,3’-c]phenazine (dppz)
compound having inherent redox centers has been synthesized and structurally
characterized. Its electronic absorption, fluorescence emission, photoinduced
intramolecular charge transfer, and electrochemical behavior have been
investigated. The observed electronic properties are explained on the
basis of density functional theory.
Synthesis, structure and properties of {M4O4} cubanes containing nickel(II) and cobalt(II)
K. Isele, F. Gigon, A. F. Williams, G. Bernardinelli, P. Franz , S. Decurtins, Dalton Trans., 2007, 332-341. online versionPDF
Abstract:
A survey of the crystal structures containing simple
{M4O4} cubane units is
reported. It shows that the average M–M distance in these complexes is
relatively constant for a given metal ion M. The structures are all distorted
from the idealised cube to a Td structure, and
most show a further distortion which, however, usually maintains some elements
of symmetry. A system for classifying the different types of ligand in these
complexes is proposed. Two new cubanes of cobalt(II) and
nickel(II) with the ligand
(R,R)-bis-1,2-(1-methylbenzimidazol-2-yl)ethane-1,2-diol,
(R,R)-1 or its enantiomer have been isolated and
the crystal structure of the cobalt(II) complex confirms the
cubane structure. Electronic, CD and 1H NMR spectra
and magnetic susceptibility data are reported. The magnetic data for these and
other compounds in the literature are discussed in terms of the structural
parameters.
2006
Preparation and characterization of 3-(4,5-ethylenedithio-1,3-dithiol-2-ylidene)naphthopyranone: a luminescent redox-active donor–acceptor compound
S. Dolder, S.-X. Liu, X. Guégano, M. Atanasov, C. A. Daul, C. Leiggener, A. Hauser, A. Neels, S. Decurtins, Tetrahedron, 2006, 62, 11106-11111. online versionPDF
Abstract:
A new 1,3-dithiol-2-ylidene substituted naphthopyranone 2 has
been synthesized and characterized. UV–vis spectroscopic and cyclic voltammetry
results, interpreted on the basis of density functional theory, show that
2 displays an intramolecular charge-transfer transition and
acts like a donor–acceptor (D–A) system. Furthermore, a weak fluorescence
originating from the excited charge-transfer state is observed.
C. Jia, S.-X. Liu, C. Ambrus, A. Neels, G. Labat, S. Decurtins, Inorg. Chem., 2006, 45, 3152-3154. online versionPDF
Abstract:
A new tetrathiafulvalene derivative 1 bearing a single pyridine group and
its coordination complex 2, with stoichiometry
[Mn(μ-Cl)Cl(1)2(CH3OH)]n,
have been synthesized and fully characterized. The complex 2 shows an
extended chain structure, which is potentially favorable for electrical
conductivity. Notably, this is the first monohalogen-bridged Mn(II) polymer
exhibiting a moderate antiferromagnetic coupling between the Mn(II) centers.
A redox-active tri-star molecule: merging of TTF and HAT chemistry
C. Jia, S.-X. Liu, C. Tanner, C. Leiggener, L. Sanguinet, E. Levillain, S. Leutwyler, A. Hauser, S. Decurtins, Chem. Commun., 2006, 1878-1880. online versionPDF
Abstract:
A planar π-conjugated
heteroaromatic molecule 1 has been synthesized and fully
characterized; it combines two characteristics, a charge-transfer transition
originating from its inherent donor–acceptor nature in its neutral state and an
intervalence charge-transfer transition in its
12+ mixed-valence state.
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S0
fluorescence emission not only in solution but also in the solid state at
room temperature. The remarkable type of organization of the organic
chromophores into a solid state sheet structure suppresses a possible
quenching of a solid state emission and, quite interestingly, allows in
principle probing of the photoexcited exciton states based on a defined
molecular geometry.
