Our Research Goal

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.

The following abstracts of a few selected publications give an overview of our main research fields.


Research Highlights 2006-....

2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017

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2017


new

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.
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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

Oleg Reu, Serghei Ostrovsky, Silvio Decurtins, Shi-Xia Liu, Sophia Klokishner,
Eur. J. Inorg. Chem., 2017, in press.
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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.
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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

Tobias Meier, Rémy Pawlak, Shigeki Kawai, Yan Geng, Xunshan Liu, Silvio Decurtins, Prokop Hapala, Alexis Baratoff, Shi-Xia Liu, Pavel Jelinek, Ernst Meyer, Thilo Glatzel,
ACS Nano, 2017, 11(8), 8413-8420.
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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

Laerte L. Patera, Xunshan Liu, Nico Mosso, Silvio Decurtins, Shi-Xia Liu, Jascha Repp,
Angew. Chem. Int. Ed., 2017, 56(36), 10786-10790.
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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

Songjie Chen, Xiao Huang, Silvio Decurtins, Christiane Albrecht, Shi-Xia Liu,
Polyhedron, 2017, 134, 287-294.
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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.
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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, Milos Baljozovic, 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.
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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.
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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.
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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

Nemanja Kocić, Silvio Decurtins, Shi-Xia Liu, Jascha Repp,
J. Chem. Phys., 2017, 146(9), 092327/1-8.
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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.
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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

Marianna Roman, Silvio Decurtins, Shi-Xia Liu, Sophia Klokishner,
Eur. J. Inorg. Chem., 2016, (34), 5324-5331.
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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.
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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

Xunshan Liu, Songjie Chen, Jürg Hauser, Vladimir Laukhin, Silvio Decurtins, Ulrich Aschauer, Shi-Xia Liu,
Cryst. Growth Des., 2016, 16(9), 5230-5237.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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 {MnIII33-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.
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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

Fabrice Pointillart, Julie Jung, Romain Berraud-Pache, Boris Le Guennic, Vincent Dorcet, Stéphane Golhen, Olivier Cador, Olivier Maury, Yannick Guyot, Silvio Decurtins, Shi-Xia Liu, Lahcène Ouahab,
Inorg. Chem., 2015, 54(11), 5384-5397.
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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

Birte Varnholt, Romain Letrun, Jesse Bergkamp, Yongchun Fu, Oleksandr Yushchenko, Silvio Decurtins, Eric Vauthey, Shi-Xia Liu, Thomas Bürgi,
Phys. Chem. Chem. Phys., 2015, 17(22), 14788-14795.
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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

An Xiang, Hui Li, Songjie Chen, Shi-Xia Liu, Silvio Decurtins, Meilin Bai, Shimin Hou, Jianhui Liao,
Nanoscale, 2015, 7(17), 7665-7673.
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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.
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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.
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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.
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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.
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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

Yongchun Fu, Songjie Chen, Akiyoshi Kuzume, Alexander Rudnev, Cancan Huang, Veerabhadrarao Kaliginedi, Masoud Baghernejad, Wenjing Hong, Thomas Wandlowski, Silvio Decurtins, Shi-Xia Liu,
Nature Commun., 2015, 6, 6403/1-7.
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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

Jesse J. Bergkamp, Silvio Decurtins, Shi-Xia Liu,
Chem. Soc. Rev., 2015, 44(4), 863-874.
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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.
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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.
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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.
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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.
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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(CH2Cl2x(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

Wei Wang, Na Zhao, Yan Geng, Shi-Bin Cui, Jürg Hauser, Silvio Decurtins, Shi-Xia Liu,
RSC Adv., 2014, 4(62), 32639-32642.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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

Hewei Luo, Songjie Chen, Zitong Liu, Chuang Zhang, Zhengxu Cai, Xin Chen, Guanxin Zhang, Yongsheng Zhao, Silvio Decurtins, Shi-Xia Liu, Deqing Zhang,
Adv. Funct. Mater., 2014, 24(27), 4250-4258.
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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.
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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.
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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.
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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 × 10-4-1 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

Anneliese Amacher, Hewei Luo, Zitong Liu, Martin Bircher, Michele Cascella, Jürg Hauser, Silvio Decurtins, Deqing Zhang, Shi-Xia Liu,
RSC Adv., 2014, 4(6), 2873-2878.
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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.
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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.
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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

Yves Aeschi, Hui Li, Zhencai Cao, Songjie Chen, Anneliese Amacher, Nathalie Bieri, Bilal Özen, Juerg Hauser, Silvio Decurtins, Songting Tan, Shi-Xia Liu,
Org. Lett., 2013, 15(21), 5586-5589.
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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

Hui Li, Chenyi Yi, Sofiane Moussi, Shi-Xia Liu, Claude Daul, Michael Grätzel, Silvio Decurtins,
RSC Adv., 2013, 3(43), 19798-19801.
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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.
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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.
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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 {Mo22-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 antianti conformation type of tr2pr facilitates the tight zigzag chain packing motif. The crystal structure of the mixed-anion complex salt 2 consists of trinuclear [Co33-MoO4)22-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 [Co32-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 [Co32-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.
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Graphical Abstract: Dumbbell arrays: A benzodifuran (BDF) donor is for the first time fused to two C60 molecules by different linkers to form triads 13 (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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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

Wenjing Hong, Hui Li, Shi-Xia Liu, Yongchun Fu, Jianfeng Li, Veerabhadrarao Kaliginedi, Silvio Decurtins, Thomas Wandlowski,
J. Am. Chem. Soc., 2012, 134(47), 19425-19431.
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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

Jakob Grilj, Tanya Kumanova Todorova, Chenyi Yi, Shi-Xia Liu, Eric Vauthey, Silvio Decurtins,
Chem. Eur. J., 2012, 18(43), 13605-13608.
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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.
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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.
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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.
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Abstract: A tetrathiafulvalene (TTF) donor is annulated to porphyrins (P) via quinoxaline linkers to form novel symmetric P–TTF–P triads 1 ac 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 ac. 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.




Tetrathiafulvalene-based lanthanide coordination complexes: Synthesis, crystal structure, optical and electrochemical characterization

Ying-Fen Ran, Martin Steinmann, Marc Sigrist, Shi-Xia Liu, Jürg Hauser, Silvio Decurtins,
C. R. Chimie, 2012, 15(10), 838-844.
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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 {MnFe23-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.
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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 15 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 35. 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 15.




[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.
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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.
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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.
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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

Xavier Guégano, Jürg Hauser, Shi-Xia Liu, Silvio Decurtins,
Acta Cryst. E, 2011, E67(11), o2967-o2968.
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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.
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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.
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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.
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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.
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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

Ying-Fen Ran, Shi-Xia Liu, Olha Sereda, Antonia Neels, Silvio Decurtins,
Dalton Trans., 2011, 40(32), 8193-8198.
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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.
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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.
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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.
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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.
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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 {Fe43-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.
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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 {Fe43-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 {Fe43-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.
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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.
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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 (46) 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.
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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.
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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.
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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.
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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.
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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.
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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.
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Abstract: A molecular donor-acceptor dyad comprising a hexarhenium cluster core, [Re63-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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.




Three-dimensional bimetallic octacyanidometalates [MIV{(μ-CN)4MnII(H2O)2}2·4H2O]n (M = Nb, Mo, W): Synthesis, single-crystal X-ray diffraction and magnetism

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.
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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.
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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.
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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 S1  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.




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.
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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.
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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.
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(Article without Abstract)




Di-μ-acetato-μ-aqua-bis[acetatobis(1H-benzimidazole)cobalt(II)]

I. Zimmermann, T. D. Keene, A. Neels, S. Decurtins,
Acta Cryst. E, 2008, E64, m845-m846.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.




One-Dimensional μ-Chloromanganese(II)-Tetrathiafulvalene (TTF) Coordination Compound

C. Jia, S.-X. Liu, C. Ambrus, A. Neels, G. Labat, S. Decurtins,
Inorg. Chem., 2006, 45, 3152-3154.
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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, E. Levillain, S. Leutwyler, A. Hauser, S. Decurtins,
Chem. Commun., 2006, 1878-1880.
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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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