The main focus of our research
lies in redox-active π-conjugated metal-organic molecules where the
metal atoms constitute an integral part of the delocalized π-system and
endow it with low oxidation potentials, increased stabilities of the
oxidized forms and intense electronic absorptions in the visible
regime. In particular, we have investigated allenylidene complexes
[Cl(L2)Ru=C=C=C(ERn)R’]+ (L2 = bidentate diphosphine ligand) and vinyl
complexes [(CO)Cl(PR3)2LM(CH=CHR’)] (M = Ru, Os; L = neutral donor
ligand). Details of this research can be found in the appropriate
documents of this page.
Apart from the routine spectroscopic and, if possible, crystallographic
characterization methods we also employ various electrochemical
techniques in order to investigate the electron transfer properties of
the redox-active metal-organic π-conjugated molecules. We routinely
generate and spectroscopically characterize the associated oxidized or
reduced forms by means of IR, UV/Vis/NIR and ESR spectroscopy. This
provides us with detailed insight into the composition of the
“redox-orbitals” that are involved in the electron transfer events.
Accompanying quantum chemical calculations help us to put our
experimental results into context and to arrive at a deeper
understanding of the bonding in the delocalized metal-organic π-systems.
Based on allenylidene and vinyl complexes we are presently exploring
• molecule-based electrically
• photoaddressable switches
• electrochromic materials and redox-responsive dyes
• electron transfer across multiple hydrogen bridges
• electron transfer paths in cross-conjugated π-systems
• mixed-valency in ferrocene-heterometal conjugates
Our group, albeit small, is involved in various national and
international collaborations, where we rely on the expertise of other
groups for investigations on our systems, perform electrochemical
and/or spectroelectrochemical investigations on samples from other
groups or work on common research programs. Our present collaboration
• Dr. Biprajit Sarkar and Prof.
Dr. Wolfgang Kaim, University of Stuttgart (ESR-spectroscopy)
• Dr. Stanislav Záli¨, J. Heyrovský Institute of Physical Chemistry v.
v. i. of the Czech Academy of Sciences, Prague (quantum chemical
• Prof. Dr. Hans-Jörg Krüger, University of Kaiserslautern (Mößbauer
• Prof. Dr. Bernhard Dick, University of Regensburg (Laser excitation
and molecular spectroscopy)
• Prof. Dr. Helmut Fischer, University of Konstanz; Priv. Doz. Katja
Heinze, University of Heidelberg; Prof. Dr. Heinrich Lang, University
of Chemitz; Prof. Dr. Sabine Laschat, University of Stuttgart; Prof.
Dr. Franc Meyer, University of Göttingen; Prof. Dr. Oliver Reiser,
University of Regensburg; Prof. Dr. Manfred Scheer, University of
Regensburg; Prof. Dr. Uli Siemeling, University of Kassel; Prof. Dr.
Matthias Wagner, University of Frankfurt (spectroelectrochemical
• Dr. Jean-Luc Fillaut, Dr. Olivier Lavastre, Université de Rennes
(ferrocenyl/heterometal conjugates and enynyl bridged homo- and
• Dr. Konrad Kowalski, University of Łodz (azaferrocenes and
• Prof. Dr. Michael Knorr, University of Besançon (paracyclophane