Coordination Chemistry for Energy Conversion, Catalysis and Nanotechnology

The global energy supply and the related environmental issues are the biggest technological challenges because of the increasing world population and the legitimate aspiration of developing countries to reach higher life standards. Alternative energy supplies such as solar power are urgently needed to limit our dependence on fossil fuels. Coordination chemistry takes a central role in processes such as light-induced charge separation and light-driven generation of high-energy fuels. Energy transport and storage are further fields in which chemistry can contribute solutions. Efficiency and sustainability are key factors in modern chemical manufacturing processes. Progress in these areas requires the development of new catalytic reactions. A large fraction of these reactions make use of metal complexes. Furthermore, advances in nanotechnology, material sciences, molecular electronics and information storage will contribute to a sustainable development. Supramolecular coordination compounds such as single molecule magnets, redox-active self-assemblies and metal-functionalized DNA structures are examples for structural motifs driving the progress in these fields. The collaborative research projects within the HeKKSaGOn coordination chemistry workgroup tackle different aspects of these research areas. Some workgroup members concentrate on catalytic processes involving functionalized metal complexes. Small molecule activation and artificial photosynthetic systems are studied as well. Another subset of researchers works on the assembly and properties of supramolecular structures containing metal cations. Most contributing research groups provide expertise and instrumentation for key techniques (electrochemistry, kinetic studies, various specialized spectroscopic methods) that allow for finding answers to complex chemical questions that a single research group could hardly elucidate on its own.

In the field of homogenous catalysis, Peter Comba from Heidelberg University has teamed up with Shunichi Fukuzumi from Osaka University to study the electrochemistry of a family of non-heme iron catalysts based on a tetradentate chelate ligand. The studied bispidine-iron complexes were found to catalyze various oxidation reactions, thus allowing for the energy efficient functionalization of alkanes and alkenes. The collaboration has already lead to frequent exchanges of researchers between the two groups. Comba, P.; Fukuzumi, S.; Kotani, H.; Wunderlich, S. Angew. Chem. 2010, 49, 2622. "Electron transfer properties of an efficient nonheme iron oxidation catalyst with a tetradentate bispidine ligand".

The groups of Masahiro Yamashita from Tohoku University and Markus Enders from Heidelberg University collaborate in die field of single molecular magnets. Their joint work culminated in the combination of different NMR spectroscopic techniques including paramagnetic NMR and residual dipolar couplings to obtain structural information of Terbium(III)-Phthalocyaninato compounds in solution. The application of NMR methods in the field of single molecular magnets contributes to the promising future of theses compounds in nanotechnology, memory devices and spintronics.
Marko Damjanovic, Keiichi Katoh, Masahiro Yamashita, and Markus Enders* J. Am. Chem. Soc. 2013, 135, 14349. "Combined NMR Analysis of Huge Residual Dipolar Couplings and Pseudocontact Shifts in Terbium(III)-Phthalocyaninato Single Molecule Magnets".

In the area of supramolecular coordination chemistry, the group of Guido Clever from Göttingen University has started a fruitful collaboration with the Fukuzumi research group from Osaka University. The project studies the reversible electrochemistry of interpenetrated metal-organic cages consisting of densely packed redoxactive backbones joint through transition metal cations. It was shown that up to eight charges can be loaded on each nanoscopic architecture. These self-assembled compounds promise to find application in molecular electronics, catalysis and photovoltaics. Part of the work was carried out by a PhD student from Göttingen in the Japanese laboratory.

M. Frank, J. Hey, I. Balcioglu, Y.-S. Chen, D. Stalke, T. Suenobu, S. Fukuzumi, H. Frauendorf, G. H. Clever, Angew. Chem. Int. Ed. 2013, 52, 10102. "Assembly and Stepwise Oxidation of Interpenetrated Coordination Cages based on Phenothiazine".