DAAD-Förderung wissenschaftlicher Kooperationen mit Prof. Dr. F. J. Pina, Universidade Nova de Lisboa, Department of Chemistry, Portugal
Projektbeschreibung
In the last two decades it became apparent that transition metal complexes as organometallic compounds exhibit an enormous potential for new applications due to their photophysical and photochemical properties. For example, systems involving photo-redox processes for solar energy conversion, photovoltaic devices, molecular photodiodes or chemical synthesis, information storage systems, chemical sensors and biosensors, and supramolecular systems with user-defined photo-physical or photo-chemical properties have been explored in recent years. However, the development of new materials is limited by a lack of understanding of the nature and dynamics of the excited states, which are mainly responsible for all these properties. Only in very simple cases the nature of the excited states can be well described, but in larger systems a more profound understanding is still lacking.
One very promising approch to a deeper understanding comes from a combined effort of a more physically or spectroscopically oriented research with a more chemically or synthetically based investigation. A systematic, chemical change will lead to defined electronic variations and thus to a change of the properties of the compounds. In another approch, more subtile electronic changes can be made by substitution of a second coordination sphere around the metal complex leading thus to the formation of supercomplexes (complexes of complexes). These changes will be studied spectroscopically.
The project is intended to focus on properties of metal-organic complexes with Ru(II) as central metal ion. These systems belong to a class of highly promising compounds with respect to the applications mentioned above. The Portuguese group of Prof. Dr. F. J. Pina will prepare and access a series of Ru(II) compounds of the type [Ru(CN)₄(XX)]^2- and [Ru(NH₃)₄(XX)]²⁺ (XX = polypyrine neutral ligand) as well as positively charged macrocycles and polyazamacrocycles with negatively charged pendant arms which will bind the former ones as second coordination sphere ligands. The German group of Prof. Dr. H. Yersin will investigate these compounds with techniques of modern laser optical spectroscopy. Both groups have to come together to interpret the results and to work out plans for the subsequent experiments. It is aimed to obtain an understanding how the first and second coordination sphere of the central metal Ru(II) influences the properties of the low-lying triplet sublevels, like energies, zero-field splittings, emission lifetimes, metal-d-orbital/ligand-pi*-orbital involvements, spatially directed redistributions of electron charge densities, etc.. (Compare H. Yersin, W. Humbs, J. Strasser; Topics in Current Chemistry 191 (1997) 153)
DAAD-Förderung 1999/2000



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