Oligonuclear carboxylate-brigded transition metal complexes as a) heteronuclear coordination compounds, b) coordination compounds with redox non-innocent ligands, c) complexes with additional organometallic capping groups

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Molecular species containing more than one metal ion offer the possibility of co-operative behavior between the metal centers, which may lead to new properties and reactivity. Nature utilizes such co-operative properties in enzymes that catalyze several different processes, but moreover oligonuclear metal complexes are of fundamental interest in the field of molecule-based magnets, with the most thoroughly investigated examples of single molecule magnets being oxo- and hydroxo-bridged polymetallic systems. The systematic variation of the electronic properties by means of varying the spin system will be studied spectroscopically and magnetically in order to establish magneto-structural relationships for heterometallic compounds or metal complexes with additional spin carrying organic units. In the project we will prepare new coordination compounds starting from well-known transition metal clusters as building blocks using new synthetic strategies. Heteropolynuclear complexes and compounds bearing redox-active ligands will be obtained and studied in detail by X-ray crystallography, spectroscopic methods like Mössbauer and UV-Vis as well as magnetic susceptibility measurements. Successful performance of this research will provide a profound understanding of synthetic strategies to new homo- and heteropolymetallic compounds including various spin centers. Our long-standing interest and experience in the study of magneto-structural correlations in polynuclear iron systems with basic carboxylate groups provides us with the basis to successfully carry out the project on ordered multidimensional spin arrays.