Exchange coupling in organometallic metal-centered oligoradicals: a comprehensive study of mediating spacers

• Applicant: Professor Dr. Christoph Elschenbroich
• Subject Area: Inorganic Molecular Chemistry - Synthesis and Characterisation
• Term: from 2002 to 2010
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 5368756

Cooperative magnetic behavior has traditionally been studied on inorganic solids bearing para-magnetic sites, Werner-type coordination compounds of open-shell central metal ions, charge transfer radical salts and organic oligoradicals. Despite the fact that one of the most spectacular findings, the room-temperature ferromagnetism of the product from the reaction of di(ben-zene)vanadium with tetracyanoethylene utilized an organometallic compound, the impact of organometallics on molecular magnetism has as yet been very limited. We propose to synthesize an extensive series of new di- and oligonuclear organometallic compounds in which paramagnetic (tropylium)vanadium(cyclopentadienyl) units are separated by spacers containing elements of the groups 13, 14, 15 and 16. One-atom bridges including heteroatoms, sp3 and sp2 hybridized carbon as well as alkene, alkyne and phenylene units will be introduced. Heteronuclear spacers will feature BHB and AlRAl 2e3c bridges, S-M-S (thiolate) and carboxylate units. Principal tool in the study of exchange coupling will be EPR spectroscopy in fluid solution since intermolecular exchange will then be eliminated and very weak long-distance intramolecular interactions become detectable. It is hoped that after completing the program a data base will exist which describes the capacity of a large variety of bridging units to mediate electron exchange coupling and which may serve in predictions of molecular magnetic behavior.

• DFG Programme: Research Grants