Theoretical and Experimental Evidence for a New Kind of Spin-Coupled Singlet Species:Isomeric Mixed-Valent Complexes Bridged by a Radical Anion Ligand

摘要

Singlet species composed from clearly identified odd-electron components have long been known in the form of antiferro-magnetically spin-spin coupled transition-metal centers (M) of d~(2n+1) configuration bridged by ligands mu-L,giving rise to the phenomenon of "superexchange" in (M~(centre dot))(mu-L)(M~(centre dot)) species.More recently,the reverse situation (L~(centre dot))(M)(L~(centre dot)) with a bridging diamagnetic metal center was described and referred to in terms of "singlet diradical" species.