Evidence for Large Antisymmetric Superexchange in Tetrameric Copper Complexes

Transition metal cluster complexes often combine high local symmetry about individual magnetic ions with low spin-pair symmetry. These complexes should therefore enrich greatly the field of study of highly anisotropic, particularly asymmetric, exchange phenomena of low order. We illustrate by presenting evidence indicating strongly that the tetrameric copper complex Cu₄OCl₆[OP(C₆H₅)₃]₄ provides the first example in the literature of large (lowest-order) antisymmetric superexchange between orbitally degenerate magnetic ions.