Structures and magnetic properties of imidazolate-bridged tetranuclear and polymeric copper(II) complexes

Abstract

Eight kinds of imidazolate-bridged copper(II) complexes were found to be classified into two categories from the magnetic properties. The crystal structures of [Cu(L)(μ-im)] n (Him = imidazole; L = nonane-4,6-dionate, 2,6-dimethylheptane-3,5-dionate) and [Cu(L)(μ-im)] 4 (L = nonane-4,6-dionate, 1-phenylbutane-1,3-dionate) were determined, to reveal that they consist of polymeric chains and tetranuclear cycles, respectively. Note that the nonane-4,6-dionate derivative gave the two phases. The Bonner–Fisher model (a one-dimensional antiferromagnetic chain model) was plausibly applied to [Cu(L)(μ-im)] n for the best fit, while a square model was to [Cu(L)(μ-im)] 4. The complexes with unknown crystal structures were also subjected to magnetic measurements, and the tetra- and polymeric structures could be clearly distinguished from each other by fitting the magnetic data to appropriate models. The exchange parameters were comparable for both series (2 J/ k B = −78 to −97 K) because the structurally common bridges Cu–N(eq)–N(eq)–Cu afford comparable magnitudes of couplings.