Diphenic Acid-Based Cobalt(II) Complexes: Trinuclear and Double-Helical Structures



The linear trinuclear complex [Co3(dpa)2(Hdpa)2(1-MeIm)2(H2O)2] (1) and the two-dimensional coordination polymer [Co2(dpa)2(pyz)]n (2; H2dpa = diphenic acid, 1-MeIm = 1-methylimidazole, pyz = pyrazine) exemplify the versatile coordination chemistry of diphenic acid in conjunction with N-donor ligands. Complex 1 consists of a discrete arrangement of three CoII atoms bridged by four diphenate ligands, whereas complex 2 contains a network of dinuclear CoII units bridged by two diphenate ligands to form double-helical chains, which are further connected via pyrazine molecules into two-dimensional sheets. A magnetochemical analysis of these complexes reveals both strong ligand field effects on the CoII4F free ion ground state and ferro- and antiferromagnetic exchange contributions mediated by the dpa ligands. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)