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

The linear trinuclear complex [Co-3(dpa)(2)(Hdpa)(2)(1-MeIM)(2)-(H2O)(2)] (1) and the two-dimensional coordination polymer [CO2(dpa)(2)(PYZ)](n) (2; H(2)dpa = diphenic acid, 1-Melm = 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 Co-II atoms bridged by four diphenate ligands, whereas complex 2 contains a network of dinuclear Co-II 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 Coll 4 F free ion ground state and ferro- and antiferromagnetic exchange contributions mediated by the dpa ligands. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)