X-Ray Crystal Structure and Cu2+ Doped EPR Studies of Tetraaquabis(Isonicotinamide)Zinc and -Cobalt(II) Disaccharinate 1.5 Hydrate Single Crystals

Abstract

Crystal structure of [M(ina)<inf>2</inf>(H<inf>2</inf>O)<inf>4</inf>](sac)<inf>2</inf>1.5H <inf>2</inf>O (M=Zn2+(1), Co2+(2); ina for isonicotinamide or pyridine-4-carboxyamide and sac for saccharine) complexes have been determined by X-ray diffraction analyses and their magnetic environments have been identified by electron paramagnetic resonance (EPR). The isostructural complexes of 1 and 2 both crystallize in the monoclinic system. In both complexes, the octahedral metal atom, which rides on a crystallographic center of symmetry, is coordinated by two monodentate isonicotinamide ligands through the ring nitrogens and four aqua ligands to form a discrete [M(ina)<inf>2</inf>(H<inf>2</inf>O)<inf>4</inf>]2+ unit, which captures up and down two saccharinate ions, each through intermolecular hydrogen bonds. The EPR analyses of Cu2+ doped 1 and 2 single crystals indicate that there is one magnetic centre with two magnetically inequivalent sites for the paramagnetic Cu2+ ion in 1, whereas two magnetic centres with each having two magnetically inequivalent sites are observed in 2. The spin Hamiltonian parameters together with the molecular orbital coefficients for each crystal of 1 and 2 were derived from the EPR spectra and these were used to construct the ground state wave function of Cu2+ ion in each crystal. © 2005 Elsevier B.V. All rights reserved.