Crystal structure, magnetic and spectral properties of tetrakis(2-nitrobenzoato)di(aqua)dicopper(II) dihydrate

The synthesis, characterization and structure of [Cu-2(2(..)NO(2)bz)(4)(H2O)(2)].2H(2)O are reported. The structure is centrosymmetric and the copper(II) atom has a square-pyramidal coordination by four oxygen atoms of carboxylate groups with a mean Cu-O distance of 1.964(1) Angstrom which creates a plane, and the apical position is occupied by a water molecule at a Cu-OH2 bond distance of 2.111(1) Angstrom. The electronic and infrared spectra exhibit typical features consistent with the observed structure. The EPR spectrum of a microcrystalline sample is consistent with a dimeric structure with the Hamiltonian parameters g(perpendicular to) = 2.018, g(parallel to) = 2.315, D = 0.343 and E = 0.003 cm(-1). The magnetic susceptibility measurements of a polycrystalline sample proved the dimeric structure and gives at 300 K an effective magnetic moment of 1.33 BM and at 70 K mu(eff) congruent to 0.04 BM. The magnetic susceptibility data best fitting to a Bleaney-Bowers equation gives 2J = -332 cm(-1). (C) 2004 Elsevier Ltd. All rights reserved.