Synthesis and structural and magnetic characterization of discrete phenolate and imidazolate bridged Gd(III)-M(II) [M = Cu, Ni] dinuclear complexes

Three dinuclear complexes formed by the reaction of Gd(hfa)(3) (hfa is hexafluoroacetylacetonate) with Schiff base complexes of Cu(II) and Ni(II) have been synthesized and characterized. The crystal structures of the complexes [Gd(hfa)(3)M(prpen)] {M = Cu(II (1)), Ni(II) (2)} are reported. (H(2)prpen is the Schiff base derived from the condensation of 2 equiv. of 2-hydroxypropiophenone and 1 equiv. of ethylenediamine.) Both 1 and 2 are discrete dinuclear complexes consisting of an eight coordinate Cd atom which is bridged to four coordinate M(II) via both phenolate oxygen atoms of the prpen ligand. The crystal structure shows there is no tendency toward dimerization between adjacent Cu(II) Schiff base units in 1. Cryomagnetic measurements show a ferromagnetic interaction between Gd(III) and Cu(II) in 1 as predicted by theory with J = 1.91 cm (- 1). The reaction of Gd(hfa), with Ni(L) (H2L is the Schiff base derived from the condensation of 1 equiv. each of 5-chlorobenzophenone, 1,2-diaminobenzene, and 5-methyl-4-imidazolecarboxaldehyde) produced Gd(hfa),Ni(L) (3) in which imidazolate is available to bridge Gd(III) and Ni(II). (C) 2001 Elsevier Science B.V. All rights reserved.