The reaction of a tripodal ligand (H2L = N,N-bis(2-hydroxybenzyl)-N′,N′-dimethylethylenediamine) with (Cu(NO3)2·3H2O and Cu(ClO4)2·6H2O in methanol yielded [Cu2(HL)2](NO3)2·H 2O (1) and [Cu2(HL)2](ClO4)2 (1′), respectively. When H2L was allowed to react with CuSO4·5H2O in the presence of triethylamine (1:1:2) in methanol, the neutral dicopper(II,II) complex [Cu2(L)2] (2) was obtained. The monopositive species [Cu2(L)(HL)]ClO4·CH3OH·H 2O (3) crystallized on mixing 1′ and 2(1:1) in methanol-dichloromethane. The crystal structures of 1,2, and 3 were determined by X-ray crystallography. All of the complexes consist of a discrete dinuclear molecule with bis(μ-phenoxide)-bridges. The tripodal ligand functions as a tetradentate ligand and one of the phenolic oxygen atoms serves as a bridging ligand. Protonation/deprotonation takes place at the terminal phenol moiety and as the phenol group is deprotonated the coordination geometry changes from a distorted square pyramid to a distorted trigonal bipyramid. The two copper ions in 1-3 are antiferromagnetically coupled with 2J = -714 (1), -19.9 (2), -277 cm-1 (3). The results clearly demonstrate that protonation/deprotonation causes a change in coordination geometry, which in turn drastically affects magnetic exchange interactions.
|Number of pages||6|
|Journal||Journal of the Chemical Society, Dalton Transactions|
|Publication status||Published - Oct 29 2002|
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