Exchange Coupling in Symmetrically syn,syn-Mono(carboxylato)-Bridged Dinuclear Copper(II) Complexes.

The reaction of CuCl2·2H2O (or CuBr2) with benzoic acid and 1,4,7-trimethyl-1,4,7-triazacyclononane in CH3OH affords green crystals of [{LCuIICl}2(μ-benzoato)](ClO4) (1) or its bromo analog (2). The dinuclear mono(carboxylato)-bridged cations display weak intramolecular antiferromagnetic exchange coupling. An apparent linear magneto−structural correlation between the ratio J/n (J is the coupling constant and n is the number of syn,syn-carboxyalto bridges present) and the Cu−O−C angle α has been found.