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Triggering the Sign of Magnetic Exchange Coupling in a Dinuclear Copper(II) Complex by Solvent Molecule Coordination



The magnetic properties of a dinuclear copper(II) complex of the Schiff base ligand bis(N,N′-3-formylsalicylidene)-1,3-diaminopropan-2-ol (H3L) with an exogenous acetate bridging group, [Cu2L(CH3COO)] (2), and the product of its crystallization from dimethyl sulfoxide (DMSO) solution, [Cu2L(CH3COO)(DMSO)] (3), are studied experimentally and theoretically. The coordination of a DMSO molecule triggers exchange coupling from antiferromagnetic in 2 (2J = –94.8 cm–1) to ferromagnetic in 3 (2J = +121 cm–1). A combination of experimental data [XRD, X-ray absorption spectroscopy (XAS)] and the results of DFT calculations with a broken-symmetry approach show that the different magnetic behaviour of 2 and 3 is explained by a different conformation of the dinuclear unit, which is “symmetric” in 2 and roof-shaped in 3. The role of the DMSO molecule in exchange-coupling sign inversion is limited to the stabilisation of the roof-shaped conformation of the complex.