2-Chloro-3-fluoropyridine copper(II) complexes and the effect of structural changes on magnetic behavior

Abstract

A family of copper(II) compounds has been prepared with the general formula (2-chloro-3-fluoro-pyridine)2CuX2·n(Y), where X = Cl, Br, n = 0,1, and Y = methanol or water. For the copper chloride complexes, only solvated structures were obtained (1, X = Cl, Y = H2O; 2, X = Cl, Y = CH3OH) while for the copper bromide compounds, both a desolvated structure and the methanol solvate were prepared (3, X = Br, Y = none; 4, X = Br, Y = CH3OH). Each compound has been characterized by IR, powder X-ray diffraction, single-crystal X-ray diffraction, and temperature-dependent magnetic susceptibility measurement. Compounds 1 and 4 are isostructural, in the space group Cm, and neither exhibits significant magnetic exchange although superexchange pathways are present. Compound 2 also crystallizes in the Cm space group and exhibits weak ferromagnetic interactions (J/kB = 1.72(2) K from the 1D-ferromagnetic chain model) which are likely propagated by hydrogen bonding. Compound 3 crystallizes in the space group P21/n with the Cu(II) ion sitting on a crystallographic inversion center. Compound 3 exhibits weak antiferromagnetic exchange via two-halide superexchange typical for similar complexes. The magnetic data for 3 were fit to the 1D-antiferromagnetic chain model resulting in J/kB = −1.21(1).