Magnetism of CuwCl2•2D2O and CuCl2•2H2O, and of CuBr2•6H2O

The magnetic properties of little examined CuCl2 center dot 2D(2)O are studied and compared with those of CuCl2 center dot 2H(2)O. New CuBr2 center dot 6H(2)O is also examined. Susceptibility maxima appear for chlorides at 5.35 and 5.50 K, in the above order, with estimated antiferromagnetic ordering at 4.15 and 4.25 K. Curie-Weiss fits yield g of 2.210 and 2.205, and Weiss theta of -6.0 and -4.7 K, respectively, in chi(M) = C/(T - theta). One-dimensional Heisenberg model fits to susceptibilities, including interchain exchange in a mean-field approximation, are performed. Interchain exchange is significant but much weaker than intrachain. The bromide hexahydrate strongly differs magnetically from any chloride hydrate, but exhibits notable similarities and differences compared to previously studied CuBr2. A broad susceptibility maximum occurs near 218 K, only 4% lower than for CuBr2, but with almost twice the magnitude. Powder X-ray diffraction data for CuBr2.6H(2)O may be best accounted for by a monoclinic unit cell that is metrically orthorhombic. The volume per formula unit is consistent with trends in metal ionic radii. However, an alternative monoclinic cell with 5% smaller volume more readily rationalizes the magnetism. (C) 2017 Elsevier B.V. All rights reserved.