Magnetic Properties and Crystal Structure of a One-Dimensional Phase of Tetrakis(<i>μ</i>₂-benzoato-<i>O</i>,<i>O</i>‘)-bis(dimethyl sulfoxide)dicopper(II)

A new crystalline polymorphic phase of tetrakis(μ2-benzoato-O,O‘)-bis(dimethyl sulfoxide)dicopper(II) was obtained by direct synthesis, in space group P21/n. The copper coordination is in a slightly distorted square pyramidal geometry with an intramolecular Cu···Cu distance of 2.6494(8) Å. The Cu−O distances of the two copper in a dimer are different, giving different chemical environments for each Cu ion. The crystal structure is built up of well-separated stacking columns oriented along the b-axis, with units uniformly spaced, producing a one-dimensional (1-D) zigzag chain through Cu(II)−S···S−Cu(II) interdimer interactions [S···S separation: 3.975(2) Å]. Magnetization measurements in the range 2−300 K indicate two magnetic orderings, at low temperature (T < 10 K) a weak ferromagnetic ordering is observed, and above this temperature an antiferromagnetic behavior takes place. ESR spectra at 300 and 77 K of a polycrystalline sample show the characteristic signal of zero-field with D = 0.354 cm-1, consistent with a ferromagnetic Cu···Cu exchange interaction at low temperature.