Anisotropic exchange in transition-metal dinuclear complexes. 8. Bis(.mu.-pyridine N-oxide)bis[dichloro(dimethyl sulfoxide)copper(II)]

Single-crystal EPR spectra of bis(p-pyridine N-oxide)bis[dichloro(dimethyl sulfoxide)copper(II)], [Cu(pyO)C12(Me2SO*)], w ere recorded at room temperature at both X- and Q-band frequencies. They are typical of a triplet with g,, = 2.069 (2), gyy = 2.077 (2), g,, = 2.337 (2), Ddd = 0.0898 (6), Df f = 0.0373 ( 5 ) , and D , ,= -0.1271. The z and z'axes make an angle of 28.7 ( 5 ) O , while the x'direction makes an angle of 82.0 (2)O with the copper-copper direction. The overall appearance of the D tensor is indicative of a relevant exchange contribution, and the observed deviation of the r'axis from the z direction suggests a sizable, essentially exchange-determined DY2 component of the zero-field-splitting tensor. The polycrystalline-powder EPR spectra of the manganese(I1)-doped compound show the presence of exchange-coupled copper(I1)-manganese(I1) pairs and are characteristic of a quintet state.