Anisotropic exchange in dinuclear complexes with polyatomic bridges. Crystal and molecular structure and EPR spectra of (m-oxalato)-bis-(1,10 phenantroline) dicopper (II) dinitrate

The X-ray crystal structure of (oxalato)bis(l,lO-phenanthroline)dicopper(II) dinitrate was determined at room temperature.The crystals are triclinic, space group Pi, with a = 9.977 (6) A, b = 9.658 (6) A, c = 7.036 (3) A, (Y = 108.03 (4)O, 0 = 95.40(4)'. y = 90.22 (4)O, and Z = 2. The least-squares refinement of the structure led to a conventional R factor of 0.036.Single-crystal EPR spectra were recorded at X-band (9-GHz) frequency at 77 K. The measured zero-field splitting tensor wasfound to be largely misaligned from the g tensor, showing that exchange contributions to the anisotropic spinspin interactionare operative. The relative influences of the dipolar magnetic and the anisotropic exchange interactions in determining the zero-field splitting in oxalato-bridged copper(I1) dimers are discussed.