Magneto-Structural Correlations of Dimeric Copper(ll) Trichioroacetates

Sixteen crystal structures of dimeric copper(II) trichloroacetates, (I)-(XVI), have been determined by single-crystal X-ray diffraction. In crystals of the compounds which have small -2J values, less than 200 cm- 1, the coordination geometry around the Cu atom is deformed from square pyramidal (SP) to trigonal bipyramidal (TBP), and the Cu...Cu interatomic distance is elongated. The longer the Cu.--Cu distance, the smaller the -2J value, indicating that the spin super exchange interaction is weaker in the TBP than in the SP structure. The magnetic orbitals in the TBP structure may consist mainly of copper dz, orbitals (z along the axial direction of the TBP), which are perpendicular to each other at the two Cu atoms, and overlap only slightly with each other on * To whom correspondence should be addressed.