LONG-RANGE EXCHANGE INTERACTION IN (2,2'-BIPYRIDINE-3,3'-DICARBOXYLIC ACID)DICHLOROCOPPER(II) MONOHYDRATE VIA LATTICE WATER - SINGLE-CRYSTAL EPR STUDIES

An examination of the crystal structure of the title complex revealed three pathways for magnetic exchange. Analysis of the bulk magnetic susceptibility data in the temperature range 5303 K gave a value of J=-1.25 cm-1 for the intradimer coupling. Single-crystal EPR spectra showed anomalous angular variation from which the molecular ssg tensor was derived using a decoupling procedure. The two intermolecular couplings [J=0.0006(2) cm-1 at 300 K and 0.0001(2) cm-1 at 147 K, and J0.056 cm-1] involving multiatomic bridges were also derived from the EPR data. J involves equatorial-equatorial exchange between two coupled centers separated by 11.75 and is stronger than the axial-equatorial exchange between centers separated by 7.73. The results were analyzed on the basis of a model that assumes participation of the uncoordinated lattice water in propagating exchange interaction through H bonds. Interpretation of the molecular ssg tensor resulted in an x2-y2 ground state with very little mixing of 3z2-r2. The negligible electron density in the axial direction is responsible for the weak J. © 1990 The American Physical Society.