A New Interpretation of the Anomalous Magnetic and Optical Behavior of Copper Acetate Monohydrate

Abstract

Interpretation of the extensive magnetic and optical measurements of copper acetate monohydrate on the basis of a C4v symmetry of the complex by different workers are, to some extent, incomplete and often lead to contradictions. Starting with the electronic states of each half of the complex, assumed to have a C2v symmetry as shown by ESR. data, we find that the bonding between the two halves is a mixture of σ- and δ-type as against a pure σ or δ bonding for a C4v symmetry. Operation of H=Hex+HLS+βH(L+2S) on the valence bond states of the whole complex by usual perturbation technique then gives us the expressions for the singlet-triplet separation (J), the spectroscopic splitting factors and the magnetic susceptibilities. It is found that the last two quantities and the optical absorption data can be correlated to a good extent and the ligand field parameters obtained in the process yield a value of − 138 cm−1 for J, which is fair enough under the approximations employed. In this calculation we have found it necessary to consider the dimeric band at 28 000 cm−1 to be a Laporte forbidden type under a strong anisotropic ligand field.