The isotropic hyperfine interaction in ternary complexes of copper(II) with 8-hydroxyquinoline and various salicylic acids

Electron spin resonance and optical absorption studies are carried out on bis(8-hydroxyquinolinato)copper(II) and seven ternary copper(II) complexes with 8-hydroxyquinoline and salicylic acid or substituted salicylic acids. Electron spin resonance spectra of all these complexes give well-resolved lines. An unusual splitting of the parallel lines in frozen solution spectra and four line fluid (DMF) solution spectra at room temperature are observed. It is explained on the basis of either partial dissociation of 8-hydroxyquinoline ligand or the solvation effect of DMF which solvates some copper chelate molecules even at room temperature. This is more prominent on the parallel lines in frozen solution spectra of all the ternary complexes. The molecular orbital coefficients are estimated assuming an axial symmetry and these indicate that the in-plane π bonding is weak compared to σ-bond in the ternary complexes. The value of χ, which is proportional to hyperfine constants, indicates that it is quite independent of either ligand substitutions or substitutions in the ligand, but purely depends upon the immediate environment which constitutes the coordination around the paramagnetic ion.