Spectrophotometric and Electron Spin Resonance Studies on Acetylacetonato(N,N,N',N'-Tetra-Methylethylenediamine)Copper(II) Tetraphenylborate in Various Solvents

Abstract

1 : 1 equilibrium constants for the Lewis acid-base interaction between acetylacetonato- (N, N, N', N'- tetramethylethylenediamine )copper(II) tetraphenylborate and tetrahydrofuran, pyridine, ethylacetate and N, N- dimethylformamide were obtained at 298 K in 1,2-dichloroethane by u.v .-visible spectrophotometry . The optical absorption maxima, D, of the mixed-chelate copper(II) complex in various donor solvents which decrease as the axial interaction increases were also measured and it was found that no linear correlation exists between C (cm^-l) and the solvent donor number. Isotropic hyperfine coupling constants of ^63,65Cu, A_iso, and isotropic g values, g_iso were obtained in various solvents. In general, A_iso decreases but g_iso increases as the axial interaction increases. The coefficient, α, of the d_x2-y2 orbital in the ground state molecular orbital (B1_g) was found to decrease with increasing axial interaction. The frozen solution e.s.r. spectra als ; gave α values similar to those obtained from the solution spectra. The relationship g?> g? was found in all solvents, indicating the presence of elongated tetragonal symmetry.