Copper compounds

Electronic-structure studies of Tetrakis(imidazole)sulphatocopper(II) - Cu(C3H4N2)4SO4 and Tetrakis(imidazole)diperchloratocopper(II) - Cu(C3H4N 2)4(ClO4)2 have been carried out by analysis of electronic spectra, magnetic properties and ESR spectra. Solution spectra of both systems in the visible and UV range as well as unpolarised single-crystal spectrum of Cu(Im)4SO4 in the visible have been recorded. Both ligand-field (LF) and charge-transfer (L --> M) bands have been identified and assigned, with the exception of the lowest energy LF band. The Angular Overlap Model has been used to calculate the LF band-maxima and compare with the observed band-maxima The ground-state energy-term for both Cu(Im)4SO4 and Cu(Im)4(ClO4)2 has been established with the use of ESR data to be 2B1g. Magnetic moment for the complexes have been obtained from precise magnetic susceptibility measurements with temperature variation and satisfactorily compared with the calculated values.

The electronic spectrum of Cu(II)(L-His)2 has been measured in the visible-near IR and UV regions. By assigning ligand field bands and by fitting the band maxima with calculated energies using angular overlap model, the structure of the complex has been deduced to be five-coordinate C4v1 The observed bands in the UV spectrum have been assigned as due to ligand-to-metal charge transfer transitions. Electronic spectra of Cu(II)(diphenylcarbazide)2 and Cr(II)(diphenylcarbazone)(H2O)4 complexes have also been measured. By interpretation of the ligand field bands in these spectra, tentative structures of these complexes in solution have been proposed.