SPECTROCHEMICAL STUDIES OF COMPLEXES OF COPPER (II) WITH ETHYLENEDIAMINE AND AMMONIA.

Author Institution: Department of Chemistry and Chemical Engineering, University of IllinoisRecent studies of the electronic absorption spectra of copper (II) ethylenediamine and copper (II) ammine complexes in both solutions and crystals are reported. In light of the various transition energies and intensities, the question of the coordination number and stereochemistry of copper (II) complexes in solution is discussed. Notably, a comparison of the ethylenediamine solution spectrum of Cu $en_{3}^{2+}$ with the crystal spectrum of trigonal Cu $en_{3}^{2+}$ (undistorted by Jahn-Teller forces) confirms the idea that the solution species is five-coordinate. An assignment of the visible bands of crystalline bis-(ethylenediamine)-copper (II) complexes is proposed on the basis of a molecular orbital calculation and experimental polarization data. For the crystal spectra of tetrammine compounds, the intensity is vibronic and essentially unaffected by axial substituents