Electronic Absorption Spectrum and Structure of CuCl4=

Polarized crystal-absorption spectra in the near-infrared, visible, and ultraviolet regions are reported for Cs2CuCl4. The near-infrared bands are analyzed on the basis of the known structure of the CuCl4= ion with D2d symmetry. The positions and polarizations of the bands are accounted for and the minor effcets of spin—orbit coupling and the true-site symmetry (Cs) are discussed. The observations agree very well with the theoretical calculations of Lohr and Lipscomb and differ from the pure electrostatic crystal-field theory. An analysis of the electron-transfer bands has been made. It is concluded that the CuCl4= ion in solution has a structure which is close to that found in the crystal of Cs2CuCl4.