Knowledge Bank

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 effects of spin-orbit coupling and the true site symmetry $(Ca)$ are discussed. The observations agree very well with the theoretical calculations of Lohr and $Lipscomb1$ 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 $Cs2CuCl4$.