Charge-transfer spectra of post-transition-metal halide complexes

Abstract

U.v. spectra of tetrahedral Group IIIB [Et₄N][MX₄](M = Ga or In; X = Cl, Br, or I), octahedral [Et₄N]₂[SnX₆], and tetrahedral SnX₄ complexes have been measured in solution at room temperature, and of [HgI₄]^2– doped in a crystal of [NEt₄]₂[ZnI₄] at 300 to 4 K. The temperature variation of the half-width of the absorption band in the latter leads to an estimate of 0·21 Å for the expansion of the molecule in the excited state. The excitation is broadened by interaction with the totally symmetric stretching mode. Using results obtained in this and a previous paper, energies of the baricentres of the first halogen (p_π)→metal(s) configurations are correlated for a wide range of B-subgroup elements, with respect to changing halogen, metal, and symmetry of the complex.