Electronic Spectra and Photochemistry of Tin(II), Lead(II), Antimony(III), and Bismuth(III) Bromide Complexes in Solution

Abstract

The electronic spectra of bromo complexes of main group metal ions with an s2 electronic configuration (SnBr3 -, PbBr3 -, PbBr4 2-, SbBr4 -, SbBr6 3-, BiBr4 -, BiBr6 3-) in acetonitrile show long-wavelength absorption bands which are assigned to metal-centered sp transitions. Compared to the corresponding chloro complexes the sp bands of the bromo complexes appear at longer wavelength due to sp/LMCT mixing (LMCT = ligand-to-metal charge transfer). As a result of this mixing the luminescence which originates from low-energy sp excited states is much weaker than that of the chloro complexes. Moreover, some of the bromo complexes (e.g. BiBr4-) undergo a photochemical redox decomposition induced by LMCT excitation.