ELECTRONIC-SPECTRA AND PHOTOCHEMISTRY OF TIN(II), LEAD(II), ANTIMONY(III), AND BISMUTH(III) BROMIDE COMPLEXES IN SOLUTION

The electronic spectra of bromo complexes of main group metal ions with an s2 electronic configuration (SnBr3-, PbBr3-, PbBr42-, SbBr4-, SbBr63-, BiBr4-, BiBr63-) 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.