Electronic and vibrational spectra of mixed-valence complexes with a metal--halide chain

The electronic and vibrational spectra of compounds with a M(II)---X—M(IV) (where M = Pt, Pd, Ni and X = Cl,Br,I) chain are briefly reviewed and some new results reported. Emphasis is given on the size effects. The interpretation of the optical absorption spectra is based on the assumption that the gap energy increases as the size of the particles decreases. A red shift predicted for the resonance Raman excitation profiles is in agreement with the experiments.