The electroreflectance spectra of the halogen-bridged mixed-valence Pt complexes, [Pt(ethylenediamine)2][Pt(ethylenediamine)2X2](ClO4)4 (X=Cl, Br, and I), have been measured. Electric-field-induced new absorption bands that can be assigned to optically forbidden charge-transfer (CT) excitons with even parity have been found at a little higher energy than the optically allowed CT excitons with odd parity. The modulation mechanism can be quantitatively explained by the electric-field-induced mixing between the odd and the even CT excitons. The energy separations between the odd and the even excitons of the X=Cl, Br, and I complexes are 0.54, 0.46, and 0.24 eV, respectively. This indicates the large electron-hole attractive energies in the complexes. The halogen-dependent change of the energy separations can be explained in terms of the intersite electron transfer energies.
ASJC Scopus subject areas
- Condensed Matter Physics