Photo-Induced Defect States in a Quasi One-Dimensional Mixed-Valence Platinum Complex

Abstract

Photo-induced absorption effects have been investigated in [Pt(en) 2 ][Pt(en) 2 Cl 2 ] (ClO 4 ) 4 single crystals. When the crystals are irradiated at 77 K by the light within the charge-transfer absorption band (CT band) or higher, two absorption bands (A and B) are observed below the CT band. Their intensities increase linearly with the total excitation light flux at low excitation level. The photo-induced absorption bands are stable at 77 K, but are not observed at room temperature. The A and B bands are induced only by the light with E // chain and preferencially polarized for E // chain, suggesting that the photo-induced defect states are located on individual chains, and not associated with interchain defects. The results are discussed in terms of the photo-induced polaron and kink-soliton models.