Photo-Induced Absorption Band in One-Dimensional Halogen-Bridged Mixed-Valence Platinum Complex: [Pt(en)2][PtI2(en)2](SO4)2·6H2O and its Au-Doped Complex: [AuxPt1-xI(en)2]SO4·3H2O

Abstract

The intervalence charge-transfer absorption spectra in the mixed-valence complexes [Pt(en) 2 ][PtI 2 (en) 2 ](SO 4 ) 2 ·6H 2 O and [Au x Pt 1- x I(en) 2 ]SO 4 ·3H 2 O ( x =0.03) have been investigated at 4.2 K. In these complexes, below the charge-transfer absorption edge, a weak absorption band ( A -band) has been observed for the light polarized parallel to the chain axis. When these complexes were irradiated with the light in the region of the charge-transfer transition from Pt II to Pt IV , the absorption coefficient of the A -band increased remarkably, which implies that the A -band is a photo-induced absorption band. The photo-induced effect for the A -band in [Au x Pt 1- x I(en) 2 ]SO 4 ·3H 2 O ( x =0.03) is more intense than that in [Pt(en) 2 ][PtI 2 (en) 2 ](SO 4 ) 2 ·6H 2 O. The A -band suggests the existence of new excitations such as a soliton-like excitation in the electronic state of the platinum chains.