Reflectance and Raman spectra of mixed crystals of quasi-one-dimensional mixed-valence platinum complexes [ Pt3− ϱ( en) 2][ Pt3+ ϱ( Cl1− xBrx) 2( en) 2]( ClO4) 4 (0 ≦ x ≦ 1, 0 ⪡ ϱ ≦ 1)

Abstract

Mixed crystals of halogen-bridged mixed-valence platinum complexes [ Pt 3− ϱ ( en) 2][ Pt 3+ ϱ ( Cl 1− x Br x ) 2]( ClO 4) 4 (0 ≦ x ≦ 1, 0 ⪡ ϱ ≦ 1) are studied by reflectance and Raman scattering measurements. Quasi-one-dimensional charge transfer excitons in these mixed crystals are of the “amalgamation” type with large optical bowing. The energies of the phonons related to the Peierls distortion shift with composition x and their resonant Raman intensities diminish rapidly by the introduction of different halogens. These effects are discussed in terms of modulated charge density waves in one-dimensional mixed crystals.