Influence of Pt-Cl force constants on the Raman lineshapes in (PtCl)-Cl-35/Cl-37 chains

The influence of the Cl-35/Cl-37 isotopic disorder of natural chlorine on the Raman and infrared lineshapes of the vibrational modes in PtCl chains was calculated as a function of the interionic force constants in a one-dimensional model. It is shown that the fine structure of the Raman line is strongly dependent of the Pt-3+delta-Cl and Pt-3-delta-Cl force constants, and so it can be used to estimate the charge disproportion delta. From the case of [Pt(en)(2)][Pt(en)(2)Cl-2](ClO4)(4) it appears that the description of the high-wavenumber infrared line (v(2)) requires one to take into account interactions with more distant ions. It is also shown that the intensity of the low-wavenumber infrared-active mode (v(3)) is so weak that the corresponding line may have never been observed.