Excitation wavenumber dependence of the symmetric chain-stretching mode of linear-chain mixed-valence platinum complexes

Abstract

The wavenumber, ν1, of the symmetric chain-stretching mode of linear-chain halogen(X)-bridged mixed-valence complexes of platinum increases as the wavenumber of the excitation line (ν0) increases, whereas those of equatorial modes do not. For any set of complexes the wavenumber change, ν1(λ0= short wavelength)–ν1(λ0= long wavelength), increases in the order Cl < Br < I and is largest for those complexes in which the PtII⋯ PtIV separation is least and for which the bond-length ratio r(PtIV–X)/r(PtII–X) is nearest to unity. This suggests that the wavenumber dispersion of v1 with v0 depends on the extent of valence delocalisation along the chain.