Pt195Mössbauer Effect in the One-Dimensional ConductorK2Pt(CN)4Br0.30· 3H2O

The one-dimensional conductor ${\mathrm{K}}_2$Pt${\mathrm{}\left(\mathrm{CN}\right)\mathrm{}}_4$ ${\mathrm{Br}}_{0.30}$ · 3${\mathrm{H}}_2$O becomes an insulator at low temperatures for dc but retains its essentially metallic optical properties. In order to study the nature of the charge localization implied by the thermally activated dc conductivity we have performed ${}_{}{}^{195}{}_{}{}^{}\mathrm{Pt}$ Mössbauer experiments on the above compound. We find at 4.2 °K a single symmetrical Lorentzian absorption line. If a charge localization on an atomic scale would occur, we would expect 85% Pt(II) and 15% Pt(IV). The difference in the isomer shift between Pt(II) and Pt(IV) would cause an asymmetry in the absorption line. We thus conclude that charge is not localized on an atomic scale. The anomalously high value of ${\left|\Psi \mathrm{}\right(0\left)\right|}^2$ obtained from the isomer shift as compared to the related insulating compounds ${\mathrm{K}}_2$Pt${\mathrm{}\left(\mathrm{CN}\right)\mathrm{}}_4$ · 3${\mathrm{H}}_2$O and ${\mathrm{K}}_2$Pt${\mathrm{}\left(\mathrm{CN}\right)\mathrm{}}_4$ ${\mathrm{Br}}_2$ is a consequence of the strong metal-metal bond.