129I Mössbauer Spectroscopic Study in a MMX-Chain System, M2(dta)4I (M = Ni, Pt, dta = CH3CS2−)

The title Pt compound is a highly-conductive mixed-valence MMX-chain system. It exhibits a metal-semiconductor transition at 300 K, which is attributed to a valence transition of Pt from an average-valence state of +2.5 to a trapped-valence state of +2 and +3. From 129I Mِssbauer spectroscopic study, the 1-D structural mode was strongly suggested to be a -PtII-PtIII-I-PtIII-PtII-I-PtII-PtIII-I-PtIII-PtII-- charge ordering state at 16 K. The charge-ordering mixed-valence state is discussed, as well as the valence state of the Ni compound, which is considered to be an averaged-valence Mott insulator.