Tuning of electronic structures of quasi one-dimensional iodide-bridged dinuclear platinum mixed-valence complexes

This review describes the tuning of electronic structures and variable phase transitions in quasi one-dimensional iodide-bridged dinuclear Pt compounds (MMX chains). These are classified into two types of MMX chain compounds, that is, Pt2(dta)4I (dta = dithioacetate derivatives) and R4[Pt2(pop)4I]·nH2O (R = alkylammonium, etc.; pop = P2O5H22−). These MMX chains compounds can take four electronic structures such as average valence (AV), charge-density-wave (CDW), charge-polarization (CP) and alternating charge-polarization (ACP) states. The Pt2(dta)4I compounds show a phase transition from metallic AV, CP, to ACP state with decreasing temperature. The phase transition feature depends on the alkyl derivatives of the dta ligands. The R4[Pt2(pop)4I]·nH2O exhibits three oxidation states, AV, CDW, and CP states, depending on the kind of cations. Some of these compounds show a phase transition by pressure, photo-irradiation, temperature, and humidity.