Mixed Charge-Ordering State of MMX-Type Quasi-One-Dimensional Iodide-Bridged Platinum Complexes with Binary Countercations

A new charge-ordering (CO) state in quasi-1D iodide-bridged dinuclear Pt complexes (MMX-chains) was developed by introducing two different kinds of countercations. From crystal structure analysis, K2(H3NCH2CHMeCH2NH3)[Pt2(pop)4I]·4H2O (pop = P2H2O52−) had structural features of both ACP (alternating charge-polarization) and CDW (charge-density-wave) states. Therefore, this new CO state was named ACP+CDW state. Remarkably, the structure was three dimensionally ordered, which was verified by the strong superlattice reflections observed in an X-ray oscillation photograph. Using polarized Raman and 31P MAS NMR spectroscopies, it was shown that there were two different Pt2 units and four inequivalent P atoms, respectively. These results agreed with the crystal structure analysis and supported the presence of the ACP+CDW state.