Novel optical and magnetic bistability and photoinduced transition in a one-dimensional halogen-bridged binuclear Pt complex

In iodine-bridged binuclear Pt compounds, R 4 [Pt 2 (pop) 4 I]nH 2 O and R' 2 [Pt 2 (pop) 4 I]nH 2 O (pop = P 2 O 5 H 2 - 2 ), electronic structures on the PtPtI chains have been controlled between a diamagnetic charge-density-wave (CDW) state and a paramagnetic charge-polarization (CP) state by modification of the counterions (R, R') located between chains. In the R = (C 2 H 5 ) 2 NH + 2 compound, a pressure-induced CP to CDW transition with a drastic color change is identified. This transition is accompanied by a large hysteresis loop within which photoinduced transition between CDW and CP can be driven by selecting the excitation photon energy.