Thermal-, Pressure-, and Light-Induced Spin Transition in Novel Cyanide-Bridged FeIIbAgI Bimetallic Compounds with Three-Dimensional Interpenetrating Double Structures {FeIILx[Ag(CN)2]2}⋅G

Low-spin, high-spin and spin-transition behaviours have been observed for the doubly interpenetrating three-dimensional bimetallic compounds (FeII(pz)[Ag(CN)2]2).pz (pz = pyrazine), (FeII(4,4'-bipy)2[Ag(CN)2]2) (4,4'-bipy = 4,4'-bipyridine), and (FeII(bpe)2[Ag(CN)2]2) (bpe = bispyridylethylene), respectively. The single crystals of the bpe derivative undergo a spin transition with a large hysteresis loop at about 95 K. After several warming and cooling cycles, the single crystals become a microcrystalline powder with 50% spin transition. Influence of pressure--as well as light-induced excited spin-state trapping (LIESST) on the thermal 50% spin transition of the microcrystalline sample has also been investigated. Thermal spin-transition behaviour has also been induced at pressures higher than 1 bar for the 4,4'-bipy derivative. Both the 4,4'-bipy and bpe derivatives show strong pressure dependence of the spin state at 300 K.