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

[EN] Low-spin, high-spin and spin-transition behaviours have been observed for the doubly interpenetrating three-dimensional bimetallic compounds {Fe-II(pz)[Ag(CN)(2)](2)}.pz (pz= pyrazine), {Fe-II(4,4'-bipy)(2)[Ag(CN)(2)](2)} (4,4'-bipy-4,4'-bipyridine), and {Fe-II-(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.
We are grateful for financial support from the European Commission, granting the TMR-Network Thermal and Optical Switching of Spin States (TOSS) , Contract No. ERB-FMRX-CT98-0199EEC/TMR. We thank the Spanish DGICYT for financial assistance through Project PB97-1397.