Solvent Effects on the Structural Packing and Spin-Crossover Properties of a Mononuclear Iron(II) Complex

Solvent molecules are known to have a remarkable effect on the crystal structures and magnetic properties of spin-crossover (SCO) compounds. On the basis of our previous works on this topic, we have synthesized a series of SCO Fe(II) compounds, [Fe(tpa)(NCSe)(2)]center dot Soly (tpa = tris(2-pyridylmethyl)amine; Solv = 0.5CH(3)OH for 1 center dot CH3OH, 0.5C(2)H(5)OH for 1 center dot C2H5OH, 0.25H(2)O for 1 center dot H2O, 0.5CH(3)CN for 1 center dot CH3CN-A, CH3CN for 1 center dot CH3CN-B, and CH2Cl2 for 1 center dot CH2Cl2), by crystallization of the molecular complex [Fe(tpa)(NCSe)(2)] from the respective solvents. Single crystal X-ray crystallographic studies show that the molecular packing structures and intermolecular interactions of these compounds are subtly changed by the lattice solvent molecules; thus, their SCO properties can be differentiated from each other. All of the solvated compounds undergo onestep SCO behavior with the order of critical temperatures being T-c(1 center dot CH3CN-B) < T-c(1 center dot CH2Cl2) < T-c(1 center dot CH3CN-A) < T-c(1 center dot C2H5OH) approximate to T-c(1 center dot CH3OH) < T-c(1 center dot H2O), of which thermal hysteresis loops of 3 K width (T-c up arrow = 255 K and T-c down arrow = 252 K) and 10 K width (T-c up arrow = 256 K and T-c down arrow = 246 K) are observed for 1 center dot CH3CN-B and 1 center dot CH2Cl2, respectively.