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

Abstract

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]·Solv (tpa = tris(2-pyridylmethyl)amine; Solv = 0.5CH3OH for 1·CH3OH, 0.5C2H5OH for 1·C2H5OH, 0.25H2O for 1·H2O, 0.5CH3CN for 1·CH3CN-A, CH3CN for 1·CH3CN-B, and CH2Cl2 for 1·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 one-step SCO behavior with the order of critical temperatures being Tc(1·CH3CN-B) < Tc(1·CH2Cl2) < Tc(1·CH3CN-A) < Tc(1·C2H5OH) ≈ Tc(1·CH3OH) < Tc(1·H2O), of which thermal hysteresis loop...