Multistep Changes in Spin‐Crossover Temperature Induced by Stepwise Desolvations

Lattice solvents significantly influence spin‐crossover (SCO) behavior, while multistep changes induced by stepwise desolvations are rarely reported. Herein, we report a novel Fe(II) SCO complex, [Fe(H 2 L) 2 ](BF 4 ) 2 ·3VN ( 1·3VN , H 2 L = 2,6‐bis(5‐phenyl‐1 H ‐pyrazol‐3‐yl)pyridine, VN = valeronitrile), shows non‐monotonic changes in spin transition temperature ( T 1/2 ) upon stepwise desolvation of VN molecules. A conversion from 1·3VN to 1·2VN increases T 1/2 and slightly enhances hysteresis. In contrast, further desolvated 1·VN shows partial SCO with significantly decreased T 1/2 and enhanced hysteresis. Structural investigations revealed that the multistep changes in T 1/2 values can be explained by significant alterations of the intermolecular interactions between VN molecules and 1 .