In [Fe(ebbtr)2(CH3CN)2](CF3SO3)2·4CH3CN spin crossover is associated with the occurrence of “normal” and “reverse” hysteresis loops separated by a region of stable HS form. This results from trans–trans → gauche–trans conformational changes of ebbtr molecules and anion reorientation, which occur in different ways during cooling and during heating.
Spin-crossover, governed by conformational changes of nitrile molecule, triggers corrugation of polymeric skeleton and formation of superstructure in [Fe(hbtz)2(allyl cyanide)2](ClO4)2.