Spin-crossover systems with multifunctional behavior based on intermolecular interactions

Abstract

Spin-crossover (SCO) complexes featuring Fe(II), Fe(III), or Co(II) centers exhibit bistable magnetic and electronic states that can be reversibly switched by external stimuli, such as temperature, pressure, or light. This review highlights the decisive role of intermolecular interactions; hydrogen bonding, π–π stacking, van der Waals forces, and host–guest effects, in modulating cooperativity, hysteresis width, and multifunctional behavior in SCO materials. Particular attention is paid to Fe(III) systems that exhibit light-induced excited spin-state trapping and Co(II) systems showing reverse spin transitions. Additionally, the concept of pseudo-pressure effects in graphene oxide composites is presented as a strategy to control spin states without external compression. These insights demonstrate how supramolecular engineering enables the rational design of multifunctional and responsive spin materials.