Leveraging supramolecular design towards spin-state control.

Spin-state control in metallosupramolecular systems represents a central challenge in the design and development of stimuli-responsive molecular materials, with far-reaching implications for sensing, data storage and nanoelectronics. In this feature article, we present a systematic investigation drawing primarily from our recent work and review selected contributions from the broader literature, examining how supramolecular design principles govern spin-state transitions, with a particular emphasis on spin crossover (SCO) behaviour. Through studies spanning coordination cages, helicates and coordination polymers (CPs)/metal-organic frameworks (MOFs), we demonstrate how deliberate manipulation of coordination environment, molecular geometry, structural constraints and supramolecular packing motifs can be exploited to tune magnetic features inherent to the particular system, such as transition temperature (T1/2), cooperativity, hysteresis width and completeness. Contextualised against broader advances in the field, our findings establish metallosupramolecular design as a powerful and versatile platform for controlling spin-state behaviour, offering a clear pathway towards the rational development of next-generation switchable materials.