Controlling Spin Switching with Anionic Supramolecular Frameworks

Encasing the classic spin-crossover (SCO) complex cation [Co­(terpy)2]2+ in different anionic supramolecular frameworks modulates its SCO behavior, tuning both its T1/2 (shift of up to 200 K) and the cooperativity of the system. The SCO behavior is influenced by the organization of the complex cations within supramolecular anionic frameworks comprising iodoperfluorobenzenes and iodide anions, with tighter packing of complexes leading to a more abrupt transition. This approach for the control of magnetic properties is applicable to any complex with suitable counterions and hence provides significant opportunity for further developing the properties of many such stimuli-responsive complexes, without requiring changes to their chemical structures. The magnetic properties of the materials presented herein are investigated through variable-temperature magnetic susceptibility measurements and variable-temperature and -pressure molecular structure studies.