A dual-switching spin-crossover framework with redox regulation and guest response

A dual-switching spin crossover metal-organic framework (SCO-MOF) [Fe(TPB){PtII(CN)4}]·3iPrOH·4H2O (TPB = 1,2,4,5-tetra(pyridin-4-yl)benzene) is developed via the combination of redox-active framework and tunable guests. The reversible structural transformation between [PtII(CN)4]2− and [PtIVBr2(CN)4]2− moieties can be manipulated by redox post-synthetic modification (PSM), which results in the change of SCO behaviors from step-wise to one-step. The influences of the oxidative addition of bromides on the ligand field splitting of Fe side are further explored by density functional theory calculations. Besides, the modulation of hysteretic four-/three-step, one-step and four-step SCO behaviors can be achieved by tuning the composition of guest molecules. Therefore, the combination of electronic bistability, redox reaction and guest recognition in a homogeneous lattice provides a utility platform for designing multi-responsive molecule-based materials.