High-spin versus spin-crossover versus low-spin: geometry intervention in cooperativity in a 3D polymorphic iron(II)-tetrazole MOFs system

Reported here are three 3D metal-organic framework (MOF) polymorphs with the chemical formula [Fe-2(H(0.67)bdt)(3)]center dot xH(2)O (H(2)bdt = 5,5'-(1,4-phenylene)bis(1H-tetrazole)), all of which are constructed from similar Fe-II-tetrazole rod secondary building units (SBUs) via covalent links, but exhibit diverse spin states regulated by inter-chain cooperativity.