Precise Control and Consecutive Modulation of Spin Transition Temperature Using Chemical Migration in Porous Coordination Polymers

Precise control of spin transition temperature (T-c) is one of the most important challenges in molecular magnetism. A Hofmann-type porous coordination polymer {Fe(pz)[Pt-II(CN)(4)]) (1; pz = pyrazine) exhibited cooperative spin transition near room temperature (T-c(up) = 304 K and T-c(down) = 284 K) and its iodine adduct {Fe(pz)[Pt-II/IV(CN)(4)(I)]} (1-I), repared by oxidative addition of iodine to the open metal sites of Pt-II, raised the T-c by 100 K. DSC and microscopic Raman spectra of a solid mixture of 1-I and 1 revealed that iodine migrated from 1-I to 1 through the grain boundary after heating above 398 K. We have succeeded in precisely controlling the iodine content of {Fe(pz)[Pt(CN)(4)(I)(n)]) (1-In; n = 0.0-1.0), which resulted in consecutive modulation of T-c in the 300-400 K while maintaining the hysteresis width. Furthermore, it was demonstrated that iodine migration in the solid mixture was triggered by the spin transition of 1-I. The magnetically bistable porous framework decorating guest interactive open-metal-site in the pore surface makes it possible to modulate T-c ad arbitrium through unique postsynthetic method using iodine migration. range