title: Precise control and consecutive modulation of spin transition temperature using chemical migration in porous coordination polymers.
abstract: 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), prepared 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 range 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.
authors.affiliation: Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto 615-8510, Japan.
authors.forename: Ryo
authors.initials: R
authors.lastname: Ohtani
authors.forename: Ko
authors.initials: K
authors.lastname: Yoneda
authors.forename: Shuhei
authors.initials: S
authors.lastname: Furukawa
authors.forename: Nao
authors.initials: N
authors.lastname: Horike
authors.forename: Susumu
authors.initials: S
authors.lastname: Kitagawa
authors.forename: Ana B
authors.initials: AB
authors.lastname: Gaspar
authors.forename: M Carmen
authors.initials: MC
authors.lastname: Muñoz
authors.forename: José A
authors.initials: JA
authors.lastname: Real
authors.forename: Masaaki
authors.initials: M
authors.lastname: Ohba