Peculiar Spin Crossover Behavior in the 2D Polymer K[FeIII(5Cl-thsa)2статья
Статья опубликована в высокорейтинговом журнале
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Дата последнего поиска статьи во внешних источниках: 4 марта 2022 г.
Авторы:
Spitsyna Nataliya G.,
Blagov Maxim A.,
Lazarenko Vladimir A.,
Svetogorov Roman D.,
Zubavichus Yan V.,
Zorina Leokadiya V.,
Maximova Olga,
Yaroslavtsev Sergey A.,
Rusakov Vyacheslav S.,
Raganyan Grigory V.,
Yagubskii Eduard B.,
Vasiliev Alexander N.
Аннотация:A potassium salt of the N2S2O2-coordination Fe(III) anion K[Fe(5Clthsa)2] (1) (5Cl-thsa − 5-chlorosalicylaldehyde thiosemicarbazone) is synthesizedand characterized structurally and magnetically over a wide temperature range. Twopolymorphs of salt 1 characterized by the common 2D polymer nature and assigned tothe same orthorhombic Pbcn space group have been identified. The molecularstructure of the minor polymorph of 1 was solved and refined at 100, 250, and 300 Kis shown to correspond to the LS configuration. The dominant polymorph of 1features K+ cations disordered over a few crystallographic sites, while the minorpolymorph includes fully ordered K+ cations. The major polymorph exhibits acomplete three-step cooperative spin-crossover transition both in the heating andcooling modes: The first step occurs in a temperature range from 2 to 50 K; thesecond abrupt hysteretic step occurs from 200 to 250 K with T1/2 = 230 K and a 6 Khysteresis loop. The third gradual step occurs from 250 to 440 K. According to 57FeMössbauer, XRPD, and EXAFS data, the spin-crossover transition for the dominant polymorph is quite peculiar. Indeed, the increasein the HS concentration by 57% at the second step does not result in the expected significant increase in the iron(III)−ligand bondlengths. In addition, the final step of the spin conversion (ΔγHS = 26%) is associated with a structural phase transition with asymmetry lowering from the orthorhombic (Pbcn) to the monoclinic (P21/n) space group. This nontrivial phenomenon wasinvestigated in detail by applying magnetization measurements, electron spin resonance, 57Fe Mössbauer spectroscopy, and DFTcalculations. These results provide a new platform for understanding the multistep spin-crossover character in the Fe(III) thsacomplexesand related compounds.