Spin-Crossover Hysteresis of [FeII(LHiPr)2(NCS)2] (LHiPr = N-2-Pyridylmethylene-4-Isopropylaniline) Accompanied by Isopropyl Conformation Isomerism

Magnetochemistry

Naotaka Mochida²  Akifumi Kimura²  Takayuki Ishida¹ 

[1] Department of Engineering Science, The University of Electro-Communications, Chofu, Tokyo 182-8585, Japan;

关键词: spin crossover;    hysteresis;    structural phase transition;    order-disorder transition;    conformational isomer;    conformer;    spin transition;    crystal structure;   

DOI  :  10.3390/magnetochemistry1010017

来源: mdpi

【 摘 要 】

[Fe^II(L_H^iPr)₂(NCS)₂] (L_H^iPr = N-2-pyridylmethylene-4-isopropylaniline) showed an abrupt spin-crossover (SCO) at T_1/2↓ = 154 K on cooling and at T_1/2↑ = 167 K on heating. The thermal hysteresis with a width of 13 K is related with the structural solid-state phase transition. The space group was unchanged as P2₁/n with Z = 8, and there are two crystallographically independent molecules in a unit cell at 130 and 180 K. The two iron (II) sites synchronously underwent the SCO. The most drastic structural change across the SCO was found in the conformation isomerization of an isopropyl group. Namely, rotation around the C(sp²)–C(sp³) bond by ca. 120° takes place during the SCO. There is no structural disorder in the high-temperature phase. The thermal hysteresis probably originates in the bulk isomerization requiring considerable activation energy in the crystalline solid.

【 授权许可】

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