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• 作者：Takeshi Fujinami ; Koshiro Nishi ; Daisuke Hamada ; Keishiro Murakami ; Naohide Matsumoto ; Seiichiro Iijima ; Masaaki Kojima ; Yukinari Sunatsuki
• 刊名：Inorganic Chemistry
• 出版年：2015
• 出版时间：August 3, 2015
• 年：2015
• 卷：54
• 期：15
• 页码：7291-7300
• 全文大小：541K
• ISSN：1520-510X

文摘

Solvent-free spin crossover Fe^II complex fac-[Fe^II(HL^n-Pr)₃]Cl路PF₆ was prepared, where HL^n-Pr denotes 2-methylimidazol-4-yl-methylideneamino-n-propyl. The magnetic susceptibility measurements at scan rate of 0.5 K min^鈥? showed two successive spin transition processes consisting of the first spin transition T₁ centered at 122 K (T_{1鈫?/sub> = 127.1 K, T1鈫?/sub> = 115.8 K) and the second spin transition T2 centered at ca. 105 K (T2鈫?/sub> = 115.8 K, T2鈫?/sub> = 97.2 K). The magnetic susceptibility measurements at the scan rate of 2.0, 1.0, 0.5, 0.25, and 0.1 K min^鈥? showed two scan speed dependent spin transitions, while the M枚ssbauer spectra detected only the first spin transition T1. The crystal structures were determined at 160, 143, 120, 110, 95 K in the cooling mode, and 110, 120, and 130 K in the warming mode so as to follow the spin transition process of high-spin HS 鈫?HS(T1) 鈫?HS(T2) 鈫?low-spin LS 鈫?LS(T2) 鈫?LS(T1) 鈫?HS. The crystal structures at all temperatures have a triclinic space group P1虆 with Z = 2. The complex-cation has an octahedral N6 coordination geometry with three bidentate ligands and assume a facial-isomer with 螖- and 螞-enantimorphs. Three imidazole groups of fac-[Fe^II(HL^n-Pr)3]²⁺ are hydrogen-bonded to three Cl^{鈥?/sup> ions. The 3:3 NH(imidazole)路路路Cl鈥?/sup> hydrogen-bonds form a stepwise ladder assembly structure, which is maintained during the spin transition process. The spin transition process is related to the structural changes of the FeN6 coordination environment, the order鈥揹isorder of PF6鈥?/sup> anion, and the conformation change of n-propyl groups. The Fe鈥揘 bond distance in the HS state is longer by 0.2 脜 than that in the LS state. Disorder of PF6鈥?/sup> anion is not observed in the LS state but in the HS state. The conformational changes of n-propyl groups are found in the spin transition processes except for HS 鈫?HS(T1) 鈫?HS(T2).}}