Molecular Spin Crossover in Slow Motion: Light-Induced Spin-State Transitions in Trigonal Prismatic Iron(II) Complexes

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• 作者：Philipp Stock ; Eva Deck ; Silvia Hohnstein ; Jana Korzekwa ; Karsten Meyer ; Frank W. Heinemann ; Frank Breher ; Gerald Hörner
• 刊名：Inorganic Chemistry
• 出版年：2016
• 出版时间：June 6, 2016
• 年：2016
• 卷：55
• 期：11
• 页码：5254-5265
• 全文大小：611K
• 年卷期：0
• ISSN：1520-510X

文摘

A straightforward access is provided to iron(II) complexes showing exceedingly slow spin-state interconversion by utilizing trigonal-prismatic directing ligands (Lⁿ) of the extended-tripod type. A detailed analysis of the interrelations between complex structure (X-ray diffraction, density functional theory) and electronic character (SQUID magnetometry, Mössbauer spectroscopy, UV/vis spectroscopy) of the iron(II) center in mononuclear complexes [FeLⁿ] reveals spin crossover to occur along a coupled breathing/torsion reaction coordinate, shuttling the complex between the octahedral low-spin state and the trigonal-prismatic high-spin state along Bailar’s trigonal twist pathway. We associate both the long spin-state lifetimes in the millisecond domain close to room temperature and the substantial barriers against thermal scrambling (E_a ≈ 33 kJ mol^–1, from Arrhenius analysis) with stereochemical constraints. In particular, the topology of the κ⁶N ligands controls the temporary and structural dynamics during spin crossover.