A Copper–Nitroxide Adduct Exhibiting Separate Single Crystal-to-Single Crystal Polymerization–Depolymerization and Spin Crossover Transitions

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• 作者：Victor Ovcharenko ; Sergey Fokin ; Elvina Chubakova ; Galina Romanenko ; Artem Bogomyakov ; Zhanna Dobrokhotova ; Nikita Lukzen ; Vitaly Morozov ; Marina Petrova ; Maria Petrova ; Ekaterina Zueva ; Igor Rozentsveig ; Elena Rudyakova ; Galina Levkovskaya ; Renad Sagdeev
• 刊名：Inorganic Chemistry
• 出版年：2016
• 出版时间：June 20, 2016
• 年：2016
• 卷：55
• 期：12
• 页码：5853-5861
• 全文大小：412K
• 年卷期：0
• ISSN：1520-510X

文摘

A complex cascade of solid-state processes initiated by variation of temperature was found for the heterospin complex [Cu(hfac)₂L^Me/Et] formed in the reaction of copper(II) hexafluoroacetylacetonate [Cu(hfac)₂] with stable nitronyl nitroxide 2-(1-methyl-3-ethyl-1H-pyrazol-4-yl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole-3-oxide-1-oxyl (L^Me/Et). The cooling of the compound below 260 K initiated a solid-state chemical reaction, which led to a depolymerization of chains and formation of a pair heterospin complex [Cu(hfac)₂L^Me/Et₂][[Cu(hfac)₂]₃L^Me/Et₂]. Further decrease in temperature below 144 K led to a spin transition accompanied by a drastic decrease in the effective magnetic moment from 2.52 to 2.24 μ_B. When the compound was heated, the order of effects was reversed: at first, the magnetic moment abruptly increased, and then the molecular fragments of the pair cluster united into polymer chains. Two hysteresis loops correspond to this cascade of temperature-induced structural transformations on the experimental dependence μ_eff(T): one at high (T↑ = 283 K and T↓ = 260 K) and the other at low (T↑ = 161 K, T↓ = 144 K) temperature. The spin transitions were also recorded for the [[Cu(hfac)₂]₃L^Bu/Et₂] and [[Cu(hfac)₂]₅L^Bu/Et₄] molecular complexes, which are models of the trinuclear fragment of the {[Cu(hfac)₂]₃L^Me/Et₂} pair cluster.