Thermochromic and Photoresponsive Cyanometalate Fe/Co Squares: Toward Control of the Electron Transfer Temperature

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• 作者：Yuan-Zhu Zhang ; Philip Ferko ; Diana Siretanu ; Rodica Ababei ; Nigam P. Rath ; Michael J. Shaw ; Rodolphe Cl茅rac ; Corine Mathoni猫re ; Stephen M. Holmes
• 刊名：Journal of the American Chemical Society
• 出版年：2014
• 出版时间：December 3, 2014
• 年：2014
• 卷：136
• 期：48
• 页码：16854-16864
• 全文大小：533K
• ISSN：1520-5126

文摘

Two structurally related and photoresponsive cyanide-bridged Fe/Co square complexes, {Fe₂Co₂}, are reported: {[(Tp^Me)Fe(CN)₃]₂[Co(bpy)₂]₂[(Tp^Me)Fe(CN)₃]₂}路12H₂O (2) and {[(Tp^Me)Fe(CN)₃]₂[Co(bpy)₂]₂[BPh₄]₂}路6MeCN (3), where Tp^Me and bpy are hydridotris(3-methylpyrazol-1-yl)borate and 2,2鈥?bipyridine, respectively. Through electrochemical and spectroscopic studies, the Tp^Me ligand appears to be a moderate 蟽 donor in comparison to others in the [NEt₄][(Tp^R)Fe^III(CN)₃] series [where Tp^R = Tp, hydridotris(pyrazol-1-yl)borate; Tp^Me = hydridotris(3-methylpyrazol-1-yl)borate; pzTp = tetrakis(pyrazol-1-yl)borate; Tp* = hydridotris(3,5-dimethylpyrazol-1-yl)borate; Tp*^Me = hydridotris(3,4,5-trimethylpyrazol-1-yl)borate]. The spectroscopic, structural, and magnetic data of the {Fe₂Co₂} squares indicate that thermally-induced intramolecular electron transfer reversibly converts {Fe^II_LS(渭-CN)Co^III_LS} pairs into {Fe^III_LS(渭-CN)Co^II_HS} units near ca. 230 and 244 K (T_1/2) for 2 and 3, respectively (LS: low spin; HS: high spin). These experimental results show that 2 and 3 display light-induced {Fe^III_LS(渭-CN)Co^II_HS} metastable states that relax to thermodynamic {Fe^II_LS(渭-CN)Co^III_LS} ones at ca. 90 K. Ancillary Tp^R ligand donor strength appears to be the dominant factor for tuning electron transfer properties in these {Fe₂Co₂} complexes.