Li Feng, Carpenter Stephanie H, Higgins Robert F, Hitt Mark G, Brennessel William W, Ferrier Maryline G, Cary Samantha K, Lezama-Pacheco Juan S, Wright Joshua T, Stein Benjamin W, Shores Matthew P, Neidig Michael L, Kozimor Stosh A, Matson Ellen M
Department of Chemistry, University of Rochester , Rochester, New York 14627, United States.
Department of Chemistry, Colorado State University , Fort Collins, Colorado 80523, United States.
Inorg Chem. 2017 Jun 19;56(12):7065-7080. doi: 10.1021/acs.inorgchem.7b00650. Epub 2017 May 26.
Inspired by the multielectron redox chemistry achieved using conventional organic-based redox-active ligands, we have characterized a series of iron-functionalized polyoxovanadate-alkoxide clusters in which the metal oxide scaffold functions as a three-dimensional, electron-deficient metalloligand. Four heterometallic clusters were prepared through sequential reduction, demonstrating that the metal oxide scaffold is capable of storing up to four electrons. These reduced products were characterized by cyclic voltammetry, IR, electronic absorption, and H NMR spectroscopies. Moreover, Mössbauer and X-ray absorption spectroscopies suggest that the redox events involve primarily the vanadium ions, while the iron atoms remained in the 3+ oxidation state throughout the redox series. In this sense, the vanadium portion of the cluster mimics a conventional organic-based redox-active ligand bound to an iron(III) ion. Magnetic coupling within the hexanuclear cluster was characterized using SQUID magnetometry. Overall, the results suggest extensive electronic delocalization between the metal centers of the cluster core. These results demonstrate the ability of electronically flexible, reducible metal oxide supports to function as redox-active reservoirs for transition-metal centers.
受使用传统有机基氧化还原活性配体实现的多电子氧化还原化学的启发，我们对一系列铁功能化的多氧钒酸盐 - 醇盐簇进行了表征，其中金属氧化物支架作为三维缺电子金属配体发挥作用。通过顺序还原制备了四个异金属簇，表明金属氧化物支架能够存储多达四个电子。这些还原产物通过循环伏安法、红外光谱、电子吸收光谱和核磁共振氢谱进行了表征。此外，穆斯堡尔光谱和X射线吸收光谱表明，氧化还原事件主要涉及钒离子，而在整个氧化还原系列中，铁原子保持在 +3 氧化态。从这个意义上说，簇的钒部分模拟了与铁（III）离子结合的传统有机基氧化还原活性配体。使用超导量子干涉仪磁力计对六核簇内的磁耦合进行了表征。总体而言，结果表明簇核心的金属中心之间存在广泛的电子离域。这些结果证明了具有电子灵活性、可还原的金属氧化物载体作为过渡金属中心的氧化还原活性储库的能力。
