Clarke Ryan M, Hazin Khatera, Thompson John R, Savard Didier, Prosser Kathleen E, Storr Tim
Department of Chemistry, Simon Fraser University , Burnaby, British Columbia V5A 1S6, Canada.
Inorg Chem. 2016 Jan 19;55(2):762-74. doi: 10.1021/acs.inorgchem.5b02231. Epub 2015 Dec 31.
The geometric and electronic structure of a doubly oxidized bimetallic Co complex containing two redox-active salen moieties connected via a 1,2-phenylene linker was investigated and compared to an oxidized monomeric analogue. Both complexes, namely, CoL(1) and Co2L(2), are oxidized to the mono- and dications, respectively, with AgSbF6 and characterized by X-ray crystallography for the monomer and by vis-NIR (NIR = near-infrared) spectroscopy, electron paramagnetic resonance (EPR) spectroscopy, superconducting quantum interference device (SQUID) magnetometry, and density functional theory (DFT) calculations for both the monomer and dimer. Both complexes exhibit a water molecule coordinated in the apical position upon oxidation. CoL(1)-H2O displays a broad NIR band at 8500 cm(-1) (8400 M(-1) cm(-1)), which is consistent with recent reports on oxidized Co salen complexes (Kochem, A. et al., Inorg. Chem., 2012, 51, 10557-10571 and Kurahashi, T. et al., Inorg. Chem., 2013, 52, 3908-3919). DFT calculations predict a triplet ground state with significant ligand and metal contributions to the singularly occupied molecular orbitals. The majority (∼75%) of the total spin density is localized on the metal, highlighting both high-spin Co(III) and Co(II)L(•) character in the electronic ground state. Further oxidation of CoL(1) to the dication affords a low-spin Co(III) phenoxyl radical species. The NIR features for Co2L(2)-2H2O at 8600 cm(-1) (17 800 M(-1) cm(-1)) are doubly intense in comparison to CoL(1)-H2O owing to the description of Co2L(2)-2H2O as two non-interacting oxidized Co salen complexes bound via the central phenylene linker. Interestingly, TD-DFT calculations predict two electronic transitions that are 353 cm(-1) apart. The NIR spectrum of the analogous Ni complex, Ni2L(2), exhibits two intense transitions (4890 cm(-1)/26 500 M(-1) cm(-1) and 4200 cm(-1)/21 200 M(-1) cm(-1)) due to exciton coupling in the excited state. Only one broad band is observed in the NIR spectrum for Co2L(2)-2H2O as a result of the contracted donor and acceptor orbitals and overall CT character.
研究了一种双氧化双金属钴配合物的几何和电子结构，该配合物包含两个通过1,2 - 亚苯基连接基相连的氧化还原活性双水杨醛缩邻苯二胺（salen）部分，并与氧化的单体类似物进行了比较。这两种配合物，即CoL(1)和Co2L(2)，分别用AgSbF6氧化为单阳离子和双阳离子，通过X射线晶体学对单体进行表征，并通过可见 - 近红外（NIR = 近红外）光谱、电子顺磁共振（EPR）光谱、超导量子干涉装置（SQUID）磁强计以及对单体和二聚体的密度泛函理论（DFT）计算进行表征。两种配合物在氧化时均在顶端位置配位有一个水分子。CoL(1)-H2O在8500 cm(-1)（8400 M(-1) cm(-1)）处显示出一个宽的近红外带，这与最近关于氧化钴salen配合物的报道一致（科赫姆，A.等人，《无机化学》，2012年，51卷，10557 - 10571页；仓桥，T.等人，《无机化学》，2013年，52卷，3908 - 3919页）。DFT计算预测其基态为三重态，配体和金属对单占据分子轨道有显著贡献。总自旋密度的大部分（约75%）定域在金属上，突出了电子基态中高自旋Co(III)和Co(II)L(•)的特征。CoL(1)进一步氧化为双阳离子得到一种低自旋Co(III)苯氧基自由基物种。Co2L(2)-2H2O在8600 cm(-1)（17800 M(-1) cm(-1)）处的近红外特征与CoL(1)-H2O相比强度加倍，这是因为Co2L(2)-2H2O被描述为通过中心亚苯基连接基结合的两个非相互作用的氧化钴salen配合物。有趣的是，含时密度泛函理论（TD - DFT）计算预测有两个电子跃迁，它们相隔353 cm(-1)。类似的镍配合物Ni2L(2)的近红外光谱由于激发态中的激子耦合而显示出两个强跃迁（4890 cm(-1)/26500 M(-1) cm(-1)和4200 cm(-1)/21200 M(-1) cm(-1)）。由于供体和受体轨道收缩以及整体电荷转移（CT）特征，在Co2L(2)-2H2O的近红外光谱中只观察到一个宽带。
