Electronic Structure Description of a Doubly Oxidized Bimetallic Cobalt Complex with Proradical Ligands
Electronic Structure Description of a Doubly Oxidized Bimetallic Cobalt Complex with Proradical Ligands
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DOI：
10.1021/acs.inorgchem.5b02231
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发表时间：
2016-01-18
影响因子：
4.6
通讯作者：
Storr, Tim
中科院分区：
文献类型：
--
作者：
Clarke, Ryan M.;Hazin, Khatera;Storr, Tim
的几何和电子结构的双氧化的双氧化的钴络合物含有两个氧化还原活性的Salen部分连接通过1，2-亚苯基接头进行了研究，并比较氧化的单体类似物。这两种复合物，即CoL 1和Co2 L2，分别氧化的单和dications，与AgSbF 6和其特征在于通过X射线晶体学的单体和可见-NIR（NIR =近红外）光谱，电子顺磁共振（EPR）光谱，超导量子干涉器件（SQUID）的磁力，和密度泛函理论（DFT）计算的单体和二聚体。这两种配合物都表现出在氧化后的顶端位置配位的水分子。[CoL 1-H2O]（+）在8500 cm（-1）（8400 M-1 cm（-1））处显示宽的NIR带，这与最近关于氧化的Co salen络合物的报道一致（Kochem，A.例如，无机化学，2012，51，1055710571和Kurahashi，T.例如，无机化学，2013，52，39083919）。密度泛函理论计算预测的三重基态与显着的配体和金属的贡献，奇异占据的分子轨道。总自旋密度的大部分（类似于75%）位于金属上，突出了电子基态中的高自旋Co（III）和Co（II）L-中心点特征。进一步氧化CoL 1的双阳离子提供了一个低自旋钴（III）苯氧基自由基物种。[Co2 L2 - 2 H（2）O]（2+）在8600 cm（-1）（17 800 M-1 cm（-1））处的近红外光谱特征比[CoL 1-H2O]（+）的近红外光谱特征强一倍，这是由于[Co2 L2 - 2 H（2）O]（2+）被描述为两个通过中心亚苯基连接基结合的非相互作用的氧化Co salen络合物。有趣的是，TD-DFT计算预测两个电子跃迁相距353 cm（-1）。[Ni 2L 2]（2+）的近红外光谱显示出两个强跃迁（4890 cm（-1）/26500 M-1cm（-1）和4200 cm（-1）/21200 M-1cm（-1）），这是由于激发态的激子耦合引起的。在[Co_2L_2 - 2 H（2）O]（2+）的近红外光谱中只观察到一个宽的谱带，这是由于给体和受体轨道收缩以及整体CT特征的结果。
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, CoL1 and Co2L2, 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. [CoL1-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, 1055710571 and Kurahashi, T. et al., Inorg. Chem., 2013, 52, 39083919). DFT calculations predict a triplet ground state with significant ligand and metal contributions to the singularly occupied molecular orbitals. The majority (similar to 75%) of the total spin density is localized on the metal, highlighting both high-spin Co(III) and Co(II)L-center dot character in the electronic ground state. Further oxidation of CoL1 to the dication affords a low-spin Co(III) phenoxyl radical species. The NIR features for [Co2L2-2H(2)O](2+) at 8600 cm(-1) (17 800 M-1 cm(-1)) are doubly intense in comparison to [CoL1-H2O](+) owing to the description of [Co2L2-2H(2)O](2+) 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, [Ni2L2](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 [Co2L2-2H(2)O](2+) as a result of the contracted donor and acceptor orbitals and overall CT character.