Non-innocent ligand behaviour of a bimetallic Cu complex employing a bridging catecholate
Non-innocent ligand behaviour of a bimetallic Cu complex employing a bridging catecholate
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使用桥联儿茶酚盐的双金属铜络合物的非无害配体行为
DOI：
10.1039/c2dt30444a
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发表时间：
2012
影响因子：
4
通讯作者：
Yuichi Shimazaki and Tim Storr
中科院分区：
文献类型：
--
作者：
Tim J. Dunn;Linus Chiang;Caterina F. Ramogida;Mike I. Webb;Didier Savard;Miyuki Sakaguchi;Takashi Ogura;Yuichi Shimazaki and Tim Storr
研究了一种双金属铜席夫碱配合物及其单电子氧化形态的几何和电子结构。中性络合物1中的两个salen单元通过桥接儿茶酚酸功能连接，两个Cu(II) d9中心之间的耦合是弱反铁磁性的，基于固态磁研究（J = - 3 cm−1）和变温电子顺磁共振（EPR） （J = - 3 cm−1）。理论计算（DFT）与实验结果（J =−7 cm−1）一致，并为中性体系的耦合机制提供了新的见解。单电子氧化提供[1]+，观察到[1]+在溶液中的稳定性有限。被氧化的配合物在溶液中被确定为配基自由基，电子空穴可能定位在氧化还原活性的二恶烃、酚酸酯配体上，或在整个配体系统上脱域。电化学实验和紫外-可见-近红外光谱结合密度泛函理论（DFT）计算，深入了解了该体系的氧化轨迹和离域程度。实验确定了[1˙]+的配体自由基定位在二恶索烯桥上，而计算预测的外酚酸基团上有少量自旋密度。通过与Ni模拟物的数据比较（Inorg），这项任务得到了帮助。化学。科学通报，2011,50,6746)。在CH2Cl2溶液中，[1˙]+ (λex = 413 nm)的共振拉曼光谱在1308 cm−1处比在1处清晰地显示出一个新的谱带，支持半醌的形成。三自旋体系[1˙]+上的变温EPR没有提供耦合相互作用的明确信息，可能是由于S = 3/2和S = 1/2态之间的能量差很小和/或零场分裂很小，加上明显的谱线展宽。该数据与对[1˙]+的整体电子结构的描述是一致的，它是一个双金属铜（II）配合物，具有桥定域的半醌配体自由基。
The geometric and electronic structure of a bimetallic Cu Schiff-base complex and its one-electron oxidized form have been investigated. The two salen units in the neutral complex 1 are linked via a bridging catecholate function, and the coupling between the two Cu(II) d9 centres was determined to be weakly antiferromagnetic on the basis of solid-state magnetic studies (J = −3 cm−1), and variable-temperature electron paramagnetic resonance (EPR) (J = −3 cm−1). Theoretical calculations (DFT) were in agreement with the experimental results (J = −7 cm−1), and provided insight into the coupling mechanism for the neutral system. One-electron oxidation provided [1]+ which was observed to have limited stability in solution. The oxidized complex was determined to be a ligand radical species in solution, with the electron hole potentially localized on the redox-active dioxolene, the phenolate ligands, or delocalized over the entire ligand system. Electrochemical experiments and UV-vis-NIR spectroscopy, in combination with density functional theory (DFT) calculations, provided insight into the locus of oxidation and the degree of delocalization in this system. The ligand radical for [1˙]+ was determined experimentally to be localized on the dioxolene bridge with a small amount of spin density on the outer phenolate moieties predicted by the calculations. This assignment was aided via comparison to data for the Ni analogue (Inorg. Chem., 2011, 50, 6746). The resonance Raman spectrum of [1˙]+ (λex = 413 nm) in CH2Cl2 solution clearly exhibited a new band at 1308 cm−1 in comparison to 1, supporting semiquinone formation. Variable-temperature EPR on the three-spin system [1˙]+ did not provide definitive information on the coupling interaction, possibly due to a very small difference in energy between the S = 3/2 and S = 1/2 states and/or a very small zero-field splitting, in combination with significant line-broadening. The data is consistent with a description of the overall electronic structure of [1˙]+ as a bimetallic Cu(II) complex with a bridge-localized semiquinone ligand radical species.