Photochemical Processes in a Rhenium(I) Tricarbonyl N-Heterocyclic Carbene Complex Studied by Time-Resolved Measurements
Photochemical Processes in a Rhenium(I) Tricarbonyl N-Heterocyclic Carbene Complex Studied by Time-Resolved Measurements
复制标题
DOI：
10.1021/acs.inorgchem.6b02936
复制
发表时间：
2017-03-20
影响因子：
4.6
通讯作者：
Onda, Ken
中科院分区：
文献类型：
--
作者：
Mukuta, Tatsuhiko;Simpson, Peter V.;Onda, Ken
在光化学反应条件下(乙腈溶液中)和非反应条件下(在二氯甲烷溶液中)，我们对一个含N-杂环卡宾配体的Re(I)羰基配合物Far[Re(CO)(3)(PylmPh)BR]进行了时间分辨红外光谱(TRIR)和发射寿命测量，以研究配体取代反应的机理。红外光谱测量表明，在皮秒尺度上没有反应，而阳离子产物Fac[Re(CO)(3)(PyImPh)(MeCN)(+)]仅在乙腈溶液中才在纳秒尺度上生成，这表明反应是从激发态开始热进行的。由于在TR-IR中没有观察到其他产物，因此我们得出结论，该反应是一个反应。温度相关发射寿命的测量和过渡态理论的分析表明，光取代反应是从金属到配体的电荷转移激发态进行的，该激发态的结构允许溶剂分子的势能配位。因此，溶剂的配位能力决定了反应是否进行。由于卡宾配体的独特性质，这一机理不同于其他类型的Re(I)羰基配合物的光化学反应。
We carried out time-resolved infrared (TR-IR) and emission lifetime measurements on a Re(I) carbonyl complex having an N-heterocyclic carbene ligand, namely, far[Re(CO)(3)(PylmPh)Br], under photochemically reactive (in solution in acetonitrile) and nonreactive (in solution in dichloromethane) conditions to investigate the mechanism of photochemical ligand substitution reactions. The TR-IR measurements revealed that no reaction occurs on a picosecond time scale and the cationic product, namely, fac[Re(CO)(3)(PyImPh)(MeCN)(+), is produced on a nanosecond time scale only in solution in acetonitrile, which indicates that the reaction proceeds thermally from the excited state. Because no other products were observed by TR-IR, we concluded that this reactions. The measurements of the temperature-dependent emission lifetime and analysis using transition-state theory revealed that the photochemical substitution reaction proceeds from a metal-to-ligand charge transfer excited state, the structure of which allows the potential coordination of a solvent molecule. Thus, the coordinating capacity of the solvent determines whether the reaction proceeds or not. This mechanism is different from those of photochemical reactions of other types of Re(I) carbonyl complexes owing to the unique characteristics of the carbene ligand.