triplet state) via a combined photochemical and transient absorption spectroscopic study. We found that the energy order between 1CT (charge transfer singlet state) and 3LE dictates the accessibility of 3LE/3CT for EnT, which can be effectively engineered by varying solvent polarity and D-A character to depopulate 3LE and facilitate EnT from the chemically more tunable 3CT state for photosensitization
三重态-三重态能量转移 (EnT) 是光催化中的基本活化途径。在这项工作中,我们报告了基于 EnT 的光催化反应中咔唑 - 氰基苯供体 - 受体(DA)荧光团的三重激发态的机械起源,并证明了控制 3LE(局部激发三重态)可及性的关键因素和通过结合光化学和瞬态吸收光谱研究的 3CT(电荷转移三重态)。我们发现 1CT(电荷转移单线态)和 3LE 之间的能量顺序决定了 EnT 3LE/3CT 的可及性,这可以通过改变溶剂极性和 DA 特征来有效地设计,以减少 3LE 的数量并促进 EnT 从化学更可调的 3CT光敏状态。遵循上述设计原则,鉴定了一种具有强 DA 特性和弱氧化还原电位的新型 DA 荧光团,该荧光团对 Ni(II) 催化的羧酸和芳基卤化物的交叉偶联表现出高效率,具有广泛的底物范围和高选择性。我们的结果不仅为 DA 荧光团的 EnT 机制提供了关键的基本见解,而且还确立了其在 EnT
Ni(II)-Mediated Photochemical Oxidative Esterification of Aldehydes with Phenols
作者:Lu-Lu Chai、You-Hui Zhao、David James Young、Xinhua Lu、Hong-Xi Li
DOI:10.1021/acs.orglett.2c02560
日期:2022.9.30
The photopromoted, Ni-catalyzed acceptorless dehydrogenation esterification of phenols and aromatic aldehydes has been achieved in an oxidant- and external photosensitizer-free manner. This reliable and atom-economical transformation was tolerant to a wide range of functional groups and proceeded efficiently to give various aryl benzoates in moderate to high yields. Additionally, this photocatalytic