南开大学刘天飞团队报道了可见光照射下自旋禁止激发产生二氟卡宾。相关研究成果发表在2024年11月4日出版的《美国化学会杂志》。

该文报道了在450nm蓝光照射下，通过自旋禁止激发从二氟甲烷双（锍叶立德）1生成二氟卡宾。通过与苯乙烯衍生物反应生成二氟环丙烷化，并插入RX-H键（X=O，S）生成RXCF₂H，证实了二氟卡宾的形成。

光谱和动力学研究以及计算化学支持了，二氟甲烷双（锍叶立德）形成二氟卡宾的自旋禁止激发机制。

通过对前体自由基捕获反应的时间分辨EPR光谱研究，以及二甲基（苯硫醇）丙二酰自由基二聚体的分离，证实了化合物1中两个S-C键在辐射下的均裂。

进一步的研究表明，基于同位素标记的加扰实验和DFT计算，均裂过程在溶剂笼中异步发生。

附：英文原文

Title: Difluorocarbene Generation via a Spin-Forbidden Excitation under Visible Light Irradiation

Author: Shan Liu, Guang-Ning Pan, Yijing Ling, Feng Gao, Yin Yang, Ganglong Cui, Qilong Shen, Tianfei Liu

Issue&Volume: November 4, 2024

Abstract: The generation of difluorocarbene from difluoromethane bis(sulfonium ylide) 1 through spin-forbidden excitation under irradiation with 450 nm blue light was reported. The formation of difluorocarbene was confirmed by its reaction with styrene derivatives for the generation of difluorocyclopropanation and insertion into RX–H bonds (X = O, S) for the generation of RXCF2H. The spin-forbidden excitation mechanism for the formation of difluorocarbene from difluoromethane bis(sulfonium ylide) was supported by spectroscopic and kinetic studies as well as computational chemistry. The homolytic cleavage of two S–C bonds in compound 1 under irradiation was confirmed by time-resolved EPR spectroscopic studies of the precursor’s free-radical-capturing reaction, as well as the isolation of the dimer of dimethyl (phenylthiol)malonyl radical. Further studies showed that the homolytic cleavage process occurred asynchronously in the solvent cage based on the isotope-labeled scrambling experiments and DFT calculations.

DOI: 10.1021/jacs.4c10939

Source: https://pubs.acs.org/doi/abs/10.1021/jacs.4c10939