康 · 学术 | Reaction of the Day No. 1771

Carbon Radical Generation by Irreversible Metal-to-ligand Charge Transfer

Zhiqiang Wei1,2,3, Xiang Li1,3, Lin Xiao1,3, Yu He1,3, Zhao Liu1, Kaidi Zhu1, Chuanfa Ni1, Xiao-Song Xue*1 & Jinbo Hu*1,2

1. State Key Laboratory of Fluorine and Nitrogen Chemistry and Advanced Materials, Shanghai Institute of Organic Chemistry, University of Chinese Academy of Sciences, Chinese Academy of Sciences, 345 Ling-Ling Road, Shanghai 200032, China. 2. School of Physical Science and Technology, ShanghaiTech University, 100 Haike Road, Shanghai 201210, China. 3. These authors contributed equally: Zhiqiang Wei, Xiang Li, Lin Xiao, Yu He.

—Nature., 2026, doi:10.1038/s41586-026-11368-9

Recommended by Depei Meng _ MC4

KEY WORDS: Metal-to-ligand charge transfer, Cu catalysis, photo chemistry, fluoroalkylation(反应类型), C(sp)─C(F), C(sp3)-C(F), C(sp3)-I, (成键类型), perfluorocyclobutyl iodide (I-FCB), alkynes, alkene,arenes (原料), fluorinated product (产物)

ABSTRACT: Metal-to-ligand charge transfer (MLCT) is a fundamental photoinduced process that underpins a broad range of energy- or electron-transfer events. In the absence of productive substrate engagement, the MLCT excited state typically relaxes to the ground state via photophysical deactivation, reflecting its largely reversible character. Here we report a class of isolable copper–heteroaryl sulfone complexes that, upon visible light irradiation, undergo an irreversible MLCT-driven fragmentation through C–S bond cleavage within the coordinated sulfone ligand, generating carbon-centered radicals. Spectroscopic and computational studies support the formation of MLCT-derived excited states and a low-barrier pathway for C–S bond cleavage. This reactivity is largely independent of the reduction potentials of the corresponding free sulfones, enabling the generation of fluoroalkyl and non-fluorinated tertiary, secondary, and primary (even methyl) alkyl radicals. We demonstrate the utility of this platform in copper-catalyzed C–H fluoroalkylation of arenes and terminal alkynes. Leveraging these MLCT-generated trifluoromethyl radicals to initiate halogen-atom transfer (XAT) from perfluorocyclobutyl iodide (I-FCB), we also achieve radical perfluorocyclobutylation–iodination of alkenes, addressing a longstanding challenge in the incorporation of perfluorocyclobutyl motifs.

Addressing the challenge of irreversible metal-to-ligand charge transfer (MLCT).b, Reaction design. c. Irreversible MLCT-initiated perfluoroalkylation-iodination of alkenes

Characterization and reactivity investigation of the isolated copper(I)-sulfone complexes. a, Preparation of copper(I)-sulfone complexes with sulfone 1a and 1b. b, Preparation of copper(I)-sulfone complex with sulfone 1c. c, Stoichiometric reactions of complex Cu-2 under blue LEDs irradiation in CH2Cl2

MLCT-enabled alkylation. a, MLCT-enabled generation of alkyl radicals; 2, 3, 4, 6-11, NMR yield; 5, GC yield. b, MLCT-enabled alkylation of alkenes. c, Cu-complex-enabled trifluoromethyl- and difluoromethyl-azidation of alkenes. d, Cu-complex-catalyzed fluoroalkylation of arenes. Sulfones 1c and 1d are used, respectively. e, MLCT-enabled and copper-catalyzed fluoroalkylation of terminal alkynes.

Synthesis and reactivity investigation of perfluorocyclobutyl iodide (I-FCB). a, Synthesis of perfluorocyclobutyl iodide. b, Reactivity of perfluorocyclobutyl iodide. c, Optimization of the perfluorocyclobutylation-iodination of alkenes; d, Competition between Cu-2 and I-FCB. 

Scope of the reaction with various alkenes

Synthetic applications: Product transformations

Summary and Comments

In summary, Prof. Jinbo Hu group and Prof. Xiao-Song Xue group report a class of isolable copper–heteroaryl sulfone complexes that undergo irreversible metal-to-ligand charge transfer (MLCT) under visible-light irradiation, coupled with C–S bond cleavage within the coordinated sulfone ligand, to directly generate carbon-centered radicals. This platform generates both fluoroalkyl and non-fluorinated tertiary, secondary, and primary (even methyl) alkyl radicals, with radical generation largely independent of the reduction potentials of the corresponding free sulfones. The utility is demonstrated in copper-catalyzed C–H fluoroalkylation of arenes and terminal alkynes, and the MLCT-generated CF? radical is further exploited to initiate halogen-atom transfer (XAT) from perfluorocyclobutyl iodide (I-FCB), enabling radical perfluorocyclobutylation–iodination of alkenes and addressing a longstanding challenge in perfluorocyclobutyl incorporation.

中国科学院上海有机化学研究所胡金波教授团队联合薛小松教授团队报道了一类可分离的铜-杂芳基砜配合物，其在可见光照射下可经由不可逆的金属到配体电荷转移（MLCT）过程，伴随配位砜配体内C–S键断裂，直接生成碳中心自由基。该平台可生成氟烷基及非氟化的叔、仲、伯（甚至甲基）烷基自由基，且自由基生成行为基本不受游离砜还原电位的影响。作者展示了该平台在铜催化芳烃和末端炔烃C–H氟烷基化中的应用，并利用MLCT生成的CF?自由基对全氟环丁基碘（I-FCB）引发卤原子转移（XAT），实现了烯烃的全氟环丁基化-碘化反应，解决了全氟环丁基引入这一长期挑战.