Xiao-Ya Dou, Yi-Ran Jiang, Le-Jie Liu, Ling-Ya Peng*, Ganglong Cui*, and Yu Fang. Angew. Chem. Int. Ed. 2026, e6897356. https://onlinelibrary.wiley.com/doi/epdf/10.1002/anie.6897356

Electron spin refers to the intrinsic angular momentum property of electron, which underpins the electron transfer and molecular interactions in photochemistry. The precise manipulation of electron spin can enhance catalytic performance. However, the correlation between spin states and catalytic activity is still elusive, especially in the energy transfer (EnT)-catalyzed photocycloaddition and photo-ene reactions. Here, we rationalize the EnT process and clarify the chemoselectivity encompassing Marcus theory and ab initio methods. The initial photophysical process of photocatalyst isopropylthioxanthone (ITX) involves a nonadiabatic transition of ¹ππ*→³nπ*→³ππ* upon excitation, populating the long-lived ³ππ* state. In the presence of 1,5-dienes, the intrinsic deactivation pathway of photocatalyst ITX does not suppress the intermolecular spin-allowed EnT process with substrates, and this process is accompanied by spin multiplicity transfer within the Marcus normal region. The triplet-state 1,5-diene preferentially undergoes 5-exo-trig radical cyclization, followed by intersystem crossing to the open-shell singlet state, where the reaction branches to yield bicyclo[2.1.1]hexanes or cyclopentanes. It should be noted that both the photocycloaddition and photo-ene reactions exhibit spin selectivity, whereas the chemoselectivity is governed in the open-shell singlet state. Furthermore, quantum mechanical tunneling effects play a decisive role in promoting the photo-ene reaction and reshaping the reaction pathways. Guided by Marcus theory, spin-dependent catalysis can be further regulated through amino-group substitution, which not only elevates the EnT efficiency but also enhances the photocycloaddition chemoselectivity.

Our work not only clarifies the observed selectivity and the spin-activity correlation, but also establishes a general strategy to theoretically modulate both the EnT process and the ensuing spin-dependent reaction pathway under the guidance of Marcus theory.

First Author: Dou Xiaoya, master’s student, Shaanxi Normal University

Correspondence Authors: Dr. Peng Lingya, Shaanxi Normal University; Prof. Cui Ganglong, Beijing Normal University

Full Text Link: https://onlinelibrary.wiley.com/doi/epdf/10.1002/anie.6897356