170443 20260420103355.0 doi 10.1002/chem.70970 sideral 148923 ART-2026-148923 eng Pedrón Laserna, Manuel Universidad de Zaragoza (orcid)0000-0003-4249-6748 When light challenges heat: mechanistic insights into a reaction competing with Cadogan Cyclisation in Nitro‐Perylenediimides 2026 Visible-light-driven transformations have emerged as powerful and sustainable tools in modern organic synthesis. However, the intrinsic photochemical reactivity of polycyclic aromatic hydrocarbons (PAHs) remains underexplored. Among π-conjugated chromophores, perylenediimides (PDIs) combine exceptional photostability, strong visible-light absorption, and rich redox properties, yet their light-induced chemical transformations are still poorly understood. Herein, we report an unprecedented divergence between thermal and photochemical reactivity in the reaction of bay-nitrated PDIs (PDI-NO2) with triphenylphosphine. While thermal activation promotes a classical Cadogan-type reductive cyclization to afford N-annulated PDI carbazole, visible-light irradiation redirects the reaction toward a previously unobserved pathway, yielding a bay-functionalized 1-(iminophosphorane)-12-hydroxy PDI derivative in excellent yield. Experimental studies reveal a strong wavelength dependence, with blue light dominating the photochemical transformation. Notably, the initial nitro-to-nitroso conversion is not phosphine-mediated but arises from the strong reducing power of photoexcited PDI-NO2. Combined experimental and theoretical investigations demonstrate that light irradiation reshapes the reaction landscape by enabling access to charge-transfer and π–π* excited states, involving the population of an asymmetric unoccupied orbital localized on the nitroso moiety, thereby unlocking a phosphine-addition pathway inaccessible under thermal conditions. These findings establish orbital-selective excitation as a general design principle for exploiting visible light to control reaction pathways in π-conjugated chromophores. Access copy available to the general public Unrestricted info:eu-repo/semantics/openAccess by https://creativecommons.org/licenses/by/4.0/deed.es info:eu-repo/semantics/article info:eu-repo/semantics/publishedVersion Ciofini, Ilaria Hudhomme, Piétrick 2013 765 Universidad de Zaragoza Dpto. Química Orgánica Área Química Orgánica (2026), e70970 [11 pp.] Chemistry (Weinh.) Chemistry (Weinheim) 0947-6539 2202888 http://zaguan.unizar.es/record/170443/files/texto_completo.pdf Versión publicada 2508906 http://zaguan.unizar.es/record/170443/files/texto_completo.jpg?subformat=icon icon Versión publicada oai:zaguan.unizar.es:170443 articulos driver 2026-04-18-10:49:40 ARTICLE