Benzoselenadiazole‐based Photosensitizers: Effect of Substituent Position on the Electrochemical, Photophysical, and Photochemical Properties

Selenium-containing photosensitizers are attracting growing attention for optoelectronic and biomedical applications due to their distinctive redox and photophysical characteristics. Herein, we present a series of novel donor-acceptor benzoselenadiazole derivatives synthesized via Buchwald-Hartwig and Ullmann-type cross-coupling reactions. Fine-tuning of the substitution pattern on the benzoselenadiazole core leads to distinct positive solvatochromism, reflecting strong intramolecular charge-transfer character. Most of the synthesized compounds exhibited efficient singlet oxygen (¹O₂) generation, with generation quantum yield values (Φ_Δ) of up to 0.74. Their photocatalytic activity was further demonstrated through the visible light-driven oxidation of 2-furoic acid, achieving complete conversion within four hours at a catalyst loading of just 0.05 mol%. The results highlight the potential of benzoselenadiazole-based chromophores as multifunctional materials for light-driven applications in photocatalysis, and as promising scaffolds for the future design of photosensitizers.