Exploring excited state dynamics and two-photon absorption response in synthetic β-chalcone-substituted tetraphenylporphyrins derivatives

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Porphyrins' unique structure confers exceptional light-interacting properties, driving interest in their use in medical therapies. This work investigates synthetic β-chalcone-substituted tetraphenylporphyrins derivatives using fluorescence-based methods to evaluate fluorescence, triplet formation, and internal conversion quantum yields, as well as fluorescence lifetimes, thereby revealing radiative and non-radiative decay rates. Two-photon absorption cross-sections were measured via the double-pulse induced fluorescence technique. Results highlight the tetraphenylporphyrin-chalcone interaction, with triplet-formation quantum yields of around 30% and internal-conversion yields up to 86%. Combined with short fluorescence lifetimes of no more than 10 ns, the decay rates suggest strong potential for photodynamic (PDT) and photothermal (PTT) therapies. Notably, the CP3 derivative bearing a high-electron-withdrawing nitrophenyl moiety increased the internal conversion rate to 360 × 10 6 s −1 , thereby demonstrating its photothermal therapy potential. The set also shows an increase in two-photon absorption, achieving up to 48 GM within the first biological window for CP1 and CP5, which could be useful for deeper tissue penetration in medical applications.