Solvent‐Dependent Photophysics and Nonlinear Optical Properties of a Triazolobenzanthrone: Role of Hydrogen Bond‐Assisted Intramolecular Charge Transfer

ABSTRACT

The photophysical, solvatochromic, and nonlinear optical properties of Benzo[10,1]phenanthro[2,3‐ d ][1,2,3]triazol‐7(3 H )‐one were investigated using both experimental and computational methods. The molecule exhibits weakly solvatochromic absorption but strongly red‐shifted emission (~120 nm), indicating the formation of a polar intramolecular charge transfer (ICT) excited state. The Lippert–Mataga analysis shows poor correlation but strong linearity in protic solvents, confirming the dominance of hydrogen bonding interactions over dielectric effects. Further, solvent polarity was analyzed using three complementary solvatochromic models: the Kamlet–Abboud–Taft (KAT), Catalán, and Laurence scales. Lifetime and quantum yield measurements reveal enhanced nonradiative decay in protic solvents due to hydrogen bond‐assisted relaxation. Computational analysis confirms a compact ICT state with charge transfer from the triazole donor to the carbonyl acceptor. Z‐scan measurements demonstrate reverse saturable absorption, positive nonlinear refraction, and strong third‐order susceptibility, supported by hyperpolarizability calculations. The results establish hydrogen bond‐assisted ICT as the central mechanism, explained using both photophysical and nonlinear optical behavior, highlighting the potential of the molecule for applications in optical limiting and photonic devices.