Solvent Effects on the Photophysical Mechanism of a 2’-Hydroxybenzochalcone Derivative with TICT Characteristics

Abstract 2’-Hydroxybenzochalcone derivatives serve as solid-state laser materials and promising high-sensitivity fluorescent probes with TICT and ESIPT dual photophysical pathways, yet their solvent-dependent mechanisms remain ambiguous. Herein, synthesized 2’-hydroxy-4-methoxybenzochalcone (HMBC) was systematically explored via spectroscopic characterization and theoretical calculations in three aprotic solvents of varied polarity. Increasing solvent polarity induces a gradual red shift in the absorption peaks, and dual fluorescence emission is observed with a significantly large Stokes shift for the long-wavelength band. DFT and TD-DFT results reveal that the initial hydroxyl proton configuration plays a critical role in directing the excited-state relaxation of HMBC. In combination with the extremely low fluorescence quantum yields measured in dilute solution, the excited-state behavior of HMBC was shown to be predominantly governed by TICT rather than ESIPT. Moreover, a clear correlation among solvent polarity, excited-state molecular torsion, charge-transfer character, and luminescence behavior was established. This work offers guidance for the rational design of advanced fluorescent probes toward environmental and biomedical detection based on 2’-hydroxylchalcone template.