Quantum chemical prediction of nonlinear optical properties in Benzoxazine derivatives with symmetrical double acceptors: Insights from gas-phase, implicit solvent, and dynamics frequency studies

The benzoxazine class of molecules offers promising potential for optical and nonlinear optical (NLO) properties, as their conjugated structures and electron-donating/withdrawing groups can be fine-tuned to enhance optical properties. The symmetrical double acceptor groups are introduced into central double donor benzoxazine core, and their NLO responses are thoroughly investigated using DFT. Among the designed compounds, DBB4 shows the highest performance with linear isotropic ([Formula: see text] and anisotropic ([Formula: see text] polarizabilities of [Formula: see text][Formula: see text]esu and [Formula: see text][Formula: see text]esu, respectively. The third-order NLO polarizability [Formula: see text] for DBB4 was found to be [Formula: see text][Formula: see text]esu, [Formula: see text] times greater than para-nitroaniline. To assess the solvent effects, polar and nonpolar implicit solvation models were applied to DPB4 and DBB4 for comparative study, revealing that the PCM model tends to overestimate NLO properties compared to gas phase calculations. TD-DFT analysis for DBB4 indicates the lowest transition energy of 2.81[Formula: see text]eV and the smallest HOMO–LUMO energy gap of 3.61[Formula: see text]eV for DBB4. The UV–Visible absorption spectra exhibit a red-shift at 440[Formula: see text]nm, while IR bands at 1708[Formula: see text]cm[Formula: see text] and 1532[Formula: see text]cm[Formula: see text] confirm presence of nitro group. The charge transfer properties are supported by molecular electrostatic and electron density difference maps. The topological analysis further reveals efficient electronic charge delocalization consolidating the role of DBB4 as a high-performance NLO candidate. Our findings underscore the strong potential of our designated derivatives as a next-generation NLO material for photonic and optoelectronic device applications.