Dual experimental and computational approach for study of optical and nonlinear optical properties of naphthalimide derivatives

The synthesis and characterization of naphthalimide Bis-Schiff bases (5a) and (5b) using a dual approach comprising computational and experimental techniques. The synthesized Bis-Schiff base compounds (5) were successfully characterized using UV–visible, fluorescence, Fourier-transform infrared (FT-IR), and 1H nuclear magnetic resonance (NMR) spectroscopies. In ethanol solvent, the experimental absorption peak was observed at 339 nm for compound 5a and at 341 and 433 nm for compound 5b. The computationally calculated absorption peak for compounds 5a was at ~ 343 nm and those for 5b were at 337 and 425 nm. The fluorescence emission bands of compounds 5a and 5b were observed at 383 and 549 nm, respectively, at an excitation wavelength of 338 nm. Additionally, quantum chemical studies of the synthesized compounds were performed to study their molecular structures linear optical and nonlinear optical (NLO) response properties. The molecular geometries were optimized to minimum energy ground state. Compounds 5a and 5b showed third-order NLO polarizability amplitudes of 391.8 × 10–36 and 489.0 × 10–36 esu, respectively, which are significantly larger than those of some standard NLO compounds. The results indicate that the Bis-Schiff base is a promising molecule for use in electronic and optoelectronic devices and biosensors.