N-(1H-Benzo[d]imidazol-2-yl)-1-(3-substituted phenyl) methanimines as optoelectronic and nonlinear optical materials: spectroscopic and computational approaches

The negative environmental impact of fossil fuel and the ever-increasing need for renewable energy materials necessitate a rigorous search for optoelectronic materials. Photon reabsorption due to a small Stokes shift limits the light-emitting potentials of many optical materials. In this research, two benzimidazole Schiff bases, 3-(((1H-benzo[d]imidazol-2-yl)imino)methyl)phenol (1) and N-(1H-benzo[d]imidazole(-2-yl)-1-(3-nitrophenyl))methanimine (2), were synthesized via one-pot single-step condensation and characterized using spectrometric (¹H NMR, ¹³C NMR, HRMS and FTIR) techniques. The optoelectronic, nonlinear optical (NLO), adsorption properties and natural bond orbital (NBO) analysis of 1 and 2 were explored using spectroscopic, density functional theory (DFT) and Monte Carlo (MC) simulation approaches. The absorption, light-harvesting efficiency (LHE) and fluorescence properties were studied in solution. Static and dynamic first and second hyperpolarizabilities and parameters for power conversion efficiency (V_oc and ΔG_inj) were computed using the time-dependent DFT/B3LYP/6–311++G(d,p) method. Hyperpolarizabilities were compared with those of urea (standard). The binding properties of 1 and 2 on TiO₂ (anatase 101) were investigated using the MC method. The calculated electronic properties agree with the experimental results. The compounds display large Stokes shifts (> 200 nm), appreciable quantum yields and low band gaps. High LHE (87%) and large hyperpolarizabilities were obtained for 2. Dye 2 displayed a high V_oc, while 1 exhibited a more negative ΔG_inj. The negative adsorption energies of the 1-TiO₂ (− 52.9 kJ/mol) and 2-TiO₂ (– 57.1 kJ/mol) interfaces indicate their strong binding interactions with anatase. NBO analysis revealed that conjugation and hyperconjugation were the primary interactions responsible for the stabilization of the dyes. These dyes have the potential for use in optoelectronic and nonlinear optical applications.