Synthesis, Characterization, Physico-Chemical and DFT Studies of Potential Organic NLO Materials: Experimental and Theoretical Combined Study

1-(2,4-difluorobenzyl)-2-(2,4-difluorophenyl)-6-methyl-1H-benzo[d]imidazole(1) and 1-(3-(tri fluoromethyl)benzyl)2-(4-(trifluoromethyl)phenyl)-6-methyl-1H-benzo[d]imidazole (2) were synthesized and characterized using FT-IR,H-1-NMR,C-13-NMR and mass spectral studies. UV-Vis absorption and emission spectral studies were studied in hexane and ethanol medium. In addition to these, density functional theory studies (DFT/B3LYP/6-31G(d,p)) has also been carried out to compute the relevant electronic properties of the molecules and the observed theoretical results of the non-zero dipole moments, polarizability and hyper polarizability values which show that these types of molecules are promising candidates for applications in various non-linear optical (NLO) devices because of their significant values of the molecular hyperpolarizabilities and fine microscopic NLO behaviour. The high NLO responses of the donor-acceptor -conjugated molecules are related to the intramolecular charge transfer excited state. The results confirmed that the synthesized benzimidazoles can act as a non-linear optical material and changing the substituents in the aldehydic phenyl ring will change the energy gap in the molecule.