Synthesis and structural analysis of novel indole derivatives by XRD, spectroscopic and DFT studies

Abstract The indole derivatives have been getting immense interest to possess diverse applications in different fields. In present investigation, four novel indole based derivatives namely; 4,6-dimethoxy-2,3-diphenyl-1H-indole 3a, 4,5,6-trimethoxy-2,3-diphenyl-1H-indole-7-carbaldehyde 4b, N-(3‴-chlorophenyl) (4,6-dimethoxy-2,3-diphenyl-1H-indol-7-yl)methanimine 6a and N-(3‴-chlorophenyl) (4,5,6-trimethoxy-2,3-diphenyl-1H-indol-7-yl)methanimine 6b were synthesized and characterized by 1H NMR &13C NMR to resolve their molecules structures. To provide additional spectroscopic support, FT-IR and UV–Visible techniques were executed for characterization of entitle synthesized molecules. The X-ray diffraction (XRD) studies have been performed to evaluate bond angles, bond lengths, unit cells and specific space groups. Ancillary, density functional theory (DFT) study at B3LYP level of theory and 6-311 + G(d,p) basis set to investigate the optimized geometry, FT-IR vibrational analysis, frontier molecular orbital (FMO), molecular electrostatic potential (MEP) and nonlinear optical (NLO investigations. The results of single crystal studies and experimental spectroscopic studies were compared with computational insights and found in good agreement. Global reactivity parameters were estimated using energy values of FMOs. The UV–Vis spectral analysis was executed by time dependent DFT (TDDFT) at B3LYP/6-311 + G(d,p) level of theory. Two-state model and urea molecule comparative analysis evident that 3a, 4b, 6a and 6b comprise of fine NLO properties. We hope that this synergistic experimental-computational study may provide new ways for the utilization of investigated molecules for NLO associated hi-tech applications.