Solvatochromic analysis and DFT computational study of N-(hexyl)-N-(5-(3-hydroxynaphthyl-2-yl)-1,3,4-oxadiazol-2-yl)amine

Abstract

A detailed analysis of the molecular orbitals contained in the electronic transitions in the UV-spectra and a detailed synthesis and conformational study of N-(hexyl)-N-(5-(3-hydroxynaphthyl-2-yl)-1,3,4-oxadiazol-2-yl)amine (NOH) were conducted using the method of TD-DFT (B3LYP/6-311 + G (d,p)). All the theoretical results were found to be in line with the experimental values. For the most stable conformer, the optimized structure parameters (bond lengths, bond angles), vibrational modes and their assignments and were calculated using DFT/B3LYP functional and 6-311 +G(d,p) basis set. The basic vibrational modes were determined by PED, the experimental and computed values were found to support each other. The chemical shifts of 1H-NMR and 13C-NMR were specified using the method of GIAO and compared with the experimental chemical shifts. The frontier orbital energy gap, global chemical reactivity restrictive such as the chemical potential, global hardness, electronegativity, index of electrophilicity, global softness of the molecule were also studied. The Natural Bond Orbital (NBO) analysis was performed to find out the stability and strength of the molecule. Based upon the experimental solvent influence and the theoretical examinations, the long wavelength bands were attributed to π → π* transitions induced by HOMO–LUMO intra-molecular charge transfer from the naphthyl ring to the 1,3,4-oxadiazole. Beside these, electrophilic index, EHOMO (− 5.88 eV), ELUMO (1.89 eV) and energy gap (3.99 eV) were computed to investigate the bio activity, reactivity and stability of the NOH. Kamlet–Taft and Catalan solvatochromism of synthesized 1,3,4-oxadiazole derivative were discussed. The Kamlet–Taft and Catalan solvent parameter sets were used to determine the effect of specific and non-specific solvent–solute interactions on the shifts of UV–Vis absorption maxima.