Molecular Structure, Theoretical and Experimental Vibrational Spectroscopy, NBO Investigation, RDG, IRI, AIM Analyses, and NLO Study of 1‐[(E)‐2‐(5‐chloro‐2‐hydroxyphenyl) Hydrazine‐1‐ylidene] Naphthalen‐2(1H)‐one

ABSTRACT In this work, density functional theory (DFT) was employed to investigate the molecular structure and vibrational frequencies of [1‐[(E)‐2‐(5‐chloro‐2‐hydroxyphenyl) hydrazin‐1‐ylidene] naphthalen‐2(1H)‐one (5CHN)]. The spectroscopic characterization was carried out using experimental FT‐IR, 1 H NMR, and 13 C NMR spectroscopy. DFT calculations were performed using the B3LYP functional combined with the 6‐311G (d, p) basis set. Vibrational frequencies as well as 1 H and 13 C chemical shifts were computed at the same theoretical level and compared with the experimental data. Additionally, natural bond orbital (NBO) analysis, molecular electrostatic potential (MEP) mapping, frontier molecular orbital (FMO) analysis, and reactivity indexes were conducted and discussed. The UV–vis absorption spectrum, both in the gas phase and in chloroform solvent, was simulated using the TD‐DFT method, and the density of states (DOS) was also analyzed accordingly. The covalent and non‐covalent interactions within 5CHN were explored through reduced density gradient (RDG) analysis, interaction region indicator (IRI) analysis, and atoms in molecules (AIM) theory. Furthermore, Mulliken, Natural Population Analysis (NPA), and Hirshfeld atomic charges were determined. Nonlinear optical (NLO) properties were also evaluated.