Experimental and theoretical investigation on N-(Naphthalen-5-yl)-N-phenyl benzamide organic single crystal toward its NLO applications

Nonlinear optical heterocyclic—organic single crystals of N-(Naphthalen-5-yl)-N-Phenyl benzamide (NNNPB) was synthesized using N-phenylnaphthalen-1-amine and benzoyl chloride. Single crystals of NNNPB resolved by X-ray diffraction technique and crystal reveal monoclinic arrangement among space group P21/n. The parameters of lattice of NNNPB molecule and unit cell proportions were a = 9.9798(11) Å, b = 13.2737(13) Å, c = 13.0321(13) Å & Volume = 1725.7(3) ų. The experimental as well as theoretical FT-IR & Raman spectral data verified the NNNPB molecules significant stretching vibration of the amide carbonyl (–C = O) function group. ¹H & ¹³C NMR spectral investigation was utilized to forecast the existence of proton and carbon in NNNPB compound. TGA and DTA study verified the various phases of the formed crystals degradation and revealed that it is thermally stable up to 150 °C. Quantum chemical calculations were carried out through density functional theory. The topological surface analysis of NNNPB were analysed through ELF and LOL. The virtual second-harmonic generation efficiencies deliberated by Kurtz- Perry powder manner along with are found to be 3.45 period better against potassium dihydrogen phosphate. The UV–vis spectral analysis confirmed the electronic excitations of NNNPB, showing high transparency in the deep ultraviolet region below 230 nm and above 320 nm. This optical behavior indicates its potential application in advanced laser systems. The calculated static first-order hyperpolarizability (β₀ = 1.41 × 10² a.u.) and second-order hyperpolarizability (γ_o = 4.14 × 10⁴ a.u.) reveal a strong nonlinear optical (NLO) response. Furthermore, at dynamic frequencies, the hyperpolarizability value increases to 8.73 × 10⁴ a.u., demonstrating enhanced NLO performance. These results suggest that NNNPB is a promising candidate for optical technologies, particularly for improving second-harmonic generation and dc-Kerr effects.