Synthesis, spectral, crystal structure, linear and NLO properties of quinoline Schiff base: Combined experimental and DFT calculations

The study explores the optical and nonlinear optical (NLO) properties of 2-imino [N- (N'-amido phenyl)] chromophore, a compound with potential in photonic applications. The compound was produced and crystallized using a slow evaporation approach using ethanol as solvent, and spectroscopy techniques were used to characterize it. The molecular structure of the compound was determined using FT-IR and NMR spectral methods. The crystal's structure was found via SCXRD analysis, showing a monoclinic system with a P2₁/c space group. The UV–Vis-NIR spectrum showed good transmittance over the visible region, with lower cutoff wavelengths of 338 nm and optical band gaps of 3.17 eV. The grown crystal exhibited a χ3 value of 2.89 × 10⁻⁸esu, making it valuable for non-linear optical applications. Quantum computational analysis was used to investigate molecular architectures, topologies, and molecule-level third-order NLO response. The compound exhibited a planar molecular geometry, with an average third-order NLO polarizability of 69.65 × 10⁻³⁶ esu. The study also examined quantum chemically computed UV–visible spectra and electron density difference maps, as well as the density of states and molecular electrostatic potentials. In addition to highlighting the relationship between structure and characteristics, our current study of synthesized compounds highlights the potential of photonic applications.