Nonlinear optical and quantum chemical studies of Palladium benzimidazole Schiff base complex

This article presents the linear and nonlinear optics and density functional theory studies of a Palladium complex with a benzimidazole-based Schiff base. Linear absorption of the complex has been studied using a UV–Vis absorption spectrometer. Optical nonlinearity and thereby the optical limiting performance of the complex has been deliberated experimentally using a Z-scan method with a continuum wave laser of wavelength 532 nm. The NLO investigation of the complex demonstrated significant nonlinear absorption (β_eff = 4.64–27.23 × 10⁻² cm/W) with an imaginary part of nonlinear optical susceptibility of the third-order (Imχ⁽³⁾ = 1.28–7.49 × 10⁻⁵ esu) and nonlinear refraction (n₂ = 5.46–12.3 × 10⁻⁷ cm²/W) with real part of nonlinear optical susceptibility of the third-order (Reχ⁽³⁾ = 3.55–8.00 × 10⁻⁵ esu). The large nonlinear absorption displayed superior optical power limiting characteristics with a threshold and clapping level of 115 W/cm² and 35 W/cm²respectively. Theoretical studies are performed for Palladium benzimidazole Schiff base complex within Density Functional Theory (DFT) framework, using hybrid exchange-correlation B3LYP with basis set LANL2DZ. DFT-based descriptors are computed viz. energy gap between HOMO-LUMO, electronegativity, electrophilicity index, molecular hardness, and softness. Result reveals that the bond length between Pd–O is small as compared to Pd–Cl and Pd–N.