Density functional investigation of the molecular structures, vibrational spectra and molecular properties of sulfonated pyridyl imine ligands and their palladium complexes

The equilibrium geometries and harmonic vibrational frequencies of the sulfonated pyridyl-imine ligands (L1–L6) and their palladium (II) complexes (C1–C6) were calculated using density functional theory at the B3LYP level. The complete vibrational assignments of ligand L1, and its palladium (II) complex C1, were performed based on the total energy distribution (TED) of the vibrational modes and the calculated isotopic frequency shifts. er to investigate the electronic properties of ligands and complexes, quantum chemical parameters, such as the highest occupied molecular orbital energy (εHOMO), the lowest unoccupied molecular orbital energy (εLUMO), energy gap (Δε), dipole moment (μ), electronegativity (χ) and hardness (η) were calculated. Chemical hardness was used to predict their relative stability and reactivity.