Density functional modelling studies of chloride-substituted Schiff bases as corrosion inhibitors: Optimized geometries, atomic charges, solvent and non-linear optical effects

The anti-corrosive properties, optimized geometrical structures, atomic charges, molecular electrostatic potential (MEP) surfaces and non-linear optical (NLO) effects of some chloride-substituted Schiff bases salicylaldimine (R), N-(2-chlorophenyl)salicyaldimine (2Cl–R), N-(3-chlorophenyl)salicyaldimine (3Cl–R) and N-(4-chlorophenyl)salicyaldimine (4Cl–R) have been investigated by using density functional modelling calculations. The quantum chemical parameters, such as the highest occupied molecular orbital, the lowest unoccupied molecular orbital, gap energy and other parameters, including electronegativity, global hardness, the total charges on the whole molecules and the total energies have been calculated and discussed to obtain information about the relationships between the molecular and electronic structures of the studied inhibitors and their experimental corrosion inhibition efficiencies. The linear polarizability (α), and the firstorder hyperpolarizability (β) have been also predicted by the density functional theory (DFT) with different base sets 6-31G(d), 6-31+G(d,p), 6-31++G(d,p), 6-311+G(d) and 6-311++G(d,p) for investigating the effects of basis sets on the NLO properties.