Investigation of structural and thermodynamical properties of schiff bases and zinc complexes using quantum chemical computations

This research represents a theoretical study on the ligands derived from O-phenylenediamine and salicylaldehyde and their complexes with Zn2+ using B3LYP/6-311++G(d,p) and M06-2X/6-311++G(d,p) computational levels. the effect of substituents on the electronic and physicochemical properties of the thirteen complexes obtained with various electron-donating and electron- withdrawing substituted schiff base ( X: NO2, NH2, OCH3, H, F, Cl, Br, CN, OH, N(Me)2, CHO, CH3, CF3) and Zinc cation was investigated. The amounts of the charge transfer, interaction energy, formation enthalpy, Gibbs free energy, structural parameters and geometric properties were perdicted. The result show that the interaction between Zn2+ and ligands increases with the increase of electron-donating nature of substituents on the para position of the phenolic ring of the ligands. Since B3LYP resulted in more accurate results in comparison with M06-2X, then the B3LYP method was applied to the next calculations (NBO, AIM). According to the calculated interaction energies, the order of stability of the complexes was found to be as follows: LN(Me)2Zn > LNH2Zn > LOCH3Zn > LCH3Zn > LOHZn > LHZn> LBrZn > LClZn > LFZn > LCHOZn > LCF3Zn > LCNZn> LNO2Zn.