A DFT study of molecular structures and tautomerizations of 2-benzoylpyridine semicarbazone and picolinaldehyde N-oxide thiosemicarbazone and their complexations with Ni(II), Cu(II), and Zn(II)

The structure optimizations of picolinaldehyde N-oxide thiosemicarbazone (Hpiotsc), 2-benzoylpyridine semicarbazone (H2BzPS), their imino tautomers and their complexes with Ni(II), Cu(II), and Zn(II) were carried out using DFT calculations. The structures of Hpiotsc and H2BzPS ligands, transition states of their tautomerizations were obtained at the B3LYP/6-31+G(d,p) level and their thermodynamic properties were derived from the frequency calculations at the same level of theory. The B3LYP/LANL2DZ-optimized structures of Hpiotsc and H2BzPS complexes with Ni(II), Cu(II), and Zn(II), and the thermodynamic properties of their complexations derived from the B3LYP/LANL2DZ-frequency calculations were obtained. The B3LYP/LANL2DZ-optimized geometrical parameters for the [Ni(Hpiotsc)(2)](2+), [Cu(Hpiotsc).Cl-2], and [Zn(Hpiotsc).Cl-2] complexes show good agreement with their corresponding X-ray crystallographic data.