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 at the B3LYP/LANL2DZ level of theory. Thermodynamic properties of tautomerizations of Hpiotsc and H2BzPS and complexations of their complexes derived from the frequency calculations at the same level were obtained. The B3LYP/LANL2DZ-optimized geometry parameters for the complexes of [[Ni(Hpiotsc)[subscript 2]][superscript 2+]], [Cu(Hpiotsc).Cl[subscript 2]] and [Zn(Hpiotsc).Cl[subscript 2]] show good agreement with their corresponding X-ray crystallographic data. Aryl semicarbazone derivatives have been studied for the development of new antituberculous agents. The quantitative structure activity relationship (QSAR) analysis for the antituberculous activity of the aryl semicarbazones were carried out in terms of the molecular hydrophobicity and indicator variables using the multiple linear regression method. The new definition for indicator variables based on the substituents of the aryl semicarbazones was proposed and employed in the QSAR analysis.