Theoretical Study of Pyridine -2- Amidoxime by Semi-Empirical Methods

D.K. Kumar et al.

Centre of Research for Chemical Sciences, Post Graduate Department of Chemistry, S.M.S. Government Model Science College, Gwalior (India)

X-ray diffraction data shows that pyridine-2-amidoxime, C6H7N3O, crystals are monoclinic. The compound is stable and is used as ligand to form complexes with transition metal ions. Experimental data of this compound is available which promoted us to study its theoretical parameters like bond length, bond angle, electron density, and general thermodynamic parameters etc using AM1, PM3, MNDO and MNDO-d semi-empirical methods. For bond lengths, the correlation coefficient obtained for AM1, PM3, MNDO and MNDO-d methods are 0.672, 0.893, 0.571 and 0.571 respectively. Out of the four semi-empirical methods PM3 produces most satisfactory correlation (cc=0.893) between experimental and calculated bond length. In the case of bond angles, correlation coefficients are 0.603, 0.254, 0.336 and 0.336 for AM1, PM3, MNDO and MNDO-d methods respectively. Thus AM1 method gives most satisfactory correlation (cc=0.603). Electronic charge and atom electron density data reveal the coordination sites of pyridine-2-amidoxime when it forms complexes with transition metal ions. Out of two nitrogen atoms azo-methine nitrogen carries more electron density. Thus, performance of Semi-empirical AM1, PM3, MNDO, MNDO-d methods has been tested to find the best auxiliary tool for geometry & electron density.

Pyridine-2-amidoxime; semi-empirical methods; AM1; PM3; MNDO; MNDO-d; correlation coefficient