Molecular structure and electric properties of some pyridine and pyridine-N-oxide derivatives

Dipole moments of molar Kerr constants of several pyridine and pyridine-N-oxide derivatives are studied both experimentally and by AM1 and PM3 quantum chemical methods. To the authors' knowledge, this is the first application of AMI and PM3 techniques to the calculation of Kerr constants. Based on the experimental data, the quantum chemical methods are found to satisfactorily describe the electric properties of the pyridine compounds. It is shown that the mesomeric moment correlates with the pi-charge on the carbon atom nearest to the substituent, while the overall (mesomeric plus inductive) substituent effect correlates with the total charge on the atom. (C) 1998 Elsevier Science B.V. All rights reserved.