Dipole moment, spectroscopic, and theoretical study of di-2-pyridyl sulphones

Abstract

The electric dipole moments and u.v. and i.r. spectra of di-2-pyridyl sulphone and of its p-nitro- and p,p′-dinitroderivatives have been measured and analysed. Dipole moment data, in conjunction with theoretical calculations of conformational energy (CNDO/2 and EHT), show that these molecules prefer a single conformation in which the pyridine ring planes are perpendicular to the CSC plane and the nitrogen atoms are located anti to each other. The main features of the u.v. and i.r. spectra of the compounds examined, together with those of diphenyl sulphone, have been surveyed. The electronic transitions have been interpreted in terms of CNDO/S-Cl calculations for the most favoured conformation. Vibrational assignments for the characteristic SO₂ group frequencies are also presented.