Hydrogen bonding and conformational change of 2,2′-pyridil in polyhydric solvents

Abstract

Hydrogen bonding interaction of di-2-pyridyl diketone (2,2′-pyridil) with polyhydric solvents such as ethylene glycol, propane-1,2-diol, glycerol, and water has been studied by means of u.v. absorption spectroscopy. From the drastic change of the ππ* bands in these solvents compared with those in other solvents in which 2,2′-pyridil takes the skewed structure, it has been suggested that the hydrogen bonding causes geometrical change in 2,2′-pyridil with variation of the carbonyl–carbonyl dihedral angle. Regardless of solvents, the geometry in the lowest triplet state is deduced from the phosphorescence spectra to be the skewed structure.