Abstract
The conformational properties of bipyridine cardiotonics were investigated by means of quantum chemical (AM1(Austin Model 1)) calculations. The calculations for the tautomeric and ionic structures of 3, 4'-dipyridin-6(1H)-one (1), the basic structure for bipyridine cardiotonics, showed that the equilibrium conformations in the ionic structures are more planar than those in the neutral structures and that the rotational barrier of the cationic pyridone structure is characteristically higher compared to those of the pyridinol tautomer and 1'-hydro-3, 4'-bipyridinium cation. The difference in conformation between the well known cardiotonics, amrinone and milrinone, is more distinctive in the cationic structure, which is considered to be the usual structure in biological environments, than in the neutral structures.
