A theoretical study of the conformation, basicity and NMR properties of 2,2′-, 3,3′- and 4,4′-bipyridines and their conjugated acids

A theoretical study at the B3LYP/6-311++G(d,p) level has been carried out on 2,2′-, 3,3′- and 4,4′-bipyridines, as well as on their monoprotonated and diprotonated forms. The geometries, torsion angles, and the energies of the minima and transition states have been calculated with good agreement with previous calculations and with most of the scarce available data. The absolute shieldings were calculated on these geometries using the GIAO approximation and transformed into chemical shifts using previously established relationships.