The energetics of protonation of pyridine and a series of its derivatives, as well as the energetics of formation of hydrogen-bended N...H...N homocomplexed cations in systems involving substituted pyridines and conjugate cationic acids were investigated by means of restricted Hartree-Fock (RHF) and Moller-Plesset (MP2) ab initio calculations. The Gaussian functional basis set 6-31G* was employed to calculate energy and Gibbs free energy of protonation and cationic homoconjugation in the gas phase. The proton potential of a homocomplexed pyridine cation exhibits a double minimum with a 5.7 kcal/mol energy barrier, which could be reduced to 2.7 kcal/mol by accounting for a thermodynamic correction factor. The calculated protonation energies, DeltaE(prot), and Gibbs free energies, DeltaG(prot), have been found to correlate well with the acid dissociation constants (expressed as pK(a) values) in acetonitrile. On the contrary, the calculated energies, DeltaE(BHB+), and Gibbs free energies, DeltaG(BHB)+, Of formation of the homocomplexes do not correlate with the cationic homoconjugation constant values (expressed as log(10) KBHB+) determined in acetonitrile.