Derivatives of azacalix[3](2,6)pyridine are strong neutral organic superbases: a DFT study.

The gas phase basicities and pKa values in acetonitrile of azacalix[3](2,6)pyridine and its derivatives are determined by the B3LYP DFT method. It is found that all compounds of this series are neutral organic superbases. The proton attacks the inner pyridine N(sp2) atom, thus forming a bifurcated intramolecular hydrogen bond. The most powerful superbase is provided by the hexakis(dimethylamino) derivative of the title compound. Its gas phase proton affinity is 296.6 kcal mol-1, its basicity is 291.3 kcal mol-1, and its pKa(MeCN) is 30.9 units. [structure: see text]