Computational study of the intramolecular proton transfer reactions of dipicolinic acid (pyridine-2,6-dicarboxylic acid) and its dimers

The intramolecular proton transfer (IPT) reaction and dimerization processes of dipicolinic acid (DPA) have been investigated using density functional theory (DFT) at the B3LYP/6-31G++(d) basis set level. The influence of the solvent on the zwitterion -to- neutral transition of DPA was examined using the continuum model (CPCM) with different dielectric constants (ε = 4.9, CHCl3; ε = 7.42, THF; ε = 32.63, CH3OH; ε = 78.39, H2O). The intramolecular proton transfer reaction occurs more readily in the gas phase than solution. Results also show that the stability of DPA dimers in the gas phase is directly affected by the hydrogen bond angle and electrostatic potential (ESP) value in the dimer structure.