Synthesis, characterization, crystal structure and solution studies of a novel proton transfer (charge transfer) complex of 2,2′-dipyridylamine with 2,6-pyridine dicarboxylic acid

• A proton transfer compound is synthesized and characterized by spectral techniques.
• The structural investigations confirmed hydrogen bonds and π–π stacking interactions.
• The equilibrium constants system was calculated by the potentiometric pH titration method.
• The solution potentiometric studies supported the results obtained from the solid state studies.

Reaction between 2,2′-dipyridylamine (DPA) and 2,6-pyridine dicarboxylic acid (dipicolinic acid, dipicH2), in water results in the formation of a proton transfer or charge transfer (CT) complex, (DPAH)+(dipicH)−·H2O, 1. The characterization was performed using 1H NMR and FTIR spectroscopy, elemental analysis and X-ray crystallography. The crystal system is triclinic with space group P1. The structural investigations exhibit that the hydrogen bonds and π–π stacking interactions stabilize the crystal structure of proton transfer complex. The protonation constants of 2,6-pyridine dicarboxylic acid, 2,2′-dipyridylamine and the equilibrium constants for dipic–DPA (1:1) proton transfer system were calculated by potentiometric pH titration method using Hyperquad2008 program. The stoichiometries of the proton transfer species in solution was in agreement with the solid state result.

Figure optionsDownload as PowerPoint slide