Spectroscopic and structural elucidation of 3,4-diaminopyridine and its hydrogentartarate salt: Crystal structure of 3,4-diaminopyridinium hydrogentartarate dihydrate

The novel 3,4-diaminopyridinium hydrogentartarate dihydrate has been synthesized and its structure and properties elucidated in detail spectroscopically, thermally and structurally, using single crystal X-ray diffraction, linear-polarized solid state IR-spectroscopy, UV-spectroscopy, TGA, DSC, DTA and positive and negative ESI-MS. Quantum chemical calculations were used to obtain the electronic structure, vibrational data and electronic spectra. The studied compound crystallizes in the noncentrosymmetric space group P212121 and exhibits a 3D network with molecules linked with participation of cations, anions and solvent molecules. Hydrogentartarates form infinite chains through strong OCOH…OCO interaction. The effects of N1 protonation on the optical and magnetic properties of 3,4-diaminopyridine are elucidated by comparison with the data of the neutral form.