Crystal and molecular structure, hydrogen bond and electrostatic interactions of bis(1-methylisonicotinate)hydrogen perchlorate studied by X-ray diffraction, DFT calculations, FT-IR, Raman and NMR spectroscopes

The crystal structure of bis(1-methylisonicotinate)hydrogen perchlorate, (MIN)2H·ClO4, has been studied by X-ray diffraction, DFT calculations, FT-IR, Raman, 1H and 13C NMR spectra. The crystals are monoclinic, space group P21/n, with a pair of MIN molecules bridged by a short asymmetrical O·H·O hydrogen bond of 2.461(5) Å. The COO groups are twisted by 80.55° with respect to the plane of the pyridine ring. The ClO 4 - anion interacts electrostatically with the positively charged nitrogen atoms of the neighbouring MIN molecules. The most stable conformer of isolated (MIN)2H·ClO4 and two homoconjugated cations, (MIN)2H, have been analyzed by the B3LYP/6-31G(d,p) calculations in order to determine the influence of the anion on the hydrogen bonds in MIN·H·MIN unit. The FT-IR spectrum of the (MIN)2H·ClO4 shows a broad and intense absorption in the 1500–400 cm−1 region, typical of short hydrogen bonds. The isotopic ratio, νOHO/νODO, is close to unity, indicating that the hydrogen bond is acentric (pseudo-type A).