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

Abstract

The crystal structure of bis(1-methylisonicotinate)hydrogen perchlorate, (MIN) 2H·ClO 4, has been studied by X-ray diffraction, DFT calculations, FT-IR, Raman, 1H and 13C NMR spectra. The crystals are monoclinic, space group P2 1 /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·ClO 4 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·ClO 4 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).