Hydrogen bonds and conformational analysis of bis(1-methylisonicotinate) hydrochloride monohydrate by X-ray diffraction, vibrational spectra and B3LYP calculations

In the crystal structure of bis(1-methylisonicotinate) hydrochloride monohydrate, (MIN)2H·Cl·H2O, 1-methylisonicotinate betaines are hemiprotonated and form a homoconjugated cation through a short asymmetric O·H·O hydrogen bond of length 2.456(3) Å. Water molecules and Cl− anions are linked alternatively by hydrogen bonds of lengths 3.202(3) and 3.282(2) Å into planar zigzag chains along the [c] direction. The Cl− anion additionally interacts electrostatically with two positively charged nitrogen atoms of the neighboring MIN molecules. The most stable conformers of (MIN)2H·Cl·H2O, (MIN)2H·Cl, (MIN)2H·H2O and (MIN)2H have been analyzed by the B3LYP/6-31G(d,p) calculations in order to determine the influence of the anion and water molecule on the hydrogen bond in the homoconjugated MIN·H·MIN unit. The FTIR spectrum of (MIN)2H·Cl·H2O shows a broad and intense absorption in the 1500–400 cm−1 region, typical for short hydrogen bonds. The bands at 3416 and 3378 cm−1 confirm the presence of medium–strong hydrogen bonds between water molecules and Cl− anions.