Spectroscopic, structural and theoretical investigation of bis(4-trimethylammoniumbenzoate) hydroiodide hydrate

Abstract

The structure of bis(4-trimethylammoniumbenzoate) hydroiodide hydrate 1 has been studied by X-ray diffraction, B3LYP/6–311G(d,p) calculations, FTIR, Raman and NMR spectroscopic techniques. The crystal is polar in monoclinic space group Cc. Two 4-trimethylammoniumbenzoate moieties are joined by a short and asymmetric hydrogen bond of 2.45(2)Å. Water molecules are gradually released from the structure, causing shifts in the position of iodine anions, which induces their disorder. The water molecule interacts with 4-trimethylammoniumbenzoate moiety and iodide anion via two O(3)–H(1)⋯O(1) and O(3)–H(2)⋯I(1) hydrogen bonds of lengths 2.70(3) and 3.51(1)Å. Hydrogen bonds in theoretically predicted structures of 2 and 3 (in vacuum), and 4, 5 (in DMSO) optimized by the B3LYP/6-311G(d,p) approach are slightly longer than in crystal 1. The FTIR spectrum of 1 shows a broad and intense absorption in the 1500–400cm−1 region, typical of short hydrogen bonds assigned to the νas(OHO)+γ(OHO) vibrations. The correlations between the experimental 13C and 1H chemical shifts (δexp) of the investigated compound in DMSO and the GIAO/B3LYP/6-311G(d,p) magnetic isotropic shielding constants (σcalc) calculated by using the screening solvation model (COSMO) are linear, δexp=a+b σcalc, and they well reproduce the experimental chemical shifts.