Structural, spectroscopic and theoretical studies of short OHO hydrogen bonds in 2:1 complexes of 1-methyl-6-oxyquinolinium betaine with mineral acids

Authors:

• Piotr Barczyński,
• Anna Komasa,
• M. Ratajczak-Sitarz,
• Andrzej Katrusiak,
• Z. Dega-Szafran,
• M. Szafran

Abstract

Bis(1-methyl-6-oxyquinolinium) hydroiodide, (6QB)₂HI (1), has been characterized by X-ray diffraction, B3LYP calculations, FTIR and NMR spectroscopy. The complex crystallizes in triclinic P 1̄ space group. A pair of 6QB molecules is bridged by the O·H·O hydrogen bond of 2.450(2) . The anion I^- electrostatically interacts with both positively charged nitrogen atoms of the neighboring 6QB molecules. The isolated entities of the complex were analyzed at the B3LYP/6-311G(d,p) level of theory in order to determine the influence of counter ions (X^- = I ^-, Br^-, Cl^- and ClO4-) on the hydrogen bond in (6QB)₂HX (2-5). The FTIR spectra of (6QB)₂HI and (6QB)₂HClO₄ show a broad and intense absorption in the 1500-400 cm^-1 region, typical for short hydrogen bonds. Both ¹H and ¹³C chemical shifts depend on the acid-base stoichiometry and counter ions. © 2010 Elsevier B.V. All rights reserved.