The 1:2:1 adduct of DABCO dication, hydrogen squarate and water molecules studied by X-ray diffraction and FTIR spectroscopy

The molecular structure of 1:2:1 adduct of diprotonated 1,4-diazabicyclo[2.2.2]octane, (DABCO), hydrogen squarates (HSQ(-)) and water (1) has been characterized by single-crystal X-ray diffraction and infrared spectroscopy. The crystals of 1 are orthorhombic, space group Pnma. The non-equivalent HSQ(-) anions are bonded into zigzag chains (alpha-chain) by two short O-H center dot center dot center dot O hydrogen bonds of 2.485(2) and 2.509(2) angstrom. and additionally H-bonded by water molecules linking the zigzag chains into ribbons. The diprotonated DABCO cations are located between the ribbons and interact with HSQ(-) anions by the N-H center dot center dot center dot O trifurcated hydrogen bonds. The FTIR spectrum shows a very broad absorption in the 1740-550 cm(-1) region, typical of short hydrogen bonds and it is attributed to the nu(OHO) and gamma(OHO) vibrations. The second derivative spectrum distinguishes the nu C-0 and gamma C-C modes assigned to the pi-delocalized squaric acid ring. (C) 2011 Elsevier B.V. All rights reserved.