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Hydrogen Bonding in the 2, 2'-Bipyridinium Salt of 1, 2, 4, 5-Benzenetetracarboxylic Acid (Pyromellitic Acid)

The 2, 2'-bipyridinium salt of pyromellitic acid (PMA, 1, 2, 4, 5-benzenetetracarboxylic acid), 2, 2'-bipyridinium hemi/1, 2, 4, 5-benzenetetracarboxylate(2-)/ hemi(1, 2, 4, 5-benzenetetracarboxylic acid), C_10H_8N_2H^+ˇ1/2/C_6H_2(COO)_4H_2/^2-ˇ1/2/C_6H_2(COO)_4H_4/, has been prepared and studied by X-ray diffraction and IR spectroscopy. 2, 2'-Bipyridine acts as a proton sponge by accepting a proton from pyromellitic acid. The transfer of protons results in strong asymmetric intramolecular hydrogen bonds ; H(N)ˇˇˇN 2.603 (2) Ĺ in the bipyridinium cation, which has a syn conformation, and H(O)ˇˇˇO 2.396 (2) Ĺ in the pyromellitate anion. The N-HˇˇˇN hydrogen bond is part of a three-centre hydrogen bond with a carbonyl group of the neutral pyromellitic acid ; N-HˇˇˇN/O with an NˇˇˇO distance of 2.805 (2) Ĺ. Each neutral PMA molecule is connected by hydrogen bonds to two cations and four anions forming a two-dimensional network with plane indices (112). The IR spectrum also suggest the presence of strong hydrogen bonds.

Hydrogen Bonding; 2; 2

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