Hydrogen-Bonding in the Structures of the Hydrated Proton-Transfer Compounds of Isonipecotamide with the Isomeric Indole-2- and Indole-3-Carboxylic Acids |
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Authors: | Graham Smith Urs D Wermuth |
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Institution: | (1) Faculty of Science and Technology, Queensland University of Technology, G.P.O. Box 2434, Brisbane, QLD, 4001, Australia;(2) School of Biomolecular and Physical Sciences, Griffith University, Nathan, QLD, 4111, Australia |
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Abstract: | Abstract The structures of two hydrated proton-transfer compounds of 4-piperidinecarboxamide (isonipecotamide) with the isomeric heteroaromatic
carboxylic acids indole-2-carboxylic acid and indole-3-carboxylic acid, namely 4-carbamoylpiperidinium indole-2-carboxylate
dihydrate (1) and 4-carbamoylpiperidinium indole-3-carboxylate hemihydrate (2) have been determined at 200 K. Crystals of both 1 and 2 are monoclinic, space groups P21/c and P2/c, respectively with Z = 4 in cells having dimensions a = 10.6811(4), b = 12.2017(4), c = 12.5456(5) ?, β = 96.000(4)° (1) and a = 15.5140(4), b = 10.2908(3), c = 9.7047(3) ?, β = 97.060(3)° (2). Hydrogen-bonding in 1 involves a primary cyclic interaction involving complementary cation amide N–H···O(carboxyl) anion and anion hetero N–H···O(amide)
cation hydrogen bonds graph set R22(9)]. Secondary associations involving also the water molecules of solvation give a two-dimensional network structure which
includes weak water O–H···π interactions. In the three-dimensional hydrogen-bonded structure of 2, there are classic centrosymmetric cyclic head-to-head hydrogen-bonded amide–amide interactions graph set R22(8)] as well as lateral cyclic amide-O linked amide–amide extensions graph set R42(8)]. The anions and the water molecule, which lies on a twofold rotation axis, are involved in secondary extensions. |
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