Proton‐transfer compounds of isonipecotamide with the aromatic dicarboxylic acids 4‐nitrophthalic, 4,5‐dichlorophthalic, 5‐nitroisophthalic and terephthalic acid
The structures of the 1:1 proton‐transfer compounds of isonipecotamide (piperidine‐4‐carboxamide) with 4‐nitrophthalic acid [4‐carbamoylpiperidinium 2‐carboxy‐4‐nitrobenzoate, C6H13N2O8 +·C8H4O6 −, (I)], 4,5‐dichlorophthalic acid [4‐carbamoylpiperidinium 2‐carboxy‐4,5‐dichlorobenzoate, C6H13N2O8 +·C8H3Cl2O4 −, (II)] and 5‐nitroisophthalic acid [4‐carbamoylpiperidinium 3‐carboxy‐5‐nitrobenzoate, C6H13N2O8 +·C8H4O6 −, (III)], as well as the 2:1 compound with terephthalic acid [bis(4‐carbamoylpiperidinium) benzene‐1,2‐dicarboxylate dihydrate, 2C6H13N2O8 +·C8H4O4 2−·2H2O, (IV)], have been determined at 200 K. All salts form hydrogen‐bonded structures, viz. one‐dimensional in (II) and three‐dimensional in (I), (III) and (IV). In (I) and (III), the centrosymmetric R 2 2(8) cyclic amide–amide association is found, while in (IV) several different types of water‐bridged cyclic associations are present [graph sets R 4 2(8), R 4 3(10), R 4 4(12), R 3 3(18) and R 6 4(22)]. The one‐dimensional structure of (I) features the common `planar' hydrogen 4,5‐dichlorophthalate anion, together with enlarged cyclic R 3 3(13) and R 4 3(17) associations. In the structures of (I) and (III), the presence of head‐to‐tail hydrogen phthalate chain substructures is found. In (IV), head‐to‐tail primary cation–anion associations are extended longitudinally into chains through the water‐bridged cation associations, and laterally by piperidinium–carboxylate N—H...O and water–carboxylate O—H...O hydrogen bonds. The structures reported here further demonstrate the utility of the isonipecotamide cation as a synthon for the generation of stable hydrogen‐bonded structures. An additional example of cation–anion association with this cation is also shown in the asymmetric three‐centre piperidinium–carboxylate N—H...O,O′ interaction in the first‐reported structure of a 2:1 isonipecotamide–carboxylate salt.
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Document Type: Research Article
Publication date: July 15, 2011