Anhydrous 1:1 proton-transfer compounds of isonipecotamide with picric acid and 3,5-dinitrosalicylic acid: 4-carbamoylpiperidinium 2,4,6-trinitrophenolate and two polymorphs of 4-carbamoylpiperidinium 2-carboxy-4,6-dinitrophenolate

Three-dimensional hydrogen-bonded structures in the hydrated proton-transfer salts of isonipecotamide with the dicarboxylic oxalic and adipic acid homologues

The structures of the 1:1 hydrated proton-transfer compounds of isonipecotamide (piperidine-4-carboxamide) with oxalic acid, 4-carbamoylpiperidinium hydrogen oxalate dihydrate, C6H13N2O+·C2HO4−·2H2O, (I), and with adipic acid, bis(4-carbamoylpiperidinium) adipate dihydrate, 2C6H13N2O+·C6H8O42−·2H2O, (II), are three-dimensional hydrogen-bonded constructs involving several different types of enlarged water-bridged cyclic associations. In the structure of (I), the oxalate monoanions give head-to-tail carboxylic acid O—H...Ocarboxylhydrogen-bonding interactions, formingC(5) chain substructures which extend alonga. The isonipecotamide cations also give parallel chain substructures through amide N—H...O hydrogen bonds, the chains being linked acrossband downcby alternating water bridges involving both carboxyl and amide O-atom acceptors and amide and piperidinium N—H...Ocarboxylhydrogen bonds, generating cyclicR43(10) andR32(11) motifs. In the structure of (II), the asymmetric unit comprises a piperidinium cation, half an adipate dianion, which lies across a crystallographic inversion centre, and a solvent water molecule. In the crystal structure, the two inversion-related cations are interlinked through the two water molecules, which act as acceptors in dual amide N—H...Owaterhydrogen bonds, to give a cyclicR42(8) association which is conjoined with anR44(12) motif. Further N—H...Owater, water O—H...Oamideand piperidinium N—H...Ocarboxylhydrogen bonds give the overall three-dimensional structure. The structures reported here further demonstrate the utility of the isonipecotamide cation as a synthon for the generation of stable hydrogen-bonded structures. The presence of solvent water molecules in these structures is largely responsible for the non-occurrence of the common hydrogen-bonded amide–amide dimer, promoting instead various expanded cyclic hydrogen-bonding motifs.

Piperazine-1,4-diium bis(2,4,5-tricarboxybenzoate) dihydrate

In the title hydrated salt, C₄H₁₂N₂²⁺·2C₁₀H₅O₈⁻·2H₂O, the piperazinediium cation, lying about an inversion center, adopts a chair conformation. The benzene ring of the anion makes dihedral angles of 25.17 (8)° with the carboxyl­ate group and angles of 8.50 (7), 20.07 (7) and 80.86 (8)° with the three carb­oxy­lic acid groups. In the crystal, the cations, anions and water mol­ecules are connected by O—H⋯O and N—H⋯O hydrogen bonds into double layers parallel to (110).

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, C(6)H(13)N(2)O(8)(+)·C(8)H(4)O(6)(-), (I)], 4,5-dichlorophthalic acid [4-carbamoylpiperidinium 2-carboxy-4,5-dichlorobenzoate, C(6)H(13)N(2)O(8)(+)·C(8)H(3)Cl(2)O(4)(-), (II)] and 5-nitroisophthalic acid [4-carbamoylpiperidinium 3-carboxy-5-nitrobenzoate, C(6)H(13)N(2)O(8)(+)·C(8)H(4)O(6)(-), (III)], as well as the 2:1 compound with terephthalic acid [bis(4-carbamoylpiperidinium) benzene-1,2-dicarboxylate dihydrate, 2C(6)H(13)N(2)O(8)(+)·C(8)H(4)O(4)(2-)·2H(2)O, (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.

4-Carbamoylpiperidinium 2-carb-oxy-benzoate-benzene-1,2-dicarb-oxy-lic acid (1/1)

The asymmetric unit of the title salt adduct, C(6)H(13)N(2)O(+)·C(8)H(5)O(4) (-)·C(8)H(6)O(4), comprises one isonipecotamide cation, a hydrogen phthalate anion and a phthalic acid adduct mol-ecule. These form a two-dimensional hydrogen-bonded network through head-to-tail cation-anion-adduct mol-ecule inter-actions which include a cyclic heteromolecular amide-carboxyl-ate motif [graph set R(2) (2)(8)], conjoint cyclic R(2) (2)(6) and R(3) (3)(10) piperidinium N-H⋯O(carbox-yl) associations, as well as strong carboxyl O-H⋯O(carbox-yl) hydrogen bonds.

4-Carbamoylpiperidinium 5-nitro-salicylate

In the crystal structure of the title compound, C(6)H(13)N(2)O(+)·C(7)H(4)NO(5) (-), the isonipecotamide cations and the 5-nitro-salicylate anions form hydrogen-bonded chain substructures through head-to-tail piperidinium-carboxyl-ate N-H⋯O hydrogen bonds and through centrosymmetric cyclic head-to-head amide-amide hydrogen-bonding associations [graph set R(2) (2)(8)]. These chains are cross-linked by amide-carboxyl-ate N-H⋯O and piperidinium-nitro N-H⋯O associations, giving a sheet structure.

4-Carbamoylpiperidinium phenyl-acetate hemihydrate

The asymmetric unit of the title compound, C(6)H(13)N(2)O(+)·C(8)H(7)O(2) (-)·0.5H(2)O, comprises two isonipecotamide cations, two phenyl-acetate anions and a water mol-ecule of solvation. The hydrogen-bonding environments for both sets of ion pairs are essentially identical with the piperidinium and amide 'ends' of each cation involved in lateral heteromolecular hydrogen-bonded cyclic N-H⋯O associations [graph set R(2) (2)(11)] which incorporate a single carboxyl O-atom acceptor. These cyclic motifs enclose larger R(5) (5)(21) cyclic systems, forming sheet substructures which lie parallel to (101) and are linked across b by the single water mol-ecule via water O-H⋯O(c) (c = carboxylate) associations, giving a duplex-sheet structure.