N,N-Diformylmescaline: A novel analogue of mescaline detected in Queensland

N,N-Diformylmescaline, a novel analogue of mescaline, has recently been detected in Australia in two unrelated seizures. To confirm the identification, a three-step synthesis from 3,4,5-trimethoxyphenylacetic acid was devised. However, purification of the final product proved problematic with the compound prone to degradation in solution. Analysis of the compound by LC-MS indicated that the compound was unstable under acidic and basic conditions, breaking down to N-formylmescaline. Further degradation to mescaline was observed when the compound was dissolved in hydrochloric acid for an extended period of time suggesting that N,N-diformylmescaline may be a prodrug for mescaline. The GC-MS, NMR and FTIR data for the seized compound are presented along with details of the synthesis and studies of the compound's stability in solution.

Proton-transfer compounds featuring the unusual 4-arsonoanilinium cation from the reaction of (4-aminophenyl)arsonic acid with strong organic acids

The crystal structures of the 1:1 proton-transfer compounds of (4-aminophenyl)arsonic acid (p-arsanilic acid) with the strong organic acids, 2,4,6-trinitrophenol (picric acid), 3,5-dinitrosalicylic acid, (3-carboxy-4-hydroxy)benzenesulfonic acid (5-sulfosalicylic acid) and toluene-4-sulfonic acid have been determined at 200 K and their hydrogen–bonding patterns examined. The compounds are, respectively, anhydrous 4-arsonoanilinium 2,4,6-trinitrophenolate (1), the hydrate 4-arsonoanilinium 2-carboxy-4,6-dinitrophenolate monohydrate (2), the hydrate 4-arsonoanilinium (3-carboxy-4-hydroxy)benzenesulfonate monohydrate (3) and the partial solvate 4-arsonoanilinium toluene-4-sulfonate 0.8 hydrate (4). The asymmetric unit of 2, a phenolate, comprises two independent but conformationally similar cation-anion pairs and two water molecules of solvation, and in all compounds, extensive inter-species hydrogen–bonding interactions involving arsono O–H···O and anilinium N–H···O hydrogen–bonds generate three-dimensional supramolecular structures. In the cases of 1 and 2, the acceptors include phenolate and nitro O-atom acceptors, with 3 and 4, additionally, sulfonate O-atom acceptors, and with the hydrates 2–4, the water molecules of solvation. A feature of the hydrogen–bonding in 3 is the presence of primary chains extending along (010) through centrosymmetric cyclic R 2 2(8) motifs together with conjoined cyclic R 3 4(12) motifs, which include the water molecule of solvation. The primary hydrogen–bonding in the substructure of 4 involves homomolecular cation–cation arsono O–H···O interactions forming columns down the crystallographic four-fold axis of the unit cell.

Unusual 4-arsonoanilinium cationic species in the hydrochloride salt of (4-aminophenyl)arsonic acid and formed in the reaction of the acid with copper(II) sulfate, copper(II) chloride and cadmium chloride

Structures having the unusual protonated 4-arsonoanilinium species, namely in the hydrochloride salt, C₆H₉AsNO₃⁺·Cl^-, (I), and the complex salts formed from the reaction of (4-aminophenyl)arsonic acid (p-arsanilic acid) with copper(II) sulfate, i.e. hexaaquacopper(II) bis(4-arsonoanilinium) disulfate dihydrate, (C₆H₉AsNO₃)₂[Cu(H₂O)₆](SO₄)₂·2H₂O, (II), with copper(II) chloride, i.e. poly[bis(4-arsonoanilinium) [tetra-μ-chlorido-cuprate(II)]], {(C₆H₉AsNO₃)₂[CuCl₄]}_n, (III), and with cadmium chloride, i.e. poly[bis(4-arsonoanilinium) [tetra-μ-chlorido-cadmate(II)]], {(C₆H₉AsNO₃)₂[CdCl₄]}_n, (IV), have been determined. In (II), the two 4-arsonoanilinium cations are accompanied by [Cu(H₂O)₆]²⁺ cations with sulfate anions. In the isotypic complex salts (III) and (IV), they act as counter-cations to the {[CuCl₄]^2-}_n or {[CdCl₄]^2-}_n anionic polymer sheets, respectively. In (II), the [Cu(H₂O)₆]²⁺ ion sits on a crystallographic centre of symmetry and displays a slightly distorted octahedral coordination geometry. The asymmetric unit for (II) contains, in addition to half the [Cu(H₂O)₆]²⁺ ion, one 4-arsonoanilinium cation, a sulfate dianion and a solvent water molecule. Extensive O-H...O and N-H...O hydrogen bonds link all the species, giving an overall three-dimensional structure. In (III), four of the chloride ligands are related by inversion [Cu-Cl = 2.2826 (8) and 2.2990 (9) Å], with the other two sites of the tetragonally distorted octahedral CuCl₆ unit occupied by symmetry-generated Cl-atom donors [Cu-Cl = 2.9833 (9) Å], forming a two-dimensional coordination polymer network substructure lying parallel to (001). In the crystal, the polymer layers are linked across [001] by a number of bridging hydrogen bonds involving N-H...Cl interactions from head-to-head-linked As-O-H...O 4-arsonoanilinium cations. A three-dimensional network structure is formed. Cd^II compound (IV) is isotypic with Cu^II complex (III), but with the central CdCl₆ complex repeat unit having a more regular M-Cl bond-length range [2.5232 (12)-2.6931 (10) Å] compared to that in (III). This series of compounds represents the first reported crystal structures having the protonated 4-arsonoanilinium species.

Crystal structures and hydrogen bonding in the isotypic series of hydrated alkali metal (K, Rb and Cs) complexes with 4-amino-phenyl-arsonic acid

The structures of the alkali metal (K, Rb and Cs) complex salts with 4-amino-phenyl-arsonic acid (p-arsanilic acid) manifest an isotypic series with the general formula [M₂(C₆H₇AsNO₃)₂(H₂O)₃], with M = K {poly[di-μ₃-4-amino-phenyl-arsonato-tri-μ₂-aqua-dipotassium], [K₂(C₆H₇AsNO₃)₂(H₂O)₃], (I)}, Rb {poly[di-μ₃-4-amino-phenyl-arsonato-tri-μ₂-aqua-dirubidium], [Rb₂(C₆H₇AsNO₃)₂(H₂O)₃], (II)}, and Cs {poly[di-μ₃-4-amino-phenyl-arsonato-tri-μ₂-aqua-dirubidium], [Cs₂(C₆H₇AsNO₃)₂(H₂O)₃], (III)}, in which the repeating structural units lie across crystallographic mirror planes containing two independent and different metal cations and a bridging water mol-ecule, with the two hydrogen p-arsanilate ligands and the second water mol-ecule lying outside the mirror plane. The bonding about the two metal cations in all complexes is similar, one five-coordinate, the other progressing from five-coordinate in (I) to eight-coordinate in both (II) and (III), with overall M-O bond-length ranges of 2.694 (5)-3.009 (7) (K), 2.818 (4)-3.246 (4) (Rb) and 2.961 (9)-3.400 (10) Å (Cs). The additional three bonds in (II) and (III) are the result of inter-metal bridging through the water ligands. Two-dimensional coordination polymeric structures with the layers lying parallel to (100) are generated through a number of bridging bonds involving the water mol-ecules (including hydrogen-bonding inter-actions), as well as through the arsanilate O atoms. These layers are linked across [100] through amine N-H⋯O hydrogen bonds to arsonate and water O-atom acceptors, giving overall three-dimensional network structures.

The coordination complex structures and hydrogen bonding in the three-dimensional alkaline earth metal salts (Mg, Ca, Sr and Ba) of (4-aminophenyl)arsonic acid

(4-Aminophenyl)arsonic acid (p-arsanilic acid) is used as an antihelminth in veterinary applications and was earlier used in the monosodium salt dihydrate form as the antisyphilitic drug atoxyl. Examples of complexes with this acid are rare. The structures of the alkaline earth metal (Mg, Ca, Sr and Ba) complexes with (4-aminophenyl)arsonic acid (p-arsanilic acid) have been determined, viz. hexaaquamagnesium bis[hydrogen (4-aminophenyl)arsonate] tetrahydrate, [Mg(H₂O)₆](C₆H₇AsNO₃)·4H₂O, (I), catena-poly[[[diaquacalcium]-bis[μ₂-hydrogen (4-aminophenyl)arsonato-κ²O:O']-[diaquacalcium]-bis[μ₂-hydrogen (4-aminophenyl)arsonato-κ²O:O]] dihydrate], {[Ca(C₆H₇AsNO₃)₂(H₂O)₂]·2H₂O}_n, (II), catena-poly[[triaquastrontium]-bis[μ₂-hydrogen (4-aminophenyl)arsonato-κ²O:O']], [Sr(C₆H₇AsNO₃)₂(H₂O)₃]_n, (III), and catena-poly[[triaquabarium]-bis[μ₂-hydrogen (4-aminophenyl)arsonato-κ²O:O']], [Ba(C₆H₇AsNO₃)₂(H₂O)₃]_n, (IV). In the structure of magnesium salt (I), the centrosymmetric octahedral [Mg(H₂O)₆]²⁺ cation, the two hydrogen p-arsanilate anions and the four water molecules of solvation form a three-dimensional network structure through inter-species O-H and N-H hydrogen-bonding interactions with water and arsonate O-atom and amine N-atom acceptors. In one-dimensional coordination polymer (II), the distorted octahedral CaO₆ coordination polyhedron comprises two trans-related water molecules and four arsonate O-atom donors from bridging hydrogen arsanilate ligands. One bridging extension is four-membered via a single O atom and the other is eight-membered via O:O'-bridging, both across inversion centres, giving a chain coordination polymer extending along the [100] direction. Extensive hydrogen-bonding involving O-H...O, O-H...N and N-H...O interactions gives an overall three-dimensional structure. The structures of the polymeric Sr and Ba complexes (III) and (IV), respectively, are isotypic and are based on irregular MO₇ coordination polyhedra about the M²⁺ centres, which lie on twofold rotation axes along with one of the coordinated water molecules. The coordination centres are linked through inversion-related arsonate O:O'-bridges, giving eight-membered ring motifs and forming coordination polymeric chains extending along the [100] direction. Inter-chain N-H...O and O-H...O hydrogen-bonding interactions extend the structures into three dimensions and the crystal packing includes π-π ring interactions [minimum ring centroid separations = 3.4666 (17) Å for (III) and 3.4855 (8) Å for (IV)].

Hexaaquamanganese(II) bis[hydrogen (4-aminophenyl)arsonate] tetrahydrate

In the structure of the complex salt formed from the reaction of manganese(II) acetate with (4-aminophenyl)arsonic acid (p-arsanilic acid), [Mn(H2O)6](C6H7AsNO3)2·4H2O, the centrosymmetric Mn(H2O)6coordination polyhedron has slightly distorted octahedral stereochemistry, with the two hydrogen (4-aminophenyl)arsonate anions and the four water molecules of solvation related by inversion. Extensive O—H...O, O—H...N and N—H...O hydrogen bonds link all species, giving an overall three-dimensional supramolecular structure, which also has weak π–π ring interactions [minimum ring-centroid separation = 3.7304 (15) Å]. The structure is isotypic with that of the Mg salt.

Crystal structure and hydrogen bonding in the water-stabilized proton-transfer salt brucinium 4-aminophenylarsonate tetrahydrate

The tetra­hydrated brucinium salt of p-arsanilic acid forms a three-dimensional hydrogen-bonded network featuring the previously described undulating layered brucinium host substructure accommodating the anions and water guest mol­ecules and stabilized by cation–anion N—H⋯O and O—H⋯O hydrogen-bonding inter­actions.

In the structure of the brucinium salt of 4-amino­phenyl­arsonic acid (p-arsanilic acid), systematically 2,3-dimeth­oxy-10-oxostrychnidinium 4-amino­phenyl­ar­son­ate tetra­hydrate, (C₂₃H₂₇N₂O₄)[As(C₆H₇N)O₂(OH)]·4H₂O, the brucinium cations form the characteristic undulating and overlapping head-to-tail layered brucine substructures packed along [010]. The arsanilate anions and the water mol­ecules of solvation are accommodated between the layers and are linked to them through a primary cation N—H⋯O(anion) hydrogen bond, as well as through water O—H⋯O hydrogen bonds to brucinium and arsanilate ions as well as bridging water O-atom acceptors, giving an overall three-dimensional network structure.

Crystal structures and hydrogen bonding in the proton-transfer salts of nicotine with 3,5-di-nitro-salicylic acid and 5-sulfosalicylic acid

The crystal structures of the 1:1 salts of nicotine with 3,5-di­nitro­salicylic acid and with 5-sulfosalicylic acid both show polymeric hydrogen-bonded and π–π-bonded structures but these differ in that in the first example, cations and anions form separate cation chains or anion columns which are unassociated through formal hydrogen bonds while in the second, hydrogen-bonded cation–anion chains are found.

The structures of the 1:1 anhydrous salts of nicotine (NIC) with 3,5-di­nitro­salicylic acid (DNSA) and 5-sulfosalicylic acid (5-SSA), namely (1R,2S)-1-methyl-2-(pyridin-3-yl)-1H-pyrrolidin-1-ium 2-carb­oxy-4,6-di­nitro­phenolate, C₁₀H₁₅N₂⁺·C₇H₃N₂O₇⁻, (I), and (1R,2S)-1-methyl-2-(pyridin-3-yl)-1H-pyrrolidin-1-ium 3-carb­oxy-4-hy­droxy­benzene­sulfonate, C₁₀H₁₅N₂⁺·C₇H₅O₆S⁻, (II), are reported. The asymmetric units of both (I) and (II) comprise two independent nicotinium cations (C and D) and either two DNSA or two 5-SSA anions (A and B), respectively. One of the DNSA anions shows a 25% rotational disorder in the benzene ring system. In the crystal of (I), inter-unit pyrrolidinium N—H⋯N_pyridine hydrogen bonds generate zigzag NIC cation chains which extend along a, while the DNSA anions are not involved in any formal inter-species hydrogen bonding but instead form π–π-associated stacks which are parallel to the NIC cation chains along a [ring-centroid separation = 3.857 (2) Å]. Weak C—H⋯O inter­actions between chain substructures give an overall three-dimensional structure. In the crystal of (II), A and B anions form independent zigzag chains with C and D cations, respectively, through carb­oxy­lic acid O—H⋯N_pyridine hydrogen bonds. These chains, which extend along b, are pseudocentrosymmetrically related and give π–π inter­actions between the benzene rings of anions A and B and the pyridine rings of the NIC cations C and D, respectively [ring centroid separations = 3.6422 (19) and 3.7117 (19) Å]. Also present are weak C—H⋯O hydrogen-bonding inter­actions between the chains, giving an overall three-dimensional structure.

The three-dimensional hydrogen-bonded structures in the ammonium and sodium salt hydrates of 4-aminophenylarsonic acid

The structures of two hydrated salts of 4-aminophenylarsonic acid (p-arsanilic acid), namely ammonium 4-aminophenylarsonate monohydrate, NH4(+)·C6H7AsNO3(-)·H2O, (I), and the one-dimensional coordination polymer catena-poly[[(4-aminophenylarsonato-κO)diaquasodium]-μ-aqua], [Na(C6H7AsNO3)(H2O)3]n, (II), have been determined. In the structure of the ammonium salt, (I), the ammonium cations, arsonate anions and water molecules interact through inter-species N-H...O and arsonate and water O-H...O hydrogen bonds, giving the common two-dimensional layers lying parallel to (010). These layers are extended into three dimensions through bridging hydrogen-bonding interactions involving the para-amine group acting both as a donor and an acceptor. In the structure of the sodium salt, (II), the Na(+) cation is coordinated by five O-atom donors, one from a single monodentate arsonate ligand, two from monodentate water molecules and two from bridging water molecules, giving a very distorted square-pyramidal coordination environment. The water bridges generate one-dimensional chains extending along c and extensive interchain O-H...O and N-H...O hydrogen-bonding interactions link these chains, giving an overall three-dimensional structure. The two structures reported here are the first reported examples of salts of p-arsanilic acid.

4-(4-Amino-phenyl-sulfon-yl)anilinium toluene-4-sulfonate

In the title p-toluene-sulfonate salt of the drug dapsone, C12H13N2O2S(+)·C7H7O3S(-), the dihedral angle between the two aromatic rings of the dapsone monocation is 70.19 (17)° and those between these rings and that of the p-toluene-sulfonate anion are 72.34 (17) and 46.43 (17)°. All amine and aminium H atoms are involved in inter-molecular N-H⋯O hydrogen-bonding associations with sulfonyl O-atom acceptors as well as one of the sulfone O atoms, giving a three-dimensional structure.

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.

4-Meth-oxy-anilinium 2-carb-oxy-4,5-di-chloro-benzoate

In the title salt C7H10NO(+)·C8H3Cl2O4 (-) the benzene rings of the cation and anion are essentially parallel [inter-ring dihedral angle 4.8 (2)°]. In the anion the carb-oxy-lic acid and carboxyl-ate groups make dihedral angles of 19.0 (2) and 79.5 (2)°, respectively, with the benzene ring. Aminium N-H⋯O, carb-oxy-lic acid O-H⋯O and weak aromatic C-H⋯O hydrogen-bonding associations with carboxyl O-atom acceptors together with cation-anion π-π ring inter-actions [minimum ring centroid separation = 3.734 (3) Å] give rise to a sheet structure lying parallel to (001).

Hydrogen bonding in two ammonium salts of 5-sulfosalicylic acid: ammonium 3-carboxy-4-hydroxybenzenesulfonate monohydrate and triammonium 3-carboxy-4-hydroxybenzenesulfonate 3-carboxylato-4-hydroxybenzenesulfonate

The structures of two ammonium salts of 3-carboxy-4-hydroxybenzenesulfonic acid (5-sulfosalicylic acid, 5-SSA) have been determined at 200 K. In the 1:1 hydrated salt, ammonium 3-carboxy-4-hydroxybenzenesulfonate monohydrate, NH4(+)·C7H5O6S(-)·H2O, (I), the 5-SSA(-) monoanions give two types of head-to-tail laterally linked cyclic hydrogen-bonding associations, both with graph-set R4(4)(20). The first involves both carboxylic acid O-H···O(water) and water O-H···O(sulfonate) hydrogen bonds at one end, and ammonium N-H···O(sulfonate) and N-H···O(carboxy) hydrogen bonds at the other. The second association is centrosymmetric, with end linkages through water O-H···O(sulfonate) hydrogen bonds. These conjoined units form stacks down c and are extended into a three-dimensional framework structure through N-H···O and water O-H···O hydrogen bonds to sulfonate O-atom acceptors. Anhydrous triammonium 3-carboxy-4-hydroxybenzenesulfonate 3-carboxylato-4-hydroxybenzenesulfonate, 3NH4(+)·C7H4O6S(2-)·C7H5O6S(-), (II), is unusual, having both dianionic 5-SSA(2-) and monoanionic 5-SSA(-) species. These are linked by a carboxylic acid O-H···O hydrogen bond and, together with the three ammonium cations (two on general sites and the third comprising two independent half-cations lying on crystallographic twofold rotation axes), give a pseudo-centrosymmetric asymmetric unit. Cation-anion hydrogen bonding within this layered unit involves a cyclic R3(3)(8) association which, together with extensive peripheral N-H···O hydrogen bonding involving both sulfonate and carboxy/carboxylate acceptors, gives a three-dimensional framework structure. This work further demonstrates the utility of the 5-SSA(-) monoanion for the generation of stable hydrogen-bonded crystalline materials, and provides the structure of a dianionic 5-SSA(2-) species of which there are only a few examples in the crystallographic literature.

Proton-transfer compounds with 4-amino-N-(4,6-dimethylpyrimidin-2-yl)benzenesulfonamide (sulfamethazine): the structures and hydrogen bonding in the salts with 5-nitrosalicylic acid and picric acid

The structures of the anhydrous proton-transfer compounds of the sulfa drug sulfamethazine with 5-nitrosalicylic acid and picric acid, namely 2-(4-aminobenzenesulfonamido)-4,6-dimethylpyrimidinium 2-hydroxy-5-nitrobenzoate, C12H15N4O2S(+)·C7H4NO4(-), (I), and 2-(4-aminobenzenesulfonamido)-4,6-dimethylpyrimidinium 2,4,6-trinitrophenolate, C12H15N4O2S(+)·C6H2N3O7(-), (II), respectively, have been determined. In the asymmetric unit of (I), there are two independent but conformationally similar cation-anion heterodimer pairs which are formed through duplex intermolecular N(+)-H···O(carboxylate) and N-H···O(carboxylate) hydrogen-bond pairs, giving a cyclic motif [graph set R2(2)(8)]. These heterodimers form separate and different non-associated substructures through aniline N-H···O hydrogen bonds, one one-dimensional, involving carboxylate O-atom acceptors, the other two-dimensional, involving both carboxylate and hydroxy O-atom acceptors. The overall two-dimensional structure is stabilized by π-π interactions between the pyrimidinium ring and the 5-nitrosalicylate ring in both heterodimers [minimum ring-centroid separation = 3.4580 (8) Å]. For picrate (II), the cation-anion interaction involves a slightly asymmetric chelating N-H···O R2(1)(6) hydrogen-bonding association with the phenolate O atom, together with peripheral conjoint R1(2)(6) interactions between the same N-H groups and O atoms of the ortho-related nitro groups. An inter-unit amine N-H···O(sulfone) hydrogen bond gives one-dimensional chains which extend along a and inter-associate through π-π interactions between the pyrimidinium rings [centroid-centroid separation = 3.4752 (9) Å]. The two structures reported here now bring to a total of four the crystallographically characterized examples of proton-transfer salts of sulfamethazine with strong organic acids.

2-(4-Amino-benzene-sulfonamido)-4,6-dimethyl-pyrimidin-1-ium 2-carb-oxy-4,6-dinitro-phenolate

In the structure of the phenolate salt of the sulfa drug sulfamethazine with 3,5-dinitro-salicylic acid, C12H15N4O2S(+)·C7H3N2O7 (-), the dihedral angle between the pyrimidine and benzene rings of the cation is 59.70 (17)°. In the crystal, cation-anion hydrogen-bonding inter-actions involving pyrim-idine-carb-oxy N(+)-H⋯O and amine-carb-oxy N-H⋯O pairs give a cyclic R 2 (2)(8) motif while secondary N-H⋯O hydrogen bonds between the aniline group and both sulfone and nitro O-atom acceptors give a two-dimensional structure extending in (001).

4-Amino-N-(4,6-dimethyl-pyrimidin-2-yl)benzene-sulfonamide-2-nitro-benzoic acid (1/1)

In the asymmetric unit of the title co-crystal, C(12)H(14)N(4)O(2)S·C(7)H(5)NO(4), the sulfamethazine and 2-nitro-benzoic acid mol-ecules form a heterodimer through inter-molecular amide-carb-oxy-lic acid N-H⋯O and carb-oxy-lic acid-pyrimidine O-H⋯N hydrogen-bond pairs, giving a cyclic motif [graph set R(2) (2)(8)]. The dihedral angle between the two aromatic ring systems in the sulfamethazine mol-ecule is 88.96 (18)° and the nitro group of the acid is 50% rotationally disordered. Secondary aniline N-H⋯O(sulfone) hydrogen-bonding associations give a two-dimensional structure lying parallel to the ab plane.

4-(4-Nitro-benz-yl)pyridinium 3-carb-oxy-4-hy-droxy-benzene-sulfonate

In the title salt, C(12)H(11)N(2)O(2) (+)·C(7)H(5)O(6)S(-), the dihedral angle between the benzene and pyridine rings in the 4-(4-nitro-benz-yl)pyridinium cation is 82.7 (2)°. Within the anion there is an intramolecular hydroxy-O-H⋯O(carboxylic acid) bond. In the crystal, the cation forms a single N(+)-H⋯O(sulfonate) hydrogen bond with the anion. These cation-anion pairs inter-act through duplex anion carb-oxy-lic acid O-H⋯O(sulfonate) hydrogen bonds, giving a centrosymmetric cyclic association [graph set R(2) (2)(16)]. The crystals studied were non-merohedrally twinned.

Hydrogen bonding in cyclic imides and amide carboxylic acid derivatives from the facile reaction ofcis-cyclohexane-1,2-carboxylic anhydride witho- andp-anisidine andm- andp-aminobenzoic acids

The structures of the open-chain amide carboxylic acidrac-cis-2-[(2-methoxyphenyl)carbamoyl]cyclohexane-1-carboxylic acid, C15H19NO4, (I), and the cyclic imidesrac-cis-2-(4-methoxyphenyl)-3a,4,5,6,7,7a-hexahydroisoindole-1,3-dione, C15H17NO3, (II), chiralcis-3-(1,3-dioxo-3a,4,5,6,7,7a-hexahydroisoindol-2-yl)benzoic acid, C15H15NO4, (III), andrac-cis-4-(1,3-dioxo-3a,4,5,6,7,7a-hexahydroisoindol-2-yl)benzoic acid monohydrate, C15H15NO4·H2O, (IV), are reported. In the amide acid (I), the phenylcarbamoyl group is essentially planar [maximum deviation from the least-squares plane = 0.060 (1) Å for the amide O atom] and the molecules form discrete centrosymmetric dimers through intermolecular cyclic carboxy–carboxy O—H...O hydrogen-bonding interactions [graph-set notationR22(8)]. The cyclic imides (II)–(IV) are conformationally similar, with comparable benzene ring rotations about the imide N—Carbond [dihedral angles between the benzene and isoindole rings = 51.55 (7)° in (II), 59.22 (12)° in (III) and 51.99 (14)° in (IV)]. Unlike (II), in which only weak intermolecular C—H...Oimidehydrogen bonding is present, the crystal packing of imides (III) and (IV) shows strong intermolecular carboxylic acid O—H...O hydrogen-bonding associations. With (III), these involve imide O-atom acceptors, giving one-dimensional zigzag chains [graph-setC(9)], while with the monohydrate (IV), the hydrogen bond involves the partially disordered water molecule which also bridges molecules through both imide and carboxy O-atom acceptors in a cyclicR44(12) association, giving a two-dimensional sheet structure. The structures reported here expand the structural database for compounds of this series formed from the facile reaction ofcis-cyclohexane-1,2-dicarboxylic anhydride with substituted anilines, in which there is a much larger incidence of cyclic imides compared to amide carboxylic acids.

Cyclic imides and an open-chain amide carboxylic acid from the facile reaction ofcis-cyclohexane-1,2-carboxylic anhydride with the isomeric monofluoroanilines

The structures of the cyclic imidescis-2-(2-fluorophenyl)-3a,4,5,6,7,7a-hexahydroisoindole-1,3-dione, C14H14FNO2, (I), andcis-2-(4-fluorophenyl)-3a,4,5,6,7,7a-hexahydroisoindoline-1,3-dione, C14H14FNO2, (III), and the open-chain amide acidrac-cis-2-[(3-fluorophenyl)carbamoyl]cyclohexane-1-carboxylic acid, C14H16FNO3, (II), are reported. Cyclic imides (I) and (III) are conformationally similar, with comparable ring rotations about the imide N—Carbond [the dihedral angles between the benzene ring and the five-membered isoindole ring are 55.40 (8)° for (I) and 51.83 (7)° for (III)]. There are no formal intermolecular hydrogen bonds involved in the crystal packing of either (I) or (III). With the acid (II), in which themeta-related F-atom substituent is rotationally disordered (0.784:0.216), the amide group lies slightly out of the benzene plane [the interplanar dihedral angle is 39.7 (1)°]. Intermolecular amide–carboxyl N—H...O hydrogen-bonding interactions between centrosymmetrically related molecules form stacks extending downb, and these are linked acrosscby carboxyl–amide O—H...O hydrogen bonds, giving two-dimensional layered structures which lie in the (011) plane. The structures reported here represent examples of compounds analogous to the phthalimides or phthalanilic acids and have little precedence in the crystallographic literature.

4-Amino-N-(4,6-dimethyl-pyrimidin-2-yl)-benzene-sulfonamide-4-nitro-benzoic acid (1/1)

In the asymmetric unit of the title co-crystal, C(7)H(5)NO(4)·C(12)H(14)N(4)O(2)S, there are two independent but conformationally similar heterodimers, which are formed through inter-molecular N-H⋯O(carb-oxy) and carbox-yl-pyrimidine O-H⋯N hydrogen-bond pairs, giving a cyclic motif [graph set R(2) (2)(8)]. The dihedral angles between the rings in the sulfonamide molecules are 78.77 (8) and 82.33 (9)° while the dihedral angles between the ring and the CO(2)H group in the acids are 2.19 (9) and 7.02 (10)°. A two-dimensional structure parallel to the ab plane is generated from the heterodimer units through hydrogen-bonding associations between NH(2) and sulfone groups. Between neighbouring two-dimensional arrays there are two types of aromatic π-π stacking inter-actions involving either one of the pyrimidine rings and a 4-nitro-benzoic acid mol-ecule [minimum ring centroid separation = 3.5886 (9) Å] or two acid mol-ecules [minimum ring centroid separation = 3.7236 (10) Å].

Bis(benzyl-aminium) 4,5-dichloro-benzene-1,2-dicarboxyl-ate monohydrate

In the structure of the title salt, 2C(7)H(10)N(+)·C(8)H(2)Cl(2)O(4) (2-)·H(2)O, the two benzyl-aminium anions have different conformations, one being essentially planar and the other having the side chain rotated out of the benzene plane [minimum ring to side-chain C-C-C-N torsion angles = -3.6 (6) and 50.1 (5)°, respectively]. In the 4,5-dichloro-phthalate dianion, the carboxyl-ate groups make dihedral angles of 23.0 (2) and 76.5 (2)° with the benzene ring. In the crystal, aminium N-H⋯O and water O-H⋯O hydrogen-bonding associations with carboxyl-ate O-atom acceptors give a two-dimensional duplex sheet structure which extends along the (011) plane. Weak π-π inter-actions are also present between the benzene ring of the dianion and one of the cation rings [minimum ring centroid separation = 2.749 (3) Å].

rac-3-exo-Ammonio-7-anti-carboxytricyclo[2.2.1.0.2,6]heptane-3-endo-carboxylate monohydrate

The racemic title compound, C₉H₁₁NO₄·H₂O, a tricyclic rearranged amino­norbornane dicarb­oxy­lic acid, is a conformationally rigid analogue of glutamic acid and exists as an ammonium-carboxyl­ate zwitterion, with the bridghead carb­oxy­lic acid group anti-related. In the crystal, N—H⋯O and O—H⋯O hydrogen bonds involving the ammonium, carb­oxy­lic acid and water donor groups with both water and carboxyl O-atom acceptors give a three-dimensional framework structure.

1,1,3,3-Tetraethylisoindolin-2-ium chloride

In the title compound, C₁₆H₂₆N⁺·Cl⁻, the cations and anions form discrete centrosymetric cyclic dimers through N—H⋯Cl hydrogen-bonding associations with graph-set R₄²(8).

rac-4-Carbamoylpiperidiniumcis-2-carboxycyclohexane-1-carboxylate

In the title racemic salt, C₆H₁₃N₂O⁺·C₈H₁₁O₄⁻, formed from the reaction of cis-cyclo­hexane-1,2-dicarb­oxy­lic anhydride with isonipecotamide, the cations are linked into duplex chain substructures through both centrosymmetric cyclic head-to-head ‘amide motif’ hydrogen-bonding associations [graph set R₂²(8)] and ‘side-by-side’ R₂²(14) associations. The anions are incorporated into the chains through cyclic R₄³(10) inter­actions involving amide and piperidinium N—H⋯O_carbox­yl hydrogen bonds which, together with inter-anion carb­oxy­lic acid O—H⋯O_carbox­yl hydrogen bonds, give a two-dimensional layered structure extending along (011).

4-[(4-Amino-phen-yl)sulfon-yl]aniline-3,5-dinitro-benzoic acid (1/1)

The title compound, C₇H₄N₂O₆·C₁₂H₁₂N₂O₂S, is a 1:1 cocrystal of the drug dapsone with 3,5-dinitro­benzoic acid. The dihedral angle between the two aromatic rings of the dapsone mol­ecule is 75.4 (2)°, and the dihedral angles between these rings and that of the 3,5-dinitro­benzoic acid are 64.5 (2) and 68.4 (2)°. A strong inter­molecular carb­oxy­lic acid O—H⋯N_amine hydrogen bond is found, together with inter­molecular amine N—H⋯O hydrogen-bonding associations with carboxyl, nitro and sulfone O-atom acceptors. In addition, weak π–π inter­actions between one of the dapsone benzene rings and the 3,5-dinitro­benzoic acid ring [ring centroid separation = 3.774 (2) Å] results in a two-dimensional network structure.

4-(4-Amino-phenyl-sulfon-yl)aniline-1,3,5-trinitro-benzene (1/2)

The asymmetric unit of the title co-crystalline 1:2 adduct, C₁₂H₁₂N₂O₂·2C₆H₃N₃O₆, contains two independent mol­ecules of bis­(4-amino­phen­yl) sulfone (the drug Dapsone) and four mol­ecules of 1,3,5-trinitro­benzene and is extended into a two-dimensional hydrogen-bonded network structure through amino N—H⋯O hydrogen-bonding associations with nitro O-atom acceptors. In the two independent Dapsone mol­ecules, the inter-ring dihedral anges are 69.6 (3) and 63.63 (9)°. Aromatic π–π inter­actions are also found between one of the Dapsone aromatic rings and a trinitro­benzene ring [minimum ring centroid separation = 3.596 (3) Å]. A 4-amino­phenyl ring moiety of one of the Dapsone mol­ecules and two nitro groups of a trinitro­benzene are disordered in a 50:50 ratio.

Poly[tetra-μ-aqua-diaqua-tetra-kis-[μ-(E)-2-nitro-cinnamato]tetra-rubidium]

In the structure of the title compound, [Rb₄(C₉H₆NO₄)₄(H₂O)₆]_n, the asymmetric unit comprises four rubidium cations, two of which have an RbO₇ coordination polyhedron with a monocapped distorted octa­hedral stereochemistry and two of which have a distorted RbO₆ octa­hedral coordination. The bonding about both the seven-coordinate cations is similar, comprising one monodentate water mol­ecule together with three bridging water mol­ecules and three carboxyl­ate O-atom donors, two of which are bridging. The environments around the six-coordinate cations are also similar, comprising a monodentate nitro O-atom donor, a bridging water mol­ecule and four bridging carboxyl­ate O-atom donors [overall Rb—O range = 2.849 (2)–3.190 (2) Å]. The coordination leads to a two-dimensional polymeric structure extending parallel to (001), which is stabilized by inter­layer water O—H⋯O hydrogen-bonding associations to water, carboxyl and nitro O-atom acceptors, together with weak inter-ring π–π inter­actions [minimum ring centroid–centroid separation = 3.5319 (19) Å].

Ethane-1,2-diaminium 4,4'-sulfonyl-dibenzoate

In the title salt, C(2)H(10)N(2) (2+)·C(14)H(8)O(6)S(2-), both the ethyl-ene-diaminium cations and the 4,4'-sulfonyl-dibenzoate dianions have crystallographic twofold rotational symmetry. They are inter-linked by aminium N-H⋯O(carboxyl-ate) hydrogen-bonding associations, giving sheets parallel to (101) and are further linked along [010], forming a three-dimensional structure.

catena-Poly[[diaqualithium]-μ-[rac-cis-(2-carboxycyclohexane-1-carboxylato-κ2O1:O2]]

In the structure of the title compound, [Li(C₈H₁₁O₄)(H₂O)₂]_n, the distorted tetra­hadral LiO₄ coordination sphere comprises two water mol­ecules and two carboxyl O-atom donors from separate bridging cis-2-carb­oxy­cyclo­hexane-1-carboxyl­ate monoanions [Li—O = 1.887 (4)–1.946 (3) Å], giving chain substructures which extend along [010]. Water–water and water–carboxyl O—H⋯O hydrogen bonds stabilize these chain structures and provide inter­chain links, resulting in a two-dimensional layered structure extending parallel to (100).

Poly[aqua(μ3-2-hydroxy-5-nitrobenzoato-κ3O1:O1′:O2)rubidium]

In the structure of title compound, [Rb(C₇H₄NO₅)(H₂O)]_n, the centrosymmetric cyclic dimeric repeating unit comprises two irregular RbO₄ complex centres bridged by the carboxyl­ate groups of the 5-nitro­salicylate ligands. The coordination about each Rb atom is completed by a monodentate water mol­ecule and a phenolic O-atom donor which gives a bridging extension [Rb—O range = 3.116 (7)–3.135 (5) Å]. The polymeric structure is stabilized by inter­molecular water O—H⋯O_{carboxyl­ate} hydrogen bonds and weak inter-ring π–π inter­actions [minimum ring centroid separation = 3.620 (4) Å]. An intramolecular O—H⋯O hydrogen bond between phenol and carboxylate groups is also present.

4-Amino-pyridinium cis-2-carb-oxy-cyclo-hexane-1-carboxyl-ate

In the structure of the title molecular salt, C₅H₇N₂⁺·C₈H₁₁O₄⁻, the cis monoanions associate through short O—H⋯O hydrogen bonds in the carb­oxy­lic acid groups [graph set C(7)], forming zigzag chains which extend along the c axis. These are inter­linked through pyridinium and amine N—H⋯O hydrogen bonds, giving a three-dimensional network structure.

rac-cis-Cyclohexane-1,2-dicarboxylic acid–isoquinoline (1/1)

In the crystal structure of the title mol­ecular adduct, C₉H₇N·C₈H₁₂O₄, the two species are ­linked through a carb­oxy­lic acid–isoquinoline O—H⋯N hydrogen bond. These mol­ecular pairs then inter-associate through the second acid group of the cis-cyclo­hexane-1,2-dicarb­oxy­lic acid molecules, forming a classic centrosymmetric cyclic head-to-head carb­oxy­lic acid–carboxyl O—H⋯O hydrogen-bonding association [graph-set R₂²(8)], giving a zero-dimensional (cluster) structure, consisting of two of each species.

tert-Butylaminium 2-carboxy-4,5-dichlorobenzoate

In the structure of the title anhydrous salt, C₄H₁₂N⁺·C₈H₃Cl₂O₄⁻, the 4,5-dichloro­phthalate monoanions have the common ‘planar’ conformation with the carboxyl groups close to coplanar with the benzene ring and with a short intra­molecular carb­oxy­lic acid O—H⋯O hydrogen bond. In the crystal, a two-dimensional sheet structure is formed through aminium N—H⋯O_carbox­yl hydrogen-bonding associations.

Hexaaqua-magnesium bis-(3-carb-oxy-4-hy-droxy-benzene-sulfonate) dihydrate

In the crystal structure of the title compound, [Mg(H(2)O)(6)](C(7)H(5)O(6)S)(2)·2H(2)O, the octa-hedral complex cation lies on an inversion centre and is hydrogen bonded through the coordinated water molecules to the substituted benzene-sulfonate monoanions and the water mol-ecules of solvation. These inter-actions together with a carb-oxy-lic acid O-H⋯O(sulfonate) association give a three-dimensional structure.

rac-2-Aminopyridiniumcis-2-carboxycyclohexane-1-carboxylate

In the structure of the title compound, C₅H₇N₂⁺·C₈H₁₁O₄⁻, the cis anions associate through head-to-tail carb­oxy­lic acid–carboxyl O—H⋯O hydrogen bonds [graph set C(7)], forming chains which extend along c and are inter­linked through the carboxyl groups, forming cyclic R₂²(8) associations with the pyridinium and an amine H-atom donor of the cation. Further amine–carboxyl N—H⋯O inter­actions form enlarged centrosymmetric rings [graph set R₄⁴(18)] and extensions down b, giving a three-dimensional structure.

Poly[di-μ-aqua-bis-(μ-2-amino-4-nitro-benzoato)dicaesium]

In the structure of title compound, [Cs(2)(C(7)H(5)N(2)O(4))(2)(H(2)O)(2)](n), the asymmetric unit contains two independent Cs atoms comprising different coordination polyhedra. One is nine-coordinate, the other seven-coordinate, both having irregular configurations. The CsO(9) coordination polyhedron comprises O-atom donors from three bridging water mol-ecules, one of which is doubly bridging, three from carboxyl-ate groups, and three from nitro groups, of which two are bidentate chelate bridging. The CsO(6)N coordination polyhedron comprises the two bridging water mol-ecules, one amine N-atom donor, one carboxyl-ate O-atom donor and four O-atom donors from nitro groups (two from the chelate bridges). The extension of the dimeric unit gives a three-dimensional polymeric structure, which is stabilized by both intra- and inter-molecular amine N-H⋯O and water O-H⋯O hydrogen bonds to carboxyl-ate O-atom acceptors, as well as inter-ring π-π inter-actions [minimum ring centroid-centroid separation = 3.4172 (15) Å].

Bis(guanidinium) 4,5-dichloro-phthalate monohydrate

In the structure of the title hydrated salt, 2CH(6)N(3) (+)·C(8)H(2)Cl(2)O(4) (2-)·H(2)O, the planes of the carboxyl-ate groups of the dianion are rotated out of the plane of the benzene ring [dihedral angles = 48.42 (10) and 55.64 (9)°]. A duplex-sheet structure is formed through guanidinium-carboxyl-ate N-H⋯O, guanidinium-water N-H⋯O and water-carboxyl-ate O-H⋯O hydrogen-bonding associations.

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.

2-(4-Amino-phen-yl)-1-phenyl-diazenium 2,4,6-trinitro-phenolate

In the title salt, C₁₂H₁₂N₃⁺·C₆H₂N₃O₇⁻, the diazenyl group of the 4-(phenyl­diazen­yl)aniline mol­ecule is protonated and forms a hydrogen bond with the phenolate O-atom acceptor of the picrate anion. Structure extension occurs through two symmetrical inter-ion three-centre amine N—H⋯O,O′_nitro hydrogen-bonding associations [graph set R₁²(4)], giving a convoluted two-dimensional network structure.

2,4,6-Trinitro-N-[4-(phenyl-diazen-yl)phen-yl]aniline

The title compound, C(18)H(12)N(6)O(6), was prepared from the reaction of 4-(phenyl-diazen-yl)aniline (aniline yellow) with picryl-sulfonic acid. The dihedral angle formed by the two benzene rings of the diphenyl-diazenyl ring system is 6.55 (13)° and that formed by the rings of the picrate-aniline ring system is 48.76 (12)°. The mol-ecule contains an intra-molecular aniline-nitro N-H⋯O hydrogen bond.

Diiodidobis[4-(4-nitro-benz-yl)pyridine-κN]zinc

The asymmetric unit of the title compound, [ZnI(2)(C(12)H(10)N(2)O(2))(2)], obtained from the reaction of 4-(4-nitro-benz-yl)pyridine with zinc(II) iodide, contains two independent discrete distorted tetra-hedral complex units [Zn-I = 2.5472 (8)-2.5666 (7) Å and Zn-N = 2.044 (4)-2.052 (4) Å], which are essentially identical conformationally. The crystal used for measurement was a racemic twin.

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.

catena-Poly[[[diaqua-cobalt(II)]-μ-(3,5-dinitro-2-oxidobenzoato)-κO,O:O-[tetra-aqua-cobalt(II)]-μ-(3,5-dinitro-2-oxidobenzoato)-κO:O,O] dihydrate]

In polymeric title compound, {[Co(2)(C(7)H(2)N(2)O(7))(2)(H(2)O)(6)]·2H(2)O}(n), obtained from the reaction of 3,5-dinitro-salicylic acid with cobalt(II) acetate, both Co(II) atoms are located on inversion centres and exhibit a distorted octahedral coordination geometry. The coordin-ation sphere about one Co(II) atom comprises four O-atom donors from two bidentate chelate (O(phenolate) and O(carbox-yl)) and bridging dianionic ligands and two water mol-ecules [Co-O range = 2.0249 (11)-2.1386 (14) Å], while that about the second Co(II) atom has four water mol-ecules and two bridging carboxyl-ate O-donor atoms [Co-O range = 2.0690 (14)-2.1364 (11) Å]. The coordinated water mol-ecules as well as the water mol-ecules of solvation give O-H⋯O water-water and water-carboxyl hydrogen-bonding inter-actions in the three-dimensional framework structure.

rac-Ammonium cis-2-carb-oxy-cyclo-hexane-1-carboxyl-ate

In the structure of the title compound, NH₄⁺·C₈H₁₁O₄⁻, the carboxyl and carboxyl­ate groups of the cation adopt C—C—C—O torsion angles of 174.9 (2) and −145.4 (2)°, respectively, with the alicyclic ring. The ammonium H atoms of the cations give a total of five hydrogen-bonding associations with carboxyl­ate O-atom acceptors of the anion which, together with a carboxyl O—H⋯O_{carboxyl­ate} inter­action give sheet structures which lie in the (101) planes.

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.

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

The structures of the anhydrous 1:1 proton-transfer compounds of isonipecotamide (piperidine-4-carboxamide) with picric acid and 3,5-dinitrosalicylic acid, namely 4-carbamoylpiperidinium 2,4,6-trinitrophenolate, C(6)H(13)N(2)O(+)·C(6)H(2)N(3)O(7)(-), (I), and 4-carbamoylpiperidinium 2-carboxy-4,6-dinitrophenolate [two forms of which were found, the monoclinic α-polymorph, (II), and the triclinic β-polymorph, (III)], C(6)H(13)N(2)O(+)·C(7)H(3)N(2)O(7)(-), have been determined at 200 K. All three compounds form hydrogen-bonded structures, viz. one-dimensional in (II), two-dimensional in (I) and three-dimensional in (III). In (I), the cations form centrosymmetric cyclic head-to-tail hydrogen-bonded homodimers [graph set R(2)(2)(14)] through lateral duplex piperidinium-amide N-H...O interactions. These dimers are extended into a two-dimensional network structure through further interactions with phenolate and nitro O-atom acceptors, including a direct symmetric piperidinium-phenol/nitro N-H...O,O cation-anion association [graph set R(1)(2)(6)]. The monoclinic polymorph, (II), has a similar R(1)(2)(6) cation-anion hydrogen-bonding interaction to (I) but with an additional conjoint symmetrical R(1)(2)(4) interaction as well as head-to-tail piperidinium-amide N-H...O,O hydrogen bonds and amide-carboxyl N-H...O hydrogen bonds, giving a network structure which includes large R(4)(3)(20) rings. The hydrogen bonding in the triclinic polymorph, (III), is markedly different from that of monoclinic (II). The asymmetric unit contains two independent cation-anion pairs which associate through cyclic piperidinium-carboxyl N-H...O,O' interactions [graph set R(1)(2)(4)]. The cations also show the zigzag head-to-tail piperidinium-amide N-H...O hydrogen-bonded chain substructures found in (II), but in addition feature amide-nitro and amide-phenolate N-H...O associations. As well, there is a centrosymmetric double-amide N-H...O(carboxyl) bridged bis(cation-anion) ring system [graph set R(4)(2)(8)] in the three-dimensional framework. The structures reported here demonstrate the utility of the isonipecotamide cation as a synthon with previously unrecognized potential for structure assembly applications. Furthermore, the structures of the two polymorphic 3,5-dinitrosalicylic acid salts show an unusual dissimilarity in hydrogen-bonding characteristics, considering that both were obtained from identical solvent systems.

Hydrogen bonding in the anhydrous 1:1 proton-transfer compounds of isonipecotamide with nitro-substituted benzoic acids: the salts of the three isomeric mononitrobenzoic acids and of 3,5-dinitrobenzoic acid

The structures of the anhydrous 1:1 proton-transfer compounds of isonipecotamide (piperidine-4-carboxamide) with the three isomeric mononitro-substituted benzoic acids and with 3,5-dinitrobenzoic acid, namely 4-carbamoylpiperidinium 2-nitrobenzoate, (I), 4-carbamoylpiperidinium 3-nitrobenzoate, (II), and 4-carbamoylpiperidinium 4-nitrobenzoate, (III), all C(6)H(13)N(2)O(+)·C(7)H(4)NO(4)(-), and 4-carbamoylpiperidinium 3,5-dinitrobenzoate, C(6)H(13)N(2)O(8)(+)·C(7)H(3)N(2)O(6)(-), (IV), respectively, have been determined at 200 K. All the salts form hydrogen-bonded structures, viz. three-dimensional in (I), two-dimensional in (II) and (III), and one-dimensional in (IV). Featured in the hydrogen bonding of three of these [(I), (II) and (IV)] is the cyclic head-to-head amide-amide homodimer motif [graph set R(2)(2)(8)] through a duplex N-H...O association, the dimer then giving structure extension via either piperidinium or amide H-atom donors and carboxylate O-atom and, in some examples [(II) and (IV)], nitro O-atom acceptors. In (I), the centrosymmetric amide-amide homodimers are expanded laterally through N-H...O hydrogen bonds via cyclic R(4)(2)(8) interactions, forming ribbons which extend along the c cell direction. These ribbons incorporate the 2-nitrobenzoate cations through centrosymmetric cyclic piperidine-carboxylate N-H...O associations [graph set R(4)(4)(12)], giving interconnected sheets in the three-dimensional structure. In (II), in which no amide-amide homodimer is present, duplex piperidinium-amide N-H...O homomolecular hydrogen-bonding associations [graph set R(2)(2)(14)] give centrosymmetric head-to-tail dimers. Structure extension occurs through hydrogen-bonding associations between both the amide H-atom donors and carboxylate and nitro O-atom acceptors, as well as a three-centre piperidinium-carboxylate N-H...O,O' cyclic R(1)(2)(4) association, giving the two-dimensional network structure. In (III), the centrosymmetric amide-amide dimers are linked through the two carboxylate O-atom acceptors of the anions via bridging piperidinium N-H...O,O'...H-N(amide) hydrogen bonds, giving the two-dimensional sheet structure which features centrosymmetric cyclic R(4)(4)(12) associations. In (IV), the amide-amide dimer is also centrosymmetric, with the dimers linked to the anions through amide-nitro N-H...O interactions. The piperidinium groups extend the structure into one-dimensional ribbons via N-H...O(carboxylate) hydrogen bonds. The structures reported here further demonstrate the utility of the isonipecotamide cation in molecular assembly. They also highlight the efficacy of the cyclic R(2)(2)(8) amide-amide hydrogen-bonding homodimer motif in this process and provide an additional homodimer motif type in the head-to-tail R(2)(2)(14) association.