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1.  2-Amino-3-carb­oxy­pyrazin-1-ium perchlorate bis­(2-amino­pyrazin-1-ium-3-carboxyl­ate) monohydrate 
The asymmetric unit of the title compound, C5H6N3O2 +·ClO4 −·2C5H5N3O2·H2O, comprises two symmetry-independent zwitterions, one cation, one perchlorate anion and one water mol­ecule. In the crystal, the three different types of organic entities are linked by N—H⋯O and N—H⋯N hydrogen bonds, forming undulating sheets parallel to (1-10). These sheets are in turn connected by O—H⋯N and O—H⋯O hydrogen bonds involving perchlorate anions and water mol­ecules, forming a three-dimensional network. Intra­molecular N—H⋯O and weak inter­molecular C—H⋯O hydrogen bonds are also present.
PMCID: PMC3379306  PMID: 22719504
2.  4-[(E)-2-(2,4-Dichloro­benzyl­idene)hydrazin-1-yl]quinolin-1-ium chloride monohydrate 
In the title hydrated salt, C16H12Cl2N3 +·Cl−·H2O, there is a small twist in the cation as seen in the torsion angle linking the benzene ring to the rest of the mol­ecule [171.96 (17)°]. In the crystal, the quinolinium H atom forms a hydrogen bond to the lattice water mol­ecule, which also forms hydrogen bonds to two Cl− anions. Each Cl− ion also accepts a hydrogen bond from the hydrazine H atom. The three-dimensional architecture is also stabilized by π–π inter­actions between centrosymmetrically related quinoline residues [centroid–centroid distance = 3.5574 (11) Å].
PMCID: PMC3344163  PMID: 22606166
3.  2-Oxo-1,2-dihydro­pyrimidin-3-ium di-μ-chlorido-bis­{dichloridobis[pyrimidin-2(1H)-one-κN 3]cuprate(II)} dihydrate 
The asymmetric unit of the title compound, (C4H5N2O)2[Cu2Cl6(C4H4N2O)2]·2H2O, consists of one cation, one half of a centrosymmetric dianion and one water mol­ecule. The centrosymmetric dianion formed by dimerization in the crystal structure has neutral pyrimidin-2-one ligands coordinated to each copper(II) centre through Cu—N bonds. The Cu atoms each have a distorted trigonal bipyramidal geometry, with the N atom of the pyrimidin-2-one ligand in an axial position, and dimerize by sharing two equatorial Cl atoms. N—H⋯Cl, O—H⋯Cl and N—H⋯O hydrogen bonds connect the anions, cations and water mol­ecules, forming a three-dimensional network.
PMCID: PMC2961836  PMID: 21202780
4.  Bis(5-amino-4-amino­carbonyl-1H-imid­azol-3-ium) (5-amino-4-amino­carbonyl-1H-imidazol-3-ium-κO)-di-μ-chlorido-hepta­chlorido-dibismuth(III) mono­hydrate 
The title compound, (C4H7N4O)2[Bi2Cl9(C4H7N4O)]·H2O, was prepared by the reaction of bis­muth trichloride and 5-amino-1H-imidazole-4-carboxamide in a dilute HCl medium. The asymmetric unit contains two 5-amino-4-amino­carbonyl-1H-imidazol-3-ium cations, one edge-shared non-centrosymmetric biocta­hedral [Bi2C19(C4H7N4O)]2− dianion and a water mol­ecule. In the dianion, the planar 5-amino-4-amino­carbonyl-1H-imidazol-3-ium ligand occupies an equatorial site and is inclined at an angle of 75.7 (2)° to the Bi2(μ-C1)2 plane. The salt forms a three-dimensional network arising from hydrogen bonds between cations, anions and water mol­ecules.
PMCID: PMC2961098  PMID: 21202193
5.  8-Hy­droxy­quinolin-1-ium hydrogen sulfate monohydrate 
In the crystal structure of the title salt hydrate, C9H8NO+·HSO4 −·H2O, the quinoline N—H atoms are hydrogen bonded to the bis­ulfate anions. The bis­ulfate anions and water mol­ecules are linked together by O—H⋯O hydrogen-bonding inter­actions. The cations and anions form separate layers alternating along the c axis, which are linked by N—H⋯O and O—H⋯O hydrogen bonds into a two-dimensional network parallel to (100). Further O—H⋯O contacts connect these layers, forming a three-dimensional network, in which two R 4 4(12) rings and C 2 2(13) infinite chains can be identified.
PMCID: PMC3884397  PMID: 24427083
6.  2-(4-Hy­droxy­phen­yl)-1H-benzimidazol-3-ium chloride monohydrate 
The title mol­ecular salt, C13H11N2O+·Cl−·H2O, crystallizes as a monohydrate. In the cation, the phenol and benzimidazole rings are almost coplanar, making a dihedral angle of 3.18 (4)°. The chloride anion and benzimidazole cation are linked by two N+—H⋯Cl− hydrogen bonds, forming chains propagating along [010]. These chains are linked through O—H⋯Cl hydrogen bonds involving the water mol­ecule and the chloride anion, which form a diamond core, giving rise to the formation of two-dimensional networks lying parallel to (10-2). Two π–π inter­actions involving the imidazolium ring with the benzene and phenol rings [centroid–centroid distances = 3.859 (3) and 3.602 (3) Å, respectively], contribute to this second dimension. A strong O—H⋯O hydrogen bond involving the water mol­ecule and the phenol substituent on the benzimidazole unit links the networks, forming a three-dimensional structure.
PMCID: PMC3884505  PMID: 24427105
7.  2-Isopropyl-6-methyl-4-oxo-3,4-dihydro­pyrimidin-1-ium 2-carb­oxy-4,6-dinitro­phenolate monohydrate 
In the title mol­ecular salt, C8H13N2O+·C7H3N2O7 −·H2O, the pyrimidinium cation is essentially planar, with a maximum deviation of 0.009 (1) Å. The cation undergoes an enol–keto tautomerism during the crystallization. In the crystal, the ion pairs and water mol­ecules are connected via O—H⋯O, N—H⋯O and C—H⋯O hydrogen bonds, forming two-dimensional networks parallel to the bc plane. There is an intra­molecular O—H⋯O hydrogen bond in the 3,5-dinitro­salicylate anion, which generates an S(6) ring motif.
PMCID: PMC3009185  PMID: 21589119
8.  N-(2,6-Dimethyl­anilino)-5,6-dihydro-4H-1,3-thia­zin-3-ium chloride monohydrate 
In the title compound, alternatively called xylazine hydro­chloride monohydrate, C12H17N2S+·Cl−·H2O, the six-membered thia­zine ring is in a half-chair conformation. In the crystal structure, six component centrosymmetric clusters are formed via inter­molecular O—H⋯Cl, N—H⋯O and N—H⋯Cl hydrogen bonds involving xylazine cations, chloride anions and water mol­ecules.
PMCID: PMC2961393  PMID: 21202581
9.  Bis(2,4,6-tri­amino­pyrimidin-1-ium) sulfate penta­hydrate 
The asymmetric unit of the title salt, 2C4H8N5 +·SO4 2−·5H2O, contains four 2,4,6-tri­amino­pyrimidinium (TAPH+) cations, two sulfate anions and ten lattice water mol­ecules. Each two of the four TAPH+ cations form dimers via N—H⋯N hydrogen bonds between the amino groups and the unprotonated pyrimidine N atoms [graph-set motif R 2 2(8)]. The (TAPH+)2 dimers, in turn, form slightly offset infinite π–π stacks parallel to [010], with centroid–centroid distances between pyrimidine rings of 3.5128 (15) and 3.6288 (16) Å. Other amino H atoms, as well as the pyrimidinium N—H groups, are hydrogen-bonded to sulfate and lattice water O atoms. The SO4 2− anions and water mol­ecules are inter­connected with each other via O—H⋯O hydrogen bonds. The combination of hydrogen-bonding inter­actions and π–π stacking leads to the formation of a three-dimensional network with alternating columns of TAPH+ cations and channels filled with sulfate anions and water mol­ecules. One of the sulfate anions shows a minor disorder by a ca 37° rotation around one of the S—O bonds [occupancy ratio of the two sets of sites 0.927 (3):0.073 (3)]. One water mol­ecule is disordered over two mutually exclusive positions with an occupancy ratio of 0.64 (7):0.36 (7).
PMCID: PMC3793762  PMID: 24109349
10.  2,6-Diamino-4-oxo-3,4-dihydropyrim­idin-1-ium chloride dihydrate 
In the crystal structure of the title compound, C4H7N4O+·Cl−·2H2O, adjacent cations are connected to one another through N—H⋯O hydrogen bonds, forming infinite chains along the b axis. These chains are further hydrogen bonded to the chloride anions and water mol­ecules, resulting in a three-dimensional network. The pyrimidine rings of adjacent mol­ecules are arranged in an anti­parallel manner above each other with centroid–centroid distances of 3.435 (1) Å, indicative of π–π inter­actions.
PMCID: PMC3007964  PMID: 21588646
11.  2-Amino-1-(2-carboxyl­atoeth­yl)pyrimidin-1-ium monohydrate 
In the title structure, C7H9N3O2·H2O, there are two formula units in the asymmetric unit. The mol­ecule is a zwitterion, containing a quaternary N atom and a deprotonated carboxyl group, with C—O distances in the range 1.256 (2)–1.266 (3) Å. The two independent mol­ecules form a hydrogen-bonded R 2 2(16) dimer about an approximate inversion center via N—H⋯O hydrogen bonds, with N⋯O distances of 2.766 (2) and 2.888 (2) Å. O—H⋯O hydro­gen bonds involving the water mol­ecules and additional N—H⋯O hydrogen bonds link these dimers, forming double chains.
PMCID: PMC3011485  PMID: 21589454
12.  Bis[2-(4-amino­phen­yl)-4,5-dihydro-1H-imidazol-3-ium] dichloride monohydrate 
The asymmetric unit of the title compound, 2C9H12N3 +·2Cl−·H2O, comprises two mol­ecules, two chloride anions and one mol­ecule of crystal water. In the imidazolinium ring, the protonation contributes to delocalization of the positive charge over the two C—N bonds. Both chloride anions are acceptors of four hydrogen bonds in a flattened tetra­hedron environment. The donors are NH2 groups, the NH groups of the imidazolinium rings and the water mol­ecule. These hydrogen bonds and N—H⋯O(H2O) hydrogen bonds form a three-dimensional network.
PMCID: PMC3239081  PMID: 22199929
13.  Bis(4-meth­oxy-3,4-di­hydro­quinazolin-1-ium) chloranilate 
In the title compound [systematic name: bis­(4-meth­oxy-3,4-di­hydro­quinazolin-1-ium) 2,5-di­chloro-3,6-dioxo­cyclo­hexa-1,4-diene-1,4-diolate], 2C9H11N2O+·C6Cl2O4 2−, the chloranil­ate anion lies about an inversion center. The 4-meth­oxy-3,4-di­hydro­quinazolin-1-ium cations are linked on both sides of the anion via bifurcated N—H⋯(O,O) and weak C—H⋯O hydrogen bonds, giving a centrosymmetric 2:1 aggregate. The 2:1 aggregates are linked by another N—H⋯O hydrogen bond into a tape running along [1-10]. The tapes are further linked by a C—H⋯O hydrogen bond into a layer parallel to the ab plane.
PMCID: PMC3884394  PMID: 24427103
14.  4,9,12,15-Tetra­oxa-3,5,8,10,14,16-hexa­aza­tetra­cyclo­[,6.07,11]hexa­deca-1(16),2,5,7,10,13-hexaen-3-ium-3-olate monohydrate 
The organic mol­ecule in the title monohydrate, C6N6O5·H2O, presents an almost planar configuration, the greatest deviation from the least-squares plane through the atoms being 0.061 (1) Å for the O atom within the seven-membered ring. Each water H atom is bifurcated, one forming two O—H⋯N hydrogen bonds and the other forming O—H⋯N,O hydrogen bonds. The result of the hydrogen bonding is the formation of supra­molecular layers with a zigzag topology that stack along [001].
PMCID: PMC3297919  PMID: 22412722
15.  5-Carb­oxy-2-isopropyl-1H-imidazol-3-ium-4-carboxyl­ate monohydrate 
In the title compound, C8H10N2O4·H2O, the imidazole N atom is protonated and one of the carboxyl­ate groups is deprotoned, forming a zwitterion. An intra­molecular O—H⋯O hydrogen bond occurs. The crystal structure is stabilized by inter­molecular N—H⋯O and O—H⋯O hydrogen bonds. In addition, inter­molecular N—H⋯O and O—H⋯O hydrogen bonds link the mol­ecules into two-dimensional networks parallel to (10).
PMCID: PMC3152056  PMID: 21837204
16.  5-Amino-3-carb­oxy-1H-1,2,4-triazol-4-ium nitrate monohydrate 
The two-dimensional crystal packing of the title compound, C3H5N4O2 +·NO2 −·H2O, results from the stacking of well separated layers (i.e. with nothing between the layers) parallel to the (-113) plane in which adjacent cations adopt a head-to-head arrangement such that two –COOH groups are linked via two water mol­ecules (the water O atom behaves simultaneously as donor and acceptor of hydrogen bonds) and two –NH2 groups are linked through two nitrate anions. This arrangement leads to alternating hydro­philic and hydro­phobic zones in which O—H⋯O and N—H⋯O hydrogen bonds, respectively, are observed.
PMCID: PMC3344063  PMID: 22589972
17.  7-(2,2-Dimethylpropanamido)-2-methyl-1,8-naphthyridin-1-ium chloride monohydrate 
The asymmetric unit of the title compound, C14H18N3O+·Cl−·H2O, comprises a substituted amido–naphthyridine cation, a chloride anion and a water mol­ecule of crystallization. Intra­molecular C—H⋯O hydrogen bonds generate six-membered rings, producing an S(6) ring motif. The amido group is twisted from the naphthyridine ring, making a dihedral angle of 17.65 (7)°. The crystal structure is stabilized by inter­molecular N—H⋯O, N—H⋯Cl, O—H⋯Cl (× 2), and C—H⋯O (× 2) hydrogen bonds. These inter­actions linked neighbouring mol­ecules into chains along the a and b axes of the crystal, thus forming mol­ecular sheets parallel to the (001) plane.
PMCID: PMC2968242  PMID: 21581941
18.  Bis(5-amino-3-carb­oxy-1H-1,2,4-triazol-4-ium) dihydrogenphosphate nitrate 5-amino-1H-1,2,4-triazol-4-ium-3-carboxyl­ate 
In the title compound, 2C3H5N4O2 +·H2PO4 −·NO3 −·C3H4N4O2, three independent 5-amino-1H-1,2,4-triazol-3-carb­oxy­lic acid moieties are observed. Two are in the form of cations, while the third is in the zwitterionic form. The triazole rings in the two cations are almost coplanar, making an angle of 4.11 (7)°. Layers parallel to the (20-1) plane, resulting from hydrogen bonding of the organic mol­ecules and the nitrate anions, are linked via H2PO4 − infinite zigzag chains running parallel to the c axis. The crystal studied was an inversion twin, with refined components of 0.33 (7) and 0.67 (7).
PMCID: PMC3344471  PMID: 22590233
19.  3,4,7,8-Tetra­methyl-1,10-phenanthrolin-1-ium nitrate monohydrate 
In the crystal of the title compound, C16H17N2 +·NO3 −·H2O, the tetra­methyl-1,10-phenanthrolinium cations, nitrate anions and lattice water mol­ecules are all located on a mirror plane with the methyl H atoms of the cation equally disordered over two sites about the mirror plane. The cation, anion and water mol­ecule are linked by O—H⋯O and N—H⋯O hydrogen bonds into a sheet parallel to the bc plane. π–π stacking between phenanthroline ring systems is observed in the crystal structure, the centroid–centroid distance being 3.4745 (6) Å.
PMCID: PMC3379486  PMID: 22719684
20.  2-Ethyl-1H-imidazol-3-ium hemioxalate oxalic acid monohydrate 
In the title compound, C5H9N2 +·0.5C2O4 2−·C2H2O4·H2O, the anions, cations and water mol­eculars are linked by N—H⋯O and O—H⋯O hydrogen bonds which define a tightly bound three-dimensional structure. The title compound is a layered structure as viewed along the a or c axis; one layer contains water and oxalic acid mol­ecules, the other the imidazolium cation. The C atoms of the ethyl group of the 2-ethyl­imidazolium cation are disordered over two positions of equal occupancy.
PMCID: PMC3152088  PMID: 21837033
21.  1H-Imidazo[4,5-f][1,10]phenanthrolin-7-ium perchlorate monohydrate 
In the title crystal structure, C13H9N4 +·ClO4 −·H2O, cations, anions and water mol­ecules are linked through inter­molecular N—H⋯O, O—H⋯N and O—H⋯O hydrogen bonds, forming layers parallel to (001). In addition, there are weak π–π stacking inter­actions between the layers, involving the cations and with centroid–centroid distances in the range 3.584 (2)–3.662 (2) Å, forming a three-dimensional network.
PMCID: PMC2970354  PMID: 21577803
22.  1-(5-Carboxy­pent­yl)-2,3,3-trimethyl-3H-indol-1-ium bromide monohydrate 
In the title compound, C17H24NO2 +·Br−·H2O, the pentyl group chain in the cation extends nearly perpendicular [N—C—C—C = −64.4 (3)°] to the mean plane of the indole ring with the carboxyl end group twisted such that the dihedral angle between the mean planes of the indole and carb­oxy groups measures 43.2 (4)°. Both ions in the salt form inter­molecular hydrogen bonds (O—H⋯Br and O—H⋯O) with the water mol­ecule. As a result of the Br⋯H—O—H⋯Br inter­actions, a zigzag chain is formed in the c-axis direction. The crystal packing is influenced by the collective action of the O—H⋯O and O—H⋯Br inter­molecular inter­actions as well as π–π stacking inter­molecular inter­actions between adjacent benzyl rings of the indole group [centroid–centroid distance = 3.721 (13) Å] and inter­molecular C—H⋯π inter­actions between a methyl hydrogen and the benzyl ring of the indole group. The O—H⋯Br inter­actions form a distorted tetra­hedral array about the central Br atom. A MOPAC AM1 calculation provides support to these observations.
PMCID: PMC2980276  PMID: 21580058
23.  Penta­kis(2-oxo-2,3-dihydro­pyrimidin-1-ium) di-μ3-chlorido-tri-μ2-chlorido-hexa­chloridotricadmate(II) 
The title compound, (C4H5N2O)5[Cd3Cl11], was obtained from the reaction of 2-hydroxy­pyrimidine hydro­chloride and cadmium(II) chloride in concentrated HCl solution. The crystal structure consists of planar 2-oxo-1,2-dihydro­pyrimidin-3-ium cations with both N atoms protonated and the O atom unprotonated, and a complex trinuclear [Cd3Cl11]5− anion of approximately D 3h symmetry, which has a triangle of three octa­hedrally coordinated CdII centres bonded to 11 chloride ions. Three of the chloride ions bridge adjacent Cd atoms, two cap the faces of the Cd3 triangle and the remaining six are terminally bonded and act as hydrogen-bond acceptors. Various N—H⋯Cl hydrogen bonds connect the anions and cations and, in addition, inter­molecular N—H⋯O hydrogen bonds contribute to the formation of a three-dimensional network.
PMCID: PMC2961797  PMID: 21202808
24.  2-Amino-5-ethoxy­carbonyl-4-methyl­thia­zol-3-ium chloride monohydrate 
In the crystal structure of the title compound, C7H11N2O2S+·Cl−·H2O, the cations, anions and water mol­ecules are linked by inter­molecular N—H⋯O, N—H⋯Cl, O—H⋯O and O—H⋯Cl hydrogen bonds, forming layers stacked along [20].
PMCID: PMC2977512  PMID: 21583464
25.  1-Carboxy­methyl-2-ethyl-4-methyl-1H-imidazol-3-ium chloride monohydrate 
In the title compound, C8H13N2O2 +·Cl−·H2O, the methyl C atom of the ethyl group is slightly out of the imidazole plane, with an N—C(ring)—C—C torsion angle of −15.1 (2)°. In the crystal structure, there are strong inter­molecular hydrogen-bonding inter­actions between the solvent water mol­ecule, the free chloride anion and the organic cation, resulting in a two-dimensional supra­molecular network in the ab plane.
PMCID: PMC2977760  PMID: 21583896

Results 1-25 (648577)