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1.  Investigation of supramolecular synthons and structural characterisation of aminopyridine-carboxylic acid derivatives 
Background
Co-crystal is a structurally homogeneous crystalline material that contains two or more neutral building blocks that are present in definite stoichiometric amounts. The main advantage of co-crystals is their ability to generate a variety of solid forms of a drug that have distinct physicochemical properties from the solid co-crystal components. In the present investigation, five co-crystals containing 2-amino-6-chloropyridine (AMPY) moiety were synthesized and characterized.
Results
The crystal structure of 2-amino-6-chloropyridine (AMPY) (I), and the robustness of pyridine-acid supramolecular synthon were discussed in four stoichiometry co-crystals of AMPY…BA (II), AMPY…2ABA (III), AMPY…3CLBA (IV) and AMPY…4NBA (V). The abbreviated designations used are benzoic acid (BA), 2-aminobenzoic acid (2ABA), 3-chlorobenzoic acid (3CLBA) and 4-nitrobenzoic acid (4NBA). All the crystalline materials have been characterized by 1HNMR, 13CNMR, IR, photoluminescence, TEM analysis and X-ray diffraction. The supramolecular assembly of each co-crystal is analyzed and discussed.
Conclusions
Extensive N---H · · · N/N---H · · · O/O---H · · · N hydrogen bonds are found in (I-V), featuring different supramolecular synthons. In the crystal structure, for compound (I), the 2-amino-6-chloropyridine molecules are linked together into centrosymmetric dimers by hydrogen bonds to form homosynthon, whereas for compounds (II-V), the carboxylic group of the respective acids (benzoic acid, 2-aminobenzoic acid, 3-chlorobenzoic acid and 4-nitrobenzoic acid) interacts with pyridine molecule in a linear fashion through a pair of N---H · · · O and O---H · · · N hydrogen bonds, generating cyclic hydrogen-bonded motifs with the graph-set notation
, to form heterosynthon. In compound (II), another intermolecular N---H · · · O hydrogen bonds further link these heterosynthons into zig-zag chains. Whereas in compounds (IV) and (V), these heterosynthons are centrosymmetrically paired via N---H · · · O hydrogen bonds and each forms a complementary DADA [D = donor and A = acceptor] array of quadruple hydrogen bonds, with graph-set notation, and .
Electronic supplementary material
The online version of this article (doi: 10.1186/1752-153X-8-31) contains supplementary material, which is available to authorized users.
doi:10.1186/1752-153X-8-31
PMCID: PMC4032391  PMID: 24887234
2.  Investigation of supramolecular synthons and structural characterisation of aminopyridine-carboxylic acid derivatives 
Background
Co-crystal is a structurally homogeneous crystalline material that contains two or more neutral building blocks that are present in definite stoichiometric amounts. The main advantage of co-crystals is their ability to generate a variety of solid forms of a drug that have distinct physicochemical properties from the solid co-crystal components. In the present investigation, five co-crystals containing 2-amino-6-chloropyridine (AMPY) moiety were synthesized and characterized.
Results
The crystal structure of 2-amino-6-chloropyridine (AMPY) (I), and the robustness of pyridine-acid supramolecular synthon were discussed in four stoichiometry co-crystals of AMPY…BA (II), AMPY…2ABA (III), AMPY…3CLBA (IV) and AMPY…4NBA (V). The abbreviated designations used are benzoic acid (BA), 2-aminobenzoic acid (2ABA), 3-chlorobenzoic acid (3CLBA) and 4-nitrobenzoic acid (4NBA). All the crystalline materials have been characterized by 1HNMR, 13CNMR, IR, photoluminescence, TEM analysis and X-ray diffraction. The supramolecular assembly of each co-crystal is analyzed and discussed.
Conclusions
Extensive N---H · · · N/N---H · · · O/O---H · · · N hydrogen bonds are found in (I-V), featuring different supramolecular synthons. In the crystal structure, for compound (I), the 2-amino-6-chloropyridine molecules are linked together into centrosymmetric dimers by hydrogen bonds to form homosynthon, whereas for compounds (II-V), the carboxylic group of the respective acids (benzoic acid, 2-aminobenzoic acid, 3-chlorobenzoic acid and 4-nitrobenzoic acid) interacts with pyridine molecule in a linear fashion through a pair of N---H · · · O and O---H · · · N hydrogen bonds, generating cyclic hydrogen-bonded motifs with the graph-set notation
R228
, to form heterosynthon. In compound (II), another intermolecular N---H · · · O hydrogen bonds further link these heterosynthons into zig-zag chains. Whereas in compounds (IV) and (V), these heterosynthons are centrosymmetrically paired via N---H · · · O hydrogen bonds and each forms a complementary DADA [D = donor and A = acceptor] array of quadruple hydrogen bonds, with graph-set notation R238, R228 and R238.
doi:10.1186/1752-153X-8-31
PMCID: PMC4032391  PMID: 24887234
3.  N′-[(1E,2E)-3,7-Dimethyl­octa-2,6-dien-1-yl­idene]pyridine-4-carbohydrazide 
In the title compound, C16H21N3O, the mol­ecule adopts an E conformation about the central C=N double bond. The 2-methyl­pent-2-ene group is disordered over two sets of sites, with a refined occupancy ratio of 0.785 (8):0.215 (8). The dihedral angle between the essentially planar [the r.m.s. value for the major component is 0.021 (7) and its maximum deviation is 0.025 (4) Å; the r.m.s. value for the minor component is 0.03 (4) and its maximum deviation is 0.05 (3) Å] major and minor components of the 2-methyl­but-2-ene group is 35.9 (13)°. In the crystal, C—H⋯O and N—H⋯O hydrogen bonds link the molecules, with the same O atom acting as the acceptor. This results in C 1 1(4) and C 1 1(5) [001] chains.
doi:10.1107/S1600536812009075
PMCID: PMC3344089  PMID: 22606092
4.  (E)-2-(2,3-Dimethyl­anilino)-N′-[2-methyl-5-(prop-1-en-2-yl)cyclo­hex-2-enyl­idene]benzohydrazide 
The asymmetric unit of the title compound, C25H29N3O, comprises two crystallographically independent mol­ecules. The dihedral angles between the benzene rings in the two mol­ecules are 59.7 (2) and 61.27 (18)°. The cyclo­hexene rings adopt sofa and half-chair conformations. In the crystal, mol­ecules are connected via N—H⋯O and weak C—H⋯O hydrogen bonds, forming chains along the a axis. In each mol­ecule, there is an intra­molecular N—H⋯O hydrogen bond.
doi:10.1107/S1600536812009087
PMCID: PMC3344081  PMID: 22606084
5.  (E)-N′-(4-Isopropyl­benzyl­idene)isonicotinohydrazide monohydrate 
In the title compound, C16H17N3O·H2O, the isonicotinohydrazide mol­ecule adopts an E conformation about the central C=N double bond. The dihedral angle between the pyridine and the benzene rings is 54.56 (15)°. In the crystal, mol­ecules are connected via N—H⋯O, O—H⋯N and O—H⋯O hydrogen bonds, forming a three-dimensional network.
doi:10.1107/S1600536812009099
PMCID: PMC3343969  PMID: 22589878
6.  catena-Poly[[[aqua­manganese(III)]-μ-(E)-5-bromo-N-[2-(5-bromo-2-oxidobenzyl­idene­amino)-4-nitro­phen­yl]-2-oxidobenzamidato] N,N-dimethyl­fomamide monosolvate] 
The asymmetric unit of the title complex, {[Mn(C20H10Br2N3O5)(H2O)]·(CH3)2NCHO}n, consists of one MnIII ion, one (E)-5-bromo-N-[2-(5-bromo-2-oxidobenzyl­idene­amino)-4-nitro­phen­yl]-2-oxidobenzamidate ligand (Schiff base), one water mol­ecule and an N,N-dimethyl­formamide mol­ecule. The coordination geometry around the MnIII ion is a distorted octa­hedron, being surrounded by two O and two N atoms from the Schiff base, which are positioned in the equatorial plane. The water mol­ecule and the O atom of the carbonyl group from the adjacent MnIII complex are situated at the axial positions, leading to a polymeric chain along the c axis. In the crystal, the complex and N,N-dimethyl­formamide mol­ecules are connected via O—H⋯O, C—H⋯O and C—H⋯Br hydrogen bonds, forming a three-dimensional network.
doi:10.1107/S1600536812008501
PMCID: PMC3343787  PMID: 22589761
7.  (1Z,2E)-N′-{2-Chloro-1-methyl-2-[2-(4-methyl­phen­yl)hydrazin-1-yl­idene]ethyl­idene}-4-meth­oxy­benzohydrazide 
The asymmetric unit of the title compound, C18H19ClN4O2, contains two mol­ecules, in which the dihedral angles between the benzene rings are 43.60 (12) and 58.65 (13)°. The hydrazine N atoms are twisted slightly out of the planes of the tolyl and meth­oxy­benzene rings: the C—C—N—N and N—N—C—C torsion angles are 171.1 (2) and −174.4 (2)°, respectively, for one mol­ecule and −177.4 (2) and −170.6 (2)°, respectively, for the other. In the crystal, mol­ecules are linked by N—H⋯O and C—H⋯O hydrogen bonds into chains propagating along the b-axis direction.
doi:10.1107/S1600536812008367
PMCID: PMC3343910  PMID: 22589991
8.  Absolute configuration of (1S,2S)-3-methyl-2-phenyl-2,3-dihydro­thia­zolo[2,3-b]quinazolin-5-one 
The absolute structure of the molecule in the crystal of the title compound, C17H14N2OS, was determined by the refinement of the Flack parameter to 0.0 (2) based on 1011 Friedel pairs. The quinazoline ring is essentially planar, with a maximum deviation of 0.037 (2) Å. The thia­zole ring is distorted from planarity [maximum deviation = 0.168 (2) Å] and adopts a slightly twisted envelope conformation, with the C atom as the flap atom. The central thia­zole ring makes dihedral angles of 7.01 (8) and 76.80 (10)° with the quinazoline and phenyl rings, respectively. The corresponding angle between the quinazoline and phenyl rings is 3.74 (9)°. In the crystal, there are no classical hydrogen bonds but stabilization is provided by weak C—H⋯π inter­actions, involving the centroids of the phenyl rings.
doi:10.1107/S160053681200832X
PMCID: PMC3343911  PMID: 22589992
9.  3-Benzyl-6-methyl-2-sulfanylidene-2,3-di­hydroquinazolin-4(1H)-one 
In the title compound, C16H14N2OS, the quinazoline ring system is essentially planar, with a maximum deviation of 0.029 (3) Å. The dihedral angle between the quinazoline and benzene rings is 88.4 (2)°. In the crystal, adjacent mol­ecules are connected via pairs of N—H⋯S and C—H⋯O hydrogen bonds, which generate R 2 2(8) and R 2 2(10) graph-set motifs, respectively, resulting in a supra­molecular chain along the a axis.
doi:10.1107/S1600536812006009
PMCID: PMC3295489  PMID: 22412600
10.  4-Methyl-2-oxo-2H-chromen-7-yl 4-fluoro­benzene­sulfonate 
In the asymmetric unit of the title compound, C16H11FO5S, the 2H-chromene ring is essentially planar, with a maximum deviation of 0.040 (2) Å. The dihedral angle between the 2H-chromene ring and the 4-fluoro­phenyl ring is 2.17 (8)°. One of the sulfonamide O atoms is approximately coplanar with the benzene ring [C—C—S—O torsion angle = 166.00 (14)°], whereas the other O atom lies well below the plane [C—C—S—O = −61.35 (17)°]. In the crystal, mol­ecules are connected by weak C—H⋯O hydrogen bonds, forming two-dimensional networks parallel to the ac plane.
doi:10.1107/S1600536812004394
PMCID: PMC3295434  PMID: 22412545
11.  3,3′-[1,2-Phenyl­enebis(methyl­ene)]bis­(1-ethyl­benzimidazolium) dibromide 
In the title mol­ecular salt, C26H28N4 2+·2Br−, the central benzene ring makes dihedral angles of 76.75 (11) and 82.40 (10)° with the pendant benzimidazole rings. The corresponding angle between the benzimidazole rings is 57.03 (9)°. In the crystal, the cations and anions are linked via C—H⋯Br hydrogen bonds, forming sheets lying parallel to the bc plane. The crystal structure also features weak C—H⋯π inter­actions.
doi:10.1107/S1600536812002802
PMCID: PMC3297300  PMID: 22412490
12.  Methyl N-({[2-(2-meth­oxy­acetamido)-4-(phenyl­sulfan­yl)phen­yl]amino}[(meth­oxy­carbonyl)imino]methyl)carbamate 
In the title compound, C20H22N4O6S, the phenyl and benzene rings form a dihedral angle of 58.75 (5)°. Intra­molecular N—H⋯O and N—H⋯N hydrogen bonds generate two S(6) and one S(7) ring motif, respectively. In the crystal, mol­ecules are linked via N—H⋯O, N—H⋯N, C—H⋯S and C—H⋯O hydrogen bonds, forming two-dimensional networks parallel to the bc plane.
doi:10.1107/S1600536812002760
PMCID: PMC3297308  PMID: 22412498
13.  5-Isopropyl­imidazolidine-2,4-dione monohydrate 
In the title compound, C6H10N2O2·H2O, the imidazole ring is essentially planar, with a maximum deviation of 0.012 (2) Å. In the crystal, mol­ecules are connected via N—H⋯O and O—H⋯O hydrogen bonds, forming a supra­molecular tape along the a axis.
doi:10.1107/S1600536812002838
PMCID: PMC3275273  PMID: 22347129
14.  3-Acetyl-1-(3-methyl­phen­yl)-5-phenyl-1H-pyrazole-4-carbonitrile 
In the title compound, C19H15N3O, the central pyrazole ring makes dihedral angles of 35.52 (12) and 62.21 (11)° with the attached phenyl and methyl-substituted phenyl rings, respectively. The corresponding angle between the phenyl and methyl-substituted phenyl rings is 62.90 (11)°. In the crystal, mol­ecules are connected by weak C—H⋯O hydrogen bonds, forming supra­molecular chains propagating along the a-axis direction.
doi:10.1107/S160053681200181X
PMCID: PMC3275233  PMID: 22347089
15.  Bis(2,3-diamino­pyridinium) phthalate dihydrate 
The complete anion of the title hydrated mol­ecular salt, 2C5H8N3 +·C8H4O4 −·2H2O, is generated by a crystallographic twofold axis. In the crystal, the cations, anions and water mol­ecules are connected by N—H⋯O, O—H⋯O and C—H⋯O hydrogen bonds, forming a three-dimensional network. The crystal structure also features C—H⋯π inter­actions.
doi:10.1107/S1600536811055838
PMCID: PMC3275077  PMID: 22347022
16.  Diisobutyl 4-(3-eth­oxy-4-hy­droxy­phen­yl)-2,6-dimethyl-1,4-dihydro­pyridine-3,5-dicarboxyl­ate 
The asymmetric unit of the title compound, C25H35NO6, contains two independent mol­ecules. In each mol­ecule, the 1,4-dihydro­pyridine ring adopts a flattened boat conformation. The dihedral angles between the 1,4-dihydro­pyridine and benzene rings are 87.55 (7) and 87.23 (7)°. In one of these mol­ecules, one of the isobutyl groups is disordered over two sets of sites, with an occupancy ratio of 0.890 (2):0.110 (2). In the crystal, mol­ecules are linked through N—H⋯O, O—H⋯O and C—H⋯O hydrogen bonds forming two-dimensional networks parallel to the ab plane. The crystal structure is further stabilized by weak C—H⋯π inter­actions.
doi:10.1107/S1600536811055334
PMCID: PMC3274982  PMID: 22346927
17.  2,3-Diamino­pyridinium sorbate–sorbic acid (1/1) 
In the title mol­ecular salt–adduct, C5H8N3 +·C6H7O2 −·C6H8O2, the 2,3-diamino­pyridinium cation is essentially planar, with a maximum deviation of 0.013 (2) Å, and is protanated at its pyridine N atom. The sorbate anion and sorbic acid mol­ecules exist in extended conformations. In the crystal, the protonated N atom and one of the two amino-group H atoms are hydrogen bonded to the sorbate anion through a pair of N—H⋯O hydrogen bonds, forming an R 1 2(6) ring motif. The carboxyl groups of the sorbic acid mol­ecules and the carboxyl­ate groups of the sorbate anions are connected via O—H⋯O hydrogen bonds. Furthermore, the ion pairs and neutral mol­ecules are connected via inter­molecular N—H⋯O hydrogen bonds, forming sheets lying parallel to (100).
doi:10.1107/S1600536811053025
PMCID: PMC3254524  PMID: 22259470
18.  1-(4,4′′-Difluoro-5′-meth­oxy-1,1′:3′,1′′-terphenyl-4′-yl)ethanone 
In the title compound, C21H16F2O2, the central benzene ring is inclined at dihedral angles of 30.91 (8) and 46.88 (7)° to the two terminal fluoro-substituted rings. The dihedral angle between the two terminal fluoro-subsituted rings is 68.34 (8)°. An intra­molecular C—H⋯O hydrogen bond generates an S(6) ring motif. The crystal structure is stabilized by weak C—H⋯π inter­actions.
doi:10.1107/S1600536811053037
PMCID: PMC3254504  PMID: 22259448
19.  2-Amino-5-chloro­pyrimidin-1-ium hydrogen maleate 
In the title salt, C4H5ClN3 +·C4H3O4 −, the 2-amino-5-chloro­pyrimidinium cation is protonated at one of its pyrimidine N atoms. In the roughly planar (r.m.s. deviation = 0.026 Å) hydrogen malate anion, an intra­molecular O—H⋯O hydrogen bond generates an S(7) ring. In the crystal, the protonated N atom and the 2-amino group of the cation are hydrogen bonded to the carboxyl­ate O atoms of the anion via a pair of N—H⋯O hydrogen bonds, forming an R 2 2(8) ring motif. The ion pairs are connected via further N—H⋯O hydrogen bonds and a short C—H⋯O inter­action, forming layers lying parallel to the bc plane.
doi:10.1107/S1600536811051646
PMCID: PMC3254455  PMID: 22259394
20.  4-Methyl-2-oxo-2H-chromen-7-yl 4-meth­oxy­benzene­sulfonate 
In the title compound, C17H14O6S, the 2H-chromene ring is essentially planar, with a maximum deviation of 0.016 (1) Å. The dihedral angle between the 2H-chromene and the benzene rings is 54.61 (5)°. The C atom of the meth­oxy group is close to coplanar with its attached ring [deviation = 0.082 (2) Å]. In the crystal, mol­ecules are connected via C—H⋯O hydrogen bonds, forming sheets lying parallel to the bc plane. Weak C—H⋯π inter­actions are also observed.
doi:10.1107/S1600536811049476
PMCID: PMC3239087  PMID: 22199935
21.  1,3-Bis(2-cyano­benz­yl)imidazolium bromide 
In the title salt, C19H15N4 +·Br−, the central imidazole ring makes dihedral angles of 83.1 (2) and 87.6 (2)° with the terminal benzene rings. The dihedral angle between the terminal benzene rings is 6.77 (19)°; the cyanide substituents have an anti orientation. In the crystal, the cations and anions are linked via C—H⋯N and C—H⋯Br hydrogen bonds, forming sheets lying parallel to the ac plane.
doi:10.1107/S1600536811048951
PMCID: PMC3239090  PMID: 22199938
22.  2,3-Diamino­pyridinium 3-chloro­benzo­ate–3-chloro­benzoic acid (1/1) 
The asymmetric unit of the title compound, C5H8N3 +·C7H4ClO2 −·C7H5ClO2, contains an ion pair and a 3-chloro­benzoic acid mol­ecule. In the cation, the pyridine N atom is protonated. In the crystal, the components are connected via N—H⋯O, O—H⋯O and C—H⋯O hydrogen bonds, thereby forming sheets lying parallel to (100).
doi:10.1107/S1600536811050422
PMCID: PMC3239122  PMID: 22199970
23.  Ethyl 7-pivaloyl­amino-1,8-naphthyridine-2-carboxyl­ate sesquihydrate 
In the title hydrate, C16H19N3O3·1.5H2O, both water mol­ecules are disordered: one over two adjacent sites in a 0.498 (5):0.502 (5) ratio and one lying near a crystallographic twofold axis. The dihedral angle between the pyridine rings of the organic moleucle is 1.47 (6)°. In the crystal, the components are linked by N—H⋯O, O—H⋯N and C—H⋯O hydrogen bonds, forming sheets lying parallel to the ac plane.
doi:10.1107/S160053681104921X
PMCID: PMC3239052  PMID: 22199900
24.  (E)-1-(4,4′′-Difluoro-5′-meth­oxy-1,1′:3′,1′′-terphenyl-4′-yl)-3-(6-meth­oxy­naphthalen-2-yl)prop-2-en-1-one 
In the title compound, C33H24F2O3, the central benzene ring makes dihedral angles of 44.71 (10), 47.80 (10) and 63.68 (9)° with the two fluoro-substituted benzene rings and the naphthalene ring system, respectively. In the crystal, mol­ecules are connected via inter­molecular C—H⋯F and C—H⋯O hydrogen bonds. Furthermore, the crystal structure is stabilized by weak C—H⋯π and π–π inter­actions [centroid–centroid distance = 3.6816 (13) Å].
doi:10.1107/S1600536811047660
PMCID: PMC3238976  PMID: 22199825
25.  6-Fluoro-2-(4-meth­oxy­phen­yl)imidazo[2,1-b][1,3]benzothia­zole 
The asymmetric unit of the title compound, C16H11FN2OS, comprises two independent mol­ecules in which the benzothia­zole rings are essentially planar, with maximum deviations of 0.038 (2) and 0.045 (3) Å. The central benzothia­zole ring makes dihedral angles of 4.87 (13) and 0.64 (12)° and 4.04 (12) and 3.67 (12)° with the two terminal phenyl rings in the two independent mol­ecules. In the crystal, mol­ecules are connected via weak inter­molecular C—H⋯O hydrogen bonds forming supra­molecular chains along the c axis.
doi:10.1107/S1600536811046666
PMCID: PMC3238924  PMID: 22199773

Results 1-25 (206)