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1.  Crystal structure of tetra­aqua­bis(3,5-di­amino-4H-1,2,4-triazol-1-ium)cobalt(II) bis­[bis­(pyridine-2,6-di­carboxyl­ato)cobaltate(II)] dihydrate 
The asymmetric unit of the title compound, [Co(C2H6N5)2(H2O)4][Co(C7H3NO4)2]2·2H2O, features 1.5 CoII ions (one anionic complex and one half cationic complex) and one water mol­ecule. In the cationic complex, the CoII atom is located on an inversion centre and is coordinated by two triazolium cations and four water mol­ecules, adopting an octa­hedral geometry where the N atoms of the two triazolium cations occupy the axial positions and the O atoms of the four water mol­ecules the equatorial positions. The two triazole ligands are parallel offset (with a distance of 1.38 Å between their planes). In the anionic complex, the CoII ion is six-coordinated by two N and four O atoms of the two pyridine-2,6-di­carboxyl­ate anions, exhibiting a slightly distorted octa­hedral coordination geometry in which the mean plane of the two pyridine-2,6-di­carboxyl­ate anions are almost perpendicular to each other, making a dihedral angle of 85.87 (2)°. In the crystal, mol­ecules are linked into a three-dimensional network via C—H⋯O, C—H⋯N, O—H⋯O and N—H⋯O hydrogen bonds.
doi:10.1107/S2056989015010014
PMCID: PMC4459343  PMID: 26090171
crystal structure; pyridine-2,6-di­carboxyl­ate; triazolium; CoII complex; hydrogen bonding
2.  Synthesis, Structural and Antioxidant Studies of Some Novel N-Ethyl Phthalimide Esters 
PLoS ONE  2015;10(3):e0119440.
A series of N-ethyl phthalimide esters 4(a-n) were synthesized and characterized by spectroscopic studies. Further, the molecular structure of majority of compounds were analysed by single crystal X-ray diffraction studies. The X-ray analysis revealed the importance of substituents on the crystal stability and molecular packing. All the synthesized compounds were tested for in vitro antioxidant activity by DPPH radical scavenging, FRAP and CUPRAC methods. Few of them have shown good antioxidant activity.
doi:10.1371/journal.pone.0119440
PMCID: PMC4351070  PMID: 25742494
3.  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
4.  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
5.  1-[5-(2H-1,3-Benzodioxol-5-yl)-3-(4-methyl­phen­yl)-2-pyrazolin-1-yl]ethanone 
In the title compound, C19H18N2O3, the pyrazoline ring is close to being planar (r.m.s. deviation = 0.035 Å) and subtends dihedral angles of 2.11 (8) and 82.63 (8)° with the p-tolyl and benzene rings, respectively. In the crystal, C—H⋯O and C—H⋯N hydrogen bonds link the mol­ecules, forming a three-dimensional network. A weak C—H⋯π inter­action involving the benzene ring is also observed.
doi:10.1107/S1600536813008817
PMCID: PMC3648258  PMID: 23723878
6.  3-(4-Methyl­phen­yl)-4-[(thio­semi­carba­zono)meth­yl]-1,2,3-oxa­diazol-3-ium-5-olate 1,4-dioxane hemisolvate 
The asymmetric unit of the title compound, C11H11N5O2S·0.5C4H8O2, contains one 3-(p-tol­yl)sydnone 4-thio­semi­carba­zone mol­ecule and a half mol­ecule of 1,4-dioxane, which lies abount an inversion centre. The sydnone ring is almost planar, with a maximum deviation of 0.002 (1) Å, and forms a dihedral angle of 46.31 (5)° with the benzene ring. In the crystal, the two components are linked into a tape along [01-1] by N—H⋯O and N—H⋯S hydrogen bonds. The crystal structure is further stabilized by C—H⋯O and C—H⋯π inter­actions, forming a three-dimensional network.
doi:10.1107/S1600536813008805
PMCID: PMC3648259  PMID: 23723879
7.  Bis­(3,5-diamino-4H-1,2,4-triazol-1-ium) 3,4-dioxocyclo­butane-1,2-diolate 
The asymmetric unit of the title compound, 2C2H6N5 +·C4O4 2−, contains two 3,5-diamino-4H-1,2,4-triazolium cations and one squarate dianion. The squaric acid mol­ecule donated one H atom to each of the two 3,5-diamino-1,2,4-triazole mol­ecules at their N atoms. The squaric acid dianion has four C—O bonds which are shorter than a normal single C—O bond (1.426 Å) and are slightly longer than a normal C=O bond (1.23 Å), which indicates the degree of electron delocalization in the dianion. In the crystal, the cations and dianions are linked by N—H⋯N and N—H⋯O hydrogen bonds into a three-dimensional network.
doi:10.1107/S160053681300322X
PMCID: PMC3588514  PMID: 23476545
8.  (2E)-1-[2,3-Dichloro-6-methyl-5-(trifluoro­meth­yl)phen­yl]-2-(1-phenyl­ethyl­idene)hydrazine 
The title compound, C16H13Cl2F3N2, exists in an E conformation with respect to the C=N bond [1.2952 (11) Å] and the C—N—N=C torsion angle is 175.65 (8)°. The dihedral angle between the benzene rings is 42.09 (4)°. An intra­molecular C—H⋯F hydrogen bond generates an S(6) ring. In the crystal, the mol­ecules are linked into [101] chains by C—H⋯F hydrogen bonds.
doi:10.1107/S1600536812042419
PMCID: PMC3515280  PMID: 23284500
9.  2-(4-Meth­oxy­phenyl)-2-oxoethan­aminium chloride 
In the cation of the title compound, C9H12NO2 +·Cl−, the dihedral angle between the 2-oxoethanaminium N—C—C(=O)– plane [maximum deviation = 0.0148 (12) Å] and the benzene ring is 7.98 (8)°. The meth­oxy group is approximately in-plane with the benzene ring, with a C—O—C—C torsion angle of −2.91 (18)°. In the crystal, the cations and chloride anions are connected by N—H⋯Cl and C—H⋯Cl hydrogen bonds, forming a layer parallel to the bc plane. A C—H⋯π inter­action further links the layers.
doi:10.1107/S1600536812039645
PMCID: PMC3470349  PMID: 23125762
10.  2-Cyclo­pentyl­idenehydrazine­carboxamide 
The asymmetric unit of the title compound, C6H11N3O, consists of two independent mol­ecules in which the cyclo­pentane rings adopt envelope conformations with CH2 grouping as the flap and the semicarbazone groups are essentially planar, with maximums deviation of 0.0311 (12) and 0.0285 (12) Å. In the crystal, N—H⋯O, N—H⋯N and C—H⋯O hydrogen bonds link the mol­ecules to form sheets lying parallel to the ab plane.
doi:10.1107/S1600536812034599
PMCID: PMC3435698  PMID: 22969569
11.  1-[5-(4-Bromo­phen­yl)-3-(4-fluoro­phen­yl)-4,5-dihydro-1H-pyrazol-1-yl]butan-1-one 
In the title compound, C19H18BrFN2O, the benzene rings form dihedral angles of 5.38 (7) and 85.48 (7)° with the mean plane of the 4,5-dihydro-1H-pyrazole ring (r.m.s. deviation = 0.0849 Å), which approximates to an envelope conformation with the –CH2– group as the flap. The dihedral angle between the benzene rings is 82.86 (7)°. In the crystal, C—H⋯F and C—H⋯O hydrogen bonds link the mol­ecules to form inversion dimers and together these generate chains along [011]. The crystal packing also features C—H⋯π inter­actions.
doi:10.1107/S1600536812034368
PMCID: PMC3435682  PMID: 22969553
12.  1-[5-(4-Bromo­phen­yl)-3-(4-fluoro­phen­yl)-4,5-dihydro-1H-pyrazol-1-yl]ethanone 
In the title mol­ecule, C17H14BrFN2O, the benzene rings form dihedral angles of 6.58 (6) and 85.31 (6)° with the mean plane of the 4,5-dihydro-1H-pyrazole ring (r.m.s. deviation = 0.0231 Å). The latter ring is planar with a maximum deviation of 0.032 (1) Å The dihedral angle between the benzene rings is 78.75 (6)°. In the crystal, weak C—H⋯O and C—H⋯F hydrogen bonds link the mol­ecules into corrugated layers parallel to the ab plane.
doi:10.1107/S1600536812033351
PMCID: PMC3415024  PMID: 22905011
13.  N-(4-Chloro­phen­yl)-2,2-diphenyl­acetamide 
In the title compound, C20H16ClNO, an S(6) ring motif is formed via an intra­molecular C—H⋯O hydrogen bond. The chloro-substituted benzene ring is almost perpendicular to the benzene rings, forming dihedral angles of 87.33 (9) and 88.69 (9)°. The dihedral angle between the benzene rings is 87.17 (9)°. In the crystal, mol­ecules are linked into chains parallel to the c axis by inter­molecular N—H⋯O hydrogen bonds. The crystal packing also features weak C—H⋯π inter­actions involving the chloro-substituted ring.
doi:10.1107/S1600536812032965
PMCID: PMC3414999  PMID: 22904986
14.  1-[2,6-Dichloro-4-(trifluoro­meth­yl)phen­yl]-3,4-dimethyl­pyrano[2,3-c]pyrazol-6(1H)-one 
In the title compound, C15H9Cl2F3N2O2, the 1,6-dihydro­pyrano[2,3-c]pyrazole ring system is almost planar, with a maximum deviation of 0.0226 (14) Å, and forms a dihedral angle of 69.90 (6)° with the benzene ring. In the crystal, mol­ecules are linked into a helical chain along the c axis by C—H⋯O hydrogen bonds.
doi:10.1107/S1600536812029789
PMCID: PMC3414285  PMID: 22904818
15.  N′-[(E)-4-Chloro­benzyl­idene]pyridine-4-carbohydrazide monohydrate 
The asymmetric unit of the title compound, C13H10ClN3O·H2O, consists of two crystallographically independent Schiff base mol­ecules which exist in an E conformation with respect to the C=N double bond, and two independent water mol­ecules. In the crystal, the Schiff base and water mol­ecules are linked into a three-dimensional network via N—H⋯O, O—H⋯N, O—H⋯O and C—H⋯O hydrogen bonds. The crystal studied was a pseudo-merohedral twin with twin law (101 0-10 00-1) and a component ratio of 0.792 (2):0.208 (2).
doi:10.1107/S1600536812029121
PMCID: PMC3394078  PMID: 22798943
16.  (2E)-1-(4,4′′-Difluoro-5′-meth­oxy-1,1′:3′,1′′-terphenyl-4′-yl)-3-(2-fluoro­phen­yl)prop-2-en-1-one 
In the title compound, C28H19F3O2, the central benzene ring forms dihedral angles of 48.69 (6), 60.93 (6) and 42.06 (6)° with the fluoro­benzene rings. In the crystal, inter­molecular C—H⋯O and C—H⋯F hydrogen bonds link the mol­ecules, forming an undulating two-dimensional network parallel to the bc plane. C—H⋯π inter­actions further consolidate the crystal packing.
doi:10.1107/S1600536812024981
PMCID: PMC3393293  PMID: 22807850
17.  (2E)-3-(4-Cyano­phen­yl)-1-(4,4′′-difluoro-5′-meth­oxy-1,1′:3′,1′′-terphenyl-4′-yl)prop-2-en-1-one 
In the title compound, C29H19F2NO2, the central benzene ring forms a dihedral angle of 56.92 (12)° with the cyano­benzene ring and dihedral angles of 40.91 (12) and 44.76 (12)° with the two fluoro­benzene rings. In the crystal, C—H⋯O and C—H⋯F hydrogen bonds link the mol­ecules into sheets lying parallel to the ab plane. The crystal packing also features C—H⋯π inter­actions involving the central benzene ring.
doi:10.1107/S1600536812023124
PMCID: PMC3379440  PMID: 22719638
18.  N-(3-Chloro-4-fluoro­phen­yl)acetamide 
In the title compound, C8H7ClFNO, the dihedral angle between the benzene ring and the acetamide side chain is 5.47 (6)°. An S(6) ring motif is formed via an intra­molecular C—H⋯O hydrogen bond. In the crystal, N—H⋯O hydrogen bonds link the mol­ecules into C(4) chains along [001].
doi:10.1107/S160053681201416X
PMCID: PMC3344482  PMID: 22590244
19.  Diethyl 4-[5-(4-chloro­phen­yl)-1H-pyrazol-4-yl]-2,6-dimethyl-1,4-dihydro­pyridine-3,5-dicarboxyl­ate 
In the title compound, C22H24ClN3O4, intra­molecular C—H⋯O and C—H⋯N hydrogen bonds form S(9) and S(7) ring motifs, respectively. The 1,4-dihydro­pyridine ring adopts a flattened boat conformation. The benzene ring makes a dihedral angle of 33.36 (6)° with the pyrazole ring. In the crystal, pairs of N—H⋯N hydrogen bonds link the mol­ecules into inversion dimers. The dimers are stacked in column along the a axis through N—H⋯O and C—H⋯N hydrogen bonds. The crystal packing also features C—H⋯π inter­actions involving the pyrazole ring.
doi:10.1107/S160053681201344X
PMCID: PMC3344438  PMID: 22590200
20.  2-(8-Bromo­imidazo[1,2-a]pyridin-2-yl)-N′-[(E)-4-diethyl­amino-2-hy­droxy­benzyl­idene]acetohydrazide dihydrate 
In the title compound, C20H22BrN5O2·2H2O, the Schiff base mol­ecule exists in an E conformation with respect to the acyclic C=N bond. An S(6) ring motif is formed via an intra­molecular O—H⋯N hydrogen bond. The dihedral angle between the imidazo[1,2-a]pyridine system and the benzene ring is 84.62 (5)°. In the crystal, N—H⋯O, O—H⋯O, O—H⋯N, C—H⋯O and C—H⋯Br hydrogen bonds link the mol­ecules into a three-dimensional network. The crystal packing is further stabilized by C—H⋯π and π–π inter­actions [centroid–centroid distance = 3.5365 (7) Å].
doi:10.1107/S160053681200685X
PMCID: PMC3297878  PMID: 22412681
21.  2-[(2,4,4,6,6-Penta­chloro-1,3,5,2λ5,4λ5,6λ5-triaza­triphosphinin-2-yl)aza­nid­yl]pyridinium 
The title compound, C5H5Cl5N5P3, crystallizes as a zwitterion in which the pyridine N atom is protonated. An S(6) ring motif is formed via an intra­molecular C—H⋯N hydrogen bond. The triaza­triphosphinine ring adopts an envelope conformation, with one N atom displaced by 0.145 (1) Å from the other atoms. In the crystal, N—H⋯N and C—H⋯N hydrogen bonds link the mol­ecules into centrosymmetric dimers containing one R 2 2(7) ring motif and two R 2 2(8) ring motifs.
doi:10.1107/S160053681200013X
PMCID: PMC3274999  PMID: 22346944
22.  2-(4-Fluoro­phen­yl)-2-oxoethyl 4-meth­oxy­benzoate 
In the title compound, C16H13FO4, the dihedral angle between the benzene rings is 84.28 (8)°. In the crystal, C—H⋯F and C—H⋯O hydrogen bonds link the mol­ecules to form a three-dimensional network. The crystal structure is consolidated by C—H⋯π inter­actions and short F⋯F contacts [2.7748 (14) Å] also occur.
doi:10.1107/S1600536811049233
PMCID: PMC3239086  PMID: 22199934
23.  N′-[(E)-(3-Phenyl-1H-pyrazol-4-yl)methyl­idene]naphtho­[2,1-b]furan-2-carbohydrazide monohydrate 
In the title hydrate, C23H16N4O2·H2O, the pyrazole ring is approximately planar, with a maximum deviation of 0.023 (1) Å, and makes dihedral angles of 28.63 (6) and 46.44 (7)° with the naphtho­[2,1-b]furan ring system and the benzene ring, respectively, In the crystal, O—H⋯N, O—H⋯O, N—H⋯O, N—H⋯N, C—H⋯O and C—H⋯N hydrogen bonds link the mol­ecules, forming sheets lying parallel to the ab plane. The crystal structure also features C—H⋯π inter­actions involving the centroids of the pyrazole and benzene rings.
doi:10.1107/S1600536811050239
PMCID: PMC3239098  PMID: 22199946
24.  2-(4-Chloro­phen­yl)-2-oxoethyl 4-methyl­benzoate 
In the title compound, C16H13ClO3, the dihedral angle between the benzene rings is 80.74 (8)°. In the crystal, C—H⋯O hydrogen bonds link the mol­ecules to form C(11) chains propagating in [010].
doi:10.1107/S1600536811042851
PMCID: PMC3247425  PMID: 22220043
25.  2-(4-Bromo­phen­yl)-2-oxoethyl 4-hy­droxy­benzoate 
In the title compound, C15H11BrO4, the dihedral angle between the aromatic rings is 66.77 (8)°. In the crystal, O—H⋯O, C—H⋯Br and C—H⋯O hydrogen bonds link the mol­ecules, forming layers lying parallel to (101). The crystal packing is further consolidated by C—H⋯π inter­actions and π–π stacking inter­actions [centroid–centroid distance = 3.5476 (7) Å].
doi:10.1107/S1600536811040311
PMCID: PMC3247591  PMID: 22219896

Results 1-25 (86)