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1.  6-(Hex-5-en­yloxy)naphthalene-2-carb­oxy­lic acid 
The asymmetric unit of the title compound, C17H18O3, comprises three independent mol­ecules with similar geometries. In each mol­ecule, the carbonyl group is twisted away from the napthalene ring system, making dihedral angles of 1.0 (2), 1.05 (19)° and 1.5 (2)°. The butene group in all three mol­ecules are disordered over two sets of sites, with a refined occupancy ratio of 0.664 (6):0.336 (6). In the crystal, mol­ecules are oriented with respect to their carbonyl groups, forming head-to-head dimers via O—H⋯O hydrogen bonds. Adjacent dimers are further inter­connected by C—H⋯O hydrogen bonds into chains along the a-axis direction. The crystal structure is further stabilized by weak C—H⋯π inter­actions.
doi:10.1107/S1600536814010642
PMCID: PMC4051067  PMID: 24940271
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
, 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
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
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
4.  6-Cyanona­phthalen-2-yl 4-hexyl­benzo­ate 
In the title compound, C24H23NO2, a whole mol­ecule is disordered over two sets of sites with occupancies in a ratio of 0.692 (6):0.308 (6). In the major disorder component, the naphthalene ring system forms a dihedral angle of 68.6 (5)° with the benzene ring. The corresponding angle in the minor component is 81.6 (10)°. In the crystal, mol­ecules are linked into chains propagating along the b-axis direction via weak C—H⋯O hydrogen bonds. The crystal packing is further consolidated by weak C—H⋯π inter­actions.
doi:10.1107/S160053681400909X
PMCID: PMC4011248  PMID: 24860410
5.  Trichodermaerin: a diterpene lactone from Trichoderma asperellum  
The title compound, C20H28O3, known as ‘trichodermaerin’ [systematic name: (4E)-4,9,15,16,16-penta­methyl-6-oxa­tetra­cyclo­[10.3.1.01,10.05,9]hexa­dec-4-ene-7,13-dione], is a diterpene lactone which was isolated from Trichoderma asperellum. The structure has a tetra­cycic 6–5–7–5 ring system, with the cyclo­hexa­none ring adopting a twisted half-chair conformation and the cyclo­pentane ring adopting a half-chair conformation, whereas the cyclo­heptene and tetra­hydro­furan­anone rings are in chair and envelope (with the methyl-substituted C atom as the flap) conformations, respectively. The three-dimensional architecture is stabilized by C—H⋯O inter­actions.
doi:10.1107/S1600536814004632
PMCID: PMC3998585  PMID: 24826124
6.  (E)-2-[4-(Di­ethyl­amino)­styr­yl]-1-methyl­quinolin-1-ium 4-chloro­benzene­sulfonate monohydrate 
The asymmetric unit of the title hydrated salt, C22H25N2 +·C6H4ClO3S−·H2O, comprises two 2-[4-(di­ethyl­amino)­styr­yl]-1-methyl­quinolin-1-ium cations, two 4-chloro­benzene­sul­fon­ate anions and two solvent water mol­ecules. One ethyl group of both cations displays disorder over two positions in a 0.659 (2):0.341 (2) ratio in one mol­ecule and in a 0.501 (2):0.499 (2) ratio in the other. The sulfonate group of one anion is also disordered over two positions in a 0.893 (7):0.107 (7) ratio. The dihedral angle between the mean plane of the quinolinium ring system and that of benzene ring is 10.57 (18)° in one cation and 14.4 (2)° in the other. In the crystal, cations, anions and water mol­ecules are linked into chains along the [010] direction by O—H⋯Osulfonate hydrogen bonds, together with weak C—H⋯Osulfonate and C—H⋯Cl inter­actions. The cations are stacked by π–π inter­actions, with centroid–centroid distances in the range 3.675 (2)–4.162 (3) Å.
doi:10.1107/S1600536814004577
PMCID: PMC3998564  PMID: 24826116
7.  (E)-4-Meth­oxy-N′-(2,4,5-tri­meth­oxy­benzyl­idene)benzohydrazide hemihydrate 
The title compound crystallizes as a hemihydrate, C18H20N2O5·0.5H2O. The mol­ecule exists in an E conformation with respect to the C=N imine bond. The 4-meth­oxy­phenyl unit is disordered over two sets of sites with a refined occupancy ratio of 0.54 (2):0.46 (2). The dihedral angles between the benzene rings are 29.20 (9) and 26.59 (9)°, respectively, for the major and minor components of the 4-meth­oxy-substituted ring. All meth­oxy substituents lie close to the plane of the attached benzene rings [the Cmeth­yl—O—C—C torsion angles range from −4.0 (12) to 3.9 (2)°]. In the crystal, the components are linked into chains propagating along [001] via N—H⋯O and O—H⋯O hydrogen bonds and weak C—H⋯O inter­actions.
doi:10.1107/S1600536814000531
PMCID: PMC3998312  PMID: 24764873
8.  (E)-2-[(2,4,6-Tri­meth­oxy­benzyl­idene)amino]­phenol1  
There are two independent mol­ecules in the asymmetric unit of the title compound, C16H17NO4, with similar conformations but some differences in their bond angles. Each mol­ecule adopts a trans configuration with respect to the methyl­idene C=N bond and is twisted with a dihedral angle between the two substituted benzene rings of 80.52 (7)° in one mol­ecule and 83.53 (7)° in the other. All meth­oxy groups are approximately coplanar with the attached benzene rings, with Cmeth­yl—O—C—C torsion angles ranging from −6.7 (2) to 5.07 (19)°. In the crystal, independent mol­ecules are linked together by O—H⋯N and O—H⋯O hydrogen bonds and a π–π inter­action [centroid–centroid distance of 3.6030 (9) Å], forming a dimer. The dimers are further linked by weak C—H⋯O inter­actions and another π–π inter­action [centroid–centroid distance of 3.9452 (9) Å] into layers lying parallel to the ab plane.
doi:10.1107/S1600536813032996
PMCID: PMC3914096  PMID: 24527001
9.  2-[(E)-2-(4-Eth­oxy­phen­yl)ethen­yl]-1-methyl­quinolinium 4-fluoro­benzene­sulfonate 
In the structure of the title salt, C20H20NO+·C6H4FO3S−, the 4-(eth­oxy­phen­yl)ethenyl unit is disordered over two positions with a refined site-occupancy ratio of 0.610 (6):0.390 (6). The cation is nearly planar, the dihedral angle between the quinolinium and benzene rings being 6.7 (4) and 1.7 (7)° for the major and minor components, respectively. The eth­oxy group is essentially coplanar with the benzene ring [C—O—C—Cmethy = 177.1 (8) and 177.8 (12)° for the major and minor components, respectively]. In the crystal, cations and anions are linked into chains along the b-axis direction by C—H⋯Osulfon­yl weak inter­actions. These chains are further connected into sheets parallel to (001) by C—H⋯Osulfon­yl weak inter­actions. The chains are also stacked along the a axis through π–π inter­actions involving the quinolinium and benzene rings [centroid–centroid distances = 3.636 (5) Å for the major component and 3.800 (9) Å for the minor component]. C—H⋯π inter­actions are also present.
doi:10.1107/S1600536813032509
PMCID: PMC3914062  PMID: 24526963
10.  6-(4-Amino­phen­yl)-2-meth­oxy-4-phenyl­nicotino­nitrile 
In the structure of the title nicotino­nitrile derivative, C19H15N3O, the pyridine ring makes dihedral angles of 11.50 (7) and 43.36 (8)° with the 4-amino­phenyl and phenyl rings, respectively, and the dihedral angle between the phenyl rings is 36.28°. In the crystal, mol­ecules are linked by N—H⋯N hydrogen bonds into wave-like sheets parallel to (10-2). These sheets are stacked by π–π inter­actions between the 4-amino­phenyl rings of adjacent sheets, with centroid–centroid distances of 3.7499 (9) Å. C—H⋯π inter­actions are also present.
doi:10.1107/S1600536813031437
PMCID: PMC3885069  PMID: 24454245
11.  Bis{4-[(E)-2-(1H-indol-3-yl)ethen­yl]-1-methyl­pyridinium} 4-chloro­benzene­sulfonate nitrate 
In the title mixed salt, 2C16H15N2 +·C6H4ClO3S−·NO3 −, one of the cations shows whole mol­ecule disorder over two sets of sites in a 0.711 (7):0.289 (7) ratio. The 4-chorobenzenesulfon­ate anion is also disordered over two orientations in a 0.503 (6):0.497 (6) ratio. The cations are close to planar, the dihedral angles between the pyridinium and indole rings being 1.48 (3)° in the ordered cation, and 5.62 (3) and 2.45 (3)°, respectively, for the major and minor components of the disordered cation. In the crystal, the cations are stacked in an anti­parallel manner approximately along the a-axis direction and linked with the anions via N—H⋯O hydrogen bonds and C—H⋯O inter­actions, generating a three-dimensional network. Weak C—H⋯π and π–π inter­actions [with centroid–centroid distances of 3.561 (2)–3.969 (7) Å] are also observed.
doi:10.1107/S1600536813030080
PMCID: PMC3885032  PMID: 24454207
12.  6-Meth­oxy-4-(2,4,5-tri­meth­oxy­phen­yl)-2,2′-bi­pyridine-5-carbo­nitrile 
In the title 3-cyano­pyridine derivative, C21H19N3O4, the 3-cyano-substituted pyridine ring forms dihedral angles of 2.35 (5) and 41.60 (5)° with the unsubstituted pyridine and 2,4,5-trimeth­oxy-substituted benzene rings, respectively. The dihedral angle between the unsubstituted pyridine and benzene rings is 39.84 (5)°. The meth­oxy groups form Cmeth­yl—O—C—(C,N) torsion angles in the range 0.80 (15)–11.45 (15)°. In the crystal, mol­ecules related by 21 screw axes are linked by weak C—H⋯N hydrogen bonds along [010]. In addition, weak C—H⋯π inter­actions and π–π stacking inter­actions between pyridine rings, with a centroid–centroid distance of 3.6448 (6) Å, are observed.
doi:10.1107/S1600536813023891
PMCID: PMC3790375  PMID: 24098197
13.  Ethyl 2-[(2-oxo-2H-chromen-7-yl)­oxy]acetate 
In the title compound, C13H12O5, the mean plane of the 2H-chromene ring system (r.m.s deviation = 0.026 Å) forms a dihedral angle of 81.71 (6)° with the mean plane of ethyl 2-hy­droxy­acetate moiety (r.m.s deviation = 0.034 Å). In the crystal, C—H⋯O hydrogen bonds result in the formation of zigzag layers parallel to the bc plane.
doi:10.1107/S1600536813005539
PMCID: PMC3629532  PMID: 23634050
14.  7-Hy­droxy­methyl-2-pivaloyl­amino-1,8-naphthyridine 
In the title compound, C14H17N3O2, the mean plane of the 1,8-naphthyridine ring system (r.m.s deviation = 0.020 Å) forms a dihedral angle of 23.4 (1)° with the acetamide moiety (r.m.s deviation = 0.001 Å). The mol­ecular structure is stabilized by an intra­molecular O—H⋯N hydrogen bond, which generates an S(5) ring motif. In the crystal, mol­ecules are linked into inversion dimers by pairs of N—H⋯O hydrogen bonds, generating 18-membered R 2 2(18) ring motifs.
doi:10.1107/S1600536813005527
PMCID: PMC3629533  PMID: 23634051
15.  3-(4-Chloro­phen­yl)-5-(4-eth­oxy­phen­yl)-4,5-dihydro-1H-pyrazole-1-carbothio­amide ethanol monosolvate 
The asymmetric unit of the title compound, C18H18ClN3OS·C2H5OH, comprises a pyrazoline derivative and an ethanol solvent mol­ecule. In the mol­ecule of the pyrazoline derivative, the pyrazole ring adopts an envelope conformation with the C atom bearing the eth­oxy­phenyl substituent as the flap. The dihedral angle between the benzene rings is 74.22 (7)°. The eth­oxy group is coplanar with the attached benzene ring [C—O—C—Cmeth­yl = 175.50 (11)° and r.m.s. deviation = 0.0459 (1) Å for the nine non-H atoms]. In the crystal, the pyrazoline mol­ecules are linked by N—H⋯Oeth­oxy hydrogen bonds into chains along the c axis and are further linked with the solvent ethanol mol­ecules by N—H⋯Oethanol and Oethanol—H⋯S hydrogen bonds. C—H⋯π inter­actions are also present.
doi:10.1107/S1600536813005369
PMCID: PMC3629506  PMID: 23634024
16.  (E)-2-[4-(Diethyl­amino)­styr­yl]-1-ethyl­pyridinium iodide monohydrate 
In the title hydrated salt, C19H25N2 +·I−·H2O, the 4-(diethyl­amino)­phenyl unit of the cation is disordered over two positions in a 0.847 (3):0.153 (3) ratio. The cation is twisted, with dihedral angles between the pyridinium and benzene rings of 11.25 (13) and 10.7 (8)° for the major and minor components, respectively. In the crystal, the three components are linked into a centrosymmetric 2:2:2 unit by O—H⋯I and C—H⋯O hydrogen bonds. π–π inter­actions with centroid–centroid distances of 3.5065 (7)–3.790 (9) Å are also present.
doi:10.1107/S160053681300528X
PMCID: PMC3588554  PMID: 23476625
17.  (Z)-2-Benzyl­idenebenzo[d]thia­zolo[3,2-a]imidazol-3(2H)-one 
The mol­ecule of the title compound, C16H10N2OS, is approximately planar, the dihedral angle between the 1,3-benzothia­zolo[3,2-a]imidazol-3(2H)-one and the benzyl­idene moieties being 4.10 (8)°. A weak intra­molecular C—H⋯S inter­action generates an S(6) ring. No inter­molecular hydrogen bonds are observed in the crystal structure.
doi:10.1107/S1600536812035003
PMCID: PMC3435723  PMID: 22969594
18.  (2E)-3-[4-(Benz­yloxy)phen­yl]-1-(pyridin-3-yl)prop-2-en-1-one 
The title compound, C21H17NO2, exists in an E conformation with respect to the C=C bond. The pyridine ring forms dihedral angles of 5.57 (7) and 82.30 (9)°, respectively, with the central benzene ring and the terminal phenyl ring. The dihedral angle between the benzene and phenyl rings is 87.69 (8)°. No significant inter­molecular inter­actions are observed.
doi:10.1107/S1600536812034897
PMCID: PMC3435737  PMID: 22969608
19.  1-(1,5-Diphenyl-4-phenyl­sulfonyl-1H-pyrazol-3-yl)ethanone 
The asymmetric unit of the title compound, C23H18N2O3S, contains two mol­ecules with comparable geometries. In one mol­ecule, the pyrazole ring forms dihedral angles of 61.65 (11), 47.88 (11) and 63.20 (14)° with the three benzene rings. The corresponding values for the other mol­ecule are 77.19 (11), 43.55 (11) and 63.56 (15)°. In the crystal, both mol­ecules are linked into inversion dimers by pairs of C—H⋯S hydrogen bonds, generating R 2 2(14) loops in each case.
doi:10.1107/S1600536812035027
PMCID: PMC3435738  PMID: 22969609
20.  3-Oxo-3-(piperidin-1-yl)propane­nitrile 
In the title compound, C8H12N2O, the piperidine ring exhibits a chair conformation and its least-squares plane (all atoms) makes a dihedral angle of 32.88 (12)° with the propane­nitrile unit (r.m.s. deviation = 0.001 Å). In the crystal, mol­ecules are linked by C—H⋯O hydrogen bonds, forming chains along [001].
doi:10.1107/S1600536812035015
PMCID: PMC3435739  PMID: 22969610
21.  (Z)-2-(5-Acetyl-4-methyl-3-phenyl-2,3-dihydro-1,3-thia­zol-2-yl­idene)-3-(3-methyl-1-benzofuran-2-yl)-3-oxo­propane­nitrile 
In the title compound, C24H18N2O3S, the benzofuran ring system (r.m.s. deviation = 0.010 Å) forms dihedral angles of 83.13 (17) and 8.92 (14)° with the benzene and thia­zole rings, respectively. The dihedral angle between the benzene and thia­zole rings is 84.51 (19)°. The mol­ecular structure features an intra­molecular C—H⋯O hydrogen bond, which closes an S(6) ring. There are no inter­molecular hydrogen bonds observed in this structure.
doi:10.1107/S1600536812035039
PMCID: PMC3435740  PMID: 22969611
22.  N-(1,5-Dimethyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazol-4-yl)-2-[4-(methyl­sulfan­yl)phen­yl]acetamide 
In the title compound, C20H21N3O2S, the 2,3-dihydro-1H-pyrazole ring is nearly planar (r.m.s. deviation = 0.023 Å) and forms dihedral angles of 16.96 (6) and 38.93 (6)° with the benzene and phenyl rings, respectively. The dihedral angle between the benzene and phenyl rings is 55.54 (6)°. The mol­ecular conformation is consolidated by an intra­molecular C—H⋯O hydrogen bond, which forms an S(6) ring. In the crystal, inversion dimers linked by pairs of N—H⋯Op (p = pyrazole) hydrogen bonds generate R 2 2(10) loops. The dimers are linked by C—H⋯O hydrogen bonds into sheets lying parallel to (100).
doi:10.1107/S1600536812034605
PMCID: PMC3435699  PMID: 22969570
23.  2-(4-Bromo­phen­yl)-N-(2,6-dimethyl­phen­yl)acetamide 
In the title compound, C16H16BrNO, the dihedral angle between the benzene rings is 69.8 (2)°. In the crystal, N—H⋯O hydrogen bonds link the mol­ecules into C(4) chains propagating in [100]. Adjacent mol­ecules in the chains are also linked by C—H⋯O inter­actions which, along with the N—H⋯O hydrogen bonds, generate R 2 1(6) loops.
doi:10.1107/S1600536812034617
PMCID: PMC3435700  PMID: 22969571
24.  2-(4-Chloro­phen­yl)-N-(1,3-thia­zol-2-yl)acetamide 
In the title compound, C11H9ClN2OS, the thia­zole ring is nearly planar (r.m.s. deviation = 0.003 Å) and forms a dihedral angle of 64.18 (7)° with the bezene ring. In the crystal, inversion dimers linked by pairs of N—H⋯Nt (t = thia­zole) hydrogen bonds generate R 2 2(8) loops.
doi:10.1107/S1600536812034629
PMCID: PMC3435701  PMID: 22969572
25.  1-(6-Chloro-1,3-benzothia­zol-2-yl)-2-[1-(4-meth­oxy­phen­yl)ethyl­idene]hydrazine 
The asymmetric unit of the title compound, C16H14ClN3OS, contains two independent mol­ecules (A and B) linked into dimers via N—H⋯N hydrogen bonds. The 1,3-benzothia­zol-2-yl ring system and the benzene ring form dihedral angles of 17.08 (8) and 8.63 (7)° in mol­ecules A and B, respectively.
doi:10.1107/S1600536812032606
PMCID: PMC3435704  PMID: 22969575

Results 1-25 (79)