Displaying publications 41 - 60 of 77 in total

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  1. Hemamalini M, Fun HK
    Acta Crystallogr Sect E Struct Rep Online, 2010 May 22;66(Pt 6):o1418-9.
    PMID: 21579496 DOI: 10.1107/S1600536810018210
    In the crystal structure of the title salt, C(5)H(6)ClN(2) (+)·C(7)H(5)O(3) (-), the protonated N atom and the 2-amino group of the cation are hydrogen bonded to the carboxyl-ate O atoms via a pair of N-H⋯O hydrogen bonds, forming R(2) (2)(8) ring motifs. These motifs are centrosymmetrically paired via N-H⋯O hydrogen bonds, forming a complementary donor-donor-acceptor-acceptor (DDAA) array. A typical intra-molecular O-H⋯O hydrogen bond is also observed in the salicylate anion. The crystal structure is further stabilized by weak C-H⋯π inter-actions.
  2. Hemamalini M, Fun HK
    Acta Crystallogr Sect E Struct Rep Online, 2010 Feb 06;66(Pt 3):o557.
    PMID: 21580326 DOI: 10.1107/S1600536810004265
    In the title salt, C(5)H(6)ClN(2) (+)·C(7)H(5)O(3) (-), the carboxyl-ate mean plane of the 4-hydroxy-benzoate anion is twisted by 7.16 (9)° from the attached ring. In the crystal structure, the cations and anions are linked via O-H⋯O and N-H⋯O hydrogen bonds, as well as C-H⋯O contacts, forming a three-dimensional network. In addition, weak π-π inter-actions involving the benzene and pyridinium rings, with centroid-to-centroid distances of 3.8941 (9) Å, are observed.
  3. Hemamalini M, Fun HK
    Acta Crystallogr Sect E Struct Rep Online, 2010 Mar 10;66(Pt 4):o783-4.
    PMID: 21580623 DOI: 10.1107/S1600536810008196
    The asymmetric unit of the title salt, C(5)H(6)ClN(2) (+)·C(2)F(3)O(2) (-), contains two independent 2-amino-5-chloro-pyridinium cations and two independent trifluoro-acetate anions. The F atoms of both anions are disordered over two sets of positions, with occupancy ratios of 0.672 (12):0.328 (12) and 0.587 (15):0.413 (15). In the crystal, the cations and anions are linked via N-H⋯O and C-H⋯O hydrogen bonds, forming a two-dimensional network parallel to (001).
  4. Hemamalini M, Fun HK
    Acta Crystallogr Sect E Struct Rep Online, 2010 Jan 30;66(Pt 2):o464-5.
    PMID: 21579876 DOI: 10.1107/S1600536810002990
    In the title salt, C(5)H(6)ClN(2) (+)·C(4)H(5)O(4) (-), the pyridine N atom is protonated. The pyridinium and amino groups associate via a pair of N-H⋯O hydrogen bonds to the carboxyl-ate O atoms of the singly deprotonated succinate anion. The hydrogen succinate anions self-assemble via O-H⋯O hydrogen bonds into chains along the b axis. The crystal structure is further stabilized by additional N-H⋯O hydrogen bonds involving the second amino H atoms, as well as C-H⋯O contacts, forming a three-dimensional network.
  5. Hemamalini M, Fun HK
    Acta Crystallogr Sect E Struct Rep Online, 2010 Aug 28;66(Pt 9):o2457-8.
    PMID: 21588777 DOI: 10.1107/S1600536810033507
    In the title hydrated salt, C(5)H(6)ClN(2) (+)·C(4)H(3)O(4) (-)·0.25H(2)O, the water O atom lies on a twofold axis with 0.25 occupancy. The 2-amino-5-chloro-pyridinium cation is almost planar, with a maximum deviation of 0.015 (3) Å. In the hydrogen malate anion, an intra-molecular O-H⋯O hydrogen bond generates an S(7) ring and results in a folded conformation. In the crystal, the protonated N atom and the 2-amino group of the cation are hydrogen bonded to the carboxyl-ate 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 further connected via O-H⋯O, N-H⋯O and C-H⋯O hydrogen bonds, forming layers parallel to the ab plane which stack down the c axis.
  6. Hemamalini M, Fun HK
    Acta Crystallogr Sect E Struct Rep Online, 2010 Jul 24;66(Pt 8):o2093-4.
    PMID: 21588388 DOI: 10.1107/S1600536810027960
    In the crystal structure of the title compound, C(6)H(9)N(2) (+)·0.5C(4)H(2)O(4) (2-)·0.5C(4)H(6)O(4), the fumarate dianion and fumaric acid mol-ecule are located on inversion centres. The 2-amino-5-methyl-pyrimidinium cation inter-acts with the carboxyl-ate group of the fumarate anion through a pair of N-H⋯O hydrogen bonds, forming an R(2) (2)(8) ring motif. These motifs are centrosymmetrically paired via N-H⋯O hydrogen bonds, forming a complementary DDAA array. The carboxyl groups of the fumaric acid mol-ecules and the carboxyl-ate groups of the fumarate anions are hydrogen bonded through O-H⋯O hydrogen bonds, leading to a supra-molecular chain along [101]. The crystal structure is further stabilized by weak C-H⋯O hydrogen bonds.
  7. Hemamalini M, Fun HK
    Acta Crystallogr Sect E Struct Rep Online, 2010 Aug 21;66(Pt 9):o2369.
    PMID: 21588709 DOI: 10.1107/S1600536810032617
    In the title salt, C(5)H(8)N(3) (+)·C(6)H(7)O(2) (-), the pyridine N atom of the 2,3-diamino-pyridine mol-ecule is protonated. The 2,3-diamino-pyridinium cation is essentially planar, with a maximum deviation of 0.068 (2) Å for one of the amino N atoms. The sorbate anion adopts an extended conformation. In the crystal structure, 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(2) (2)(8) ring motif. The ion pairs are further connected via inter-molecular N-H⋯O and C-H⋯O hydrogen bonds, forming two-dimensional networks parallel to (100).
  8. Hemamalini M, Fun HK
    Acta Crystallogr Sect E Struct Rep Online, 2010 Jul 24;66(Pt 8):o2095-6.
    PMID: 21588389 DOI: 10.1107/S1600536810028539
    In the crystal structure of the title salt, C(6)H(9)N(2) (+)·C(7)H(5)O(6)S(-)·H(2)O, the water mol-ecule acts as an acceptor of bifurcated N-H⋯O hydrogen bonds from the pyridinium H atom and one H atom of the 2-amino group, forming an R(2) (1)(6) ring. The 3-carb-oxy-4-hy-droxy-benzene-sulfonate anions self-assemble via O-H⋯O hydrogen bonds, leading to supra-molecular chains along the a axis. These chains and R(2) (1)(6) motifs are linked via O-H⋯O, N-H⋯O and C-H⋯O hydrogen bonds, forming a layer parallel to the ac plane. There is also an intra-molecular O-H⋯O hydrogen bond in the 3-carb-oxy-4-hy-droxy-benzene-sulfonate anion, generating an S(6) ring motif.
  9. Hemamalini M, Fun HK
    Acta Crystallogr Sect E Struct Rep Online, 2010 Aug 18;66(Pt 9):o2323-4.
    PMID: 21588670 DOI: 10.1107/S1600536810032290
    The asymmetric unit of the title salt, C(5)H(6)ClN(2) (+)·C(7)H(5)O(6)S(-), contains two independent 2-amino-5-chloro-pyridinium cations and two independent 3-carb-oxy-4-hy-droxy-benzene-sulfonate anions. In both anions, the O atoms of the sulfonate group are disordered over two sets of positions, with occupancy ratios of 0.47 (5):0.53 (5) and 0.50 (8):0.50 (8). In each anion, an intra-molecular O-H⋯O hydrogen bond generating an S(6) motif is observed. In the crystal structure, the cations and anions are linked via N-H⋯O, O-H⋯O and C-H⋯O hydrogen bonds, forming a two-dimensional network parallel to (110). The structure is further stabilized by π-π inter-actions between cations and anions [centroid-centroid distance = 3.5454 (12) Å]. The crystal studied was a non-merohedral twin, with a ratio of the twin components of 0.715 (3):0.285 (3).
  10. Hemamalini M, Fun HK
    Acta Crystallogr Sect E Struct Rep Online, 2010 Jul 31;66(Pt 8):o2153-4.
    PMID: 21588438 DOI: 10.1107/S1600536810029636
    The asymmetric unit of the title salt, C(6)H(9)N(2) (+)·C(7)H(5)O(6)S(-), contains two crystallographically independent 2-amino-5-methylpyridinium cations and two sulfosalicylate anions. In the crystal structure, the sulfonate group of each 3-carb-oxy-4-hy-droxy-benzene-sulfonate anion inter-acts with the corresponding 2-amino-5-methyl-pyridinium cation via a pair of N-H⋯O hydrogen bonds, forming an R(2) (2)(8) ring motif. The ionic units are linked by N-H⋯O, O-H⋯O and C-H⋯O hydrogen bonds. Furthermore, the crystal structure is stabilized by π-π inter-actions between the benzene and pyridine rings [centroid-centroid distances = 3.5579 (8) and 3.8309 (8) Å]. There are also intra-molecular O-H⋯O hydrogen bonds in the anions, which generate S(6) ring motifs.
  11. Hemamalini M, Fun HK
    Acta Crystallogr Sect E Struct Rep Online, 2010 Mar 10;66(Pt 4):o781-2.
    PMID: 21580622 DOI: 10.1107/S1600536810008202
    The asymmetric unit of the title compound, C(6)H(9)N(2) (+)·C(2)F(3)O(2) (-), contains two independent 2-amino-4-methyl-pyridinium cations and two independent trifluoro-acetate anions. The F atoms of both anions are disordered over two sets of sites, with site occupancies of 0.50 (3) and 0.50 (3) in one of the anions, and 0.756 (9) and 0.244 (9) in the other. In the crystal, the cations and anions are linked into chains along the b axis by N-H⋯O hydrogen bonds and these chains are cross-linked by C-H⋯O hydrogen bonds, forming a two-dimensional network lying parallel to (101). The crystal structure is further stabilized by π-π inter-actions between the pyridinium rings [centroid-centroid distances = 3.5842 (13) and 3.5665 (16) Å].
  12. Hemamalini M, Goh JH, Fun HK
    PMID: 22347022 DOI: 10.1107/S1600536811055838
    The complete anion of the title hydrated mol-ecular salt, 2C(5)H(8)N(3) (+)·C(8)H(4)O(4) (-)·2H(2)O, is generated by a crystallographic twofold axis. In the crystal, the cations, anions and water mol-ecules 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 inter-actions.
  13. Hemamalini M, Goh JH, Fun HK
    Acta Crystallogr Sect E Struct Rep Online, 2011 Dec 1;67(Pt 12):o3498.
    PMID: 22199970 DOI: 10.1107/S1600536811050422
    The asymmetric unit of the title compound, C(5)H(8)N(3) (+)·C(7)H(4)ClO(2) (-)·C(7)H(5)ClO(2), contains an ion pair and a 3-chloro-benzoic acid mol-ecule. 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).
  14. Hemamalini M, Razak IA, Fun HK
    Acta Crystallogr Sect E Struct Rep Online, 2011 Oct 1;67(Pt 10):o2655.
    PMID: 22065809 DOI: 10.1107/S1600536811036774
    In the 4-nitro-benzene sulfonate anion of the title compound, C(2)H(4)N(3) (+)·C(6)H(4)NO(5)S(-)·H(2)O, the nitro group is slightly twisted from the plane of the benzene ring [dihedral angle = 2.8 (3)°]. In the crystal, the three components are linked via N-H⋯O, O-H⋯N, O-H⋯O and C-H⋯O hydrogen bonds, forming a two-dimensional network parallel to the bc plane. A short inter-molecular O⋯N contact of 2.872 (3) Å is also observed between the nitro and sulfonate groups.
  15. Hemamalini M, Goh JH, Fun HK
    PMID: 22259470 DOI: 10.1107/S1600536811053025
    In the title mol-ecular salt-adduct, C(5)H(8)N(3) (+)·C(6)H(7)O(2) (-)·C(6)H(8)O(2), the 2,3-diamino-pyridinium 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 mol-ecules 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 mol-ecules and the carboxyl-ate groups of the sorbate anions are connected via O-H⋯O hydrogen bonds. Furthermore, the ion pairs and neutral mol-ecules are connected via inter-molecular N-H⋯O hydrogen bonds, forming sheets lying parallel to (100).
  16. Hemamalini M, Goh JH, Fun HK
    PMID: 22220123 DOI: 10.1107/S1600536811044461
    In the title mol-ecular salt, C(5)H(8)N(3) (+)·C(7)H(5)O(3) (-), the 2,3-diamino-pyridinium cation is essentially planar, with a maximum deviation of 0.006 (2) Å. In the crystal, adjacent cations and anions are linked by pairs of N-H⋯O hydrogen bonds, generating R(2) (2)(8) loops. These dimers are linked by further N-H⋯O hydrogen bonds and C-H⋯O inter-actions to form sheets lying parallel to (001). A typical intra-molecular O-H⋯O hydrogen bond is also observed in the salicylate (2-hy-droxy-benzoate) anion, which generates an S(6) ring. The crystal structure also features π-π stacking inter-actions between the pyridinium rings of the cations, with a centroid-centroid distance of 3.5896 (15) Å.
  17. Hemamalini M, Goh JH, Fun HK
    PMID: 22220125 DOI: 10.1107/S1600536811044473
    In the title mol-ecular salt, C(5)H(8)N(3) (+)·C(5)H(7)O(4) (-), the 2,3-diamino-pyridine mol-ecule is protonated at the pyridine N atom. The cation is essentially planar, with a maximum deviation of 0.015 (2) Å, and the anion adopts an extended conformation. In the crystal, the hydrogen glutarate (4-carb-oxy-butano-ate) anions are self-assembled through O-H⋯O hydrogen bonds, forming chains. The cations are connected to the anion chains via N-H⋯O hydrogen bonds, forming a three-dimensional network. The crystal structure also features aromatic π-π inter-actions between the pyridinium cations, with a centroid-centroid distance of 3.4464 (10) Å.
  18. Hemamalini M, Goh JH, Fun HK
    PMID: 22220124 DOI: 10.1107/S160053681104445X
    In the title hydrated mol-ecular salt, C(5)H(8)N(3) (+)·C(7)H(5)O(6)S(-)·H(2)O, the ion pairs and water mol-ecules are connected by N-H⋯O, O-H⋯O and C-H⋯O hydrogen bonds, thereby forming a three-dimensional network. There is an intra-molecular O-H⋯O hydrogen bond in the 3-carb-oxy-4-hy-droxy-benzene-sulfonate anion, which generates an S(6) ring motif.
  19. Hemamalini M, Razak IA, Fun HK
    Acta Crystallogr Sect E Struct Rep Online, 2011 Sep 1;67(Pt 9):o2402.
    PMID: 22058994 DOI: 10.1107/S1600536811033174
    In the title mol-ecular salt, C(6)H(9)N(2) (+)·C(8)H(5)O(4) (-), an intra-molecular O-H⋯O hydrogen bond occurs within the anion, thereby generating an S(7) ring, which may correlate with the fact that both the carb-oxy-lic acid and carboxyl-ate groups are almost coplanar with their attached rings [dihedral angles = 2.9 (3) and 5.2 (3)°, respectively]. In the crystal, each cation is linked to its adjacent anion by two N-H⋯O hydrogen bonds; the dihedral angle between the pyridine and benzene rings is 2.22 (10)°. The ion pairs are linked by further N-H⋯O inter-actions.
  20. Quah CK, Hemamalini M, Fun HK
    PMID: 21588263 DOI: 10.1107/S1600536810025924
    The title 1:1 adduct, C(5)H(5)BrN(2)·C(7)H(6)O(3), contains two mol-ecules of each species in the asymmetric unit, with similar geometries. In the crystal, mol-ecules are linked to form extended chains along [100] by N-H⋯O, O-H⋯O, O-H⋯N and C-H⋯O hydrogen bonds. Adjacent chains are crosslinked via further N-H⋯O inter-actions into sheets lying parallel to (001). The crystal studied was an inversion twin with a 0.54 (2):0.46 (2) domain ratio.
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