Displaying publications 1 - 20 of 136 in total

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  1. Seng HL, Ong HK, Rahman RN, Yamin BM, Tiekink ER, Tan KW, et al.
    J Inorg Biochem, 2008 Nov;102(11):1997-2011.
    PMID: 18778856 DOI: 10.1016/j.jinorgbio.2008.07.015
    The binding selectivity of the M(phen)(edda) (M=Cu, Co, Ni, Zn; phen=1,10-phenanthroline, edda=ethylenediaminediacetic acid) complexes towards ds(CG)(6), ds(AT)(6) and ds(CGCGAATTCGCG) B-form oligonucleotide duplexes were studied by CD spectroscopy and molecular modeling. The binding mode is intercalation and there is selectivity towards AT-sequence and stacking preference for A/A parallel or diagonal adjacent base steps in their intercalation. The nucleolytic properties of these complexes were investigated and the factors affecting the extent of cleavage were determined to be: concentration of complex, the nature of metal(II) ion, type of buffer, pH of buffer, incubation time, incubation temperature, and the presence of hydrogen peroxide or ascorbic acid as exogenous reagents. The fluorescence property of these complexes and its origin were also investigated. The crystal structure of the Zn(phen)(edda) complex is reported in which the zinc atom displays a distorted trans-N(4)O(2) octahedral geometry; the crystal packing features double layers of complex molecules held together by extensive hydrogen bonding that inter-digitate with adjacent double layers via pi...pi interactions between 1,10-phenanthroline residues. The structure is compared with that of the recently described copper(II) analogue and, with the latter, included in molecular modeling.
  2. Tiekink ER
    PMID: 21578544 DOI: 10.1107/S1600536809047096
    The title supra-molecular polymer, [Cu(S(3)O(6))(H(2)O)(4)](n), features a tetra-gonally distorted octa-hedral Cu(II) centre within an O(6) donor set with the longer Cu-O bonds linking the dication and the trithio-nate dianion. Extensive O-H⋯O hydrogen-bonding inter-actions connect the supra-molecular chains into a three-dimensional network.
  3. Ozair LN, Abdullah N, Khaledi H, Tiekink ER
    Acta Crystallogr Sect E Struct Rep Online, 2010 Apr 30;66(Pt 5):m589-90.
    PMID: 21579064 DOI: 10.1107/S1600536810015060
    The structure of the dinuclear title complex, [Cu(2)(C(5)H(9)O(2))(4)(C(5)H(5)N)(2)], represents a monoclinic polymorph of the previously reported triclinic form [Blewett et al. (2006 ▶). Acta Cryst. E62, m420-m422]. Each carboxyl-ate group is bidentate bridging and the distorted octa-hedral geometry about each Cu(II) atom is completed by a pyridine N atom and the other Cu atom [Cu⋯Cu = 2.6139 (7) Å]. In the crystal, mol-ecules are connected into supra-molecular chains via π-π inter-actions formed by the pyridine rings [centroid-centroid distance = 3.552 (3) Å] and these are connected into a two-dimensional array in the ac plane by C-H⋯π contacts. One of the tert-butyl groups is disordered over two orientations in a 0.734 (6):0.266 (6) ratio.
  4. Aznan Akhmad MA, Abdullah Z, Fairuz ZA, Ng SW, Tiekink ER
    PMID: 21588732 DOI: 10.1107/S1600536810033040
    Two independent mol-ecules comprise the asymmetric unit of the title compound, C(12)H(11)N(3)O(2). These differ in terms of the relative orientations of the benzene rings as seen in the respective dihedral angles formed between the pyridine and benzene rings [17.42 (16) and 34.64 (16)°]. Both mol-ecules are twisted about the amine-tolyl N-C bonds [respective torsion angles = 22.3 (5) and 35.9 (5)°] but only about the amine-pyridine N-C bond in the first independent mol-ecule [respective torsion angles = -11.7 (5) and 0.8 (5)°]. Intra-molecular N-H⋯O hydrogen bonds preclude the amine H atoms from forming significant inter-molecular inter-actions. The crystal packing features inter-molecular C-H⋯O and C-H⋯π and π-π [centroid-centroid distance: pyridine-benzene = 3.6442 (19) Å and pyridine-pyridine = 3.722 (2) Å] contacts.
  5. Badaruddin E, Aiyub Z, Abdullah Z, Ng SW, Tiekink ER
    PMID: 21588767 DOI: 10.1107/S1600536810033301
    Two independent mol-ecules comprise the asymmetric unit in the title compound, C(11)H(11)N(3). These differ in terms of the relative orientations of the aromatic rings: the first is somewhat twisted, while the second is approximately planar [dihedral angles between the pyrimidine and phenyl rings = 39.00 (8) and 4.59 (11)°]. The mol-ecules also form distinct patterns in their hydrogen bonding. The first independent mol-ecule forms centrosymmetric dimers featuring an eight-membered {HNCN}(2) synthon. The second independent mol-ecule forms an N-H⋯N hydrogen bond with the other pyrimidine N atom of the first mol-ecule. Thereby, tetra-meric aggregates are formed. These associate via C-H⋯N and C-H⋯π inter-actions, consolidating the crystal packing.
  6. Hassan ND, Abdullah Z, Tajuddin HA, Fairuz ZA, Ng SW, Tiekink ER
    PMID: 21588753 DOI: 10.1107/S1600536810034100
    In the title mol-ecule, C(14)H(9)N(3)O(3), the dihedral angle between the quinoxaline and benzene rings is 77.13 (9)°. The mol-ecule is twisted about the ether-benzene O-C bond, with a C-O-C-C torsion angle of -102.8 (2)°. In the crystal, mol-ecules are linked by C-H⋯O hydrogen bonds, forming layers in the ab plane, with one nitro O atom accepting two such inter-actions. The layers stack along the c-axis direction via weak C-H⋯π inter-actions.
  7. Nasir SB, Abdullah Z, Fairuz ZA, Ng SW, Tiekink ER
    PMID: 21588752 DOI: 10.1107/S1600536810034057
    In the title mol-ecule, C(12)H(10)N(2)O(4), the pyridine and benzene rings are almost orthogonal [dihedral angle = 86.69 (11)°], with the pyridine N atom directed towards the centre of the benzene ring. The -NO(2) [O-N-C-C = -26.1 (3)°] and -OMe [C-O-C-C = 166.5 (2)°] substituents are not coplanar with their respective aromatic rings. In the crystal, supra-molecular layers in the ab plane are formed via C-H⋯π inter-actions involving methyl H atoms and the pyridine and benzene rings. Short N-O⋯π contacts (where the π-system is derived from the pyridine ring) occur between layers in the c-axis direction.
  8. Idris A, Abdullah Z, Ariffin A, Fairuz ZA, Ng SW, Tiekink ER
    PMID: 21588631 DOI: 10.1107/S1600536810031260
    The quinoxaline system in the title hydrate, C(15)H(13)N(3)·H(2)O, is roughly planar, the r.m.s. deviation for the 18 non-H atoms being 0.188 Å; this conformation features a short intra-molecular C-H⋯N(pyrazine) inter-action. In the crystal, the amine H atom forms an N-H⋯O hydrogen bond to the water mol-ecule, which in turn forms two O-H⋯N hydrogen bonds to the pyrazine N atoms of different organic mol-ecules. These inter-actions lead to supra-molecular arrays in the bc plane that are two mol-ecules thick; additional π-π inter-actions stabilize the layers [ring centroid-centroid distance = 3.5923 (7) Å]. The layers stack along the a-axis direction via C-H⋯π contacts.
  9. Aiyub Z, Badaruddin E, Abdullah Z, Fairuz ZA, Ng SW, Tiekink ER
    PMID: 21588567 DOI: 10.1107/S1600536810034033
    In the centrosymmetric title mol-ecule, [Cu(2)(CH(3)COO)(4)(C(6)H(9)N(3))(2)], each of the four acetate groups bridges a pair of Cu(II) atoms [Cu-Cu = 2.6540 (4) Å]. The distorted octa-hedral geometry of the metal atom is completed by an N-donor atom of the N-ethyl-pyrimidin-2-amine ligand: an intra-molecular N-H⋯O hydrogen links its N-H group to an acetate carboxyl-ate O atom. In the crystal, C-H⋯O inter-actions link the mol-ecules into a supra-molecular chain along the b axis.
  10. Nasir SB, Abdullah Z, Mainal A, Fairuz ZA, Ng SW, Tiekink ER
    PMID: 21588653 DOI: 10.1107/S1600536810031946
    In the title compound, C(11)H(10)N(2)O(2), the aromatic rings are almost orthogonal to each other [dihedral angle = 86.97 (8)°], with the benzene ring orientated to face one of the pyrazine N atoms. In the crystal, centrosymmetrically related pairs are connected via pairs of C-H⋯π inter-actions and the dimeric units thus formed pack into undulating layers that stack along the a axis.
  11. Nasir SB, Abdullah Z, Fairuz ZA, Ng SW, Tiekink ER
    PMID: 21588583 DOI: 10.1107/S1600536810030448
    The pyrimidine and benzene rings in the title compound, C(10)H(8)N(2)O(2), form a dihedral angle of 71.03 (7)°, with the roughly orthogonal benzene ring being folded towards one of the pyrimidine N atoms. In the crystal, pairs of O-H⋯N hydrogen bonds connect mol-ecules related by twofold symmetry into dimeric aggregates. These associate into a supra-molecular chain propagating along the b axis by way of C-H⋯π contacts. The chains are cross-linked by π-π inter-actions that occur between pyrimidine rings [ring centroid-centroid distances = 3.5393 (9) and 3.5697 (9) Å].
  12. Ketuly KA, Hadi AH, Ng SW, Tiekink ER
    PMID: 21588624 DOI: 10.1107/S160053681003117X
    In the title cholestane derivative, C(28)H(48) [systematic name: (1S,2S,7R,10R,11R,14R,15R)-2,5,10,15-tetra-methyl-14-[(2R)-6-methyl-heptan-2-yl]tetra-cyclo-[8.7.0.0(2,7).0(11,15)]hepta-dec-4-ene], the cyclo-hexene ring adopts a half-chair conformation. The parent 5α-cholest-2-ene and the equivalent fragment of the title compound are almost superimposable (r.m.s. deviation = 0.033 Å).
  13. Ketuly KA, Hadi AH, Khaledi H, Tiekink ER
    PMID: 21579426 DOI: 10.1107/S1600536810016661
    The asymmetric unit of the title compound {systematic name: (3S,8S,9S,10R,13R,14S,17R)-17-[(E,2R,5S)-5-ethyl-6-methyl-hept-3-en-2-yl]-10,13-dimethyl-2,3,4,7,8,9,11,12,14,15,16,17-dodeca-hydro-1H-cyclo-penta-[a]phenanthren-3-yl p-toluene-sulfonate}, C(36)H(54)O(3)S, comprises two independent mol-ecules that differ significantly in terms of the relative orientations of the peripheral groups; the conformation about the C=C bond of the side chain is E. In the crystal, mol-ecules associate into linear supra-molecular chains aligned along the a axis via C-H⋯O inter-actions.
  14. Abdullah N, Mohamadin MI, Safwan AP, Tiekink ER
    PMID: 21588481 DOI: 10.1107/S1600536810030436
    The title complex, [Cu(C(7)H(3)N(2)O(6))(2)(C(10)H(8)N(2))(H(2)O)]·C(4)H(8)O, features a penta-coordinate Cu(II) atom bound by two monodentate carboxyl-ate ligands, a bidentate 2,2'-bipyridine mol-ecule [dihedral angle between pyridine rings = 5.0 (2)°] and a water mol-ecule. The resulting N(2)O(3) donor set defines a distorted square-pyramidal geometry with the coordinated water mol-ecule in the apical position. In the crystal, the presence of O-H(w)⋯O(c) (w = water and c = carbon-yl) hydrogen bonding leads to the formation of a supra-molecular chain propagating along the c axis, which associates into a double chain via C-H⋯ O and π-π contacts between pyridyl rings [centroid-centroid distance = 3.527 (3) Å]. The solvent mol-ecules, which are disordered over two orientations in a 0.678 (11):0.322 (11) ratio, occupy voids defined by the complex mol-ecules and are held in place via C-H⋯O inter-actions.
  15. Fairuz ZA, Aiyub Z, Abdullah Z, Ng SW, Tiekink ER
    PMID: 21588477 DOI: 10.1107/S1600536810030187
    In the crystal structure of the title complex, [Cu(2)(CH(3)COO)(4)(C(12)H(11)ClN(2))(2)], the complete binuclear mol-ecule is generated by a crystallographic centre of inversion; the four acetate groups each bridge a pair of Cu(II) atoms. The coordination of the metal atom is distorted octa-hedral within a donor set defined by four O atoms, the heterocyclic N atom and the second Cu atom. The pyridine ring is twisted with respect to the benzene ring, forming a dihedral angle of 33.9 (2)°. An intra-molecular N-H⋯O hydrogen bond is present between the amino group and a carboxyl O atom. Inter-molecular inter-actions of the C-H⋯π type link mol-ecules in the crystal structure.
  16. Fairuz ZA, Aiyub Z, Abdullah Z, Ng SW, Tiekink ER
    PMID: 21588497 DOI: 10.1107/S1600536810031168
    The title complex, [Cu(2)(CH(3)COO)(4)(C(13)H(14)N(2))(2)], features a binuclear mol-ecule, which lies about a crystallographic centre of inversion; the four acetate ions each bridge a pair of Cu(II) atoms. The coordination of the metal atom is distorted octa-hedral within a donor set defined by four O atoms, the heterocyclic N atom and the second Cu atom. The pyridine ring is twisted with respect to the tolyl ring and forms a dihedral angle of 35.34 (9)°. A bifurcated N-H⋯(O,O) hydrogen bond is present, linking the amine group to two carboxyl-ate O atoms derived from different acetate ions. In the crystal, C-H⋯π inter-actions link mol-ecules into a supra-molecular array in the bc plane.
  17. Nasir SB, Abdullah Z, Fairuz ZA, Ng SW, Tiekink ER
    PMID: 21588464 DOI: 10.1107/S160053681003014X
    In the title compound, C(11)H(10)N(2)O(2), the benzene ring faces towards one of the pyrimidine N atoms, and is almost orthogonal to the plane through the pyrimidine ring [dihedral angle = 84.40 (14)°]. In the crystal, the presence of C-H⋯π and π-π [centroid-centroid separation = 3.7658 (18) Å] inter-actions leads to a supra-molecular array in the ac plane. The layers thus formed inter-digitate along the b axis.
  18. Fairuz ZA, Aiyub Z, Abdullah Z, Ng SW, Tiekink ER
    PMID: 21588463 DOI: 10.1107/S1600536810030138
    In the title compound, C(12)H(11)ClN(2), the dihedral angle between the benzene and pyridyl rings is 48.03 (8)°. Twists are also evident in the mol-ecule, in particular about the N(a)-C(b) (a = amine and b = benzene) bond [C-N-C-C = -144.79 (18)°]. In the crystal, inversion dimers linked by pairs of N-H⋯N hydrogen bonds result in the formation of eight-membered {⋯NCNH}(2) synthons [or R(2) (2)(8) loops].
  19. Hussen RS, Heidelberg T, Rodzi NZ, Ng SW, Tiekink ER
    PMID: 21754110 DOI: 10.1107/S1600536811008257
    The galactose ring in the title compound, C(21)H(24)O(11), has a chair conformation with the substituted benzene ring occupying an equatorial position. The crystal packing features C-H⋯O inter-actions that lead to the formation of supra-molecular layers in the ab plane.
  20. Heidelberg T, Hussen RS, Rodzi NZ, Ng SW, Tiekink ER
    PMID: 21754109 DOI: 10.1107/S1600536811008099
    The pyran-oside ring in the title compound, C(21)H(24)O(11), has a chair conformation with the substituted benzene ring occupying an equatorial position. The crystal packing is dominated by C-H⋯O inter-actions that lead to the formation of supra-molecular layers in the ab plane.
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