Displaying publications 1 - 20 of 136 in total

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  1. Arman HD, Poplaukhin P, Tiekink ER
    PMID: 24426981 DOI: 10.1107/S1600536813021569
    The asymmetric unit of title salt co-crystal, [K(C9H11N2S2)(C12H24O6)], comprises a K(+) cation, an (-)S2CN(Et)py anion and a 18-crown-6 mol-ecule. Substantial delocalization of π-electron density is evident in the di-thio-carbamate anion, as indicated by the equivalent C-S bond lengths. The K(+) cation sits within an O6S2 donor set lying 0.7506 (6) Å out of the least-squares plane through the six O atoms (r.m.s. deviation = 0.1766 Å) of the 18-crown-6 mol-ecule with the two S atoms being on one side of this plane. Supra-molecular layers in the bc plane, sustained by C-H⋯O and C-H⋯π inter-actions, feature in the crystal packing.
  2. Affan MA, Salam MA, Asaruddin MR, Ng SW, Tiekink ER
    Acta Crystallogr Sect E Struct Rep Online, 2012 Jul 1;68(Pt 7):m909-10.
    PMID: 22807748 DOI: 10.1107/S1600536812025937
    Two independent mol-ecules comprise the asymmetric unit in the title compound, [Sn(C₄H₉)(C₁₄H₁₉N₄S)Cl₂]. In each mol-ecule, the Sn(IV) atom exists within a distorted octa-hedral geometry defined by the N,N',S-tridentate mono-deprotonated Schiff base ligand, two mutually trans Cl atoms, and the α-C atom of the n-butyl group; the latter is trans to the azo-N atom. The greatest distortion from the ideal geometry is found in the nominally trans angle formed by the S and pyridyl-N atoms at Sn [151.72 (7) and 152.04 (7)°, respectively]. In the crystal, mol-ecules are consolidated into a three-dimensional architecture by a combination of N-H⋯Cl, C-H⋯π and π-π inter-actions [inter-centroid distances = 3.6718 (19) and 3.675 (2) Å].
  3. Tan SL, Lee SM, Heard PJ, Halcovitch NR, Tiekink ER
    Acta Crystallogr E Crystallogr Commun, 2017 Feb 01;73(Pt 2):213-218.
    PMID: 28217345 DOI: 10.1107/S2056989017000755
    The title compound, [Re(C3H6NS2)(C2H3N)(CO)3], features an octa-hedrally coordinated Re(I) atom within a C3NS2 donor set defined by three carbonyl ligands in a facial arrangement, an aceto-nitrile N atom and two S atoms derived from a symmetrically coordinating di-thio-carbamate ligand. In the crystal, di-thio-carbamate-methyl-H⋯O(carbon-yl) inter-actions lead to supra-molecular chains along [36-1]; both di-thio-carbamate S atoms participate in intra-molecular methyl-H⋯S inter-actions. Further but weaker aceto-nitrile-C-H⋯O(carbonyl) inter-actions assemble mol-ecules in the ab plane. The nature of the supra-molecular assembly was also probed by a Hirshfeld surface analysis. Despite their weak nature, the C-H⋯O contacts are predominant on the Hirshfeld surface and, indeed, on those of related [Re(CO)3(C3H6NS2)L] structures.
  4. 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.
  5. Jotani MM, Poplaukhin P, Arman HD, Tiekink ER
    Acta Crystallogr E Crystallogr Commun, 2016 Aug 01;72(Pt 8):1085-92.
    PMID: 27536388 DOI: 10.1107/S2056989016010768
    The asymmetric unit of the title compound, [Cd2(C12H10N2)3(C6H12NOS2)4]·4C2H3N, comprises a Cd(II) atom, two di-thio-carbamate (dtc) anions, one and a half trans-1,2-dipyridin-4-yl-ethyl-ene (bpe) mol-ecules and two aceto-nitrile solvent mol-ecules. The full binuclear complex is generated by the application of a centre of inversion. The dtc ligands are chelating, one bpe mol-ecule coordinates in a monodentate mode while the other is bidentate bridging. The resulting cis-N2S4 coordination geometry is based on an octa-hedron. Supra-molecular layers, sustained by hy-droxy-O-H⋯O(hy-droxy) and hy-droxy-O-H⋯N(bpe) hydrogen bonding, inter-penetrate to form a three-dimensional architecture; voids in this arrangement are occupied by the aceto-nitrile solvent mol-ecules. Additional inter-molecular inter-actions falling within the specified framework have been analysed by Hirshfeld surface analysis, including π-π inter-actions.
  6. Mohamad R, Awang N, Kamaludin NF, Jotani MM, Tiekink ER
    Acta Crystallogr E Crystallogr Commun, 2016 Oct 1;72(Pt 10):1480-1487.
    PMID: 27746946
    The crystal and mol-ecular structures of two tri-phenyl-tin di-thio-carbamates, [Sn(C6H5)3(C16H16NS2)], (I), and [Sn(C6H5)3(C7H14NO2S2)], (II), are described. In (I), the di-thio-carbamate ligand coordinates the Sn(IV) atom in an asymmetric manner, leading to a highly distorted trigonal-bipyramidal coordination geometry defined by a C3S2 donor set with the weakly bound S atom approximately trans to one of the ipso-C atoms. A similar structure is found in (II), but the di-thio-carbamate ligand coordinates in an even more asymmetric fashion. The packing in (I) features supra-molecular chains along the c axis sustained by C-H⋯π inter-actions; chains pack with no directional inter-actions between them. In (II), supra-molecular layers are formed, similarly sustained by C-H⋯π inter-actions; these stack along the b axis. An analysis of the Hirshfeld surfaces for (I) and (II) confirms the presence of the C-H⋯π inter-actions but also reveals the overall dominance of H⋯H contacts in the respective crystals.
  7. Tan SL, Yeo CI, Heard PJ, Akien GR, Halcovitch NR, Tiekink ER
    Acta Crystallogr E Crystallogr Commun, 2016 Dec 01;72(Pt 12):1799-1805.
    PMID: 27980834
    The title compound, [Cu(C5H5NO2S2)(C18H15P)2]·CHCl3, features a tetra-hedrally coordinated CuI atom within a P2S2 donor set defined by two phosphane P atoms and by two S atoms derived from a symmetrically coordinating di-thio-carbamate ligand. Both intra- and inter-molecular hy-droxy-O-H⋯O(hydroxy) hydrogen bonding is observed: the former closes an eight-membered {⋯HOC2NC2O} ring, whereas the latter connects centrosymmetrically related mol-ecules into dimeric aggregates via eight-membered {⋯H-O⋯H-O}2 synthons. The complex mol-ecules are arranged to form channels along the c axis in which reside the chloro-form mol-ecules, being connected by Cl⋯π(arene) and short S⋯Cl [3.3488 (9) Å] inter-actions. The inter-molecular inter-actions have been investigated further by Hirshfeld surface analysis, which shows the conventional hydrogen bonding to be very localized with the main contributors to the surface, at nearly 60%, being H⋯H contacts. Solution NMR studies indicate that whilst the same basic mol-ecular structure is retained in solution, the tri-phenyl-phosphane ligands are highly labile, exchanging rapidly with free Ph3P at room temperature.
  8. Rosely SN, Hussen RS, Lee SM, Halcovitch NR, Jotani MM, Tiekink ER
    Acta Crystallogr E Crystallogr Commun, 2017 Mar 01;73(Pt 3):390-396.
    PMID: 28316817 DOI: 10.1107/S2056989017002365
    The title diorganotin compound, [Sn(CH3)2(C28H32N2O4)], features a distorted SnC2NO2 coordination geometry almost inter-mediate between ideal trigonal-bipyramidal and square-pyramidal. The dianionic Schiff base ligand coordinates in a tridentate fashion via two alkoxide O and hydrazinyl N atoms; an intra-molecular hy-droxy-O-H⋯N(hydrazin-yl) hydrogen bond is noted. The alk-oxy chain has an all-trans conformation, and to the first approximation, the mol-ecule has local mirror symmetry relating the two Sn-bound methyl groups. Supra-molecular layers sustained by imine-C-H⋯O(hy-droxy), π-π [between dec-yloxy-substituted benzene rings with an inter-centroid separation of 3.7724 (13) Å], C-H⋯π(arene) and C-H⋯π(chelate ring) inter-actions are formed in the crystal; layers stack along the c axis with no directional inter-actions between them. The presence of C-H⋯π(chelate ring) inter-actions in the crystal is clearly evident from an analysis of the calculated Hirshfeld surface.
  9. Lee SM, Lo KM, Tan SL, Tiekink ER
    Acta Crystallogr E Crystallogr Commun, 2016 Aug 1;72(Pt 8):1223-7.
    PMID: 27536419 DOI: 10.1107/S2056989016012159
    In the solid state, the title compound, C12H16BrNO5 [systematic name: 4-bromo-2-((1E)-{[1,3-dihy-droxy-2-(hy-droxy-meth-yl)propan-2-yl]iminium-yl}meth-yl)-6-meth-oxy-benzen-1-olate], C12H16BrNO5, is found in the keto-amine tautomeric form, with an intra-molecular iminium-N-H⋯O(phenolate) hydrogen bond and an E conformation about the C=N bond. Both gauche (two) and anti relationships are found for the methyl-hydroxy groups. In the crystal, a supra-molecular layer in the bc plane is formed via hy-droxy-O-H⋯O(hy-droxy) and charge-assisted hy-droxy-O-H⋯O(phenolate) hydrogen-bonding inter-actions; various C-H⋯O inter-actions provide additional cohesion to the layers, which stack along the a axis with no directional inter-actions between them. A Hirshfeld surface analysis confirms the lack of specific inter-actions in the inter-layer region.
  10. Otero-de-la-Roza A, Luaña V, Tiekink ER, Zukerman-Schpector J
    J Chem Theory Comput, 2014 Nov 11;10(11):5010-9.
    PMID: 26584384 DOI: 10.1021/ct500832g
    Noncovalent interactions are prevalent in crystal packing and supramolecular chemistry. Directional noncovalent interactions such as donor-acceptor bonds (e.g., hydrogen, chalcogen, and pnictogen bonds) as well as nondirectional forces (such as dispersion) come together to stabilize supramolecular assemblies by striking a delicate energetic balance. Typically, a two-pronged approach employing experimental X-ray structures and gas phase quantum chemical modeling has been used to understand and design supramolecular architectures. Drawing from recent advances in molecular crystal modeling with dispersion corrected density functional theory (DFT), we propose in this article a combination of qualitative noncovalent index (NCI) analysis and periodic and gas phase DFT calculations on substitutional crystal analogues to unravel the dominant interactions in a particular crystal packing. We illustrate the possibilities of this approach by studying three crystal packings of epoxydihydroarsanthrene analogues that present a complex combination of donor-acceptor interactions including pnictogen-pnictogen, pnictogen-π, and pnictogen-chalcogen. We show that, in these crystals, the chalcogen-pnictogen interaction dominates over the pnictogen-pnictogen and pnictogen-π. In the latter, the role of donor and acceptor is reversed depending on the interacting moieties. Multiple chalcogen-pnictogen interactions necessitate larger donor atoms, such as sulfur. These observations explain and rationalize the experimentally observed crystal structures.
  11. Wardell JL, Jotani MM, Tiekink ER
    Acta Crystallogr E Crystallogr Commun, 2016 Dec 01;72(Pt 12):1691-1699.
    PMID: 27980811
    The crystal structures of two ammonium salts of 2-amino-4-nitro-benzoic acid are described, namely di-methyl-aza-nium 2-amino-4-nitro-benzoate, C2H8N+·C7H5N2O4-, (I), and di-butyl-aza-nium 2-amino-4-nitro-benzoate, C8H20N+·C7H5N2O4-, (II). The asymmetric unit of (I) comprises a single cation and a single anion. In the anion, small twists are noted for the carboxyl-ate and nitro groups from the ring to which they are connected, as indicated by the dihedral angles of 11.45 (13) and 3.71 (15)°, respectively; the dihedral angle between the substituents is 7.9 (2)°. The asymmetric unit of (II) comprises two independent pairs of cations and anions. In the cations, different conformations are noted in the side chains in that three chains have an all-trans [(+)-anti-periplanar] conformation, while one has a distinctive kink resulting in a (+)-synclinal conformation. The anions, again, exhibit twists with the dihedral angles between the carboxyl-ate and nitro groups and the ring being 12.73 (6) and 4.30 (10)°, respectively, for the first anion and 8.1 (4) and 12.6 (3)°, respectively, for the second. The difference between anions in (I) and (II) is that in the anions of (II), the terminal groups are conrotatory, forming dihedral angles of 17.02 (8) and 19.0 (5)°, respectively. In each independent anion of (I) and (II), an intra-molecular amino-N-H⋯O(carboxyl-ate) hydrogen bond is formed. In the crystal of (I), anions are linked into a jagged supra-molecular chain by charge-assisted amine-N-H⋯O(carboxyl-ate) hydrogen bonds and these are connected into layers via charge-assisted ammonium-N-H⋯O(carboxyl-ate) hydrogen bonds. The resulting layers stack along the a axis, being connected by nitro-N-O⋯π(arene) and methyl-C-H⋯O(nitro) inter-actions. In the crystal of (II), the anions are connected into four-ion aggregates by charge-assisted amino-N-H⋯O(carboxyl-ate) hydrogen bonding. The formation of ammonium-N-H⋯O(carboxyl-ate) hydrogen bonds, involving all ammonium-N-H and carboxyl-ate O atoms leads to a three-dimensional architecture; additional C-H⋯O(nitro) inter-actions contribute to the packing. The Hirshfeld surface analysis confirms the importance of the hydrogen bonding in both crystal structures. Indeed, O⋯H/H⋯O inter-actions contribute nearly 50% to the entire Hirshfeld surface in (I).
  12. Tiekink ER
    Dalton Trans, 2012 Jun 7;41(21):6390-5.
    PMID: 22252404 DOI: 10.1039/c2dt12225a
    Despite being disparaged for their malodorous and toxic demeanour, compounds of selenium, a bio-essential element, and tellurium, offer possibilities as therapeutic agents. Herein, their potential use as drugs, for example, as anti-viral, anti-microbial, anti-inflammatory agents, etc., will be surveyed along with a summary of the established biological functions of selenium. The natural biological functions of tellurium remain to be discovered.
  13. Yeo CI, Ooi KK, Akim AM, Ang KP, Fairuz ZA, Halim SN, et al.
    J Inorg Biochem, 2013 Oct;127:24-38.
    PMID: 23850666 DOI: 10.1016/j.jinorgbio.2013.05.011
    The Ph3PAu[SC(OR)=NPh], R=Me (1), Et (2) and iPr (3), compounds are significantly cytotoxic to the HT-29 cancer cell line with 1 being the most active. Based on human apoptosis PCR-array analysis, caspase activities, DNA fragmentation, cell apoptotic assays, intracellular reactive oxygen species (ROS) measurements and human topoisomerase I inhibition, induction of apoptosis is demonstrated and both the extrinsic and intrinsic pathways of apoptosis have been shown to occur. Compound 1 activates the p73 gene, whereas each of 2 and 3 activates the p53 gene. An additional apoptotic mechanism is exhibited by 2, that is, via the JNK/MAP pathway.
  14. Siddiqui R, Abjani F, Yeo CI, Tiekink ER, Khan NA
    J Negat Results Biomed, 2017 Apr 03;16(1):6.
    PMID: 28366172 DOI: 10.1186/s12952-017-0070-7
    BACKGROUND: Gold compounds have shown promise in the treatment of non-communicable diseases such as rheumatoid arthritis and cancer, and are considered of value as anti-microbial agents against Gram-negative and Gram-positive bacteria, and have anti-parasitic properties against Schistosoma mansoni, Trypanosoma brucei, Plasmodium falciparum, Leishmania infantinum, Giardia lamblia, and Entamoeba histolytica. They are known to affect enzymatic activities that are required for the cellular respiration processes.

    METHODS: Anti-amoebic effects of phosphanegold(I) thiolates were tested against clinical isolate of A. castellanii belonging to the T4 genotype by employing viability assays, growth inhibition assays, encystation assays, excystation assays, and zymographic assays.

    RESULTS: The treatment of A. castellanii with the phosphanegold(I) thiolates tested (i) had no effect on the viability of A. castellanii as determined by Trypan blue exclusion test, (ii) did not affect amoebae growth using PYG growth medium, (iii) did not inhibit cellular differentiation, and (iv) had no effect on the extracellular proteolytic activities of A. castellanii.

    CONCLUSION: Being free-living amoeba, A. castellanii is a versatile respirator and possesses respiratory mechanisms that adapt to various aerobic and anaerobic environments to avoid toxic threats and adverse conditions. For the first time, our findings showed that A. castellanii exhibits resistance to the toxic effects of gold compounds and could prove to be an attractive model to study mechanisms of metal resistance in eukaryotic cells.

  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. 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.
  18. 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.
  19. Zukerman-Schpector J, Madureira LS, Wulf GD, Stefani HA, Vasconcelos SN, Ng SW, et al.
    Molecules, 2014;19(2):1990-2003.
    PMID: 24531216 DOI: 10.3390/molecules19021990
    Two independent molecules that differ in terms of rotation about the central S-N bond comprise the asymmetric unit of the title compound 1. The molecules have a V-shape with the dihedral angles between the fused ring system and benzene ring being 79.08(6)° and 72.83(5)°, respectively. The packing is mostly driven by p···p interactions occurring between the tolyl ring of one molecule and the C6 ring of the indole fused ring system of the other. DFT and IRC calculations for these and related 1-(arylsulfonyl)indole molecules showed that the rotational barrier about the S-N bond between conformers is within the 2.5-5.5 kcal/mol range. Crystal data for C16H13NO3S (1): Mr = 299.33, space group Pna21, a = 19.6152(4) Å, b = 11.2736(4) Å, c = 12.6334(3) Å, V = 2793.67(13) Å3, Z = 8, Z' = 2, R = 0.034.
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