Displaying publications 1 - 20 of 138 in total

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  1. Jotani MM, Lee SM, Lo KM, Tiekink ERT
    Acta Crystallogr E Crystallogr Commun, 2019 May 01;75(Pt 5):624-631.
    PMID: 31110800 DOI: 10.1107/S2056989019004742
    The crystal and mol-ecular structures of C14H12Cl2, (I), and C14H12Br2, (II), are described. The asymmetric unit of (I) comprises two independent mol-ecules, A and B, each disposed about a centre of inversion. Each mol-ecule approximates mirror symmetry [the Cb-Cb-Ce-Ce torsion angles = -83.46 (19) and 95.17 (17)° for A, and -83.7 (2) and 94.75 (19)° for B; b = benzene and e = ethyl-ene]. By contrast, the mol-ecule in (II) is twisted, as seen in the dihedral angle of 59.29 (11)° between the benzene rings cf. 0° in (I). The mol-ecular packing of (I) features benzene-C-H⋯π(benzene) and Cl⋯Cl contacts that lead to an open three-dimensional (3D) architecture that enables twofold 3D-3D inter-penetration. The presence of benzene-C-H⋯π(benzene) and Br⋯Br contacts in the crystal of (II) consolidate the 3D architecture. The analysis of the calculated Hirshfeld surfaces confirm the influence of the benzene-C-H⋯π(benzene) and X⋯X contacts on the mol-ecular packing and show that, to a first approximation, H⋯H, C⋯H/H⋯C and C⋯X/X⋯C contacts dominate the packing, each contributing about 30% to the overall surface in each of (I) and (II). The analysis also clearly differentiates between the A and B mol-ecules of (I).
  2. Lee SM, Lo KM, Tan SL, Tiekink ER
    Acta Crystallogr E Crystallogr Commun, 2016 Oct 1;72(Pt 10):1390-1395.
    PMID: 27746926
    The Yb(III) atom in the title complex, [Yb(C27H24Cl3N4O3)] [systematic name: (2,2',2''-{(nitrilo)-tris-[ethane-2,1-di-yl(nitrilo)-methylyl-idene]}tris-(4-chloro-phenolato)ytterbium(III)], is coordinated by a trinegative, hepta-dentate ligand and exists within an N4O3 donor set, which defines a capped octa-hedral geometry whereby the amine N atom caps the triangular face defined by the three imine N atoms. The packing features supra-molecular layers that stack along the a axis, sustained by a combination of aryl-C-H⋯O, imine-C-H⋯O, methyl-ene-C-H⋯π(ar-yl) and end-on C-Cl⋯π(ar-yl) inter-actions. A Hirshfeld surface analysis points to the major contributions of C⋯H/ H⋯C and Cl⋯H/H⋯Cl inter-actions (along with H⋯H) to the overall surface but the Cl⋯H contacts are at distances greater than the sum of their van der Waals radii.
  3. Suwardi SA, Lee SM, Lo KM, Jotani MM, Tiekink ER
    Acta Crystallogr E Crystallogr Commun, 2017 Mar 01;73(Pt 3):429-433.
    PMID: 28316825 DOI: 10.1107/S2056989017002705
    The title compound, [Cd2(C8H8NS2)4], is a centrosymmetric dimer with both chelating and μ2-tridentate di-thio-carbamate ligands. The resulting S5 donor set defines a Cd(II) coordination geometry inter-mediate between square-pyramidal and trigonal-bipyramidal, but tending towards the former. The packing features C-H⋯S and C-H⋯π inter-actions, which generate a three-dimensional network. The influence of these inter-actions, along with intra-dimer π-π inter-actions between chelate rings, has been investigated by an analysis of the Hirshfeld surface.
  4. 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.
  5. Chew ST, Lo KM, Lee SK, Heng MP, Teoh WY, Sim KS, et al.
    Eur J Med Chem, 2014 Apr 9;76:397-407.
    PMID: 24602785 DOI: 10.1016/j.ejmech.2014.02.049
    Four new copper(II) complexes containing phosphonium substituted hydrazone (L) with the formulations [CuL]Cl(3), [Cu(phen)L]Cl(4), [Cu(bpy)L]Cl(5), [Cu(dbpy)L]Cl(6), (where L = doubly deprotonated hydrazone; phen = 1,10'-phenanthroline; bpy = 2,2'-bipyridine; dbpy = 5,5'-dimethyl-2,2'-bipyridine) have been synthesized. The compounds were characterized by elemental analysis, spectroscopic methods and in the case of crystalline products by X-ray crystallography. The cytotoxicity and topoisomerase I (topo I) inhibition activities of these compounds were studied. It is noteworthy that the addition of N,N-ligands to the copper(II) complex lead to the enhancement in the cytotoxicity of the compounds, especially against human prostate adenocarcinoma cell line (PC-3). Complex 4 exhibits the highest activity against PC-3 with the IC₅₀ value of 3.2 μΜ. The complexes can also inhibit topo I through the binding to DNA and the enzyme.
  6. Ng S, Sathasivam RV, Lo KM, Xie Y, Schaefer HF
    J Phys Chem A, 2005 Dec 29;109(51):12059-63.
    PMID: 16366662
    The Woessner approach is applied to the 13C relaxation data for tetraphenyltin (1) and tetra(p-tolyl)tin (2) in CDCl3 solution over the temperature range 5-42 degrees C to obtain correlation times for rotational motions and hence the activation barriers. Quantum mechanical computations were carried out to obtain the rotational energy barriers for comparison. For 2 the relaxation data indicate (1) slower ring rotation than in 1, (2) highly hindered internal rotation of the methyl group. IR and chemical shift data support the hypothesis of hyperconjugation of the methyl correlated with interaction between the pi-electrons and the 5d orbitals of tin in the (p-tolyl)Sn moiety to account for the hindrances to the rotations of the ring and the methyl. The activation barrier for the tolyl group rotation is found to be much higher than that for the phenyl rotation. However, the Woessner approach yields an anomalously high barrier for the methyl rotation. An explanation based on correlated rotations of the tolyl ring and the methyl is offered.
  7. Lee SM, Lo KM, Mohd Ali H, Robinson WT
    PMID: 21582732 DOI: 10.1107/S1600536809023150
    The title compound, [Sn(C(6)H(5))(3)(C(17)H(25)O(3)S)](n), comprises two symmetry-independent five-coordinated triphenyl-tin mol-ecules which are linked by carboxyl-ate bridges into a polymeric chain. The Sn(IV) atom is in a distorted trans-C(3)SnO(2) trigonal-bipyramidal geometry. The presence of two bulky tert-butyl groups on the benzene ring prevents any hydrogen-bonding inter-actions involving the hydroxyl substituents.
  8. Lee SM, Lo KM, Mohd Ali H, Robinson WT
    PMID: 21577403 DOI: 10.1107/S1600536809030323
    In the title compound, (C(7)H(11)N(2))(2)[SnBr(4)(C(7)H(7))(2)], the tetra-bromidobis(4-methyl-phen-yl)stannate(IV) anion possesses a centre of inversion located at the Sn(IV) atom. In the crystal structure, two inversion-related cations are linked to the anion via weak N-H⋯Br hydrogen bonds.
  9. Lee SM, Lo KM, Mohd Ali H, Robinson WT
    PMID: 21577402 DOI: 10.1107/S1600536809030232
    In the title compound, (C(7)H(11)N(2))(2)[SnBr(4)(C(6)H(4)Cl)(2)]·C(6)H(4)BrCl, the Sn(IV) atom in the tetra-bromidobis(4-chloro-phen-yl)stannate(IV) anion lies on a centre of inversion. The distances between the 4-(dimethyl-amino)pyridinium N atom and the Br atoms of the anion are 3.450 (2) and 3.452 (2) Å, suggesting weak hydrogen bonding. The 4-bromo-chloro-benzene solvent mol-ecule, which is a bromination by-product from the reaction, is disordered about a twofold rotation axis with approximately equal occupancy.
  10. Ngan NK, Lo KM, Richard Wong CS
    PMID: 21836856 DOI: 10.1107/S1600536811020290
    The coordination geometry at the Mo(VI) atom in the title compound, [Mo(C(16)H(14)N(2)O(4))O(2)(C(2)H(6)OS)], is distorted octa-hedral. The phenolate O, imino N, oxide O from the enolized carbonyl group and one of the terminal O atoms form the equatorial plane; the axial positions are occupied by the other terminal O atom of the dioxidomolybdenum group and the donor O atom of DMSO. The O=Mo=O angle is 105.31 (6)°. An intra-molecular O-H⋯N hydrogen bond and weak inter-molecular C-H⋯O hydrogen bonds are present in the structure.
  11. Keng TC, Lo KM, Ng SW
    PMID: 21836954 DOI: 10.1107/S1600536811023919
    In the title carboxyl-ate-bridged polymer, [Sn(C(7)H(7))(3)(C(7)H(5)O(3))](n), the Sn(IV) atom exists in a distorted trans-C(3)SnO(2) trigonal-bipyramidal geometry. The polymer propagates as a chain along the a axis. There are two independent formula units in the asymmetric unit; the furyl ring of one of the anions is disordered over two positions in a 0.630 (8):0.370 (8) ratio. The crystal studied was a non-merohedral twin with a minor twin domain of 37.3 (1)%.
  12. Keng TC, Lo KM, Ng SW
    PMID: 21754570 DOI: 10.1107/S1600536811015686
    The six-coordinate Sn(IV) atom in the title compound, [Sn(C(7)H(6)F)(2)Cl(2)(C(10)H(8)N(2))], shows a trans-C(2)SnN(2)Cl(2) octa-hedral coordination [C-Sn-C = 174.81 (10) and 176.71 (9)° in the two independent mol-ecules in the asymmetric unit]; the Cl atoms are cis to each other as are the N atoms of the chelating N-heterocycle.
  13. Keng TC, Lo KM, Ng SW
    PMID: 21754610 DOI: 10.1107/S1600536811016436
    The formyl-meth-oxy-nitro-phenoxide ions in the polymeric title compound, [Sn(C(7)H(7))(3)(C(8)H(6)NO(5))](n), link adjacent triorganotin(IV) cations into linear chains lying close to (101) [Sn-O = 2.1227 (12) Å and Sn← O = 2.4936 (13) Å]. The Sn(IV) atom is displaced out of the C(3)Sn girdle of the trans-C(3)SnO(2) trigonal-bipyramidal polyhedron in the direction of the covalently-bonded O atom [Sn-O-C = 137.63 (11)°] by 0.247 (1) Å; the geometry is distorted towards an octa-hedron by a remote O atom of the meth-oxy subsituent [Sn⋯O = 3.019 (1) Å].
  14. Raja I, Lo KM, Ng SW
    PMID: 21754583 DOI: 10.1107/S1600536811015935
    The O-C(6)H(4)-CH=N-C(6)H(4)-O dianion of the title compound, [Mn(C(13)H(9)NO(2))(C(7)H(5)O(2))(C(2)H(6)OS)], acts as an O,N,O'-chelate to bind to the Mn(III) atom, and the three atoms constitute three points [O-Mn-O = 174.43 (11)°] of an octa-hedron around the metal atom. The azomethine linkage is disordered over two positions in a 0.657 (13):0.343 (13) ratio. The deprotonated salicyldehyde anion acts as an O,O'-chelate; the sixth coordination site is represented by the O atom of the dimethyl sulfoxide mol-ecule. The crystal studied was a non-merohedral twin with a minor twin component of 14.2 (3)%.
  15. Keng TC, Lo KM, Ng SW
    PMID: 21754574 DOI: 10.1107/S1600536811015728
    In the title mol-ecule, [Sn(C(7)H(6)Cl)(2)(C(6)H(4)NO(2))(2)(H(2)O)], the O atoms of the two chelating nicotinate groups and the O atom of the coordinated water mol-ecule comprise the penta-gonal plane of the trans-C(2)SnO(5) penta-gonal-bipyramid [C-Sn-C = 178.62 (11) °] surrounding the Sn(IV) atom. In the crystal, adjacent mol-ecules are linked by O-H⋯N hydrogen bonds, generating a chain running along the body diagonal of the triclinic unit cell.
  16. Keng TC, Lo KM, Ng SW
    PMID: 21754573 DOI: 10.1107/S1600536811015716
    The dinuclear title complex, [Sn(2)(C(7)H(6)Cl)(4)(C(9)H(16)NO(2)S(2))(4)], lies on a center of inversion. The Sn(IV) atoms are chelated by one of the two carboxyl-ate ions; the other carboxyl-ate ion bridges two metal atoms. The geometry of the six-coordinate Sn(IV) atom is a distorted trans-C(2)SnO(4) octa-hedron [C-Sn-C = 155.32 (8)°].
  17. Keng TC, Lo KM, Ng SW
    PMID: 21754576 DOI: 10.1107/S1600536811015741
    The Sn(IV) atom in the title compound, [Sn(C(7)H(6)Cl)(3)(C(10)H(9)O(2))], exists in a tetra-hedral geometry [Σ C-Sn-C = 341.5 (4)°]. If the doubly bonded carbonyl O atom is taken into account for the coordination sphere of Sn [Sn⋯O = 2.808 (2) Å], the coordination geometry can be described as a cis-penta-gonal bipyramid.
  18. Keng TC, Lo KM, Ng SW
    PMID: 21754575 DOI: 10.1107/S160053681101573X
    The Sn(IV) atom in the three independent mol-ecules of the title compound, [Sn(C(7)H(6)Cl)(2)(C(9)H(6)NO)Cl], is N,O-chelated by the quinolin-8-olate anion and exists in a cis-C(2)SnNOCl trigonal-bipyramidal geometry; the O atom of the anion and the two benzyl C atoms lie in the equatorial plane.
  19. Keng TC, Lo KM, Ng SW
    PMID: 21754572 DOI: 10.1107/S1600536811015704
    The six-coordinate Sn(IV) atom in the title compound, [SnCl(4)(C(14)H(14)OS)(2)], exists in a cis-SnCl(4)O(2) octa-hedral geometry. Of the four Cl atoms, two are close to adjacent S atoms [Cl⋯S = 3.320 (1) and 3.376 (1) Å]; the Sn-Cl bonds involving these two Cl atoms are longer than the other two Sn-Cl bonds.
  20. Keng TC, Lo KM, Ng SW
    PMID: 21754571 DOI: 10.1107/S1600536811015698
    The six-coordinate Sn(IV) atom in the title compound, [Sn(C(8)H(9))Cl(3)(C(3)H(4)N(2))(2)], shows an octa-hedral coordination. The N atoms of the N-heterocycle are cis to each other. The Sn-N bond that is trans to the Sn-C bond is shorter than the Sn-N bond trans to the Sn-Cl bond. Weak N-H⋯Cl hydrogen bonds link adjacent mol-ecules, generating a double chain running along the c axis.
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