Seik Weng Ng

King Abdulaziz University, Djidda, Makkah, Saudi Arabia

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Publications (797)305.9 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Two lead(II) coordination polymers, [Pb2(4,4′-bipy)(NO3)4]n (1) and [Pb4(4,4′-bipy)2(NO3)8(PhN2O2)2]n (2), were synthesized by reaction of lead(II) nitrate with the 4,4′-bipyridine (4,4′-bipy) and cupferron ([PhN(O)NO]NH4) ligands and characterized by 1H and 13C NMR, IR, and UV spectroscopies and elemental analysis. The molecular structure of 2 was determined by single-crystal X-ray diffraction. Photoluminescence studies of complexes showed that a good correlation exists between the structures of complexes and emission wavelengths. Utilization of cupferron ligand as a second ligand in the structure of 2 resulted in a red-shift in the both absorption and fluorescence spectra and moderately enhanced the photoluminescence intensity. Lead(II) oxide core that resulted from direct thermal decomposition of complex 2 at 600 °C in air was characterized by X-ray powder diffraction and scanning electron microscopy. The photoluminescence emission spectrum of PbO nanoparticles revealed a strong blue emission band centered at 472 nm, which might be associated with oxygen vacancies.
    Journal of Molecular Structure 03/2015; 1083. DOI:10.1016/j.molstruc.2014.12.019 · 1.60 Impact Factor
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    ABSTRACT: The molecular structure of 2 with intramolecular C-H center dot center dot center dot Cu, C-H center dot center dot center dot pi and hydrogen bonding interactions. New Co(II) and Cu(II) diphenate complexes with 4-methylimidazole were synthesized and characterized through elemental analysis, magnetic susceptibilities, and IR spectroscopic studies. The crystal structures of [Co(dpa)(5-meim)(4)]center dot 2H(2)O (1) and [Cu(dpa)(4-meim)(5-meim)(2)]center dot H2O (2) were determined by single-crystal X-ray diffraction (H(2)dpa = diphenic acid, 4-meim = 4-methylimidazole and 5-meim = 5-methylimidazole). In 1, Co(II) has distorted octahedral geometry with four 5-meim and one diphenate ligands. Complex 2 has distorted trigonal bipyramidal geometry with one 4-methylimidazole, two 5-methylimidazole, and one diphenate ligands. In the complexes, the diphenate is coordinated to the metal(II) ions via the deprotonated oxygens of carboxylate as a bidentate ligand. The 4-meim and 5-meim linkage isomers within the same complex are found, and this complex is an unusual example. Moreover, another interesting feature of 2 is the presence of C-H center dot center dot center dot Cu weak hydrogen-bonding interactions.
    Journal of Coordination Chemistry 09/2014; 67(15):2564-2575. DOI:10.1080/00958972.2014.946916 · 2.22 Impact Factor
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    ABSTRACT: Two isoreticular metal–organic frameworks with chemical formulae [Cu(L)(4,4’-bipy)(H2O)]n•1.5nCH3CN (1) and [Cu(L)(4,4’-bipy)(H2O)]n•4nH2O (2) (H2L= diphenylmethane-4,4'-dicarboxylic acid) were synthesized and structurally characterized. They show CdSO4 (65.8) net and have obvious 1-D channel that spread along the crystallographic c axis. More importantly, 1 shows high selectivity for H2 over N2 and CO2 at low pressure, which could be confirmed via computational calculations using Connolly algorithm to reveals the size and shape of accessible voids. The incorporation of the drug 5-fluorouracil (5-FU) into the desolvated 1 was around 27.5 wt% per gram of dehydrated 1. 5-FU is released in a highly controlled and progressive fashion with 61 % of the drug released after 95 hours. In addition, we have applied molecular docking calculations to investigate the preferred conformation of 5-FU molecules upon binding to MOF 1. These calculations provide a structural basis to explain the 5-FU release from MOF 1.
    Dalton Transactions 09/2014; 43(46). DOI:10.1039/C4DT01890G · 4.10 Impact Factor
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    Dataset: khair abadi
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    ABSTRACT: In the title salt, C14H18N2(2+)·2C9H5N4O(-), the 1,1'-diethyl-4,4'-bipyridine-1,1'-diium dication lies across a centre of inversion in the space group P21/c. In the 1,1,3,3-tetracyano-2-ethoxypropenide anion, the two independent -C(CN)2 units are rotated, in conrotatory fashion, out of the plane of the central propenide unit, making dihedral angles with the central unit of 16.0 (2) and 23.0 (2)°. The ionic components are linked by C-H...N hydrogen bonds to form a complex sheet structure, within which each cation acts as a sixfold donor of hydrogen bonds and each anion acts as a threefold acceptor of hydrogen bonds.
    03/2014; 70(Pt 3):338-41. DOI:10.1107/S2053229614004379
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    ABSTRACT: Six triangular silver(I) or gold(I) 4-chloro/iodo-3,5-diphenyl pyrazolates, as well as a triangular silver(I) 4-methyl-3,5-diphenyl pyrazolate, have been synthesized and structurally characterized by single-crystal X-ray diffraction. Comparison and inspection of the Ag/AuCl/I distances, geometries of C-Cl/I bonds with respect to the Ag3 or Au3 triangles, and crystal packing diagrams verify the existence of Ag3Cl/I or Au3I interactions in some of the structures of the trimers, which are strong enough to impart a substantial effect on the spatial arrangement of the trimers in their solid states. Density function theory (DFT) calculations on the trimers give the molecular electrostatic potential (MEP) surfaces and HOMO/LUMOs, which support that the observed M3X structural motifs can be understood on the basis of a weak acid-base interaction having contributions from both ionic δ+δ− attraction and covalent LUMO-HOMO overlap. Calculations also show the existence of the so-called “σ-hole” and the secondary effect to it on the halogen atoms; the structural roles played by them were discussed based on the crystal structures.
    CrystEngComm 01/2014; 16(23):4987. DOI:10.1039/c4ce00029c · 3.86 Impact Factor
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    ABSTRACT: Reported here is a new CdII-based metal-organic framework (MOF), ROD-8, based on the rod secondary building unit (SBU) and tetratopic linker 1,3,6,8-tetrakis(p-benzoic acid)pyrene. The structure of this MOF experiences framework disorder with the two extreme ordered orientations of the ligand, which are topologically related to the two nets, namely lrk and lrl, both derived from the basic net lrj. Moreover, the activated sample, ROD-8a, shows selective gas adsorption of CO2 over N2, CO2 over CH4 and CH4 over N2 at room temperature, estimated by the Ideal Adsorbed Solution Theory (IAST).
    CrystEngComm 01/2014; 16(28):6291. DOI:10.1039/c4ce00279b · 3.86 Impact Factor
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    ABSTRACT: The limited selection of immunosuppressants in the clinic hampers the efficient management of immune disorders such as rejections after organ transplantations. However, the search for new immunosuppressive compounds remains random and creates inevitably financial and laborious wastes. Herein, we present an immunity-inspired discovery strategy that rationally allows an efficient identification of immunosuppressive compounds from the endophyte culture, as exemplified by the new peptide trichomide A. This compound exerts its immunosuppressive action more selectively than cyclosporin A. It was found that trichomide A decreases the expression of Bcl-2, increases the expression of Bax, and has a small or negligible effect on the expressions of p-Akt, CD25, and CD69. Our study strengthens the idea that the cross-kingdom similarity in immunity among living things could provide a shorter route towards the identification of natural products valuable for the development of new immunosuppressants.
    Chemistry - An Asian Journal 12/2013; 8(12). DOI:10.1002/asia.201300734 · 3.94 Impact Factor
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    ABSTRACT: A new cerium-adipate metal-organic framework [Ce(C6H8O4)(H2O)(2)(NO3)] was grown by simple gel diffusion technique at room temperature. The compound possesses a two dimensional network structure constructed from edge sharing CeO6(H2O)(2)(NO3) polyhedron. The adjacent polyhedrons are connected by the carboxylate ligand forming the 20 framework with bullet shaped channels running parallel to c axis. Thermal decomposition of the compound takes place in four steps and CeO2 is obtained as the final product. UV-visible spectra, solid state photoluminescence, and magnetic susceptibility measurements were also carried out at room temperature.
    Inorganic Chemistry Communications 09/2013; 35:140-143. DOI:10.1016/j.inoche.2013.06.003 · 2.06 Impact Factor
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    ABSTRACT: In the title compound, C29H21ClN2O, there is a twist in the bridging prop-2-en-1-one group [C=C-C=O torsion angle = 22.7 (2)°]. The quinolinyl residues form a dihedral angle of 86.92 (4)°, indicating an almost perpendicular relationship. In the crystal, supra-molecular layers in the bc plane are stabilized by C-H⋯π and π-π inter-actions [centroid-centroid distance = 3.4947 (7) Å].
    Acta Crystallographica Section E Structure Reports Online 08/2013; 69(Pt 8):o1318. DOI:10.1107/S1600536813020229 · 0.35 Impact Factor
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    ABSTRACT: In the mol-ecule of the title compound, C24H19ClN2O, the terminal quinolinyl residues are close to perpendicular to each other [dihedral angle 83.72 (4)°]. The quinolinyl residues are connected by and inclined to the prop-2-en-1-one bridge, with the Car-Car-C-C (ar = aromatic) torsion angles being 71.01 (17) and 20.6 (2)°. The crystal structure features phen-yl-carbonyl C-H⋯O inter-actions and π-π inter-actions between centrosymmetrically related quinolinyl residues [3.5341 (10) and 3.8719 (9) Å], which together lead to a three-dimensional architecture.
    Acta Crystallographica Section E Structure Reports Online 08/2013; 69(Pt 8):o1275. DOI:10.1107/S1600536813019405 · 0.35 Impact Factor
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    ABSTRACT: Two Cd(ii)-organic frameworks based on 5-iodoisophthalate (IIP(2-)), {[Cd(IIP)(bte)(H2O)]·H2O}n () and [Cd(IIP)(bpp)(H2O)]n (), were obtained either at an ambient temperature or under solvothermal conditions at 120 °C in the presence of 1,4-bis(1,2,4-triazol-1-yl)ethane (bte) and 1,3-bis(4-pyridyl)propane (bpp) as auxiliary ligands, respectively. is a novel discrete single-walled Cd(ii)-organic tube (SWCOT) which further extends into a 3D supramolecular interdigitated microporous columnar architecture supported by C-II halogen bonds and hydrogen bonds, while exhibits an interesting two-fold interpenetrated 3D diamond network architecture. When the auxiliary ligands bte or bpp were replaced by a longer spacer ligand with more flexibility, 1,4-bis(triazol-1-ylmethyl)benzene (bbtz), the unique discrete single-walled Cd(ii)-organic nanotube (SWCONT), {[Cd(IIP)(bbtz)(H2O)]·H2O}n (), which further extends into a 3D supramolecular microporous framework supported by face-to-face ππ stacking interactions and hydrogen bonds, was generated at room temperature. Under solvothermal conditions at 120 °C, an interesting two-fold 2D "embracing" (4,4) topological network, [Cd(IIP)(bbtz)(H2O)] (), which further extends into a two-fold 3D "embracing" supramolecular framework through O-HO hydrogen bonds, is obtained. loses crystallinity in air, leading to the formation of [Cd(IIP)(bbtz)]·0.5H2O () evidenced by elemental analysis, thermogravimetric analysis (TGA) and powder X-ray diffraction (PXRD). Remarkably, in situ rapid and reversible dehydration-rehydration in static air occurs in , indicating their potential applications as water absorbent and sensing materials. Dehydrated and show selective gas adsorption of CO2 over N2 and dehydrated can adsorb methanol and ethanol vapors strongly. These compounds exhibit blue fluorescence in the solid state.
    Dalton Transactions 07/2013; 42(34). DOI:10.1039/c3dt51118a · 4.10 Impact Factor
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    ABSTRACT: A new organic-lanthanide framework [TbL1.5(H2O)2]·H2O () [H2L = 5-(3'-carboxylphenyl)nicotinic acid] was synthesized. Its structure was determined by single crystal X-ray diffraction. The complex was characterized by PXRD, FT-IR, fluorescence as well as TGA, and features a 3D framework with a 1D channel and exhibits exceptionally high thermal stability up to 440 °C in air. Furthermore, it displays highly sensitive and selective luminescence quenching to Hg(2+) in aqueous solution. The result of a reversible sensing experiment showed complex could be reusable at least 5 times.
    Photochemical and Photobiological Sciences 06/2013; 12(9). DOI:10.1039/c3pp50105a · 2.94 Impact Factor
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    ABSTRACT: In the title compound, C13H19N3S, the methyl-amine substituent is coplanar with the thia-diazole ring to which it is attached [C-N-C-S torsion angle = 175.9 (2)°] and the amine H atom is syn to the thia-diazole S atom. Supra-molecular chains along [101], sustained by N-H⋯N hydrogen bonding, feature in the crystal packing.
    Acta Crystallographica Section E Structure Reports Online 05/2013; 69(Pt 5):o683. DOI:10.1107/S1600536813009033 · 0.35 Impact Factor
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    ABSTRACT: In the title compound, C13H11N3S2, the triazole and thio-phene rings are coplanar [dihedral angle = 6.22 (13)°]. By contrast, the phenyl ring is perpendicular to the triazole ring [dihedral angle = 85.58 (13)°], so that the mol-ecule has an L-shape. The thio-phene S atom is syn with the ring imine N atom. In the crystal, eight-membered {⋯HNCS}2 synthons form between centrosymmetrically related mol-ecules, leading to dimeric aggregates that are connected into a supra-molecular layer parallel to (101) by π-π inter-actions between centrosymmetrically related triazole rings [centroid-centroid distance = 3.6091 (15) Å] and C-H⋯π inter-actions.
    Acta Crystallographica Section E Structure Reports Online 05/2013; 69(Pt 5):o697. DOI:10.1107/S1600536813009501 · 0.35 Impact Factor
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    ABSTRACT: The title compound, C10H5FN2, is a monoclinic (P21/c) polymorph of the previously reported triclinic (P-1) form [Anti-pin et al. (2003 ▶). J. Mol. Struct. 650, 1-20]. The 13 non-H atoms in the title polymorph are almost coplanar (r.m.s. deviation = 0.020 Å); a small twist between the fluoro-benzene and dinitrile groups [C-C-C-C torsion angle = 175.49 (16)°] is evident in the triclinic polymorph. In the crystal, C-H⋯N inter-actions lead to supra-molecular layers parallel to (-101); these are connected by C-F⋯π inter-actions.
    Acta Crystallographica Section E Structure Reports Online 04/2013; 69(Pt 4):o515. DOI:10.1107/S1600536813006235 · 0.35 Impact Factor
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    ABSTRACT: The title compound, C21H15FN2O2, features an approximately planar 1H-benzo[f]chromene fused-ring system (r.m.s. deviation for the 14 non-H atoms = 0.052 Å), with the fluoro-benzene ring being almost perpendicular to this [dihedral angle = 85.30 (7) °]. The furan ring has a flattened half-chair conformation, with the methine C atom deviating by 0.132 (2) Å from the plane of the remaining atoms (r.m.s. deviation = 0.0107 Å). In the crystal, inversion dimers are formed via pairs of amine-cyano N-H⋯N hydrogen bonds. The dimers are connected into a three-dimensional architecture by C-H⋯N(cyano), C-H⋯π and π-π [inter-centroid distance = 3.6671 (10) Å] inter-actions.
    Acta Crystallographica Section E Structure Reports Online 04/2013; 69(Pt 4):o476-7. · 0.35 Impact Factor
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    ABSTRACT: The asymmetric unit of the title compound, C19H12ClN3O, contains two mol-ecules with similar conformations. The 14 non-H atoms comprising the 4H-chromeno[8,7-b]pyridine residue are essentially coplanar (r.m.s. deviations = 0.037 and 0.042 Å for the two mol-ecules) and the main difference between them is seen in the twist about the bond linking the main residue to the attached chloro-benzene rings [dihedral angles = 79.01 (12) and 76.22 (11)° for the two mol-ecules]. Zigzag supra-molecular chains along the a-axis direction mediated by amino-pyridine N-H⋯N hydrogen bonds feature in the crystal packing; these are connected into a three-dimensional architecture by C-H⋯π inter-actions and Cl⋯Cl contacts [Cl⋯Cl = 3.3896 (14) Å].
    Acta Crystallographica Section E Structure Reports Online 04/2013; 69(Pt 4):o462-3. DOI:10.1107/S1600536813005217 · 0.35 Impact Factor
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    ABSTRACT: via one-pot three-component condensation of acetylacetone, malononitrile, and different amines in the presence of N-hydroxybenzamide or p-toluenesulfonic acid
    ChemInform 03/2013; 44(11). DOI:10.1002/chin.201311155

Publication Stats

952 Citations
305.90 Total Impact Points

Institutions

  • 2011–2014
    • King Abdulaziz University
      • Department of Chemistry
      Djidda, Makkah, Saudi Arabia
  • 2013
    • Yangzhou University
      Wu-hsien, Jiangsu Sheng, China
  • 2010–2013
    • University of Tehran
      • School of Chemistry
      Teheran, Tehrān, Iran
    • Shahid Beheshti University
      • Department of Chemistry
      Teheran, Tehrān, Iran
  • 1987–2013
    • University of Malaya
      • Department of Chemistry
      Kuala Lumpur, Kuala Lumpur, Malaysia
  • 2012
    • University of Karachi
      • International Center for Chemical and Biological Sciences
      Kurrachee, Sindh, Pakistan
  • 2008
    • Nanjing University
      • School of Life Sciences
      Nan-ching, Jiangsu Sheng, China
  • 2007
    • Shantou University
      • Department of Chemistry
      Swatow, Guangdong, China
  • 2002
    • Sun Yat-Sen University
      • Department of Chemical Engineering
      Guangzhou, Guangdong Sheng, China
  • 2001
    • Xiamen University
      • Department of Biology
      Amoy, Fujian, China
  • 1999
    • University of Pardubice
      • Department of General and Inorganic Chemistry
      Pardubitz, Pardubický, Czech Republic
  • 1992–1994
    • The Chinese University of Hong Kong
      • Department of Chemistry
      Hong Kong, Hong Kong
  • 1991
    • University of Adelaide
      • School of Chemistry and Physics
      Adelaide, South Australia, Australia
  • 1990
    • University of Oklahoma
      • Department of Chemistry and Biochemistry
      Norman, OK, United States
  • 1989
    • University of Western Australia
      • School of Chemistry and Biochemistry
      Perth, Western Australia, Australia