Seik Weng Ng

Al-Azhar University, Cairo, Muhafazat al Qahirah, Egypt

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Publications (792)199.03 Total impact

  • [Show abstract] [Hide abstract]
    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; · 3.81 Impact Factor
  • Seng Lim Tan, Seik Weng Ng
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    ABSTRACT: The crystal structures of C7H8FN3, C20H25Br, [Cu(H2O)2(C6H12N4)(C7H3N2O6)2]·2H2O, [SnCl(H2O)(C6H5)3(C10H8N2)]2 and [Pb(NO3)2(C3H9N3S)] refined on numerically absorption-corrected reflections to low R values although the dimensions of the crystals exceeded the diameter of the X-ray beam collimator. The R values for the organic and copper compounds were not significantly different when smaller specimens cut from the large crystals were used. For the tin complex, a large peak persisted in the difference map for all sizes, and for the lead complex, the difference Fourier map was more diffuse the smaller the specimen.
    Journal of Applied Crystallography 08/2014; 47(4). · 3.34 Impact Factor
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    ABSTRACT: We observed an unusual aggregation process with stimuli-responsive structural dynamics and optical changes attributed to the formation of a sandwich-like Au3-Ag-Au3 cluster, which can be synthesized through both solution and mechanochemical methods. Unlike many other heteronuclear gold-silver clusters, the affinity of the cyclic Au3 complex and AgI ion is solely bound by unsupported Au-Ag metallophilic attraction. The assembly/disassembly behavior, further forming nanodot aggregates, is controllable by adjusting the concentration of solution. In the solid state, the insertion of AgI ion can be implemented through mechanochemical approach in a reversible manner, accompanied with visible color change and luminochromism. Furthermore, an unconventional solid-liquid extraction is demonstrated, showing the uniqueness of this labile Au-Ag metallophilicity and hinting at the possibility of manipulating a chemical process through a heterogeneous route.
    Journal of the American Chemical Society 06/2014; · 10.68 Impact Factor
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    ABSTRACT: Evidence for C-Hπ(CuClHNCS) interactions, i.e. C-Hπ(quasi-chelate ring) where a six-membered quasi-chelate ring is closed by an N-HCl hydrogen bond, is presented based on crystal structure analyses of (Ph3P)2Cu[ROC([double bond, length as m-dash]S)N(H)Ph]Cl. Similar intramolecular interactions are identified in related literature structures. Calculations suggest that the energy of attraction provided by such interactions approximates 3.5 kcal mol(-1).
    Chemical Communications 04/2014; · 6.38 Impact Factor
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    ABSTRACT: A novel three-dimensional lead(II) coordination polymer, [Pb3(dmp)2Cl6]n, was prepared by reacting lead(II) chloride with 2,9-dimethyl-1,10-phenanthroline ina fast and facile process. The complex was fully characterized on the basis of its1H and13C NMR, IR, and UVspectra and elemental and thermal analyses. The molecular structure of the compound was determined by singlecrystal X-ray diffraction and its photoluminescence properties were investigated. The single-crystal X-ray data showed that the compound crystallized in the triclinic crystal system in the space group Pı ¯ ¯. The complex was utilized as a precursor for the preparation of PbO nanoparticles by direct thermal decomposition at 600�C in air. The prepared PbO nanoparticles were characterized by scanning electron microscopy and powder X-ray diffraction and a band gap of ca. 3.76 eV was determined from the UV–Vis absorption spectrum. A strong blue emission, centered at 466 nm, was observed in the photoluminescence spectrum of PbO nanoparticles and that related to oxygen vacancies in PbO.
    Monatshefte fuer Chemie/Chemical Monthly 04/2014; 145(8):1277. · 1.63 Impact Factor
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    ABSTRACT: A facile, efficient and environmentally friendly approach has been developed for the diversity oriented synthesis of trifunctional coumarin-amide-triazole containing compounds. A wide variety of pharmacologically significant and structurally interesting compounds were synthesized via a one-pot, six-component, tandem Knoevenagel/Ugi/click reaction sequence from readily available starting materials in ethanol at room temperature in excellent overall yields. Substituents could be independently varied at five different positions.
    ACS combinatorial science. 02/2014;
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    ABSTRACT: 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.
    Molecules 01/2014; 19(2):1990-2003. · 2.43 Impact Factor
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    ABSTRACT: Four novel samarium complexes were prepared by reacting samarium(III) nitrate with 8-hydroxyquinoline, 2-methyl-8-hydroxyquinoline, and 1,10-phenanthroline and utilized as emitting materials in the electroluminescence device. All complexes were characterized by elemental analysis, infrared, UV–vis and 1H NMR spectroscopes and the molecular structure of a representative complex, [Sm2(Me-HQ)4(NO3)6] (1), was determined by single-crystal X-ray diffraction. Utilization of a π-conjugated (phenanthroline) ligand as a second ligand in the structure of the samarium complexes resulted in red shifts in both absorption and fluorescence spectra of complexes and moderately enhanced the photoluminescence intensity and the fluorescence quantum yield. The maximum emission peaks showed that a good correlation exists between the nature of the substituent group on the 8-hydroxyquinoline and the addition of the π-conjugated ligand in the structure of samarium complexes and emission wavelength. Devices with samarium(III) complexes with structure of ITO/PEDOT:PSS (90 nm)/PVK:PBD:Sm(III) complexes (75 nm)/Al (180 nm) were fabricated. In the electroluminescence (EL) spectra of the devices, a strong ligand-centered emission and narrow bands arising from the 4G5/2→6HJ transitions (J=7/2, 9/2, and 11/2) of the samarium ion were observed for the complexes. The electroluminescent spectra of the samarium complexes were red-shifted as compared with the PVK:PBD blend. We believe that the electroluminescence performance of OLED devices based on samarium complexes relies on overlaps between the absorption of the samarium compounds and the emission of PVK:PBD. This revealed that it is possible to evaluate the electroluminescence performance of the samarium compounds-doped OLED devices based on the emission of PVK:PBD and the absorption of the dopants.
    Journal of Luminescence. 01/2014; 156:219–228.
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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 09/2013; · 4.57 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; · 3.81 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; · 2.92 Impact Factor
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    ABSTRACT: Needles of [{Cd[S2CN(iPr)CH2CH2OH]2}3·MeCN]∞ (2) were harvested from a dry acetonitrile solution of Cd[S2CN(iPr)CH2CH2OH]2 after one or two days and proved to be a coordination polymer in which all dithiocarbamate ligands are μ2,κ2-tridentate, bridging two cadmium atoms and simultaneously chelating one of these. If the same solution was allowed to stand for at least several days, 2 is replaced by blocks comprising a supramolecular isomer of 2, dimeric 1, with formula {Cd[S2CN(iPr)CH2CH2OH]2}2·2H2O·2MeCN, and two ligands coordinating μ2,κ2 as in 2 and the other two purely κ2-chelating. The time dependency correlates with the pivotal role of water in driving the conversion of “chain” 2 to “ball” 1; crystals of 2 could not be isolated from “wet” acetonitrile. When each of 1 and 2 are dissolved in solution, they exhibit comparable spectroscopic attributes (1H, 13C, and 113Cd NMR and UV/vis), indicating the solution structures are the same. Both 1 and 2 are luminescent in the solid state with 1 being significantly brighter than 2. Greenockite CdS nanoparticles are generated by the thermal decomposition of both 1 and 2.
    Crystal Growth & Design 06/2013; 13(7):3046–3056. · 4.69 Impact Factor
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    ABSTRACT: A library of some new fluorescent chromenopyrimidine derivatives has been synthesized by new approaches. Water- promoted and one-pot reaction can produce new dialkylylamino)-5H-chromeno[2,3-d]pyrimidin-2-yl) phenols. These compounds can also be produced using domino reaction. Two parallel methods are compared. Novel N-alkyl-N-phenyl-5H-chromeno [2, 3-d]- pyrimidin-4-amines and 4-alkoxy-5H-chromeno[2, 3-d] pyrimidines are synthesized by Lewis acid catalyzed reactions. The fluorescence emission intensity of the four compounds from each of libraries after excitation in 290 nm is measured. Compound 2-(4,5-bis(N-methyl-N-phenylamino)-5H-chromeno[2,3-d]pyrimidin-2-yl)phenol was isolated as a by-product. The details of an interesting exchangeable intramolecular H- bonding of two of the new compounds are reported by X-ray analysis data.
    ACS combinatorial science. 04/2013; 15:240-246.
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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. · 0.35 Impact Factor
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    ABSTRACT: In the title compound, C21H15BrN2O2, the 14 non-H atoms of the 4H-benzo[h]chromene fused-ring system are approximately coplanar (r.m.s. deviation = 0.129 Å). Within this system, the 4H-pyran ring adopts a flattened half-chair conformation with the methine C atom lying 0.281 (4) Å above the plane of the remaining atoms (r.m.s. deviation = 0.0446 Å). The bromo-benzene ring is almost perpendicular to the fused-ring system [dihedral angle = 85.34 (13)°]. In the crystal, supra-molecular layers parallel to (101) are sustained by amine-cyano N-H⋯N and amine-meth-oxy N-H⋯O hydrogen bonds. The layers stack with inter-actions of the type (bromo-benzene)C-H⋯π(outer-C6 ring of the fused-ring system) connecting them.
    Acta Crystallographica Section E Structure Reports Online 04/2013; 69(Pt 4):o480-1. · 0.35 Impact Factor
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    ABSTRACT: In the title compound, CHNOS, the quinoline residue (r.m.s. deviation = 0.018 Å) is essentially orthogonal to both the phenyl [dihedral angle = 88.95 (8)°] and 2-thienyl [81.98 (9)°] rings. The carbonyl O atom lies to one side of the quinoline plane, the carbonyl C atom is almost coplanar and the remaining atoms of the chalcone residue lies to the other side, so that overall the mol-ecule has an L-shape. The conformation about the ethyl-ene bond [1.340 (2) Å] is . In the crystal, a supra-molecular chain with the shape of a square rod aligned along the -axis direction is sustained by C-H⋯π inter-actions, the π-systems being the heterocyclic rings.
    Acta Crystallographica Section E Structure Reports Online 03/2013; 69(Pt 3):o426-7. · 0.35 Impact Factor
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    ABSTRACT: In the title compound, CHNS, comprising fused six-, six- and five-membered rings, the mol-ecule is close to being planar (r.m.s. deviation of the non-H atoms = 0.041 Å). The S-bound methyl group is folded away from the single N atom of the triazole ring and the NH group of the six-membered ring, allowing for the formation of centrosymmetric eight-membered {⋯HNCN} synthons in the crystal. The resulting inversion dimers are connected into supra-molecular stacks aligned along the -axis direction by π-π inter-actions [centroid-centroid distances = 3.6531 (12) and 3.7182 (12) Å].
    Acta Crystallographica Section E Structure Reports Online 03/2013; 69(Pt 3):o434. · 0.35 Impact Factor
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    ABSTRACT: In the title compound, CHBrNO, the pyran ring has a flattened boat conformation with the O and methine C atoms lying to one side of the plane [0.160 (5) and 0.256 (6) Å, respectively] defined by the remaining atoms. Nevertheless, the 4-benzo[]chromene ring system approximates a plane (r.m.s. deviation = 0.116 Å) with the bromo-benzene ring almost perpendicular [dihedral angle = 83.27 (16)°] and the ester group coplanar [C-C-C-O = 3.4 (5)°]; the meth-oxy substituent is also coplanar [C-O-C-C = 174.5 (3)°]. In addition to an intra-molecular N-H⋯O(ester carbon-yl) hydrogen bond, the ester carbonyl O atom also forms an inter-molecular N-H⋯O hydrogen bond with the second amine H atom, generating a zigzag supra-molecular chain along the axis in the crystal packing. The chains are linked into layers in the plane by N-H⋯Br hydrogen bonds, and these layers are consolidated into a three-dimensional architecture by C-H⋯π inter-actions.
    Acta Crystallographica Section E Structure Reports Online 03/2013; 69(Pt 3):o435-6. · 0.35 Impact Factor
  • Seik Weng Ng
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    ABSTRACT: In the title mol-ecule, C15H22O2, there is an intra-molecular hydrogen bond involving the hy-droxy and aldehyde groups and forming an S(6) ring. The mean plane of the non-H atoms of this ring [(H)O-C C-C=O, with a maximum deviation of 0.013 (1) Å] are essentially coplanar with the benzene ring, forming a dihedral angle of 2.29 (8)°.
    Acta Crystallographica Section E Structure Reports Online 01/2013; 69(Pt 9):o1427. · 0.35 Impact Factor

Publication Stats

291 Citations
199.03 Total Impact Points

Institutions

  • 2013
    • Al-Azhar University
      • Department of Chemistry
      Cairo, Muhafazat al Qahirah, Egypt
    • Xi'An Modern Chemistry Research Institute
      Ch’ang-an, Shaanxi, China
    • BITS Pilani, K K Birla Goa
      • Department of Chemistry
      Goa Velha, Goa, India
    • King Khalid University
      Ebha, Minţaqat ‘Asīr, Saudi Arabia
    • King Saud University
      • Department of Pharmaceutical Chemistry
      Riyadh, Mintaqat ar Riyad, Saudi Arabia
  • 2011–2013
    • King Abdulaziz University
      • Department of Chemistry
      Djidda, Makkah, Saudi Arabia
  • 2004–2013
    • University of Malaya
      • Department of Chemistry
      Kuala Lumpur, Kuala Lumpur, Malaysia
  • 2012
    • Heilongjiang University
      • School of Chemistry and Materials Science
      Charbin, Heilongjiang Sheng, China
  • 2002
    • Sun Yat-Sen University
      • Department of Chemical Engineering
      Guangzhou, Guangdong Sheng, China