Seik Weng Ng

King Abdulaziz University, Djidda, Makkah, Saudi Arabia

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Publications (817)274.78 Total impact

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    ABSTRACT: The work presents an further investigation on the coordination chemistry of 5-amino-2,4,6-triiodoisophthalic acid (H2ATIBDC) and reveals the significant function of weak interactions in constructing the resultant supramolecular networks. Reactions of H2ATIBDC with the d10 metal ions [Zn(II) and Cd(II)] in the presence of varied N-donor auxiliary imidazole ligands at ambient condition yield three new 1D metal-organic coordination polymers (CPs): {[Cd(ATIBDC)(biim)]·2H2O}n (1), {[Zn(ATIBDC)(biim)]·3H2O}n (2) and [Cd(ATIBDC)(bbi)]n (3) [biim = 2,2’-biimidazole, bbi = 1,1’-(1,4-butanediyl)bis(imidazole)], which are characterized by elemental analysis, IR spectroscopy, thermogravimetry and single crystal X-ray diffraction measurements. Generally, these three complexes display 1D ATIBDC2--bridged coordination arrays. Extended 3D supramolecular network architectures are further constructed through the weak secondary interactions: aromatic stacking, halogen bonding and hydrogen bonding. It should be interesting to emphasize that the C-I…π halogen bonding plays significant role in the supramolecular assembly of 3. An acyclic trimeric water cluster (D3 chain) was observed and discussed in 2. Thermal stabilities of 1, 2 and 3 have been studied. The fluorescent properties of 1, 2 and 3 have been investigated in the solid state. Compounds 1 and 2 show completely reversible dehydration-rehydration behaviors, which reveal that 1 and 2 may possibly be used as water adsorbents.
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    ABSTRACT: Testosterone thiosemicarbazone, L and its nickel (II) complex 1 were synthesized and characterized by using FTIR, CHN, (1)H NMR, and X-ray crystallography. X-ray diffraction study confirmed the formation of L from condensation of testosterone and thiosemicarbazide. Mononuclear complex 1 is coordinated to two Schiff base ligands via two imine nitrogens and two tautomeric thiol sulfurs. The cytotoxicity of both compounds was investigated via MTT assay with cisplatin as positive reference standard. L is more potent towards androgen-dependent LNCaP (prostate) and HCT 116 (colon). On the other hand, complex 1, which is in a distorted square planar environment with L acting as a bidentate NS-donor ligand, is capable of inhibiting the growth of all the cancer cell lines tested, including PC-3 (prostate). It is noteworthy that both compounds are less toxic towards human colon cell CCD-18Co. The intrinsic DNA binding constant (Kb) of both compounds were evaluated via UV-Vis spectrophotometry. Both compounds showed Kb values which are comparable to the reported Kb value of typical classical intercalator such as ethidium bromide. The binding constant of the complex is almost double compared with ligand L. Both compounds were unable to inhibit the action topoisomerase I, which is the common target in cancer treatment (especially colon cancer). This suggest a topoisomerase I independent-cell death mechanism. Copyright © 2015 Elsevier B.V. All rights reserved.
    Spectrochimica Acta Part A Molecular and Biomolecular Spectroscopy 06/2015; 150:360-372. DOI:10.1016/j.saa.2015.05.095 · 2.13 Impact Factor
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    ABSTRACT: Herein, two stable lead(II) molecular-bowl-based metal-organic frameworks and their micro- and nanosized forms with open metal sites were presented. These materials could act as Lewis acid catalysts to cyanosilylation reaction. Moreover, the catalytic performances are size-dependent, with the catalyst with nanosized form being 1 order of magnitude more efficient than those with micro- and millisized forms.
    Inorganic Chemistry 04/2015; 54(8). DOI:10.1021/acs.inorgchem.5b00185 · 4.79 Impact Factor
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    ABSTRACT: A new tin complex, [µ-(4-bpdb){Me2Sn(cupf)2}2] (1), was prepared by reacting dimethyltin(IV) dichloride, with 1,4-bis(4-pyridyl)-2,3-diaza-1,3-butadiene (4-bpdb) and cupferron in a fast and facile process. The complex was fully characterized based on its 1H and 13C NMR, IR, and UV spectra and elemental analysis. The nanostructure of the prepared compound was synthesized by the sonochemical method. The new nanostructure was characterized by scanning electron microscopy (SEM), X-ray powder diffraction (XRD), IR spectroscopy and elemental analysis. Thermal stability of single crystalline and nanosize samples of the prepared compound was studied by thermal gravimetric and differential thermal analysis. The prepared complexes, as bulk and as nanoparticles, were utilized as a precursor for preparation of SnO2 nanoparticles by direct thermal decomposition at 600 °C in air. The morphology and size of the SnO2 nanoparticles were determined by scanning electron microscopy, XRD and IR spectroscopy and the results showed that particle size of the SnO2 nanoparticle depend on the initial particles size of 1. Photoluminescence properties of the nanostructured and crystalline bulk of the prepared complex and SnO2 nanoparticles core of them were investigated.
    Journal of Inorganic and Organometallic Polymers and Materials 01/2015; DOI:10.1007/s10904-015-0222-5 · 1.08 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: Two isostructural one-dimensional lanthanide coordination polymers, with the general formula {[Ln(aip)(H2O)5]·0.5(bdc)·3H2O}n [Ln = Eu (1), Tb (2); H2aip = 5-aminoisophthalic acid, H2bdc = 1,4-benzenedicarboxylic acid], have been synthesized by a diffusion technique at room temperature. Their structures were identified by X-ray diffraction. Complex 2 exhibits green emission, corresponding to the 5D4 → 7FJ (J = 6-3) transitions of the Tb3+ ion. Significantly, when 2 was immersed in different organic solvents, it had a unique response to methanol compared to other solvents. Furthermore, 2 displayed highly sensitive and selective luminescence quenching to methanol with the ignorable interference of other small-molecule organics. This makes it a potential luminescence sensor for actual application in recognizing methanol.
    RSC Advances 01/2014; 4(27):14035. DOI:10.1039/c4ra00745j · 3.71 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: 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: 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: dithiocarbamates, R 3 PAu[SC(=S)N(iPr)CH 2 CH 2 OH] for R = Ph, Cy and Et: Role of phosphane-bound R substituents upon in vitro cytotoxicity against MCF-7R breast cancer cells and cell death pathways, European Journal of Medicinal Chemistry (2013), doi: 10.1016/j.ejmech.2013.06.038. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
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    ABSTRACT: In the title compound, C18H18O4, the planes of the benzene rings are twisted by 81.60 (5)°. In the crystal, weak C-H⋯O hydrogen bonds link the mol-ecules into supra-molecular chains extending along the a axis.
    Acta Crystallographica Section E Structure Reports Online 06/2013; 69(Pt 6):o819. DOI:10.1107/S1600536813011458 · 0.35 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: In the title compound, C21H15FN2O2, the furan ring has a flattened half-chair conformation [the methine C atom lies 0.136 (2) Å above the C5 plane which has an r.m.s. deviation of 0.0229 Å]. Overall, the 1H-benzo[f]chromene fused-ring system approximates a plane (r.m.s. deviation of the 14 non-H atoms = 0.049 Å). The fluoro-benzene ring is almost perpendicular to this plane [dihedral angle = 89.58 (8)°]. Zigzag supra-molecular tapes along the b axis are the most notable feature of the crystal packing. This arises through an alternating sequence of 12-membered {⋯HNC3N}2 and eight-membered {⋯HNCO}2 synthons. These are connected into a three-dimensional architecture by π-π [inter-centroid distance for centrosymmetrically related fluoro-benzene rings = 3.5181 (10) Å] and C-H⋯π inter-actions.
    Acta Crystallographica Section E Structure Reports Online 04/2013; 69(Pt 4):o478-9. DOI:10.1107/S1600536813005473 · 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

Publication Stats

976 Citations
274.78 Total Impact Points

Institutions

  • 2011–2015
    • King Abdulaziz University
      • Department of Chemistry
      Djidda, Makkah, Saudi Arabia
  • 1987–2015
    • University of Malaya
      • Department of Chemistry
      Kuala Lumpor, Kuala Lumpur, Malaysia
  • 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
  • 2006–2007
    • Heilongjiang University
      Charbin, Heilongjiang Sheng, China
    • Guangxi Normal University
      • Department of Chemistry
      Pakhoi, Guangxi Zhuangzu Zizhiqu, China
  • 2001–2007
    • Xiamen University
      • • Department of Chemistry
      • • Department of Biology
      Amoy, Fujian, China
  • 2002
    • Sun Yat-Sen University
      • Department of Chemical Engineering
      Guangzhou, Guangdong Sheng, China
  • 1999
    • University of Pardubice
      • Department of General and Inorganic Chemistry
      Pardubitz, Pardubický, Czech Republic