Firasat Hussain

A Gadolinium-Bridged Polytungstoarsenate(III) Nanocluster: [Gd8As12W124O432(H2O)22]60−†

This work was supported by the Swiss National Science Foundation (SNSF Professorship PP002-114711/1) and the University of Zurich. We thank Dr. B. Spingler, Institute of Inorganic Chemistry, University of Zurich, for helpful crystallographic discussions, and S. Weyeneth, Physics Institute, University of Zurich, for assistance with the magnetic measurements. We are grateful to Prof. A. Stemmer and R. Enning, Micro and Nano Science Platform, ETH Zurich, for help with AFM measurements. We thank Dr. R. Wepf, Electron Microscopy ETH Zurich, EMEZ, for Cryo-SEM investigations. The support of the Center for Microscopy and Image Analysis, University of Zurich, is gratefully acknowledged, and we thank Y. Zhou, UZH, for help with SEM measurements.

Self-assembly of dilacunary building blocks into high-nuclear [Ln16As16W164O576(OH)8(H2O)42]80− (Ln = EuIII, GdIII, TbIII, DyIII, and HoIII) polyoxotungstates

A new family of [Ln16As16W164O576(OH)8(H2O)42]80− (Ln = EuIII, GdIII, TbIII, DyIII, and HoIII) nanoclusters has been synthesized from a self-assembly process in solution. The novel macroanion is constituted of two identical sub-units with the formula [Gd8As8W82O288(OH)4(H2O)21]40− and it was obtained from the versatile building block [As2W19O67(H2O)]14− in combination with mid to late lanthanoid cations. All compounds have been structurally characterized and the magnetic properties of the Gd-containing member of the series have been investigated. The novel macroanion represents the largest polyoxotungstate reported to date and the influence of the templating cations on the molecular architecture is discussed. Furthermore, the spectrum of lanthanide linkers for the construction of large polyoxotungstates has been amplified in the present approach.

Lanthanoid-Containing Open Wells–Dawson Silicotungstates: Synthesis, Crystal Structures, and Properties

Five novel lanthanoid-containing silicotungstates with polymeric crystal structures [Ln(2)(H(2)O)(7)Si(2)W(18)O(66)](n)(10n-) [Ln = Gd(III) (Gd-1 and Gd-2), Tb(III), Ho(III)] and [Dy(2)(H(2)O)(6.5)(C(2)H(4)O(2))(0.5)Si(2)W(18)O(66)](n)(10n-) were obtained from the one-step reaction of Na(10)[SiW(9)O(34)]·nH(2)O with Ln(NO(3))(3)·nH(2)O in a sodium acetate buffer. The compounds were characterized by single-crystal X-ray diffraction and a wide range of analytical methods, including FT-IR, UV/vis, and photoluminescence spectroscopy as well as electrochemistry and thermogravimetric analysis. This new polyoxotungstate series is the first example of lanthanoids embedded in the open Wells-Dawson silicotungstate anion [α-Si(2)W(18)O(66)](16-). The lanthanoid-containing Wells-Dawson-type polyoxoanions [Ln(2)(H(2)O)(7)Si(2)W(18)O(66)](10-) [Ln = Gd(III) (Gd-1 and Gd-2), Tb(III), Ho(III)] and [Dy(2)(H(2)O)(6.5)(C(2)H(4)O(2))(0.5)Si(2)W(18)O(66)](10-) are linked by Ln(3+) cations to form 3D architectures for Gd-1 or 2D frameworks for the isostructural compounds Tb-2, Dy-2, Ho-2, and Gd-2. The structure-directing influence of the lanthanoid cation on the local structure of the dimeric building blocks and on the crystal packing motifs is investigated in detail. The photoluminescence properties of Tb-2 and Dy-2 were investigated at room temperature, and Ho-2 exhibits an interesting photochromic behavior. The magnetic susceptibility of Gd-1 and Gd-2 was studied in the temperature range between 2 and 300 K for its effective magnetic moment.

Caesium-templated lanthanoid-containing polyoxotungstates

A family of novel lanthanoid-containing polytungstoarsenate(iii) polyanions with interesting structural features has been isolated: six lacunary {alpha-AsW(9)O(33)} building blocks comprising unusual pyramidal WO(5) units are templated by a caesium cation in a central cavity of the structure.

Titanium substituted hexagonal mesoporous aluminophosphates: Highly efficient and selective heterogeneous catalysts for the oxidation of phenols at room temperature

Abstract A remarkable para-selectivity was achieved, for the first time, for the oxidation of phenol over novel titanium substituted hexagonal mesoporous aluminophosphate molecular sieves at room temperature, and that the catalysts also showed excellent activity for alkyl substituted phenols.

Synthesis, Characterization, and Catalytic Properties of Chromium-Containing Hexagonal Mesoporous Aluminophosphate Molecular Sieves

Chromium-containing hexagonal mesoporous aluminophosphate molecular sieve materials were synthesized, characterized and evaluated for the oxidation of cyclohexane under mild conditions. The catalysts showed remarkable activity for the chosen reaction with very high substrate conversion and excellent product selectivity. In addition, recycling studies over the spent catalysts as well as studies on quenched solutions under the reaction conditions indicated no or very meager loss in activity; thus, the materials behaved truly as heterogeneous catalysts. This observation was well supported by ICP-AES analysis of the filtrates obtained from the washed catalysts where no leaching of active chromium species was detected. Furthermore, the reaction carried out using these filtrates confirmed the absence of active metal ions as it exhibited only a marginal activity.

Synthesis and evaluation of some new pyrazoline substituted benzenesulfonylureas as potential antiproliferative agents.

Twenty six new pyrazoline substituted benzenesulfonylureas (2a-z) were synthesized and tested for in vitro anticancer activity. Fourteen derivatives (2i, 2k-2p, 2r, 2s-2x) were screened for their antiproliferative activity towards 60 human cancer cell lines by the National Cancer Institute (USA). Among them four compounds (2i, 2n, 2v and 2x) exhibited significant growth inhibition and further screened at 10-fold dilutions of five different concentrations (0.01, 0.1, 1, 10 and 100 μM). The compounds 2i, 2n, 2v and 2x showed effective growth inhibition (GI50 MID) values of 2.62, 3.93, 3.33, 3.74 μM respectively beside cytostatic activity TGI (MG-MID) values of 8.42, 65.80, 24.00 and 36.06 μM respectively. The compound 2i displayed remarkable antiproliferative activity in 8 different cell lines with GI50 less than 2 μM. Compounds 2n, 2v and 2x also displayed good antiproliferative activity against 11, 18 and 14 different cell lines respectively with GI50 less than 3 μM.

Luminescent Dirhenium(I)-Double-Heterostranded Helicate and Mesocate

The semirigid ligands 1,4-bis(2-(2-hydroxyphenyl)benzimidazol-1-ylmethyl)benzene (H2-pBC) and 1,3-bis(2-(2-hydroxyphenyl)benzimidazol-1-ylmethyl)-2,4,6-trimethylbenzene (H2-mBC), containing two hydroxyphenylbenzimidazolyl units as bis-chelating (or bis(bidentate)) N∩OH donor, were synthesized and were used to assemble neutral, luminescent heteroleptic, unsaturated double-hetero-stranded, rhenium(I)-based helicate (1) and mesocate (2) with the flexible bis(monodentate) nitrogen donor (1,4-bis(benzimidazol-1-ylmethyl)benzene/1,3-bis(benzimidazol-1-ylmethyl)benzene), and Re2(CO)10. The photophysical properties of the complexes were studied. Both complexes 1 and 2 exhibit dual emissions in both solution and solid state. In solution, these complexes show both fluorescence and phosphorescence. Complex 1 undergoes a predominantly ligand-centered oxidation, resulting in the generation of phenoxyl radicals.

Lanthano-phosphotungstate: A water soluble and reusable catalyst for oxidation of alcohols using H2O2 as an oxidant

A series of water soluble lanthano-phosphotungstate K11[Ln(PW11O39)2]·xH2O [Ln = Pr(III), Nd(III), Eu(III), Gd(III), Tb(III), Dy(III), Ho(III), Er(III), Tm(III) and Yb(III)] catalysts were synthesized. These catalysts (0.24 mol%) were screened for oxidation of primary and secondary alcohols using H2O2 as an oxidant in water. The Pr-POM catalyst retained its activity after being recycled and reused upto five cycles.

Dimeric complexes of rare-earth substituted Keggin-type silicotungstates: syntheses, crystal structure and solid state properties

A series of rare-earth substituted dimeric complexes of Keggin-type silicotungstates: [{Ln(α-SiW11O39)(H2O)}2(μ-CH3COO)2]12− [Ln = EuIII (Eu-1), GdIII (Gd-2), TbIII (Tb-3), DyIII (Dy-4), HoIII (Ho-5), ErIII (Er-6) and TmIII (Tm-7)] and [Ln(α-SiW11O39)2]13− [Ln = PrIII (Pr-8), NdIII (Nd-9), SmIII (Sm-10)] were synthesized by a single step reaction of Na10[α-SiW9O34]·16H2O with Ln(NO3)3·nH2O in potassium acetate buffer at pH 4.5. All these compounds were structurally characterized by single-crystal X-ray diffraction, and other analytical techniques including FT-IR, ICP-AES, UV/vis, photoluminescence spectroscopy, thermogravimetric analysis, 13C and 1H NMR spectroscopy and vibrating sample magnetometry (VSM). The single-crystal X-ray diffraction and FT-IR studies suggest that the compounds Na4K8[{Ln(α-SiW11O39)(H2O)}2(μ-CH3COO)2]·xH2O (Ln = Eu − Tm) (Eu-1a–Tm-7a), and K6Na7[Ln(SiW11O39)2]·xH2O (Ln = Pr, Nd, Sm) (Pr-8a–Sm-10a) are isostructural. The photoluminescence properties of Eu-1a, Tb-3a, Dy-4a and Sm-10a were studied at room temperature. VSM studies of Gd-2a, Tb-3a, Dy-4a, Ho-5a, Er-6a and Tm-7a were carried out at room temperature, and they showed paramagnetic behaviour.