Faculty of Natural Sciences
Permanent URI for this community
Welcome to the scholarship of the Faculty of Natural Sciences.
The Faculty is developing a reputation as an important centre of research in South Africa. It equips graduates with solid academic and research skills and gives them the ability to succeed in the market place.
Electronic theses and dissertations are available in the Electronic Theses and Dissertations Repository.
News
South African institutions top THE Africa rankings pilot
Times Higher Education creates a top 15 table for Africa’s academies ahead of the inaugural THE Africa Universities Summit on 30-31 July
Browse
Browsing by Author "Abbo, Hanna S."
Now showing 1 - 5 of 5
Results Per Page
Sort Options
Item An efficient inclusion complex based fluorescent sensor for mercury (ii) and its application in live cell imaging(Springer, 2022) Keerthana, Ponmudi; Abbo, Hanna S.; Cherian, Anila RoseThe formation of an inclusion complex between hydroxypropyl-β-cyclodextrin (H-CD) and 4-acetylphenyl-4-(((6- chlorobenzo[d]thiazol-2-yl)-imino)-methyl)-benzoate (L) was investigated by FT-IR, 1 H-NMR, X-ray difraction (XRD), FT-Raman, scanning electron microscope (SEM) techniques in the solid-state, absorption and emission spectroscopy in the liquid state and the virtual state as molecular docking technique. The binding properties of the inclusion complex (H-CD: L) with cations in deionized water was observed via absorbance and photoluminescence (PL) emission spectroscopy. The fuorescence probe (H-CD: L) inclusion complex (IC) was examined for several heavy metal cations, and identifed that the PL emission wavelength of the complex displayed a continuous rise in the fuorescence intensity for Hg2+. A linearity range of 1× 10–8 – 11× 10–8 M and limit of detection value of 2.71×10–10 M was found to be achieved for the detection of Hg2+. This outcome proves that the inclusion complex H-CD: L would be a promising material for the development a solid-state fuorescence probe for detecting Hg2+. It also shows application in real sample analysis and cell imaging.Item A new vanadium (III) complex of 2,6-Bis(3,5-diphenylpyrazol- 1-ylmethyl)pyridine as a catalyst for ethylene polymerization(MDPI, 2013) Abbo, Hanna S.; Titinchi, Salam J.J.The tridentate ligand 2,6-bis(3,5-diphenylpyrazol-1-ylmethyl)pyridine, abbreviated as 2,6-[(3,5-ph2pz-CH2)2-py], a new pyridine-pyrazole derivative, was prepared from 2,6-bis(bromomethyl)pyridine and 3,5-diphenylpyrazole. The ligand was characterized by means of elemental analyses, ATR-IR, 1H- and 13C-NMR spectroscopy and single crystal X-ray crystallography. Using this ligand, a new mononuclear vanadium (III) complex, {2,6-[(3,5-ph2pz)CH2]2py}VCl3 was prepared and characterized by elemental analysis, ATR-IR and HR-MS. The complex was investigated as a catalyst for ethylene polymerization and compared with 2,6-[(3,5-Me2pz)CH2]2py}VCl3 to explore the effect of the substituent on the pyrazolyl rings on ethylene polymerization. High catalytic activity was observed at ambient temperature. After treatment with AlEtCl2, these complexes showed high activity for ethylene polymerization converting ethylene to highly linear polyethylene and affording high molecular weight polymers (up to 1.0 × 106 g/mol) with unimodal molecular weight distributions.Item Oxidation of benzoin catalyzed by oxovanadium (IV) schiff base complexes(Chemistry Central, 2013) Alsalim, Tahseen A.; Hadi, Jabbar S.; Ali, Omar N.; Abbo, Hanna S.; Titinchi, Salam J.J.BACKGROUND: The oxidative transformation of benzoin to benzil has been accomplished by the use of a wide variety of reagents or catalysts and different reaction procedures. The conventional oxidizing agents yielded mainly benzaldehyde or/and benzoic acid and only a trace amount of benzil. The limits of practical utilization of these reagents involves the use of stoichiometric amounts of corrosive acids or toxic metallic reagents, which in turn produce undesirable waste materials and required high reaction temperatures. In recent years, vanadium complexes have attracted much attention for their potential utility as catalysts for various types of reactions. RESULTS: Active and selective catalytic systems of new unsymmetrical oxovanadium(IV) Schiff base complexes for the oxidation of benzoin is reported. The Schiff base ligands are derived between 2-aminoethanol and 2-hydroxy-1- naphthaldehyde (H2L1) or 3-ethoxy salicylaldehyde (H2L3); and 2-aminophenol and 3-ethoxysalicylaldehyde (H2L2) or 2-hydroxy-1-naphthaldehyde (H2L4). The unsymmetrical Schiff bases behave as tridentate dibasic ONO donor ligands. Reaction of these Schiff base ligands with oxovanadyl sulphate afforded the mononuclear oxovanadium(IV) complexes (VIVOLx.H2O), which are characterized by various physico-chemical techniques. The catalytic oxidation activities of these complexes for benzoin were evaluated using H2O2 as an oxidant. The best reaction conditions are obtained by considering the effect of solvent, reaction time and temperature. Under the optimized reaction conditions, VOL4 catalyst showed high conversion (>99%) with excellent selectivity to benzil (~100%) in a shorter reaction time compared to the other catalysts considered. CONCLUSION: Four tridentate ONO type Schiff base ligands were synthesized. Complexation of these ligands with vanadyl(IV) sulphate leads to the formation of new oxovanadium(IV) complexes of type VIVOL.H2O. Elemental analyses and spectral data of the free ligands and their oxovanadium(IV) complexes were found to be in good agreement with their structures, indicating high purity of all the compounds. Oxovanadium complexes were screened for the oxidation of benzoin to benzil using H2O2 as oxidant. The effect of time, solvent and temperature were optimized to obtain maximum yield. The catalytic activity results demonstrate that these catalytic systems are both highly active and selective for the oxidation of benzoin under mild reaction conditions.Item Salicylaldiminato chromium complex supported on chemically modified silica as highly active catalysts for the oxidation of cyclohexene(Elsevier, 2013) Titinchi, Salam J.J.; Abbo, Hanna S.Immobilization of chromium complexes on modified silica support was achieved via two different synthetic routes using 3-aminopropyl triethoxysilane (APTS) as a linking group. The FTIR spectra, elemental and solid-state NMR analyses demonstrated incorporation of amine functional groups on the surface of the APTS-functionalized silica support, which was further confirmed by 29 Si solid-state CP MAS NMR spectroscopy. Oxidation of cyclohexene was carried out over the chromium complex supported on organically modified silica using H2 O2 as an oxidant under various conditions and different atmospheres viz. oxygen, nitrogen and air. The supported catalysts exhibited excellent activity (>94%) after 6 h reaction time under O2 atmosphere using THF as solvent. The catalysts showed high chemoselectivity towards formation 2-cyclohexen-1-ol and 2-cyclohexen-1-one. Activity of the immobilized catalysts remains nearly the same after three consecutive cycles, suggesting the true heterogeneous nature of the catalyst.Item Synthesis and electronic properties of Alkyl- and alkyloxy-cucuminoids(Elsevier, 2013) Alsalim, Tahseen A.; Saeed, Bahjat Ali; Elias, Rita Sabah; Abbo, Hanna S.; Titinchi, Salam J.J.Two series of p‐alkyl‐ and p‐alkoxy‐substituted curcuminoids were synthesized. The validity of the proposed structures was checked on the basis of their high resolution mass spectra as well as NMR, IR and electronic spectra. The spectra were essentially similar for both series. NMR, IR and electronic spectra showed that the compounds exist mainly or exclusively as the enolic tautomer in their solutions. Theoretical study for the electronic spectra was conducted to account for the origins of the electronic transitions that are responsible for the UV‐VIS bands. The theoretical calculations were done at the B3LYP/6‐31G(d) level of theory and predicted that the similarity of the electronic spectra is may be due to the close resemblance of their molecular orbitals.