Prof. Martin O Onani (Chemistry)
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| Position: | Associate professor in Inorganic Chemistry |
| Department: | Department of Chemistry |
| Faculty: | Faculty of Natural Sciences |
| Qualifications: | PhD |
| My publications in this repository | |
| More about me: | here and here |
| Tel: | 021 959 3050 |
| Fax: | 021 959 1400 |
| Email: | monani@uwc.ac.za |
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Item Antimicrobial activities of a novel biflavonoid and other constituents from Rhus natalensis(Academic Journals, 2013) Mwangi, Henry M.; Mabusela, Wilfred T.; Abegaz, Berhanu M.; Martin, Onani O.Phytochemical studies on Rhus natalensis root bark collected from Kenya led to the isolation and identification of a new biflavonoid (3-(1-(2,4-dihydroxyphenyl)-3,3-bis(4-hydroxyphenyl)-1-oxopropan-2- yl)-7-methoxy-4H-chromone-4-one (1), named rhuschromone, in addition to two other known compounds; 2',4'-dihydroxychalcone-(4-O-5''')-4'',2''',4'''-trihydroxychalcone (2) and 3-((Z)-heptadec-13- enyl) benzene-1,2-diol (3). The chemical structures of the isolated compounds were established using spectroscopic techniques including high field nuclear magnetic resonance (NMR). The total extracts and the isolated compounds were tested for their antimicrobial activities against different strains of bacteria.Item Bis(ferrocenylimine)palladium(II) and platinum(II) complexes: synthesis, molecular structures and evaluation as antitumor agents(Elsevier, 2012) Motswainyana, William M.; Onani, Martin O.; Madiehe, Abram M.Compounds (ferrocenyl-2-furylmethyl)imine (L1), (ferrocenyl-2-thiophenemethyl)imine (L2) and (ferrocenyl-2-thiopheneethyl)imine (L3) were synthesized by condensation reactions and obtained in very good yields. Reactions of L1 – L3 with 0.5 equiv of either PdCl2(cod), PdClMe(cod) or K2[PtCl4] gave the new corresponding trans bis(ferrocenylimine)palladium(II) and platinum(II) complexes 1 – 9. The compounds were characterized by elemental analysis, IR, 1H and 13C NMR spectroscopy. The molecular structures of 3 and 6 were determined by single crystal X-ray diffraction analysis. Both structures crystallize in monoclinic P21/n space system. The coordination geometry around the palladium atom in complexes 3 and 6 exhibits a square planar geometry at the palladium atom. Complexes 1, 7 and 9 were evaluated for their cytotoxic activities against human breast (MCF-7) and human ovarian (A2780) cancer cell lines, and they exhibited low cytotoxic activities but comparable to that of cisplatin.Item Imino-quinolyl palladium(II) and platinum(II) complexes: synthesis, characterization, molecular structures and cytotoxic effect(Elsevier, 2013) Motswainyana, William M.; Onani, Martin O.; Madiehe, Abram M.; Saibu, Morounke; Jacobs, Jeroen; van Meervelt, LucImino-quinolyl ligands L1-L5 were synthesized by condensation reactions and obtained in good yields. Reactions of the ligands with either PdCl2(cod) or K2[PtCl4] gave the corresponding palladium(II) and platinum(II) complexes 1-10 also in good yields. All the compounds were characterized by elemental analysis, IR, 1H and 13C NMR spectroscopy. X-ray crystallography was used to confirm the structures of these compounds. Molecular structures of 3 and 5 showed that the ligands coordinate to the metal centre through the two nitrogen atoms, generating a distorted square planar geometry around the palladium atom. The new complexes exhibited remarkable cytotoxic activities against MCF-7 and HT-29 cancer cell lines.Item New phenylene bridged binuclear bis (imino-quinolyl) palladium(II) complexes: synthesis, characterization and Heck reactions(Elsevier, 2012) Motswainyana, William M.; Onani, Martin O.Two new phenylene bridged binuclear bis(imino-quinolyl) palladium (II) complexes were prepared from the reaction of the ligand 1,4-bis(imino-quinolyl)benzene, L1 with either Pd(cod)Cl2 or Pd(cod)ClMe. The molecular structure of L1 was confirmed by single crystal X-ray diffraction analysis. The structure shows two planar molecules (A and B) in the asymmetric unit. The complexes were evaluated as catalysts for Heck coupling reactions of methyl and butyl acrylate with iodobenzene, and showed high activity. The reactions proceeded at a faster initial rate and there was good selectivity for the formation of the trans- isomers.Item New imino-pyridyl nickel (II) complexes: synthesis, molecular structures and application as Heck coupling catalysts(Elsevier, 2012) Motswainyana, William M.; Onani, Martin O.; Ojwach, Stephen O.; Omondi, BernardReactions of imino-pyridyl ligands, (2-pyridyl-2-thiophenemethyl)imine (L1) and (2-pyridyl-2-thiopheneethyl)imine (L2) with NiBr2(DME) gave the corresponding complexes [Ni(L1)Br2] (1) and [Ni(L2)Br2] (2) in good yields. Treatment of 1 and 2 with one equivalent of 2-hydroxythiophenol resulted in the displacement of the bromide ligands to form the nickel(II) thiolato complexes 3 and 4. Molecular structure of 3 confirmed that L1 and L2 bind to the nickel atom in a bidentate fashion. Complexes 1-4 catalyzed the Heck coupling reaction of iodobenzene and bromobenzene with methyl acrylate.Item Dichlorido-[(2-diphenylphosphino-benzylidene)-2-methylphenylen-amine]palladium( II) acetonitrile monosolvate(International Union of Crystallography, 2013) Motswainyana, William M.; Onani, Martin O.; Jacobs, Jeroen; van Meervelt, LucThe title imino–phosphine compound, [PdCl2(C26H22NP)] - CH3CN, was prepared by reaction of N-[2-(diphenylphosphanyl) benzylidene]-2-methylaniline with dichlorido(cycloocta- 1,5-diene)palladium(II) in dry CH2Cl2. The PdII cation is coordinated by the P and N atoms of the bidentate chelating ligand and by two chloride anions, generating a distorted square-planar coordination geometry. There is a detectable trans influence for the chloride ligands. The methyl group present in this structure has an influence on the crystal packing.Item Dichlorido-[2-(2,6-diethylphenyl)iminomethylquinoline-N,N’]palladium(II) acetonitrile monosolvate(International Union of Crystallography, 2012) Motswainyana, William M.; Onani, Martin O.; Jacobs, Jeroen; van Meervelt, LucThe title complex, [PdCl2(C20H20N2)] CH3CN, was synthesized by the reaction of 2-[(2,6-diethylphenyl)iminomethyl]quinoline with dichlorido(cycloocta-1,5-diene)palladium(II) in dry CH2Cl2. The PdII ion is coordinated by two N atoms of the bidentate quinoline ligand and by two chloride anions, generating a distorted square-planar coordination geometry around the metal centre. There is a detectable trans influence for the chloride ligands. The crystal packing is characterized by – stacking between the quinoline rings. The use of acetonitrile as the crystallization solvent was essential for obtaining good-quality crystals.