Browsing by Author "O'Brien, P."

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    Cobalt(III) complexes of a-w- diaminocarboxylic acids and chloroquine
    (2001) Govender, kuvasani; Kolawole, G.A.; O'Brien, P.
    a-w-Diaminocarboxylic acids, such as lysine and 2,3-diaminopropionic acid (2,3-DAPH), are trifunctional, and thus, when only two sites are available for coordination, an interesting question is posed as to which functional groups are utilised in chelation. A series of cobalt(III) complexes of the formulation [Co(en)2AA]2+, where en is ethylenediamine and AA represents lysine and DL-2,3-DAP, were prepared. In addition, complexes of the type [Co(AA)(AAH)Cl2] and [Co(AA)2]+, where AA is DL-2,3-DAP, have been synthesised. The compounds were characterised using elemental analysis, NMR, IR and electronic spectroscopy and mass spectrometry. The reaction of czs-[Co(en)2Cl2]Cl with lysine yielded two products notably, [Co(en)2(lys)]2+, within which lysine coordinates via the a-nitrogen and oxygen donor atoms, and [Co(en)3]3+. The reaction of c/s-[Co(en)2Cl2]Cl with DL-2,3-DAPH, however, yielded three products, viz. [Co(en)2(2,3-DAP)]2+, in which the glycinate portion of 2,3-DAP is involved in chelation, [Co(2,3-DAP)2]+ where 2,3-DAP acted as a tridentate ligand, and [Co(en)3]3+. In [Co(2,3-DAP)(2,3-DAPH)Cl2], one of the 2,3-DAP ligands coordinated via the two amino groups leaving the carboxylic acid group free whilst the second ligand coordinated via the glycinate portion leaving the terminal amino group free.
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    N,N'-diisopropylthiourea and N,N'-dicyclohexylthiourea zinc(II) complexes as precursors for the synthesis of ZnS nanoparticles
    (Academy of Science of South Africa, 2009) Moloto, N.; Revaprasadu, N.; Moloto, M.J.; O'Brien, P.
    The single X-ray crystal structures of zinc (II) complexes of N,N'-diisopropylthiourea and N,N'-dicyclohexylthiourea were determined. These complexes, similar to other alkylthioureas, were found to be effective as precursors for the preparation of hexadecylamine-capped ZnS nanoparticles. The complexes are air-stable, easy to prepare and inexpensive. They pyrolyse cleanly to give high-quality ZnS nanoparticles, which show quantum confinement effects in their absorption spectra and close to band-edge emission. Their broad diffraction patterns are typical of nanosized particles while their transmission electron microscopy images showed agglomerates of needle-like platelet nanoparticles.