Browsing by Author "Getachew, Negash"

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    Benign Methods for the Synthesis of Metal Organic Frameworks (MOFs)
    (Addis Ababa University, 2013-06-06) Getachew, Negash; Chebude, Yonas (PhD)
    The recent interest in the synthesis of hybrid inorganic–organic solids (metal organic frameworks or MOFs) gives a new dimension to the domain of porous compounds. They offer new scientific and technological opportunities by combining attractive features of both porous solids and organometallics. Most of them are prepared under mild hydrothermal conditions using functionalized organic ligand and organic amines. Hence there is a need to develop an environmentally green and energetically favorable method in the synthesis of these materials. The main challenge behind the synthesis of MOFs under benign conditions is the insolubility of the organic linkers in most of the common solvents. In this work, different MOFs have been synthesized using water as a solvent for the metal salts. Some of these are known MOFs [MOF-2, HKUST-1 and MOF-74 (Zn)] while others are uncommon phases. Using a linker salt (disodiumterephthalate or Na2BDC), two of the most popular MOFs: MIL-53(Al) (MIL=Material of Institute Lavoisier) and MOF-5 [Zn4O(BDC)3] have been synthesized at room temperature. Especially MIL-53(Al) or aluminum - 1,4-benzenedicarboxylate was synthesized at room temperature using water as a solvent for the first time. The linker salt approach can be applied as a general strategy consisting in the use of linker salts as an alternative to the exclusively tested acidic form of the linker (protonated linkers). The method does not only imply the prevention of the undesirable corrosive synthesis medium, but it also introduces substantial differences in terms of solubility of the linker, and pH of the medium. Hence, a novel method in the synthesis of metal organic framework materials has been developed under environmentally benign conditions. - Spanish cooperation Agency for financing my research undertaking in Spain - A.A.U. for giving me an opportunity to pursue my graduate studies I would like to appreciate and bless my mother W/O Almaz, my brothers (Seyoum, Meseret, Abreham and Eyob) and my sisters (Genet, Tigist, Amelework, Abaynesh and Muluken) for their prayers, unreserved help and encouragement throughout the course of this work. My heartfelt appreciation and gratitude goes to my family; my soul mate and companion of my life Mesti, my son Muse and my daughter Bethel for their endless support, prayer, love and sacrifice.
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    Studies on First Rowtransition Metal Complexes Derived from Ninhydrin and Amino Acids Having Polar(Threonine) and Nonpolar(Leucine) Side Chains
    (Addis Ababa Universty, 2003-06) Getachew, Negash
    Complexes of Co(II), Ni(II), and Zn(II) with Ruhmann’s purple, those of Fe(III) and Mn(II) with an intermediate Schiff base ( ketimine and / or aldimine) and Cu(II) with ninhydrin were successfully synthesized. All complexes were distinctly colored and stable to atmospheric conditions. The complexes were characterized by elemental analysis, molar conductance, magnetic susceptibility, infrared and electronic spectral studies. The ligands were shown to behave as a monobasic tridentate ONO, bidentate ON or OO donor. The complexes of Zn(II), Co(II) and Ni(II) are purely Ruhmann’s purple, those of Mn(II) and Fe(III) are Schiff base (ketimine), Schiff base and ninhydrin or Schiff base and Ruhmann’s purple complexes. An octahedral geometry is proposed for all of the metal complexes, except Mn(II). A comparative anti- microbial study of the complexes was undertaken against two gram - negative bacteria, Escherichia coli and one gram - positive bacterium Staphylococcus aureus. It was revealed that except Cu(II) and to some extent Zn(II) complexes most of the complexes exhibit a reduced activity against both bacterium. KEY WORDS: metal complexes, Schiff base, ninhydrin, Ruhmann’s purple, ᾳ– Leucine, ᾳ–L–Threonine and antimicrobial activity