Chemistry

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http://10.90.10.223:4000/handle/123456789/121

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Browsing Chemistry by Subject "1"

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    Empirical Dielectric Constant from Optical Measurements
    (Addis Ababa University, 2014-06-06) Gebrekidan, Matiyos; Redi, Mesfin (PhD); Mustafa, Ahmed (PhD); Perez, Eduardo (PhD)
    Solvent effects on the vibrational and electronic absorption band of different compounds were determined. In increasing the polarity of the solvent a shift of the absorption maxima to lower energy was observed in all compounds. The solvation dielectric constant of dioxane was empirically determined from correlation plot of Lippert-Mataga polarity function versus vibrational absorption maxima of picolinamide and other amides (Acrylamide, propylamide etc.). From linear fit the value of solvation dielectric constant of dioxane was goes to infinite (r,solv=  ), which is unrealistic and unphysical. In addition, from correlation plot of Lippert-Mataga polarity function versus electronic absorption maxima of DMABA, BBA and NBA the value of solvation dielectric constant of dioxane was found to be 3.4, 3.8 and 7.7, respectively. These values were inconsistent and there is no universal solvation dielectric constant from electronic spectroscopy
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    Synthesis and Characterization of 1, 4- Dihydroquinoxaline-2,3-Dione Derivativesbased Co (Ii) and Ni (Ii) Complexes
    (Addis Ababa University, 2020-08-23) Adefris, Efrem; Chebude, Yonas (PhD)
    In recent years, there has been enhanced interest in the synthesis and characterization of transition metal complexes containing Schiff bases as ligands due to their importance. According to this concept, two Schiff base complexes, [CoL2Cl2] and [NiL2]Cl2 were synthesized based on the Schiff base ligand that was a result of condensation of 1, 4-dihydroquinoxaline-2, 3-dione and 3-hydroquinoxaline-2(1H)- one. In the process of formation of the ligand and complexes, chemicals like OPD, diethyl oxalate, hydrazine, ethylenediamine, Co (II) and Ni (II) chloride salts, and solvents such as diethyl ether, methanol, butanol, were used. The synthesized ligand and complexes were characterized using IR, UV-Vis., molar conductivity, AAS, and other physical measurements such as melting point and solubility were determined. Based on the physico-chemical analysis, octahedral structure of Co (II) complex and square planar structure of Ni (II) complex were proposed.