Browsing by Author "Eze, Edith Ogochukwu"

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    Spectrophotometric determination of the stoichiometries, stability constants and free energies of zinc (II) and vanadium (v)complexes of anthranilic acid
    (Federal University of Technology, Owerri, 2019-05) Eze, Edith Ogochukwu
    This research work describes a simple and selective spectrophotometric methods for the determination of the stoichoiometries and the stability constants of zinc (II) and vanadium (V) complexes of anthranilic acid using Job’s method of continuous variation and Yoe-Jones mole ratio method. Zinc (II) ion formed a colourless complex with anthranilc acid at pH 4, and vanadium (V) formed a golden-yellow complex at pH 6. The complexes showed maximum absorbance at 309 nm for zinc (II) and 326.5 nm for vanadium (V). The zinc (II) ion formed a 1:2 metal to ligand mole ratio complex with anthranilic acid (HA), while vanadium (V) ion formed a 1:1 metal to ligand mole ratio complex with anthranilic acid. That is, for Zn2+/A complex, ZnA2 is formed and V5+/A- complex, VO2A is formed.The stability constants, (Log K), molar absorptivity and free energies of the formation of Zn (II) and V (V) anthranlilate complexes were 5 x 105, (5.71), 7.58 x 104 and -32.58 kJ/mol for zinc (II) anthranilate and 6.61x 104, 6.67, 4.7x 106 and -38.07 kJ/mol for vanadium (V) anthranilate, respectively. It was found that the vanadium (V) ion formed more stable complex with anthranilic acid with Log K value of 6.67 compared to zinc (II) complex with Log K value of 5.71. The negative values obtained for the free energies of both complexes showed that the reactions were spontaneous, feasible and irreversible and that stable complexes were formed. Anthranilic acid is a bidented ligand and as such formed a 4-coordinate bis-chelate with each of the metals; square planar geometry is being suggested for each of the chelate complexes, bearing in mind that anthranilic acid is a strong ligand.