Abstract:
The determination of ionization constants and the
chelating properties exhibited by a series of derivatives of
N-phenylbenzohydroxamic acid, N-phenyllaurohydroxamic
acid and 1-naphmalenememylimminodiacetohydroxamic
acid type ligands toward Fe(III), Cu(II) and Ni(II) ions were
studied by pH-metric method. The data obtained by pH-metric
method were analyzed by three standard methods namely,
Bjerrum's method, Irving and Rossotti method, and Sarkar and
Kruck method. The ionization constants of hydroxamic acids
and the stability constants of metal-ligand complexes were
calculated using the above three methods and it was found
that the values obtained closely agreed with each other. The
evaluation of the calculated stability constants shows that the
substituent effect on the N-phenyl ring leads to more basic
character at the carbonyl oxygen and it influences significantly
the stability of the complex species formed by the hydroxamate
moieties. The stability constant and the species distribution
of Fe(III) - 1-naphmalenemethylimminodiacetohydroxamic
acid system at physiological pH range (6.8 - 7.2) suggest that
1-naphmalenememylimminodiacetohydroxamic acid is an
effective source for the iron overload.
