Abstract
Some new ternary complexes’ [Cu(II), Ni(II), Co(II), and Zn(II)] metal ions with phenylephrine and some selected carboxylic acid were investigated by means of potentiometry techniques at 25 °C and in I = 0.10 mol L−1 NaNO3. The protonation equilibria of phenylephrine and biologically important aliphatic and aromatic carboxylic acids: adipic, succinic, malic, tartaric, oxalic, phthalic, and salicylic were investigated and discussed. The acidity constants of the ligand under study were determined and used for determining the stability constants of the binary and ternary complexes formed in the aqueous medium under the experimental conditions. The order of stability constants of binary and ternary complexes was found to obey Co(II) Zn(II). The ternary complex formation was found to occur in a stepwise manner. Extrastability of ternary complexes compared to their binary complexes was explained to be due to electrostatic interactions of the side chains of ligands, charge neutralization, chelate effect, stacking interactions, and hydrogen bonding. The relative stabilities of the ternary complexes are compared with those of the corresponding binary complexes in terms of (ΔlogK, \(\log X\) and % R. S) values. The concentration distribution of the various complex species in solution was evaluated and discussed.
Published Version
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