Potentiometric Studies of Stability Constants and Speciation of Binary and Ternary Complexes of Metal (II) Ions with Amino Acids and Thiobarbituric Acid

Kayode Taiwo Ishola,Omobola Ajibike Odedokun,Oladapo Tunde Olanipekun,Mary Adelaide Oladipo

doi:10.11648/j.ajac.20200801.14

Kayode Taiwo Ishola, Omobola Ajibike Odedokun + Show 2 more

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https://doi.org/10.11648/j.ajac.20200801.14

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Abstract

Several chelating agents have been widely used as scavengers to transport metals to or away from vulnerable sites due to their ability to form stable complexes with different metal ions. Many of the chelating agents have been reported to be toxic, non-biodegradable and inflexible for the recovery of bound metal ions. The inherent drawbacks with these chelating agents necessitate a search for their replacement. Therefore, the extent of coordination of L-tyrosine, L-histidine (secondary ligands) and Thiobarbituric acid (primary ligand) with Co(II), Cu(II) and Pb(II) in an aqueous medium at 27°C and 35°C has been examined potentiometrically with ionic strength maintained by 0.02M NaNO3. The potentiometric equilibrium measurements showed that the ligands formed binary and ternary complexes with the metal ions. Ternary complexes were formed by simultaneous mechanisms and they were found to be more stable than the corresponding binary complexes. The order of stability was found to increase with an increase in the covalent index of the metal ions and decrease with increase in temperature. Speciation diagram showed the variation in stability constants of the binary and ternary complexes as the function of pH. The ligands exhibited high coordinating properties and could be used as metal scavengers for transportation of metals to or away from vulnerable sites. The binary metal complexes could be applied as a medium of transporting chemotherapeutic drugs to target sites or detoxifying poisonous substances which possesses donor atoms with chelating capability.

Highlights

The advances in inorganic chemistry provide better opportunities to use coordination compounds and chelators in nutritional supplements, fertilizers, chemical analysis, as water softeners, commercial products such as shampoos and food preservatives, medicine, heavy metal detox, and industrial applications [1, 2]
This study investigated binding abilities of L-histidine, Ltyrosine and Thiobarbituric acid with Co(II), Cu(II) and Pb(II) ions in forming binary and ternary complexes with a view of assessing their potential in transporting the metal ions to or away from vulnerable sites
For the sake of briefness, the curves for the ligands, binary complexes and ternary complexes at 27°C and 35°C are presented in Figures 1 and 2 respectively

Summary

Introduction

The advances in inorganic chemistry provide better opportunities to use coordination compounds and chelators in nutritional supplements, fertilizers, chemical analysis, as water softeners, commercial products such as shampoos and food preservatives, medicine, heavy metal detox, and industrial applications [1, 2]. The study of co-ordinate compounds in solution on the basis of equilibrium provides information on stability constants of the complexes which give detail of the complexation reactions of the metal ions, complex formation ability of the ligands and the activities of the complexes formed in a solution containing two or more component species in equilibrium. The application of the transition metals in many industries have led to the contamination of air, soil and water which are global problems that have become a growing threat to humanity. As a result of this, researchers have focused on the study of Kayode Taiwo Ishola et al.: Potentiometric Studies of Stability Constants and Speciation of Binary and Ternary

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