Ligand exchange method for determination of mole ratios of relatively weak metal complexes: a comparative study
Abstract Ligand exchange method is introduced as an alternative to Job’s and mole ratio methods for studying the stoichiometry of relatively weak metal complexes in solutions. The method involves adding varying amounts of a ligand (L) to an excess constant amount of a colored complex (MX) with appro...
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doaj-0acdff9657e8472b9e2e53fa1748440e2021-08-02T15:59:27ZengBMCChemistry Central Journal1752-153X2018-12-011211710.1186/s13065-018-0512-4Ligand exchange method for determination of mole ratios of relatively weak metal complexes: a comparative studyMokhtar Mabrouk0Sherin F. Hammad1Mohamed A. Abdelaziz2Fotouh R. Mansour3Department of Pharmaceutical Analytical Chemistry, Faculty of Pharmacy, Tanta UniversityDepartment of Pharmaceutical Analytical Chemistry, Faculty of Pharmacy, Tanta UniversityDepartment of Pharmaceutical Analytical Chemistry, Faculty of Pharmacy, Tanta UniversityDepartment of Pharmaceutical Analytical Chemistry, Faculty of Pharmacy, Tanta UniversityAbstract Ligand exchange method is introduced as an alternative to Job’s and mole ratio methods for studying the stoichiometry of relatively weak metal complexes in solutions. The method involves adding varying amounts of a ligand (L) to an excess constant amount of a colored complex (MX) with appropriate stability and molar absorptivity. The absorbance of each solution is measured at the λmax of the initial complex, MX, and plotted against the concentration of the studied ligand, L. If the newly formed complex ML does not absorb at the λmax of the initial complex, then attenuation of the absorbance of the initial complex on adding varying quantities of the investigational ligand gives an inverse calibration line that intersects with the calibration curve of initial complex at a given point. If a line parallel to the ordinate is drawn from this point to the x-axis, the ratio of the two parts of the x-axis to the left and to the right (α/β) gives the metal to ligand molar ratio in the complex formed, ML. The new method has been applied to the study of the composition of iron (III) complexes with three bisphosphonate drugs: alendronate, etidronate, and ibandronate. The mole ratio was found to be 1:1 with the three investigated bisphosphonates and results were further confirmed by Job’s and mole ratio methods. The ligand exchange method is simpler, quicker, easier to perform and more accurate than Job’s and mole ratio methods for studying weak and relatively weak complexes.http://link.springer.com/article/10.1186/s13065-018-0512-4Ligand exchange methodMole ratio methodJob’s methodBisphosphonatesRelatively weak complexes |
collection |
DOAJ |
language |
English |
format |
Article |
sources |
DOAJ |
author |
Mokhtar Mabrouk Sherin F. Hammad Mohamed A. Abdelaziz Fotouh R. Mansour |
spellingShingle |
Mokhtar Mabrouk Sherin F. Hammad Mohamed A. Abdelaziz Fotouh R. Mansour Ligand exchange method for determination of mole ratios of relatively weak metal complexes: a comparative study Chemistry Central Journal Ligand exchange method Mole ratio method Job’s method Bisphosphonates Relatively weak complexes |
author_facet |
Mokhtar Mabrouk Sherin F. Hammad Mohamed A. Abdelaziz Fotouh R. Mansour |
author_sort |
Mokhtar Mabrouk |
title |
Ligand exchange method for determination of mole ratios of relatively weak metal complexes: a comparative study |
title_short |
Ligand exchange method for determination of mole ratios of relatively weak metal complexes: a comparative study |
title_full |
Ligand exchange method for determination of mole ratios of relatively weak metal complexes: a comparative study |
title_fullStr |
Ligand exchange method for determination of mole ratios of relatively weak metal complexes: a comparative study |
title_full_unstemmed |
Ligand exchange method for determination of mole ratios of relatively weak metal complexes: a comparative study |
title_sort |
ligand exchange method for determination of mole ratios of relatively weak metal complexes: a comparative study |
publisher |
BMC |
series |
Chemistry Central Journal |
issn |
1752-153X |
publishDate |
2018-12-01 |
description |
Abstract Ligand exchange method is introduced as an alternative to Job’s and mole ratio methods for studying the stoichiometry of relatively weak metal complexes in solutions. The method involves adding varying amounts of a ligand (L) to an excess constant amount of a colored complex (MX) with appropriate stability and molar absorptivity. The absorbance of each solution is measured at the λmax of the initial complex, MX, and plotted against the concentration of the studied ligand, L. If the newly formed complex ML does not absorb at the λmax of the initial complex, then attenuation of the absorbance of the initial complex on adding varying quantities of the investigational ligand gives an inverse calibration line that intersects with the calibration curve of initial complex at a given point. If a line parallel to the ordinate is drawn from this point to the x-axis, the ratio of the two parts of the x-axis to the left and to the right (α/β) gives the metal to ligand molar ratio in the complex formed, ML. The new method has been applied to the study of the composition of iron (III) complexes with three bisphosphonate drugs: alendronate, etidronate, and ibandronate. The mole ratio was found to be 1:1 with the three investigated bisphosphonates and results were further confirmed by Job’s and mole ratio methods. The ligand exchange method is simpler, quicker, easier to perform and more accurate than Job’s and mole ratio methods for studying weak and relatively weak complexes. |
topic |
Ligand exchange method Mole ratio method Job’s method Bisphosphonates Relatively weak complexes |
url |
http://link.springer.com/article/10.1186/s13065-018-0512-4 |
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