Thermodynamic Study on the Dissociation and Complexation of Coumarinic Acid with Neodymium(III) and Dioxouranium(VI) in Aqueous Media
In the frame of a systematic study on the sequestering ability of natural antioxidants towards metal cations, the complexation of coumarin-3-carboxilic acid (HCCA) with neodymium(III) and dioxouranium(VI) (uranyl, UO<sub>2</sub><sup>2+</sup>), and overall stability constants...
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MDPI AG
2021-05-01
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| Online Access: | https://www.mdpi.com/2076-3417/11/10/4475 |
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| author | Luana Malacaria Giuseppina Anna Corrente Emilia Furia |
| author_facet | Luana Malacaria Giuseppina Anna Corrente Emilia Furia |
| author_sort | Luana Malacaria |
| collection | DOAJ |
| description | In the frame of a systematic study on the sequestering ability of natural antioxidants towards metal cations, the complexation of coumarin-3-carboxilic acid (HCCA) with neodymium(III) and dioxouranium(VI) (uranyl, UO<sub>2</sub><sup>2+</sup>), and overall stability constants of the resulting complexes, were evaluated from the pH-potentiometric titration data at 37 °C and in an aqueous solution (i.e., 0.16 mol/L NaClO<sub>4</sub>). The graphic representation of the complex’s concentration curves is given by the distribution diagrams, which provide a depiction of all the species present in the solution in the selected pH ranges. The protonation constant of HCCA was also determined to evaluate the competition of the ligand for the metal cations and H<sup>+</sup>. The ligand-to-metal concentration ratio was varied between 1 and 10, and the hydrogen ion concentration was decreased stepwise until the incipient precipitation of a basic salt of the metal, which occurred at different values depending on the specific metal cation and the ligand to metal ratio. Speciation profiles obtained by potentiometric titrations and supported by UV-Vis data show that a complexation occurs at a ligand-to-Nd(III) and to –UO<sub>2</sub><sup>2+</sup> ratio of 1:1 and 2:1, with different degrees of deprotonation: Nd(OH)(CCA)<sup>+</sup>, UO<sub>2</sub>(OH)(CCA), UO<sub>2</sub>(OH)<sub>2</sub>(CCA)<sup>−</sup>, and Nd(OH)(CCA)<sub>2</sub>, UO<sub>2</sub>(CCA)<sub>2</sub> and (UO<sub>2</sub>)<sub>2</sub>(OH)<sub>2</sub>(CCA)<sub>2</sub>. |
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| last_indexed | 2024-03-10T11:25:04Z |
| publishDate | 2021-05-01 |
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| record_format | Article |
| series | Applied Sciences |
| spelling | doaj.art-a178cddd85a34ec18ca350a26523def62023-11-21T19:43:58ZengMDPI AGApplied Sciences2076-34172021-05-011110447510.3390/app11104475Thermodynamic Study on the Dissociation and Complexation of Coumarinic Acid with Neodymium(III) and Dioxouranium(VI) in Aqueous MediaLuana Malacaria0Giuseppina Anna Corrente1Emilia Furia2Department of Chemistry and Chemical Technologies, University of Calabria, 87036 Rende, CS, ItalyDepartment of Chemistry and Chemical Technologies, University of Calabria, 87036 Rende, CS, ItalyDepartment of Chemistry and Chemical Technologies, University of Calabria, 87036 Rende, CS, ItalyIn the frame of a systematic study on the sequestering ability of natural antioxidants towards metal cations, the complexation of coumarin-3-carboxilic acid (HCCA) with neodymium(III) and dioxouranium(VI) (uranyl, UO<sub>2</sub><sup>2+</sup>), and overall stability constants of the resulting complexes, were evaluated from the pH-potentiometric titration data at 37 °C and in an aqueous solution (i.e., 0.16 mol/L NaClO<sub>4</sub>). The graphic representation of the complex’s concentration curves is given by the distribution diagrams, which provide a depiction of all the species present in the solution in the selected pH ranges. The protonation constant of HCCA was also determined to evaluate the competition of the ligand for the metal cations and H<sup>+</sup>. The ligand-to-metal concentration ratio was varied between 1 and 10, and the hydrogen ion concentration was decreased stepwise until the incipient precipitation of a basic salt of the metal, which occurred at different values depending on the specific metal cation and the ligand to metal ratio. Speciation profiles obtained by potentiometric titrations and supported by UV-Vis data show that a complexation occurs at a ligand-to-Nd(III) and to –UO<sub>2</sub><sup>2+</sup> ratio of 1:1 and 2:1, with different degrees of deprotonation: Nd(OH)(CCA)<sup>+</sup>, UO<sub>2</sub>(OH)(CCA), UO<sub>2</sub>(OH)<sub>2</sub>(CCA)<sup>−</sup>, and Nd(OH)(CCA)<sub>2</sub>, UO<sub>2</sub>(CCA)<sub>2</sub> and (UO<sub>2</sub>)<sub>2</sub>(OH)<sub>2</sub>(CCA)<sub>2</sub>.https://www.mdpi.com/2076-3417/11/10/4475coumarin-3-carboxilic acidNd(III) complexesUO<sub>2</sub><sup>2+</sup> complexessequestering abilitystability constants |
| spellingShingle | Luana Malacaria Giuseppina Anna Corrente Emilia Furia Thermodynamic Study on the Dissociation and Complexation of Coumarinic Acid with Neodymium(III) and Dioxouranium(VI) in Aqueous Media Applied Sciences coumarin-3-carboxilic acid Nd(III) complexes UO<sub>2</sub><sup>2+</sup> complexes sequestering ability stability constants |
| title | Thermodynamic Study on the Dissociation and Complexation of Coumarinic Acid with Neodymium(III) and Dioxouranium(VI) in Aqueous Media |
| title_full | Thermodynamic Study on the Dissociation and Complexation of Coumarinic Acid with Neodymium(III) and Dioxouranium(VI) in Aqueous Media |
| title_fullStr | Thermodynamic Study on the Dissociation and Complexation of Coumarinic Acid with Neodymium(III) and Dioxouranium(VI) in Aqueous Media |
| title_full_unstemmed | Thermodynamic Study on the Dissociation and Complexation of Coumarinic Acid with Neodymium(III) and Dioxouranium(VI) in Aqueous Media |
| title_short | Thermodynamic Study on the Dissociation and Complexation of Coumarinic Acid with Neodymium(III) and Dioxouranium(VI) in Aqueous Media |
| title_sort | thermodynamic study on the dissociation and complexation of coumarinic acid with neodymium iii and dioxouranium vi in aqueous media |
| topic | coumarin-3-carboxilic acid Nd(III) complexes UO<sub>2</sub><sup>2+</sup> complexes sequestering ability stability constants |
| url | https://www.mdpi.com/2076-3417/11/10/4475 |
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