Stability constants and multinuclear NMR measurements of phosphonic acid derivatives with aluminum in aqueous solutions |
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| Institution: | 1. Division of Forest and Biomaterials Science, Graduate School of Agriculture, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan;2. Guangzhou Sugarcane Industry Research Institute, Guangzhou 510316, China;1. Mechanical Engineering College, Advanced Material Institute, Shijiazhuang 050003, PR China;2. Artillery Investigation Radar Office, Mechanical Engineering College, Heping West Road, 97, Shijiazhuang 050003, PR China;3. Shijiazhuang Environment Monitoring Center, Beixin Street, 169, Shijiazhuang 050022, PR China;1. School of Materials Science and Engineering, Nanyang Technological University, Blk N4.1, Nanyang Avenue, Singapore 639798, Singapore;2. Institute of Materials Research and Engineering (IMRE), Agency for Science Technology and Research (A1STAR), 3 Research Link, Singapore 117602, Singapore;1. Departamento de fisica, Universidad del Zulia, Maracaibo, Venezuela;2. Laboratoire Charles Coulomb (L2C), Université Montpellier, 34095 Montpellier, France;3. CNRS UMR 7263, Institut Méditerranéen de Biodiversité et d’Ecologie marine et continentale, Aix Marseille Université, 13397 Marseille, France;4. IRD UMR 237-IMBE, Campus Agro Environnemental Caraibes, B.P. 214 Petit Morne, 97232 Le Lamentin, Martinique |
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| Abstract: | We are reporting the stability constants of the different complexes between phosphonoacetic acid (PAA), phosphonoformic acid (PFA), aminomethylphosphonic acid (AMPA), aminoethylphosphonic acid (AEPA) and methylenediphosphonic acid (MDP) with the aluminum metal ion in aqueous solutions. (In this study the term aluminum is reserved for the 3+ ion.) The affinity of the phosphonic acid derivatives to chelate aluminum has been tested by potentiometric titrations with I = 0.10 M KNO3 at 25 ± 0.1 °C. The proposed aluminum–ligand complex structures have been confirmed by 31P NMR, 13C NMR, and 27Al NMR experiments. Both PAA and PFA formed simple one to one complexes. The respective values for PAA are log β111 = 13.57, log β110 = 10.58, and log β11?1 = 5.84. The respective values for PFA are log β112 = 15.24, log β111 = 13.11, and log β110 = 6.88. In contrast to PAA and PFA, the major species formed with AMPA and AEPA consist of a series of dimeric complexes. The 31P NMR spectra of these complexes indicate that the amine groups do not co-ordinate to aluminum and remain protonated. In addition to these dimeric complexes, a monoprotonated monomer of Al–AMPA also has been detected. The 27Al NMR experiments indicated that the aluminum is hexacoordinated in all the complexes in this study and the hydroxide ion did not remove aluminium from its complexes. Among the ligands studied, PAA and PFA were able to solubilize aluminum at physiological pH. A comparison between the acidities and the chelating properties of the ligands used is presented. |
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