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Interactions of Aluminum(III) with Phosphates
Károly Atkári1, Tamás Kiss, Roberta Bertani
1Department of Inorganic and Analytical Chemistry, Kossuth University, H-4010 Debrecen, Hungary, Centro di Studio Sulla Chimica e Tecnologia dei Compositi Metallorganici degli Elementi di Transizione, CNR, I-35131 Padova, Italy, and Department of Chemistry, University of Virginia, Charlottesville, Virginia 22903.
Inorganic Chemistry
|November 20, 1996
Summary
Aluminum(III) interactions with various phosphates were studied using potentiometric measurements. A linear free energy relation revealed similar binding for most ligands, estimating aluminum(III)-orthophosphate binding and confirming citrate
Area of Science:
- Inorganic Chemistry
- Coordination Chemistry
- Biophysical Chemistry
Background:
- Understanding aluminum(III) interactions with phosphates is crucial for biological and environmental systems.
- The precipitation of aluminum(III)-orthophosphate complicates direct study of these interactions.
- Organic phosphates, phosphonates, and nucleoside monophosphates are relevant ligands in biological systems.
Purpose of the Study:
- To characterize the complex-forming properties of aluminum(III) with a range of phosphate-containing ligands.
- To overcome the challenge of precipitation in the aluminum(III)-orthophosphate system.
- To estimate the stability constant of aluminum(III) binding to orthophosphate.
Main Methods:
- Potentiometric measurements were employed to determine stability constants.
- Linear Free Energy Relations (LFER) were used to correlate ligand basicity with complex stability.
- (31)P Nuclear Magnetic Resonance ((31)P NMR) spectroscopy supported structural elucidation.
Main Results:
- A LFER demonstrated similar binding affinities of Al(III) to organic phosphates, phosphonates, and several nucleoside-5'-monophosphates.
- Adenosine and cytidine 5'-monophosphates deviated from the LFER due to specific protonation and hydroxide binding.
- The estimated log stability constant for Al(III)-HPO(4)(2-) binding is 6.13 ± 0.05.
- Al(III) binding to di- and triphosphates differs from monophosphates.
Conclusions:
- The study provides insights into Al(III) complexation with diverse phosphate ligands.
- The findings support the limited role of soluble orthophosphate complexes in serum, highlighting citrate's importance.
- The methodology developed allows for the study of otherwise intractable metal-phosphate systems.