Metal ion-binding properties of the diphosphate ester analogue, methylphosphonylphosphate, in aqueous solution.
- Song B Institute of Inorganic Chemistry University of Basel Spitalstrasse 51 Basel CH-4056 Switzerland.
- Zhao J
- Gregán F
- Prónayová N
- Sajadi SA
- Sigel H
- 2008-05-14
Published in:
- Metal-based drugs. - 1999
English
The stability constants of the 1:1 complexes formed between methylphosphonylphosphate (MePP(3-)), CH(3)P(O)(-) (2)-O-PO3(2-), and Mg(2+), Ca(2+), Sr(2+), Ba(2+), Mn(2+), Co(2+), Ni(2+), Cu(2+), Zn(2+), or Cd(2+) (M(2+)) were determined by potentiometric pH titration in aqueous solution (25 degrees C; l = 0.1 M, NaNO(3)). Monoprotonated M(H;MePP) complexes play only a minor role. Based on previously established correlations for M(2+)-diphosphate monoester complex-stabilities and diphosphate monoester beta-group. basicities, it is shown that the M(Mepp)(-) complexes for Mg(2+) and the ions of the second half of the 3d series, including Zn(2+) and Cd(2+), are on average by about 0.15 log unit more stable than is expected based on the basicity of the terminal phosphate group in MePP(3-). In contrast, Ba(Mepp)(-) and Sr(Mepp)(-) are slightly less stable, whereas the stability for Ca(Mepp)(-) is as expected, based on the mentioned correlation. The indicated increased stabilities are explained by an increased basicity of the phosphonyl group compared to that of a phosphoryl one. For the complexes of the alkaline earth ions, especially for Ba(2+), it is suggested that outersphere complexation occurs to some extent. However, overall the M(Mepp)(-) complexes behave rather as expected for a diphosphate monoester ligand.
- Language
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- English
- Open access status
- gold
- Identifiers
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- DOI 10.1155/MBD.1999.321
- PMID 18475908
- Persistent URL
- https://sonar.ch/global/documents/18133
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