2-(Hydroxyimino)propanohydroxamic acid, a new effective ligand for aluminium

The capacity of a new ligand, 2-(hydroxyimino)propanohydroxamic acid (HPH, an analog of alanine), to bind the Al3+ ion has been examined. A particular objective was to check whether the HPH oximic group could take part in aluminum co-ordination together with the two hydroxamic oxygens, a possibility that could make HPH an efficient low-molecular-mass ligand for detrimental Al3+ ions in vivo. Glass electrode potentiometry, NMR spectroscopy and Electrospray Mass Spectrometry were used to investigate Al3+–HPH complex equilibria and their related structural aspects. The aluminium binding capacity of HPH was compared to that of other monohydroxamic acids. In spite of the lowest basicity of its hydroxamic moiety and the non-involvement of its oximic moiety in metal ion binding, HPH was found to be a very competitive ligand. Comparative quantum calculations performed on the systems involved suggest that electrostatic interactions induced by the ligand molecule are determining for complex stability.

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