Complex formation between aluminium(III) and two hydroxy-aromatic ligands:2-hydroxyphenylethanone and 2-hydroxybenzeneacetic acid

The formation of complexes between aluminium(III) and two hydroxyaromatic l igands of possible environmental and biological relevance, 2-hydroxyphenyle thanone (HPE) and 2-hydroxybenzeneacetic acid (HBA), in aqueous 0.6 m (Na)C l at 25 degrees C has been investigated by means of potentiometric titratio ns. In both systems, the formation of two complexes, AlL and AlLH-1, has be en observed, and the following stability constants have been evaluated: for HPE (pK(a) = 10.027 +/- 0.004), log beta(AlL) = 7.34 +/- 0.01 and log beta (AlLH-1) = 1.97 +/- 0.04; for HBA (pK(a1) = 4.116 +/- 0.004 and pK(a2) = 10 .507 +/- 0.008), log beta(AlL) = 8.06 +/- 0.03 and log beta(AlLH-1) = 3.11 +/- 0.07. The qualitative and quantitative results obtained have been parti ally confirmed by UV-spectrophotometry and H-1 NMR spectroscopy.