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 ligands of possible environmental and biological relevance, 2-hydroxyphenylethanone (HPE) and 2-hydroxybenzeneacetic acid (HBA), in aqueous 0.6 m (Na)Cl at 25°C has been investigated by means of potentiometric titrations. In both systems, the formation of two complexes, AlL and AlLH-1, has been observed and the following stability constants have been evaluated: for HPE (pΚa = 10.027 ± 0.004), log βAlL = 7.34 ± 0.01 and log βAlLH-1 = 1.97 ± 0.04; for HBA (pΚa1 = 4.116 ± 0.004 and pΚa2 = 10.507 ± 0.008), log βAlL = 8.06 ± 0.03 and log βAlLH-1 = 3.11 ± 0.07. The qualitative and quantitative results obtained have been partially confirmed by UV-spectrophotometry and 1H NMR spectroscopy.