2-Hydroxy-3-carboxy-dlhydrocinnamic acid: Complexation properties towards alurninium(III) and iron(III)

2-Hydroxy-3-carboxy-dihydrocinnamic acid (H3L) is proposed as a simple salicylic acid derivative able to form tridentate complexes with Al(III) and Fe(III). H3L was synthesized, and its complexation properties towards Al(III) and Fe(III) have been studied by means of potentiometric titrations, UV–Vis and NMR measurements at 25 degrees in aqueous (Na)Cl 0.6 m. pKa values of the ligand are 2.68 ± 0.02 (H3L) and 4.49 ± 0.01 (H2L-). The complexes with the following stoichiometry (and stability constant, log beta values) were identified: AlLH+ (3.888 ± 0.003), AlL (-0.273 ± 0.003), and AlL2 3 (2.93 ± 0.06) for Al(III), and FeLH+ (6.54 ± 0.04), FeL (3.0 ± 0.1), FeL2H2 (10.5 ± 0.1), and FeL2H2 (7.34 ± 0.08) for Fe(III). Most of the Al(III) and Fe(III) species are either bidentate (salicylate-like), or mixed ligand-hydroxo complexes. The tridentate chelation is displayed in the AlL species. Molecular modeling confirmed experimental results.