The interaction between aluminium ion (Al) and quinolic acid (L) in acidic aqueous solution was investigated by potentiometry and 13C and 27Al NMR spectroscopy. In the 27Al NMR spectra, two peaks were observed at 8 and 15.6 ppm, which were assigned to AlL and AlL2 complexes, respectively. The 13C NMR spectra provide clear evidence that the L acts as a bidentate ligand and that the L coordinates with a nitrogen atom and an oxygen atom of the adjacent carboxylic group to form a chelate complex with a five-membered ring. From a potentiometric study, the formation constants (log β1 and log β2) for the AlL and AlL2 complexes were estimated to be 4.52 ± 0.02 and 7.99 ± 0.05, respectively.
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