First fluorescence spectroscopic investigation of Am(III) complexation with an organic carboxylic ligand, pyromellitic acid

For the first time Am(III) complexation with a small organic ligand could be identified and characterized with time-resolved laser-induced fluorescence spectroscopy (TRLFS) at room temperature and trace metal concentration. With pyromellitic acid (1,2,4,5-benzene-tetracarboxylic acid, BTC) as ligand spectroscopic characteristics for the Am BTC complex system as well as for the Am3+(aq) ion were determined at pH 5.0, an ionic strength of 0.1 M (NaClO4) and room temperature. The fluorescence lifetimes were determined to be 20.8 ± 3.4 ns for Am3+(aq) and 27.3 ± 2.3 ns for the Am BTC 1 : 1 complex; the emission maximum for the 5D1 7F1 transition is 691 nm for both species. The complex stability constant for the Am BTC 1 : 1 complex was calculated to be log β110 = 5.42 ± 0.09.