Complexation of europium(III) by hydroxybenzoic acids: a time-resolved luminescence spectroscopy study

Pauline Moreau (1) , Sonia Colette-Maatouk (1) , Pierre Vitorge (2) , Pierre Gareil (3) , Pascal E. Reiller (1)

1 LANIE - Laboratoire de développement Analytique Nucléaire Isotopique et Elémentaire
2 LRMO - Laboratoire de Radiolyse et de la Matière Organique
3 LECA - Laboratoire d'Electrochimie et de Chimie Analytique

Complexation of Eu(III) by two hydroxybenzoic acids, namely p-hydroxybenzoic acid (4 dihydroxybenzoic, HPhbH), and protocatechuic acid (3,4-dihydroxybenzoic, HProtoH2), is studied by time-resolved luminescence spectroscopy (TRLS) in mildly acidic solution. Comparable formation constants are determined at 0.1 mol/L NaCl for EuPhbH[2+] – log10β°(EuPhbH[2+]) = 2.18 ± 0.09 (1sigma) – and 0.01 mol/L NaCl for EuProtoH2[2+] – log10β°(EuProtoH2[2+]) = 2.72 ± 0.07 (1sigma). The stoichiometry and carboxylate complexation of the EuProtoH2[2+] complex is ascertained by varying both pH and ligand concentration. The luminescence decay time of EuPhbH[2+] (τ = 107 ± 5 µs) is comparable with that of Eu(H2O)n[3+] (τ = 110 ± 3 µs), suggesting that luminescence quenching processes compensate the expected increase in decay time due to the dehydration associated with complexation. For EuProtoH2[2+], the luminescence decay time is even shorter (τ = 20 ± 5 µs), evidencing intricate quenching processes.

Mots clés: Euroium; lanthanides; hydroxybenzoic acids; phenolic acids; complexation; time-resolved luminescence spectroscopy

Domaines: Géochimie; Chimie; Chimie de coordination; Chimie inorganique

Pauline Moreau, Sonia Colette-Maatouk, Pierre Vitorge, Pierre Gareil, Pascal E. Reiller. Complexation of europium(III) by hydroxybenzoic acids: a time-resolved luminescence spectroscopy study. Inorganica Chimica Acta, 2015, 432, pp.81-88. ⟨10.1016/j.ica.2015.03.036⟩. ⟨hal-01194523⟩