ARAMENDIA Pedro Francisco
congresos y reuniones científicas
Fluorescence quenching of complexes of Eu(III) and Tb(III) by transition metal cations.
BEATRIZ CARMEN BARJA; MIREILLE PEREC; PEDRO F. ARAMENDÍA
Viña del Mar
Congreso; VII Encuentro Latinoamericano de Fotoquímica y Fotofísica.; 2002
The steady state luminiscence quenching of different complexes of Eu(III) and Tb(III) with Cu(II) and Co(II) were measured in aqueous solution. The emission decay of all the complexes are monoexponential. Their lifetimes (to ) cover the range of 0.1 - 1.5 ms (for Eu(III) aquo and [Eu(DPA)33-]a, respectively), and 0.44 - 1.0 ms for Tb(III) aquo and [Tb(oda)33-]b reflecting the efficiencies of the ligands to occupy the coordination sites of the metal coordination sphere to prevent the deactivation of the luminiscence by the water molecules. The charge of the complexes in solution was inferred from the difference in the decay times in D2O compared to H2O. From this difference, the number of water molecules in the first coordination sphere of the metal (q) can be calculated. The quenching constants (kQ, M-1.s-1) for Cu(II) obtained from the linear regression of the Stern Volmer plots show in all cases that the higher values are obtained as the charge of the lanthanide complex becomes more negative, indicating that a favorable electrostatic interaction between the complex and the metal quencher enhances the quenching process.(kQ = 2 106 for [Eu(crot)3]c and 5 107 for [Eu(oda)33-]). Only in the case of the [Eu(DPA)33-] complex, the Stern Volmer plots were not linear, evidencing both dynamic and static quenching. Among the transition metals studied, Cu(II) is the most efficient quencher of the luminiscence of all the Eu(III) and Tb(III) complexes. The Stern Volmer constants for Co(II) are 4-5 fold lower than the corresponding values for Cu(II). a H2DPA (2,6- pyridinedicarboxylic acid. b H2oda (oxydiacetic acid). c Hcrot (crotonic acid)