Stoichiometry,stability constants and coordination geometry of Eu(III)5-sulfosalicylate complex in aqueous system-A TRLIFS study

摘要

The complex formation between Eu(III)and 5-sulfosalicylate,(HSSA)_2~,has been investigated by means of TRLIFS(time resolved laser induced fluorescence spectroscopy).The concentration of free ligand in the solution was determined from the fluorescence emission of 5-sulfosalicylate by subtracting the dynamic quenching effect from the observed quenching of fluorescence emission by means of lifetime analysis,and the Stoichiometry and the corresponding formation constants were obtained.A carboxylate coordinated complex,Eu(HSSA)~+,and also a chelate complex,Eu(SSA),were identified,and the formation constants of the complex Eu(HSSA)~(2+)for the reaction,Eu~(3+)+ HSSA~(2-)-> Eu(HSSA)~+,and the deprotonation constant of the chelating reaction,Eu(HSSA)~+-> Eu(SSA)+ H~+,were calculated at logbeta_(1,1)= 1.79 and log K =-5.78,respectively.TRLIFS using the fluorescence emission from Eu(ni)was performed in order to determine the number of coordination waters of the complex Eu(HSSA)~(2+).The quenching of the EU(III)fluorescence caused by(SSA)~(3-)disturbed the lifetime analysis of the 'intrinsic lifetime' of EU(III)in Eu(HSSA)~(2+),however the problem was successfully solved by the analysis of emission intensity and lifetime,and the formulation of the complex was determined as[Eu(HSSA)8H_2O]~(2+)with the explicit involvement of the coordinated waters.