Luminescence spectroscopy of Eu(Bis-tris)(3+) complexes in anhydrous DMF [Bis-tris=2,2-bis(hydroxymethyl)-2,2 ',2 ''-nitrilotriethanol]: luminescence quenching rate constants for the D-5(0) state of Eu3+ by DMF and polyalcoholic OH groups

Abstract

Excitation and emission spectra and luminescence lifetimes of Eu3+ complexes obtained by dissolving anhydrous EuCl3 and EuCl3/2,2-bis(hydroxymethyl)-2,2',2"- nitrilotriethanol (Bis-tris) in anhydrous dimethylformamide (DMF) and those from a Eu(Bis-tris)(2)Cl-3 crystalline sample have been studied. Two distinct Eu3+ complexes were observed when anhydrous EuCl3 was dissolved in anhydrous DMF, and one was interpreted as an outer-sphere complex of Cl- anion. Dissolution of an excess amount of vacuum dried NaClO4 or KPF6 in anhydrous DMF resulted in longer luminescence lifetimes, presumably reducing the effects of trace amounts of water in the solvent due to competitive binding of the water in the solvent by alkali metal cations. The quenching rate constant for the D-5(0) state of Eu3+ ion by each complexed DMF molecule in solution and by each OH group in the Bis-tris from the Eu(Bis-tris)(2)Cl-3 crystalline sample were 54 +/-1 and 495 +/-5 s(-1), respectively, and these were used to interpret the plausible structures of the different Eu3+ complexes in the EuCl3/Bis-tris/DMF solution.