Synthesis and luminescent properties of three new and bright Eu - tta compounds modified on α-carbon for use as biological markers

Abstract

Three smarts luminescent Eu3+ complexes (Eu1 = Eu(tta-ester)3phen 1, Eu2 = Eu(tta- NH2)3phen 2, Eu3 = Eu(tta-COOH)3phen, were synthesized by using phenanthroline as the neutral ligand and Cα modified 2-thenoyltrifluoroacetonate and as the anionic ligand. All the Eu(III) complexes were structurally characterized by spectroscopic methods. Photoluminescence (PL) emission spectra of Eu complexes showed red color emission in the solid state. These materials were analyzed by X-ray diffraction, scanning electron microscopy and by energy dispersive, ultraviolet–visible spectroscopy, luminescence and vacuum ultraviolet–ultraviolet spectroscopies.The spectra show several sharp emission bands ranging from 450 to 750 nm due to the 4f– 4f transition from the excited state 5D0 to the low-lying multiple level 7FJ (J = 0, 1, 2, 3 and 4) of the Eu3+ ion. The five main sharp emission peaks were observed at wavelengths of c.a. 579, 591, 613, 653 and 702 nm, which are attributed to the f–f electronic transitions of the Eu(III) ion (5D0 → 7F0, 5D0 → 7F1, 5D0 → 7F2, 5D0 → 7F3 and 5D0 → 7F4, respectively). These complexes were evaluated also in terms of high energy.VUV-UV emission spectra present the 5D0→7F2 the transition dominating the spectrum under excitation at higher energies (Fig.1).