Spectroscopic investigation of uranium supermolecules with octaacetatecalix[8}arene as ligand

Abstract

The uranyl compounds (UO,””) present a great potential as luminescent materials. for instance, applied in technology laser. luminescent probes. cells for conversion of energy. etc. In this work it is reported synthesis. characterization and luminescent properties of the supermolecules of U0, and octaacetatecalix[8]arene. These compounds were characterized by complexation analyses for determining the U® concentration. infrared spectra. absorption in UV-VIS and luminescence spectroscopy. The results agree with the following composition UOxMS).coctaacetate calix[8Jarene and UO,(TFA}eoctaacetate calix[8]arene (where MS is methane sulfonate and TFA is trifluoroacetate). The IR data show the coordination of counter ion and the inclusion into calixarene cavity. The Juminescence spectra present the characteristic bands of the uranyl ion, attributed to the *TI,—+'Eg+ transition. The emission spectrum of the supermolecule with MS recorded under excitation at 400 nm presents narrow bands different from that obtained with excitation at 255 nm that exhibits broaden bands. On the other hand. the emission spectra of the trifluoroacetate supermolecule system Show identical profile under both excitation energies. Besides. it was observed a $hifting of the bands in the emission spectra (o shorter wavelengths for the precursor complexes as compared with those supermolecules system. The luminescence decay curves exhibit a mono-exponential behaviour presenting the lifetime for the UO,(MS)2 octaacetatecalix[8Jarene (T = 413 ys) higher than for the UO;(TFA)..octaacetatecalix[8Jarene (T= 168 ps).