Ligand sensitized luminescence of uranyl by benzoic acid in acetonitrile medium: a new luminescent uranyl benzoate specie.
Benzoic acid (BA) is shown to sensitize and enhance the luminescence of uranyl ion in acetonitrile medium. Luminescence spectra and especially UV-Vis spectroscopy studies reveal the formation of tri benzoate complex of uranyl i.e. [UO2(C6H5COO)3](-) which is highly luminescent. In particular, three sharp bands at 431, 443, 461nm of absorption spectra provides evidence for tri benzoate specie of uranyl in acetonitrile medium. The luminescence lifetime of uranyl in this complex is 68μs which is much more compared to the lifetime of uncomplexed uranyl (20μs) in acetonitrile medium. In contrary to aqueous medium where uranyl benzoate forms 1:1 and 1:2 species, spectroscopic data reveal formation of 1:3 complex in acetonitrile medium. Addition of water to acetonitrile results in decrease of luminescence intensity of this specie and the luminescence features implode at 20% (v/v) of water content. For the first time, to the best of our knowledge, the existence of [UO2(C6H5COO)3](-) specie in acetonitrile is reported. Mechanism of luminescence enhancement is discussed.
Synthetic, structural, and luminescence study of uranyl coordination polymers containing chelating terpyridine and trispyridyltriazine ligands
Seven uranyl coordination polymers [(UO2)(BrC8H3O4)(C15H11N3)] (1), [(UO2)(ClC8H3O4)(C15H11N3)] (2), [(UO2)(BrC8H3O4)(C18H12N6)]·H2O (3), [(UO2)(ClC8H3O4)(C18H12N6)]·2H2O (4), [(UO2)(C8H3IO4)(C18H12N6)]·2C3H7O (5), [(UO2)(C9H6O4)(C18H12N6)]·H2O (6), and [(UO2)(C6H2O4S)(C18H12N6)]·2H2O (7) containing N-donor ligands 2,2′:6′,2′′-terpyridine (TPY) and 2,4,6-tripyridyl s-triazine (TPTZ); and O-donor linkers thiophene 2,5-dicarboxylic acid (TDC) and X-1,4-benzene dicarboxylic acid (X-BDC, where X = Me, Cl, Br, I) were synthesized and characterized using single crystal X-ray diffraction (SC-XRD), powder X-ray diffraction (PXRD), and fluorescence spectroscopy. Each compound crystallizes as binuclear pseudo dimers containing a UO22+ pentagonal bipyramidal primary building unit. Fluorescence spectra of 1–4, and 6–7 show characteristic UO22+ emission whereas 5 is non-emissive. Red shifts within the emission of 1–4 are noted as a function of N-donor ligands TPY and TPTZ whereas emission shifts are not observed in TPTZ bearing compounds (3, 4, 6, 7) containing different O-donor linkers. Luminescent lifetimes of 1–7 were obtained and fitted with either bi-exponential or tri-exponential components.
Determination of Trace Terbium(III) Based on New Fluorescence Enhancement System of Terbium(III) with 1,7- bis- (2′-Carboxylphenyl)-1,4,7-trioxaheptane by Sodium Acetate in Dimethyl Sulfoxide
Abstract A new ligand; 1,7-bis-(2′-carboxylphenyl)-1,4,7-trioxaheptane (BCPTH), its fluorescence intensity with terbium(III) was increased by more than two orders of magnitude in the present of sodium acetate (NaAc) or hexamethylene tetramine (HMTM) solution. Following the addition of organic solvents to the above system leading to the Tb3+ fluorescence was further enhanced by about an order of magnitude. The enhancement was observed to be highest with NaAc and dimethyl sulfoxide (DMSO) solvent. The spectrofluorimetric determination of trace amount of Tb3+ based on the phenomenon was carried out. The excitation and emission wavelengths are 296 nm and 545 nm, respectively. Under optimal conditions, the fluorescence intensities vary linearly with the concentration of Tb3+ in the range 7.0 × 10−9 M–4.8 × 10−5 M with a detection limit of 5.0 × 10−9 M. The interferences of some rare-earth metals and other inorganic ions are described. The method is a selective, sensitive, rapid, and simple analytical procedure for the determination of terbium(III) in a high purity yttrium oxide and synthetic sample. The mechanism for the fluorescence enhancement was also studied.