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.
Synthesis and characterization of quinoline-derivated fluorescent
sol–gel-imprinted polymer as a chemosensor for sensing of uranyl ion
In this work, chemosensor that contains 3-aminoquinoline derivative of silane coupling agent grafted to the sol–gel polymer has been synthesized and characterized for determination of the uranyl, $$UO_2^{2 + }$$UO22+ion. The quinoline-based fluorescence probe was covalently anchored to the surface of sol–gel polymer by a simple one-step procedure.The sol–gel polymer was characterized by FTIR spectroscopy, N2 adsorption–desorption analysis, scanning electron microscope, particle size distribution, and optical microscope by comparing with ion-imprinted sol–gel polymer obtained in the presence of $$UO_2^{2 + }$$UO22+ion. Surface area, pore volume, and diameter were analyzed from the profile of nitrogen adsorption. Conductometric and potentiometric titrations were carried out to evaluate the active concentration of functional precursor immobilizedwithin the sol–gel matrix. The pH-dependent fluorescence behavior of sol–gel polymer both in the absence and presence of $$UO_2^{2 + }$$UO22+ ion was elucidated to optimizethe conditions for the sensing of $$UO_2^{2 + }$$UO22+ion in aqueous solution. The chemosensor exhibits singlefluorescence emission belonging to quinoline group in sol–gel polymer,whereas it demonstrates dual emission in the presence of $$UO_2^{2 + }$$UO22+ion. It was observed that the peak belonging quinoline group was quenched while the peak at longer wavelength enhanced upon interaction with $$UO_2^{2 + }$$UO22+ion.Graphical Abstract
Synthesis of 2,4-dideoxy-.beta.-D-erythro-hexopyranosyl nucleosides
The synthesis of 1-(2,4-dideoxy-β-D-erythro-hexopyranosyl)thymine (12) 1 was accomplished using two different synthetic routes. It was obtained starting either from 1,2:5,6-di-O-isopropylidene-α-D-glucofuranose or from tri-O-acetyl-D-glucal. The other modified nucleosides, with either a cytosine, guanine, or adenine moiety, were synthesized using the second reaction scheme. Deoxygenation reactions were accomplished with the (2,4-dichlorophenoxy)thiocarbonyl derivatives generated in situ