New Luminescent Bioprobes Eu(lll)-phloroglucinol Derivatives and Their Spectrofluorimetric, Electrochemical Interactions with Nucleotides and DNA

Two new ligands derived from phloroglucinol 2-{(4-methoxy benzoyl ) oxy ] } methyl benzoic acidL1] and 2-{(4-methyl benzoyl )oxy] methyl} benzoic acidL2] were synthesized. The solid complex Eu(III)-L2 has been synthesised and characterized by elemental analysis ,UV and IR spectra. The reaction of Eu(III) with the two synthesized ligands has been investigated in I = 0.1 mol dm^-3 p-toluene sulfonate by cyclic voltammetry and square wave voltammetry. The reaction of Eu (III)–L1 and Eu (III)–L2 binary complexes with nucleotide 5′-AMP , 5′-ADP ,5′-ATP , 5′- GMP , 5′-IMP , and 5′-CMP has been investigated using UV, fluorescence and electrochemical methods. The experimental conditions were selected such that self-association of the nucleotides and their complexes was negligibly small, that is, the monomeric complexes were studied. The interaction of the Eu(III)–L1 or L 2 solid complexes with calf-thymus DNA has been investigated by fluorescence and electrochemical methods including cyclic voltammetery(CV) ,differential pulse polarography (DPP) and square wave voltammetry (SWV) on a glassy carbon electrode. The fluorescence intensity of Eu(III)-L2 complex was enhanced with the addition of DNA. Under optimal conditions in phosphate buffer pH 7.0 at 25 °C the linear range is 3–20 μM for calf thymus DNA (CT–DNA) and the corresponding determination limit is 1.8 μM.