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 acid[L1] and 2-{[(4-methyl benzoyl)oxy] methyl} benzoic acid[L2] 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 L2 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.