Synthesis, Luminescence Properties of Eu (III) and Tb (III) Complexes with a Polyamine Polycarboxylic Ligand as well as Their Binding Characteristics with Bovine Serum Albumin (BSA)

Abstract

A novel polyamine polycarboxylic ligand (L) with imidazole and pyridyl moieties and its corresponding complexes Na3EuLCl3·6H2O and Na3TbLCl3·6H2O, on to which Eu(III) and Tb(III) were bound via coordination, were prepared and characterized by FT-IR, 1HNMR, TG-DTA and CHN elemental analysis. The thermogravimetric analysis shows the Eu (III) and Tb(III) complexes have good thermal stabilities with decomposition temperatures 380 and 398°C, respectively. The luminescence properties of the complexes show the ligand has excellent antenna effect to sensitize the lanthanide ions while using ethyl p-dimethylaminobenzoate in ethanol as reference sample, the quantum efficiency of the Eu(III) and Tb(III) complexes are 0.264 and 0.280 in the DMSO at room temperature, respectively. The interactions of the complexes with bovine serum albumin (BSA) were analyzed by fluorescence measurements under physiological conditions. The UV–vis absorbance and the Stern-Volmer analysis indicate that the main quenching mechanism of BSA by the complexes is a static quenching procedure. The binding constants, binding site number at different temperatures were calculated by Van't Hoff equation, which confirms that the Van der Waals and hydrogen bond interactions are mainly impulse to the formation of complexes BSA-L coordination compound. Furthermore, the effect of complex on the conformation of BSA was analyzed according to synchronous fluorescence and circular dichroism (CD) spectra.