Synthesis, luminescence properties of a novel aromatic carboxylic acid (L) and corresponding Eu(III) and Tb(III) compounds as well as the binding characteristics of L with bovine serum albumin (BSA)

A novel polyamino polycarboxylic pyridine derivative ligand, N,N,N1,N1-(2,6-bis((3-(aminoethyl)-5-methyl-1H-pyrazol-1-yl)methyl)pyridine)hexakis(acetic acid) (L), was designed and synthesized with the motive that it is able to sensitize the emission of lanthanides. Its corresponding Eu(III) and Tb(III) complexes Na4EuLCl3·3H2O and Na4TbLCl3·5H2O were successfully prepared. The ligand and the complexes were characterized by elemental analysis, IR, MS, NMR and TG–DTA. The luminescence properties of the compounds in solid state were investigated; each complex had very narrow emission bands and strong luminescence intensity up to about 10,000. The TG–DTA studies showed that the initial decomposition temperature of both complexes was over 250 °C, elucidating the complexes had a high thermal stability. Meanwhile, the comparison with similar complexes suggested that the ligand with more coordination sites possessed more efficient antenna effect. To explore the potential medicinal value of L, the binding interaction of L and bovine serum albumin (BSA) was carried out by fluorescence spectrum. The studies indicated that the reaction between L and BSA was a static quenching procedure. The binding site number n and binding constant Ka were calculated according to the double logarithm regression equation. The thermodynamic parameters showed the Van der Waals and hydrogen bond interactions were the mainly impulse to the reaction.

Graphical abstractA novel polyamino polycarboxylic pyridine derivate ligand and its corresponding Eu(III) and Tb(III) complexes Na4EuLCl3·3H2O and Na4TbLCl3·5H2O were successfully prepared. And the luminescence properties of the complexes in solid state were investigated. Furthermore, the binding characteristics of L with bovine serum albumin (BSA) was carried out.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► A novel polyamino polycarboxylic pyridine derivative ligand (L) with more coordination sites was designed and synthesized successfully. ► The ligand owned a strong ability to sensitize the emission of lanthanides. ► L could cause the fluorescence quenching of BSA, changing the structures of protein accordingly, which is the theoretical basis of the potential medicinal value of the ligand L.