Complexation of Eu(III) with furan monocarboxylates in aqueous medium at variable temperatures: Luminescence and computational studies

Abstract

Luminescence of Eu(III) with furan monocarboxylates (FCA) ligands namely, 2 furoate (2FCA) and 3 furoate (3FCA) have been studied in aqueous medium. Both the ligands sensitized the luminescence of Eu(III) to a different extent. The magnitude of luminescence intensity was higher for the Eu(III)-2FCA than Eu(III)-3FCA complex due to the higher absorbance of 2FCA ligand as corroborated by UV–Vis spectroscopy. The formation of 1:1 Eu(III) complexes with both the ligands was confirmed through luminescence lifetime measurements. Stability constants of these complexes, calculated using HypSpec computation program were found to increase with temperature. The coordination mode of both the ligands was found to be monodentate. Van't Hoff equation was used to calculate enthalpy of formation of Eu(III) complexes using stability constants at different temperatures (283, 298, 313, 328, 343 K). The enthalpy of complex formation of 2FCA and 3FCA with Eu(III) was endothermic. Density functional theory (DFT) and time dependent (TD)-DFT calculations were performed to corroborate experimental observations.