Spectroscopic investigation of europium benzoate in acetonitrile: Luminescence enhancement and complexation studies

- Luminescence and complexation of Eu3+-BA have been studied in MeCN.
- The luminescence intensity of Eu3+-BA is 320 times more in MeCN compared to aqueous medium.
- Luminescence enhancement is a result of sensitization and reduction in non-radiative decay channels in MeCN.
- Eu3+ forms only ML3 type complex with BA in MeCN contrary to aqueous medium where it forms ML and ML2 type species.

Luminescence from Eu3+ complexed with benzoic acid (BA) has been studied using acetonitrile (MeCN) as solvent. More than two orders luminescence enhancement is found as compared to Eu3+-BA complex in aqueous medium. The lifetime of Eu3+ in this complex is 900 μs which is much higher as compared to 118 μs in aqueous medium, suggesting the luminescence enhancement is a result of reduction in non-radiative decay channels in MeCN medium. Luminescence spectroscopy along with UV-vis spectroscopy is used to study the complexation behavior of Eu3+-BA in this medium. In contrary to aqueous medium where Eu3+-BA forms ML and ML2 type species, spectroscopic data reveal formation of only ML3 complex with composition Eu(BA)3(MeCN)6 in MeCN medium. Absorbance, luminescence lifetimes and the ratio of areas of 615-592 nm peaks are used in HypSpec computation program to determine the log β for the ML3 complex.