Tb3+ and Eu3+ luminescence in imidazolium ionic liquids

The luminescence properties of Tb3+ and Eu3+ dissolved in ionic liquids are studied. Solutes in this study include simple lanthanide compounds (e.g., EuBr3, TbCl3) and lanthanide complexes (e.g., Eu(dpa)33- where dpa = 2,6 pyridine dicarboxylate dianion) dissolved in a 1-butyl-3-methylimidazolium bromide(BMIBr)/water mixture. Emission, excitation, and time-resolved emission measurements are utilized to characterize the spectroscopic properties. It is well established in the literature that the solubility and spectroscopic properties of lanthanides in ionic liquids are highly dependent upon environmental factors including purity, and water content [K. Binnemans, Chemical Reviews (2007); I. Billard, S. Mekki, C. Gaillard, P. Hesemann, C. Mariet, G. Moutiers, A. Labet, J.-C.G. Buenzli, European Journal of Inorganic Chemistry 6 (2004) 1190-1197; S. Samikkanu, K. Mellem, M. Berry, P.S. May, Inorganic Chemistry 46 (2007) 7121-7128]. The water in this ionic liquid system acts as a co-solvent to facilitate solubility of Tb3+ and Eu3+ compounds. The observed spectroscopic properties of Eu3+ and Tb3+ salts are expectedly impacted by the high water content, but unexpectedly impacted by the BMIBr ionic liquid. However, the spectroscopy of Eu(dpa)33- is unaffected by the presence of BMIBr.