Solvation-controlled emission of divalent europium salts

[Display omitted] •Solvation of divalent europium salts by tetrahydrofuran (THF) and dimethoxyethane (DME) leads to shift in emission maximum.•In general emission observed from DME solution is red shifted compare to that of THF.•Effect of solvation is marginal in absorption spectra.•Time dependent density functional theory indicated similar orbital transitions are involved in both the solvents.•An additional relaxation mechanism such as change in geometry in the excited is responsible for red shifted emission in DME. Coordination-environment-dependent tuning of luminescence of divalent europium is an emerging topic of research. While it has been extensively demonstrated in the solid state, recent reports indicate similar findings in solution, where emission properties were tuned by altering different ligands and counter anions. In the present study, we demonstrate that differences in solvation shells alter the luminescence properties of divalent europium. Steady-state emission measurements indicate that the emission maxima of EuII salts in dimethoxyethane is red-shifted compared to the maxima in tetrahydrofuran. This shifting was confirmed with three different EuII salts: EuI2, EuBr2, and Eu(OTf)2. UV–visible spectroscopic measurements indicate a marginal difference in absorption spectra of EuII salts in tetrahydrofuran and dimethoxyethane, ruling out the possibility that a difference in ground-state geometry is responsible for the solvation-induced emission shift. Time-dependent density functional theory studies further support this conclusion. Relaxation of the excited state in dimethoxyethane is a postulated mechanism behind the red-shifted emission. The current study demonstrates a straight-forward path toward tuning the emission properties of EuII without altering light absorption.