Luminescence and Nanoheterogeneity in Manganese-Containing Ionic Liquid Mixtures

The luminescence properties of single-component and binary ionic liquids (ILs) were investigated in relation to their nanoheterogeneities. The cations of the ILs were 1-alkyl-3-methylimidazolium and trihexyl(tetradecyl)phosphonium ([P666,14]⁺). The anions were [Cl]^-, [Br]^-, [MnCl₄]^2-, and [MnBr₄]^2-. Even in the liquid state, the binary mixtures of η[P666,14][Br] + [P666,14]₂[MnBr₄] (η = 0.5, 1, 2, and 4) emitted green light at room temperature. In the mixed liquids, the prepeak derived from the nanoheterogeneity was observed at a low Q position on the small- and wide-angle X-ray scattering patterns. With increasing temperature, the luminescent intensities of the IL mixtures increased, contrary to the almost constant prepeak intensity. The luminescence intensity maximum of the mixture (η = 0.5) was observed at 403 K.