Easily Accessible Rare-Earth-Containing Phosphonium Room-Temperature Ionic Liquids: EXAFS, Luminescence, and Magnetic Properties

A range of liquid rare earth chlorometallate complexes with the alkyl-phosphonium cation, [P<sub>666 14</sub>]<sup>+</sup>, has been synthesized and characterized. EXAFS confirmed the predominant liquid-state speciation of the [LnCl<sub>6</sub>]<sup>3–</sup> ion in the series with Ln = Nd, Eu, Dy. The crystal structure of the shorter-alkyl-chain cation analogue [P<sub>4444</sub>]<sup>+</sup> has been determined and exhibits a very large unit cell. The luminescence properties, with visible-light emissions of the liquid Tb, Eu, Pr, and Sm and the NIR emissions for the Nd and Er compounds, were determined. The effective magnetic moments were measured and fitted for the Nd, Tb, Ho, Dy, Gd, and Er samples.