A new series of liquid rare earth chlorometallate complexes featuring the alkyl-phosphonium cation [P666 14](+) has been created and studied in detail.
EXAFS analysis showed that the [LnCl6](3-) ion is the main form in these liquids for elements like Nd, Eu, and Dy.
The luminescence properties revealed visible light emissions for Tb, Eu, Pr, and Sm, plus near-infrared emissions for Nd and Er, with effective magnetic moments measured for several rare earth samples.
A series of novel, phosphine oxide functionalised ionic liquids have been synthesised and their application as tuneable lanthanide complexing agents is demonstrated.