2D Ionic Liquid‐Like State of Charged Rare‐Earth Clusters on a Metal Surface

Abstract Rare‐earth complexes are vital for separation chemistry and useful in many advanced applications including emission and energy upconversion. Here, 2D rare‐earth clusters having net charges are formed on a metal surface, enabling investigations of their structural and electronic properties on a one‐cluster‐at‐a‐time basis using scanning tunneling microscopy. While these ionic complexes are highly mobile on the surface at ≈100 K, their mobility is greatly reduced at 5 K and reveals stable and self‐limiting clusters. In each cluster, a pair of charged rare‐earth complexes formed by electrostatic and dispersive interactions act as a basic unit, and the clusters are chiral. Unlike other non‐ionic molecular clusters formed on the surfaces, these rare‐earth clusters show mechanical stability. Moreover, their high mobility on the surface suggests that they are in a 2D liquid‐like state.