Rare-earth (RE) elements are vital for high technological applications due to their typically large magnetic moments and signature optical transitions associated with the 4f electron shell.  In addition to considering single atoms or ions, one can study them inside coordination complexes, allowing for the design and synthesis of structures with desirable functions.  We study different complexes: from ions deposited on surfaces and explore their magnetic interactions to RE ionic clusters self-assembled on a gold crystal surface. Experiments on the ionic complexes find them highly mobile at ~100 K, indicating a liquid-like state. Their mobility is greatly reduced below 5K, revealing self-limiting clusters with RE complexes joined by electrostatic and molecular interactions.  We also study possible arrangements of RE ion chains and clusters on gold.  The magnetic ground state configurations are found to be dominated by magnetic anisotropy effects, which can be explored using scanning tunneling techniques to investigate spin-flip excitations. RE ion clusters can also be employed to analyze entanglement entropy and their signatures in differential conductance experiments.