A single-stranded {Gd18} nanowheel with a symmetric polydentate diacylhydrazone ligand.

An unprecedented {Gd18} nanowheel was solvothermally synthesized with a novel diacylhydrazone ligand. It features a rare single-stranded skeleton just like a Reuleaux triangle with vertices buckled in, represents the highest nuclearity and largest size in lanthanide (Ln) wheels reported so far, and shows a large magnetocaloric effect (MCE).