Single-molecule magnets (SMMs) display magnetic hysteresis that is molecular in origin, and these materials have huge potential to be developed as nano-scale devices. The big challenge is to create SMMs that function without the need for liquid-helium cooling.This project will develop new SMMs that combine the strong magnetic anisotropy of lanthanide ions with a series of novel radical ligands. Our innovative SMMs will have controllable molecular and electronic structures, which will ultimately enable hysteresis at unprecedented temperatures.Highly unusual di- and tri-metallic Ln-SMMs are proposed in which the metals are bridged by radicals with heavy Group 15 (phosphorus-bismuth) and Group 16 (sulphur-tellurium) donor atoms. Trimetallic SMMs will also be based on hexaazatriphenylene (HAT) radicals, and dimetallic SMMs will also be based on nindigo radicals, both of which are nitrogen-donor ligands.The SMM field is dominated by systems with diamagnetic ligands. Our radical ligands have never been used in SMM studies: their diffuse unpaired spin provides a way of switching off the quantum tunnelling mechanisms that otherwise prevent hysteresis. We will exploit the rich electrochemistry of the target ligands: heavy p-block radicals have huge spin densities on the donor atoms; HAT radicals can have up to three unpaired electrons; reduced or oxidized nindigo radicals allow access to redox-switchable SMMs. In the HAT-bridged SMMs, the use of ligands with more than one unpaired electron is unprecedented. The heavy p-block ligands are themselves are novel.The PI’s approach to SMMs has already established new directions in lanthanide chemistry and in molecular magnetism. He now proposes a new, radical approach to SMMs with potential to re-define the state of the art, and to extend the frontiers of a vibrant multi-disciplinary field. Achieving the aims will provide a major step towards using SMMs for applications at practical temperatures.