Facile Preparation Methods for Triarylmethyl‐Type Stable Luminescent Diradicals and Higher Multiradicals

Stable luminescent multiradicals are photophysically very attractive materials as well as stable luminescent monoradicals due to their complex spin‐multiplicity states or intramolecular electronic and magnetic interactions. This concept article highlights synthetic advances in triarylmethyl‐type stable luminescent radicals, emphasizing methods to construct diradical, triradical, and multiradical systems. These radicals are prepared from triarylmethane precursors via deprotonation, followed by oxidation. The initial synthesis of perchlorinated triphenylmethanes through the BMC methodology (S 2 Cl 2 and AlCl 3 in SO 2 Cl 2 ) chlorination led to perchlorinated Chichibabin diradical. Friedel–Crafts reactions have been widely employed to produce various halogenated triphenylmethanes, which serve as versatile platforms for further functionalization. Incorporation of pyridine rings into the triarylmethyl core enables the formation of coordination systems with multiple radical ligands. Coupling reactions play an important role in expanding these radical frameworks. Direct substitution to the tris(2,4,6‐trichlorophenyl)methyl radical allows for the introduction of N ‐donor groups, creating donor–acceptor luminescent radicals and acceptor–donor–acceptor luminescent diradicals. Pd‐catalyzed couplings enable the functionalization of halogenated triarylmethanes, facilitating their dimerization, trimerization, and other complex architectures. The development of triarylmethane‐based boronic acids and esters has further expanded the synthetic scope, overcoming previous limitations and opening new pathways to stable luminescent diradicals.