Mixed-Halide Triphenyl Methyl Radicals for Site-Selective Functionalization and Polymerization

Derivatives of the stable, luminescent tris-2,4,6-trichlorophenylmethyl (TTM) radical exhibit unique doublet spin properties that are of interest for applications in optoelectronics, spintronics, and energy storage. However, the synthesis and variety of TTM-type donor-acceptor molecules with high quantum yields are limited by the symmetric chloride decoration and poor reactivity of chlorides in metal-catalyzed C-C cross-coupling reactions. Therefore, only few donor-acceptor molecules have been successfully coupled to the TTM radical motif. Here, we present a synthetic pathway to obtain mixed-halide derivatives of TTM, partly carrying bromo- instead of chloro-substituents, leading to improved reactivity and enabling site-specific cross-coupling reactions. These highly stable mixed-halide triphenyl methyl radicals represent a powerful tool to obtain complex, and so far inaccessible open-shell small molecules, as well as polymers.