Abstract
Solvent-free mechanochemistry enables reactivity and selectivity, which are difficult to achieve in solution, particularly for poorly soluble polycyclic aromatic hydrocarbons. Here we describe a mechanochemical radical-chain C(sp³)–C(sp²) coupling between benzyl halides and unactivated arenes that proceeds with high regioselectivity across a broad range of polycyclic aromatic hydrocarbons and enables direct post-functionalization of poly(N‑vinylcarbazole). Spin-trapping and radical-clock experiments support the in situ generation of benzyl radicals during milling and a radical-chain propagation manifold. To provide a qualitative physical picture for force-assisted C–I homolysis, we introduce an atom-probe computational model in which controlled compressive distortion increases the diradical character and destabilizes benzyl iodides, consistent with mechanoradical formation under milling. A coupling product further serves as a precursor for on-surface synthesis, and an unexpected nanographene isomer was found, highlighting the synergy between mechanochemistry and atomically precise nanocarbon synthesis. Collectively, this work provides a prime example that mechanoradicals, often considered detrimental in material design, can be harnessed for constructive and highly selective C–C bond coupling in the solid state.
Fangzi Liu
Visiting PhD Student
