posted on 2024-02-22, 22:33authored bySamuel G. Dunning, Wan Si Tang, Bo Chen, Li Zhu, George D. Cody, Stella Chariton, Vitali B. Prakapenka, Timothy A. Strobel
Compression of small molecules can induce solid-state
reactions
that are difficult or impossible under conventional, solution-phase
conditions. Of particular interest is the topochemical-like reaction
of arenes to produce polymeric nanomaterials. However, high reaction
onset pressures and poor selectivity remain significant challenges.
Herein, the incorporation of electron-withdrawing and -donating groups
into π-stacked arenes is proposed as a strategy to reduce reaction
barriers to cycloaddition and onset pressures. Nevertheless, competing
side-chain reactions between functional groups represent alternative
viable pathways. For the case of a diaminobenzene:tetracyanobenzene
cocrystal, amidine formation between amine and cyano groups occurs
prior to cycloaddition with an onset pressure near 9 GPa, as determined
using vibrational spectroscopy, X-ray diffraction, and first-principles
calculations. This work demonstrates that reduced-barrier cycloaddition
reactions are theoretically possible via strategic functionalization;
however, the incorporation of pendant groups may enable alternative
reaction pathways. Controlled reactions between pendant groups represent
an additional strategy for producing unique polymeric nanomaterials.