Strong light-matter coupling as a photonic substituent: cavity-induced electronic and structural control of regioselectivity in nitrobenzene.

Abstract

Strong coupling to the vacuum electromagnetic field of optical cavities has been proposed as a route to control ground-state chemical reactivity, enabling "photonic substituent effects." Recent theoretical work predicted that cavity coupling can invert intrinsic regioselectivity in electrophilic aromatic substitution in nitrobenzene. Here, we revisit this prediction using correlated ab initio cavity quantum electrodynamics. Using cavity-constrained QED-DFT geometry relaxations followed by QED-CCSD(2,2) calculations of the Wheland intermediates, we confirm substantial energetic reordering and predict a para-meta stabilization more than twice the previously reported estimate, which was based on geometries relaxed in the absence of cavity coupling. QED-DMRG analysis shows that the ortho stabilization effect arises from cavity-induced reweighting of resonance structures, reinforcing the idea of a photonic substituent effect that is as influential on molecular electronic structure as chemical substituents. Complementary ab initio molecular dynamics simulations driven by QED-DFT analytic gradients reveal that orientational dynamics may be strongly biased toward configurations that stabilize ortho and para intermediates, introducing a dynamical gating mechanism that can shift the canonical meta selectivity toward ortho or para electrophilic aromatic substitution products.

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