Disequilibrating azobenzenes by visible-light sensitization under confinement

The ability to photoswitch azobenzenes from their stable E isomer to the
metastable Z state is the basis of numerous applications of these
molecules. However, this reaction typically requires UV light, which
limits the applicability, particularly in biological settings. Here we
introduce DisEquilibration by Sensitization under Confinement (DESC), a
biomimetic approach to switch various azobenzenes using visible light of
desired color, including red. DESC relies on a combination of a
macrocyclic host and a photosensitizer, which act together to bind and
selectively sensitize E-azobenzenes. After switching to the Z isomer, the
azobenzene loses its affinity to—and is expelled from—the host, which can
convert additional copies of E into Z. In this way, the
host/photosensitizer complex acts as a light-driven supramolecular
machine, converting photon energy into chemical energy in the form of
out-of-equilibrium photostationary states, including ones that cannot be
accessed via direct photoexcitation.