Strong Coupling with Light Enhances the Photoisomerization Quantum Yield of Azobenzene

doi:10.1016/j.chempr.2019.11.001

Chem

Volume 6, Issue 1, 9 January 2020, Pages 250-265

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Highlights

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Simulation of a realistic polaritonic chemistry reaction in a realistic setup
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Enhanced quantum yield predicted for azobenzene photoisomerization
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Conditions to observe such enhancements are identified
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Mechanism requires the high complexity of the atomistic dynamics of the system

The Bigger Picture

Strong coupling between molecules and light can be achieved in resonant cavities, giving rise to hybrid light-molecule states (polaritons). Chemistry in such states is different than the original photochemistry of the molecule. As such, polaritonic chemistry is emerging as a non-conventional approach to manipulate photochemical reactions, toward, for example, increasing reaction specificity or enhancing yields. Using accurate quantum chemistry multiscale simulations, we find that strong coupling can lead to enhanced photoisomerization yields for azobenzene in a realistic nanoplasmonic setup. Strong coupling acts on the motion of azobenzene atoms in the multi-dimensional space of internal coordinates, steering them away from unreactive pathways accessible instead in the traditional regimen. Our results show that the chemical complexity of molecules, rather than being a foe, can be turned into a friend in the strong coupling regimen, endowing polaritonic chemistry of additional potentialities.

Summary

The strong coupling between molecules and photons in resonant cavities offers a new toolbox to manipulate photochemical reactions. Although the quenching of photochemical reactions in the strong coupling regimen has been demonstrated before, their enhancement has proven to be more elusive. Here, by means of a state-of-the-art approach, we show how the trans $\to$ cis photoisomerization quantum yield of azobenzene embedded in a realistic environment can be higher in polaritonic conditions than in the cavity-free case. We characterize the mechanism leading to such enhancement and discuss the conditions to push the photostationary state toward the unfavored reaction product. Our results provide a signature that the control of photochemical reactions through strong coupling can be extended from selective quenching to improvement of the quantum yields.

Graphical Abstract

Keywords

polaritonic chemistry

photochemistry

strong coupling

nanocavities

azobenzene

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