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Updated: Jul 28, 2025

Photogeneration of N-Heterocyclic Carbenes: Application in Photoinduced Ring-Opening Metathesis Polymerization
Published on: November 29, 2018
Quantum chain amplification in nanocrystalline Dewar benzenes by intramolecular sensitization
Edris Rivera1, Indrajit Paul1, Javier Fajardo1
1Department of Chemistry and Biochemistry, University of California Los Angeles CA 90095-1560 USA mgg@chem.ucla.edu.
Abstract:
Quantum chain reactions are characterized by the formation of several photoproducts per photon absorbed (ΦQC > 1) and constitute a promising signal amplification mechanism. The triplet-sensitized isomerization of Dewar benzene is known to undergo quantum chain reactions characterized by an adiabatic valence-bond isomerization to the excited state of Hückel benzene, which is able to transfer its triplet energy to a new ground state Dewar benzene that reacts to continue the chain. Given that diffusion-mediated energy transfer is the chain-limiting event in solution, we demonstrate here that reactions in crystals are significantly more efficient by taking advantage of energy transfer by a presumed exciton delocalization mechanism. Using Dewar benzenes with covalently attached, high energy triplet sensitizers we have demonstrated the efficiency of the solid state by the amplification of a quantum yield of ca. ΦQC ≈ 76 in acetonitrile solution to as much as ca. ΦQC ≈ 100-120 in submicron size specimens prepared by the re-precipitation method, and up to ca. ΦQC ≈ 300 with microcrystalline powders suspended in water.
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