Reaction amplification with a gain: Triplet exciton-mediated quantum chain using mixed crystals with a tailor-made triplet sensitizer

From Beam Damage to Massive Reaction Amplification under the Electron Microscope: An Ionization-Induced Chain Reaction in Crystals of a Dewar Benzene

Electron microscopy in its various forms is one of the most powerful imaging and structural elucidation methods in nanotechnology where sample information is generally limited by random chemical and structural damage. Here we show how a well-selected chemical probe can be used to transform indiscriminate chemical damage into clean chemical processes that can be used to characterize some aspects of the interactions between high-energy electron beams and soft organic matter. Crystals of a Dewar benzene exposed to a 300 keV electron beam facilitate a clean valence-bond isomerization radical-cation chain reaction where the number of chemical events per incident electron is amplified by a factor of up to ca. 90,000.

Cascade Photoreaction in Crystals: A Phase Change Caused by a Dewar Benzene Quantum Chain Triggers a Topochemical [2 + 2] Photodimerization

Crystals undergoing tandem reactions where the first transformation enables the second one are rare. Using photoreactive Dewar benzene 3,4,5,6-tetramethyl-1,2-dicarboxylic diacid (DB) as a hydrogen-bonding template for the [2π+2π] photodimerization of trans-4,4'-bipyridyl-ethenes (BPE), we obtained crystals DB-BPE-NT with a DB:BPE = 2:1 stoichiometry with double bonds at a nonreactive distance of 5.957 Å. Exposure to UV light resulted in valence bond isomerization to Hückel benzene 3,4,5,6-tetramethyl-1,2-dicarboxylic acid (HB) by a quantum chain reaction that triggered the sought-after topochemical [2π+2π] photodimerization reaction. Notably, crystals HB:BPE-T with the Hückel benzene isomer and BPE adopted a 2:2 stoichiometry and displayed an efficient topochemically templated photodimerization reaction.