Triplet exciton–mediated quantum chain using mixed crystals with a tailor-made triplet sensitizer

The phenomenon of triplet-sensitized quantum chain amplification in crystalline solids represents a significant advancement in the field of photochemistry and materials science. This process involves the generation and propagation of triplet excitons within a crystalline lattice, leading to a cascade of energy transfer events that amplify the initial photonic input. To that end, we have used the adiabatic valence-bond isomerization of a Dewar benzene (DB) to its corresponding Hückel benzene isomer in mixed crystals grown with a tailor-made sensitizer to establish that a triplet exciton carrier leads to quantum chain reactions where every photon results in up to 517 product molecules (Φ ≈ 517), with as little as 0.1% of the triplet sensitizer. By contrast, isomorphous crystals of the DB diacid lacking a triplet sensitizer showed a less impressive quantum yield of ca. Φ ≈ 22. Mixed crystals designed for this study are based on the use of isomorphous ionic auxiliaries both as crystal engineering handles and as triplet sensitizers. By leveraging the inherent structural order and long-range interactions present in crystalline solids, this mechanism enables efficient energy harvesting and conversion, with potential applications in photovoltaics, light-emitting diodes, and quantum information processing.