Affiliation:
1. Department of Chemistry and Biochemistry, University of California, Los Angeles, CA 90024-1569
Abstract
Photochemical valence bond isomerization of a crystalline Dewar benzene (
DB
) diacid monoanion salt with an acetophenone-linked piperazinium cation that serves as an intramolecular triplet energy sensitizer (
DB-AcPh-Pz
) exhibits a quantum chain reaction with as many as 450 product molecules per photon absorbed (Φ ≈ 450). By contrast, isomorphous crystals of the
DB
diacid monosalt of an ethylbenzene-linked piperazinium (
DB-EtPh-Pz
) lacking a triplet sensitizer showed a less impressive quantum yield of ca. Φ ≈ 22. To establish the critical importance of a triplet excited state carrier in the adiabatic photochemical reaction we prepared mixed crystals with
DB-AcPh-Pz
as a dilute triplet sensitizer guest in crystals of
DB-EtPh-Pz
. As expected from their high structural similarities, solid solutions were easily formed with the triplet sensitizer salt in the range of 0.1 to 10%. Experiments carried out under conditions where light is absorbed by the triplet sensitizer-linked
DB-AcPh-Pz
can be used to initiate a triplet state adiabatic reaction from
3
DB-AcPh-Pz
to
3
HB*-AcPh-Pz
, which can serve as a chain carrier and transfer energy to an unreacted
DB-EtPh-Pz
where exciton delocalization in the crystalline solid solution can help carry out an efficient energy transfer and enable a quantum chain employing the photoproduct as a triplet chain carrier. Excitation of mixed crystals with as little as 0.1% triplet sensitizer resulted in an extraordinarily high quantum yield Φ ≈ 517.
Funder
National Science Foundation
Publisher
Proceedings of the National Academy of Sciences
Cited by
1 articles.
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1. QnAs with Miguel A. Garcia-Garibay;Proceedings of the National Academy of Sciences;2024-04-03