Dual photochemistry of anthracene-9,10-endoperoxide studied by femtosecond spectroscopy

Abstract

The dual photochemistry of anthracene-9,10-endoperoxide (APO) was investigated in a fs UV pump-supercontinuum probe experiment, along with anthracene (AC) and anthraquinone (AQ) for comparison. Excitation of APO at 282 nm leads to 100% product formation by two competing photoreaction channels. Cycloreversion generates with a ∼25% quantum yield (QY) (1)O(2) and AC vibrationally excited in the singlet electronic ground state (hot AC). 1-2% of the AC is generated in the lowest triplet state, but no AC is generated in electronically excited singlet states. Generation and cooling of hot AC are modeled using solution phase and broadened gas-phase AC absorption spectra at various temperatures. Results indicate ultrafast generation of hot AC within 3 ps, much faster than reported before for derivatives of anthracene endoperoxide, and subsequent cooling with an 18 ps time constant. The homolytic O-O cleavage pathway generates a biradical, which converts into electronically excited diepoxide (DE). Our data indicate a 1.5 ps time constant that we tentatively assign to the biradical decay and DE formation. Cooling of DE in this electronically excited state takes place with a ∼21 ps time constant. Excitation of AQ at 266 nm is followed by an ultrafast population of the T(1)(nπ*) triplet state of AQ with a time constant of (160 ± 60) fs.

The Ugi Four‐Component Reaction Route to Photoinducible Electron‐Transfer Systems

“…Singlet excited 1 AQ* is known to undergo intersystem crossing to the triplet state 3 AQ* within a few hundred femtoseconds. [21] Both excited states lie energetically above the DIP states. We propose that a forward ET occurs in CHEMPLUSCHEM COMMUNICATIONS www.chempluschem.org competition with an intersystem crossing on a 100 fs timescale.…”

Surface energy gradient driven convection for generating nanoscale and microscale patterned polymer films using photosensitizers

“…A mechanism for anthracene endoperoxide radical intermediate formation by either thermal or photochemical decomposition was previously investigated by other groups . Based on their findings for our system, the photoexposure first produced DBA endoperoxide, which then decomposed to generate a biradical intermediate upon thermal annealing.…”

Mechanism of the O2(1Δg) generation from the Cl2/H2O2 basic aqueous solution explored by the combined ab initio calculation and nonadiabatic dynamics simulation

“…As for the photolysis, it is generally accepted that endoperoxides undergo cycloreversion reactions to release O 2 ( 1 Δ g ) with high yield, when they are populated in the ππ* singlet state upon UV irradiation . However, cleavage of the peroxidic bond was observed to be dominant primary pathway in a wide wavelength range from UV to visible light in the recent femtosecond UV pump probe experiments, which is supported by the combined electronic structure calculation and dynamic simulation …”