Photophysics of Perylene Diimide Dianions and Their Application in Photoredox Catalysis

Abstract

The two-electron reduced forms of perylene diimides (PDIs) are luminescent closed-shell species whose photochemical properties seem underexplored. Our proof-of-concept study demonstrates that straightforward(single) excitation of PDI dianions with green photons provides an excited state that is similarly or more reducing than the muchshorter-lived excited states of PDI radical monoanions,w hicha re typically accessible after biphotonic excitation with blue photons. Thermodynamically demanding photocatalytic reductive dehalogenations and reductive CÀOb ond cleavage reactions of lignin model compounds have been performed using sodium dithionite acts as ar eductant, either in aqueous solution or in biphasic water-acetonitrile mixtures in the presence of aphase transfer reagent. Our work illustrates the concept of multielectron reduction of ap hotocatalyst by as acrificial reagent prior to irradiation with low-energy photons as am eans of generating very reactive excited states.

Visible Light Generation of a Microsecond Long-Lived Potent Reducing Agent

“…Previously reported reductants and ZrO 2 (e – )|PDI (red star) lifetime versus reduction potential. ,,,,− ES is short for excited state.…”

“…Relative to PDI dissolved in DMF, the spectrum of ZrO 2 |PDI was broadened with a change in relative intensities attributed to intermolecular PDI–PDI interactions and surface heterogeneity . Chemical reduction of ZrO 2 |PDI by tetrakis­(dimethylamino)­ethylene (TDAE) resulted in the appearance of new absorption features in the red and near-infrared regions with maintenance of an isosbestic point at 545 nm that were attributed to the formation of the reduced PDI, abbreviated as ZrO 2 |PDI •– , Figure S3.…”

“…Indeed, mesoporous thin films of ZrO 2 nanoparticles have previously been utilized as reference materials for dyesensitization studies when characterization of excited states was desired without complications from interfacial electron transfer. 17,18 We discovered that visible light excitation of ZrO 2 |PDI •− yielded a charge separated state, denoted as ZrO 2 (e − )|PDI, that has a stellar long lifetime of over ten microseconds while still maintaining a reduction potential more negative than −2.4 V vs the saturated calomel electrode Relative to PDI dissolved in DMF, the spectrum of ZrO 2 | PDI was broadened with a change in relative intensities attributed to intermolecular PDI−PDI interactions 19 and surface heterogeneity. 20 Chemical reduction of ZrO 2 |PDI by tetrakis(dimethylamino)ethylene (TDAE) resulted in the appearance of new absorption features in the red and nearinfrared regions with maintenance of an isosbestic point at 545 nm that were attributed to the formation of the reduced PDI, abbreviated as ZrO 2 |PDI •− , Figure S3.…”

Diazazethrene bisimide: a strongly electron-accepting π-system synthesizedviathe incorporation of both imide substituents and imine-type nitrogen atoms into zethrene

“…The extremely deep-lying LUMO level of DAZBI encouraged us to isolate its reduced species. Radical anions and dianions that are easy to handle are currently attractive targets as materials in photochemical reactions, 14,39,40 rechargeable batteries, 41 and photodynamic therapy. 7 The reaction of 8a with 2.5 equiv of cobaltocene (CoCp 2 ) in CH 2 Cl 2 at room temperature afforded the corresponding dianion 13 in 70% yield as a green solid (Scheme 2a).…”

Development of Carbazole-Cored Organo-Photocatalyst for Visible Light-Driven Reductive Pinacol/Imino-Pinacol Coupling

“…), supramolecules, organic dyes, and polyaromatic compounds (perylene, benzo­[ g,h,i ]­perylene, phenoxazine, etc.) as photocatalysts. , Moreover, the higher cost of noble metal photocatalysts and lower efficacy of organic dyes set the stage to develop more efficient and readily accessible organo-photoredox catalysts (Scheme ).…”