title: Electrocatalytic Z → E Isomerization of Azobenzenes.
abstract: A variety of azobenzenes were synthesized to study the behavior of their E and Z isomers upon electrochemical reduction. Our results show that the radical anion of the Z isomer is able to rapidly isomerize to the corresponding E configured counterpart with a dramatically enhanced rate as compared to the neutral species. Due to a subsequent electron transfer from the formed E radical anion to the neutral Z starting material the overall transformation is catalytic in electrons; i.e., a substoichiometric amount of reduced species can isomerize the entire mixture. This pathway greatly increases the efficiency of (photo)switching while also allowing one to reach photostationary state compositions that are not restricted to the spectral separation of the individual azobenzene isomers and their quantum yields. In addition, activating this radical isomerization pathway with photoelectron transfer agents allows us to override the intrinsic properties of an azobenzene species by triggering the reverse isomerization direction (Z → E) by the same wavelength of light, which normally triggers E → Z isomerization. The behavior we report appears to be general, implying that the metastable isomer of a photoswitch can be isomerized to the more stable one catalytically upon reduction, permitting the optimization of azobenzene switching in new as well as indirect ways.
authors.affiliation: Department of Chemistry & IRIS Adlershof, Humboldt-Universität zu Berlin , Brook-Taylor-Strasse 2, 12489 Berlin, Germany.
authors.forename: Alexis
authors.initials: A
authors.lastname: Goulet-Hanssens
authors.affiliation: Theoretische Chemie, Institut für Chemie, Universität Potsdam , Karl-Liebknecht-Strasse 24-25, 14476 Potsdam-Golm, Germany.
authors.forename: Manuel
authors.initials: M
authors.lastname: Utecht
authors.affiliation: Department of Chemistry & IRIS Adlershof, Humboldt-Universität zu Berlin , Brook-Taylor-Strasse 2, 12489 Berlin, Germany.
authors.forename: Dragos
authors.initials: D
authors.lastname: Mutruc
authors.affiliation: Theoretische Chemie, Institut für Chemie, Universität Potsdam , Karl-Liebknecht-Strasse 24-25, 14476 Potsdam-Golm, Germany.
authors.forename: Evgenii
authors.identifier: 0000-0002-1732-1826
authors.initials: E
authors.lastname: Titov
authors.affiliation: Department of Chemistry & IRIS Adlershof, Humboldt-Universität zu Berlin , Brook-Taylor-Strasse 2, 12489 Berlin, Germany.
authors.forename: Jutta
authors.initials: J
authors.lastname: Schwarz
authors.affiliation: Department of Chemistry & IRIS Adlershof, Humboldt-Universität zu Berlin , Brook-Taylor-Strasse 2, 12489 Berlin, Germany.
authors.forename: Lutz
authors.initials: L
authors.lastname: Grubert
authors.affiliation: Department of Chemistry & IRIS Adlershof, Humboldt-Universität zu Berlin , Brook-Taylor-Strasse 2, 12489 Berlin, Germany.
authors.forename: David
authors.initials: D
authors.lastname: Bléger
authors.affiliation: Theoretische Chemie, Institut für Chemie, Universität Potsdam , Karl-Liebknecht-Strasse 24-25, 14476 Potsdam-Golm, Germany.
authors.forename: Peter
authors.initials: P
authors.lastname: Saalfrank
authors.affiliation: Department of Chemistry & IRIS Adlershof, Humboldt-Universität zu Berlin , Brook-Taylor-Strasse 2, 12489 Berlin, Germany.
authors.forename: Stefan
authors.identifier: 0000-0002-6124-0222
authors.initials: S
authors.lastname: Hecht