TY  - JOUR
A1  - Knie, Christopher
A1  - Utecht, Manuel Martin
A1  - Zhao, Fangli
A1  - Kulla, Hannes
A1  - Kovalenko, Sergey
A1  - Brouwer, Albert M.
A1  - Saalfrank, Peter
A1  - Hecht, Stefan
A1  - Bleger, David
T1  - ortho-Fluoroazobenzenes: visible light switches with very long-lived Z isomers
JF  - Chemistry - a European journal
N2  - Improving the photochemical properties of molecular photoswitches is crucial for the development of light-responsive systems in materials and life sciences. ortho-Fluoroazobenzenes are a new class of rationally designed photochromic azo compounds with optimized properties, such as the ability to isomerize with visible light only, high photoconversions, and unprecedented robust bistable character. Introducing sigma-electron-withdrawing F atoms ortho to the N=N unit leads to both an effective separation of the n -> pi* bands of the E and Z isomers, thus offering the possibility of using these two transitions for selectively inducing E/Z iso-merizations, and greatly enhanced thermal stability of the Z isomers. Additional para-electron-withdrawing groups (EWGs) work in concert with ortho-F atoms, giving rise to enhanced separation of the n -> pi* transitions. A comprehensive study of the effect of substitution on the key photochemical properties of ortho-fluoroazobenzenes is reported herein. In particular, the position, number, and nature of the EWGs have been varied, and the visible light photoconversions, quantum yields of isomerization, and thermal stabilities have been measured and rationalized by DFT calculations.
KW  - azobenzenes
KW  - photochromism
KW  - photoswitches
KW  - substituent effects
KW  - visible light
Y1  - 2014
U6  - https://doi.org/10.1002/chem.201404649
SN  - 0947-6539
SN  - 1521-3765
VL  - 20
IS  - 50
SP  - 16492
EP  - 16501
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Titov, Evgenii
A1  - Sharma, Anjali
A1  - Lomadze, Nino
A1  - Saalfrank, Peter
A1  - Santer, Svetlana
A1  - Bekir, Marek
T1  - Photoisomerization of an azobenzene-containing surfactant within a micelle
JF  - ChemPhotoChem
N2  - Photosensitive azobenzene-containing surfactants have attracted great attention in past years because they offer a means to control soft-matter transformations with light. At concentrations higher than the critical micelle concentration (CMC), the surfactant molecules aggregate and form micelles, which leads to a slowdown of the photoinduced trans -> cis azobenzene isomerization. Here, we combine nonadiabatic dynamics simulations for the surfactant molecules embedded in the micelles with absorption spectroscopy measurements of micellar solutions to uncover the reasons responsible for the reaction slowdown. Our simulations reveal a decrease of isomerization quantum yields for molecules inside the micelles. We also observe a reduction of extinction coefficients upon micellization. These findings explain the deceleration of the trans -> cis switching in micelles of the azobenzene-containing surfactants.
KW  - azobenzene
KW  - micelles
KW  - photoswitches
KW  - rate constants
KW  - surfactants
KW  - surface hopping
Y1  - 2021
U6  - https://doi.org/10.1002/cptc.202100103
SN  - 2367-0932
VL  - 5
IS  - 10
SP  - 926
EP  - 932
PB  - Wiley-VCH
CY  - Weinheim
ER  -