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Indirect Red and Near-Infrared Z-to-E Photoisomerization of ortho-Functionalized Azobenzenes via Triplet Energy Transfer

submitted on 01.03.2021, 09:25 and posted on 02.03.2021, 12:48 by Jussi Isokuortti, Kim Kuntze, Matti Virkki, Zafar Ahmed, Elina Vuorimaa-Laukkanen, Mikhail A. Filatov, Andrey Turshatov, Timo Laaksonen, Arri Priimägi, Nikita A. Durandin
Designing azobenzene photoswitches capable of selective and efficient photoisomerization by long wavelength excitation is a long-standing challenge. Indirect excitation can expand the properties of the photoswitching system beyond the intrinsic limits of azobenzenes. Herein, a rapid Z-to-E isomerization of two ortho-functionalized azobenzenes with near-unity photoconversion was facilitated via triplet energy transfer upon red and near-infrared (up to 770 nm) excitation of porphyrin photosensitizers in catalytic micromolar concentrations. Our results indicate that the whole process of triplet-sensitized isomerization is strongly entropy-driven. This ensures efficient Z-to-E photoswitching even when the azobenzene triplet energy is considerably higher (>200 meV) than for the sensitizer, which is the key for the expansion of excitation wavelengths into the near-infrared spectral range.


Academy of Finland (Grant No. 316893)

ERC Starting Grant Project PHOTOTUNE, Decision number 679646


Email Address of Submitting Author


Tampere University



ORCID For Submitting Author


Declaration of Conflict of Interest

No conflict of interet to declare.

Version Notes

This version is a pre-print.