Tuning the photochemical isomerization in azobenzene analogues containing phenol groups and heterocyclic rings
Abstract
A C T Azobenzenes and their heterocyclic analogues, such as azopyrazoles and azoisoxazoles, are versatile photoswitches with applications in responsive materials. Fully exploiting these systems requires a comprehensive understanding on how structural modifications and environmental factors control their isomerization kinetics and the stability of the Z (cis) isomers. In this work, we synthesized and systematically investigated the photochromic properties of a series of azobenzene and azoheteroarene derivatives. We combined experimental and theoretical methods to correlate molecular structure with photoswitching behavior. The photoinduced dynamics were studied using steady-state UV-vis and ultrafast time-resolved pump-probe spectroscopy, while the underlying molecular mechanisms were investigated using density functional theory (DFT). We show that structural modifications, including phenol groups, secondary amines, alkoxy chains, and ortho-methyl substituents, strongly affect ground-state thermal relaxation. By comparing the photoswitching behavior in toluene (non-polar solvent) and methanol (polar protic solvent), we show that the thermal half-lives of the Z isomers can be tuned over six orders of magnitude, from hundreds of milliseconds to several days. For derivatives bearing phenol or secondary amine groups, protic environments strongly accelerate relaxation. Quantum chemical calculations support these observations and show that solvent-assisted proton transfer opens an energetically favorable, lowbarrier zwitterionic pathway with a single nitrogen-nitrogen bond that allows free rotation. These results provide guidelines for designing molecular switches with tailored properties.
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BibTeX
@article{rossi2026tuning,
title = {{Tuning the photochemical isomerization in azobenzene analogues containing phenol groups and heterocyclic rings}},
author = {Ruggero Rossi and Dominika Jaďuďová and Sandra Doria and Alessandro Iagatti and Camilla Parmeggiani and Diederik S Wiersma and Wybren Jan Buma and Tim Prins and Michiel Hilbers and Adele Laurent and Miroslav Medved and Daniele Martella and Mariangela Di Donato},
journal = {Journal of Photochemistry and Photobiology A: Chemistry},
year = {2026},
month = nov,
doi = {10.1016/j.jphotochem.2026.117770},
url = {https://nantes-universite.hal.science/hal-05849466v1},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Tuning the photochemical isomerization in azobenzene analogues containing phenol groups and heterocyclic rings
AU - Ruggero Rossi
AU - Dominika Jaďuďová
AU - Sandra Doria
AU - Alessandro Iagatti
AU - Camilla Parmeggiani
AU - Diederik S Wiersma
AU - Wybren Jan Buma
AU - Tim Prins
AU - Michiel Hilbers
AU - Adele Laurent
AU - Miroslav Medved
AU - Daniele Martella
AU - Mariangela Di Donato
PY - 2026
DA - 2026/11/03
JO - Journal of Photochemistry and Photobiology A: Chemistry
DO - 10.1016/j.jphotochem.2026.117770
UR - https://nantes-universite.hal.science/hal-05849466v1
AB - A C T Azobenzenes and their heterocyclic analogues, such as azopyrazoles and azoisoxazoles, are versatile photoswitches with applications in responsive materials. Fully exploiting these systems requires a comprehensive understanding on how structural modifications and environmental factors control their isomerization kinetics and the stability of the Z (cis) isomers. In this work, we synthesized and systematically investigated the photochromic properties of a series of azobenzene and azoheteroarene derivatives. We combined experimental and theoretical methods to correlate molecular structure with photoswitching behavior. The photoinduced dynamics were studied using steady-state UV-vis and ultrafast time-resolved pump-probe spectroscopy, while the underlying molecular mechanisms were investigated using density functional theory (DFT). We show that structural modifications, including phenol groups, secondary amines, alkoxy chains, and ortho-methyl substituents, strongly affect ground-state thermal relaxation. By comparing the photoswitching behavior in toluene (non-polar solvent) and methanol (polar protic solvent), we show that the thermal half-lives of the Z isomers can be tuned over six orders of magnitude, from hundreds of milliseconds to several days. For derivatives bearing phenol or secondary amine groups, protic environments strongly accelerate relaxation. Quantum chemical calculations support these observations and show that solvent-assisted proton transfer opens an energetically favorable, lowbarrier zwitterionic pathway with a single nitrogen-nitrogen bond that allows free rotation. These results provide guidelines for designing molecular switches with tailored properties.
SN - 1010-6030
ER -