Investigating pH Effects on the Photoswitching of Furanyl-Indolinium Heteroarylstilbenes
Abstract
Cationic heteroarylstilbenes, such as the furanyl-indolinium chromophore, represent a class of watersoluble, visible-light-responsive photoswitches. However, their photochemical behaviour under physiologically relevant pH conditions remains insufficiently understood. In this study, four derivatives were synthesized and systematically investigated, with particular emphasis on their photoswitching properties at three pH values using phosphate-buffered media. The visible-light-induced E/Z photoisomerization kinetics were analysed by UV/Vis spectroscopy, while the structures of the resulting isomers were confirmed by NMR spectroscopy. A key result is the pronounced pH dependence of the thermal Z→E back-isomerization in phosphate buffer, whereas the photoinduced E→Z switching is only weakly affected. The apparent thermal recovery is superimposed by a competing dark-decay process, which was quantified independently to separate concurrent degradation from the actual thermal back-isomerization kinetics. The derivatives differ in their chemical stability. The methyl-substituted derivative is comparatively robust, whereas the nitro-substituted derivative shows pronounced degradation. These results show that water solubility alone does not guarantee robust photoswitching under biologically relevant conditions and that both pH-dependent switching kinetics and chemical stability must be considered in the design of cationic heteroarylstilbene photoswitches.
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BibTeX
@misc{seemann2026investigating,
title = {{Investigating pH Effects on the Photoswitching of Furanyl-Indolinium Heteroarylstilbenes}},
author = {M. Seemann and J. N. Riese and R. Geitner and A. G. Groß and Alexander Gross},
howpublished = {ChemRxiv},
year = {2026},
month = sep,
doi = {10.26434/chemrxiv.15009146/v1},
url = {https://chemrxiv.org/doi/full/10.26434/chemrxiv.15009146/v1},
note = {CC BY},
}
RIS
TY - UNPB
TI - Investigating pH Effects on the Photoswitching of Furanyl-Indolinium Heteroarylstilbenes
AU - M. Seemann
AU - J. N. Riese
AU - R. Geitner
AU - A. G. Groß
AU - Alexander Gross
PY - 2026
DA - 2026/09/21
PB - ChemRxiv
DO - 10.26434/chemrxiv.15009146/v1
UR - https://chemrxiv.org/doi/full/10.26434/chemrxiv.15009146/v1
AB - Cationic heteroarylstilbenes, such as the furanyl-indolinium chromophore, represent a class of watersoluble, visible-light-responsive photoswitches. However, their photochemical behaviour under physiologically relevant pH conditions remains insufficiently understood. In this study, four derivatives were synthesized and systematically investigated, with particular emphasis on their photoswitching properties at three pH values using phosphate-buffered media. The visible-light-induced E/Z photoisomerization kinetics were analysed by UV/Vis spectroscopy, while the structures of the resulting isomers were confirmed by NMR spectroscopy. A key result is the pronounced pH dependence of the thermal Z→E back-isomerization in phosphate buffer, whereas the photoinduced E→Z switching is only weakly affected. The apparent thermal recovery is superimposed by a competing dark-decay process, which was quantified independently to separate concurrent degradation from the actual thermal back-isomerization kinetics. The derivatives differ in their chemical stability. The methyl-substituted derivative is comparatively robust, whereas the nitro-substituted derivative shows pronounced degradation. These results show that water solubility alone does not guarantee robust photoswitching under biologically relevant conditions and that both pH-dependent switching kinetics and chemical stability must be considered in the design of cationic heteroarylstilbene photoswitches.
ER -