Central Ring Puckering Enhances the Stokes Shift of Xanthene Dyes

0583934 - ÚOCHB 2025 RIV DE eng J - Journal Article
Dunlop, David - Horváth, P. - Klán, P. - Slanina, Tomáš - Šebej, P.
Central Ring Puckering Enhances the Stokes Shift of Xanthene Dyes.
Chemistry - A European Journal. Roč. 30, č. 19 (2024), č. článku e202400024. ISSN 0947-6539. E-ISSN 1521-3765
R&D Projects: GA MŠMT(CZ) LTC20076
Research Infrastructure: RECETOX RI II - 90269
Institutional support: RVO:61388963
Keywords : conformation * fluorescence * functional dyes * pyronin * quantum chemical calculations * stokes shift * xanthene
OECD category: Physical chemistry
Impact factor: 4.3, year: 2022
Method of publishing: Open access
https://doi.org/10.1002/chem.202400024

Small-molecule dyes are generally designed based on well-understood electronic effects. However, steric hindrance can promote excited-state geometric relaxation, increasing the difference between the positions of absorption and emission bands (the Stokes shift). Accordingly, we hypothesized that sterically induced central ring puckering in xanthene dyes could be used to systematically increase their Stokes shift. Through a combined experimental/quantum-chemical approach, we screened a group of (9-acylimino)-pyronin dyes with a perturbed central ring geometry. Our results showed that an atom with sp(3) hybridization in position 10 of (9-acylimino)-pyronins induces central ring puckering and facilitates excited-state geometric relaxation, thereby markedly enhancing their Stokes shifts (by up to similar to 2000 cm(-1)). Thus, we prepared fluorescent (9-acylimino)-pyronin pH sensors, which showed a Stokes shift disparity between acid and base forms of up to similar to 8700 cm(-1). Moreover, the concept of ring puckering-enhanced Stokes shift can be applied to a wide range of xanthene analogues found in the literature. Therefore, central ring puckering may be reliably used as a strategy for enhancing Stokes shifts in the rational design of dyes.
Permanent Link: https://hdl.handle.net/11104/0351920