Exploring the excited state mechanisms of a viscosity-sensitive zeromethine merocyanine dye emitter.
- 1Institut für Organische Chemie, Julius-Maximilians-Universität Würzburg Am Hubland 97074 Würzburg Germany [email protected].
- 2School of Chemistry, Indian Institute of Science Education and Research Thiruvananthapuram Vithura Thiruvananthapuram 695551 India [email protected].
- 3Center for Nanosystems Chemistry (CNC), Julius-Maximilians-Universität Würzburg Theodor-Boveri-Weg 97074 Würzburg Germany.
Abstract
Merocyanine (MC) dyes are among the most versatile and tunable chromophores owing to their structural flexibility. However, their excited state dynamics, which often lead to fluorescence quenching by ultrafast non-radiative decay pathways such as photoisomerization or relaxation through conical intersections, are poorly understood for most MCs. Herein, we elucidate the excited state mechanisms of a zeromethine MC dye (PyBA), which represents a special case of the donor-acceptor architecture featuring two directly connected heterocycles. The analysis was achieved by combining steady-state measurements under varying temperature, viscosity and polarity conditions, time-resolved ultrafast spectroscopy, and quantum-chemical calculations. Our studies show that PyBA upon photoexcitation develops a twisted intramolecular charge transfer (TICT) state in dynamic environments (e.g., CH₂Cl₂), whereas this process is restricted in rigid environments (PMMA matrix), leading to a significant luminescence turn-on with the quantum yield (Φ PL) increasing from 0.7% to 55%. Moreover, the measurements performed in the PMMA matrix reveal room temperature phosphorescence (RTP) even under ambient conditions, i.e. even without external stimuli, which becomes more intense at cryogenic temperatures under an argon atmosphere, reaching a phosphorescence lifetime of 705 ms. Furthermore, this work introduces a simple and time-efficient strategy for screening small-molecule fluorescence probes.
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BibTeX
@article{fichtner2026exploring,
title = {{Exploring the excited state mechanisms of a viscosity-sensitive zeromethine merocyanine dye emitter.}},
author = {Julian Fichtner and Preetika Verma and Menyhárt Sárosi and Matthias Stolte and Yapamanu Adithya Lakshmanna and Frank Würthner},
journal = {Chemical science},
year = {2026},
month = oct,
doi = {10.1039/d6sc05772a},
url = {https://europepmc.org/article/MED/42910032},
note = {CC BY},
}
RIS
TY - JOUR
TI - Exploring the excited state mechanisms of a viscosity-sensitive zeromethine merocyanine dye emitter.
AU - Julian Fichtner
AU - Preetika Verma
AU - Menyhárt Sárosi
AU - Matthias Stolte
AU - Yapamanu Adithya Lakshmanna
AU - Frank Würthner
PY - 2026
DA - 2026/10/12
JO - Chemical science
DO - 10.1039/d6sc05772a
UR - https://europepmc.org/article/MED/42910032
AB - Merocyanine (MC) dyes are among the most versatile and tunable chromophores owing to their structural flexibility. However, their excited state dynamics, which often lead to fluorescence quenching by ultrafast non-radiative decay pathways such as photoisomerization or relaxation through conical intersections, are poorly understood for most MCs. Herein, we elucidate the excited state mechanisms of a zeromethine MC dye (PyBA), which represents a special case of the donor-acceptor architecture featuring two directly connected heterocycles. The analysis was achieved by combining steady-state measurements under varying temperature, viscosity and polarity conditions, time-resolved ultrafast spectroscopy, and quantum-chemical calculations. Our studies show that PyBA upon photoexcitation develops a twisted intramolecular charge transfer (TICT) state in dynamic environments (e.g., CH₂Cl₂), whereas this process is restricted in rigid environments (PMMA matrix), leading to a significant luminescence turn-on with the quantum yield (Φ PL) increasing from 0.7% to 55%. Moreover, the measurements performed in the PMMA matrix reveal room temperature phosphorescence (RTP) even under ambient conditions, i.e. even without external stimuli, which becomes more intense at cryogenic temperatures under an argon atmosphere, reaching a phosphorescence lifetime of 705 ms. Furthermore, this work introduces a simple and time-efficient strategy for screening small-molecule fluorescence probes.
SN - 2041-6520
SN - 2041-6539
ER -