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Excited-state intramolecular proton-transfer reaction demonstrating anti-Kasha behavior
Huan-Wei Tseng1, Jiun-Yi Shen1, Ting-Yi Kuo1
1Department of Chemistry , National Taiwan University , Taipei , 10617 Taiwan , Republic of China . Email: chop@ntu.edu.tw ;
Chemical Science
|June 14, 2018
Summary
Two new 3-hydroxychromone derivatives show unique photophysical properties. Their excited-state intramolecular proton transfer (ESIPT) reaction efficiency increases significantly in low-polarity solvents when excited to higher energy levels.
Area of Science:
- Photochemistry
- Organic Chemistry
- Spectroscopy
Background:
- The excited-state intramolecular proton transfer (ESIPT) is a crucial photophysical process.
- Kasha's rule generally dictates emission from the lowest excited state.
- Understanding deviations from Kasha's rule is important for photophysical studies.
Purpose of the Study:
- To investigate the photophysical properties of novel 3-hydroxychromone derivatives.
- To explore the influence of excitation energy and solvent polarity on the ESIPT reaction.
- To analyze conditions leading to anti-Kasha emission and deviations from Kasha's rule.
Main Methods:
- Synthesis of two new 3-hydroxychromone derivatives.
- Steady-state and time-resolved emission spectroscopy.
- Analysis of excitation and emission spectra.
- Kinetic analysis of excited-state dynamics.
Main Results:
- The designed 3-hydroxychromone derivatives exhibit ESIPT.
- ESIPT efficiency is significantly enhanced upon excitation to higher excited states (Sn, n > 1) in low-polarity solvents.
- Conditions for observing this anti-Kasha phenomenon differ from those for standard anti-Kasha emission.
Conclusions:
- Novel 3-hydroxychromone derivatives display unusual photophysical behavior.
- High-energy excitation in low-polarity solvents can enhance ESIPT efficiency, challenging Kasha's rule.
- The study provides insights into the nuanced conditions governing excited-state proton transfer reactions.
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