Core structure dependence of cycloreversion dynamics in diarylethene analogs
Chana R Honick1, Garvin M Peters1, Jamie D Young1
1Department of Chemistry, Johns Hopkins University, 3400 N. Charles St., Baltimore, MD 21218, USA. artbragg@jhu.edu.
Physical Chemistry Chemical Physics : PCCP
|January 24, 2020
Summary
Structural rigidity in molecular photoswitches significantly impacts their excited-state dynamics. Rigid core photoswitches exhibit faster cycloreversion than flexible perfluorocyclopentene ones, influencing reaction pathways.
Area of Science:
- Photochemistry
- Molecular Switches
- Organic Chemistry
Background:
- Diarylperfluorocyclopentenes are molecular photoswitches known for reversible photocyclization.
- Cycloreversion efficiency is limited by excited-state deactivation, influenced by pendant aryl groups.
- The impact of core bridge structure on excited-state dynamics remains underexplored.
Purpose of the Study:
- To investigate how core bridge structural motifs affect the excited-state dynamics of molecular photoswitches.
- To compare the photophysical behaviors of perfluorocyclopentene and diarylethene derivatives with varied bridge groups.
- To elucidate the relationship between structural rigidity and cycloreversion quantum yields.
Main Methods:
- Synthesis and characterization of diarylperfluorocyclopentene and diarylethene photoswitches with different core bridge groups.
- Photophysical studies including transient absorption spectroscopy to determine excited-state lifetimes.
- Analysis of temperature-dependent cycloreversion quantum yields and excited-state lifetimes.
Main Results:
- Flexible perfluorocyclopentene cores exhibit 3-4x slower cycloreversion than rigid diarylethene cores (e.g., thieno[3,4-b]thiophene).
- Increased structural rigidity of the core leads to faster rates of both nonreactive internal conversion and reactive cycloreversion.
- Comparable cycloreversion quantum yields were observed despite differences in excited-state lifetimes.
Conclusions:
- Structural rigidity of the core bridge is a critical factor in controlling excited-state dynamics of molecular photoswitches.
- Rigid cores result in shallower excited-state potential energy surfaces, facilitating faster deactivation pathways.
- Understanding these dynamics is key to designing efficient molecular photoswitches for various applications.
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