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Published on: September 10, 2013
Controlling the conformational changes in donor-acceptor [4]-dendralenes through intramolecular charge-transfer
Alexander L Kanibolotsky1, John C Forgie, Greg J McEntee
1WestCHEM, Department of Pure and Applied Chemistry, University of Strathclyde, Glasgow G1 1XL, UK.
Chemistry (Weinheim an Der Bergstrasse, Germany)
|September 18, 2009
Summary
Two novel [4]-dendralene compounds with tunable donor-acceptor units were synthesized. Light and heat reversibly control their structural transformations, enabling potential applications in responsive materials.
Area of Science:
- Organic Chemistry
- Materials Science
- Photochemistry
Background:
- Donor-acceptor molecules are crucial for optoelectronic applications.
- Controlling molecular conformation is key to tuning material properties.
- Thiophene-based systems offer versatile electronic characteristics.
Purpose of the Study:
- To synthesize novel [4]-dendralene compounds with thiophene-(p-nitrophenyl) donor-acceptor units.
- To investigate the light- and heat-induced conformational transformations between two distinct states (a and b conformers).
- To explore the potential of these dendralenes in responsive materials and polymer applications.
Main Methods:
- Synthesis of [4]-dendralene compounds 13 and 15.
- Structural characterization using single-crystal X-ray diffraction and 1H NMR spectroscopy.
- Monitoring conformational changes via absorption spectroscopy and Density Functional Theory (DFT) calculations (B3LYP/6-31G*).
- Electrochemical polymerization and spectroelectrochemical studies of the EDOT derivative (15).
Main Results:
- Two [4]-dendralene compounds with tunable thiophene-(p-nitrophenyl) donor-acceptor units were successfully synthesized.
- Dendralenes exist in two conformers (a and b) interconverting via light-induced isomerization, with ambient light driving the a to b conversion.
- First-order kinetics observed for the a-->b transformation with rate constants k=0.0027 s⁻¹ (13) and k=0.00022 s⁻¹ (15).
- DFT calculations support a photoinduced intramolecular charge transfer (ICT) mechanism for the a-->b conversion.
- The EDOT derivative (15) can be polymerized electrochemically, and the a conformer can be trapped in the solid state.
Conclusions:
- The synthesized [4]-dendralenes exhibit reversible light- and heat-controlled conformational changes.
- Photoinduced intramolecular charge transfer is the primary mechanism driving the observed isomerization.
- These compounds demonstrate potential for developing light-responsive materials and solid-state applications via polymerization.
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