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Crown-annelated oligothiophenes as model compounds for molecular actuation
Bruno Jousselme1, Philippe Blanchard, Eric Levillain
1Groupe Systèmes Conjugués Linéaires, UMR CNRS 6501, Université d'Angers, 2 Boulevard Lavoisier, 49045 Angers, France.
Journal of the American Chemical Society
|January 30, 2003
Summary
Crown-annelated oligothiophenes were synthesized and complexed with metal cations. Cation binding induced conformational changes, altering electronic properties and redox potentials of the conjugated system.
Area of Science:
- Organic Chemistry
- Supramolecular Chemistry
- Materials Science
Background:
- Oligothiophenes are conjugated organic materials with potential applications in electronics.
- Macrocyclic structures can be designed to bind specific metal cations.
- Understanding cation-pi system interactions is crucial for designing functional materials.
Purpose of the Study:
- To synthesize novel crown-annelated quater- (4T) and sexithiophenes (6T) with oligooxyethylene chains.
- To investigate the cation-binding properties and their effect on the electronic structure of these macrocycles.
- To explore the interplay between electrostatic interactions and conformational changes upon cation complexation.
Main Methods:
- Synthesis of crown-annelated quater- and sexithiophenes.
- Cation-binding analysis using (1)H NMR and UV-vis spectroscopy.
- Theoretical calculations using density functional methods.
- Electrochemical characterization via cyclic voltammetry.
Main Results:
- Successful synthesis of 4T and 6T macrocycles with oligooxyethylene chains.
- Formation of 1:1 complexes with Ba(2+), Sr(2+), and Pb(2+) cations.
- Cation complexation induced a conformational transition in the pi-conjugated system.
- Theoretical predictions showed a narrowed highest occupied-lowest unoccupied molecular orbital gap and decreased redox potentials.
- Experimental results indicated shifts in redox potentials (E(0)(1) and E(0)(2)) dependent on cation binding constants and interactions.
Conclusions:
- Crown-annelated oligothiophenes effectively bind specific metal cations.
- Cation binding triggers significant conformational changes, impacting the electronic and redox properties of the conjugated system.
- The observed unusual redox potential shifts highlight the complex interplay between electrostatic forces and structural rearrangements in these supramolecular systems.
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