Functional materials based on redox-active components
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Conducting polymers have been extensively investigated in a wide range of applications due to their ability to achieve near metallic conductivity while possessing the flexibility and processability of traditional polymers. However, interchain and solid-state effects have made direct investigation of the polymer systems difficult. A series of systematically varied model compounds have been designed to provide detailed information about through-chain charge transport in well-defined oligothiophenes. Our design incorporates two metal binding pockets at either end of an oligothiophene bridge to investigate the interaction of redox centers and charge transport properties between conducting polymers and bound transition metal centers. Synthesis, characterization, electrochemistry, and detailed EPR investigations of this new series of oligothiophene model compounds and the analogous mononuclear compounds will be discussed herein. Conjugated polymer matrices possess a large number of available oxidation states making them an attractive choice for use as redox-active ligands. This variety of oxidation states offers a means to easily tune the amount of electron density on a metal center and consequently affect the binding of an additional ligand. Our approach utilizes conducting metallopolymers with metal complexes synthetically incorporated directly into the conducting polymer backbone. The redox-dependent properties of this class of materials and their development as small molecule storage and delivery systems have been explored utilizing a variety of novel electropolymerizable transition metal complexes. The design, synthesis, characterization, and redox-affected properties of the monomers, corresponding conducting metallopolymers, and model complexes are discussed. The tub-shaped dibenzo[a,e]cyclooctatetraene molecule undergoes a large change in geometry upon reduction to form the planar aromatic species. Herein, we seek to prepare and investigate a supramolecular assembly utilizing this redox-active molecule. In contrast to electrochemically active frameworks where redox changes occur at the metal centers, incorporation of a functionalized dibenzo[a,e]cyclooctatetraene ligand into an assembly has the potential to result in a redox-active framework. Not only would the redox-activity occur at the organic bridge, but reduction of the system should result in a large geometry change.