ELECTROCHEMICAL PROPERTIES AND ELECTRONIC-STRUCTURES OF CONJUGATED POLYQUINOLINES AND POLYANTHRAZOLINES

The effects of molecular structure on the electronic structure and red ox properties of a series of 22 systematically designed conjugated pol yquinolines and polyanthrazolines are explored by cyclic voltammetry a nd spectroelectrochemistry on thin films. The measured electrochemical bandgap of the series of conjugated polymers was in the range 2.0-3.1 eV and found to be in good agreement with the optical bandgap. The ox idation and reduction potentials, ionization potential, and electron a ffinity of the series of polymers were correlated with their main stru ctural features. All the polyquinolines and polyanthrazolines had reve rsible reduction with formal potentials of -1.57 to -2.08 V (versus SC E) which make them excellent n-type semiconducting polymers. Polymers containing anthrazoline units have a higher electron affinity by 0.3-0 .4 eV than those containing bis(quinoline) units. On the other hand, t hiophene-linked polymers have a lower ionization potential by 0.45-0.5 eV than those with phenylene linkages. Thus, thiophene-linked polyant hrazolines combine both low ionization potentials (similar to 4.8-4.9 eV) and high electron affinities (similar to 2.9 eV) and as a result c an be p-type and n-type doped to conducting polymers with relatively m ore stability in air. Spectroelectrochemistry of the thiophene-linked polymers revealed features characteristic of polarons and bipolarons o r radical ion dimers. The results suggest that the series of polyquino lines and polyanthrazolines are promising electronic and optoelectroni c materials.