Indanedione-substituted poly(terthiophene)s: Processable conducting polymers with intramolecular charge transfer interactions

The electrochemical and chemical syntheses of poly(terthiophene)s bearing an indanedione pendant group and displaying intramolecular charge transfer interactions have been achieved. The nature of the charge transfer interaction is characterized through DFT calculations and experimental studies, including resonance Raman spectroscopy and absorption and emission data through a Lippert-Mataga analysis. It is found that the low-energy transition present in the indanedione-bearing monomer species has considerable charge transfer character with a dipole change of II D. Decomposition of the indanedione group occurred during hydrazine reduction after chemical polymerization. A soluble, low molecular weight indanedione-substituted polymer (weight average 4500 Da) was nonetheless obtained following the use of a milder reducing agent, triethanolamine. To the best of our knowledge, this is the first example of the use of triethanolamine for the reduction of an oxidized polythiophene, providing a milder and safer alternative to hydrazine. In an attempt to produce higher molecular weight processable polymers with intramolecular charge transfer interactions, a copolymer of the indanedione-substituted terthiophene and a dihexylterthiophene was synthesized. The electronic conjugation of the produced polymers was characterized by Raman frequency dispersion experiments and show dispersion rate parameters similar to those observed for other substituted polythiophenes.