Synthesis and doping of a multifunctional tetrathiafulvalene-substituted poly (isocyanide)

The poly(isocyanide) skeleton is shown to be a good support for assemblies of molecular units which permit p-type charge transport. A poly(isocyanide) containing tetrathiafulvalene (TTF) moieties in the side chains has been synthesized and characterized in its neutral state and has been oxidized to generate mixed valence states which display charge mobility in solution. UV-vis-NIR, EPR, and Raman spectroscopies were used to study the electronic properties of the polymer in its doped states, which were generated chemically with different oxidants. A broad charge-transfer band at 2100 nm characteristic of mixed valence agglomerations of neutral and cation radical TTFs was shown at lower doping levels, while evidence of aggregates between radical cation and the dicationic form of the heterocyclic system were seen at higher degrees of oxidation. The neutral macromolecule, the first mixed valence state, and the cation radical system can be reversibly interconverted by alternate oxidation with Fe(ClO4)(3) and subsequent reduction with triethylamine, and therefore the material can be considered as a candidate for electrochromic switches. EPR measurements reveal magnetic interactions between cation radical TTF moieties as well as indication of charge delocalization over the macromolecule. Bearing in mind the steric impediment that the alkyl chains attached to the TTF unit provide, we conclude that the results suggest that the motion of the charges in the first mixed valence state is intramacromolecular: this hypothesis implies that there are interactions of the TTF residues in the side chains of the polymer which lead to a stack of the pi-functional units, confirming the affirmation that this polymer skeleton is appropriate for appending electron-conducting stacks of pi-functional units.