Electrochemical, spectroelectrochemical, and comparative studies of novel organic conjugated monomers and polymers featuring the redox-active unit tetrathianaphthalene

A series of monomers has been synthesized and characterized on the basis of the incorporation of tetrathianaphthalene (1) and its saturated (2) and open cyclic (3) forms as fused side groups onto polythiophene chains. The X-ray crystal structures of compounds 1 and 2 are reported. Tetrathianaphthalene (TTN) is an isomer of tetrathiafulvalene (TTF); however, monomer and polymer versions of 1 do not show any similarity to TTF in cyclic voltammetry (CV) or spectroelectrochemical measurements. CV experiments have shown that 1 and 3 are easier to oxidize than 2, whereas 1 also has an additional reduction peak, giving it a smaller HOMO−LUMO gap than the other two monomers. All three polymers of 1−3 have nearly the same oxidation and reduction potentials as well as band gaps; small variations can be attributed to the differences in the side groups. Spectroelectrochemical measurements revealed that the polymers showed electrochromic behavior; switching times and colorimetry measurements are reported. From this data, all three polymers have a color change of red to yellow with poly(3) having the best color contrast and percentage change in absorbance from various switching times