SYNTHESIS AND CHARACTERISTIC PROPERTIES OF POLY(NAPHTHO[2,3-C]THIOPHENE) AS A SERIES OF FUSED-RING CONDUCTING POLYMERS ANALOGOUS TO POLY(ISOTHIANAPHTHENE)

Naphtho[2,3-c]thiophene was easily obtained as a yellow solid containing 1,3-dihydronaphtho[2,3-c]thiophene as a by-product through dehydration of 1,3-dihydronaphtho[2,3-c]thiophene 2-oxide by refluxing with neutral alumina in deoxygenated methylene chloride solution. Naphtho[2,3-c]thiophene was electrochemically polymerized by a well-known technique to form a thin film of poly(naphtho[2,3-c]thiophene) (PNT) which showed barely perceptible color changes associated with the electrochemical doping at a redox potential of ≈0.69 V versus Ag/AgCl. An opto-electrochemical study revealed that the band gap (Eg) of PNT was 1.5 eV, whereas it had been previously expected from theoretical calculations to be nearly zero eV. © 1990.