NEW PROCESSABLE LOW-BAND-GAP, CONJUGATED POLYHETEROCYCLES

Poly(2,3-dihexylthieno[3,4-b]pyrazine) (2b) has been prepared by ferri c chloride polymerization of 2,3-dihexylthieno[3,4-b]pyrazine (4) and studied. It is a dark blue-black soluble material which becomes light yellow in tie doped stale as either a solution or film. DoPed films ca n be cast directly from solution. The band-pp, obtained from the absor ption edge, is ca. 0.86-1.02 eV as the film and 1.14 eV as a CHCl3 sol ution. This value of about 0.95 +/- 0.1 eV is lower than that of poly( isothianaphthene) and poly(5-decylisothianaphthene), which we report h ere. It is consistent with theoretical predictions and is one of the l owest band-gaps reported to date. When doped with nitrosonium tetraflu oroborate the films show conductivities of up to 3.6 x 10(-2) S cm-1. Poly(5-decylisothianaphdiene) {(1b; poly(5-decylbenzo[c]thiophene)) ha s been prepared by FeCl3 oxidation of 5-decyl-1,3-dihyhrobenzo[c]thiop hene (6). It is a soluble dark blue-black material which forms a light yellow transparent solution when doped.