Organometallic synthesis of n-type π-conjugated polymers with dopant cation trapping sites and stability of n-doping state against air

Abstract

n-Type π-conjugated polymers comprising a 1,2,4-triazole ring substituted by a benzo-15-crown 5-ether (benzo15C5) subunit at the 4-position of the 1,2,4-triazole ring and n-type aromatic rings such as pyridine-2,5-diyl and 2,1,3-benzothiadiazole-4,7-diyl rings were synthesized by organometallic polycondensation. The UV-visible spectra of the polymers exhibited absorption maxima (λmax values) at a longer wavelength than that exhibited by 3,5-bis(2-bromopyridyl)-4-benzo15C5-1,2,4-triazole, revealing that their π-conjugation system was expanded along the polymer chain. The polymers with the benzo15C5 subunit underwent an electrochemical reduction (n-doping), and the corresponding oxidation (n-dedoping) occurred at an unusually high potential in an acetonitrile solution of NaClO4; the factor responsible for the unusually high oxidation potential was the stabilized n-doping state that was attributed to the inclusion of Na+ in the 15C5 ring. The polymers with the benzo15C5 subunit exhibited a considerably higher stability of the n-doping state in air than did those without this subunit. Copyright © 2012 Society of Chemical Industry