Dibenzo[d,d′]benzo[2,1-b:3,4-b′]difurans with extended π-conjugated chains: synthetic approaches and properties

Abstract

Ru-catalysed cross-dimerisation of 3,8-di(hexyn-1-yl)dibenzo[d,d']benzo[2,1-b,3,4-b’]difuran [3,8-di(hexyn-1-yl)-DBBDF] with 2 equivalents of methyl (E)-penta-2,4-dienoate produces 3,8-bis[(1E,3E,5E)-2-butyl-6-methoxycarbonylhexa-1,3,5-trien-1-yl]-DBBDF (9a), and the total yield of 9a obtained from 2,3-difluoro-1,4-diiodobenzene is 50% using the six-step reaction. A series of 3,8-bis(hexatrienyl)-DBBDF compounds and unsymmetrical 8-decyl-3-hexatrienyl-DBBDF compounds were also prepared using the same method. These compounds were evaluated using ultraviolet-visible (UV-vis) spectroscopy and cyclic voltammetry (CV). Time-dependent density-functional theory (TD-DFT) calculations indicate that efficient π–π* excitations occur using the conjugated trienyl side chain groups.