C–N cross coupling approach synthesis and electronic properties of donor–acceptor oligomer

C–N cross coupling approach synthesis of donor–acceptor oligomer containing 9,9-dioctyl-N2,N7-diaryl-9H-fluorene-2,7-diamine and 5-octyl-1,3-di(thiophen-2-yl)-4H-thieno[3,4-c]pyrrole-4,6(5H)-dione has been reported. The electronic properties of the synthesized oligomers were studied by UV-visible spectroscopy, fluorescence spectroscopy, cyclic voltammetry and computational analysis. The oligomers absorb the visible light at around 508–520 nm, both in solution as well as in solid state. We observed dual emission band centred at around 595 nm (LE emission) and 650 nm (CT emission) with a long tail in near-infrared (NIR) spectral region when the oligomers were excited at around 510 nm. Large Stokes shifts (∼130 nm) led to deep red emission which was likely due to the interaction of donor–acceptor units of the oligomer backbone. Overall, the experimental and theoretical results of these oligomers indicate that they can be used as a promising materials for organic electronics.