Symmetrical fluorescent oligothiophene and benzene centered bispyrenoimidazole derivatives with double n-dodecyl chains showing high thermal stability

Abstract

A family of symmetrical oligothiophene (dithiophene, terthiophene, and quaterthiophene) or benzene centered bispyrenoimidazole derivatives, having the same coplanar pyrenoimidazole terminal groups at each side, has been synthesized via Radziszewski, N-alkylation, and the following Pd(PPh3)4 catalyzed Suzuki and Stille coupling reactions. Double n-dodecyl chains are introduced to the molecules at the same time in order to increase their solubility in organic solvents. UV–vis and fluorescence spectra as well as thermal properties have been studied. The results demonstrate that compound 4 with a benzene linker displays the strongest fluorescence intensity, and oligothiophene centered bispyrenoimidazole derivatives 5–7 show obvious bathochromic shifts compared with benzene centered compound 4. It is worth mentioning that this family of compounds exhibits excellent thermal stability with the decomposition temperature higher than 400°C even if the incorporation of double n-dodecyl chains. Furthermore, X-ray single-crystal structures of one representative compound 4·(CHCl3)2 and an intermediate 3 have been described.