Regio- and stereo-selective [4+4] photodimerization of angular-shaped dialkyltetracenedithiophene

Angular-shaped dialkyltetracenedithiophenes (aTDTs) undergo [4+4] photodimerization in solution to form a butterfly-shaped skeleton. This reaction proceeds in a regio- and stereo-selective manner, forming only a single planosymmetric syn-[2,2]-daTDT out of six possible products. The photocycloaddition of aTDTs can take place topochemically in the thin-film state while maintaining regio- and stereo-selectivity. Stronger aliphatic dispersion forces and π-π interactions play important roles in forming the eclipsed dimeric complex that leads to the syn-[2,2]-daTDT isomer.