Synthesis of the anti and syn isomers of thieno[ff′]bis[1]benzothiophene.: Comparison of the optical and electrochemical properties of the anti and syn isomers

We report isomer-pure synthesis of thieno[2,3-f:5,4-f']bis-[1]benzothiophene and thieno[3,2-f.4,5-f ']bis [1]benzothiophene, the anti and syn isomers of a pentacyclic compound consisting of alternating thiophene and benzene rings. The optical and electrochemical properties of both are reported. In the anti isomer, the ribbonlike embedding of three thiophene units leads to a near-planar molecule with favorable pi-pi stacking behavior in the solid state as shown by X-ray crystal structure analysis.