Novel substituted tetrathia[7]helicenes by direct functionalization of the helical system or photocyclization of substituted 1,2-(bis-benzodithienyl)ethenes

In this work we report the synthesis of several new tetrathia[7]helicenes ([7]THs) functionalized with different electron-donor (ED) and electron-acceptor (EA) substituents in the positions 2,13 (the α positions of terminal thiophene rings) and/or 7,8 (on the central arene ring of the helical system). Some substituents were chosen on the basis of theoretical calculations performed on [7]THs to predict the best groups for applications in optoelectronics; some others were conceived to endow helicenes with appropriate groups in view of their insertion into polymeric structures.