Synthesis and characterization of benzo[1,2-b:4,3-b’]dithiophene-based organosilicon compounds

Silicon-containing polymers, having a regular alternating arrangement of silanylenes and π-electron systems in a polymer backbone, are of great interest as photoresists, semiconducting materials, and precursors of silicon carbide (1). On the other hand, much attention has been paid to thiophene-based heteroaromatic compounds due to their important photoelectric properties, and their use as charge transport materials in broad range of applications including OFETs, OLEDs and Solar Cells (2). Thiophene units bridged by silylene σ-linkages, including both small molecules and polymers, have been therefore studied extensively, because of their stability, in many optoelectronic applications (3). In this context only simple thiophene rings have been studied, hence living plenty of space for further structural engineering including the use of polyconjugated thiophene-based systems. For several years our group has been working on synthesis and functionalization of benzo[1,2-b:4,3-b’]dithiophene (BDT, Figure 1) derivatives (4,5), which are an interesting class of π-conjugated systems in functional organic materials (6), and are key intermediates for the synthesis of inherently chiral thiahelicenes (7). In this communication we will report our new field of investigation where we have focused on the development of π-conjugated BDT units bridged by silylene σ-linkages of general formula 1, as key intermediate to prepare active molecular or polymeric photoelectronic systems. We will discuss the synthesis of structures 1 along with the study of the optical, chemical and electrochemical properties.