Preparation, structure, and properties of tris(trimethylsilyl)silyl-substituted anthracenes:: Realization of ideal conformation for σ-π conjugation involving eclipse of Si-Si σ-bond with p-orbital of aromatic ring

Synthesis and X-ray diffraction analysis of 9- and 9,10-tris(trimethylsilyl)silyl (TTMSS)-substituted anthracenes were carried out to disclose that one of the Si-Si a-bonds in the TTMSS-substituted anthracenes were perpendicular to the aromatic rings. The introduction of the TTMSS groups induced red shift of UV absorption and fluorescence emission maxima as compared with the parent and 9-pentamethyldisilanylated anthracenes. Theoretical calculation suggests LUMO levels of the TTMS S -substituted anthracenes are lowered by sigma*-pi* orbital interaction.