σ–σ * conjugation Across Si─O─Si Bonds

Front Cover : Polysiloxanes and silsesquioxanes are well‐known, traditional insulating materials typically transparent or opaque white. In article 2500081, Richard M. Laine and co‐workers describe the first examples of colored polysiloxane co‐polymers that demonstrate conjugation via a very unexpected mechanism. Thus, Me 2 VinylSi─O─SiMe 2 Vinyl when copolymerized with aromatic and hetero‐aromatic (Br─Ar─Br) co‐monomers exhibit conjugation via Si─O─Si bonds contrary to the wide‐spread under‐standing that such linkages must be insulating. Conjugation is evidenced by changes in absorption and emission spectra that depend on the degree of polymerization. Longer chains give smaller band gaps evidenced by shifts in emission from blue to red. In contrast, the photophysics of model compounds is mundane.