(Oligo)aromatic species with one or two conjugated Si[double bond, length as m-dash]Si bonds: near-IR emission of anthracenyl-bridged tetrasiladiene

A series of aryl disilenes Tip Si[double bond, length as m-dash]Si(Tip)Ar (2a-c) and para-arylene bridged tetrasiladienes, Tip Si[double bond, length as m-dash]Si(Tip)-LU-Si(Tip)[double bond, length as m-dash]SiTip (3a-d) are synthesized by the transfer of the Tip Si[double bond, length as m-dash]SiTip unit to aryl halides and dihalides by nucleophilic disilenides Tip Si[double bond, length as m-dash]SiTipLi (Tip = 2,4,6-iPr C H , Ar = aryl substituent, LU = para-arylene linking unit). The scope of the nucleophilic Si[double bond, length as m-dash]Si transfer reaction is demonstrated to also include substrates of considerable steric bulk such as mesityl or duryl halides Ar-X (Ar = Mes = 2,4,6-Me C H ; Ar = Dur = 2,3,5,6-Me C H, X = Br or I). Bridged tetrasiladienes Tip Si[double bond, length as m-dash]Si(Tip)-LU-Si(Tip)[double bond, length as m-dash]SiTip with more extended linking units surprisingly exhibit fluorescence at room temperature, albeit weak. DFT calculations suggest that partial charge transfer character of the excited state is a possible explanation.