(Oligo)aromatic species with one or two conjugated SiSi bonds: near-IR emission of anthracenyl-bridged tetrasiladiene
A series of aryl disilenes Tip2SiSi(Tip)Ar (2a–c) and para-arylene bridged tetrasiladienes, Tip2SiSi(Tip)–LU–Si(Tip)SiTip2 (3a–d) are synthesized by the transfer of the Tip2SiSiTip unit to aryl halides and dihalides by nucleophilic disilenides Tip2SiSiTipLi (Tip = 2,4,6-iPr3C6H2, Ar = aryl substituent, LU = para-arylene linking unit). The scope of the nucleophilic SiSi 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-Me3C6H2; Ar = Dur = 2,3,5,6-Me4C6H, X = Br or I). Bridged tetrasiladienes Tip2SiSi(Tip)–LU–Si(Tip)SiTip2 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.