Double-pillaring strategy for silacyclophanes: Synthesis and structures of disilanyl double-pillared bisanthracenes

A new series of silacyclophanes with two disilanyl pillars has been synthesized using a straightforward method. A silylation reaction of 1,8-dilithioanthracenes allowed the connection of two anthracene rings with two Si-Si bonds to afford disilanyl double-pillared bisanthracenes ( ^SiDPBAs). The major product had an anti geometry of the anthracene rings, and a unique steplike structure favorable for σ-π conjugations was revealed by X-ray crystallographic analysis. Upon introducing a substituent at the 10-position of anthracene, we obtained a U-shaped isomer with syn geometry that yielded an excimer upon excitation and can decompose without steric protection. Easy access to silacyclophanes: A new series of silacyclophanes, disilanyl double-pillared bisanthracenes (^SiDPBAs), was synthesized using a one-pot operation from 1,8-diiodoanthracenes. The major product with anti geometry bears a steplike structure favorable for σ-π conjugation, and the minor product with syn geometry bears a U-shaped structure favorable for excimer formation.