End-capped silole dendrimers on a carbosilane periphery: Potential electroluminescent materials

The divergent synthesis of end-capped silole dendrimers Gn-2 ⁿ⁺¹Silole (n = 1-4) using 2,4,6,8tetramethyl-2,4,6,8- tetravinylcyclotetrasiloxane [Me(CH₂=CH)SiO]₄ as a core molecule and allyl alcohol/ dichloromethylsilane as a building block is described in this paper. The reaction of the dichloride functionalities of the carbosiloxane dendrimers Gn-2ⁿ⁺²Cl (n = 1-4) with the 1,4-diphenylbutadiene1,4-dianions (1) provided an effective route for the attachment of silole functionalities to a dendritic periphery. In addition, dendritic siloles GBn-2ⁿSilole (n = 1-3) based on phenylethynylmethylsilane (PhC=C)₂Me₂Si as cores were synthesized. The building blocks of the dendrimers consisted of double bonds (-PhC=CHMeSi-) in the inner shell and silole groups on the outermost periphery. The generational limit of the dendrimer for the two-branching type core molecule was found to have eight silole groups for the third generation. All of the dendrimers were characterized by ¹H and ¹³C{¹H} NMR, UV spectroscopy, cyclic votammetry (CV), and size exclusion chromatography (SEC). Using this methodology, a series of silole-containing dendrimer systems showing green to greenish-blue fluorescence were synthesized.