Self-Directed Assembly of Photoactive Hybrid Silicates Derived from an Azobenzene-Bridged Silsesquioxane

Hybrid silicate materials derived from organo-bridged silsesquioxane precursors, RO3−Si−R‘−Si−OR3, where R and R‘ are organic ligands, represent a remarkably diverse class of nanocomposites capable of forming both Si−O−Si and Si−C−Si bonds with molecular scale homogeneity. Recently, in an effort to better control their structure and function, surfactant-directed self-assembly or self-directed assembly has been used to synthesize hierarchical organo-bridged polysilsesquioxanes that exhibit order over multiple length scales. Here we report the synthesis and self-directed assembly of an optically active azobenzene-bridged silsesquioxane, 4,4‘-bis(3-triethoxysilylpropylureido)azobenzene 1. Hydrogen-bonding interactions between the three active centers of the bis-ureide groups (−NH−CO−NH) combined with π−π interactions between the azobenzene groups serve to self-assemble 1 into a highly ordered lamellar mesostructure in which the d-spacing is optically controlled through photoisomerization of the azobenzene moiety before or after assembly.