The influence of the intrinsic self-assembling properties of rigid or semirigid aromatic units as the main substructures combined with the effect of the alkylene side chains as linkers on the nanostructure of bridged silsesquioxanes was studied. The symmetry of the organic units was found to control the dimensionality of the hybrid nanostructure. Bis(silyl-Eur. Synthesis of the Molecular Precursors P1-6 and the Corresponding Hybrid Bridged Silsesquioxanes HS1-6Bis(silylated) molecular precursors P1-4 were synthesised from commercially available diamines (benzidine and 4,4Ј-methylenedianiline) by treatment with 2 mol-equiv. of (3-isocyanopropyl)triethoxysilane or (10-isocyanodecyl)triethoxysilane (Scheme 2). Tris(silylated) precursors P5 and P6 were obtained by reaction of (1,3,5-triisocyano)benzene with (3-aminopropyl)triethoxysilane or (11-aminoundecyl)triethoxysilane, respectively. [15] These reactions were performed at room temperature in CH 2 Cl 2 under argon and led to bis-or tris(urea)-based precursors P1-6 with yields of up to 75 %. www.eurjic.org