Design of a chiral surface by modifying an anionically charged single-layered inorganic compound with metal complexes

We have developed a novel method of modifying a solid surface with a single-layered film of anionic phyllosilicate as an anchor of cationic functional molecules. According to the method, a hybrid film of octadecylammonium and montmorillonite layer was deposited onto a Si substrate by the Langmuir-Blodgett method. Thereafter the Si substrate was immersed in methanol to remove an organic layer, leaving a single-layered montmorillonite film. As a final step, a cationic chiral molecule, Delta-[Ru(phen)(3)](2+) (phen = 1,10-phenanthroline), was self-assembled from its aqueous solution onto the single-layered montmorillonite film. The thickness of a single-layered montmorillonite film was estimated to be ca. 1.5-1.6 nm by atomic force microscopy observation. The thickness of the film increased to ca. 2.6-2.7 nm after the self-assembly treatment. The results were consistent with the analyses of interference oscillation patterns of specular X-ray reflectivity (SXR) curves. From the analyses of SXR curves, the thickness of the adlayer of Delta-[Ru(phen)(3)](2+) was estimated to be ca. 1.5-1.6 nm. On the basis of this, it was concluded that Delta-[Ru(phen)(3)](2+) formed an adlayer within a monolayer scale. The present method may open a way to modify a solid surface by use of a water-soluble functional molecule with neither cross-linking group nor amphiphilic property.