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, Δ-[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 Δ-[Ru(phen) 3 ] 2+ was estimated to be ca. 1.5−1.6 nm. On the basis of this, it was concluded that Δ-[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.