title: Orientation tuning of a polypyridyl Ru(II) complex immobilized on a clay surface toward chiral discrimination.
abstract: The present work reports an attempt to elucidate a stereoselective energy-transfer system by immobilizing a chiral metal complex on a clay surface. The metal complex used was [Ru(bpy)2L(i)]2+ with L1 = bpy (2,2'-bipyridine), L2 = 4,4'-diundecyl-2,2'-bipyridine, and L3 = 5,5'-diundecyl-2,2'-bipyridine. The adsorption structure of [Ru(bpy)2L(i)]2+ was studied by means of electric dichroism measurements on an aqueous dispersion of a colloidal clay. It was found that the molecular orientation of the adsorbed Ru(II) complex was affected remarkably by the positions of the alkyl chains on the bpy ligand; that is, the angle of the 3-fold or pseudo-3-fold symmetry axis of the Ru(II) complex with respect to the surface normal was obtained to be 24 degrees, 30 degrees, and 52 degrees for i = 1, 2, and 3, respectively. The efficiency of the energy-transfer was determined by photoluminescence quenching measurements between the adsorbed Ru(II) complex and [Ru(acac)3] (acac = acetylacetonate) in solution. As a result, stereoselectivity appeared most for the case of [Ru(bpy)2L3]2+ in which its two helically twisted bpy ligands were projected in an outward direction.
authors.affiliation: Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo, Tokyo 113-0033, Japan. h-sato@esp.s.u-tokyo.ac.jp
authors.forename: Hisako
authors.initials: H
authors.lastname: Sato
authors.forename: Yoshihisa
authors.initials: Y
authors.lastname: Hiroe
authors.forename: Kenji
authors.initials: K
authors.lastname: Tamura
authors.forename: Akihiko
authors.initials: A
authors.lastname: Yamagishi