Interaction between monomers of two surfactants derived from the [Ru(2,2′-bpy)3]2+ complex and α, β and γ-cyclodextrins: formation of [2]- and [3]-pseudorotaxanes

Two new surfactants derived from the tris(2,2'-bipyridine) ruthenium(II) complex, [Ru(2,2'-bpy)(3)](2+), were synthesized and characterized: the double-tailed [Ru(2,2'-bipy)(2)(4,4'-(C11H23)(2)-2,2'-bipy)](2+) surfactant (RuC11) and the mono-tailed [Ru(2,2'-bipy)(2)(4-(CH3)-4'-(C13H27)-2,2'-bipy)](2+) surfactant (RuC13). The main characteristic of these species is the presence of an inorganic complex as the polar head of the surfactant with interesting luminescence properties, which were used to study the interaction of these cationic surfactants with alpha-, beta- and gamma-cyclodextrins (CD). The results showed the formation of [2]- and [3]-pseudorotaxanes. The binding constant values as well as the stoichiometry of the complexes formed were obtained; the results were confirmed, from a qualitative point of view, with NMR spectra.