Preparation and monolayer properties of surfactant tris(2,2'-bipyridine)ruthenium(II) derivatives

The synthesis, characterization, and monolayer properties of three ruthenium bipyridyl complexes possessing hydrolytically stable surfactant linkages and differing molecular charges are described: (Ru/sup II/(bpy)/sub 2/(bpy(C/sub 19/H/sub 3992/))/sup 2 +/, 2; (Ru/sup II/(bpy)(CN)/sub 2/(bpy(C/sub 19/H/sub 39/)/sub 2/))/sup 0/, 3; and (Ru/sup II/(bpy(COO/sup -/)/sub 2/)/sub 2/(bpy(C/sub 19/H/sub 39/)/sub 2/))/sup 2 -/, 4. Field-desorption mass spectra are reported for these and other nonvolatile ruthenium bipyridyl complexes. While the monolayer absorption spectra show no significant changes (except for iodide), both the surface pressure-area (II-A) isotherms and luminescence spectra of 2 are strongly dependent on dissolved anions; perchlorate is observed to condense the films and provide higher emission intensity as compared to chloride. Such effects are unique to the interfacial environment and are not observed in homogeneous solutions of 2. In contrast, the II-A isotherm and luminescence of 3 are independent of anion. The II-A isotherm of 4 does not show significant differences for subphases containing either Na/sup +/ or Ca/sup 2 +/. The emission intensity and maximum of 4 in 20% aqueous THF solution are pH dependent.