Quenching of Tris(2,2'-bipyridine)ruthenium(II) Luminescence by Cobalt(III) Polypyridyl Complexes in Different Sites in and on Clays

Abstract

The effect of quenching of tris(2,2'-bipyridine)ruthenium(II) [Ru(bpy)_3^(2+)] luminescence by Co(phen)_3^(3+) in various locations in and on bentolite-H clay has been investigated. Ru(bpy)_3^(2+) incorporated into the interlayer region of bentolite-H by ion exchange exhibited spectral properties that were distinct from the Ru(bpy)_3^(2+) incorporated by incipient wetness methods. For example, the samples showed different diffraction, luminescence emission, and lifetime decays. The method of preparation, the nature of counterion (chloride or cyanide), and the presence of a quencher [Co(phen)_3^(3+) influence the emission properties. For example, incipient wetness methods allow deposition on outer surfaces (OUT) of the clay whereas ion-exchange leads to deposition primarily in the interlayer spacing (IN) based on spectroscopic and diffraction data. The luminescence intensities and lifetimes decrease in the order Ru(0UT) > Ru(IN) > Ru(OUT)/Co(IN) > Ru(IN)/Co(0UT) > Ru(OUT)/Co(OUT) ≃ Ru(IN)/Co(IN). Different methods of preparation and treatment result in location of Ru(bpy)_3^(2+) at different internal or external sites in the clay which give different luminescence and lifetime properties. By controlling the locations of Ru(II) and Co(III) (inside or outside), the quenching rates could be modulated. The location of the Ru(II) complex seems to control both the photophysical properties and the efficiency and rate of quenching by Co(III). The Ru(IN) and Co(IN) sample is very similar to the Ru(OUT) and Co(OUT) sample. These two samples are considerably different from the Ru(IN)/Co(OUT) sample and the Ru(OUT)/Co(IN) sample.