PHOTOCHEMISTRY ON SURFACES. EXCITED STATE BEHAVIOR OF RUTHENIUM TRIS(BATHOPHENANTHROLINE DISULFONATE) ON COLLOIDAL ALUMINA-COATED SILICA PARTICLES*

Abstract— The excited state behavior of an anionic ruthenium(II) complex, RuL₃^4-(L=bathophen-anthroline disulfonate), that is electrostatically bound to positively charged alumina-coated silica particles is investigated. The apparent association constant for the binding of RuL₃^4-to the particles is 1.2 × 10⁴M^-1. Surface photochemical processes result in decreased emission yields and multiexponential excited state decay. Excited state quenching by ground-state molecules is evident at high surface coverages. The non-exponential decay kinetics observed at low surface coverages can be attributed either to clustering of the RuL₃^4-molecules or photoionization promoted by Lewis acid sites on the particle surface.