The photophysical properties of the chromophores [Ru(bpy)(2)(4,4’-(CO2H)(2)bpy)](PF6)(2) [(4,4’-(CO2H)(2)bpy) is 4,4’-dicarboxy-2,2’-bipyridine], [Re(4,4’-(CO2H)(2)bpy)(CO)(3)(4-Etpy)](PF6) (4-Etpy is 4-ethylpyridine), and the chromophore-quencher complex [Re(4,4’-(CO2H)(2)bpy)(CO)(3)(py-PTZ)](PF6) have been investigated on high surface area silica particles with 1,2-dichloroethane (DCE) as the external solvent for the index of refraction matching. Surface coverages were estimated by direct absorption measurements with DCE as the external solvent. Decay of the metal-to-ligand charge transfer (MLCT) excited state of [Ru(bpy)(2)(4,4’-(CO2H)(2)bpy)](PF6)(2) on silica is exponential and independent of surface coverage from Gamma = 1.5 x 10(-4) to 1.3 x 10(-13) mol . cm(-2). For [Re(4,4’-(CO2H)(2)bpy)(CO)(3) (4-Etpy)](PF6), MLCT emission shifts from 600 nm in DCE to 605 nm on silica and tau decreases from 487 to 255 ns. On surfaces containing both the Ru complex and the electron transfer quenchers N-methyl-N-viologenpropanoic acid bis(hexafluorophosphate) [MV-CO2H](PF6)(2) or 3-(10H-phenothiazin-9-yl)propanoic acid, PTZ-CO2H, there is no evidence for cross-surface quenching from lifetime measurements. The transient absorption difference spectrum acquired following laser flash photolysis of [Re(4,4’-(CO2H)(2)bpy)(CO)(3)(py-PTZ)]-(PF6) on silica resembles the spectrum in DCE, with absorptions appearing for bpy(.-) at similar to 360 nm (with an additional shoulder at similar to 390 nm) and PTZ(.+) at similar to 520 nm. These features are consistent with formation of the redox-separated state [Re(4,4’-(CO2H)(2)bpy(.-))(CO)(3)(py-PTZ)(+)](+). It returns to the ground state by bpy(.-) --> PTZ(+) electron transfer with k = 2.9 x 10(7) s(-1).