A patent procedure was followed to synthesize 250 nm aggregates of individual 13 +/- 2.5 nm crystallites of zeolite X. A low-temperature aging step and addition of sucrose to the reaction mixture were required to get optimum quality of crystals. Conventional ship-in-a-bottle synthesis of Ru(bpy)(3)(2+) in the cages of these nanocrystallites resulted in considerable framework degradation, with only 10% of the crystallinity in the original crystals being retained. The degradation occurred due to exposure to mild acidity and thermal treatment during synthesis of RU(bpy)(3)(2+). The procedure was modified to avoid acidity in the initial ion-exchange step of RU(NH3)(6)(3+), resulting in a Ru(bpy)(3)(2+)-zeolite with 75% of the crystallinity retained. Acidity generated during conversion of Ru(NH3)(6)(3+) to Ru(bpy)(3)(2+) was thought to be responsible for the degradation, A third procedure starting with the highly air-sensitive Ru(NH3)(6)(2+) resulted in formation of Ru(bpy)(3)(2+)-zeolite with about 90% crystallinity. In all three procedures, the RU(bpy)(3)(2+) molecules were entrapped within the framework. Ion exchange of viologen molecules and the fluorescence quenching of photoexcited Ru(bpy)(3)(2+) by intrazeolitic viologen increased with the increase of zeolite crystallinity. Interfacial zeolite-solution electron transfer upon visible light photoexcitation of the Ru(bpy)(3)(2+)-zeolite-viologen system demonstrated an increase in permanent charge separation efficiency as the crystallinity of the zeolite is preserved. Because of the higher surface-to-volume ratios, the charge separation efficiency in the nanocrystallites was a factor of 2 better than conventional micron-sized zeolite Y crystallites under identical photolysis conditions.