ELECTRON AND ENERGY-TRANSFER AS PROBES OF INTERPARTICLE ION-EXCHANGE REACTIONS IN ZEOLITE-Y

Photoinduced electron transfer and energy transfer reactions of tris(2 ,2'-bipyridyl)ruthenium(II) (Ru(bpy)3(2+)) with methylviologen (MV2+) and tris(2,2-bipyridyl)osmium(II) (Os(bpy)3(2+)) ion-exchanged onto/in to separate zeolite Y particles were studied by emission spectroscopy. The kinetics of interparticle exchange were probed by observing the q uenching of the MLCT excited state of Ru(bpy)3(2+) by mobile MV2+ or O s(bpy)3(2+) ions. The exchange reactions occur on time scales of secon ds to hours, depending on the ionic strength of the surrounding medium . The time-dependent luminescence data were fitted to a dispersed kine tics model, from which average rate constants for the exchange reactio ns could be extracted. Time constants for interparticle exchange of MV 2+ and Os(bpy)3(2+) ions, in the range 10(3)-10(5) S at electrolyte co ncentrations of 0. 1-3 mM, are significantly longer than the time scal es (10(-7)-10(1) s) of most electrochemical and photochemical intrazeo litic reactions involving these and similar electroactive ions. These results argue for reaction mechanisms that invoke intrazeolite electro n transfer, rather than exchange of electroactive ions followed by sol ution-phase electron transfer, in these systems.