PREPARATION AND PHOTOPHYSICAL CHARACTERIZATION OF A Y-ZEOLITE-ENTRAPPED RU(BPY)(2)(PYPZ)(2+) COMPLEX

In this work, the generation of a new Y-zeolite-entrapped Ru(bpy)(2)(p ypz)(2+) complex is reported, where bpy 2,2'-bipyridine and pypz = 2-( 2-pyridyl)pyrazine. The integrity of the sample was documented by UV-v isible, emission, resonance Raman (RR), and time-resolved resonance Ra man (TR3) spectroscopic data, as well as lifetime measurements. The Ra man spectrum for the ground-state Z-Ru(bpy)(2)(pypz)(2+) intrazeolitic complex, with laser excitation at lambda(ex) = 413.1 and 488.0 nm, cl osely matched that obtained for the free [Ru(byp)(2)(pypz)]Cl-2 comple x, with some bands exhibiting slight frequency shifts of 2-5 cm(-1). T his finding indicates that the structure of the Ru2+ complex does not change substantially upon entrapment in the Y-zeolite supercages. On t he other hand, the emission spectroscopic investigation revealed a 16 nm blue shift of the Z-Ru(bpy)(2)(pypz)(2+) phosphorescence, relative to that of the free [Ru(bpy)(2)(pypz)]Cl-2 complex, and the lifetime m easurements revealed a 210 ns increase of the triplet excited-state (( MLCT)-M-3) lifetime. These data suggest perturbation of the Ru(byp)(2) (pypz)(2+) complex electronic structure, presumably induced by interac tion of the peripheral N heteroatom with the zeolite framework. Temper ature-dependent lifetime measurements indicated that decay via the the rmally populated, so-called, ''fourth MLCT state'' (4th-MLCT) was domi nant both for the Ru(bpy)(2)(pypz)(2+) complex in solution and for the complex entrapped within the zeolite supercages.