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 (pypz) 2+ complex is reported, where bpy = 2,2‘-bipyridine and pypz = 2-(2-pyridyl)pyrazine. The integrity of the sample was documented by UV−visible, emission, resonance Raman (RR), and time-resolved resonance Raman (TR 3 ) spectroscopic data, as well as lifetime measurements. The Raman spectrum for the ground-state Z−Ru(bpy) 2 (pypz) 2+ intrazeolitic complex, with laser excitation at λ ex = 413.1 and 488.0 nm, closely matched that obtained for the free [Ru(byp) 2 (pypz)]Cl 2 complex, with some bands exhibiting slight frequency shifts of 2−5 cm - 1 . This finding indicates that the structure of the Ru 2+ complex does not change substantially upon entrapment in the Y-zeolite supercages. On the 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 measurements revealed a 210 ns increase of the triplet excited-state ( 3 MLCT) lifetime. These data suggest perturbation of the Ru(byp) 2 (pypz) 2+ complex electronic structure, presumably induced by interaction of the peripheral N heteroatom with the zeolite framework. Temperature-dependent lifetime measurements indicated that decay via the thermally populated, so-called, “fourth MLCT state” (4th-MLCT) was dominant both for the Ru(bpy) 2 (pypz) 2+ complex in solution and for the complex entrapped within the zeolite supercages.