Inorganic Chemistry, Vol.37, No.5, 859-864, 1998
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 (TR3) 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 lambda(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 Ru2+ 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 ((MLCT)-M-3) 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.
Keywords:3MLCT EXCITED-STATES;RUTHENIUM(II) COMPLEXES;SPECTROSCOPIC PROPERTIES;POLYPYRIDINE COMPLEXES;REDUCING AGENTS;RESONANCE RAMAN;CHARGE-TRANSFER;SODIUM HYDRIDE;LIGANDS;TRIS(BIPYRIDINE)RUTHENIUM(II)