Synthesis and Spectroscopic Characterization of a Zeolite-Entrapped Ru(bpy)2(dpp)2+ Complex

The heteroleptic ruthenium(II) complex Ru(bpy)2(dpp)2+ (where bpy = 2,2‘-bipyridine and dpp = 2,3-bis(2-pyridyl)pyrazine) has been prepared in the supercages of Y-zeolite and characterized by diffuse reflectance, electronic absorption, electronic emission, and resonance Raman (RR) spectroscopy, as well as lifetime measurements. The spectral results confirm the identity of the entrapped complex. The diffuse reflectance spectrum of the zeolite-entrapped complex is slightly red-shifted in the visible region compared to the absorption spectrum of the free complex in water solution. The emission maximum for the zeolite-entrapped complex is red-shifted by 16 nm with respect to the complex in water solution and by 38 nm relative to the complex in acetonitrile solution. The emission maximum for a zeolite surface-adsorbed complex is blue-shifted by 12 nm with respect to the complex in water solution, but the emission maxima of the liberated complex after dissolution of the zeolite matrix, for both the entrapped and adsorbed complexes, are identical to the spectrum of the free complex in water solution. There are moderate RR frequency shifts observed for the zeolite-entrapped complex relative to the solution-phase complex as a consequence of the interaction of the complex with the zeolite framework. The excited state lifetime measurement shows no dramatic changes upon entrapment within the zeolite supercages. Temperature-dependent lifetime measurements indicate that the excited state decays via two thermally accessible upper states.