| Abstrakt: |
This report documents the spectroscopic and photophysical properties of the complexes, Ru(bpdz)32+ and [Ru(bpy)2(bpdz)]2+, where bpdz = 3,3-bipyridazine and bpy = 2,2-bipyridine. Specifically, the complexes were characterized by UV−visible, emission, resonance Raman (RR), and transient resonance Raman (TR3) spectroscopic data, as well as lifetime measurements. The RR spectrum of the Ru(bpdz)32+ complex documents the characteristic modes of the coordinated ligand, whereas the RR spectra of the heteroleptic complex, [Ru(bpy)2(bpdz)]2+, obtained at judiciously chosen excitation wavelengths, reveal selective enhancement of either bpy modes or bpdz modes, depending upon the particular excitation wavelength, permitting definitive assignment of the observed electronic absorption bands and establishing the lowest energy electronic transition as having a Ru-to-bpdz charge-transfer character. The TR3 spectrum of the Ru(bpdz)32+ complex reveals the characteristic frequencies of the coordinated bpdz-• anion radical, as expected, whereas corresponding studies of the heteroleptic complex, [Ru(bpy)2(bpdz)]2+, reveal these characteristic bpdz-• modes in the absence of any modes attributable to bpy-• anion radicals, providing definitive evidence for the [Ru(III)(bpy)2(bpdz-•)]2+ formulation of the excited state of this complex. Lifetime measurements for both complexes, made over a wide range of temperatures and interpreted with a model derived from previous measurements made on a large number of similar complexes, indicate that the two complexes of interest decay by different nonradiative pathways resulting from thermal population of a ligand field 3dd and/or a lower lying 4th 3MLCT state. |
