Spectra and relaxation dynamics of the pseudohalide (PS) vibrational bands for Ru(bpy)2(PS)2 complexes, PS = CN, NCS and N3

By Compton, Ryan; Gerardi, Helen K.; Weidinger, Daniel; Brown, Douglas J.; Dressick, Walter J.; Heilweil, Edwin J. & Owrutsky, Jeffrey C.
Published in Chemical Physics NULL 2013

Abstract

Static and transient infrared spectroscopy were used to investigate cis-Ru(bpy)2(N3)2 (bpy = 2,2'-bipyridine), cis-Ru(bpy)2(NCS)2, and cis-Ru(bpy)2(CN)2 in solution. The NC stretching IR band for cis-Ru(bpy)2(NCS)2 appears at higher frequency (∼2106 cm-1 in DMSO) than for the free NCS- anion while the IR bands for the azide and cyanide complexes are closer to those of the respective free anions. The vibrational energy relaxation (VER) lifetime for the azide complex is found to be much shorter (∼5 ps) than for either the NCS or CN species (both ∼70 ps in DMSO) and the lifetimes resemble those for each corresponding free anion in solution. However, for cis-Ru(bpy)2(N3)2, it is determined that the transition frequency depends more on the solvent than the VER lifetime implying that intramolecular vibrational relaxation is predominant over solvent energy-extracting interactions. These results are compared to the behavior of other related metal complexes in solution.

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