Characterization of Ir(ppy)3 and [Ir(ppy)2 bpy]+ by infrared, Raman spectra and surface‐enhanced Raman scattering

Abstract The Raman and infrared spectra of fac ‐tris(2‐phenylpyridinato‐N,C2′)iridium(III), Ir(ppy) 3 and surface‐enhanced resonance Raman spectra of bis(2‐phenyl pyridinato‐) (2,2′bipyridine) iridium (III), [Ir(ppy) 2 (bpy)] + cation were recorded in the wavenumber range 150–1700 cm −1 , and complete vibrational analyses of Ir(ppy) 3 and [Ir(ppy) 2 (bpy)] + were performed. Most of the vibrational wavenumbers were calculated with density‐functional theory agree with experimental data. On the basis of the results of calculation and comparison of the spectra of both complexes and their analogue [Ru(bpy) 3 ] 2+ , we assign the vibrational wavenumbers for metal–ligand modes; metal–ligand stretching wavenumbers are 277/307 and 261/236 cm −1 for Ir(ppy) 3 , and 311/324, 257/270, 199/245 cm −1 for [Ir(ppy) 2 bpy] + . Surface‐enhanced Raman scattering spectra of [Ir(ppy) 2 bpy] 2+ were measured at two wavelengths on the red and blue edges of the low‐energy metal‐to‐ligand charge‐transfer band. According to the enhanced Raman intensities for the vibrational modes of both ligands ppy and bpy, the unresolved charge‐transfer band is deduced to consist of charge‐transfer transitions from the triplet metal to both ligands ppy and bpy. Copyright © 2010 John Wiley & Sons, Ltd.