In resonance Raman (RR) spectroscopy, the laser excitation sources have often been found to be destructive towards polyiodides if compared with the milder conditions under which the Fourier transform Raman (FT-R) technique operates. In fact, our FT-R spectra of some model polyiodides—[(CH3)4N]I5 (I5− bent), [(C2H5)4N]I7, and [(CH3)4N]I9—are significantly different from the literature RR data, give evidence of decomposition of the samples in RR, and are in agreement, respectively, with the I− · 2I2, I3− · 2I2 and (I− · 2I2) · 2I2 descriptions. In addition to the above-cited cases, the FT-R spectra of (Mn(modtc)3]Is (modtc = morpholine carbodithioato) and (moH]I5 (moH = morpholinium) are reported. The crystal structures indicate that in these two compounds the I5 anions can be properly described as I− · 2I2 and I3− · I2, respectively, and FT-R spectra agree well with this formulation. Moreover, the first FT-R spectrum of an I164– anion in [mo2ttl]2I16, ([mo2ttl]2+ = 3,5-di( N-morpholinio)-1,2,4-trithiolane), whose X-ray structure shows a sequence of two I3− … I2 … I− ·I2 (I82–) interacting anions, is reported. A close correlation of the FT-Raman peaks with the molecular species, identified by the interatomic distances, is also observed in this case. Thus, a combination of X-ray structural data and FT-R data can provide a reasonable interpretation of the nature of the acceptor iodine moiety in charge-transfer polyiodide complexes.
Resonance Raman study of the solvent dynamics for ultrafast charge transfer transition in 4-nitro-4′-dimethylamino-azobenzene