Ultrafast vibrational dynamics of a solute correlates with dynamics of the solvent

Two-dimensional infrared (2D-IR) spectroscopy is used to measure the spectral dynamics of metal carbonyl complex cyclopentadienyl manganese tricarbonyl (CMT) in a series linear alkyl nitriles. 2D-IR provides direct readout solvation through diffusion, probing decay frequency correlation induced by fluctuations solvent environment. simultaneously monitors intramolecular vibrational energy redistribution (IVR) among excited vibrations, which can also be influenced density rather than dynamical friction underlying solvation. Here, we report that CMT probe reveals dependences both diffusion and IVR time scales, where each slows with increased chain length. In order assess degree solute–solvent interactions correlated bulk properties, compared our results low-frequency obtained from optical Kerr effect (OKE) spectroscopy—performed others—on same nitrile series. We find excellent between orientational scales OKE. amplitudes densities evaluated at 90-cm−1 difference, corresponding gap two strong modes probe. OKE provide complementary perspectives on condensed phase dynamics, these findings experimental evidence least level correlations, some aspects solute inferred properties solvent.