Many "vibrational probes" from functional groups with unique vibrational frequencies can report in different ways and with varying sensitivity on the atomic details of aqueous dynamics and H-bonding interactions.  While some of these signals (i.e. the asymmetric azido stretching mode and the CN stretch of nitriles) display strong dependences on H-bonding environment, the true physical root of frequency shifts associated with H-bonding is often ambiguous.  This talk will highlight and compare recent observations of H-bond effects on IR or Raman signals from several probe groups, including (but not limited to) nitriles, azides, and nitro groups across a number of different systems.  We will also discuss simulation strategies based on MD simulations and effective fragment potential-based frequency calculations that allow a piecewise and detailed understanding of the physical basis for why these signals shift and what they can actually report.  An intrinsic but often overlooked reporter from condensed water, its bend+libration combination band whose mean frequency directly reports on the rigidity of the H-bond network, will also be compared and contrasted in some of the same systems.

H-bond details and dynamics via artificial and intrinsic IR and Raman probes

2019 Fall National Meeting

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