Hydrogen bonding and solvation dynamics of n-methylacetamide in denatured water (D₂O) or denatured chloroform (CDCl₃) from nonlinear spectroscopy

Abstract

Hydrogen bonding between N-methylacetamide (NMA) and different solvents (D₂O or CDCl₃) was studied by using two-dimensional infrared spectroscopy to probe the frequency fluctuations of the amide I mode of the solvated NMA. An iterative fitting approach was used to extract a correlation function from the experimental data. The correlation function for NMA/D₂O was found to be biexponential with decay constants of 1050 fs and [approximately]50 fs. These timescales are interpreted as reflecting the collective rearrangement of the solution hydrogen bonding network and oscillation of the hydrogen bond bound to the NMA molecule respectively. The correlation function for NMA/CDCl₃ was found to decay on three timescales with two decay constants of 1600 fs and [approximately]50 fs, and a long time quasi-inhomogeneous component.