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Hydrogen bonding dynamics and two‐dimensional vibrational spectroscopy: N ‐methylacetamide in liquid methanol
Author(s) -
Kwac Kijeong,
Cho Minhaeng
Publication year - 2005
Publication title -
journal of raman spectroscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.748
H-Index - 110
eISSN - 1097-4555
pISSN - 0377-0486
DOI - 10.1002/jrs.1303
Subject(s) - solvation , chemistry , hydrogen bond , dissociation (chemistry) , molecular dynamics , molecular vibration , raman spectroscopy , spectral line , chemical physics , solvent , thermodynamics , computational chemistry , molecule , organic chemistry , physics , astronomy , optics
Abstract The distribution of the fluctuating amide I mode frequency of N ‐methylacetamide (NMA)–methanol solution at room temperature was recently found to be non‐Gaussian and can be decomposed into two Gaussians that are associated with two different solvation structures. In the present paper we discuss the temperature dependences of hydrogen bonding dynamics and their influences on one‐ and two‐dimensional vibrational spectra by carrying out molecular dynamics simulations of the same solution at five temperatures from 230 to 310 K. The radial distributions reveal the detailed solvent configuration around the NMA. The two‐species model where conformational transitions between the two distinct solvation structures are treated as a reversible reaction and the Onsager regression hypothesis was used to estimate the hydrogen bond association and dissociation rates and to study thermodynamic properties. By using the time evolution of the amide I mode frequency fluctuation, both IR absorption and two‐dimensional IR photon echo spectra were numerically simulated and compared with approximate two‐species model results. An approximation method that can be used to extract kinetic information of the hydrogen bonding dynamics from the spectra is briefly discussed. Copyright © 2005 John Wiley & Sons, Ltd.