Wang, Jianping; Yang, Fan; Shi, Jipei; Zhao, Juan
Structural dynamics of N-ethylpropionamide clusters examined by nonlinear infrared spectroscopy
JOURNAL OF CHEMICAL PHYSICS, 143 Art. No. 185102, NOV 14 2015

In this work, the structural dynamics of N-ethylpropionamide (NEPA), a model molecule of beta-peptides, in four typical solvents (DMSO, CH3CN, CHCl3, and CCl4), were examined using the N-H stretching vibration (or the amide-A mode) as a structural probe. Steady-state and transient infrared spectroscopic methods in combination with quantum chemical computations and molecular dynamics simulations were used. It was found that in these solvents, NEPA exists in different aggregation forms, including monomer, dimer, and oligomers. Hydrogen-bonding interaction and local-solvent environment both affect the amide-A absorption profile and its vibrational relaxation dynamics and also affect the structural dynamics of NEPA. In particular, a correlation between the red-shifted frequency for the NEPA monomer from nonpolar to polar solvent and the vibrational excitation relaxation rate of the N-H stretching mode was observed. (C) 2015 AIP Publishing LLC.

DOI:10.1063/1.4935579

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