title: Structural dynamics of N-ethylpropionamide clusters examined by nonlinear infrared spectroscopy.
abstract: In this work, the structural dynamics of N-ethylpropionamide (NEPA), a model molecule of β-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.
authors.affiliation: Beijing National Laboratory for Molecular Sciences, Molecular Reaction Dynamics Laboratory, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, People's Republic of China.
authors.forename: Jianping
authors.initials: J
authors.lastname: Wang
authors.affiliation: Beijing National Laboratory for Molecular Sciences, Molecular Reaction Dynamics Laboratory, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, People's Republic of China.
authors.forename: Fan
authors.initials: F
authors.lastname: Yang
authors.affiliation: Beijing National Laboratory for Molecular Sciences, Molecular Reaction Dynamics Laboratory, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, People's Republic of China.
authors.forename: Jipei
authors.initials: J
authors.lastname: Shi
authors.affiliation: Beijing National Laboratory for Molecular Sciences, Molecular Reaction Dynamics Laboratory, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, People's Republic of China.
authors.forename: Juan
authors.initials: J
authors.lastname: Zhao
mesh_terms: D008958:Models, Molecular; D015394:Molecular Structure; D010455:Peptides / Q000737:chemistry; D011422:Propionates / Q000737:chemistry*; D011789:Quantum Theory; D013055:Spectrophotometry, Infrared
chemical_list: C000608832:N-ethylpropionamide; D010455:Peptides; D011422:Propionates