Density Functional Theory Vibrational Frequencies of Amides and Amide Dimers

摘要: Infrared spectra of amides and polypeptides can provide detailed information on conformation. An understanding the amide group in model compounds is a vital step toward deeper insight into vibrational proteins. We show that contrast to MP2 popular B3LYP functional, which overestimate I frequencies by 20−80 cm-1, recently developed empirical density EDF1, yields unscaled harmonic monoamides close agreement with experimental data, even using relatively small 6-31+G* basis set. New calculations several hydrogen-bonded dimers data available for these also support conclusion EDF1 better experiment than or B3LYP. present calculated minimum-energy structures N-acetylglycine-N‘-methylamide N-acetyl-l-alanine-N‘-methylamide at EDF1/6-31+G* B3LYP/6-31+G* levels.