Infrared spectroscopy of N-methylacetamide in water from high-level QM/MM calculations

The infrared (IR) spectra of the N-methylacetamide molecule in water are calculated by using the MD simulation with high-level QM/MM corrections. The B3LYP and MP2 levels with 6-311++G** basis set are used for the QM region, respectively. Our results show all IR spectra at the B3LYP level are well consistent with the corresponding MP2 results. A dynamical charge fluctuation is observed for each atom along the simulation trajectories due to the electrostatic polarization (EP) effects from surrounding solvent environment. We find that the QM/MM corrected IR spectra satisfactorily reproduce the experimental vibrational features of amide I-III modes. (C) 2013 Zhen Yang. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.