Solvent controlled aggregation behavior of peptide bond simulant N-methylacetamide and vibrational coupling splitting theory
Wang, HG (Wang, Huigang); Liu, RR (Liu, Ruirui); Han, YF (Han, Yufei); Tan, Y (Tan, Yao); Zhang, SS (Zhang, Shishen); Jiang, CY (Jiang, Caiying); Zheng, XM (Zheng, Xuming)
Journal of Molecular Liquids, 2021, Volume 337, 116436.
Quantum state of C = O streching presents as two entangled quantum states, one is in phase and another is out phase when adjacent C = O coupled in aggregated dimers form. As the simplest model molecules of peptide, N-methylacetamide in binary mixture were chosen to investigate the intermolecular C = O coupling. The isotropic and anisotropic Raman spectra of N-methylacetamide/CCl4, N-methylacetamide/ methanol, N-methylacetamide/ acetonitrile, N-methylacetamide/ methanol and N-methylacetamide/ water binary mixture at different concentrations have been obtained. It was found that the quantum frequencies and strength of quantum entanglement could be continuously tuned span < 35 cm(-1) by adjusting concentrations or selecting solvent. According to Delta(r)G(m) = Delta H-r(m)-T Delta S-r(m), only the solvent having good solvation or forming H-bond to solute could lower the Delta H-r(m) or Delta(r)G(m) sufficiently so as to favor the entangled dimers breaking. The geometries of solvated and H-bonded monomers and dimers of Nmethylacetamide were calculated at the B3LYP-D3/6-311G (d,p) level of theory. The isotropic and anisotropic Raman splitting phenomenon of the N-methylacetamide C = O vibration and their concentrations effects can be explained by presently proposed aggregation model and the calculations. This study is expected to be applied to the structural identification, the solvent controlled physical and chemical processes of molecules in solution phase, quantum communication and basic thermodynamics teaching experiments. (C) 2021 Elsevier B.V. All rights reserved. |
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