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Интеллектуальная Система Тематического Исследования НАукометрических данных |
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Vibrational Dynamics of N-methylacetamide in the Ground S0 and Lowest Excited S1 and T1 Electronic Statesтезисы доклада
- Авторы: Tukachev N.V., Bataev V.A., Godunov I.A.
- Сборник: International Conference on Many Particle Spectroscopy of Atoms, Molecules, Clusters and Surfaces (MPS2016). M.V. Lomonosov Moscow State University. Moscow, Russian Federation, 23-26 August, 2016. Book of Abstracts
- Тезисы
- Год издания: 2016
- Место издания: KDU, University Book Moscow
- Первая страница: 101
- Последняя страница: 101
- Аннотация: Peptides and simple amides photoisomerize in aqueous solution to the less stable cis isomers during 220 nm ultraviolet resonance Raman experiments ([1]). This observation leads us to reinvestigate one of the simplest model compound for peptides – N-methylacetamide (CH3CONHCH3). Thus, structure and vibrational dynamics of the N-methylacetamide molecule in the ground (S0) and lowest excited singlet S1 and triplet T1 electronic states were studied by means of different ab initio methods. Among all amide vibrations, there are some large amplitude motions (LAM). These motions are known to play important role in describing the dynamics of conformationally non-rigid molecules. To treat with these motions properly one should take into account their anharmonicity. In present paper we variationally solve vibrational problem using model Hamiltonian like following where n = 1, 2, 3 is the dimension of problem considered, Bij — kinematic parameters, whereas V is the potential function. For the N-methylacetamide molecule in the ground state four LAM such as internal rotation around CcarbN, CmetN and CC bonds as well as out-of-plane NH vibration were described in detail. Based on potential energy surface (PES) sections by LAM coordinates calculated by MP2/aug-cc-pVTZ, vibrational levels energies and corresponding wave functions were calculated variationally. Electronic excitation to S1 and T1 states was shown to cause strong pyramide-like deformation of both HNCC and CCON fragments as well as shift of mutual orientation owing to rotation around CcarbN bond [2]. Our calculation for S1 and T1 states of N-methylacetamide predicted six different minima to exist (Fig. 1). Geometry parameters of these conformers were determined and 1D and 2D PES sections by coordinates describing internal rotations and pyramide-like deformations of the given molecule were calculated by means of CASPT2/cc-pVTZ method. PES shape analysis reveals that the couplings of considered large amplitude motions of the N-methylacetamide molecule in the ground and excited electronic states have different nature, namely in S0 state internal rotation around central CN bond results in strong pyramide-like deformation of HNCC whereas in excited S1 and T1 electronic states mentioned rotation has very limited influence on non-planar CCON and HNCC fragments.
- Добавил в систему: Батаев Вадим Альбертович