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Интеллектуальная Система Тематического Исследования НАукометрических данных |
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Conformational analysis of the simplest amides in the ground (S0) and lowest excited (S1, T1) electronic statesтезисы доклада
- Авторы: Tukachev N.V., Bataev V.A., Godunov I.A.
- Сборник: ESPA 2016. 10th Congress on Electronic Structure: Principles and Applications. June 28th to July 1st, 2016. Castellón de la Plana, Spain
- Тезисы
- Год издания: 2016
- Место издания: Castellón de la Plana, Spain
- Первая страница: 151
- Последняя страница: 152
- Аннотация: Formamide (HCONH2), acetamide (CH3CONH2) and N-methylformamide (HCONHCH3) are the first molecules in homological series of amides. Due to this, they are the simplest objects to investigate conformational properties of the peptide fragment. In order to discover conformational preferences of molecules under consideration, one should focus on the so-called large amplitude motions (LAM): torsion, inversion and in some particular cases out-of-plane vibrations. In the ground electronic state (S0) in the simplest amides RCONHR’ (R, R’ = H, CH3) LAMs are as follows: internal rotation around CcarbN bond, rotations of methyl tops in acetamide and N-methylformamide, and out-of-plane vibration of CNHR’ fragment. In concordance with earlier data it was shown that internal rotation around central CN bond is coupled with pyramide-like deformations of CNHR’ group. In addition we calculate 2D potential energy surface (PES) sections by LAM coordinates for molecules mentioned above (ab initio method used is MP2/aug-cc-pVTZ). In S1 (1(n,π*)) and Т1 (3(n,π*)) electronic states PES of amide molecules were computed by means of CASPT2/cc-pVTZ procedure. Electronic excitation was shown to cause strong pyramide-like deformation of both HNCR’ and RCON fragments as well as shift of mutual orientation owing to rotation around CcarbN bond. Our calculation for 1,3(n,π*) states of formamide and acetamide predicted three different minima to exist while for N-methylformamide there are six of them. For all amide conformers in different electronic states geometry parameters, harmonic vibrational frequencies of conformers and barriers to conformational transitions were computed. Based on potential energy surface (PES) sections, LAM frequencies were calculated variationally and found to be close to available experimental data.
- Добавил в систему: Батаев Вадим Альбертович