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Shape of Potential Energy Surfaces and Conformational Dynamics of Simplest Amides Molecules in the Ground and Excited Electronic Statesтезисы доклада
- Авторы: Tukachev N.V., Bataev V.A., Godunov I.A.
- Сборник: XVII Symposium on High Resolution Molecular Spectroscopy HighRus-2012: Abstracts of Reports. - Tomsk: Institute of Atmospheric Optics SB RAS, 2012
- Тезисы
- Год издания: 2012
- Место издания: Типография ИОА СО РАН Томск
- Первая страница: 156
- Последняя страница: 156
- Аннотация: The structure and conformational dynamics of the formamide (HCONH2), acetamide (CH3CONH2) and N-methylformamide (HCONHCH3) molecules in the ground and lowest excited n,π* electronic states were investigated by high level ab initio methods (MP2, CCSD(T), CASSCF, CASPT2, etc.). The geometric structure of heavy atoms frames of molecules under investigation in the ground electronic state is planar (or near-planar), but the torsion motion of the amino group is accompanied by significant pyramidalization of CNRR' fragments. As a result, for example, in formamide molecule the torsion and NH2 out-of-plane vibrations are strongly coupled and therefore we solved two-dimensional problem in anharmonic approximation by variational method. The different ways of the internal coordinate choosing and its influence to vibrational problem results are discussed. The comparison of our results with those obtained by other methods demonstrated that only our and VibMP2 results are in good agreement with experimental data. Geometric parameters, conformer energy differences, and one- and two-dimensional potential energy surfaces (PES) sections along the coordinate of large-amplitude motions of formamide, acetamide and N-methylformamide in the lowest excited electronic states were obtained. Our calculations demonstrate that the electronic excitations cause pyramidal distortions of the carbonyl and amino fragments and change of these group orientation. An analysis of the potential energy surface shows that the coupling the internal rotation about the C-N bond and the non-planar vibrations of amides in these excited electronic states is much weaker than in the ground state. The degree of conjugation in molecules under investigation in different electronic states was compared based on topological analysis of electron density (Bader’s Quantum Theory of Atoms in Molecules, QTAIM) and population analysis of the natural bond orbitals theory (NBO).
- Добавил в систему: Батаев Вадим Альбертович