Equilibrium molecular structure and spectra of 6-methyl-1,5-diazabicyclo[3.1.0]hexane: joint analysis of gas phase electron diffraction, quantum chemistry, and spectroscopic data

Khaikin, L.S.; Ageev, G.G.; Rykov, A.N.; Grikina, O.E.; Shishkov, I.F.; Kochikov, I.V.; Kuznetsov, V.V.; Makhova, N.N.; Bukalov, S.S.; Leites, L.A.

Авторы: Khaikin Leonid S., Ageev Georgiy G., Rykov Anatoliy N., Grikina Olga E., Shishkov Igor F., Kochikov Igor V., Kuznetsov Vladimir V., Makhova Nina N., Bukalov Sergei S., Leites Larisa A.
Журнал: Physical Chemistry Chemical Physics
Том: 22
Год издания: 2020
Издательство: Royal Society of Chemistry
Местоположение издательства: United Kingdom
Первая страница: 22477
Последняя страница: 22492
DOI: 10.1039/d0cp04005c
Аннотация: The equilibrium geometry of the boat conformation (Cs point group symmetry) of the 6-methyl-1,5-diazabicyclo[3.1.0]hexane (MDABH) molecule, absolutely dominating under normal conditions, was studied by the gas-phase electron diffraction (GED) method at 20 °C with the involvement of NMR, IR, and Raman spectroscopic data and quantum chemical calculations. The potential function of ring-puckering deformation for the MDABH bicyclic system was calculated at the MP2/aug-cc-pVTZ and B3LYP/cc-pVTZ levels. It was found by MP2 calculation that the total energy of the boat conformation is 3.52 kcal mol−1 lower than that of the chair conformation. For the first time, we recorded the IR and Raman spectra for liquid samples of MDABH and assigned their peculiarities only to boat conformation vibrations using the Pulay technique of scaling quantum chemical force fields. In the case of the chair form, transferability of the refined scale factors was used for reliable prediction of the location of its fundamental frequencies. According to the joint structural analysis of the above data, the most important equilibrium geometric re-parameters for the boat conformation of the MDABH molecule were determined to be (bond lengths in Å; angles in degrees, Cs symmetry): C2N1 = 1.466(2), C2C3 = 1.523(2), N1N5 = 1.512(2), C6N1 = 1.440(2), C6C7 = 1.487(2), ∠C2N1N5 = 106.1(2), ∠N1C2C3) = 110.2(4), ∠C2C3C4 = 99.9(4), ∠N1N5C6 = 58.3(1), ∠N1C6N5 = 63.3(1), ∠N1C6C7 = 114.9(6), ∠C6N1C2 = 111.8(1), ∠N5N1C2C3 = 17.3(1), ∠N1C2C3C4 = −26.8(2), θ = C2C3C4/C2N1N5C4 = −26.2(3), φ = N1C6N5/C2N1N5C4 = 74.0(1). Comparison of these and earlier results showed that the NN bond length in the diaziridine ring is very weakly dependent on the cis- or trans-arrangement of substituents at the nitrogen atoms.
Добавил в систему: Хайкин Леонид Соломонович

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Equilibrium molecular structure and spectra of 6-methyl-1,5-diazabicyclo[3.1.0]hexane: joint analysis of gas phase electron diffraction, quantum chemistry, and spectroscopic dataстатья

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