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Molecules 2018, 23(4), 906; https://doi.org/10.3390/molecules23040906

Complexes of CO2 with the Azoles: Tetrel Bonds, Hydrogen Bonds and Other Secondary Interactions

1
Department of Chemistry, Youngstown State University, Youngstown, OH 44555, USA
2
Instituto de Química Médica (IQM-CSIC), Juan de la Cierva, 3, E-28006 Madrid, Spain
*
Authors to whom correspondence should be addressed.
Academic Editor: Steve Scheiner
Received: 31 March 2018 / Revised: 9 April 2018 / Accepted: 11 April 2018 / Published: 14 April 2018
(This article belongs to the Special Issue Tetrel Bonds)
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Abstract

Ab initio MP2/aug’-cc-pVTZ calculations have been performed to investigate the complexes of CO2 with the azoles pyrrole, pyrazole, imidazole, 1,2,3- and 1,2,4-triazole, tetrazole and pentazole. Three types of complexes have been found on the CO2:azole potential surfaces. These include ten complexes stabilized by tetrel bonds that have the azole molecule in the symmetry plane of the complex; seven tetrel-bonded complexes in which the CO2 molecule is perpendicular to the symmetry plane; and four hydrogen-bonded complexes. Eight of the planar complexes are stabilized by Nx···C tetrel bonds and by a secondary interaction involving an adjacent Ny-H bond and an O atom of CO2. The seven perpendicular CO2:azole complexes form between CO2 and two adjacent N atoms of the ring, both of which are electron-pair donors. In three of the four hydrogen-bonded complexes, the proton-donor Nz-H bond of the ring is bonded to two C-H bonds, thereby precluding the planar and perpendicular complexes. The fourth hydrogen-bonded complex forms with the strongest acid pentazole. Binding energies, charge-transfer energies and changes in CO2 stretching and bending frequencies upon complex formation provide consistent descriptions of these complexes. Coupling constants across tetrel bonds are negligibly small, but 2hJ(Ny-C) across Nz-H···C hydrogen bonds are larger and increase as the number of N atoms in the ring increases. View Full-Text
Keywords: tetrel bond; hydrogen bond; carbon dioxide; azoles; IR spectra; spin-spin coupling constants tetrel bond; hydrogen bond; carbon dioxide; azoles; IR spectra; spin-spin coupling constants
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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Del Bene, J.E.; Elguero, J.; Alkorta, I. Complexes of CO2 with the Azoles: Tetrel Bonds, Hydrogen Bonds and Other Secondary Interactions. Molecules 2018, 23, 906.

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