Tuning of Non-Covalent Interactions in Molecular Complexes of Fluorinated Aromatic Compounds
Abstract
The rotational spectra of pentafluoropyridine-water and hexafluorobenzene-water have shown unambiguously that substitution by fluorine atoms on the ring strongly influences the binding abilities of the aromatic ligand. Differently from their non-substituted counterparts, which form hydrogen bonds with water, both molecules interact with water forming a lone-pair-π-hole interaction between the water oxygen and the ring. We report on a series of rotational spectroscopy studies performed with a Molecular Beam Fourier Transform Microwave spectrometer in which we have tested the binding abilities of a series of fluorine substituted pyridines, namely 2,4-fluoropyridine, 3,5-fluoropyridine and 2,4,6-fluoropyridine with water. In the complexes formed by the di-substituted pyridines, the water moiety lies in the aromatic plane and forms a hydrogen bond with the heterocyclic nitrogen atom and this is by far the most stable conformation. In the tri-substituted pyridine-water complexes two isomers are possible, but the lp-π-hole form is the one observed in the rotational spectrum. More studies involving the pentafluoropyridine and hexafluorobenzene molecules and several ligands such as NH_3 and CO have also been performed and the interaction with the π-hole has been characterized.
Camilla Calabrese, Qian Gou, Assimo Maris, Walther Caminati, Sonia Melandri, Probing the Lone Pair-π-Hole Interaction in Perfluorinated Heteroaromatic Rings: The Rotational Spectrum of Pentafluoropyridine-Water, J. Phys. Chem. Lett. 2016, 7, 1513-1517 http://dx.doi.org/10.1021/acs.jpclett.6b00473 Luca Evangelisti, Kai Brendel, Heinrich Maeder, Walther Caminati, and Sonia Melandri, Rotational Spectroscopy Probes Water Flipping by Full Fluorination of Benzene, Angew. Chem. Int. Ed. 2017, 56, 13699 -13703 https://doi.org/10.1002/anie.201707155- Publication:
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73rd International Symposium on Molecular Spectroscopy
- Pub Date:
- June 2018
- DOI:
- 10.15278/isms.2018.WK08
- Bibcode:
- 2018isms.confEWK08M
- Keywords:
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- Structure determination