2026-05-05T19:51:47Zhttps://uvadoc.uva.es/oai/request

oai:uvadoc.uva.es:10324/489982022-07-18T09:32:59Zcom_10324_1186com_10324_931com_10324_894col_10324_1404

00925njm 22002777a 4500 dc López Alonso, Juan Carlos author Macario Farto, Alberto author Maris, Assimo author Alkorta, Ibon author Blanco Rodríguez, Susana author 2021 The rotational spectrum of the weakly bound complex pentafluoropyridineꞏꞏꞏformaldehyde has been investigated using Fourier transform microwave spectroscopy. From the analysis of the rotational parameters of the parent species and of the 13C and 15N isotopologues, the structural arrangement of the adduct has been unambiguously established. The full ring fluorination of pyridine has a dramatic effect on its binding properties: It alters the electron density distribution at the π-cloud of pyridine creating a π-hole and changing its electron donor-acceptor capabilities. In the complex, formaldehyde lies above the aromatic ring with one of the oxygen lone pairs, as conventionally envisaged, pointing toward its centre. This lone pairꞏꞏꞏπ-hole interaction, reinforced by a weak C-HꞏꞏꞏN interaction, indicates an exchange of the electron-acceptor roles of both molecules when compared to the pyridineꞏꞏꞏformaldehyde adduct. Tunnelling doublets due to the internal rotation of formaldehyde have also been observed and analysed leading to a discussion on the competition between lone pairꞏꞏꞏπ-hole and π ꞏꞏꞏπ staking interactions. Chemistry – A European Journal, 2021, vol. 27, n. 55, p.13870 –13878 0947-6539 https://uvadoc.uva.es/handle/10324/48998 10.1002/chem.202102163 13870 55 13878 Chemistry – A European Journal 27 1521-3765 How aromatic fluorination exchanges the interaction role of pyridine with carbonyl compounds: The formaldehyde adduct