Lone‐Pair⋅⋅⋅π Interaction: A Rotational Study of the Chlorotrifluoroethylene–Water Adduct

Probing the Lone Pair···π-Hole Interaction in Perfluorinated Heteroaromatic Rings: The Rotational Spectrum of Pentafluoropyridine·Water

“…Still the fact that a barrier exists (differently, for example, from the CF 4 •water complex where water undergoes a free internal rotation) 29 shows that a feeble interaction of the hydrogen atom with the nitrogen atom is present. lp•••π-hole interactions, similar to the one detected in this work, were directly observed only in a few other complexes containing a fully halogenated alkene (CFClCF 2 •water 30 and CFClCF 2 •ammonia 31 ). In both cases the leading attraction is between the oxygen/nitrogen lp and the carbon attached to the two fluorine atoms, with the oxygen/nitrogen atom displaced toward them.…”

“…Thus, we can assert that the lp•••π-hole interaction is weaker than the O−H•••N bond typical of aromatic heterocycles but stronger than the possible same hydrogen bond in perfluorinated analogs. As regards lp•••π-hole bound complexes, it can be noted that the binding energy in CFCl CF 2 •water 30 is almost half with respect to 5FPY•W-π.…”

Rotational Characterization of an n → π* Interaction in a Pyridine–Formaldehyde Adduct

“…17,18 The n → π* interactions between water and the carbonyl group have been shown also to cooperate with moderate and weak HBs to stabilize the microsolvated adducts of β-propiolactone. 19 Complexes stabilized by the so-called lone pair•••π-hole interaction between water or ammonia with fully halogenated alkenes 20,21 or aromatic compounds 22 have also been detected by rotational spectroscopy. Theoretical and experimental studies of charge transfer n → π*, σ → π*, and π → π* complexes have been described by Weinhold and Landis.…”

Halogen–Halogen Links and Internal Dynamics in Adducts of Freons

“…Their C–H groups could indeed act as proton donors, a property enhanced by the electron withdrawing of the halogen atoms, and interact with the electron-rich regions of the partner molecules. , In addition, in adducts or oligomers of CFCs containing hydrogen, the monomer units are held together by networks of WHBs. − When CFCs do not contain hydrogen, the positive electrostatic region (“σ-hole”) , can interact electrostatically with negative sites of another or of the same molecular entity, giving rise, according to IUPAC, to the so-called halogen bond (HaB) . However, it has been observed that when a CFC does not contain hydrogen and has a π electron system, a lone pair···π interaction (Bürgi–Dunitz) is favored …”