title: Nature of the attractive interaction between proton acceptors and organic ring systems.
abstract: Systematic ab initio calculations are combined with a deconvolution of electrostatic contributions to analyze the interplay between potential hydrogen bond acceptors and organic rings with C(sp(2))-H groups (benzene, pyridine and cyclopentadiene). A distinct anisotropic interaction between the ring systems and the electron lone pairs of cyanide, water and other acceptor species is revealed that favors the in-plane orientation of the proton acceptor group. In the attractive regime this interaction carries a pronounced electrostatic signature. By decomposing the electrostatic contribution into parts attributed to different subunits of the ring systems we demonstrate that a major proportion of the interaction energy gain is originating from the non-adjacent moieties, that are not in close contact with. This behavior holds equally for homocyclic, heterocyclic and non-aromatic rings but contrasts that of the ethyne molecule, taken as reference for a weak hydrogen bond donor clearly exhibiting the expected localized character. The ring interaction requires the presence of π-electron clouds and typically results in an interaction energy gain of 40 to 80 meV. Our findings suggest the proton acceptor-ring interaction as a new category of intermolecular non-covalent interactions.
authors.affiliation: Physik Department, Technische Universität München, Garching, Germany.
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Arras
authors.forename: Ari Paavo
authors.initials: AP
authors.lastname: Seitsonen
authors.forename: Florian
authors.initials: F
authors.lastname: Klappenberger
authors.forename: Johannes V
authors.initials: JV
authors.lastname: Barth
mesh_terms: D003198:Computer Simulation; D006859:Hydrogen / Q000737:chemistry*; D006860:Hydrogen Bonding; D008956:Models, Chemical; D009930:Organic Chemicals / Q000737:chemistry*; D011522:Protons; D013816:Thermodynamics
chemical_list: D009930:Organic Chemicals; D011522:Protons; D006859:Hydrogen