title: Σ-holes, π-holes and electrostatically-driven interactions.
abstract: A positive π-hole is a region of positive electrostatic potential that is perpendicular to a portion of a molecular framework. It is the counterpart of a σ-hole, which is along the extension of a covalent bond to an atom. Both σ-holes and π-holes become more positive (a) in going from the lighter to the heavier atoms in a given Group of the periodic table, and (b) as the remainder of the molecule is more electron-withdrawing. Positive σ- and π-holes can interact in a highly directional manner with negative sites, e.g., the lone pairs of Lewis bases. In this work, the complexes of 13 π-hole-containing molecules with the nitrogen lone pairs of HCN and NH(3) have been characterized computationally using the MP2, M06-2X and B3PW91 procedures. While the electrostatic interaction is a major driving force in π-hole bonding, a gradation is found from weakly noncovalent to considerably stronger with possible indications of some degree of coordinate covalency.
authors.affiliation: CleveTheoComp, 1951 W, 59th Street Suite 409, Cleveland, OH 44113, USA. jsmurray@uno.edu
authors.forename: Jane S
authors.initials: JS
authors.lastname: Murray
authors.forename: Pat
authors.initials: P
authors.lastname: Lane
authors.forename: Timothy
authors.initials: T
authors.lastname: Clark
authors.forename: Kevin E
authors.initials: KE
authors.lastname: Riley
authors.forename: Peter
authors.initials: P
authors.lastname: Politzer
mesh_terms: D003198:Computer Simulation; D008958:Models, Molecular; D055672:Static Electricity