A reduced electrophilicity for simple Lewis acids A involved in non-covalent interactions with Lewis bases B†

Dissociation energies D for B⋯A = B + A can be written D = c′NE, where N and E are the nucleophilicities and electrophilicities of the Lewis base B and the Lewis acid A, respectively. A reduced electrophilicity is defined Ξ = E/σ, where σ is the maximum electrostatic surface potential on iso-surface of A, the atom directly involved in the non-covalent interaction. This definition is tested for halogen-bonded complexes B⋯YX, with Lewis bases B = N, CO, CH, CH, HS, HCN HO or NH. D plotted against N for several series B⋯YX yields straight lines of gradient E. When D/σ is the ordinate, the straight lines conflate to a single line, gradient Ξ = E/σ. Hydrogen-bonded complexes B⋯HX (X = F, Cl, Br, I), coinage-metal complexes B⋯MX (M = Cu, Ag, Au; X = F, Cl, Br, I), and alkali-metal bonded complexes B⋯MX (M = Li, Na: X = F, H, CH) behave similarly. Ξ is an intrinsic property of the atom immediately involved in the non-covalent bond.ACL thanks the University of Bristol for the award of a Uni- versity Senior Research Fellowship. IA thanks the Ministerio de Ciencia e Innovacio ́n of Spain (PGC2018-094644-B-C22 and 5931125495-125495-4-21) and Comunidad de Madrid (P2018/ EMT-4329 AIRTEC-CM) for financial support