The Electrophilicities of XCF ₃ and XCl (X=H, Cl, Br, I) and the Propensity of These Molecules To Form Hydrogen and Halogen Bonds with Lewis Bases: An <i>Ab Initio</i> Study

Equilibrium dissociation energies, De, of four series halogen- and hydrogen-bonded complexes B⋅⋅⋅XCF3 (X=H, Cl, Br I) are calculated ab initio at the CCSD(T)(F12c)/cc-pVDZ-F12 level. The Lewis bases B involved N2, CO, PH3, C2H2, C2H4, H2S, HCN, H2O NH3. Plots De versus NB, where NB nucleophilicities assigned to previously, good straight lines through origin, as those for corresponding set B⋅⋅⋅XCl. gradients plots define electrophilicities EXCF3 EXCl various acids. determined values are: EXCF3=2.58(22), 1.40(9), 2.15(2) 3.04(9) X=H, I, respectively, EXCl=4.48(22), 2.31(9), 4.37(27) 6.06(37) same order X. Thus, it is found that, a given X, ratio EXCl/ 2 within assessed errors, therefore appears be independent atom X type non-covalent interaction (hydrogen bond or different varieties halogen bond) in which involved. Consideration molecular electrostatic surface potentials shows that maximum positive potential σmax (the most electrophilic region XCF3 XCl, lies on symmetry axes these molecules, near X) strongly correlated.