Complementary nature of hydrogen bond basicity and acidity scales from electrostatic and atoms in molecules properties

DFT calculations over 120 hydrogen bond bases/acids and their complexes with hydrogen fluoride/hydrogen cyanide have been performed. By using properties computed at the B3LYP/6-31+G(d,p) level of theory as predictors of ∑βH2/∑αH2 in multivariate analysis, the overall hydrogen bond scale can be regarded as a composite descriptor made of an electrostatic term (by using minimum/maximum electrostatic potential values on the 0.001 au isodensity contour surface of the isolated base/acid) and of an overlap term (by using energy density values calculated at the bond critical point of 1∶1 HF/NCH complexes). These models underline the complementarity between the two overall hydrogen bond scales, and, for the first time, make accurate predictions for multi-functional bases/acids.