Correspondence between the one-electron potential and the Laplacian of the electron density as indicators of proton affinity

Proton affinities for a series of alkyl amines and phosphines formed from successive alkylation of NH3 and PH3 are known to exhibit linear correlation with (3,3) critical points of N and P in the distribution of the Laplacian of the electron density, del(2)rho. We show that these proton affinities also exhibit linear correlation with valence minima of N and P in the distribution of the one-electron potential (OEP), del(2)root rho(r)/root rho(r). These results provide evidence of the correspondence between OEP and del(2)rho as quantitative indicators of proton affinity. (C) 1999 Elsevier Science B.V. All rights reserved.