Changes of electron density in the OHN hydrogen bond upon proton transfer in complexes of phenols with trimethylamine: DFT study

The intermolecular hydrogen bonds in phenol-trimethylamine complexes were investigated by Bader Atom in Molecules (AIM) theory. The AIM parameters of the bond critical points (BCPs) of the O center dot center dot center dot H, N center dot center dot center dot H, and CO bonds as well as those of the phenol ring critical point (RCP) were analyzed as functions of the proton-transfer degree. Transfer of the proton from donor to acceptor changes not only the electron density of the hydrogen bridge, but also the electron cloud in the proton donor. The differences between the proton donors in relation to their pK(a) values are seen in the systematic changes of the AIM parameters. Copyright (C) 2008 John Wiley & Sons, Ltd.