Structure and Magnetic Properties of Glycine Radical in Aqueous Solution at Different pH Values

Abstract

A recently developed quantum mechanical approach devoted to the study of unstable species in solution was applied to the radicals resulting from the homolytic breaking of the Cα−Hα bond of glycine in aqueous solution at different pH values.The computational protocol includes density functional calculations, simulation of the solvent by a mixed discrete-continuum approach, and averaging of spectroscopic properties over the most important vibrational motions. In vacuo computations provide reliable results for the zwitterionic form when using hybrid Hartree−Fock/density-functional methods with purposely tailored basis sets. Under the same conditions, disappointing results are obtained for the magnetic properties of neutral and, especially, anionic forms. Although the modifications of the structure and the magnetic properties of these species induced by the solvent are well reproduced by either a continuum model or a supermolecule approach, quantitative results can be obtained only by a mixed discrete-continu...