Computational Study on the Conformational Preferences of Neutral, Protonated and Deprotonated Glycine Dimers

A conformational analysis has been carried out for monoprotonated, unprotonated and deprotonated glycine dimers in the gas phase an aqueous solution. MP2/6-311++(d,p), B3LYP/6-311++(d,p) M06/6-311++(d,p) optimizations were performed more than 200 initial conformations comprising nonionic (COOH–CH2–NH2) (N) zwitterionic (COO−–CH2–NH3+) (Z) structures neutral monomers. All methods indicate that Z monomers are preferred over N ones solutions, whereas reverse trend is observed (including also protonated dimers). NC ZC coexist solutions dimer. The geometries significantly different depending on media total dimer charge. Moreover, several minima display close energies each series (media charge). New conformers, not previously reported, found to be populated those mixtures. Dimers containing associated with larger absolute solvation prone N-containing experience protonation deprotonation phase, Quantum Theory of Atoms Molecules (QTAIM) reveals uncharged trifling electron density transfer between monomers, it significant anionic cationic dimers.