Hydrogen Bond Symmetrization in Glycinium Oxalate under Pressure

TL;DR

This study demonstrates hydrogen bond symmetrization in glycinium oxalate at moderate pressures using spectroscopic and computational methods, revealing pressure-induced structural reorganization and proton dynamics in the complex.

Contribution

First evidence of hydrogen bond symmetrization in glycinium oxalate under pressure combining experimental spectroscopy and first-principles simulations.

Findings

Hydrogen bond symmetrization occurs at 8 GPa.

Protonation leads to infinite oxalate chains.

Glycine units reorient above 12 GPa to form supramolecular assemblies.

Abstract

We report here the evidences of hydrogen bond symmetrization in the simplest amino acid- carboxylic acid complex, glycinium oxalate, at moderate pressures of 8 GPa using in-situ infrared and Raman spectroscopic investigations combined with first-principles simulations. The protonation of the semioxalate units through dynamic proton movement results in infinite oxalate chains. At pressures above 12 GPa, the glycine units systematically reorient with pressure to form hydrogen bonded supramolecular assemblies held together by these chains.