Intramolecular Proton Transfer in the Hydrogen Oxalate Anion and the Cooperativity Effects of the Low-Frequency Vibrations: A Driven Molecular Dynamics Study

Dalton Boutwell, Kennesaw State University
Dominick Pierre-Jacques, Kennesaw State University
Olivia Cochran, Kennesaw State University
Jason Dyke, Kennesaw State University
Dayana Salazar, Kennesaw State University
Ciara Tyler, Kennesaw State University
Martina Kaledin, Kennesaw State University


We report first-principles molecular dynamics (MD) and dipole-driven molecular dynamics (μ-DMD) simulations of the hydrogen oxalate anion at the MP2/aug-cc-pVDZ level of theory. We examine the role of vibrational coupling between the OH stretching bands, that is, the fundamental and a few combination bands spanning the 2900-3100 cm-1 range, and several of the low-frequency bending and stretching fundamental modes. The low-frequency modes between 300 and 825 cm-1 play a crucial role in the proton-transfer motion. Strong involvement of CO2 and CCO bending and the CC stretching vibrations indicate that these large amplitude motions cause the shortening of the O···O distance and thus promote H+ transfer to the other oxygen by bringing it over the 3.4 kcal/mol barrier. Analysis of resonant μ-DMD trajectories shows that the complex spectral feature near 825 cm-1, closely corresponding to both an overtone of two quanta of 425 cm-1 and a combination band of low-frequency CO2 rocking (300 cm-1) and CCO bending (575 cm-1) modes, is involved in the proton transfer. μ-DMD shows that exciting the system at these mode combinations leads to faster barrier activation than exciting at the OH fundamental mode.