Characterizing the Vibrational Spectra of Hydrogen Bonded Systems with Molecular Dynamics Simulations and Quantum Chemical Methods

Author

Dalton Boutwell, Kennesaw State UniversityFollow

Date of Award

Summer 6-15-2021

Track

Chemistry

Degree Type

Thesis

Degree Name

Master of Science in Chemical Sciences (MSCB)

Department

Chemistry

Committee Chair/First Advisor

Martina Kaledin

Committee Member

Mark Mitchell

Committee Member

Michael Stollenz

Abstract

We apply and assess the utility of DMD for the purpose of investigating complex spectral features in N₂H⁺···OC, N₂D⁺···OC, C₂O₄H^-, C₂O₄D^- and (HCOOH)₂. The proton transfer as a vibrational motion consists of diffuse qualities that can be accounted for with classical and quantum chemical analyses. Classical approaches yield a wealth of information about vibrational spectra at a reduced cost, as in the case of previously investigated N₄H⁺. The isoelectronic N₂H⁺···OC has a smaller dipole moment than N₄H⁺ and a calculated DMD parallel H⁺ transfer frequency of 1800 cm^-1, disagreeing with the VCI (1541 cm^-1) and VPT2 (1620 cm^-1) values. However, the perpendicular H⁺ bending mode is evaluated at 910 cm^-1, in good agreement with VCI (954 cm^-1). Combination bands were recovered at 980 and 1980 cm^-1, with weaker absorptions featured at 450 and 380 cm^-1. In C₂O₄H^-, the O-H stretch DMD value was in good agreement with the experiment. The brightest experimental peak in the O-H stretching region was ω_max= 2945 cm^-1, while the DMD value for the motion was ν₁ = 3000 cm^-1. C₂O₄H^- combination bands were characterized at 800-850, 1505, and 1450 cm^-1 were assigned using the analysis of the atomic motion along the trajectory. Rudimentary explicit solvation effects were explored for C₂O₄H^- and Coupled Cluster PES scans were performed to support all results. A combination band of O-H and C-H in-plane bending was found in the H⁺ transfer region for (HCOOH)₂ using the 2D-IR DMD procedure.