eprintid: 39494
rev_number: 27
userid: 9805
dir: disk0/00/03/94/94
datestamp: 2020-09-16 14:09:41
lastmod: 2020-09-16 14:09:41
status_changed: 2020-09-16 14:09:41
type: thesis_degree
metadata_visibility: show
contact_email: cajohnson0@gmail.com
eprint_status: archive
creators_name: Johnson, Clinton
creators_email: caj52@pitt.edu
creators_id: caj52
creators_orcid: 0000-0002-4141-9495
title: USING ULTRAFAST VIBRATIONAL SPECTROSCOPY FOR A COMPREHENSIVE UNDERSTANDING OF STRUCTURAL AND ROTATIONAL MOTIONS FOR WATER TO PROTIC IONIC LIQUIDS
ispublished: unpub
divisions: sch_as_chemistry
full_text_status: restricted
keywords: hydrogen bonding, ultrafast vibrational spectroscopy, protic ionic liquids, ionic liquids, two-dimensional infrared spectroscopy
abstract: In this work, two-dimensional infrared (2D-IR) spectroscopy investigates the timescale of solvent fluctuations for proton and hydride transfers.  To elucidate hydride transfer dynamics, the BH stretch of \ce{BH4-} is probed in various solvents from \ce{H2O} to ionic liquids (ILs).  For proton transfer dynamics, a vibrational probe (\ce{SCN-}) explores the three-dimensional hydrogen bonding environment of a protic ionic liquid (PIL).    
 
\ce{BH4-} is first investigated in increasing NaOH concentrations to develop a molecular understanding of suppressing the hydrogen evolution reaction.  As the concentration increases, the timescale of frequency fluctuations decrease.  Born Oppenheimer molecular dynamics (BOMD) simulations suggest that a crowding effect of ions around \ce{BH4-} inhibits the rearrangement of dihydrogen bonds between \ce{BH4-} and \ce{H2O}.  To completely suppress the hydrogen evolution reaction, ILs with \ce{BH4-} as the anion are investigated.  The linear and 2D-IR spectra of the antisymmetric BH stretch of \ce{BH4-} are complicated due to Fermi resonances.  The narrow linear and 2D-IR linewidths of \ce{BH4-} in an IL allow a comprehensive assignment of all diagonal peaks and crosspeaks.  Confirmed with a model Hamiltonian, two anharmonicities for the antisymmetric BH stretch of \ce{BH4-} are characterized.     

Polarization- and temperature-dependent 2D-IR is employed to investigate the hydrogen bonding network of the PIL ethyl-ammonium nitrate (EAN).  \ce{SCN-} experiences two hydrogen bonding subensembles in EAN as two separate vibrational relaxation times are resolved.  Furthermore, the polarization-weighted frequency fluctuation correlation function can be separated into two components: structural spectral diffusion (SSD) and reorientation-induced spectral diffusion (RISD).  For \ce{SCN-} in EAN, the timescales of frequency fluctuations are in the rotational limit as the SSD is unresolved.  Temperature-dependent 2D-IR extracts the enthalpy and entropy of activation for frequency fluctuations. For \ce{SCN-} in EAN, the enthalpy of activation for rotational motions are similar as to \ce{SCN-} in \ce{H2O}, and this suggests that the breaking and forming of hydrogen bonds around \ce{SCN-} undergoes a similar mechanism in EAN as in \ce{H2O}.
date: 2020-09-16
date_type: published
pages: 214
institution: University of Pittsburgh
refereed: TRUE
etdcommittee_type: committee_chair
etdcommittee_type: committee_member
etdcommittee_type: committee_member
etdcommittee_type: committee_member
etdcommittee_name: Garrett-Roe, Sean
etdcommittee_name: Waldeck, David H.
etdcommittee_name: Laaser, Jennifer L.
etdcommittee_name: Lambrecht, Daniel S.
etdcommittee_email: sgr@pitt.edu
etdcommittee_email: dave@pitt.edu
etdcommittee_email: j.laaser@pitt.edu
etdcommittee_email: dlambrecht@fgcu.edu
etdcommittee_id: sgr
etdcommittee_orcid: 0000-0001-6199-8773
etdcommittee_orcid: 0000-0003-2982-0929
etdcommittee_orcid: 0000-0002-0551-9659
etdcommittee_orcid: 0000-0001-5326-0234
etd_defense_date: 2020-07-07
etd_approval_date: 2020-09-16
etd_submission_date: 2020-07-31
etd_release_date: 2020-09-16
etd_access_restriction: 1_year
etd_patent_pending: FALSE
thesis_type: dissertation
degree: PhD
citation:   Johnson, Clinton  (2020) USING ULTRAFAST VIBRATIONAL SPECTROSCOPY FOR A COMPREHENSIVE UNDERSTANDING OF STRUCTURAL AND ROTATIONAL MOTIONS FOR WATER TO PROTIC IONIC LIQUIDS.  Doctoral Dissertation, University of Pittsburgh.    (Unpublished)  
document_url: http://d-scholarship-dev.library.pitt.edu/39494/19/Johnson%20Final%20ETD.pdf