Chiral Transition Metal Complexes under Resonance: Mechanism of a New Form of Chiral Raman Spectroscopy

• Author / Creator

  Li, Guojie

• My PhD thesis primarily focuses on exploring chiroptical events and signatures of chiral transition metal complexes when they are under (near) resonance conditions. To achieve this goal, multiple chiroptical spectroscopic techniques were utilized, aided by theoretical calculations. These chiroptical techniques include Raman optical activity (ROA), vibrational circular dichroism (VCD), electronic circular dichroism (ECD), and a new form of chiral Raman spectroscopy which was discovered during the thesis research. We named this new form ‘eCP-Raman’ which is a combination of ECD (abbreviated as ‘e’ in the name) and circularly polarized Raman (CP-Raman) spectroscopy. The thesis encompasses the long discovery journey of uncovering the mechanism responsible for the large, induced chiral Raman signatures of solvents when the associated chiral solute is under resonance. The development of the eCP-Raman mechanism leads to the realization that resonance ROA (RROA) spectra measured in the present thesis work and in previous reports by others are (severely) contaminated by eCP-Raman contributions.
  More specifically, Chapter 3 describes the observation of the strong, induced chiral Raman response of achiral solvent molecules when a chiral transition metal complex solute is under resonance condition and the eventual discovery of the eCP-Raman mechanism responsible for it. In Chapter 4, we examined the chiral Raman responses of three different chiral solutes under resonance and concluded that eCP-Raman contributes dominantly in all three cases, whereas RROA contributes negligibly. Importantly, the observed chiral Raman signatures of the solutes were correctly simulated by the proposed eCP-Raman mechanism. Chapter 5 describes the chiroptical characterization of two new chiral transition metal complexes, which are (near) resonance with the laser wavelength of the ROA spectrometer used. In chapter 6, an approach to extract the true RROA spectrum of a chiral complex under resonance, based on the eCP-Raman mechanism, was proposed and applied. The comparison between the true RROA spectrum extracted and the preliminary simulation results, based on the latest theoretical RROA development, provides guidance for future development in this important direction.

• Subjects / Keywords

  • Chemistry
  • Spectroscopy

• Graduation date

  Fall 2023

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/r3-pntr-bv14

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.