Photochemical Sciences Ph.D. Dissertations
Ultrafast Excited State Relaxation Dynamics in Molecular Probes and Organic Molecules of Biological Importance
Date of Award
2023
Document Type
Dissertation
Degree Name
Doctor of Philosophy (Ph.D.)
Department
Photochemical Sciences
First Advisor
Alexander Tarnovsky (Committee Chair)
Second Advisor
Yuning Fu (Other)
Third Advisor
John Cable (Committee Member)
Fourth Advisor
Peter Lu (Committee Member)
Abstract
The very initial photoprocesses of relevant chromophores and organic molecular probes can provide important mechanistic insight into designing more robust and useful compounds for targeting in vivo applications, drug delivery, as well as an overall understanding of significant biological functions. Therefore, examining and comprehending these ultrafast processes is critical. In this dissertation, the elucidation of excited state dynamics of several molecular probes and organic systems is obtained from the results of multiple femtosecond transient absorption experiments. Chapters I and II detail the theoretical and experimental aspects, respectively, of this dissertation as fundamental and practical methods are addressed. The first chapter will cover laser spectroscopy and associated theories surrounding the technique relevant to the work discussed herein in general, while the second chapter will discuss specifics of experimental design and practices used for data analysis. The third chapter focuses on a photochromic system, trans-4,4’-azopyridine, capable of undergoing trans-cis isomerization upon irradiation and how similar and different this compound’s dynamics are compared to trans-azobenzene and other azo dyes in general. An unusual trend in the quantum yield increasing upon exciting with higher excitation photon energies is linked to vibrational coherence observed for an in-plane bending mode. Chapter IV delves into a project on two polymethine cyanine dyes, which are utilized for deep tissue imaging due to their absorption and emission in the shortwave infrared region. The excited state dynamics in the fluorescent state and non-radiative relaxation mechanisms in this state, discovered to be competing photoisomerization and the energy gap law relaxation pathways, are analyzed and discussed. Finally, Chapter V describes work on a series of enaminones where the question of if and how excited state intramolecular proton transfer plays a role in the excited state mechanism of these organic systems. Different solvents were analyzed to test the hypothesis that preferential orientation of the proton transfer would be influenced by the degree of solvent polarity.
Recommended Citation
Obloy, Laura Marie, "Ultrafast Excited State Relaxation Dynamics in Molecular Probes and Organic Molecules of Biological Importance" (2023). Photochemical Sciences Ph.D. Dissertations. 150.
https://scholarworks.bgsu.edu/photo_chem_diss/150