Doctor of Philosophy (Ph.D.), Bowling Green State University, 2023, Photochemical Sciences

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 m (open full item for complete abstract)

Committee: Alexander Tarnovsky Ph.D. (Committee Chair); Yuning Fu Ph.D. (Other); John Cable Ph.D. (Committee Member); Peter Lu Ph.D. (Committee Member) Subjects: Chemistry; Physical Chemistry

Doctor of Philosophy, University of Akron, 2018, Integrated Bioscience

Application of photophysical mechanisms, such as photoinduced electron transfer (ESIPT) and aggregate induced emission (AIE), have been used to gain valuable information in biological systems. Fluorophores are commonly capable of displaying more than one photophysical property and it can be difficult to distinguish between them. In chapter II a set of aluminum sensors were reported previously as AIE materials were further investigated for their potential to display ESIPT over AIE. Low temperature fluorescence was utilized to distinguish between their emissive tautomers, which allowed for differentiation between AIE and ESIPT emission. ESIPT was determined to be the primary source of emission. The development of a large variety of fluorescent materials that can selectively bind to zinc over other competitive metals such as cadmium has been heavily sought after for the last three decades. 2-(2'-Hydroxyphenyl)benzoxazole (HBO) can chelate Zn2+ and readily undergo ESIPT to display large Stokes shifts in excess of 100 nm. Large Stokes shifts can provide sensors with high resolution. Additionally, the formed zinc complex can selectively interact with pyrophosphate (PPi) over other phosphate molecules. Chapter III discusses a newly synthesized HBO-based material that displays good selectivity for zinc and reactivity with PPi over ATP and ADP. Chapters IV-VI presents several different synthesized flavonoids that have been successfully applied to a variety of different biological applications such as molecular probes and a non-specific contrast imaging stain for live muscle imaging, which has never been reported before. Additionally, investigation into how proteins, HSA and BSA, interact with several different flavonoids was performed in order to elucidate structural information about the flavonoid-protein complex. Chapter VII presents a developmental study of the zebrafish lateral line for 96 hpf and younger embryos using a newly synthesize (open full item for complete abstract)

Committee: Yi Pang (Advisor); Wiley Youngs (Committee Member); Leah Shriver (Committee Member); Christopher Ziegler (Committee Member); Richard Londraville (Committee Member) Subjects: Biology; Chemistry