UC Davis

Spiropyrans (SP) are a class of switchable molecules that exhibit two different isomers; (1) SP “closed” isomer and (2) merocyanine (MC) “open” isomer. Their distinct differences in polarity, structure, and color due to their interchanging ability make them a great candidate as a small molecule sensor. Chapter 1 introduces the origins of spiropyrans and a detailed description of the isomerization to merocyanine. The respective UV-Vis electronic transitions are explained as well as the chemical properties of the two isomers. The layout of this dissertation work is thus described. Chapter 2 reviews 102 colorimetric copper(II) sensors from the years 2010-2022 and evaluates common metal ions that offered dual detection or anions that interfered with detection. Copper(II) is an essential metal in the body aiding in various physiological functions and is commonly found in the environment. However, excess copper(II) can result in toxicity both biologically and environmentally. Therefore, a sensor for rapid colorimetric copper(II) detection was synthesized. A dimethylamine-functionalized spiropyran (SP-14) was found to selectively and sensitively detect copper(II) over biologically and environmentally relevant metal ions. UV-Vis spectroscopy and DFT calculations were used to investigate the SP-14‒Cu2+ interaction. Chapter 3 provides a complete 1H and 13C NMR assignments for three GSH-stabilized MC species as well as their respective individual SP configurations. GSH is a redox active molecule present in the human body that acts as a powerful antioxidant. Alterations in GSH levels are indicative of oxidative stress resulting in several pathological conditions. This chapter further explores the stereochemistry between GSH and merocyanine using NOESY NMR to present a most favorable trans conformation. These findings may provide insight in elucidating how SPs interact with other chemical stimuli. Based on the sensitivity and selectively for GSH, two SPs mentioned in the previous chapter, were utilized in Chapter 4 to construct a manganese-based contrast agent for MRI. Upon examining the literature, variance in GSH concentrations between benign and malignant tumors was noticed. This chapter is directed towards developing an MR agent that can observe fluctuations in GSH concentrations in hopes to discern between these two types of tumors. Details into the individual components chosen for the formation of the agent, the synthetic procedure, testing of the r1 relaxation rate and future work will be discussed.