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Scholarly Works (3 results)

  • Thesis
  • Peer Reviewed
UC Davis Electronic Theses and Dissertations (2023)

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.

    Cover page: The Progression of Spiropyran as a Chemical Sensor to an Activatable Contrast Agent for MRI
    • Article
    • Peer Reviewed
    UC Davis Previously Published Works (2023)
    Small molecules can display certain electronic and structural features that enable their use for metal-sensing applications in different fields. Of the reported metal sensors, there has been increasing interest in copper sensing in the past decade, given the biological importance of copper as well as its presence as a potential contaminant in water and fuels. Molecules used for copper(II) sensing generally consist of a fluorophore/chromophore and a ligand for selective metal ion recognition. This review article focuses on literature contributions since the year 2010 concerning small molecule copper(II) sensors that provide a naked-eye color response in solution. We present molecular structural features and sensing mechanisms for the colorimetric and fluorometric detection of copper(II) ions in different environmental, agricultural, and biological samples. In addition, the sensing performance of these chemosensors is compared and discussed, which could aid in the future design of chemosensors for copper(II). Finally, we outline the challenges and future prospects of fluorophore/chromophore–ligand chemistry in applications of small molecules for fluorometric and colorimetric assays of copper(II).
      Cover page: Small molecule sensors for the colorimetric detection of Copper(II): A review of the literature from 2010 to 2022Creative Commons 'BY-NC-ND' version 4.0 license
      • Article
      • Peer Reviewed
      UC Davis Previously Published Works (2021)
      The metal-binding capabilities of the spiropyran family of molecular switches have been explored for several purposes from sensing to optical circuits. Metal-selective sensing has been of great interest for applications ranging from environmental assays to industrial quality control, but sensitive metal detection for field-based assays has been elusive. In this work, we demonstrate colorimetric copper sensing at low micromolar levels. Dimethylamine-functionalized spiropyran (SP1) was synthesized and its metal-sensing properties were investigated using UV-vis spectrophotometry. The formation of a metal complex between SP1 and Cu2+ was associated with a color change that can be observed by the naked eye as low as ≈6 μM and the limit of detection was found to be 0.11 μM via UV-vis spectrometry. Colorimetric data showed linearity of response in a physiologically relevant range (0-20 μM Cu2+) with high selectivity for Cu2+ ions over biologically and environmentally relevant metals such as Na+, K+, Mn2+, Ca2+, Zn2+, Co2+, Mg2+, Ni2+, Fe3+, Cd2+, and Pb2+. Since the color change accompanying SP1-Cu2+ complex formation could be detected at low micromolar concentrations, SP1 could be viable for field testing of trace Cu2+ ions.
        Cover page: Highly Sensitive and Selective Spiropyran-Based Sensor for Copper(II) Quantification
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