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Synthesis and Spectroscopic Investigation of Sensitized Near-Infrared Emission of Yb3+ Complexes
No full textLanthanide complexes possess unique photophysical properties such as sharp emission lines, large Stokes shifts, long luminescence lifetimes, and excellent photostability, making them ideal for applications in bioimaging, light-emitting devices, and telecommunications. Their ability to emit in the near-infrared (NIR) region (700–1700 nm) offers key advantages for medical and technological uses, including deep tissue penetration, minimal autofluorescence, reduced light scattering, high signal-to-noise ratios, and low toxicity. This study reports the synthesis and photophysical characterization of Yb3+ complexes across two similar projects. First, a porphyrin-based complex, [Yb(DPP)(PH)(OAc)(MeOH)], incorporating a phenylhexanone (PH) substituent, was synthesized and characterized using ¹H NMR, MS, FTIR, and UV-Vis spectroscopy. The complex exhibited visible absorption at 411 nm (Soret band) and weaker Q bands at 500 and 542 nm. Weak porphyrin fluorescence was observed at 635 and 700 nm, alongside near-infrared (NIR) emissions at 975 and 1006 nm corresponding to Yb3+ 2F5/2 → 2F7/2 transitions. The characterization data reveal that the complex possesses a highly asymmetrical coordination environment, which facilitates enhanced radiative transitions and indicates efficient energy transfer from the coordinated ligands to the Yb3+ ion. In a second study, BODIPY-functionalized ligands (L1–L4) were spectroscopically titrated with [Yb(DPP)(OAc)(MeOH)2] and [Yb(Hfac)3(H2O)2] to probe energy transfer and NIR emission behavior. Ligands L1 (Phen-BDP) and L2 (BiPy-BDP) sensitized Yb3+ emission efficiently in both complexes via the heavy atom effect, while L3 (PA-BDP) and L4 (UR-BDP) showed selective energy transfer only in [Yb-DPP-OAc-L], mediated by a stepwise FRET process. Based on these findings, four BODIPY-Yb3+ complexes were synthesized, each showing visible absorption (503–506 nm) and characteristic NIR emission around 980 nm, with peak splitting due to crystal field interactions
Identification of New Fluorescein-Based Chemical Tools for Studying Human Carboxylesterase 1 (CES1)
No full textThis thesis focuses on the significance of subcellular location-specific activity of hydrolases, exploring their implications for drug-drug interactions (DDIs) and sequence polymorphisms in drug metabolism. Hydrolases exhibit distinct distribution patterns across various tissues and organs, playing pivotal roles in local metabolic processes. These enzymes possess a wide substrate scope, efficiently breaking down various functional groups found in biological molecules through the mechanism of hydrolysis.
Here, I explore the development and characterization of fluorogenic chemical tools tailored for investigating human carboxylesterase 1 (CES1) activity in live cells. CES1 plays an essential role in the hydrolysis of many pharmaceuticals, impacting drug metabolism and therapeutic efficacy. Despite the significance of CESs, limited techniques are used for studying their activity in live cells. My initial studies focused on the development of two fluorogenic compounds based on 3-O-methylfluorescein. My efforts determined that one of these compounds, MCP-Et, is non-toxic and specific for CES1 over CES2 in live cells. Harnessing this specificity I utilized MCP-Et to study CES1-mediated DDIs.
I next studied a library of fluorogenic acylmethoxy ether (AM)-esters. Upon in vitro screening of the library, multiple AM-esters showed specificity towards CES1. Compounds that showed strong fluorescence with CES1, but minimal activity with CES2 were prioritized for further analysis as selective chemical tools for CES1. The fluorescein-based fluorogenic chemical tools developed in this thesis will provide researchers with valuable tools to study CES1 activity in live cells, enhancing our understanding of its role in drug metabolism, resulting in better outcomes for patients treated with CES1-metabolized drugs
Anne Flaherty and Don Holly
No full texthttps://thekeep.eiu.edu/authors_at_eiu_april_8_2025/1005/thumbnail.jp
