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    The Structural and Electrochemical Effects of Varying the Group 1 Counterion in Fluorinated Alkoxide Lanthanide Complexes
    (Wheaton College. (Norton, Mass.), 2023-05-15) Slaney, Cassandra
    In this work, five new lanthanide complexes with varying counterions and coordination by fluorinated alkoxide ligands were synthesized and characterized via single crystal X-ray diffractometry, including [K(THF) 2 ][Ln(pin F ) 2 (THF) 2 ] (Ln = Yb, Lu), 3-Ln-K, [Li(THF)][Eu(pin F ) 2 (THF) 3 ], 4-Eu-Li, and [Li(THF)] 3 [Ln(pin F ) 3 (THF)] (Ln = Ce, Eu), 5-Ln-Li. Differences in planarity of a diamond core in bis-perfluoropinacolate species were found across the series of lanthanides. Changing the counterion resulted in significant structural changes, indicated by differences in the degree of THF solvation and buried volume. Increasing the stoichiometry of the synthesis revealed a pinwheel structure that was more symmetric by reflection than a three-fold rotation, and cyclic voltammetry of 5-Ce-Li showed an oxidation event at +0.45 V and a reduction event at –1.79 V relative to ferrocene.
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    Synthesis and structural analysis of lanthanide perfluoropinacolates
    (Wheaton College. (Norton, Mass.), 2022-05-16) Sclafani, Dominic J.
    Three new lanthanide perfluoropinacolate complexes ([K(THF)2][Ln(pinF)2(THF)x] (x = 3, Ln = Pr; x = 2, Ln = Tb, Ho)) have been synthesized and their solid-state structures were collected via single crystal X-ray diffractometry. Due to the fluorination of the pinacolate ligands, these complexes could display interesting electrochemical and luminescent properties. The bond angles and lengths of all three complexes were analyzed and it was found that the bond lengths in [K(THF)2][Tb(pinF)2(THF)2] and [K(THF)2][Ho(pinF)2(THF)2] were shorter than in [K(THF)2][Pr(pinF)2(THF)3]. As a result of these shorter bond lengths the bond angles in [K(THF)2][Tb(pinF)2(THF)2] and [K(THF)2][Ho(pinF)2(THF)2] were larger than in the [K(THF)2][Pr(pinF)2(THF)3] complex. This is due to a reduction in the radii of the lanthanide metal center, with praseodymium (Pr) being the largest of the three, terbium (Tb) the second, and holmium (Ho) the smallest, having ionic radii of 99.0 pm, 92.3 pm, and 90.1 pm, respectively.
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    Counterion Effect on the Luminescence of Lanthanide Complexes with Fluorinated Alkoxide Ligands.
    (Wheaton College (Norton, Mass.), 2022-05-16) Proctor, John Michael.
    Lanthanides have many commercial and industrial uses due to their luminescence characteristics. To be able to understand the effect that counterion size has on these characteristics can lead to optimization and better products. The ligand used in the synthesis of the complexes studied were alkoxide ligands. Alkoxide ligands have uses in industry when bonded to metals as a precursor to ceramics production, in this study the alkoxide ligand is used as an oxygen donor to the Ln(III) (Ln = Y, Ce, Pr, Eu) metal. The ligand used is also fluorinated and bidentate leading to a reduction in luminescence quenching. All complexes used were synthesized using THF as the solvent. The absorption and emission spectra were gathered in solution. It was found by changing the group 1 counterion there was a noticeable change in several of the luminescence characteristics.
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    Mechanochemical Synthesis of Thiolactams with Lawesson's Reagent
    (Wheaton College. (Norton, Mass.), 2021-05-16) Goodwin, Matthew; Includes bibliographical references (leaves 27-28).
    Thiolactams have proved to be an essential class of compounds in medicine, agriculture, and chemical synthesis. These compounds can be reliably synthesized with 2,4-bis(4- methoxyphenyl)-1,3,2,4-dithiadiphosphetane-2,4-dithione a thionation reagent that has widely become known as Lawesson's reagent (LR). In this study mechanochemistry, a new subfield of solid-state chemical synthesis which has proven useful because of its environmentally friendly nature and highly optimizable reaction conditions is used to develop the first known mechanochemical synthesis with Lawesson's reagent to produce thiolactams ring sizes 5 through 8.
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    Chronic exposure to methylmercury adversely affects response to oxidative stress.
    (Wheaton College (MA), 2019) Bauer, Jordan
    Methylmercury (MeHg) is an environmental neurotoxicant that has been shown to lead to physiological inefficiencies. Environmental contamination is a major concern, due to the high amounts of mercury pollution that affects a variety of food webs. Chronic exposure to MeHg has been shown to lead to the generation of reactive oxygen species (ROS) and inhibition of cell defense systems. The specific activities of three antioxidant enzymes, thioredoxin reductase (TrxR), glutathione peroxidase (GPx), and glutathione reductase (GR) are altered after chronic exposure to MeHg. Prior studies have shown generally, after MeHg exposure, the activity of TrxR and GPx decrease, while GR activity increases. These data imply that the glutathione system upregulates in the presence of MeHg, compensating for the inhibited activity of TrxR. This current study used kinetic spectroscopic methods to measure the activity and concentration of TrxR, GPx, and GR in Fundulus Heteroclitus exposed to MeHg in food at a rate of 35% of body weight per day for 3.5 weeks. We hypothesized that chronic exposure to MeHg lowers the activities of TrxR and GPx, and increases the activity of GR in brain and liver tissue. Results demonstrate that TrxR activity is unaffected after MeHg exposure in the liver of F. heteroclitus, whereas GPx and GR activity significantly decreased. Both TrxR and GPx activity decreased in the brain following MeHg treatment, while GR activity decreased only in males and remained unaffected in females. These findings provide insight into F. heteroclitus as an in vivo model for analyzing cellular responses to MeHg toxicity and how redox enzymes are affected by metal pollutants.