Chemistry
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Item The Structural and Electrochemical Effects of Varying the Group 1 Counterion in Fluorinated Alkoxide Lanthanide Complexes(2023-05-15) Slaney, CassandraIn 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.Item 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.Item Chronic exposure to methylmercury adversely affects response to oxidative stress.(Wheaton College (MA), 2019) Bauer, JordanMethylmercury (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.Item Comparison of two indigo dye derivatives in the spectrophotometric detection of copper in aqueous media.(Wheaton College (MA), 2019) Oberg, CatrinaCopper is an essential element in the human body, playing a role in redox reactions and substrate activation reactions. Several diseases, including Menkes disease and Wilson’s disease, are associated with copper metabolism in the body. Copper primarily enters the body through our diet (by consuming foods like meat, bread, and beans) and through drinking water. Copper compounds can enter drinking water sources through copper pipes in plumbing infrastructure and through runoff from insecticides and fertilizers. The World Health Organization recommends that the amount of copper in drinking water does not exceed 2 ppm; for this reason the accurate detection of copper in aqueous media is needed. The objective of this investigation is to investigate the binding constants and thermodynamic parameters for two detection methods using indigo dye derivatives and spectrophotometric analysis. Copper cations (Cu2+(aq)) form a 1:1 complex with both indigo carmine (IC) and potassium indigotrisulfonate (KItS) in aqueous solutions. Both dyes selectively form a complex with copper and do not form a complex with other metal (II) cations like cadmium, magnesium, lead, or calcium. The Cu-KItS system in water was found to be the most favorable reaction because it had the highest binding constants and highest magnitude negative Gibb’s free energy. The detection limit of copper cations in water was found to be 0.031 ppm using the Cu-KItS system in water compared to 0.076 ppm using the Cu-IC system in water.Item Detection and Quantification of Tetracycline using Energy-Efficient Synthesized Carbon Dots(Wheaton College (Norton, MA)., 2020-05-10) Nerone, SophieThe use of carbon dots as sensors has increased in popularity and they have been found to be efficient fluorescent probes with high sensitivity and selectivity. The carbon dot synthesis efficiency was improved in this study. Carbon dots were then used to detect and quantify the commonly used antibiotic, tetracycline. Tetracycline is an oral, broad-spectrum antibiotic used to treat infections caused by gram-positive bacteria. Additionally, thermodynamic constants for the association of carbon dots and tetracycline (CD-TC) were investigated using fluorescence spectroscopy. Job’s plot analysis showed that tetracycline and carbon dots display 1:1 stoichiometry. The binding constants, K, for the complexation were determined using a modified Stern-Volmer equation and yielded values 2.50 × 10^4, 1.04 × 10^4, 2.02 ×10^4, and 2.50 × 10^4 M-1 for 298.15 K, 303.15 K, 308.15 K, and 313.15 K, respectively. Thermodynamic analyses suggest that the CD-TC complex occurs spontaneously with DG being negative between 298-313 K. Both the enthalpy, DH, and the entropy, DS, of the reaction were also negative at higher temperatures (308-313 K) suggesting that the reaction was exothermic, enthalpy-driven, and the disorder of the isolated system decreased. However, at lower temperatures (298- 303 K) values of DH and DS were both positive suggesting that the CD-TC association was entropy-driven. Future work can include replication of this experiment for reproducibility and probing of other antibiotics with these carbon dots.