Doctor of Philosophy (PhD)
In Chapter 2, [CuII(impy)2(NO3)]NO3·H2O was synthesized, and it shows a reversible Cu(II)/Cu(I) wave in DMF with E1/2 = 0.1 V vs. Ag/AgCl (−0.46 V vs. Fc+/Fc). Chemical reduction of [CuII(impy)2(NO3)]NO3·H2O with ascorbate generated a yellow Cu(I)-impy solution which when exposed to air (CO2 + O2) formed [CuII(impy)(C2O4)(H2O)]·2H2O. However, pure CO2 does not react with the Cu(I) solution, while pure O2 does lead to formation of the oxalate complex. Moreover, labeling experiments using 13CO2-O2 (1:1 v/v) produced only unlabeled oxalate (via IR and ESI-MS), also indicating that it did not come from CO2. So, our results indicate that [Cu(impy)2]+ is not able to reduce CO2; however, Cu(II) impy complexes can bind with the oxalate that originates from the oxidation of the ascorbate. In chapter 3, a macrocyclic copper(II) pyridyltriazole complex with externally bound chelating sulfate ions was prepared and characterized.
In Chapters 4 and 5, we studied the control of binding of guests via redox reactions of supramolecular host complexes. In one study, Cu(II) complex with (2,7-naphthalenediylbis(methylene))bis(pyridyltriazole) as a ligand has been shown to bind the neutral guest Dabco internally, giving [Cu2(npt)2(µ-Dabco)]4+. When Dabco was added to [Cu2(npt)2](PF6)4, the redox wave for oxidation of Cu(I) to Cu(II) shifted slightly, indicating some redox control of guest binding. In another study, electrochemistry of Mn beta-diketonate complexes, Mn(acac)3, and Mn(dbm)3, in the presence of Na+ ion guests (NaClO4) was investigated. Our hypothesis was that [MnII(diket)3]- would bind to Na+ more strongly than neutral [MnIII(diket)3]. This should result in the [Mn(diket)3]0/- redox potential shifting towards more positive values in the presence of added Na+. Mn(acac)3 did not show reversible redox behavior whereas Mn(dbm)3 showed reversible behavior. As Na+ guest ions are added to the Mn(dbm)3 solution, its E1/2 shifts in the positive direction. From the change in E1/2 with added [Na+], we concluded that the reduced host ([MnII(diket)3]-) binds to one Na+ ion more than the neutral host ([MnIII(diket)3]). In chapter 6, redox and host-guest reactions of a substituted Cu(II) m-xpt complex were explored. In Chapter 7, three Pt complexes were synthesized and their Pt---Pt interactions were studied in solution using UV-vis spectroscopy.
Sharma, Ruchika, "Redox and Host-Guest Reactions of Transition Metal Complexes" (2023). LSU Doctoral Dissertations. 6166.
Available for download on Friday, May 17, 2030