Master of Science (MS)
This research addresses the synthesis and characterization of Cu(II) complexes of silicon-based multidentate β-diketonate ligands. The possible products of the synthesis include (where L represents the coordinated ligand) cube Cu12L8, decahedron Cu24L16, and dodecahedron Cu30L20. This study aims to determine the structure of these discrete molecules, which may have applications in drug delivery, fuel storage, and chemical retention. Different techniques were involved in the characterization of Cu(II) complexes: Electrospray Ionization Time of Flight Mass Spectrometry (ESI-TOF MS), Atomic Force Microscopy (AFM) and Analytical Ultracentrifugation (AUC). In ESI-TOF MS, the exact mass of the molecules was attempted to be determined by experimenting if multiply charged ions could occur with these complexes. Although no multiply charged ion peaks were discovered, different experimental conditions yielded different ESI-TOF MS spectra. Additionally in ESI-TOF MS, peaks having large m/z values containing copper atoms were discovered. In AFM studies, heights of multiple copper complexes were measured to see if the discrete molecules of cube (2 nm), decahedron (3.5-4.5 nm), and dodecahedron (5 nm) could be identified. In creating an AFM histogram, the frequency of heights could be used to determine what kind of complexes were being formed and in what percentage. In the studies conducted, there were common occurrences of the samples at or around the heights of the projected structures (e.g. cube, decahedron, and dodecahedron). Additionally, there was a substantial occurrence of measured heights (i.e. 8 nm and 10 nm) that indicated possible aggregation of the discrete molecules. The AUC technique was used to determine whether the samples contained a pure compound or a mixture of discrete molecules, and also to estimate their molecular weight. What was found in the AUC studies of the Cu(II) complexes of silicon-based multidentate β-diketonate ligands were molecular weights similar to the empirical formula of the molecules (i.e. Cu3(MeSi(phac)3)2: 1322.07 g/mol; Cu3(MeSi(phpr)3)2: 1567.80 g/mol) and samples that were polydisperse. No evidence from AUC showed the discovery of compounds which had molecular weights similar to the proposed polyhedra. The numbers are based on assumed densities of 1.138 g/mL.
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Casey, Jonathan Stephen, "Synthesis and Analysis of Copper Beta-Diketonate Complexes" (2014). LSU Master's Theses. 167.