Synthesis and Characterization of Products Produced from Aluminum Monohalide Precursors

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DeCarlo, Samantha
Eichhorn, Bryan W
In this thesis, the synthesis, characterization and applications of aluminum compounds and cluster from aluminum monohalide solutions, AlX (where X = Cl or Br) are described. Chemistry of AlX solutions is not well understood, but AlX has proven adept at producing aluminum metalloid clusters (AlnLm where n>m). A brief overview of the renaissance of low-valent aluminum chemistry and select low-valent Al products is presented as background. The neutral mononuclear aluminum tris-bpy complexes [Al(Mebpy)3] and [Al(tBubpy)3] have been synthesized, isolated, and structurally characterized via X-ray single crystal diffraction. These complexes are the first structurally characterized homoleptic tris-bpy complexes and were studied via ESI-MS, d.c. magnetic susceptibility, electrochemical analyses. Electrochemistry demonstrates that six oxidation states are accessible from both neutral complexes: [Al(Rbpy)]n (n = -3 to 3, R = Me or tBu). The [Al(Mebpy)3] complex demonstrates unexpected magnetic ordering at 19 K which is not observed in [Al(tBubpy)3] nor in transition metal centered tris-bpy congeners. Synthesis, isolation, and characterization of the low-valent aluminum cluster [LiOEt2]2[HAl3(PPh2)6] via NMR and ESI-MS studies are also described. These experiments proved the presence of an H atom, and developed a complete and comprehensive picture of the structure, magnetism, and spectroscopy of this compound. Solution studies of reactions of AlBr with tBu-thiolate via ESI-MS show the formation and identification of [Al17Br(StBu)10S3]1-, [Al10(StBu)4S5]1-, [Al13(StBu)4BrS]1-, and [Al5(StBu)7Br]1-¬ in solution. The preparation and characterization of the aluminum (III) thiolate complex, Na[Al(SPh)4], is also described. These studies demonstrate the importance of reaction conditions in the formation of aluminum clusters in solution, and the viability of thiolate ligands to isolate low-valent aluminum products. Al nanoparticles (NP) can be produced from AlX solutions and have been successfully supported on both graphene and graphene oxide. The reduction of AlX solutions are quick, facile, and performed at low temperatures (-78°C). In the presence of graphene, faceted and well-dispersed graphene supported Al-NPs can be obtained. The [AlBrNEt3]4 cluster is isolated from AlBr⋅NEt3 solution and is soluble in toluene and diethyl ether. The burning rate of the hydrocarbon fuel doped with the tetramer is studied. There is an increase in burning rate attributed to the presence of [AlBrNEt3]4.