DESIGN AND SYNTHESIS OF NOVEL LIGANDS FOR BIOORTHOGONAL CATALYSIS, ASYMMETRIC SYNTHESIS, AND FERROMAGNETIC BEHAVIOR
Small molecule metal complexes have diverse applications including usage as catalysts, single molecule magnets, photosensitizers and pharmaceuticals. Nature itself frequently takes advantage of such complexes for fundamental biological processes. For example, heme-based iron complexes provide O2 for cellular respiration, while the active site of carbonic anhydrase catalyzes the hydration of CO2. Now it is our turn to define and exploit the chemical characteristics of such metal complexes. This body of work is specific to the development and application of novel aminated ligands that, when coordinated to various metal centers, can be used for an assortment of applications. The first research project in this work reports a new benzimidazole-based ligand, which dimerizes upon coordination to afford a trinuclear Cu(I) complex. Due to the linear geometry of the Cu(I) metal centers, paired with the strong nitrogen coordinating groups, the resulting complex is resistant to oxidation in both air and water, even in the presence of strong oxidants. The complex is shown to be efficient in the copper-catalyzed azide-alkyne cycloaddition (CuAAC) reaction and used to tag anticancer drug candidates in vitro. The complex is fully characterized, and a catalytic cycle is proposed. The next project focuses on a series of amidine-based ligands featuring chiral functional groups proximal to the coordinating site. In doing so, the reaction of achiral substrates may be influenced to promote the formation of one enantiomeric product over the other. The ligands are shown to be active in catalyzing the hydroxymethylation of silyl enol ethers in the presence of bismuth chloride in aqueous solutions. The reaction is optimized and yields are reported. In the final research project, Ni(II) dimer complexes are investigated for their magnetic behavior. For octahedral Ni(II) dimers bridged by a common anion, it has previously been established that the ferromagnetic superexchange between the Ni(II) metal centers can be enhanced as the angle of the bridging anion approaches 90 degrees. Novel imidazole and pyridine-based ligands are synthesized to add to the catalogue of chlorine-bridged complexes in the literature. Further, their bromine-bridged analogues are synthesized in order to determine the effect the identity of the halide bridge has on the magnetic properties of the complex. These three projects, while functionally different with individual aims, fundamentally share the goal of probing the chemical space that influences intrinsic properties of unique metal complexes.