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Structural Determination of Small Molecule Complexes, Macromolecular Systems, and Applications for Teaching Undergraduates
Crystallography is the analytical technique used to determine the arrangement of atoms within a highly ordered solid system. This method uses X-rays, which have a wavelength around 10-10 Å, to interact with the electrons in the atoms electron cloud to cause a diffraction pattern. Due to the technique’s ability to determine atomic placement it has become the best method of determining the structure of molecules in both small molecule and macro-molecular systems. (1) In organometallic catalysis, crystallography was used to characterize chelating N-heterocyclic carbene (NHC) ligands. NHC ligands with varying electronic and sterics were synthesized to fine tune the reactivity at the nickel center. (2) In systems with larger chelating ligands such as 18-crown-6 ethers, crystallography showed that the ionic radii of the late first row transition metals are too small to interact with the crown ether directly. However, hydrogen bonding networks were observed, and some metals underwent redox reactions. (3) In macromolecular chemistry, crystal structures were used to determine whether Cisplatin interacted with the thaumatin protein. Cisplatin is a platinum-based anti-cancer drug that usually bonds to sulfur residues on proteins and was previously reported to interact with some nitrogen-containing residues. (4) Results from these components were used to develop tutorials for students to learn basics of crystallography and understand how to determine their own structures. This work shows that undergraduate students can learn basic structure determination, as well as understand the basics of crystallography through a series of 3-hour modules presented in a Master’s course.