The Exploration of Small Molecules, Lanthanide Complexes, and Catalysis using Electronic Structure Theory, Dynamics, and Machine Learning

With the ever increasing availability of computational resources, more challenging chemical systems can be studied. Among these challenges are the rotational and vibrational spectra of diatomic molecules within spectroscopic accuracy, the environmental perturbations induced on a rotating water molecule, the prediction of free binding energies of lanthanide complexes using machine learning, and the study of catalytic mechanisms through a theoretical framework. High levels of electronic structure theory were combined with a rigorous treatment of either the anharmonic vibrational wave functions to study diatomic molecules or the rotational wave functions to study H₂O-pH₂ interactions. The former was initially applied to the CF⁺ cation and excellent agreement was observed between theoretical and experimental spectroscopic constants. Likewise, the H₂O-pH₂ interactions were utilized to identify satellite peaks in the infrared spectra of a H₂O-doped, pH₂ crystal lattice. These peaks most likely occur due to a vacancy site directly around the H₂O molecule. The study of lanthanide complexes is challenging due to their unique electronic structure. Specifically, the study of lanthanide-tris-β-diketone complexes was studied to calculate their respective free binding energies. Machine learning was utilized in this instance to act as the function which mapped the structure of the β-diketone ligands to the free binding energies. Predictions were made and several β-diketone ligands were identified which maximized the separation between lanthanide and lutetium. Finally, the study of catalytic mechanisms using theoretical methods is not without challenge due to the complex electronic structure of such systems. The hydrogen evolution reaction, the dehalogenation of CH₂Cl₂, the hydrogenation of small, unsaturated hydrocarbons, and the hydroformylation reaction were studied using either molecular electrocatalysts or transmetalated forms of the HKUST-1 metal-organic framework.