Investigation of Molecular Transition Metal Complexes: Structures, Magnetic Properties, and Reactivities

The dissertation describes the work on transition metal complexes to determine their structures, magnetic properties, and reactivities. Molecular magnetic complexes containing one cobalt(II) or rhenium(IV) ion have been studied to obtain their characteristic zero-field splittings and spin-phonon couplings by magnetometry and advanced spectroscopies. The investigation of spin relaxation and phonon features gives insight into potential magnetic relaxation mechanisms. Studies by ligand field theory, including ab initio ligand-field analysis, show how coordination environments of the metal centers affect the magnetic properties. Through the analyses, the impact of the coordination geometry/symmetry on the zero-field splittings can be explained. Such understanding of magneto-structural correlations is needed for the new design of single-molecule magnets. Additionally, Chapter V focuses on the hydrolysis reactivities of niobium(V) and tantalum(V) complexes, revealing unusual differences in the reactivities of the Group 5 metals. To our knowledge, this is the first example of the formation of two different complexes that maintain the V oxidation state in both metals. The studies in this dissertation give us a comprehensive understanding of magnetic anisotropy of metal complexes and the effect of coordination environment and phonon properties that lead to spin relaxation. Additionally, different hydrolysis reactivities of the Group 5 complexes may facilitate the separation of niobium and tantalum from their parent ores.