Molecular magnetism is a field highly reliant on understanding the electronic structure of the molecule in question. In Chapter 1 of this dissertation, we review the connection of state structure to bonding of ligands and review contemporary understanding of energy state manifolds, with a focus on cobalt complexes and transition metals. These complexes are used to demonstrate the growth of the study of molecular magnetism, and we discuss the growth of theory with the application of spectroscopic and magnetic techniques for their use in probing state structure. In Chapter 2, we explore the use of ligand coordination to fine-tune the electronic structure of transition metals and characterize a series of molecules through spectroscopy and magnetometry. This is done by synthesizing the first reported Co(II) and Co(I) mesoionic carbene complexes. In Chapter 3, we explore the connection of spectroscopy and magnetometry through the study of highly symmetric octahedral Co(II) complexes and propose a new method of modelling magnetic data in systems with highly complex electronic structures in order to address current problems in modelling systems with complex state structures.