Spin-unrestricted density functional theory calculations were performed using ORCA 5.0.3. Geometry optimization was performed for all experimentally characterized and hypothetical compounds discussed in this work. The BP86 exchange-correlation functional was employed and the redefinition of Ahlrichs triple-ζ split-valence basis set def2-TZVP was used for geometry optimization and spectra calculations. For the NBO and QTAIM calculations, structures of 3 and 4 were optimized as restricted singlets using the Gaussian 16 revision C01 software package. Optimized geometries were validated to be energetic minima by the absence of imaginary vibrational frequencies. Calculations were performed at the BP86/def2-TZVP level of theory unless specified otherwise, in which case the 6-311G(d,p) triple-ζ People basis set or the redefinition of Ahlrichs double-ζ split-valence basis set (def2-SVP) was used. Grimme DFT-3 empirical dispersion correction with Becke-Johnson damping was employed in all calculations. The NBO calculations were performed with the NBO 6.0 software. QTAIM calculations and their visualizations were performed using the MultiWFN program. TD-DFT calculations of X-ray absorption transitions from the Co level, and DFT calculations of X-ray emission transitions to the Co 1s level were performed using the DFT-optimized atomic coordinates. The effects of spin-orbit coupling were included using a quasi-degenerate perturbation theory approach to calculate mixing between states with different multiplicity (achieved by setting DoSOC to "true"). A tight convergence requirement was imposed for all calculations. The calculated pre-edge and emission transitions were expressed as Gaussian functions with half-widths of 0.85 eV (Co K-edge XAS) and 1.55 eV (Co Kβv2c XES) to account for core-hole and instrument broadening. The computed transition energies were shifted by 196.2 eV (Co K-edge XAS) and 195.4 eV (Co Kβv2c XES) to compensate for the inaccuracies in DFTcalculated core-hole potentials. Contour plots of the molecular orbitals associated with the absorption and emission transitions were visualized from the DFT output using Chemcraft 1.8 and their compositions were extracted from the DFT output using MOAnalyzer 1.61.