The influence of a redox-active ligand on spin-changing events induced by the coordination of exogenous donors is investigated within the cobalt complex [Co-II(DPP center dot 2-)], bearing a redox-active DPP2- ligand (DPP = dipyrrin-bis-(o,p-di-tert-butylphenolato) with a pentafluorophenyl moiety on the meso-position. This square-planar complex was subjected to the coordination of tetrahydrofuran (THF), pyridine, tBuNH(2), and AdNH(2) (Ad = 1-adamantyl), and the resulting complexes were analyzed with a variety of experimental (X-ray diffraction, NMR, UV-visible, high-resolution mass spectrometry, superconducting quantum interference device, Evans method) and computational (density functional theory, NEVPT2-CASSCF) techniques to elucidate the respective structures, spin states, and orbital compositions of the corresponding octahedral bis-donor adducts, relative to [Co-II(DPP center dot 2-)]. This starting species is best described as an open-shell singlet complex containing a DPP center dot 2- ligand radical that is antiferromagnetically coupled to a low-spin (S = 1/2) cobalt-(II) center. The redox-active DPPn- ligand plays a crucial role in stabilizing this complex and in its facile conversion to the triplet THF adduct [Co-II(DPP center dot 2)-(THF)(2)] and closed-shell singlet pyridine and amine adducts [Co-III(DPP3)-(L)(2)] (L = py, tBuNH(2), or AdNH(2)). Coordination of the weak donor THF to [Co-II(DPP center dot 2-)] changes the orbital overlap between the DPP center dot 2- ligand radical pi-orbitals and the cobalt(II) metalloradical d-orbitals, which results in a spin-flip to the triplet ground state without changing the oxidation states of the metal or DPP center dot 2- ligand. In contrast, coordination of the stronger donors pyridine, tBuNH(2), or AdNH(2) induces metal-to-ligand single-electron transfer, resulting in the formation of low-spin (S = 0) cobalt-(III) complexes [Co-III(DPP3-)(L)(2)] containing a fully reduced DPP3- ligand, thus explaining their closed-shell singlet electronic ground states.