Aerobic reaction between [Ru^II(DMSO)₄Cl₂], a redox-active 2-aminophenol-based ligand (H₂L¹: 2-[2-(benzylthio)phenylamino]-4,6-di-tert-butylphenol) and Et₃N in MeOH under refluxing conditions afforded a purple complex [Ru(L¹)₂] (S = 0). Structural analysis reveals that the tridentate ligand coordinates in a mer conformation providing a distorted octahedral RuN₂O₂S₂ coordination. Cyclic voltammetry on 1 in CH₂Cl₂ reveals the accessability of the monocation, dication and monoanion forms. Reddish purple monocation [Ru(L¹)₂](PF₆)·CH₂Cl₂ ([1^OX1](PF₆)·CH₂Cl₂; S = 1/2) and green dication [Ru(L¹)₂](BF₄)₂·H₂O ([1^OX2](BF₄)₂·H₂O; S = 0) have been isolated through the chemical oxidation of 1 in CH₂Cl₂ by [Fe^III(η⁵-C₅H₅)₂](PF₆) and AgBF₄, respectively. A structural analysis of the single crystals of the monocation and the dication with the compositions [1^OX1](PF₆)·CH₂Cl₂·H₂O (2) and [1^OX2](BF₄)₂·1.7H₂O (3), respectively, has been done. Metrical (metal–ligand and ligand backbone) parameters, values of metrical oxidation states of coordinated ligands, ¹H NMR spectra of 1 and [1^OX2](BF₄)₂·H₂O, EPR spectra of [1^OX1](PF₆)·CH₂Cl₂, X-ray photoelectron and UV-VIS-NIR spectra of 1–3, spin population analysis from broken-symmetry (BS) density functional theory (DFT) calculations and quasi-restricted orbital (QRO) analysis have allowed us to assign the electronic structure of the complexes. The complexes exhibit highly covalent metal–ligand interactions. The electronic states of 1, [1^OX1]¹⁺ and [1^OX2]²⁺ are best described as [Ru^II{(L^ISQ)˙⁻}₂] ↔ [Ru^III{(L^AP)²⁻}{(L^ISQ)˙⁻}] (S = 0), [Ru^III{(L^ISQ)˙⁻}₂]¹⁺ (S = 1/2) and [Ru^II{(L^IBQ)⁰}₂]²⁺ ↔ [Ru^III{(L^ISQ)˙⁻}{(L^IBQ)⁰}]²⁺ (S = 0), respectively. Notably, all redox processes are ligand-centred. Absorption spectral properties have been rationalized based on time-dependent (TD)-DFT calculations. For 1, the appearance of an IVCT band at 1100 nm supports its Class II–III (borderline) ligand-based mixed-valence character.