EPR/UV–Vis–NIR spectroelectrochemical characterization of 10H-phenothiazinyl-substituted oligothiophenes

• The charge carriers of the mono- and bis-phenothiazinyl-substituted compounds have been investigated using EPR and UV-vis-NIR spectroelectrochemistry. • In bis-phenothiazinyl-substituted compounds with thiophene linker, the charge is predominantly localized on the thiophene moiety. • For the compounds containing central phenyl rings in the thiophene linker, the oxidation is phenothiazine-based. The charged species of 10 H -phenothiazinyl-substituted thiophenes have been investigated by means of combined in situ electron paramagnetic resonance (EPR) and ultraviolet−visible−near infrared (UV−Vis−NIR) spectroelectrochemistry. The molecular structure of the compounds under study contains one or two phenothiazine moieties, which are connected by various thiophene linkers in the case of the latter. The optical and magnetic properties of the radical cations and dications as well as the information about their stability were provided. The impact of the linker structure on charge localization (on phenothiazine or thiophene moiety) for bis-phenothiazinyl-substituted compounds was investigated. The experimental data were supported by density functional theory (DFT) calculations, which predicted the favored charged structures of the studied compounds.