Bis(phenothiazine)arene diradicaloids: isolation, characterization and crystal structures

A class of bis(phenothiazine)arene dications were isolated and structurally characterized by using weakly coordinating anions. Their electronic structures were investigated by various experiments in tandem with DFT calculations. They all feature singlet ground states with a considerable diradical character and may be regarded as nearly pure diradicals. Our work demonstrates the important role of orthogonal alignment of spin-carrying pi-systems in tuning the electronic structures of bis(triarylamine) dications.