The periphery is central: The luminescent properties of boron(III) subporphyrazines are strongly influenced by their peripheral functionalization. These photoactive materials generate long-lived triplet excited states that mediate the sensitized production of singlet oxygen. Furthermore, their ability to behave either as oxidizing or reducing chromophores is promising for their application in molecular photovoltaics.
Physicochemical characterization of boron(III) subporphyrazines (SubPzs)—lower subphthalocyanine (SubPc) homologues—has been carried out for the first time. The SubPz macrocycle can act both as an oxidizing and a reducing entity, giving rise to stable radical anion or radical cation species, respectively. SubPzs are luminescent and exhibit fluorescence quantum yields that are in the range known for SubPcs. The peripheral substitution plays a dramatic role with respect to the luminescence properties. Moreover, as with SubPcs, deactivation of the singlet excited state of the SubPzs by intersystem crossing affords long-lived triplet excited states, which are amenable to being used as singlet-oxygen generators. Subporphyrazines are also promising electro- and photoactive materials for molecular photovoltaics.