"Two in one": an unprecedented mixed anion, Ba2(C3N3O3)(CNO), with the coexistence of isolated sp and sp2π-conjugated groups.

The combination of different types of π-conjugated anions into one structure can lead to multifunctional materials with intriguing properties. Herein, we successfully developed a new mixed anion compound, Ba2(C3N3O3)(CNO) (I), containing two types of π-conjugated groups, planar (C3N3O3)3- six-membered rings and linear (CNO)- units, for the first time. The compound I exhibits the wide bandgap of 4.82 eV and high absorption coefficients in the wavelength range of 200-280 nm; this indicates that it is a potential optical detection material in the solar-blind region.