Probing the aromaticity of bis(diazolo)pyrazine radical anions

The aromaticity of a series of heterocyclic radical anions of bis(diazolo)pyrazine type, X(CN)₂N₂(CN)₂Y (X, Y = O, S, Se, Te) was explored by the methods of electron density of delocalized bonds (EDDB) and gauge-included magnetically induced currents (GIMIC). The existence of T-aromaticity that encloses the entire molecule, which was due to delocalization of seven β-electrons, was shown. The degree of aromaticity depends on the nature of the X(Y) heteroatom and varies in the series S > O > Se > Te.