An ortho­rhom­bic polymorph of pyrazino­[2,3-f][1,10]phenanthroline-2,3-dicarbonitrile

The title compound, C(16)H(6)N(6), is a polymorph of the previously reported structure [Kozlov & Goldberg (2008 ▶). Acta Cryst. C64, o498–o501]. Unlike the previously reported monoclinic polymorph (space group P2(1)/c, Z = 8), the title compound reveals ortho­rhom­bic symmetry (space group Pnma, Z = 4). The mol­ecule shows crystallographic mirror symmetry, while the previously reported structure exhibits two independent mol­ecules per asymmetric unit. In the title compound, adjacent mol­ecules are essentially parallel along the c axis and tend to be vertical along the b axis with dihedral angles of 72.02 (6)°. However, in the reported polymorph, the entire crystal structure shows an anti­parallel arrangement of adjacent columns related by inversion centers and the two independent mol­ecules are nearly parallel with a dihedral angle of 2.48 (6)°.