Bis(dimethyl­ammonium) 2,2′-(1,3,6,8-tetra­oxo-2,7-diaza­pyrene-2,7-di­yl)diacetate

The asymmetric unit of title compound, 2C(2)H(8)N(+)·C(18)H(8)N(2)O(8) (2−), comprises one crystallographically independent dimethyl­ammonium cation and half of a 2,2′-(1,3,6,8-tetra­oxo-2,7-diaza­pyrene-2,7-di­yl)diacetate dianion. The anion lies on an inversion centre and the two carboxyl­ate groups are in trans positions based on the naphthaleneteracarb­oxy­lic diimide group. The crystal packing is stabilized by N—H⋯O hydrogen bonds between cations and anions, as well as by π–π inter­actions between the naph­thaleneteracarb­oxy­lic diimide groups [centroid–centroid distance = 4.812 (3) Å].