Bis(dimethyl-ammonium) 2,2'-(1,3,6,8-tetra-oxo-2,7-diaza-pyrene-2,7-di-yl)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 dimethyl-ammonium cation and half of a 2,2'-(1,3,6,8-tetra-oxo-2,7-diaza-pyrene-2,7-di-yl)diacetate dianion. The anion lies on an inversion centre and the two carboxyl-ate groups are in trans positions based on the naphthaleneteracarb-oxy-lic diimide group. The crystal packing is stabilized by N-H⋯O hydrogen bonds between cations and anions, as well as by π-π inter-actions between the naph-thaleneteracarb-oxy-lic diimide groups [centroid-centroid distance = 4.812 (3) Å].