title: Bis(dimethyl-ammonium) 2,2'-(1,3,6,8-tetra-oxo-2,7-diaza-pyrene-2,7-di-yl)diacetate.
abstract: 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].
authors.forename: Lan-Ping
authors.initials: LP
authors.lastname: Xu
authors.forename: Wen-Na
authors.initials: WN
authors.lastname: Zhao
authors.forename: Lei
authors.initials: L
authors.lastname: Han
references.citation: Angew Chem Int Ed Engl. 2007;46(13):2238-40
references.pmid: 17309089
references.citation: Acta Crystallogr A. 2008 Jan;64(Pt 1):112-22
references.pmid: 18156677