title: N-Methylpyridinium 3-cyano-4-(dicyanomethylene)-5-oxo-4,5-dihydro-1H-pyrrol-2-olate.
abstract: The crystal structure of the title compound, C(6)H(8)N(+).C(8)HN(4)O(2)(-), is characterized by three independent ion pairs (A, B and C) in the asymmetric unit. Each ion pair consists of an anion and a cation, and the three ion pairs have similar geometric parameters. All the anions are arranged as dianion dimers via two N-H.O hydrogen bonds and the dimers form one-dimensional columns parallel to the b axis as a result of pi-pi interactions. The cations are also stacked, in two different ways: one type of stacking consists of alternating A and B cations, while the other type consists of C cations only. Each dianion dimer stack is surrounded by eight stacks of cations and is not connected directly to other dianion stacks.
authors.affiliation: Chemistry Department, Moscow State University, 119899 Moscow, Russia. tafeenko@biocryst.phys.msu.su
authors.forename: Viktor A
authors.initials: VA
authors.lastname: Tafeenko
authors.forename: Aleksander N
authors.initials: AN
authors.lastname: Nikolaev
authors.forename: Rene
authors.initials: R
authors.lastname: Peschar
authors.forename: Olga V
authors.initials: OV
authors.lastname: Kaukova
authors.forename: Henk
authors.initials: H
authors.lastname: Schenk
authors.forename: Leonid A
authors.initials: LA
authors.lastname: Aslanov