Tetrakis(2,6-diaminopyridinium) diphthalate 2,6-diaminopyridine

In the title compound, 4C5H8N3 +·2C8H4O4 2−·C5H7N3, the asymmetric unit consists of two protonated diaminopyridine cations, one phthalate anion and one half of a diaminopyridine molecule, which has twofold rotation symmetry and is disordered over two positions with a site-occupancy ratio of 0.534 (3):0.466 (3). In the disordered structure, both pyridine rings are essentially planar, with maximum deviations of 0.011 (2) and 0.006 (2) Å, and these two rings are inclined to one another at a dihedral angle of 79.86 (10)°. In the crystal structure, intermolecular N—H⋯O and C—H⋯O hydrogen bonds link the ions and molecules into a three-dimensional network. The structure is further stabilized by C—H⋯π interactions.

In the title compound, 4C 5 H 8 N 3 ÁC 5 H 7 N 3 , the asymmetric unit consists of two protonated diaminopyridine cations, one phthalate anion and one half of a diaminopyridine molecule, which has twofold rotation symmetry and is disordered over two positions with a site-occupancy ratio of 0.534 (3):0.466 (3). In the disordered structure, both pyridine rings are essentially planar, with maximum deviations of 0.011 (2) and 0.006 (2) Å , and these two rings are inclined to one another at a dihedral angle of 79.86 (10) . In the crystal structure, intermolecular N-HÁ Á ÁO and C-HÁ Á ÁO hydrogen bonds link the ions and molecules into a three-dimensional network. The structure is further stabilized by C-HÁ Á Á interactions.
Data collection: APEX2 (Bruker, 2005); cell refinement: SAINT (Bruker, 2005); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL and PLATON (Spek, 2009).  Zuhri & Cox, 1989). It has amino-imino tautomerization property (Inuzuka & Fujimoto, 1990) and it can be used to prepare polymer complexes with lead(II), cadmium(II) and zinc(II) (El-Mossalamy, 2001). Phthalic acid is an aromatic dicarboxylic acid and can be used in its anhydride form to produce other chemicals such as dyes, perfumes, phthalates and many others. It can be prepared from the catalytic oxidation of naphthalene in a new production method (Brike et al., 2002). Some of its derivatives have anti-tumor promoting action (Yamamoto et al., 1990). The crystal structure of this molecule can be helpful in future experimental and theoretical studies.

Experimental
In order to prepare the title crystal, phthalic acid (0.01 mol, 1.75 g) was dissolved in 25 ml of THF in a round bottom flask.
In a separating funnel, 2,6-diaminopyridine (0.03 mol, 3.75 g) was dissolved in 20 ml of THF. 2,6-Diaminopyridine solution was added in drops to the flask of phthalic acid solution with stirring. The reaction mixture was left stirring for 3 h at room temperature. Colourless crystals were separated, washed with THF and dried at 80°C. supplementary materials sup-2 Refinement Hydrogen atoms attached to nitrogen atoms (excepting for H8A, H8B, H8AA and H8AB) were located in a difference Fourier map. H8A, H8B, H8AA, H8AB and all the hydrogen atoms attached to carbon atoms were positioned geometrically [N-H = 0.86 Å, C-H = 0.93 Å] and were refined using a riding model, with U iso (H) = 1.2 U eq (N, C). Rigid, similarity and simulation restraints were applied to the disordered diaminopyridine ring. Fig. 1. The molecular structure of the title compound, showing 30% probability displacement ellipsoids and the atom-numbering scheme. Open bonds indicate the minor disordered component.

Special details
Experimental. The crystal was placed in the cold stream of an Oxford Cyrosystems Cobra open-flow nitrogen cryostat (Cosier & Glazer, 1986) operating at 100.0 (1) K. Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating Rfactors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.