3,3′-Carbonyldipyridinium bis(perchlorate)

In the title molecular salt, C11H10N2O2+·2ClO4 −, the complete cation is generated by crystallographic twofold symmetry. The dihedral angle between the pyridyl rings is 67.07 (7)°. The crystal structure features N—H⋯Cl hydrogen bonds, forming sheets in the ab plane.

In the title molecular salt, C 11 H 10 N 2 O 2+ Á2ClO 4 À , the complete cation is generated by crystallographic twofold symmetry. The dihedral angle between the pyridyl rings is 67.07 (7) . The crystal structure features N-HÁ Á ÁCl hydrogen bonds, forming sheets in the ab plane.

Related literature
For the dipyridyl ketone dication, see: Crook & McElvain (1930); Favaro et al. (1990). For metal complexes of di-3pyridyl ketone, see: Chen & Mak (2005); Chen et al. (2009 Data collection: APEX2 (Bruker, 2007); cell refinement: APEX2 and SAINT (Bruker, 2007); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL and PLATON (Spek, 2009 Di-3-pyridyl ketone is an extraordinary ligand within the family of basic building blocks for construction of metalorganic complexes with intriguing architectures (Chen & Mak, 2005;Chen et al., 2009). However, the crystal structure of salts with the dipyridyl ketone dication is rarely reported until now. Several related literatures discussed the relationship between the acid-base properties of the dipyridyl ketone isomers and the positions of the nitrogen atoms on the rings, which were investigated by spectrophotometric measurements (Crook & McElvain, 1930;Favaro et al., 1990). In the present context, we report the structure of diprotonated di-3-pyridyl ketone perchlorate salt (Fig. 1). The two pyridyl rings exhibit a dihedral angle of 67.07 (7)°. The crystal structure is stabilized by N-H···(perchlorate) hydrogen bonds forming sheets in the ab plane.

Experimental
Di-3-pyridyl ketone was prepared following the literature procedure of Chen & Mak (2005). Copper(II) perchlorate (37 mg, 0.1 mmol) was heated with di-3-pyridyl ketone (18 mg, 0.1 mmol) in acetonitrile (5 ml) at 373 K for 24 h. After cooling to room temperature, the precipitate which had formed was filtrated off. Crystals of the title salt was deposited by slow evaporation of the filtrate, which can be viewed as the product of the perchloric acid from the copper(II) perchlorate and di-3-pyridyl ketone (yield 11.5 mg, 30% based on di-3-pyridyl ketone).

Refinement
H atoms were placed in idealized positions and allowed to ride on their parent atoms, with C-H = 0.93 Å and N-H = 0.86 Å, and with U iso (H) = 1.2U eq (C,N).

Special details
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes. 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 > 2σ(F 2 ) is used only for calculating R-factors(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.