Dichloridobis(1-ethyl-2,6-dimethylpyridinium-4-olate-κO)zinc(II)

In the title compound, [ZnCl2(C9H13NO)2], the ZnII ion is coordinated by two Cl− anions and two O atoms of two zwitterionic organic ligands in a distorted tetrahedral arrangement. In the crystal, molecules are linked into sheets parallel to the bc plane by C—H⋯Cl and C—H⋯O hydrogen bonds and weak π–π interactions [centroid–centroid distance = 3.669 (1) Å].


Comment
Organic pyridinium salts have been widely used as guest molecules in the construction of supramolecular architecture in the field of chemistry (Damiano et al., 2007). Pyridinium cations are good candidates for second-harmonic generation (SHG) materials because they possess large hyperpolarizabilities (β) irrespective of the short cutoff wavelength. Since pyridinium cations are ionic species, they possess an easy tunability into noncentrosymmetric structures by changing counter anions (Anwar et al., 1997(Anwar et al., , 1999. The zinc halides substituted in pyridines lead to a variety of complexes involving zinc centers and were shown to be catalytically active for the coupling of carbon dioxide and epoxides to provide high molecular weight polycarbonates and cyclic carbonates (Darensbourg et al., 2003). As a part of our interest, we report here the crystal structure of the title pyridinium dichlorozinc(II) complex.
In the title molecule ( Fig. 1), the Zn II atom is coordinated by a pair of pyridinium oxide group and terminal halide ions in a distorted tetrahedral arrangement. The organic ligand exists in a zwitterionic structure, involving a conjugated pyridinium fragment. The C atoms of methyl substituents at C2, C6, C12 and C16 lie in the plane of the corresponding pyridinium rings, which are evident from the C9-C2-N1-C6 [176.99 (16) The packing of the molecules in the unit cell is promoted by the existence of weak C-H···O, C-H···Cl and π···π types of intermolecular interactions. The C8-H8A···O1 interaction leads to the formation of a centrosymmetric R 2 2 (16) dimer (Bernstein et al., 1995). The Cl1 atom acts as an acceptor in a linear fashion for the methyl group hydrogen from the neighbouring molecule [ Fig. 2 and Table 2]. The C13-H13···Cl2 intermolecular interaction also contributes to the crystal packing, which form zigzag chains along the c axis. The crystal structure is further augmented by π···π interaction between adjacent pyridinium rings [Cg1(x, y, z)···Cg1(-x, y, 1/2-z) = 3.669 (1) Å; where Cg1 is the centroid of the (N1-C6) ring, Experimental 1-Ethyl-2,6-dimethyl-4(1H)pyridinone trihydrate (EDMP.3H 2 O) was synthesized according to the reported method (Garratt, 1963). The title complex was prepared by the reaction of ZnCl 2 with EDMP.3H 2 O in a 1:2 molar ratio in aqueous medium.
Single crystals were harvested after a typical growth period of 15 days from a saturated aqueous solution at 303 K by slow evaporation of the solvent.
supplementary materials sup-2 Refinement H atoms were positioned geometrically (C-H = 0.93-0.97 Å) and allowed to ride on their parent atoms, with U iso (H) = 1.5U eq (C) for methyl H and 1.2U eq (C) for other H atoms. Fig. 1. The molecular structure of the title compound, showing 50% probability displacement ellipsoids.

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 > 2sigma(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.