Dichlorido(4′-phenyl-2,2′:6′,2′′-terpyridyl)zinc

The title compound, [ZnCl2(C21H15N3)], was obtained from the reaction of ZnCl2·4H2O with 4′-phenylterpyridine (L) and disodium 2,6-dipicolinate. The Zn2+ cation is ligated by the N atoms of the tridentate L ligand and two chloride anions, forming a ZnN3Cl2 polyhedron with a distorted trigonal–bipyramidal coordination geometry. In the crystal, nonclassical C—H⋯Cl hydrogen bonds are observed.

Data collection: SMART (Bruker, 2001); cell refinement: SAINT (Bruker, 2002); 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: SHELXL97.   ; ;Ma, Bi et al. (2010); Ma, Cao et al. (2010)). We are particularly interested in the design and synthesis of metal coordination compounds bearing terpy ligands due to their different coordination topologies and their potential applications in photo-luminescence and antitumor activities. Previous studies on such terpyridine complexes have been published, including Pd(II), Pt(II), Zn(II) and Ag(I) (Bugarcic et al., 2004;Koo et al., 2003;Yam et al., 2003). We report here on the synthesis and the results of the crystal structure analysis of an adduct of zinc chloride with 4′-Ph-terpyridine.
The structure of the title compound, [ZnCl 2 (C 21 H 15 N 3 )], consists of a neutral molecular unit where the metal is pentacoordinate within a [ZnCl 2 L] (L = 4′-phenyl-2,2′:6′,2"-terpyridine) ( Fig. 1) coordination set. All bond lengths and angles are within normal ranges (Allen et al., 1987). The Zn 2+ cation is surrounded by the three nitrogen atoms of the ligand and two chloride anions, forming an irregular distorted trigonal-bipyramidal ZnN 3 Cl 2 polyhedron, whereby the two chloride ions occupy the axial positions and the three equatorial sites are occupied by the nitrogen atoms of L. The angles between the apical chloride ions and the three terpy nitrogen atoms range from 96.70 (4) -123.87 (4) °. The terpyridyl molecule is nearly planar (with an RMS deviations of 0.1029 Å), but the pendant phenyl ring is twisted and makes an angle of 26.55 (9) ° with the plane defined by N1, N2, N3 and Zn1.
No classic hydrogen bonding is observed, but three weak C-H···Cl hydrogen bonds are recognized (Table 2, Fig. 2).
In the title complex no solvent molecule is contained in the structure. However, two crystal structures of [ZnCl 2 L] with different solvents (water or dimethylformamide) were already reported (Tu et al., 2004;Ma, Cao et al., 2010).

Experimental
Free L was prepared by a reported procedure (Constable et al., 1990).
The title compound was synthesized by reaction of zinc(II) chloride, L and disodium 2,6-dipicolinate (Na 2 C 7 H 3 N 1 O 4 ) in the conditions as follows: ZnCl 2 .4H 2 O (0.021 g, 0.10 mM), L (0.031 g, 0.10 mM) were dissoved in a mixture of methanol and DMF (16 cm 3 , 1:1) and a aqueous solution of disodium 2,6-dipicolinate (5 cm 3 , 0.01 M/L) was added. The system was stirred for 48 h at 437 K and cooled down to room temperature. After filtration, a unknown solid and a colorless solution were obtained. Evaporation of the solution gave colorless crystals, which were isolated by mechanical separation from a mixture including an unidentified powder and were suitable for X-ray characterization. The yield of the compound is 16 % (7.3 mg) based on the ligand.

Refinement
Hydrogen atoms bonded to the ligands were positioned geometrically and refined using a riding model with C-H = 0.93 Å and with Uiso(H) = 1.2×Ueq(C). These hydrogen atoms were assigned isotropic thermal parameters and allowed to ride on their respective parent atoms.

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.