Poly[bis{μ-N′-[(pyridin-4-yl)methylidene]benzohydrazidato}copper(II)]

In the title complex, [Cu(C13H10N3O)2]n, the copper(II) cation is located on a crystallographic inversion centre and adopts an elongated octahedral coordination geometry with the equatorial plane provided by trans-arranged bis-N,O-chelating acylhydrazine groups from two ligands and the apices by the N atoms of two pyridine rings belonging to symmetry-related ligands. The ligand adopts a Z conformation about the C=N double bond. The dihedral angle between the pyridine and phenyl rings is 2.99 (13)°. An intraligand C—H⋯N hydrogen bond is observed. In the crystal, each ligand bridges two adjacent metal ions, forming a (4,4) grid layered structure. π–π stacking interactions [centroid–centroid distances in the range 3.569 (4)–3.584 (9) Å] involving rings of adjacent layers result in the formation of a three-dimensional supramolecular network.

In the title complex, [Cu(C 13 H 10 N 3 O) 2 ] n , the copper(II) cation is located on a crystallographic inversion centre and adopts an elongated octahedral coordination geometry with the equatorial plane provided by trans-arranged bis-N,O-chelating acylhydrazine groups from two ligands and the apices by the N atoms of two pyridine rings belonging to symmetry-related ligands. The ligand adopts a Z conformation about the C N double bond. The dihedral angle between the pyridine and phenyl rings is 2.99 (13) . An intraligand C-HÁ Á ÁN hydrogen bond is observed. In the crystal, each ligand bridges two adjacent metal ions, forming a (4,4) grid layered structure.stacking interactions [centroid-centroid distances in the range 3.569 (4)-3.584 (9) Å ] involving rings of adjacent layers result in the formation of a three-dimensional supramolecular network.

Poly[bis{µ-N′-[(pyridin-4-yl)methylidene]benzohydrazidato}copper(II)]
Qiong Wu, Da-Chi Chen, Chu-Yi Wu, Chang-Xiu Yan and Jian-Zhen Liao Comment Schiff bases and their metal compounds were widely synthesized in recent years and characterized for their wide range of applications as biocides and homogeneous catalysts in industry (Schurig et al., 1980;Siddall et al., 1983;Maurya et al., 2005). In previous reports, most of the Schiff base coordination compounds were oligomers such as zero-dimensional complexes with catalytic (Cozzi, 2004) or magnetic properties (Liu, et al., 2010). In this paper, the structure of a new two-dimensional polymeric copper(II) coordination compound is reported.
The asymmetric unit of the title complex contains one copper(II) ion located on an inversion centre and one deprotonated N′-(pyridin-4-ylmethyl) benzohydrazide ligand. The metal ion adopts a significantly elongated octahedral coordination geometry provided by four ligands (Fig. 1). The equatorial plane is occupied by two trans-arranged bis-N,O-chelating acylhydrazine groups from two ligands, while the axial positions are occupied by two N atoms of pyridine rings from other two ligands. In the equatorial plane, the Cu-O and Cu-N bond lengths are 1.942 (6) Å and 2.004 (4) Å, respectively, which are similar to those reported in the literature for related compounds (Yin 2008;Uçar et al., 2004;Sommerer et al., 1998). The apical Cu-N distances (2.578 (8) Å) are slightly longer than a common stretched Cu-N distance (Moya-Hernández et al., 2003), generating an elongated octahedral coordination geometry typically attributed to the Jahn-Teller effect. The ligand is approximately planar (maximum deviation from the least square plane is 0.0473 (13) Å for atom O1) and chelates to the copper atom to form a five-numbered ring (Cu1/O1/C7/N1/N2). The dihedral angle formed by the pyridine and phenyl rings is 2.99 (13)°. An intraligand C-H···N hydrogen bond is present (Table 1). In the crystal, each ligand bridges two adjacent metal ions (Fig. 2), meanwhile each copper atom is coordinated with four ligands to form a (4, 4) grid layered structure. Adjacent layers are further connected via π···π stacking interactions between benzene rings [Cg1···Cg1 i =3.584 (9) Å; Cg1 is the centroid of the C1-C6 ring; symmetry code: (i) -1/2 -x, 1/2y, -z] and benzene and pyridine ring [Cg1···Cg2 ii = 3.569 (4) Å; Cg2 is the centroid of the N1/C9-C13 ring; symmetry code: (ii) -x, -y, -z], forming a three-dimensional supramolecular structure (Fig. 3).

Experimental
A mixture of N′-(pyridin-4-ylmethyl)benzohydrazide (0.045 g, 0.02 mmol), Cu(CH 3 COO) 2 .4H 2 O (0.026 g, 0.01 mmol) in ethanol (6 mL) was stirred for 40 minutes and then heated in a 25 mL Teflon-lined autoclave at 100°C for 3 days, followed by cooling to room temperature. The resulting mixture was washed with water, and brown crystals were collected and dried in air. Yield: 40% (based on Cu).

Refinement
All H atoms were placed in idealized positions using a riding-model approximation, with C-H = 0.95 Å and U iso (H) = 1.2U eq (C).

Figure 1
The molecular structure of the title compound with displacement ellipsoids drawn at the 30% probability level. H atoms are omitted for clarity. Symmetry codes: (i) 0.5 -x, 0.5 -y, -z; (ii) 0.5 -x, 0.5 + y, 0.5 -z; (iii) x, -y, -0.5 + z.    Packing diagram of the title compound, showing the π-π stacking interactions between phenyl rings (green dashed lines) or between phenyl and pyridine rings (red dashed lines). H atoms are omitted for clarity.

Poly[bis{µ-N′-[(pyridin-4-yl)methylidene]benzohydrazidato}copper(II)]
Crystal data [Cu(C 13  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 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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq