catena-Poly[[[(pyridine-κN)copper(II)]-μ-3-{1-[(2-aminoethyl)imino]ethyl}-6-methyl-2-oxo-2H-pyran-4-olato-κ4 N,N,O 4:O 2] perchlorate]

In the title compound, {[Cu(C10H13N2O3)(C5H5N)]ClO4}n, the CuII atom has an N3O2 coordination sphere. The complex contains two different ligands, viz. a pyridine molecule and a Schiff base molecule, resulting from the condensation of ethylenodiamine with dehydroacetic acid. The CuII atom exhibits a square-pyramidal geometry: three of the four donors of the pyramid base belong to the Schiff base ligand (an N atom from the amine group, a second N atom from the imine group and the O atom of the pyranone residue) and the fourth donor is the pyridine N atom. The coordination around the metal ion is completed by a longer axial bond to the pyranone O atom of an adjacent Schiff base, so forming a one-dimensional polymer. The complex has a +1 charge that is compensated by a perchlorate ion. The crystal packing, which can be described as alternating chains of cations and tetrahedral perchlorate anions along the a axis, is stabilized by intermolecular N—H⋯O, C—H⋯O and C—H⋯N hydrogen-bonding interactions.

In the title compound, {[Cu(C 10 H 13 N 2 O 3 )(C 5 H 5 N)]ClO 4 } n , the Cu II atom has an N 3 O 2 coordination sphere. The complex contains two different ligands, viz. a pyridine molecule and a Schiff base molecule, resulting from the condensation of ethylenodiamine with dehydroacetic acid. The Cu II atom exhibits a square-pyramidal geometry: three of the four donors of the pyramid base belong to the Schiff base ligand (an N atom from the amine group, a second N atom from the imine group and the O atom of the pyranone residue) and the fourth donor is the pyridine N atom. The coordination around the metal ion is completed by a longer axial bond to the pyranone O atom of an adjacent Schiff base, so forming a onedimensional polymer. The complex has a +1 charge that is compensated by a perchlorate ion. The crystal packing, which can be described as alternating chains of cations and tetrahedral perchlorate anions along the a axis, is stabilized by intermolecular N-HÁ Á ÁO, C-HÁ Á ÁO and C-HÁ Á ÁN hydrogen-bonding interactions.

Comment
The dehydroacetic acid is a row material which is involved in the synthesis of the most heterocyclic compounds (El-Abbassi et al., 1987;Fettouhi et al., 1996;El-Kihel et al., 1999) and the chelating agents such as the Schiff bases. These ligands are also currently applied in coordination chemistry for the synthesis of Schiff base complexes of transition metals (Tan et al., 1988;El-Kubaisi et al., 1994;Munde et al., 2010). Additionally, it was often shown that the heterocyclic compounds resulting from this molecule exhibit some therapeutic activities (Das et al., 1976;Mohan et al., 1981;Maiti et al., 1988) useful for the human diseases while the Schiff base complexes obtained from its ligands showed an important catalytic activity particularly in the oxidation reactions as those carried out according the cytochrome P450 model (Moutet et al., 1997;Ourari et al., 2008). Thus, we have attempted to synthesize the Schiff base half-units in order to use them as starting materials to obtain unsymmetrical tetradentate Schiff base complexes according the Danilova method's (Danilova et al., 2003). So, we describe here the formation of a new copper Schiff base complex from dehydroacetic acid, ethylenediamine, copper perchlorate and pyridine in methanolic solution. This complex was formed in one pot with only one azomethine (-CH=N-) group yielding an unreacted amino group of ethylenediamine leading to an acceptable yield 68%. In this case, it can noted that the ring of the dehydroacetic acid seems to be not open during the reaction as it was reported in the literature (Djerrari et al., 2002) in presence of nucleophile agents such as the pyridinic derivatives. This behavior may be due to an inhibition of the nucleophilic effect of the pyridine since the reaction was conducted in methanolic solution at room temperature and without reflux. Finally, the resulting compound was confirmed by crystallographic studies as further discussed.
The asymetric unit of ionic structure of (I), and the atomic numbering used, is illustrated in Fig. 1. The Cu II ion is five coordinated in a square-pyramidal geometry by three N atoms of pyridine,imine and amine group and two O atom of pyranone moiety. The bond lengths for co-ordination Cu II sphere is ranging from 1.974 (2) to 2.049 (2) Å for Cu-N distances and Cu-O = 1.914 (2) Å and 1.914 (2) Å ( Table 2).
The crystal packing in the title structure can be described by alterning chains of cations and tetrahedral anions of perchlorate along the c axis (Fig. 2). It is stabilized by intermolecular N-H···O, C-H···O and C-H···N hydrogen bonding (Table 1). These interactions link the molecules within the layers and also link the layers together and reinforcing the cohesion of the ionic structure.

Experimental
This complex was obtained by mixing stoechiometric quantities of dehydroacetic acid 0.168 g (1 mMol) with copper perchlorate 0.373 g (1 mMol) in methanol. To this mixture was added an excess of pyridine and then 0.060 g (1 mMol) of ethylenediamine dissolved as well in methanol. After two hours of reaction, a mallow precipitate was observed which is immediately recovered by filtration. It was copiously washed with methanol. Its suitable single-crystal was so obtained by slow evaporation from the filtrate.

Refinement
The remaining H atoms were localized on Fourier maps but introduced in calculated positions and treated as riding on their parent atoms (C and N) with C-H = 0.96 Å (methyl), 0.97Å (methylene) or 0.93 Å (aromatic) and N-H = 0.90 Å with U iso (H) = 1.2U eq (C and N) or U iso (H) = 1.5U eq (methyl).