Poly[propane-1,3-diammonium [cuprate(II)-bis(μ2-pyridine-2,3-dicarboxylato)] trihydrate]

The title polymeric compound {(C3H12N2)[Cu(C7H3NO4)2]·3H2O}n or {(pnH2)[Cu(py-2,3-dc)2]·3H2O}n (pn is propane-1,3-diamine and py-2,3-dcH2 is pyridine-2,3-dicarboxylic acid), was synthesized by reaction of copper(II) chloride dihydrate with a proton-transfer compound, propane-1,3-diammonium pyridine-2,3-dicarboxylate or (pnH2)(py-2,3-dc), in aqueous solution. The anion is a six-coordinate complex (site symmetry ), with a distorted octahedral geometry around CuII, consisting of two bidentate pyridine-2,3-dicarboxylate groups and two O atoms of bridging ligands from (py-2,3-dc)2− fragments, which are located in trans positions. The (pnH2)2+ cation is disordered over two sites by the center of inversion. Intermolecular hydrogen bonds, π–π [centroid–centroid distances of 3.539 (3) Å] and C—O⋯π stacking interactions [O⋯Cg = 3.240 (5) Å; Cg is the center of the pyridine ring], connect the various components into a supramolecular structure.

Financial support from Ilam University and the Teacher Training University is gratefully acknowledged. Intermolecular intractions, such as hydrogen bonding, π-π stacking, ion pairing and donor-acceptor interactions, are famous for making aggregates of molecules. One or more of these interactions may result in the formation of specific and spontaneous self-associations or self-associated compounds. Research has shown that hydrogen bonding plays the key role in preparation of self-assembled compounds.There is a very close relationship between hydrogen bonding and formation of proton transfer compounds Aghabozorg, Daneshvar et al., 2007).
Intermolecular O-H···O, O-H···N, N-H···O, C-H···O and C-H···N hydrogen bonds with D···A ranging from 2.283 (1) Å to 3.534 (13) Å (Table 2) seem to be effective in the stabilization of the crystal structure, resulting in the formation of an interesting supramolecular structure.

S2. Experimental
A solution of CuCl 2 .2H 2 O (85 mg, 0.5 mmol) in water (5 ml) was added to an aqueous solution of (pnH 2 )(py-2,3-dc) (242 mg, 1 mmol) in water (10 ml) in a 1:2 molar ratio. Blue crystals of title compound were obtained after allowing the mixture to stand for four weeks at room temperature.

S3. Refinement
The H(C) atom positions were calculated. H(N) and H(O) atom positions were found in difference Fourier synthesis. All hydrogen atoms were refined with use of a riding model with the U iso (H) parameters equal to 1.2 U eq (C) and to 1.5 U eq (N), 1.5 U eq (O), where U(C), U eq (O) and U(N) are equivalent isotropic thermal parameters of the atoms to which corresponding H atoms are bonded.
The cation is disordered over two sites by a center of inversion.
Water molecules are disordered over two sites: O1WA and O1WB with equal occupancies and O2W by the center of inversion.

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