catena-Poly[[tri-aqua-copper(II)]-µ-5-carb-oxy-benzene-1,3-di-carboxyl-ato-κ(2) O (1):O (3)].

In the title complex, [Cu(C9H4O6)(H2O)3] n , the Cu(II) cation exhibits a distorted square-pyramidal coordination geometry involving five O atoms from two monodentate 5-carb-oxy-benzene-1,3-di-carboxyl-ate anions and three water mol-ecules. The 5-carb-oxy-benzene-1,3-di-carboxyl-ate anions bridge Cu(II) cations into zigzag polymeric chains running along the b-axis direction. These chains are further linked by O-H⋯O hydrogen bonds between coordinating water mol-ecules or carboxyl groups and carboxylate groups into a three-dimensional supra-molecular architecture. In the crystal, π-π stacking is observed between parallel benzene rings of adjacent chains, the centroid-centroid distances being 3.584 (3) and 3.684 (3) Å.

Poly[di-µ9-citrato-tetra-sodiumzinc].

In the title compound, [Na4Zn(C6H5O7)2] n , the Zn(II) ion lies on an inversion center and is coordinated by six O atoms from two citrate ligands, forming a distorted octa-hedral geometry. There are two crystallographically independent Na(+) cations in the asymmetric unit. One Na(+) cation exhibits a distorted square-pyramidal geometry defined by five O atoms from four citrate ligands. The other Na(+) cation is surrounded by six O atoms from five citrate ligands in a distorted octa-hedral geometry. The Na(+) cations are bridged by citrate carboxyl-ate groups, forming a layer parallel to (100). The layers are further assembled into a three-dimensional network with the [Zn(citrate)2](4-) building units as 'pillars'; O-H⋯O hydrogen bonds also stabilize the structure.