catena-Poly[[tetra-aqua-cobalt(II)]-µ-2,2'-dihydroxy-5,5'-diazenediyldibenzoato].

In the title compound, [Co(C(14)H(8)N(2)O(6))(H(2)O)(4)](n), each 5,5'-diazenediylbis(2-hydroxy-benzoato) ligand acts as a dicarboxyl-ate bridge, leading to the formation of polymeric chains running in the [10] direction. The Co atom is hexa-coordinated in a distorted octa-hedral geometry by six O atoms [Co-O = 2.039 (4)-2.115 (4) Å] from two ligands and four water mol-ecules. Inter-molecular O-H⋯O and O-H⋯N hydrogen bonds build up a three-dimensional supra-molecular structure.

2,2'-Dihydroxy-3,3'-[(1E,1'E)-hydrazine-1,2-diylidenedimethylidyne]dibenzoic acid N,N-dimethylformamide disolvate.

The title compound, C(16)H(12)N(2)O(6)·2C(3)H(7)NO, lies across a crystallographic inversion centre which is situated at the midpoint of the central N-N bond. The substitution at the C=N bond adopts a trans configuration and it is essentially coplanar with the benzene ring [N-C-C-C torsion angles = -173.9 (4) and 6.4 (6)°]. All torsion angles involving non-H atoms are close to 180°. Intra-molecular O-H⋯O and weak C-H⋯O hydrogen bonds form S(6) and S(5) ring motifs, respectively, while inter-molecular O-H⋯O and weak C-H⋯O hydrogen bonds connect the Schiff base mol-ecule to solvent dimethyl-formamide mol-ecules.