catena-Poly[[[diaqua­cobalt(II)]-μ-(3,5-dinitro-2-oxidobenzoato)-κ(3) O (1),O (2):O (1′)-[tetra­aqua­cobalt(II)]-μ-(3,5-dinitro-2-oxidobenzoato)-κ(3) O (1):O (1′),O (2)] dihydrate]

In polymeric title compound, {[Co(2)(C(7)H(2)N(2)O(7))(2)(H(2)O)(6)]·2H(2)O}(n), obtained from the reaction of 3,5-dinitro­salicylic acid with cobalt(II) acetate, both Co(II) atoms are located on inversion centres and exhibit a distorted octahedral coordination geometry. The coordin­ation sphere about one Co(II) atom comprises four O-atom donors from two bidentate chelate (O(phenolate) and O(carbox­yl)) and bridging dianionic ligands and two water mol­ecules [Co—O range = 2.0249 (11)–2.1386 (14) Å], while that about the second Co(II) atom has four water mol­ecules and two bridging carboxyl­ate O-donor atoms [Co—O range = 2.0690 (14)–2.1364 (11) Å]. The coordinated water mol­ecules as well as the water mol­ecules of solvation give O—H⋯O water–water and water–carboxyl hydrogen-bonding inter­actions in the three-dimensional framework structure.