Poly[[diaquabis(μ(2)-4,4'-bipyridyl)iron(II)] bis{2-[(3-carboxypyridin-2-yl)disulfanyl]nicotinate}].

In the title compound, {[Fe(C(10)H(8)N(2))(2)(H(2)O)(2)](C(12)H(7)N(2)O(4)S(2))(2)}(n), synthesized by hydro-thermal reaction, the 4,4'-bipyridyl ligands (one with symmetry 2, one with symmetry [Formula: see text]) connect Fe(2+) cations, forming a cationic layer parallel to (001). The coordination of the Fe(2+) cation (site symmetry 2) is octahedral, with four N atoms from four 4,4'-bipyridyl ligands and O atoms from two trans water molecules. Adjacent layers are linked with each other by inter-molecular O-H⋯O hydrogen bonds, forming a three-dimensional supra-molecular structure. Parts of the nicotinic acid derivative are equally disordered over two sets of sites.