Tetraaqua(1,10-phenanthroline)cobalt(II) naphthalene-1,5-disulfonate dihydrate.

The title complex, [Co(C12H8N2)(H2O)4](C10H6O6S2)·2H2O, was synthesized hydrothermally. The Co2+ cation, which lies on a twofold rotation axis, is six-coordinate. The anion is located on a centre of inversion. An extensive network of O—H⋯O hydrogen bonds links the components into a threedimensional network. [ABSTRACT FROM AUTHOR]