Diaquabis(2,5-dihydroxybenzoato-kappaO)bis(1,10-phenanthroline-kappa2N,N')strontium(II) bis(1,10-phenanthroline) tetrahydrate.

The title compound, [Sr(C(7)H(5)O(4))(2)(C(12)H(8)N(2))(2)(H(2)O)(2)].2C(12)H(8)N(2).4H(2)O, consists of an Sr(II) complex, uncoordinated phenanthroline (phen) molecules and solvent water molecules. The Sr(II) ion is located on a twofold axis and is coordinated by two phen ligands, two dihydroxybenzoate anions and two water molecules in a distorted tetragonal antiprismatic geometry. Partially overlapped arrangements exist between parallel coordinated and parallel uncoordinated phen rings; the face-to-face separations between the former (coordinated) and the latter (uncoordinated) rings are 3.436 (13) and 3.550 (14) A, respectively. This difference suggests the effect of metal coordination on pi-pi stacking between phen rings.