The title complex, [Mg(C7H7N4O2)2(H2O)4], lies across an inversion centre and the Mg(II) atom is coordinated in a slightly distorted octa-hedral environment by four aqua ligands in the equatorial sites and two 1,3-dimethyl-2,6-dioxo-3,7-di-hydro-1H-purin-9-ide ligands, through imidazole ring N atoms, in the axial sites. An intra-molecular O-H⋯O hydrogen bond forms an S(7) graph-set motif. In the crystal, O-H⋯O and O-H⋯N hydrogen bonds link complex mol-ecules forming a three-dimensional network incorporating R 4 (2)(8) and R 2 (2)(18) graph-set motifs.
Keywords: crystal structure; hydrogen bonding; tetraaqua mononuclear MgII complex; theophylline.