A monoclinic pseudopolymorph of manganese squarate dihydrate, Mn(μ-C4O4)(H2O)2, built from cubic units

The structure of poly[[[hexaaquatrimanganese(II)]-tri-mu-squarato] monohydrate], {[Mn(3)(C(4)O(4))(3)(H(2)O)(6)].H(2)O}(n), synthesized hydrothermally, consists of a new three-dimensional framework described by secondary building units (SBUs) containing two MnO(6) octahedra and three squarate groups in a cube-shaped arrangement. In the asymmetric unit, one squarate group is located around an inversion centre (4a; 0, 0, 0), two Mn atoms [4d (3/4, 1/4, 0) and 4c (1/4, 1/4, 0)] are located on inversion centres and the third Mn atom is on a twofold axis (4e; 0, y, 1/4). This report illustrates the concept of the SBU and the flexibility of the squarate spacer in the design of new porous topologies.