Synchrotron X-ray Charge-Density Study of Coordination Polymer [Mn(HCOO)2(H2O)2]

Coordination polymers (CP) provide a very attractive route for crystal engineering of functional materials.[1] Unlike porous zeolite frameworks, the structural identities of the reactants are preserved in the crystal, and the molecular assembly of CPs is reminiscent of building with Lego blocks. The structure of the compound is shown in Figure 1. It is composed of Mn-atoms linked by formate groups and water molecules. There are two distinct metal sites; Mn1 which is octahedrally coordinated to six formate bridges and Mn2 which is octahedrally coordinated to two formate bridges and four water molecules. This gives a layered structure where the Mn1 is cross linked in the bc-plane. The Mn2 sites link the Mn1-planes together via formate bridges. The compound crystallizes in space group p21/c with unit cell parameters of 8.8 Å, 7.2 Å, 9.6 Å and 97.6º. Figure 1: Structure of Manganese formate dihydrate at 16 K (Thermal ellipsoids shown at 50 % probability). In this study, we have collected three high quality x-ray diffraction data sets under very different conditions. The first is a conventional 100(2) K MoK data set, the second is a 100(2) K data set measured at D3, Hasylab and the third data set is measured at ChemMatCARS, APS at 16(2) K