Synthesis, X-ray crystal structure and spin polarized DFT study of high spin Mn based metal-organic framework

Theoretical modeling of the geometries of metal-organic frameworks is quite challenging. In order to compare the geometry obtained through density functional theory (DFT) calculations with the one obtained experimentally, a hydrothermal reaction of the potassium salt of 1,1-cyclopentane diacetic acid (L) with MnCl2·2H2O in the presence of 4,4′-bipyridine (bpy) was carried out which formulated a two dimensional metal-organic framework [Mn2(L)2(bpy)2(H2O)2]n∙6H2O. Single crystal X-ray diffraction analysis reveals that the compound crystallized in the centrosymmetric monoclinic space group P 2/n. The presence of solvate water molecules of crystallization offer hydrogen bond formation and result the connection of 2-D sheets into 3-D hydrogen bonded metal-organic framework. The manganese atom can have a maximum of sextet spin state (five unpaired electrons). Single point energies were calculated at M05-2X/6-31G (d,p) for different spin states (up to 11 et) of the high energy framework and it was elucidated that the 11et spin stat is the lowest energy spin state.