J. Rodríguez-Hernández

1-Methyl-2-pyrrolidone: from exfoliating solvent to a paramagnetic ligand.

When 1-methyl-2-pyrrolidone molecule (1m2p) interacts with the T[Ni(CN)4] layer, its carbonyl π bond homolytically disrupts and forms a coordination bond at the axial positions for the metal T, and hybrid inorganic-organic solids of formula unit T(L)2[Ni(CN)4], with T = Mn, Co, Ni, are obtained. The formed solids crystallize with a monoclinic unit cell in the C2/m space group where the metal T is found with octahedral coordination to four N ends of CN groups from a given layer and to two oxygen atoms from the organic ligands, while the inner metal (Ni) preserves its square planar coordination. In the interlayer region, the organic molecules achieve unusual planarity and are stacked through dipole-dipole interactions in a head-to-tail configuration to form a chain of molecular pillars. From such interactions, 3D pillared hybrid solids result. Upon the charge donation to the metal by oxygen atom from 1m2p, the latter becomes an organic radical whose SOMO frontier orbital has a strong π character, associated with an essentially planar structure. The unpaired electron is delocalized between neighboring C and N atoms at the ligand ring plane, and it is featured by an outstanding broad absorption band in the near-IR region. For Ni, the metal of highest polarizing power within the considered series, the existence of π overlapping interaction between organic ligand molecules leads to ferromagnetic ordering at low temperature, with TC = 10.07 K. For Mn and Co, related to the lower metal electron-withdrawing ability, the materials maintain the weak antiferromagnetic character resulting from the interaction between T metals in the layer -T-N≡C-Ni-C≡N-T- chains.

Crystal structures of three anhydrous nitroprussides: M†Fe"CN…5NO ‡" M=Mn,Zn,Cd…

The crystal structures of Mn, Zn, and Cd nitroprussides in their anhydrous state, M Fe CN 5NO M=Mn,Zn,Cd , were refined from XRD powder patterns using the Rietveld method. These compounds have a porous framework useful for adsorption and storage of small molecules. Water crystallization can be removed by heating below 100 °C without disrupting the 3D network by introducing certain structural modification mainly around the M site Mn, Zn, Cd . For M=Mn and Cd, the compounds were found to be orthorhombic with space group Pnma Mn:a=13.7844 1 , b=7.3750 2 , c=10.9470 2 A, V=1112.8 1 A3, Z=4; Cd:a=13.9566 3 , b=7.5040 4 , c =11.0230 2 A, V=1154.4 1 A3, Z=4 . Anhydrous zinc nitroprusside crystallizes in rhombohedral with space group R3¯ a=b=19.2525 1 ,c=17.7107 2 A, =120.0° ,V=5685.1 1 A3 ,Z=18 . When exposed to humid air, these anhydrous compounds become hydrated. The XRD powder patterns were recorded under vacuum on samples dehydrated in situ. The structural information from XRD was complemented with thermo-gravimetric, infrared, and Mossbauer data.

Synthesis, characterization, and crystal structure of two zinc linear dicarboxylates

Two different crystalline structures corresponding to a zinc adipate and a zinc succinate were determined combining: X-ray powder and single-crystal diffraction, infrared spectroscopy, thermal analysis, and true densities experiments. The zinc succinate crystal structure was determined by single-crystal X-ray diffraction. This compound crystallizes in the orthorhombic space-group Cccm with unit-cell parameters a = 4.792(1) A, b = 21.204(6) A, c = 6.691(2) A, V = 679.8(3) A 3 , and Z = 8. Zinc adipate crystal structure was refined from the laboratory X-ray powder diffraction data by the Rietveld method. It crystallizes in the monoclinic space group P 2/ c with unit-cell parameters, a = 16.2037(17)A, b = 4.7810(2)A, c = 9.2692(6)A, β = 90.329(3)°, V = 718.07(9) A 3 , and Z = 4. The thermal expansion of it was estimated in 5.40 × 10 −5 K −1 . This contribution is a step on the way to systematize the regularities in the coordination diversity between linear dicarboxylates and transition metal–inorganic buildings units of metal–organic frameworks.