Arianna Lanza

Anagostic Interactions under Pressure: Attractive or Repulsive?

Square-planar d(8)-ML4 complexes might display subtle but noticeable local Lewis acidic sites in axial direction in the valence shell of the metal atom. These sites of local charge depletion provide the electronic prerequisites to establish weakly attractive 3c-2e M⋅⋅⋅H-C agostic interactions, in contrast to earlier assumptions. Furthermore, we show that the use of the sign of the (1)H NMR shifts as major criterion to classify M⋅⋅⋅H-C interactions as attractive (agostic) or repulsive (anagostic) can be dubious. We therefore suggest a new characterization method to probe the response of these M⋅⋅⋅H-C interactions under pressure by combined high pressure IR and diffraction studies.

Solid-State Reversible Nucleophilic Addition in a Highly Flexible MOF

A flexible and porous metal-organic framework, based on Co(II) connectors and benzotriazolide-5-carboxylato linkers, is shown to selectively react with guest molecules trapped in the channels during the sample preparation or after an exchange process. Stimulated by a small crystal shrinking, upon compression or cooling, the system undergoes a reversible, nonoxidative nucleophilic addition of the guest molecules to the metal ion. With dimethylformamide, only part of the penta-coordinated Co atoms transform into hexa-coordinated, whereas with the smaller methanol all of them stepwise increase their coordination, preserving the crystallinity of the solid at all stages. This extraordinary example of chemisorption has enormous implications for catalysis, storage, or selective sieving.

Manganoblödite, Na2Mn(SO4)2·4H2O, and cobaltoblödite, Na2Co(SO4)2·4H2O: two new members of the blödite group from the Blue Lizard mine, San Juan County, Utah, USA

Abstract Two new minerals - manganoblödite (IMA2012-029), ideally Na2Mn(SO4)2·4H2O, and cobaltoblödite (IMA2012-059), ideally Na2Co(SO4)2·4H2O, the Mn-dominant and Co-dominant analogues of blödite, respectively, were found at the Blue Lizard mine, San Juan County, Utah, USA. They are closely associated with blödite (Mn-Co-Ni-bearing), chalcanthite, gypsum, sideronatrite, johannite, quartz and feldspar. Both new minerals occur as aggregates of anhedral grains up to 60 μm (manganoblödite) and 200 μm (cobaltoblödite) forming thin crusts covering areas up to 2 × 2 cm on the surface of other sulfates. Both new species often occur as intimate intergrowths with each other and also with Mn-Co-Ni-bearing blödite. Manganoblödite and cobaltoblödite are transparent, colourless in single grains and reddish-pink in aggregates and crusts, with a white streak and vitreous lustre. Their Mohs‘ hardness is ~2½. They are brittle, have uneven fracture and no obvious parting or cleavage. The measured and calculated densities are Dmeas = 2.25(2) g cm−3 and Dcalc = 2.338 g cm−3 for manganoblödite and Dmeas = 2.29(2) g cm−3 and Dcalc = 2.347 g cm−3 for cobaltoblödite. Optically both species are biaxial negative. The mean refractive indices are α = 1.493(2), β = 1.498(2) and γ = 1.501(2) for manganoblödite and α = 1.498(2), β = 1.503(2) and γ = 1.505(2) for cobaltoblödite. The chemical composition of manganoblödite (wt.%, electron-microprobe data) is: Na2O 16.94, MgO 3.29, MnO 8.80, CoO 2.96, NiO 1.34, SO3 45.39, H2O (calc.) 20.14, total 98.86. The empirical formula, calculated on the basis of 12 O a.p.f.u., is: Na1.96(Mn0.44Mg0.29Co0.14Ni0.06)Σ0.93S2.03O8·4H2O. The chemical composition of cobaltoblödite (wt.%, electron-microprobe data) is: Na2O 17.00, MgO 3.42, MnO 3.38, CoO 7.52, NiO 2.53, SO3 45.41, H2O (calc.) 20.20, total 99.46. The empirical formula, calculated on the basis of 12 O a.p.f.u., is: Na1.96(Co0.36Mg0.30Mn0.17Ni0.12)Σ 0.95S2.02O8·4H2O. Both minerals are monoclinic, space group P21/a, with a = 11.137(2), b = 8.279(1), c = 5.5381(9) Å, β = 100.42(1)°, V = 502.20(14) Å3 and Z = 2 (manganoblödite); and a = 11.147(1), b = 8.268(1), C = 5.5396(7) Å, β = 100.517(11)°, V = 501.97(10) Å3 and Z = 2 (cobaltoblödite). The strongest diffractions from X-ray powder pattern [listed as (d,Å(I)(hkl)] are for manganoblödite: 4.556(70)(210, 011); 4.266(45)(2̅01); 3.791(26)(2̅11); 3.338(21)(310); 3.291(100)(220, 021), 3.256(67)(211,1̅21), 2.968(22)(2̅21), 2.647(24)(4̅01); for cobaltoblödite: 4.551(80)(210, 011); 4.269(50)(2̅01); 3.795(18)(2̅11); 3.339(43)(310); 3.29(100)(220, 021), 3.258(58)(211, 1̅21), 2.644(21)( 4̅01), 2.296(22)( 1̅22). The crystal structures of both minerals were refined by single-crystal X-ray diffraction to R1 = 0.0459 (manganoblödite) and R1 = 0.0339 (cobaltoblödite).

Experimental and Theoretical Electron Density Analysis of Copper Pyrazine Nitrate Quasi-Low-Dimensional Quantum Magnets

The accurate electron density distribution and magnetic properties of two metal-organic polymeric magnets, the quasi-one-dimensional (1D) Cu(pyz)(NO3)2 and the quasi-two-dimensional (2D) [Cu(pyz)2(NO3)]NO3·H2O, have been investigated by high-resolution single-crystal X-ray diffraction and density functional theory calculations on the whole periodic systems and on selected fragments. Topological analyses, based on quantum theory of atoms in molecules, enabled the characterization of possible magnetic exchange pathways and the establishment of relationships between the electron (charge and spin) densities and the exchange-coupling constants. In both compounds, the experimentally observed antiferromagnetic coupling can be quantitatively explained by the Cu-Cu superexchange pathway mediated by the pyrazine bridging ligands, via a σ-type interaction. From topological analyses of experimental charge-density data, we show for the first time that the pyrazine tilt angle does not play a role in determining the strength of the magnetic interaction. Taken in combination with molecular orbital analysis and spin density calculations, we find a synergistic relationship between spin delocalization and spin polarization mechanisms and that both determine the bulk magnetic behavior of these Cu(II)-pyz coordination polymers.

Quasi-2D Heisenberg Antiferromagnets [CuX(pyz)2](BF4) with X = Cl and Br

Two Cu2+ coordination polymers [CuCl(pyz)2](BF4) 1 and [CuBr(pyz)2](BF4) 2 (pyz = pyrazine) were synthesized in the family of quasi two-dimensional (2D) [Cu(pyz)2]2+ magnetic networks. The layer connectivity by monatomic halide ligands results in significantly shorter interlayer distances. Structures were determined by single-crystal X-ray diffraction. Temperature-dependent X-ray diffraction of 1 revealed rigid [Cu(pyz)2]2+ layers that do not expand between 5 K and room temperature, whereas the expansion along the c-axis amounts to 2%. The magnetic susceptibility of 1 and 2 shows a broad maximum at ∼8 K, indicating antiferromagnetic interactions within the [Cu(pyz)2]2+ layers. 2D Heisenberg model fits result in J∥ = 9.4(1) K for 1 and 8.9(1) K for 2. The interlayer coupling is much weaker with | J⊥| = 0.31(6) K for 1 and 0.52(9) K for 2. The electron density, experimentally determined and calculated by density functional theory, confirms the location of the singly occupied orbital (the magnetic orbital) in the tetragonal plane. The analysis of the spin density reveals a mainly σ-type exchange through pyrazine. Kinks in the magnetic susceptibility indicate the onset of long-range three-dimensional magnetic order below 4 K. The magnetic structures were determined by neutron diffraction. Magnetic Bragg peaks occur below TN = 3.9(1) K for 1 and 3.8(1) K for 2. The magnetic unit cell is doubled along the c-axis ( k = 0, 0, 0.5). The ordered magnetic moments are located in the tetragonal plane and amount to 0.76(8) μB/Cu2+ for 1 and 0.6(1) μB/Cu2+ for 2 at 1.5 K. The moments are coupled antiferromagnetically both in the ab plane and along the c-axis. The Cu2+ g-tensor was determined from electron spin resonance spectra as g x = 2.060(1), g z = 2.275(1) for 1 and g x = 2.057(1), g z = 2.272(1) for 2 at room temperature.

The benefits of one‐dimensional detectors for high‐pressure powder X‐ray diffraction

High-pressure powder X-ray diffraction is a fundamental technique for investigating structural responses to externally applied force. Synchrotron sources and two-dimensional detectors are required. In contrast to this conventional setup, high-resolution beamlines equipped with one-dimensional detectors could offer much better resolved peaks but cannot deliver accurate structure factors because they only sample a small portion of the Debye rings, which are usually inhomogeneous and spotty because of the small amount of sample. In this study, a simple method to overcome this problem is presented and successfully applied to solving the structure of an L-serine polymorph from powder data. A comparison of the obtained high-resolution high-pressure data with conventional data shows that this technique, providing up to ten times better angular resolution, can be of advantage for indexing, for lattice parameter refinement, and even for structure refinement and solution in special cases.

Deveroite-(Ce): a new REE-oxalate from Mount Cervandone, Devero Valley, Western-Central Alps, Italy

Abstract Deveroite-(Ce), ideally Ce2(C2O4)3·10H2O, is a new mineral (IMA 2013-003) found in the alpine fissures of Mount Cervandone, overlooking the Devero Valley, Piedmont, Italy. It occurs as sprays of colourless elongated tabular, acicular prisms only on cervandonite-(Ce). It has a white streak, a vitreous lustre, is not fluorescent and has a hardness of 2-2.5 (Mohs’ scale). The tenacity is brittle and the crystals have a perfect cleavage along {010}. The calculated density is 2.352 g/cm3. Deveroite-(Ce) is biaxial (-) with 2V of ~77º, is not pleochroic and the extinction angle (β ^ c) is ~27º. No twinning was observed. Electron microprobe analyses gave the following chemical formula: (Ce1.01Nd0.33La0.32Pr0.11Y0.11Sm0.01Pb0.04U0.03Th0.01Ca0.04)2.01(C2O4)2.99·9.99H2O. Although synchrotron radiation was not used to solve the structure of deveroite-(Ce) the extremely small size of the sample (13 μm × 3 μm× 1 μm) did not allow us to obtain reliable structural data. However, it was possible to determine the space group (monoclinic, P21/c) and the unit-cell parameters, which are: a = 11.240(8) Å, b = 9.635(11) Å, c = 10.339(12) Å, β = 114.41(10)º, V = 1019.6 Å3. The strongest lines in the powder diffraction pattern [d in Å (I)(hkl)] are: 10.266(100)(100); 4.816(35.26)(211̄); 3.415(27.83)(300); 5.125(24.70)(200); and 4.988(22.98)(111). Deveroite-(Ce) is named in recognition of Devero valley and Devero Natural Park.

First crystal-structure determination of natural lansfordite, MgCO3·5H2O

Abstract This study presents the first crystal-structure determination of natural MgCO3·5H2O, mineral lansfordite, in comparison with previous structural works performed on synthetic analogues. A new prototype singlecrystal X-ray diffractometer allowed us to measure an extremely small crystal (i.e. 0.020 mm × 0.010 mm × 0.005 mm) and refine anisotropically all non-hydrogen atoms in the structure and provide a robust hydrogen-bond arrangement. Our new data confirm that natural lansfordite can be stable for several months at room temperature, in contrast with previous works, which reported that such a mineral could be stable only below 10°C.

Ghiaraite: a new mineral from Vesuvius volcano, Naples (Italy)

Abstract In this work we report the first finding of CaCl2β·4H2O, long known as a synthetic phase. The mineral, called ghiaraite, was discovered in 2011 in a sample belonging to the Real Museo Mineralogico di Napoli (Italy), that had been collected in 1872 at Vesuvius volcano and stored in a glass sealed vial. It is associated with chlorocalcite (KCaCl3), hematite, sylvite, and halite. The mineral was found inside an ejecta of 5 m in size transported by a lava flow to the locality of Massa di Somma. Here with the ejecta still hot the sample was collected and rapidly stored in a sealed glass vial to preserve it from the atmospheric conditions. Ghiaraite is triclinic, space group P1̄, with unit-cell parameters: a = 6.3660(5), b = 6.5914(5), c = 8.5568(6) Å, α = 93.504(6)°, β = 97.778(7)°, γ = 110.557(6)°, V = 330.802(9) Å3, Z = 2. The calculated density is 1.838 g/cm3 using the ideal formula and the powder X-ray diffraction data. It occurs as euhedral isometric grains up to 5-6 μm long intimately intermixed with chlorocalcite. The eight strongest reflections in the X-ray powder diffraction pattern [listed as d(Å)(I)(hkl)] are: 2.628(100)(022̄̄̄); 2.717(88)(103̄); 4.600(88)(11̄ 1̄); 2.939(77)(200); 2.204(75)(121), 5.874(73)(100), 6.124(47)(010); 3.569(46)(111̄). Ghiaraite was approved by the Commission on New Minerals, Nomenclature and Classification with IMA number 2012-072. The mineral was named in honor of Maria Rosaria Ghiara (b. 1948), Head of Real Museo Mineralogico of Napoli and Centro Musei delle Scienze Naturali e Fisiche dell’Università degli Studi di Napoli Federico II for her important work in promoting the scientific research focused on the mineralogy of Vesuvius volcano.

Binding guest molecules to frameworks: pressure-induced chemisorption in breathing MOFs

Arianna Lanza1, Luzia Germann2, Martin Fisch3, Nicola Casati4, Piero Macchi5 1Italian Institute Of Technology, Pisa, Italy, 2Max-Planck Institute for Solid State Research, Stuttgart, Germany, 3University of Bern, Bern, Switzerland, 4Swiss Light Source, Paul Scherrer Institute, Villigen, Switzerland, 5Department of Chemistry and Biochemistry, University of Bern, Bern, Switzerland E-mail: ari.streghetta@gmail.com