Cold-region ecosystems are highly sensitive to climate change, yet the geochemical processes shaping their future remain poorly understood. Here, we show that ice systematically enhances mineral dissolution through freeze concentration into microscale reactive hot spots. Using goethite nanoparticles as a model iron oxide and environmentally relevant inorganic anions common in soils, waters, and aerosols (chloride, fluoride, sulfate), we demonstrate that ligand-promoted dissolution rates under mildly acidic conditions scale with binding affinity in both ice and liquid water, with ice enhancing rates across all reactive ligands. Fluoride, the strongest complexing agent, increased dissolution more than fourfold in ice, while weakly binding perchlorate produced no measurable dissolution in either phase. Reactions persisted well below the eutectic temperature, mediated by minute volumes of liquid-like water stabilized within networks of micron-sized mineral aggregates. Our findings highlight ice as a dynamic medium driving iron release, with implications for nutrient availability, carbon cycling, and biogeochemical feedbacks in rapidly warming polar and alpine regions.

Exploring magnetic properties at the molecular level is a challenge that has been met by developing many experimental and theoretical solutions, such as polarized neutron diffraction (PND), muon-spin rotation (μ-SR), electron paramagnetic resonance (EPR), SQUID-based magnetometry measurements, and advanced modeling on open-shell systems and relativistic calculations. These methods are powerful tools that shed light on the local magnetic response in specifically designed magnetic materials such as contrast agents, for MRI, molecular magnets, magnetic tags for biological NMR, etc. All of these methods have their advantages and disadvantages. In order to complement the possibilities offered by these methods, we propose a new tool that implements a new approach combining simulation and fitting for high-resolution solid-state NMR spectra of lanthanide-based paramagnetic species. This method relies on a rigorous acquisition thanks to short high-power adiabatic pulses (SHAP) of high-resolution solid-state NMR isotropic and anisotropic data on a powdered magnetic material. It is also based on an efficient modeling of this data thanks to a semiempirical model based on a parametrization of the local magnetism and the crystal structure provided by diffraction methods. The efficiency of the calculation relies on a thorough simplification of the electron-nucleus interactions (point-dipole interaction, no Fermi contact) which is validated by experimental analysis. By taking advantage of the efficient calculation possibilities offered by our method, we can compare a great number of simulated spectra to experimental data and find the best-matching local magnetic susceptibility tensor. This method was applied to a series of isostructural lanthanide oxalates which are used as a benchmark system for many analytical methods. We present the results of thorough solid-state NMR and extensive modeling of the hyperfine interaction (including up to 400 paramagnetic centers) that yield local magnetic susceptibility tensor measurements that are self-consistent as well as consistent with bulk susceptibility measurements.

Reactions in water at ambient temperature and pressure between a lanthanide ion and benzene-1,3,5-tricarboxylate (or trimesate) lead to two series of iso-structural coordination polymers. Their general chemical formula is [Ln(tma)(H2O)6]∞ for the lightest lanthanide ions (Ln = La-Dy except Pm), while it is [Ln(tma)(H2O)5·3.5H2O]∞ for the heaviest ones (Ho-Lu plus Y). For the heaviest lanthanide ions, reactions at 50 °C lead to a third structural family with the general chemical formula [Ln(tma)(H2O)3·1.5H2O]∞ with Ln = Ho-Lu plus Y. Homo-lanthanide coordination polymers that belong to the latter two families do not exhibit luminescence in the visible region. Therefore, we used a phase induction strategy to obtain molecular alloys that belong to these structural families and show sizeable emission. The random distribution of the lanthanide ions over the metallic sites has been investigated using 89Y and 139La solid-state NMR spectroscopy experiments. Luminescent properties of homo- and hetero-nuclear coordination polymers based on Eu3+ and Tb3+ have been studied in detail and compared. As a result, this study strongly suggests that exchange-based intermetallic energy transfer mechanisms play an important role in these systems. It also suggests the presence of an intermetallic exchange pathway through π-stacking interactions.

Six lanthanides complexes with chemical formula [Ln(phen)(2)(NO3)(3)] (Ln = Sm(1), Tb (2), Nd (3), Eu (4), Ho (5) and Y (6), phen = 1,10-phenanthroline) were synthesized. 1 and 2 were obtained as single crystals by slow diffusion. Structural characterization was based on single crystal X-ray diffraction and IR and Y-89-NMR spectroscopies. NMR spectroscopic measurements were performed on [Y(phen)(2)(NO3) (3)](6) and [Y0.75Lu0.25(phen)(2)(NO3)(3)] (7). Compounds obtained as microcrystalline powders were characterized by powder X-ray diffraction. The complexes crystallize in the monoclinic system, space group P2(1)/n. Each Ln(III) ion is surrounded by four N atoms from two bidentate phenanthroline ligands and six O atoms from three chelating nitrate groups. The phenanthroline ligand provides efficient sensitization of the complexes that exhibit sizeable luminescence under UV irradiation. Thermal properties have been studied. They confirm the absence of water molecules in the crystal structure. The complexes are thermally stable up to 290 degrees C. Microcrystalline powders of hetero-lanthanide complexes, with global chemical formula [Tb1-xEux(phen)(2) (NO3)(3)] (series 8) and [Tb1-xGdx(phen)(2)(NO3)(3)] (series 9) were synthesized. Their photo-physical properties have been investigated. They demonstrate that luminescent molecular alloys can be obtained from lanthanides complexes and not only from hetero-nuclear coordination polymers as previously reported.

Dynamics of confined molecules within porous materials is equally important as local structural order, and it is necessary to quantify it and to reveal the microscopic mechanisms ruling it for better control of adsorption applications. In this study, molecular dynamics simulations were carried out to investigate the translational and the rotational dynamics of methanol trapped into the flexible NH2-MIL-53(Al) metal-organics framework (MOF). Indeed, atomistic simulation is nowadays a relevant tool to explore matter at the nanoscale. Very recently it has been shown that the NH2-MIL-53(Al) MOF material was capable to undergo a reversible structural transition (breathing phenomenon) by combining adsorption and thermal stimuli. This flexibility can drastically affect the dynamics of confined molecules and therefore the successful conduct of adsorption applications such as gas storage and separation. Rotational and translational dynamics of confined methanol through nanoporous flexible NH2-MIL-53(Al) MOF were then deeply investigated by exploring a broad range of dynamical properties to extract the molecular mechanisms ruling them. This study allowed us to shed light on the interplay of dynamics of confined fluids and flexibility of porous material and to highlight the physical insights in diffusion mechanisms of confined molecules. Anomalous translational diffusion was evidenced due to a dynamical heterogeneity caused by a combination of a localized dynamics at the subnanometric scale and translational jumps between nanodomains in a zigzag scheme between the hydroxide group of the NH2-MIL-53(Al). Actually, the non-Fickian dynamics of methanol is the result of the specific host-guest interactions and the MOF flexibility involving the pore opening. Eventually, decoupling between both rotational and translational dynamics related to breaking in the Stokes-Einstein relation was highlighted.

In this paper we undertake a study of the decoupling efficiency of the Multiple-Pulse (MP) scheme, and a rationalization of its parameterization and of the choice of instrumental set up. This decoupling scheme is known to remove the broadening of spin-1/2 spectra I, produced by the heteronuclear scalar interaction with a half-integer quadrupolar nucleus S, without reintroducing heteronuclear dipolar interaction. The resulting resolution enhancement depends on the set-up of the length of the series of pulses and delays of the MP, and some intrinsic material and instrumental parameters. Firstly through a numerical approach, this study investigates the influence of the main intrinsic material parameters (heteronuclear dipolar and J coupling, quadrupolar interaction, spin nature) and instrumental parameters (spinning rate, pulse field strength) on efficiency and resolution enhancement of the scalar decoupling scheme. A guideline is then proposed to obtain quickly and easily the best resolution enhancement via the rationalization of the instrumental and parameter set up. It is then illustrated and tested through experimental data, probing the efficiency of MP-decoupling set up using this guideline. Various spin systems were tested (31P-51V in VOPO4, 31P-93Nb in NbOPO4, 119Sn-17O in Y2Sn2O7), combined with simulations results.

We carried out a detailed investigation of the local ordering and dynamics of the lithium intercalation in paramagnetic LixVOPO4 center dot 2H(2)O (with 0 < x <= 1) materials. This question was addressed using a combination of X-ray diffraction, P-31 and Li-7 MAS NMR experiments. We first studied the structure of the fully ordered end-member of the series, Li1VOPO4 center dot 2H(2)O, revisiting the X-ray single crystal diffraction data on the basis of the information provided by P-31 MAS NMR. We then carried out Li-7 MAS and exchange NMR experiments and P-31 MAS experiments on the polycrystalline powders obtained after partial lithium insertion in VOPO4 center dot 2H(2)O phases. These experiments evidenced an unexpected ageing of the material related with lithium dynamics between the VOPO4 layers and a V4+/V5+ charge ordering mechanism within the layers.

This work aims at studying the influence of structural parameters on computations of the 93Nb quadrupolar interaction and chemical shift parameters in various niobates using first-principles approaches. We demonstrate that some of the computed NMR parameters, especially the isotropic chemical shift and the quadrupolar coupling constant, may differ either the X-ray crystal structure or a relaxed structure used for the calculation of the spectroscopic properties.

Isostructural lanthanide-based coordination polymers that are obtained by reactions in water of a lanthanide chloride and the sodium salt of 5-methoxyisophthalate (mip2-) have the general chemical formula [Ln2(mip)3(H2O)8·4H2O]∞ with Ln = Nd-Er except Pm plus Y (symbolized by [Ln2(mip)3]∞). Some of these homo-lanthanide compounds present very high luminescence brightness. The weak intermetallic energy transfer between lanthanide ions observed in these compounds allows the design of hetero-lanthanide coordination polymers with tunable luminescence properties. A molecular alloy that involved six different lanthanide ions (Nd3+, Sm3+, Eu3+, Gd3+, Tb3+, Dy3+) has been prepared and its luminescent properties have been studied. This compound, under a unique irradiation wavelength (λexc = 325 nm), exhibits almost 20 emission peaks in both the visible and the NIR regions at room temperature. This unprecedented richness of the emission spectrum could be of great interest as far as luminescent bar-codes are targeted.

The structure of the binary chalcohalide glasses Te1- xCl x (0.35 ≤ x ≤ 0.65) is considered by combining experimental and theoretical results. The structural network properties are influenced by a competition between ionic and covalent bonding in such glasses. At first, a focus is placed on the detailed information available by using the complementary high-energy X-ray and the neutron diffractions in both the reciprocal and real spaces. The main characteristic suggested by the structure factors S( Q) concerns the presence of three length scales in the intermediate range order. The total correlation function T( r) lets us also suppose that the structure of these glasses is more complicated than Te-chain fragments with terminal Cl as demonstrated in crystalline Te3Cl2. Molecular dynamics simulations were subsequently performed on Te3Cl2 and Te2Cl3, and coupled with the experimental data, a highly reticulated network of chalcogen atoms, with a fair amount of chlorine atoms bonded in a bridging mode, is proposed. The simulations clearly lead to a glass description that differs markedly from the simple structural model based on only Te atom chains and terminal Cl atoms. Solid-state NMR experiments and NMR parameters calculations allowed validation of the presence of Te highly coordinated with chlorine in these glasses.

The dynamical behavior of the organic cations in hybrid halide perovskites has triggered a wealth of experimental and theoretical investigations in the recent years. The intrinsic dynamical and electrical (dipolar) properties of the organic part were suggested to be responsible of some of the most noticeable features of these materials. Previous investigations [Phys. Chem. Chem. Phys. 2016, 18, 27133] have shown that static theoretical calculations of quadrupolar parameters (2H) in the orthorhombic phase of deuterated-MAPbBr3 (MA = CH3NH3+), lead to an overestimation of the linewidth broadening. This was rationalized in terms of thermally activated internal rotational dynamics of the molecular cations. Impact of the dynamics is further inspected in the present paper by a joint experimental and theoretical effort with low temperature solid-state NMR measurements (< 25K). Starting from extensive Ab initio molecular dynamics trajectories performed on large (4x4x4) supercells for both the tetragonal and orthorhombic phases [J. Phys. Chem. C 2017, 121, 20729] we use a specifically designed procedure to account for the effect of the thermally activated cation dynamics in the calculated NMR parameters, which includes the quadrupolar lineshapes of the NMR spectra.

Reversible structural transition between the Large (LP) and Narrow Pore (NP) forms (breathing phenomena) of the MIL-53(X, X = Al, Cr, Fe, Ga) Metal Organic Framework (MOF) is probably one of the most amazing physical properties of this class of soft-porous materials. Whereas great attention has been paid to the elucidation of the physical mechanism ruling this reversible transition, the effect of the functionalization on the flexibility has been less explored. Among functionalized MIL-53(Al) materials, the case of NH2-MIL-53(Al) is undoubtedly a very intriguing structural transition rarely observed, and the steadier phase corresponds to the narrow pore form. In this work, the flexibility of the NH2-MIL-53(Al) metal organic framework was investigated by means of molecular dynamics simulations. Guest (methanol) and thermal breathing of the NH2-MIL-53(Al) was thus explored. We show that it is possible to trigger a reversible transition between NP and LP forms upon adsorption, and we highlight the existence of stable intermediate forms and a very large pore phase. Furthermore, the NP form is found thermodynamically stable from 240 to 400 K, which is the result of strong intramolecular hydrogen bonds.

Quasicrystals belongs to a new state of matter, whose discovery was recently awarded by the Nobel prize, which presents a long range order without translational symmetry. Major questions concern the location of the atoms, their dynamics and possible structural phase transitions. The family of icosahedral quasicrystals of Tsai type [1,2] contains binary stable i-QC with low chemical disorder that offer the opportunity of precise structural analysis [3]. Neutron scattering [4] showed evidences of a dynamics of the central symmetry-breaking tetrahedron in the periodic approximant, and the phase transition near 160K was explained by an ordering of the tetrahedra. These results raise fundamental questions about the origin of the phase transition, and the coupling between the different shells of the Tsai cluster which is the main building unit of the approximant and i-QC (Fig.1). In this presentation, we will report results of 45Sc (I=7/2) and 67Zn (I=5/2) solid-state NMR experiments at different fields, and temperatures, in the 1/1 approximant Zn6Sc and quasicrystal ZnScAg. In particular, 67Zn spectra of Zn6Sc approximant were obtained at fields up to 18.8T (Lille High Field NMR platform). Observing such a nucleus was a challenge in such metallic samples, because of its very low sensitivity (low nuclear gyromagnetic ratio, natural abundance of 4.1%, medium quadrupolar coupling). Both nuclei carry complementary information within the icosahedral cluster, composed of five successive shells of increasing radius : tetrahedron (4Zn), dodecahedron (20Zn), icosahedron (12Sc), icosidodecahedron (30Zn) and rhombic triancontahedrom (92Zn). Scandium that belongs only to the icosahedron shell are particularly well suited to probe intershell coupling and tetrahedron induced distorsions. We will discuss how NMR provides insight in the structure and dynamics of these compounds. Acknowledgements: We acknowledge IRRMN FR3050 CNRS for support of High Field NMR experiments in Lille. This research received FEDER financial support (FEDER 34722-Prin2Tan) for funding NMR spectrometers in Rennes. References [1] A. P. Tsai, J. Q. Guo, E. Abe, H. Takakura, T. J. Sato, Nature, 2000, 408, 537 [2] A.P. Tsai, Chem. Soc. Rev., 2013, 42, 5352. [3] H. Takakura, C. Pay Gomez, A. Yamamoto, M. de Boissieu, A. P. Tsai, Nat. Mater.,2007, 6,58 [4] H. Euchner et al., J Phys: Condens. Matter 24,p415403 (2012);

Three volatile organic compounds (VOCs), benzene, cyclohexane, and dichloromethane, were adsorbed onto activated carbon fiber cloth. 1H (magic-angle spinning (MAS) and pulsed field gradient (PFG)) NMR techniques were carried out, and the signals were analyzed in terms of peak surface areas and shifts. These techniques were shown to be very useful for determining (i) the intrinsic quantification of adsorbed molecules (VOCs and/or water) in the porosity of the materials (the adsorption capacities ranged from 0.2 to 4 mol·kg-1); (ii) the mechanisms of interactions between adsorbed organic molecules and the carbon walls (illustrations of positions of the molecule inside the pore volume are proposed; the proton-wall distance was less than 0.15 nm); and (iii) the diffusivities (surface diffusion coefficients (DS) were estimated at ≈4.10-12 m2·s-1 for cyclohexane, ≈1.10-11 m2·s-1 for benzene, and ≈4.10-11 m2·s-1 for dichloromethane).

An ammonium vanadyl oxalatophosphite has been synthesized by hydrothermal treatment. The formula is (NH4)2(VOHPO3)2C2O4 2·9H2O (1). The crystal structure of the compound has been determined by single crystal X-ray diffraction and solid state Nuclear Magnetic Resonance spectroscopy (NMR). Compound 1 crystallizes in triclinic symmetry with space group P−1, a = 6.3844(4)Å, b = 7.2278(4)Å, c = 9.2965(5)Å, α = 67.260(4)°, β = 72.927(4)°, γ = 85.848(3)°. The vanadium phosphite framework consists of infinite chains of corner-sharing vanadium octahedra and hydrogenophosphite tetrahedra. The oxalate groups ensure the connection between the chains. The ammonium ions and the water molecules are located between the anionic [(VO)2(HPO3)2C2O4]2− layers. The thermal behaviour of 1 was carefully studied by combining thermogravimetric analyses, in situ X-ray diffraction and Infrared spectroscopy. The formation of given vanadyl phosphate catalysts was shown to be atmosphere-dependent of (NH4)2(VOHPO3)2C2O4 2·9H2O thermal decomposition.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Presenting high solar energy conversion efficiencies (21%), Hybrid Perovskite APbX3 (A is a small organic cation, X=Cl, Br, I) have recently become one of the most promising compound in the field of photovoltaic devices. In a first step, we will present a room temperature NMR study of three methylammonium lead halides, namely MAPbX3 (MA=CH3NH3). Investigation of the organic part confirms the isotropic mobility of the methylammonium cations while the structure of the inorganic part is confirmed by Pb NMR. Several years ago, R.E. Wasylishen et al. had already revealed the interest of deuterium NMR to investigate the temperature behaviour and the dynamics operating in such materials in their isotropic phase. Thus, in a second step we will focus on CH3ND3PbBr3 in the anisotropic dynamic regime. By using a homemade probehead, we can discuss on the dynamical behaviour of the inorganic part of such hybrid perovskites, which can be further rationalized based on appropriate theoretical approaches4.