Game of Crowns: Na+ Is Coming! Red NIR-Emissive Hybrid Liquid Crystals Containing Discotic Crown Ethers and Na2Mo6X8iCl6 (Xi = Cl or Br).

Molecular or supramolecular materials that can self-organize into columns such as discotic liquid crystals are of interest for several applications in the field of optoelectronics. We show in this work that red near-infrared (NIR)-emissive metal cluster compounds of general formula Na2Mo6X8iCl6 (Xi = Cl or Br) can be readily complexed with discotic liquid crystals containing a crown ether. Three cavity sizes have been tested with crown ethers bearing 4, 5, or 6 oxygen atoms. In all cases, 1:1 complexes were formed, thanks to the well-known supramolecular interactions existing between the Na+ cations of the metal cluster salt and the crown ether derivatives. All obtained hybrids are homogeneous, emit in the red NIR region, and show liquid crystalline properties on a wider temperature range than their precursors. Charge transport properties have been investigated by using a space charge limited current device. Obtained results demonstrate that metal cluster compounds can enhance the charge carrier mobility by 5 orders of magnitude compared to the native discotic organic ligands. Considering that the presented organic crown ether derivatives are not the best candidates to design optoelectronic devices because of their inherently low conductivity, but that similar compounds were developed to design proton conductive porous framework, our results open promising perspectives for the use of metal cluster compounds in devices dedicated to such a field.

Investigation of Intermetallic Energy Transfers in Lanthanide Coordination Polymers Molecular Alloys: Case Study of Trimesate-Based Compounds.

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.

Rationalization of solid-state NMR multi-pulse decoupling strategies: Coupling of spin I = ½ and half-integer quadrupolar nuclei.

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.

Anomalous Dynamics of a Nanoconfined Gas in a Soft Metal-Organics Framework.

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.

Multi-Emissive Lanthanide-Based Coordination Polymers for Potential Application as Luminescent Bar-Codes.

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.

Risedronate Effects on the In Vivo Bioactive Glass Behavior: Nuclear Magnetic Resonance and Histopathological Studies.

The present study aimed to enhance the anti-osteoporotic performance of bioactive glass (46S6) through its association with bisphosphonate such as risedronate with amounts of 8, 12, and 20%. Obtained composites have been called 46S6-8RIS, 46S6-12RIS, and 46S6-20RIS, respectively. In vitro and in vivo explorations have been carried out. Bioactive glass and risedronate association has been performed by adsorption process. Structure analyses have been carried out to evaluate and to understand their chemical interactions. Solid Nuclear Magnetic Resonance (NMR) has been employed to study the structural properties of obtained biocomposite. The spectra deconvolution showed the appearance of a species (Q 4) in the biocomposites 46S6-8RIS, 46S6-12RIS, and 46S6-20RIS indicating their successful chemical association. In vitro experiments showed the enhancement of the chemical reactivity of the composites 46S6-xRIS compared to the pure bioactive glass. In fact, the silicon liberation after 30 days of immersion was 50 ppm for pure bioactive glass 46S6, and 41, 64, and 62 from 46S6-8RIS, 46S6-12RIS, and 46S6-20RIS, respectively. Based on the in vitro results, 46S6-8RIS was implanted in the femoral condyle of an ovariectomized rat and compared with implanted pure glass in the goal to highlight its anti-osteoporotic performance. After 60 days, implanted group with 46S6-8RIS showed the increase in bone mineral density (BMD with 10%) and bone volume fraction (BV/TV with 80%) and the decrease in trabecular separation (Tb/Sp with 74%) when compared to that of 46S6 group. These results are confirmed by the histopathological analyses, which showed the bone trabeculae reconnection after the 46S6-8RIS implantation. Chemical analyses showed the reduction in silicon (Si) and sodium (Na) ion concentrations, and the rise in calcium (Ca) and phosphorus (P) ion levels, which was explained by the dissolution of biocomposite matrix and the deposition of hydroxyapatite layer. Histomorphometric results highlighted the risedronate effect on the antiosteoporotic phenomenon. Obtained results showed good behavior with only 8% of introduced risedronate in the glass matrix.

Strong Solid-state Luminescence Enhancement in Supramolecular Assemblies of Polyoxometalate and "Aggregation-Induced Emission"-active Phospholium.

Two new supramolecular fluorescent hybrid materials, combining for the first time [M6 O19 ]2- (M=Mo, W) polyoxometalates (POMs) and aggregation-induced emission (AIE)-active 1-methyl-1,2,3,4,5-pentaphenyl-phospholium (1+ ), were successfully synthesized. This novel molecular self-assembling strategy allows designing efficient solid-state emitters, such as (1)2 [W6 O19 ], by directing favorably the balance between the AIE and aggregation-caused quenching (ACQ) effects using both anion-π+ and H-bonding interactions in the solid state. Combined single-crystal X-ray diffraction, Raman, UV-vis and photoluminescence analyses highlighted that the nucleophilic oxygen-enriched POM surfaces strengthened the rigidity of the phospholium via strong C-H⋅⋅⋅O contacts, thereby exalting its solid-state luminescence. Besides, the bulky POM anions prevented π-π stacking interactions between the luminophores, blocking detrimental self-quenching effects.

Luminescent liquid crystalline hybrid materials by embedding octahedral molybdenum cluster anions with soft organic shells derived from tribenzo[18]crown-6.

Crown ethers and their derivatives are versatile building blocks for the design of supramolecular materials. They can be functionalized at will and are well known for their abilities to complex with alkali cations. Here, we show that emissive lanthanide free hybrid materials can be generated by using such building blocks. The organic tribenzo[18]crown-6 central core was functionalized via six-fold Suzuki cross-coupling as a key reaction with three o-terphenyl units which could be converted into their corresponding triphenylenes by the Scholl reaction, leading to novel liquid-crystalline columnar materials. Selected tribenzo[18]crown-6 o-terphenyls could interact with emissive ternary metal cluster compound salts to generate hybrid materials combining the properties of both moieties. Due to synergistic effects and despite the anisometry of the cluster compounds, individual properties such as liquid-crystalline phase stability of the organic part and emission abilities of its inorganic counter-part are enhanced in the hybrid compounds.

Lord of The Crowns: A New Precious in the Kingdom of Clustomesogens.

Replacing pure inorganic materials by functional organic-inorganic hybrid ones to lower production costs has become a major challenge, in particular for the optoelectronic industry. Adding nanostructuration abilities meanwhile preserving homogeneity is even more challenging for this class of new materials. Here we show that red-NIR emissive ternary molybdenum cluster salts can be assembled to liquid crystalline 15C5 crown ethers. The resulting hybrids are homogeneous and stable up to high temperature despite the weakness of the supramolecular interactions binding both components. These are illustrated by 133 Cs MAS NMR. All hybrids show hexagonal columnar arrangements and strong red-NIR emission. Surprisingly, when chlorinated clusters are used instead of brominated ones, the mesophase stability is largely enhanced.

Direct Integration of Red-NIR Emissive Ceramic-like An M6 Xi8 Xa6 Metal Cluster Salts in Organic Copolymers Using Supramolecular Interactions.

Hybrid nanomaterials made of inorganic nanocomponents dispersed in an organic host raise an increasing interest as low-cost solution-processable functional materials. However, preventing phase segregation while allowing a high inorganic doping content remains a major challenge, and usual methods require a functionalization step prior integration. Herein, we report a new approach to design such nanocomposite in which ceramic-like metallic nanocluster compounds are embedded at 10 wt % in organic copolymers, without any functionalization. Dispersion homogeneity and stability are ensured by weak interactions occurring between the copolymer lateral chains and the nanocluster compound. Hybrids could be ink-jet printed and casted on a blue LED. This proof-of-concept device emits in the red-NIR area and generates singlet oxygen, O2 (1 Δg), of particular interest for lights, display, sensors or photodynamic based therapy applications.

Solventless and Metal-Free Synthesis of High-Molecular-Mass Polyaminoboranes from Diisopropylaminoborane and Primary Amines.

The solventless reaction of diisopropylaminoborane with n-butylamine, at room temperature, leads to a mixture of B(sp2) H-, B(sp3) H2 -, and B(sp3) H3 -containing species. At low temperature, the reaction outcome is completely modified, thus leading selectively to the formation of high-mass polybutylaminoborane. When extended to a variety of primary amines, under solventless conditions and at low temperature, this reaction provides a new, efficient, and direct metal-free access to high-molecular-mass polyaminoboranes in good to high yields under mild reaction conditions.

Multinuclear NMR as a tool for studying local order and dynamics in CH3NH3PbX3 (X = Cl, Br, I) hybrid perovskites.

We report on 207Pb, 79Br, 14N, 1H, 13C and 2H NMR experiments for studying the local order and dynamics in hybrid perovskite lattices. 207Pb NMR experiments conducted at room temperature on a series of MAPbX3 compounds (MA = CH3NH3+; X = Cl, Br and I) showed that the isotropic 207Pb NMR shift is strongly dependent on the nature of the halogen ions. Therefore 207Pb NMR appears to be a very promising tool for the characterisation of local order in mixed halogen hybrid perovskites. 207Pb NMR on MAPbBr2I served as a proof of concept. Proton, 13C and 14N NMR experiments confirmed the results previously reported in the literature. Low temperature deuterium NMR measurements, down to 25 K, were carried out to investigate the structural phase transitions of MAPbBr3. Spectral lineshapes allow following the successive phase transitions of MAPbBr3. Finally, quadrupolar NMR lineshapes recorded in the orthorhombic phase were compared with simulated spectra, using DFT calculated electric field gradients (EFG). Computed data do not take into account any temperature effect. Thus, the discrepancy between the calculated and experimental EFG evidences the fact that MA cations are still subject to significant dynamics, even at 25 K.

Structure and Dynamics of Heteroprotein Coacervates.

Under specific conditions, mixing two oppositely charged proteins induces liquid-liquid phase separation. The denser phase, or coacervate phase, can be potentially applied as a system to protect or encapsulate different bioactive molecules with a broad range of food and/or medical applications. The optimization of the design and efficiency of such systems requires a precise understanding of the structure and the equilibrium of the nanocomplexes formed within the coacervate. Here, we report on the nanocomplexes and the dynamics of the coacervates formed by two well-known, oppositely charged proteins ß-lactoglobulin (ß-LG, pI ≈ 5.2) and lactoferrin (LF, pI ≈ 8.5). Fluorescence recovery after photobleaching (FRAP) and solid-state nuclear magnetic resonance (NMR) experiments indicate the coexistence of several nanocomplexes as the primary units for the coacervation. To our knowledge, this is the first evidence of the occurrence of an equilibrium between quite unstable nanocomplexes in the coacervate phase. Combined with in silico docking experiments, these data support the fact that coacervation in the present heteroprotein system depends not only on the structural composition of the coacervates but also on the association rates of the proteins forming the nanocomplexes.

Impact of 77Te on the structure and Se NMR spectra of Se-rich Ge-Te-Se glasses: a combined experimental and computational investigation.

Selenium-rich Ge-Te-Se glasses have been synthesized along the GeSe4-GeTe4 pseudo-composition line and acquired by (77)Se Hahn echo magic-angle spinning NMR. The comparison with the GeSe4 spectrum shows a drastic modification of the typical double-resonance lineshape even at low Te concentrations (<10%). In order to rationalize this feature and to understand the effect of Te on the structure of our glasses, first-principles molecular dynamics simulations and gauge including projector augmented wave NMR parameter calculations have been performed. The distribution of the tellurium atoms in the selenium phase was shown to be mainly responsible for the (77)Se lineshape changes. Another possible factor related to the perturbation of the δiso value due to Te proximity appears to be much more limited in the bulk, while the results obtained using molecular models suggest shifts of several hundreds of ppm.

From metallic cluster-based ceramics to nematic hybrid liquid crystals: a double supramolecular approach.

We describe a new supramolecular approach combining host-guest and electrostatic interactions to design hybrid materials containing polyanionic bulky inorganic compounds and showing liquid crystalline properties.

Recrystallized S-layer protein of a probiotic Propionibacterium: structural and nanomechanical changes upon temperature or pH shifts probed by solid-state NMR and AFM.

Surface protein layers (S layers) are common constituents of the bacterial cell wall and originate from the assembly of strain-dependent surface layer proteins (Slps). These proteins are thought to play important roles in the bacteria's biology and to have very promising technological applications as biomaterials or as part of cell-host cross-talk in probiotic mechanism. The SlpA from Propionibacterium freudenreichii PFCIRM 118 strain was isolated and recrystallized to investigate organization and assembly of the protein using atomic force microscopy and solid-state (1)H and (13)C-nuclear magnetic resonance. SlpA was found to form hexagonal p1 monolayer lattices where the protein exhibited high proportions of disordered regions and of bound water. The lattice structure was maintained, but softened, upon mild heating or acidification, probably in relation with the increasing mobilities of the disordered protein regions. These results gave structural insights on the mobile protein regions exposed by S layer films, upon physiologically relevant changes of their environmental conditions.

A combined 77Se NMR and molecular dynamics contribution to the structural understanding of the chalcogenide glasses.

Solid-state (77)Se NMR measurements, first-principles molecular dynamics and DFT calculations of NMR parameters were performed to gain insight into the structure of selenium-rich GexSe(1-x) glasses. We recorded the fully-relaxed NMR spectra on natural abundance and 100% isotopically enriched GeSe4 samples, which led us to reconsider the level of structural heterogeneity in this material. In this paper, we propose an alternative procedure to initialise molecular dynamics runs for the chalcogenide glasses. The (77)Se NMR spectra calculated on the basis of the structural models deduced from these simulations are consistent with the experimental spectrum.

Soil calcium availability influences shell ecophenotype formation in the sub-antarctic land snail, Notodiscus hookeri.

Ecophenotypes reflect local matches between organisms and their environment, and show plasticity across generations in response to current living conditions. Plastic responses in shell morphology and shell growth have been widely studied in gastropods and are often related to environmental calcium availability, which influences shell biomineralisation. To date, all of these studies have overlooked micro-scale structure of the shell, in addition to how it is related to species responses in the context of environmental pressure. This study is the first to demonstrate that environmental factors induce a bi-modal variation in the shell micro-scale structure of a land gastropod. Notodiscus hookeri is the only native land snail present in the Crozet Archipelago (sub-Antarctic region). The adults have evolved into two ecophenotypes, which are referred to here as MS (mineral shell) and OS (organic shell). The MS-ecophenotype is characterised by a thick mineralised shell. It is primarily distributed along the coastline, and could be associated to the presence of exchangeable calcium in the clay minerals of the soils. The Os-ecophenotype is characterised by a thin organic shell. It is primarily distributed at high altitudes in the mesic and xeric fell-fields in soils with large particles that lack clay and exchangeable calcium. Snails of the Os-ecophenotype are characterised by thinner and larger shell sizes compared to snails of the MS-ecophenotype, indicating a trade-off between mineral thickness and shell size. This pattern increased along a temporal scale; whereby, older adult snails were more clearly separated into two clusters compared to the younger adult snails. The prevalence of glycine-rich proteins in the organic shell layer of N. hookeri, along with the absence of chitin, differs to the organic scaffolds of molluscan biominerals. The present study provides new insights for testing the adaptive value of phenotypic plasticity in response to spatial and temporal environmental variations.

Coordination polymers based on heterohexanuclear rare earth complexes: toward independent luminescence brightness and color tuning.

Reactions in solvothermal conditions between hexanuclear rare earth complexes and H2bdc, where H2bdc symbolizes terephthalic acid, lead to a family of monodimensional coordination polymers in which hexanuclear complexes act as metallic nodes. The hexanuclear cores can be either homometallic with general chemical formula [Ln6O(OH)8(NO3)6](2+) (Ln = Pr-Lu plus Y) or heterometallic with general chemical formula [Ln(6x)Ln'(6-6x)O(OH)8(NO3)6](2+) (Ln and Ln' = Pr-Lu plus Y). Whatever the hexanuclear entity is, the resulting coordination polymer is iso-structural to [Y6O(OH)8(NO3)2(bdc)(Hbdc)2·2NO3·H2bdc]∞, a coordination polymer that we have previously reported. The random distribution of the lanthanide ions over the six metallic sites of the hexanuclear entities is demonstrated by (89)Y solid state NMR, X-ray diffraction (XRD), and luminescent measurements. The luminescent and colorimetric properties of selected compounds that belong to this family have been studied. These studies demonstrate that some of these compounds exhibit very promising optical properties and that there are two ways of modulating the luminescent properties: (i) playing with the composition of the heterohexanuclear entities or (ii) playing with the relative ratio between two different hexanuclear entities. This enables the independent tuning of luminescence intensity and color.

DFT-assisted structure determination of α1- and α2-VOPO4: new insights into the understanding of the catalytic performances of vanadium phosphates.

Structural investigations on vanadium phosphates, which are extensively used as catalysts in industry, often resulted in important advances in the understanding of the mechanisms driving the catalytic oxidation of light hydrocarbons. Layer translations in the two lamellar vanadium phosphates α1- and α2-VOPO4 phases identified during the catalysis were investigated by the combination of first-principles calculations, synchrotron X-ray powder diffraction, single-crystal X-ray diffraction and solid-state NMR. This analysis reveals an important feature: the α1-form is the only polymorph of VOPO4 to exhibit layer translations that prevent the formation of infinite VO6 chains. A detailed investigation of this structural characteristic in vanadium phosphates reveals the correlation between the presence of infinite VO6 chains and the catalytic performances of related phases.