Base-pairing of uracil and 2,6-diaminopurine: from cocrystals to photoreactivity

We show that the non-canonical nucleobase 2,6-diaminopurine (D) spontaneously base pairs with uracil (U) in water and the solid state without the need to be attached to the ribose-phosphate backbone. Depending on the reaction conditions, D and U assemble in thermodynamically stable hydrated and anhydrated D-U base-paired cocrystals. Under UV irradiation, an aqueous solution of D-U base-pair undergoes photochemical degradation, while a pure aqueous solution of U does not. Our simulations suggest that D may trigger the U photodimerization and show that complementary base-pairing modifies the photochemical properties of nucleobases, which might have implications for prebiotic chemistry.

A Second Glass Transition Observed in Single-Component Homogeneous Liquids Due to Intramolecular Vitrification

On supercooling a liquid, the viscosity rises rapidly until at the glass transition it vitrifies into an amorphous solid accompanied by a steep drop in the heat capacity. Therefore, a pure homogeneous liquid is not expected to display more than one glass transition. Here we show that a family of single-component homogeneous molecular liquids, titanium tetraalkoxides, exhibit two calorimetric glass transitions of comparable magnitude, one of which is the conventional glass transition associated with dynamic arrest of the bulk liquid properties, while the other is associated with the freezing out of intramolecular degrees of freedom. Such intramolecular vitrification is likely to be found in molecules in which low-frequency terahertz intramolecular motion is coupled to the surrounding liquid. These results imply that intramolecular barrier-crossing processes, typically associated with chemical reactivity, do not necessarily follow the Arrhenius law but may freeze out at a finite temperature.

Interfacial alloying between lead halide perovskite crystals and hybrid glasses

The stellar optoelectronic properties of metal halide perovskites provide enormous promise for next-generation optical devices with excellent conversion efficiencies and lower manufacturing costs. However, there is a long-standing ambiguity as to whether the perovskite surface/interface (e.g. structure, charge transfer or source of off-target recombination) or bulk properties are the more determining factor in device performance. Here we fabricate an array of CsPbI3 crystal and hybrid glass composites by sintering and globally visualise the property-performance landscape. Our findings reveal that the interface is the primary determinant of the crystal phases, optoelectronic quality, and stability of CsPbI3. In particular, the presence of a diffusion "alloying" layer is discovered to be critical for passivating surface traps, and beneficially altering the energy landscape of crystal phases. However, high-temperature sintering results in the promotion of a non-stoichiometric perovskite and excess traps at the interface, despite the short-range structure of halide is retained within the alloying layer. By shedding light on functional hetero-interfaces, our research offers the key factors for engineering high-performance perovskite devices.

Impact of Dye Encapsulation in ZIF-8 on CO2, Water, and Wet CO2 Sorption

The fast adsorption kinetics of zeolitic imidazolate frameworks (ZIFs) enable a wide range of sorption applications. The most commonly used framework, ZIF-8, is relatively non-polar. Increasing the polarity of ZIF-8 through the encapsulation of different polar species shows promise for enhancing the sorption performance for pure CO2. Recently, the outlook has re-focused on gas mixtures, mostly in the context of post-combustion CO2 capture from wet flue gasses. While water is known to sometimes have a synergistic effect on CO2 sorption, we still face the potential problem of preferential water vapor adsorption. Herein, we report the preparation of three ZIF-8/organic dye (OD) composites using Congo red, Xylenol orange, and Bromothymol blue, and their impact on the sorption properties for CO2, water, and a model wet CO2 system at 50% RH. The results show that the preparation of OD composites can be a promising way to optimize adsorbents for single gasses, but further work is needed to find superior ZIF@OD for the selective sorption of CO2 from wet gas mixtures.

Improving the molecular spin qubit performance in zirconium MOF composites by mechanochemical dilution and fullerene encapsulation

Enlarging the quantum coherence times and gaining control over quantum effects in real systems are fundamental for developing quantum technologies. Molecular electron spin qubits are particularly promising candidates for realizing quantum information processing due to their modularity and tunability. Still, there is a constant search for tools to increase their quantum coherence times. Here we present how the mechanochemical introduction of active spin qubits in the form of 10% diluted copper(ii)-porphyrins in the diamagnetic PCN-223 and MOF-525 zirconium-MOF polymorph pair can be achieved. Furthermore, the encapsulation of fullerene during the MOF synthesis directs the process exclusively toward the rare PCN-223 framework with a controllable amount of fullerene in the framework channels. In addition to the templating role, the incorporation of fullerene increases the electron spin-lattice and phase-memory relaxation times, T1 and Tm. Besides decreasing the amount of nuclear spin-bearing solvent guests in the non-activated qubit frameworks, the observed improved relaxation times can be rationalized by modulating the phonon density of states upon fullerene encapsulation.

Winning Combination of Cu and Fe Oxide Clusters with an Alumina Support for Low-Temperature Catalytic Oxidation of Volatile Organic Compounds

A γ-alumina support functionalized with transition metals is one of the most widely used industrial catalysts for the total oxidation of volatile organic compounds (VOCs) as air pollutants at higher temperatures (280-450 °C). By rational design of a bimetal CuFe-γ-alumina catalyst, synthesized from a dawsonite alumina precursor, the activity in total oxidation of toluene as a model VOC at a lower temperature (200-380 °C) is achieved. A fundamental understanding of the catalyst and the reaction mechanism is elucidated by advanced microscopic and spectroscopic characterizations as well as by temperature-programmed surface techniques. The nature of the metal-support bonding and the optimal abundance between Cu-O-Al and Fe-O-Al species in the catalysts leads to synergistic catalytic activity promoted by small amounts of iron (Fe/Al = 0.005). The change in the metal oxide-cluster alumina interface is related to the nature of the surfaces to which the Cu atoms attach. In the most active catalyst, the CuO₆ octahedra are attached to 4 Al atoms, while in the less active catalyst, they are attached to only 3 Al atoms. The oxidation of toluene occurs via the Langmuir-Hinshelwood mechanism. The presented material introduces a prospective family of low-cost and scalable oxidation catalysts with superior efficiency at lower temperatures.

Nitroreductase-sensitive fluorescent covalent organic framework for tumor hypoxia imaging in cells

Covalent organic frameworks (COFs) have been used in cell imaging, but very rarely for imaging specific cell conditions. Herein, a β-ketoenamine-based fluorescent COF was post-synthetically modified to incorporate a hypoxia-targeting molecule. Fluorescence microscopy imaging shows that the material discriminates between HeLa cells grown under hypoxia and those cultured under normoxia.

Understanding the emergence of the boson peak in molecular glasses

A common feature of glasses is the "boson peak", observed as an excess in the heat capacity over the crystal or as an additional peak in the terahertz vibrational spectrum. The microscopic origins of this peak are not well understood; the emergence of locally ordered structures has been put forward as a possible candidate. Here, we show that depolarised Raman scattering in liquids consisting of highly symmetric molecules can be used to isolate the boson peak, allowing its detailed observation from the liquid into the glass. The boson peak in the vibrational spectrum matches the excess heat capacity. As the boson peak intensifies on cooling, wide-angle x-ray scattering shows the simultaneous appearance of a pre-peak due to molecular clusters consisting of circa 20 molecules. Atomistic molecular dynamics simulations indicate that these are caused by over-coordinated molecules. These findings represent an essential step toward our understanding of the physics of vitrification.

Cationic Covalent Organic Polymer Thin Film for Label-free Electrochemical Bacterial Cell Detection

Numerous species of bacteria pose a serious threat to human health and cause several million deaths annually. It is therefore essential to have quick, efficient, and easily operable methods of bacterial cell detection. Herein, we synthesize a novel cationic covalent organic polymer (COP) named CATN through the Menshutkin reaction and evaluate its potential as an impedance sensor for Escherichia coli cells. On account of its positive surface charge (ζ-potential = +21.0 mV) and pyridinium moieties, CATN is expected to interact favorably with bacteria that possess a negatively charged cell surface through electrostatic interactions. The interdigitated electrode arrays were coated with CATN using a simple yet non-traditional method of electrophoresis and then used in two-electrode electrochemical impedance spectroscopy (EIS) measurements. The impedance response showed a linear relationship with the increasing concentration of E. coli. The system was sensitive to bacterial concentrations as low as ∼30 CFU mL^-1, which is far below the concentration considered to cause illnesses. The calculated limit of detection was as low as 2 CFU mL^-1. This work is a rare example of a COP used in this type of bacteria sensing and is anticipated to stimulate further interest in the synthesis of organic polymers for EIS-based sensors.

Trinuclear Magnesium Imidazolate Borohydride Complex

A new type of hybrid compound, combining properties of MOFs and borohydrides, was synthesized solvothermally using Mg(BH₄)₂ and imidazole as precursors. Material in the form of acetonitrile solvate with formula [Mg₃{(Im)BH₂(Im)}₆(ImH)₆]·CH₃CN crystallizes in the space group R3̅, having the unit cell parameters a = 15.1942(2) Å and c = 28.3157(3) Å as determined by single crystal X-ray diffraction. The structure was further investigated by solid-state NMR and DFT quantum chemical calculations. The main feature of the structure, reported here for the first time, is a linear trinuclear complex, where octahedrally nitrogen-coordinated Mg²⁺ ions are bridged with {(Im)BH₂(Im)}^- units, forming inside voids of 4.6 Å in diameter between the magnesium ions. Polar intermolecular interactions hold the molecules in a dense rhombohedral stacking, where a disordered acetonitrile molecule plays a cohesive role. The compound is stable in air and upon heating to about 160 °C. Using an alternative synthesis method from an imidazole melt, an imidazole solvate with the formula [Mg₃{(Im)BH₂(Im)}₆(ImH)₆]·ImH and a very similar crystal structure to acetonitrile solvate was prepared. It is stable up to 220 °C. Upon further heating, it transformed into a layered structure with the formula Mg(Im₃BH)₂, space group P3̅1c, and unit cell parameters a = 8.7338(9) Å and c = 17.621(2) Å determined by synchrotron powder diffraction. Besides its structural novelty, two types of potentially reactive hydrogens, bonded to boron and nitrogen in the same molecule, make the material highly interesting for future investigations in the fields of energy storage applications.

Polythiacalixarene-Embedded Gold Nanoparticles for Visible-Light-Driven Photocatalytic CO2 Reduction

Metal nanoparticles are potent reaction catalysts, but they tend to aggregate, thereby limiting their catalytic efficiency. Their coordination with specific functional groups within a porous structure prevents their aggregation and facilitates the mass flow of catalytic starting materials and products. Herein, we use a thiacalix[4]arene-based polymer as a porous support with abundant docking sites for Au nanoparticles. The sulfur atoms bridging the phenolic subunits of thiacalix[4]arene serve as Lewis basic sites that coordinate Au atoms. Therefore, this approach takes advantage of the functional groups inherent in the monomer and avoids laborious postsynthetic modifications of the polymer. The presented system was tested for visible-light-driven photocatalytic CO₂ reduction, where it showed adequate ability to generate 6.74 μmol g^-1 CO over the course of 4 h, while producing small amounts of the CH₄ product. This study aims to stimulate interest in the design and development of synthetically simpler porous polymer supports for various metal nanoparticles in catalytic and other applications.

Insight into the interdependence of Ni and Al in bifunctional Ni/ZSM-5 catalysts at the nanoscale

Catalyst design is crucial for improving catalytic activity and product selectivity. In a bifunctional Ni/ZSM-5 zeolite type catalyst, catalytic properties are usually tuned via varying Al and Ni contents. While changes in acid properties associated with Al sites are usually closely investigated, Ni phases, however, receive inadequate attention. Herein, we present a systematic structural study of Ni in the Ni/ZSM-5 materials by using Ni K-edge XANES and EXAFS analyses, complemented by XRD and TEM, to resolve the changes in the local environment of Ni species induced by the different Al contents of the parent ZSM-5 prepared by a "green", template free technique. Ni species in Ni/ZSM-5 exist as NiO crystals (3-50 nm) and as charge compensating Ni²⁺ cations. The Ni K-edge XANES and EXAFS results enabled the quantification of Ni-containing species. At a low Al to Si ratio (n _Al/n _Si ≤ 0.04), the NiO nanoparticles predominate in the samples and account for over 65% of Ni phases. However, NiO is outnumbered by Ni²⁺ cations attached to the zeolite framework in ZSM-5 with a high Al to Si ratio (n _Al/n _Si = 0.05) due to a higher number of framework negative charges imparted by Al. The obtained results show that the number of highly reducible and active NiO crystals is strongly correlated with the framework Al sites present in ZSM-5 zeolites, which depend greatly on the synthesis conditions. Therefore, this kind of study is beneficial for any further investigation of the catalytic activities of Ni/ZSM-5 and other metal-modified bifunctional catalysts.

Study of Water Adsorption on EDTA-Modified LTA Zeolites

The present work deals with the study of water adsorption on acid-modified zeolites A. Commercial zeolites 4A (Na form) and 5A (Ca form) were subjected to EDTA dealumination, and their structure, textural properties and stability were checked by XRD, EDX, NMR and N₂ physisorption analyses. The water adsorption isotherms of the parent zeolites and their modified forms were measured at a temperature of 25 °C and up to a relative pressure of 0.9. The results show that the treatment with EDTA drastically changes the structural properties of the zeolites and increases the water adsorption capacity by up to 10%. The changes depend on the type of extra-framework cations (Na⁺ and Ca²⁺) and the EDTA concentration.

Metal-biomolecule frameworks (BioMOFs): a novel approach for "green" optoelectronic applications

In this study, a water-stable microcrystalline bioMOF was synthesized, characterized, and loaded with silver ions or highly emissive rare earth (RE) metals such as Eu³⁺/Tb³⁺. The obtained materials were used as active layers in a proof-of-concept sustainable light-emitting device, highlighting the potential of bioMOFs in optoelectronic applications.

Liquid-phase sintering of lead halide perovskites and metal-organic framework glasses

[Figure: see text].

Mechanochemically Synthesised Flexible Electrodes Based on Bimetallic Metal-Organic Framework Glasses for the Oxygen Evolution Reaction

The melting behaviour of metal-organic frameworks (MOFs) has aroused significant research interest in the areas of materials science, condensed matter physics and chemical engineering. This work first introduces a novel method to fabricate a bimetallic MOF glass, through melt-quenching of the cobalt-based zeolitic imidazolate framework (ZIF) [ZIF-62(Co)] with an adsorbed ferric coordination complex. The high-temperature chemically reactive ZIF-62(Co) liquid facilitates the formation of coordinative bonds between Fe and imidazolate ligands, incorporating Fe nodes into the framework after quenching. The resultant Co-Fe bimetallic MOF glass therefore shows a significantly enhanced oxygen evolution reaction performance. The novel bimetallic MOF glass, when combined with the facile and scalable mechanochemical synthesis technique for both discrete powders and surface coatings on flexible substrates, enables significant opportunities for catalytic device assembly.

Technical Note: Post-burial alteration of bones: Quantitative characterization with solid-state 1H MAS NMR

The identification of markers of the modifications occurring in human bones after death and of the sedimentary and post-sedimentary processes affecting their state of preservation, is of interest for several scientific disciplines. A new index, obtained from spectral deconvolution of the 1H MAS NMR spectra of bones, relating the number of organic protons to the amount of hydrogen nuclei in the OH- groups of bioapatite, is proposed as indicator of the state of preservation of the organic fraction. In the osteological material from three different archaeological sites, this index resulted positively correlated with the extent of collagen loss derived from infrared spectroscopy. Its sensitivity to changes in the physical and chemical characteristics of bone allows to identify distinct diagenetic pathways specific to each site and to distinguish different trajectories within the same site.

Scalable Mechanochemical Amorphization of Bimetallic Cu-Zn MOF-74 Catalyst for Selective CO2 Reduction Reaction to Methanol

Selective catalytic reduction of CO₂ to methanol has tremendous importance in the chemical industry. It mitigates two critical issues in the modern society, the overwhelming climate change and the dependence on fossil fuels. The most used catalysts are currently based on mixed copper and zinc phases, where the high surface of active copper species is a critical factor for the catalyst performance. Motivated by the recent breakthrough in the controllable synthesis of bimetallic MOF-74 materials by ball milling, we targeted to study the potential of ZnCu-MOF-74 for catalytic CO₂ reduction. Here, we tested whether the nanosized channels decorated with readily accessible and homogeneously distributed Zn and Cu metal sites would be advantageous for the catalytic CO₂ reduction. Unlike the inactive monometallic Cu-MOF-74, ZnCu-MOF-74 shows moderate catalytic activity and selectivity for the methanol synthesis. Interestingly, the postsynthetic mechanochemical treatment of desolvated ZnCu-MOF-74 resulted in amorphization and a significant increase in both the activity and selectivity of the catalyst despite the destruction of the well-ordered and porous MOF-74 architecture. The results emphasize the importance of defects for the MOF catalytic activity and the potential of amorphous MOFs to be considered as heterogeneous catalysts. Scanning electron microscopy (SEM), X-ray powder diffraction (XRD) and ¹³C magic angle-spinning nuclear magnetic resonance (MAS NMR) were applied to establish quantitative structure-reactivity relationships. The apparent activation energy of rate reaction kinetics has indicated different pathway mechanisms, primarily through reverse water-gas shift (RWGS). Prolonged time on stream productivity, stability and deactivation were assessed, analysing the robustness or degradation of metal-organic framework nanomaterials. Scalable MOF production processes are making the latter more appealing within emerging industrial decarbonisation, in particular for carbon capture and utilisation (CCU) or hydrogen carrier storage. Acknowledging scale, the costs of fabrication are paramount.

Highly Selective Removal of Perfluorinated Contaminants by Adsorption on All-Silica Zeolite Beta

Perfluorinated alkylated substances (PFASs) are widely used in industrial and commercial applications, leading to a widespread occurrence of these persistent and harmful contaminants in our environment. Removal of these compounds from surface and waste waters is being mandated by European and U.S. governments. Currently, there are no treatment techniques available that lower the concentrations of these compounds for large water bodies in a cost- and energy-efficient way. We hereby propose a hydrophobic, all-silica zeolite Beta material that is a highly selective and high-capacity adsorbent for PFASs, even in the presence of organic competitors. Advanced characterization data demonstrate that the adsorption process is driven by a very negative adsorption enthalpy and favorable steric factors.

Halogenated Metal-Organic Framework Glasses and Liquids

The synthesis of four novel crystalline zeolitic imidazolate framework (ZIF) structures using a mixed-ligand approach is reported. The inclusion of both imidazolate and halogenated benzimidazolate-derived linkers leads to glass-forming behavior by all four structures. Melting temperatures are observed to depend on both electronic and steric effects. Solid-state NMR and terahertz (THz)/far-IR demonstrate the presence of a Zn-F bond for fluorinated ZIF glasses. In situ THz/far-IR spectroscopic techniques reveal the dynamic structural properties of crystal, glass, and liquid phases of the halogenated ZIFs, linking the melting behavior of ZIFs to the propensity of the ZnN₄ tetrahedra to undergo thermally induced deformation. The inclusion of halogenated ligands within metal-organic framework (MOF) glasses improves their gas-uptake properties.

Unexpected linker-dependent Brønsted acidity in the (Zr)UiO-66 metal organic framework and application to biomass valorization

The functionality of the UiO-66(Zr) linkers affects the number of defects on the Zr6 clusters, leading to differences in the MOFs' Brønsted acidity, which promotes the dehydration of fructose into HMF.

Polyurea-crosslinked biopolymer aerogel beads

Polyurea-crosslinked calcium alginate and chitosan aerogel beads: novel fibrous biopolymer-based aerogels.

The boundary lipid around DMPC-spanning influenza A M2 transmembrane domain channels: Its structure and potential for drug accommodation

We have investigated the perturbation of influenza A M2TM in DMPC bilayers. We have shown that (a) DSC and SAXS detect changes in membrane organization caused by small changes (micromolar) in M2TM or aminoadamantane concentration and aminoadamantane structure, by comparison of amantadine and spiro[pyrrolidine-2,2'-adamantane] (AK13), (b) that WAXS and MD can suggest details of ligand topology. DSC and SAXS show that at a low M2TM micromolar concentration in DPMC bilayers, two lipid domains are observed, which likely correspond to M2TM boundary lipids and bulk-like lipids. At higher M2TM concentrations, one domain only is identified, which constitutes essentially all of the lipid molecules behaving as boundary lipids. According to SAXS, WAXS, and DSC in the absence of M2TM, both aminoadamantane drugs exert a similar perturbing effect on the bilayer at low concentrations. At the same concentrations of the drug when M2TM is present, amantadine and, to a lesser extent, AK13 cause, according to WAXS, a significant disordering of chain-stacking, which also leads to the formation of two lipid domains. This effect is likely due, according to MD simulations, to the preference of the more lipophilic AK13 to locate closer to the lateral surfaces of M2TM when compared to amantadine, which forms stronger ionic interactions with phosphate groups. The preference of AK13 to concentrate inside the lipid bilayer close to the exterior of the hydrophobic M2TM helices may contribute to its higher binding affinity compared to amantadine.

Layered Zn2[Co(CN)6](CH3COO) double metal cyanide: a two-dimensional DMC phase with excellent catalytic performance

A new, layered double metal cyanide phase proved to be a reusable, stable and highly active catalyst in two important DMC applications.

Double metal cyanides (DMCs) are well known, industrially applied catalysts for ring opening polymerization reactions. In recent years, they have been studied for a variety of catalytic reactions, as well as other applications, such as energy storage and Cs sorption. Herein, a new, layered DMC phase (L-DMC), Zn₂[Co(CN)₆](CH₃COO)·4H₂O, was synthesized. The structure, which crystallizes in the monoclinic space group P2₁/m, consists of positively charged {Zn₂Co(CN)₆}⁺ DMC layers linked through acetate groups and presents a new layered structure to the family of double metal cyanides. L-DMC proved to be a reusable and stable catalyst that exhibited a higher activity than the benchmark DMC catalyst in two important applications: hydroamination of phenylacetylene with 4-isopropylaniline and polymerization of 1,2-epoxyhexane.

Unraveling the Arrangement of Al and Fe within the Framework Explains the Magnetism of Mixed-Metal MIL-100(Al,Fe)

Properties of mixed-metal MOFs depend on the distribution of different metals within their frameworks. Determination of this distribution is often very challenging. Using an example of aluminum- and iron-containing MIL-100, we demonstrate that ²⁷Al NMR spectroscopy, when combined with first-principles calculations and magnetic, X-band electron paramagnetic resonance, Fe K-edge extended X-ray absorption fine structure, and Mössbauer measurements, enables one to accurately determine the arrangement of Al and Fe within the metal trimers, which are the basic building units of MIL-100. In this particular material, the incorporation of Fe and Al on the framework metal sites is random. Crucial for deciphering the arrangement is detecting NMR signals, shifted because of the strong hyperfine interaction between the ²⁷Al nuclei and the unpaired electronic spins of Fe³⁺ ions, assigning the shifted signals aided by first-principles calculations of hyperfine couplings, and quantitatively evaluating the NMR intensities and the measured effective magnetic moment.

Eumelanin Graphene-Like Integration: The Impact on Physical Properties and Electrical Conductivity

The recent development of eumelanin pigment-based blends integrating "classical" organic conducting materials is expanding the scope of eumelanin in bioelectronics. Beyond the achievement of high conductivity level, another major goal lays in the knowledge and feasible control of structure/properties relationship. We systematically investigated different hybrid materials prepared by in situ polymerization of the eumelanin precursor 5,6-dihydroxyindole (DHI) in presence of various amounts of graphene-like layers. Spectroscopic studies performed by solid state nuclear magnetic resonance (ss-NMR), x-ray photoemission, and absorption spectroscopies gave a strong indication of the direct impact that the integration of graphene-like layers into the nascent polymerized DHI-based eumelanin has on the structural organization of the pigment itself, while infrared, and photoemission spectroscopies indicated the occurrence of negligible changes as concerns the chemical units. A tighter packing of the constituent units could represent a strong factor responsible for the observed improved electrical conductivity of the hybrid materials, and could be possible exploited as a tool for electrical conductivity tuning.

Multinuclear Magnetic Resonance Study on Aluminium Sec-butoxide Chelated with Ethyl Acetoacetate in Various Amounts

Reactive aluminum alkoxide (ASB, aluminium sec-butoxide) was chelated using β-diketone (EAA, ethyl acetoacetate) in order to gain control over rapid hydrolysis in the course of the sol-gel process. Derived chelates were analysed using several NMR spectroscopic techniques: one-dimensional 1H, 13C, 27Al NMR and two-dimensional COSY, HSQC and DOSY. The NMR analysis enabled identification of the formed chelate species, as well as determination of their quantitative relationships. Several complexation products were observed: tris-chelated monomer, Al(EAA)3, bis-chelated dimmer, Al2(OnBu)4(EAA) 2, tris-chelated dimmer, Al2(OnBu)3(EAA)3, tetra-chelated dimmer, Al2(OnBu)2(EAA)4, and monochelated trimer, Al3(OnBu)8(EAA). Of the formed oligomer compounds, this is the first evidence of Al2(OR)3L3 in any alkoxide and β-ketoester or β-diketone combination. Aluminium sec-butoxide and ethyl acetoacetate complexes Al2(OnBu)4(EAA) 2 and Al2(OnBu)2(EAA)4 were also observed for the first time. With the increase of the EAA/ASB ratio the coordination of aluminium shifts towards six, whereas above the EAA/ASB ratio of 2.5 solely six-coordinated aluminium exists.

Magnetic resonance spectroscopy approaches for electrochemical research

In this review paper, we provide a short overview of the application of magnetic resonance techniques in electrochemical studies. Brief theoretical descriptions, sensitivity aspects, challenges and new opportunities of nuclear magnetic resonance and electron paramagnetic resonance have been presented here. Particular attention will be paid to the studies using ex situ and in situ methodologies and their combination to address the questions concerning the intrinsic structures and the structural transformations, ionic mobility and interfacial interactions in the energy storage and energy conversion systems. In addition, theoretical approaches to support the experimental NMR observables as well as magnetic resonance imaging have been discussed in the context of improving electrochemical performance, cycling stability and safety of batteries.

Comparative Perturbation Effects Exerted by the Influenza A M2 WT Protein Inhibitors Amantadine and the Spiro[pyrrolidine-2,2'-adamantane] Variant AK13 to Membrane Bilayers Studied Using Biophysical Experiments and Molecular Dynamics Simulations

Aminoadamantane drugs are lipophilic amines that block the membrane-embedded influenza A M2 WT (wild type) ion channel protein. The comparative effects of amantadine ( Amt) and its synthetic spiro[pyrrolidine-2,2'-adamantane] (AK13) analogue in dimyristoylphosphatidylcholine (DMPC) bilayers were studied using a combination of experimental biophysical methods, differential scanning calorimetry (DSC), X-ray diffraction, solid-state NMR (ssNMR) spectroscopy, and molecular dynamics (MD) simulations. All three experimental methods pointed out that the two analogues perturbed drastically the DMPC bilayers with AK13 to be more effective at high concentrations. AK13 was tolerated in lipid bilayers at very high concentrations, while Amt was crystallized. This is an important consideration in the formulations of drugs as it designates a limitation of Amt incorporation. MD simulations verify provided details about the strong interactions of the drugs in the interface region between phosphoglycerol backbone and lipophilic segments. The two drugs form hydrogen bonding with both water and sn-2 carbonyls in their amine form or water and phosphate oxygens in their ammonium form. Such localization of the drugs explains the DMPC bilayers reorientation and their strong perturbing effect evidenced by all biophysical methodologies applied.

A metal-organic framework with ultrahigh glass-forming ability

Glass-forming ability (GFA) is the ability of a liquid to avoid crystallization during cooling. Metal-organic frameworks (MOFs) are a new class of glass formers (1-3), with hitherto unknown dynamic and thermodynamic properties. We report the discovery of a new series of tetrahedral glass systems, zeolitic imidazolate framework-62 (ZIF-62) [Zn(Im_2-x bIm _x )], which have ultrahigh GFA, superior to any other known glass formers. This ultrahigh GFA is evidenced by a high viscosity η (10⁵ Pa·s) at the melting temperature T_m, a large crystal-glass network density deficit (Δρ/ρ_g)_network, no crystallization in supercooled region on laboratory time scales, a low fragility (m = 23), an extremely high Poisson's ratio (ν = 0.45), and the highest T_g/T_m ratio (0.84) ever reported. T_m and T_g both increase with benzimidazolate (bIm) content but retain the same ultrahigh T_g/T_m ratio, owing to high steric hindrance and frustrated network dynamics and also to the unusually low enthalpy and entropy typical of the soft and flexible nature of MOFs. On the basis of these versatile properties, we explain the exceptional GFA of the ZIF-62 system.

Improved resolution and simplification of the spin-diffusion-based NMR method for the structural analysis of mixed-linker MOFs

Nuclear magnetic resonance spectroscopy combined with modeling represents a powerful tool for the structural analysis of heterogeneous materials. In this contribution we describe an upgraded method, particularly suited for the structural analysis of mixed-linker metal-organic framework materials, which is based on the measurement and modeling of proton spin diffusion among constituents. We tested the method on a UiO-66-type metal-organic material, in which the organic building units were 1,4-benzenedicarboxylate and trans-1,4-cyclohexanedicarboxylate anions distributed within the framework in an unknown manner. We showed that resolution of the signals of different building units could be significantly enhanced by the carbon-detected version of the proton spin-diffusion measurement. Because this kind of measurement is much more time consuming than the proton-detected measurement and because one has to carry out several two-dimensional measurements to extract spin-diffusion curves, we inspected the possibility of reducing the number of such measurements. This could be done by limiting the analysis to short mixing times, for which, as shown in this contribution, linear approximation is valid. When working in the linear regime, only a few experimental points are needed to determine the slope of spin-diffusion curves. Usage of short spin-diffusion mixing times significantly shortened the total measurement time and also markedly simplified the modeling of spin-diffusion curves.

Exploring the interactions of irbesartan and irbesartan-2-hydroxypropyl-β-cyclodextrin complex with model membranes

The interactions of irbesartan (IRB) and irbesartan-2-hydroxypropyl-β-cyclodextrin (HP-β-CD) complex with dipalmitoyl phosphatidylcholine (DPPC) bilayers have been explored utilizing an array of biophysical techniques ranging from differential scanning calorimetry (DSC), small angle X-ray scattering (SAXS), ESI mass spectrometry (ESI-MS) and solid state nuclear magnetic resonance (ssNMR). Molecular dynamics (MD) calculations have been also conducted to complement the experimental results. Irbesartan was found to be embedded in the lipid membrane core and to affect the phase transition properties of the DPPC bilayers. SAXS studies revealed that irbesartan alone does not display perfect solvation since some coexisting irbesartan crystallites are present. In its complexed form IRB gets fully solvated in the membranes showing that encapsulation of IRB in HP-β-CD may have beneficial effects in the ADME properties of this drug. MD experiments revealed the topological and orientational integration of irbesartan into the phospholipid bilayer being placed at about 1nm from the membrane centre.

Ab initio crystal structure prediction of magnesium (poly)sulfides and calculation of their NMR parameters

Ab initio prediction of sensible crystal structures can be regarded as a crucial task in the quickly-developing methodology of NMR crystallography. In this contribution, an evolutionary algorithm was used for the prediction of magnesium (poly)sulfide crystal structures with various compositions. The employed approach successfully identified all three experimentally detected forms of MgS, i.e. the stable rocksalt form and the metastable wurtzite and zincblende forms. Among magnesium polysulfides with a higher content of sulfur, the most probable structure with the lowest formation energy was found to be MgS2, exhibiting a modified rocksalt structure, in which S2− anions were replaced by S2 2− dianions. Magnesium polysulfides with even larger fractions of sulfur were not predicted to be stable. For the lowest-energy structures, 25Mg quadrupolar coupling constants and chemical shift parameters were calculated using the density functional theory approach. The calculated NMR parameters could be well rationalized by the symmetries of the local magnesium environments, by the coordination of magnesium cations and by the nature of the surrounding anions. In the future, these parameters could serve as a reference for the experimentally determined 25Mg NMR parameters of magnesium sulfide species.

Eu3+-Doped Y3−xNdxAl3O12 garnet: synthesis and structural investigation

Nd³⁺-doped yttrium aluminium garnet and Eu³⁺–Nd³⁺-co-Doped yttrium aluminium garnet were synthesized using an environmentally friendly sol–gel method at low temperatures.

Dehydration of AlPO4-34 studied by variable-temperature NMR, XRD and first-principles calculations

Complementary techniques elucidate water–framework interactions in different states of dehydration, two of which have not been observed before.