Aluminum Molecular Ring Meets Deep Eutectic Solvents: Adaptive Assembly and Optical Behavior

Different from the previous neutral reaction solvent system, this work explores the synthesis of Al-oxo rings in ionic environments. Deep eutectic solvents (DESs) formed by quaternary ammonium salts hydrogen bond acceptor (HBA) and phenols hydrogen bond donor (HBD) further reduce the melting point of the reaction system and provide an ionic environment. Further, the quaternary ammonium salt was chosen as the HBA because it contains a halogen anion that matches the size of the central cavity of the molecular ring. Based on this thought, five Al8 ion pair cocrystals were synthesized via "DES thermal". The general formula is Q+ ⊂ {Cl@[Al8(BD)8(μ2-OH)4L12]} (AlOC-180-AlOC-185, Q+ = tetrabutylammonium, tetrapropylammonium, 1-butyl-3-methylimidazole; HBD = phenol, p-chlorophenol, p-fluorophenol; HL = benzoic acid, 1-naphthoic acid, 1-pyrenecarboxylic acid, anthracene-9-carboxylic acid). Structural studies reveal that the phenol-coordinated Al molecular ring and the quaternary ammonium ion pair form the cocrystal compounds. The halogen anions in the DES component are confined in the center of the molecular ring, and the quaternary ammonium cations are located in the organic shell. Such an adaptive cocrystal binding pattern is particularly evident in the structures coordinated with low-symmetry ligands such as naphthoic acid and pyrene acid. Finally, the optical behavior of these cocrystal compounds is understood from the analysis of crystal structure and theoretical calculation.

Properties and Applications of Metal Phosphates and Pyrophosphates as Proton Conductors

We review the progress in metal phosphate structural chemistry focused on proton conductivity properties and applications. Attention is paid to structure–property relationships, which ultimately determine the potential use of metal phosphates and derivatives in devices relying on proton conduction. The origin of their conducting properties, including both intrinsic and extrinsic conductivity, is rationalized in terms of distinctive structural features and the presence of specific proton carriers or the factors involved in the formation of extended hydrogen-bond networks. To make the exposition of this large class of proton conductor materials more comprehensive, we group/combine metal phosphates by their metal oxidation state, starting with metal (IV) phosphates and pyrophosphates, considering historical rationales and taking into account the accumulated body of knowledge of these compounds. We highlight the main characteristics of super protonic CsH₂PO₄, its applicability, as well as the affordance of its composite derivatives. We finish by discussing relevant structure–conducting property correlations for divalent and trivalent metal phosphates. Overall, emphasis is placed on materials exhibiting outstanding properties for applications as electrolyte components or single electrolytes in Polymer Electrolyte Membrane Fuel Cells and Intermediate Temperature Fuel Cells.

Covalently linked hydrogen bond donors: The other side of molecular frustration in deep eutectic solvents

In this work, we investigated the effects of a single covalent link between hydrogen bond donor species on the behavior of deep eutectic solvents (DESs) and shed light on the resulting interactions at molecular scale that influence the overall physical nature of the DES system. We have compared sugar-based DES mixtures, 1:2 choline chloride/glucose [DES_(g)] and 1:1 choline chloride/trehalose [DES_(t)]. Trehalose is a disaccharide composed of two glucose units that are connected by an α-1,4-glycosidic bond, thus making it an ideal candidate for comparison with glucose containing DES_(g). The differential scanning calorimetric analysis of these chemically close DES systems revealed significant difference in their phase transition behavior. The DES_(g) exhibited a glass transition temperature of -58 °C and behaved like a fluid at higher temperatures, whereas DES_(t) exhibited marginal phase change behavior at -11 °C and no change in the phase behavior at higher temperatures. The simulations revealed that the presence of the glycosidic bond between sugar units in DES_(t) hindered free movement of sugar units in trehalose, thus reducing the number of interactions with choline chloride compared to free glucose molecules in DES_(g). This was further confirmed using quantum theory of atoms in molecule analysis that involved determination of bond critical points (BCPs) using Laplacian of electron density. The analysis revealed a significantly higher number of BCPs between choline chloride and sugar in DES_(g) compared to DES_(t). The DES_(g) exhibited a higher amount of charge transfer between the choline cation and sugar, and better interaction energy and enthalpy of formation compared to DES_(t). This is a result of the ability of free glucose molecules to completely surround choline chloride in DES_(g) and form a higher number of interactions. The entropy of formation for DES_(t) was slightly higher than that for DES_(g), which is a result of fewer interactions between trehalose and choline chloride. In summary, the presence of the glycosidic bond between the sugar units in trehalose limited their movement, thus resulting in fewer interactions with choline chloride. This limited movement in turn diminishes the ability of the hydrogen bond donor to disrupt the molecular packing within the lattice structure of the hydrogen bond acceptor (and vice versa), a crucial factor that lowers the melting point of DES mixtures. This inability to move due to the presence of the glycosidic bond in trehalose significantly influences the physical state of the DES_(t) system, making it behave like a semi-solid material, whereas DES_(g) behaves like a liquid material at room temperature.

Photochromic inorganic–organic complex derived from low-cost deep eutectic solvents with tunable photocurrent responses and photocatalytic properties

A photochromic inorganic–organic complex |C₁₀H₁₀N₂|[GaF(C₂O₄)₂] derived from low-cost deep-eutectic solvents possesses tunable photocurrent responses and photocatalytic activities.

Ionothermal synthesis of a photoelectroactive titanophosphite with a three-dimensional open-framework

A new titanophosphite open-framework exhibits photovoltaic properties and photocatalytic activity as an n-type semiconductor.

L-proline-based deep eutectic solvents (DESs) for deep catalytic oxidative desulfurization (ODS) of diesel

A series of L-proline-based DESs was prepared through an atom economic reaction between L-proline (L-Pro) and four different kinds of organic acids. The DESs were characterized by Fourier transform infrared spectroscopy (FT-IR), H nuclear magnetic resonance (¹HNMR), cyclic voltammogram (CV) and the Hammett method. The synthesized DESs were used for the oxidative desulfurization and the L-Pro/p-toluenesultonic acid (L-Pro/p-TsOH) system shows the highest catalytic activity that the removal of dibenzothiophene (DBT) reached 99% at 60°C in 2h, which may involve the dual activation of the L-Pro/p-TsOH. The acidity of four different L-proline-based DESs was measured and the results show that it could not simply conclude that the correlation between the acidity of DESs and desulfurization capability was positive or negative. The electrochemical measurements evidences and recycling experiment indicate a good stability performance of L-Pro/p-TsOH in desulfurization. This work will provide a novel and potential method for the deep oxidation desulfurization.

Syntheses and Characterizations of Three Organically Templated Zinc Phosphites with 12-Ring Channels

Three new zinc phosphites, [Hapy]2[Zn3(HPO3)4] (1; apy = 4-aminopyridine), [H2hepip][Zn3(HPO3)4]·(H2O)0.25 (2; hepip = N-(2-hydroxyethyl)piperazine), and [H2tmdab][Zn3(HPO3)4] (3; tmdab = N,N,N′,N′-tetramethyl-1,3-diaminobutane), have been synthesized and characterized by infrared spectroscopy, elemental analysis, thermogravimetric analysis, and powder and single-crystal X-ray diffraction. The frameworks of 1–3 are constructed from 4-connected ZnO4 tetrahedra and 3-connected HPO3 pseudo pyramids with distinct connection mode driven by different organic amine templates. There are 12-membered ring (12-MR) and 8-MR apertures in the (3,4)-connected three-dimensional architecture of 1–3. It is notable that helical chains are observed in the framework of compound 3.

Nanoporous chalcogenides for adsorption and gas separation

A realistic model of porous chalcogenide is used to probe the viability of such a class of materials for adsorption and phase separation applications.

Ferrier reaction in a deep eutectic solvent

A mild and efficient synthesis of 2,3-unsaturated sugar derivatives has been achieved by conducting the Ferrier reaction in a deep eutectic solvent (DES). A wide range of alcohols including primary, secondary, benzylic, and sugar-derived primary alcohols can be used. Advantages include good yields, shorter reaction times and recyclability of DES.

Concise template syntheses of gallium phosphates driven by in situ direct alkylation of aliphatic and aromatic precursors by methanol

In situ template design and generation strategy is applied to synthesize microporous materials. We report five new organically templated gallium phosphates with different structures varying from 1D chain to 2D layer and 3D framework.

Organically templated linear metal sulfites

Six novel organically-templated linear metal sulfite coordination polymers based on Zn(ii) and Mn(ii) ions are synthesized using different amines and the role of H-bonding to provide structures with increased dimensionalities are discussed.

Solving the structures of light-atom compounds with powder charge flipping

While the powder charge flipping (pCF) algorithm has been applied successfully to a variety of inorganic compounds, reports on its application to organic structures, in particular those consisting of light atoms only, are rare. To investigate the reason for this apparent incongruity, a series of light-atom structures were tested using the pCF algorithm implemented in the programSuperflip. The data sets, which covered varying degrees of reflection overlap, had resolutions of approximately 1 Å, and the structures ranged from 40 to 136 atoms per unit cell. Both centrosymmetric and noncentrosymmetric structures were investigated. A modified pCF approach, which was developed in a separate study, was tested on several compounds whose structures could not be solved by applying the basic pCF algorithm inSuperflip. The results show that organic structures with no heavy atoms and low symmetry do indeed test the limits of the pCF algorithm inSuperflip. The study has allowed a few guidelines for approaching such problems to be formulated.

Effects of ionic liquid media on the cation selectivity of uranyl structural units in five new compounds produced using the ionothermal technique

The cation selectivity of several uranyl structural units is examined in the context of five new uranyl compounds produced using the ionothermal synthesis technique.

Electrochemical and density functional theory investigation on high selectivity and sensitivity of exfoliated nano-zirconium phosphate toward lead(II)

A new strategy on the understanding of selective and sensitive identification of Pb(II) using combined experimental and theoretical efforts is described. Amorphous phase formation of exfoliated nano-zirconium phosphate (ZrP) has been prepared via a hydrothermal process and subsequent intercalation reaction. Exfoliated ZrP was used as coating on the electrode surface, and it was found to be selective and sensitive for Pb(II) detection due to its selective adsorption ability. To better and scientifically understand the microscopic adsorption mechanism, density functional theory (DFT) calculations about the details of chemical interactions between heavy metal ions and exfoliated ZrP were carried out at an atomistic level. It is verified that the exfoliated ZrP shows the strongest adsorption capability toward Pb(II) among all heavy metal ions, thereby resulting in selective detection consequently. With our combined experimental and theoretical efforts, we are able to provide a new route to realize the improved selectivity in electrochemical sensing of toxic metal ions.

Optimizing the input parameters for powder charge flipping

Over the past few years, the powder charge-flipping algorithm has proved to be a useful one for structure solution from powder diffraction data, so a semi-systematic study of the effect of the different input parameters on its success has been performed. Two data sets were studied in these tests: a zirconium phosphate framework material and D-ribose. TheSuperflipinput parameters tested were the reflection overlap factor, the intensity repartitioning frequency, the isotropic displacement parameter, the threshold for charge flipping and the number of cycles/runs. By varying the values of these parameters within sensible ranges, an optimized set could be found for the zirconium phosphate case, but no combination of parameters allowed the D-ribose structure to be solved. Reasoning that starting with nonrandom phases might help, an approximate (but incorrect) structure was generated using the direct-space global-optimization method implemented in the programFOX. This structure was then used to calculate initial phase sets forSuperflipby allowing the calculated phases to vary in a random fashion by a user-defined percentage. With such phases and reoptimized input parameters, some fully interpretable solutions with the correct symmetry could be produced, even with fairly low resolution data. Unfortunately, it was not possible to recognize these solutions using theSuperflip Rvalues, so other criteria were sought. Both cluster analyses and maximum entropy calculations of the solutions were performed, and the latter, in particular, look very promising. A set of guidelines derived from these two structures could be applied successfully to a further two inorganic and seven organic structures.

Deep eutectic solvents: syntheses, properties and applications

Within the framework of green chemistry, solvents occupy a strategic place. To be qualified as a green medium, these solvents have to meet different criteria such as availability, non-toxicity, biodegradability, recyclability, flammability, and low price among others. Up to now, the number of available green solvents are rather limited. Here we wish to discuss a new family of ionic fluids, so-called Deep Eutectic Solvents (DES), that are now rapidly emerging in the current literature. A DES is a fluid generally composed of two or three cheap and safe components that are capable of self-association, often through hydrogen bond interactions, to form a eutectic mixture with a melting point lower than that of each individual component. DESs are generally liquid at temperatures lower than 100 °C. These DESs exhibit similar physico-chemical properties to the traditionally used ionic liquids, while being much cheaper and environmentally friendlier. Owing to these remarkable advantages, DESs are now of growing interest in many fields of research. In this review, we report the major contributions of DESs in catalysis, organic synthesis, dissolution and extraction processes, electrochemistry and material chemistry. All works discussed in this review aim at demonstrating that DESs not only allow the design of eco-efficient processes but also open a straightforward access to new chemicals and materials.