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In this study, three supramolecular compounds, namely [Na(18-crown-6)]ReO4 (1), [K(18-crown-6)]ReO4 (2) and [NH4(15-crown-5)2]ReO4 (3) were synthesized and characterized using microanalysis, thermogravimetric, differential scanning calorimetric and powder X-ray diffraction techniques, among others. Herein, 15-crown-5 and 18-crown-6 represent 1,4,7,10,13-pentaoxacyclopentadecane and 1,4,7,10,13,16-hexaoxacyclooctadecane, respectively. Both 1 and 2 experienced one-step reversible phase transition at ∼436 K and ∼360 K, respectively, while 3 underwent three steps of reversible phase transitions at ∼289 K, ∼352 K and ∼380 K. A dielectric anomaly occurred at ∼433 K (∼363 K) for 1 (2), consistent with the temperature obtained from DSC measurement. In the dielectric spectra of 3, anomalies were observed at ∼386 K and ∼433 K, corresponding to two thermal anomalies observed at higher temperatures in the DSC plot. However, there was an absence of dielectric response around 289 K where a thermal anomaly appeared in the DSC plot. The distinct crystal structures, phase transitions and dielectric properties in 1–3 stem from the degree of compatibility between the radii of M+ (Na+, K+ and NH4+) and the ring sizes of crown ethers (18-crown-6 and 15-crown-5). [ABSTRACT FROM AUTHOR]

In this study, two polymorphs of the [1,1′-dibutyl-4,4′-bipyridinium][Ni(mnt)2] salt (1) were synthesized. The dark-green polymorph (designated as 1-g) was prepared under ambient conditions by the rapid precipitation method in aqueous solutions. Subsequently, the red polymorph (labeled as 1-r) was obtained by subjecting 1-g to ultrasonication in MeOH at room temperature. Microanalysis, infrared spectroscopy, thermogravimetry (TG), differential scanning calorimetry (DSC), and powder X-ray diffraction (PXRD) techniques were used to characterize the two polymorphs. Both 1-g and 1-r exhibit structural phase transitions: a reversible phase transition at ∼403 K (∼268 K) upon heating and 384 K (∼252 K) upon cooling for 1-g (1-r) within the temperature range below 473 K. Interestingly, on heating 1-r to 523 K, an irreversible phase transition occurred at about 494 K, resulting in the conversion of 1-r into 1-g. Relative to 1-r, 1-g represents a thermodynamically metastable phase wherein numerous high-energy conformations in butyl chains of cations are confined within the lattice owing to quick precipitation or rapid annealing from higher temperatures. Through variable-temperature single crystal and powder X-ray diffractions, UV-visible spectroscopy, dielectric spectroscopy, and DSC analyses, this study delves into the mechanism underlying phase transitions for each polymorph and the manual transformation between 1-g and 1-r as well. [ABSTRACT FROM AUTHOR]

A Prussian blue analogue was synthesized using biomass leather waste as a precursor by doping with Co2+ ions. This material, demonstrates good performance in both the oxygen reduction reaction and oxygen evolution reaction, and exhibits excellent charge–discharge performance and stability in zinc–air batteries. [ABSTRACT FROM AUTHOR]

The supramolecular crystals, Mn(15-crown-5)(MnCl4)(DMF), (1; 15-crown-5 = 1,4,7,10,13-pentaoxacyclopentadecane), were synthesized via a self-assembly strategy under ambient conditions. Comprehensive characterization of the crystals involved microanalysis for C, H, and N elements, thermogravimetric (TG) analysis, differential scanning calorimetry (DSC) and single-crystal X-ray diffraction techniques. The results reveal that 1 undergoes a two-step thermotropic and isostructural phase transition at around 217 K and 351 K upon heating. All three phases belong to the same space group (P212121) with analogous cell parameters. These two phase transitions primarily involve the thermally activated ring rotational dynamics of the 15-crown-5 molecule, with only the transition at ca. 351 K being associated with a dielectric anomaly. 1 exhibits intense luminescence with a peak at ∼600 nm and a high quantum yield of 68%. The mechanisms underlying this intense luminescence are likely linked to low-symmetry ligand fields. Additionally, 1 displays phase transition-induced luminescence enhancement behavior, and the possible mechanism is further discussed. [ABSTRACT FROM AUTHOR]

Crown ethers demonstrate significant conformational flexibility and rotational symmetry, rendering them invaluable in the realms of supramolecular chemistry and crystal engineering. These unique natures facilitate the construction of supramolecular crystals of crown ethers, characterized by disorder‐order phase transitions, imparts unique properties that hold promise for diverse applications across multiple fields. In this study, four supramolecular compounds, namely [Na(15‐crown‐5)]BF4 (1), [Na(18‐crown‐6)]BF4⋅H2O (2), [K(15‐crown‐5)]BF4 (3) and [K(18‐crown‐6)]BF4⋅H2O (4) were synthesized and characterized by microanalysis, thermogravimetric analysis, differential scanning calorimetry and powder X‐ray diffraction techniques. Herein, 15‐crown‐5 and 18‐crown‐6 correspond to 1,4,7,10,13‐pentaoxacyclopentadecane and 1,4,7,10,13,16‐hexaoxacyclooctadecane, respectively. It was observed that the crystal structure, phase transition, and dielectric properties of these supramolecular compounds are significantly influenced by the size of the crown‐ether rings. The research extensively discussed the correlation between the coordination mode of metal ions of K+ or Na+ with crown ethers, the compatibility between metal ions and crown‐ether rings in terms of size, and the effects of crown‐ether disorder on dielectric permittivity during phase transitions. Our discoveries hold significant implications for the design and development of crown‐ether supramolecular functional materials. [ABSTRACT FROM AUTHOR]

Solid-state electrolytes have demonstrated significant potential in achieving safer Li-metal batteries with minimal negative impact on battery performance, and in some cases, even enhancing electrochemical performance. Nonetheless, a primary obstacle lies in the advancement of cutting-edge solid-state electrolytes that exhibit rapid Li+-ion conduction, high electrochemical stability, and enhanced safety. Covalent organic frameworks (COFs) have excellent organophilicity and open channels, providing a unique feature of being an 'organic solution sponge' that allows for the absorption and release of liquid organic electrolytes, offering a useful platform for developing fast ion-conducting solid-state electrolytes. This study focuses on a benzimidazole-linked COF (PBI-COF), which acts as an organic liquid electrolyte sponge, by encapsulating propylene carbonate (PC) solution of LiBF4 into PBI-COF channels, to produce a superionic conducting solid-state electrolyte (LiBF4/PC@PBI-COF) with an ionic conductivity above 10−3 S cm−1 and a Li+-ion transference number of 0.58 at ambient temperature, and excellent flame retardancy. Our study presents a novel approach to design safe solid-state alkaline-metal ion electrolytes for use in all-solid-state alkaline-metal batteries. [ABSTRACT FROM AUTHOR]

Aqueous proton batteries (APBs) are regarded as one of the most promising energy storage devices for the next-generation batteries owing to their high safety, high power density and environmental friendliness, while the study of their electrolytes is still in the infancy regarding metal-based batteries. Herein, we present a double-network hydrogel as a quasi-solid-state electrolyte in a proton battery. Sulfonated poly(ether–ether–ketone) and an ethylene glycol/water solvent are incorporated within the poly(vinyl alcohol) hydrogel network to enhance the mechanical properties, resulting in a tensile strength of 4.37 MPa and a toughness strain of 663%. This composite also exhibits remarkable proton conductivity (8.8 × 10−3/1.1 × 10−1 S cm−1 at −35/70 °C, ambient humidity) and low temperature tolerance (−50 °C). A quasi-solid-state proton "rocking-chair" battery demonstrates stable cycling and high rate capability (77% capacity retention after 500 cycles at 1 A g−1 at 25 °C and 95% capacity retention rate over 100 cycles at −20 °C). This study provides a new possible practical application of hydrogel as a proton battery electrolyte, which could advance the development of proton electrochemical devices. [ABSTRACT FROM AUTHOR]

Two sets of 1D/2D lanthanide coordination polymers with formulas of Ln(oqa)3·2H2O [Hoqa = 2-(4-oxoquinolin-1(4H)-yl) acetic acid, Ln = Dy (1), Yb (2)] and Ln(oaa)2(HCOO)(H2O) [Hoaa = 2-(9-oxoacridin-10(9H)-yl) acetic acid, Ln = Dy (3), Yb (4)] have been synthesized and their physical properties were investigated. All four complexes are constructed from seven-coordinate lanthanide ions and corresponding organic linkers. The lanthanide ions in 1 and 2 adopt a pentagonal bipyramid coordination geometry, whereas the coordination geometry of lanthanide ions in 3 and 4 can be described as a capped octahedron. Slow magnetic relaxation behaviors were observed in these four products at a zero/non-zero static magnetic field. Complexes 1, 2 and 4 exhibit the characteristic emission of Ln(III) ions, whereas complex 3 shows ligand-based emission. Bright yellow light emission was also observed when a voltage was applied, demonstrating the potential of 1 for application in light-emitting diodes (LEDs). Compounds 3 and 4 are the first examples of lanthanide complexes based on Hoaa ligands. [ABSTRACT FROM AUTHOR]