Stand up and be tested: Self-standing membranes of a neat organic cage are reported here. The cage membranes showed a remarkably good mechanical resistance, which made them suitable for gas-permeation tests. This study pointed the possibility of using a simple organic cage molecule to achieve a molecular material with features that are generally observed with polymeric membranes.

Abstract

The synthesis and characterization of a novel film-forming organic cage and of its smaller analogue are here described. While the small cage produced single crystals suitable for X-ray diffraction studies, the large one was isolated as a dense film. Due to its remarkable film-forming properties, this latter cage could be solution processed into transparent thin-layer films and mechanically stable dense self-standing membranes of controllable thickness. Thanks to these peculiar features, the membranes were also successfully tested for gas permeation, reporting a behavior similar to that found with stiff glassy polymers such as polymers of intrinsic microporosity or polyimides. Given the growing interest in the development of molecular-based membranes, for example for separation technologies and functional coatings, the properties of this organic cage were investigated by thorough analysis of their structural, thermal, mechanical and gas transport properties, and by detailed atomistic simulations.

Seven-exo - dig hydrocarboxylation of internal alkynes was developed with gold-zinc bimetallic catalysts activating alkyne-tethered carboxylic acids via cooperative action of the gold and zinc sites. N-Substituents of the NHC ligand for gold complexes significantly affected their catalytic activities, in which a gold complex with a 2,6-dibenzhydryl-4-methylphenyl substituent served as the most effective catalyst for the seven-membered ring formation.

Abstract

Seven-exo-dig hydrocarboxylation of nonactivated internal alkynes with conformationally flexible linker chains was achieved with cooperative gold-zinc catalysts composed of an imidazo[1,5-a]pyridinylidene ligand including a bipyridine coordination site at the C5 position. A proximity effect of the gold and zinc sites was essential for their high catalytic activity, in which the internal alkyne activated by the cationic gold species was attacked by the carboxylic acid deprotonated by the basic zinc site. Using a gold(I)-complex with a bulky aromatic N-substituent, 2,6-dibenzhydryl-4-methylphenyl group, for the NHC ligand facilitated seven-membered ring formation while minimizing intermolecular hydrocarboxylation as an undesired side reaction. The reaction mechanism was investigated by quantum chemical calculations.

A CoP−FeP heterostructure catalyst with abundant P vacancies (Vp−CoP−FeP/NF) on nickel foam is constructed through impregnation and phosphorization. It demonstrates excellent hydrogen evolution performance and has practical application prospects in high-current overall water splitting. The catalyst‘s unique hierarchical nanosheet structure, plentiful P vacancies and synergistic effect of CoP and FeP accelerate HER kinetics, resulting in its superior performance.

Abstract

The development of hydrogen evolution reaction (HER) catalysts with high performance under large current density is still a challenge. Introducing P vacancies in heterostructure is an appealing strategy to enhance HER kinetics. This study investigates a CoP−FeP heterostructure catalyst with abundant P vacancies (Vp−CoP−FeP/NF) on nickel foam (NF), which was prepared using dipping and phosphating treatment. The optimized Vp−CoP−FeP catalyst exerted prominent HER catalytic capability, requiring an ultra-low overpotential (58 mV @ 10 mA cm⁻²) and displaying robust durability (50 h @ 200 mA cm⁻²) in 1.0 M KOH solution. Furthermore, the catalyst demonstrated superior overall water splitting activity as cathode, demanding only cell voltage of 1.76 V at 200 mA cm⁻², outperforming Pt/C/NF⁽⁻⁾ || RuO₂/NF⁽⁺⁾. The catalyst‘s outstanding performance can be attributed to the hierarchical structure of porous nanosheets, abundant P vacancies, and synergistic effect between CoP and FeP components, which promote water dissociation and H* adsorption and desorption, thereby synergically accelerating HER kinetics and enhancing HER activity. This study demonstrates the potential of HER catalysts with phosphorus-rich vacancies that can work under industrial-scale current density, highlighting the importance of developing durable and efficient catalysts for hydrogen production.

[4+2] condensation reaction of diphosphene [(^ClIm^Dipp)P₂(Dipp)]OTf and diphosphanide [(^ClIm^Dipp)P₂(Dipp)Cl] with the cyclo-P₄ cobalt complex [K(18c-6)][(PHDI)Co(η⁴-cyclo-P₄)] forms a CoP₆ complex, featuring an unusual hexaphosphido ligand composed of a cyclo-P₅ ring and an exocyclic (^ClIm^Dipp)P moiety. ³¹P NMR spectroscopic studies reveal that at ambient temperature, this CoP₆ complex undergoes disproportionation into more stable CoP₇ and CoP₅ complexes.

Abstract

The reaction between diphosphorus derivatives [(^ClIm^Dipp)P₂(Dipp)]OTf (1[OTf]) and [(^ClIm^Dipp)P₂(Dipp)Cl] (1[Cl]) with the cyclotetraphosphido cobalt complex [K(18c-6)][(PHDI)Co(η⁴-cyclo-P₄)] (2) leads to the formation of complex [(PHDI)Co{η⁴-cyclo-P₆(Dipp)(^ClIm^Dipp)}] (3), which features an unusual hexaphosphido ligand [^ClIm^Dipp=4,5-dichloro-1,3-bis(2,6-diisopropylphenyl)imidazol-2-yl, Dipp=2,6-diisopropylphenyl, 18c-6=18-crown-6, PHDI=bis(2,6-diisopropylphenyl)phenanthrene-9,10-diimine]. Complex 3 was obtained as a crystalline material with a moderate yield at low temperature. Upon exposure to ambient temperature, compound 3 slowly transforms into two other compounds, [K(18c-6)][(PHDI)Co(η⁴-P₇Dipp)] (4) and [(PHDI)Co{cyclo-P₅(^ClIm^Dipp)}] (5). The novel complexes 3–5 were characterized using multinuclear NMR spectroscopy and single-crystal X-ray diffraction. To shed light on the formation of these compounds, a proposed mechanism based on ³¹P NMR monitoring studies is presented.

Size of liquid exfoliated MoS₂ nanosheets plays a crucial role in determining nanoparticle decoration densities in the spontaneous reduction of chloroplatinic acid into ultrasmall Pt nanoparticles.

Abstract

Liquid exfoliation can be considered as a viable approach for the scalable production of 2D materials due to its various benefits, although the polydispersity in the obtained nanosheet size hinders their straightforward incorporation. Size-separation can help alleviate these concerns, however a correlation between nanosheet size and property needs to be established to bring about size-specific applicability. Herein, size-selected aqueous nanosheet dispersions have been obtained via centrifugation-based protocols, and their chemical activity in the spontaneous reduction of chloroplatinic acid is investigated. Growth of ultrasmall Pt nanoparticles was achieved on nanosheet surfaces without a need for reducing agents, and stark differences in the nanoparticle coverage were observed as a function of nanosheet size. Defects in the nanosheets were probed via Raman spectroscopy, and correlated to the observed size-activity. Additionally, the effect of reaction temperature during synthesis was investigated. The electrochemical activity of the ultrasmall Pt nanoparticle decorated MoS₂ nanosheets was evaluated for the hydrogen evolution reaction, and enhancement in performance was observed with nanosheet size, and nanoparticle decoration density. These findings shine light on the significance of nanosheet size in controlling spontaneous reduction reactions, and provide a deeper insight to intrinsic properties of liquid exfoliated nanosheets.

Click reaction has been used to make covalent organic cages with tetraphenyl ethylene and tetrabiphenyl ethylene AIEgens. The emissive cages exhibit enhanced aggregation induced emission and detect picric acid in nanomolar quantity in aqueous solutions.

Abstract

This study reports the synthesis of cofacial organic cage molecules containing aggregation-induced emissive (AIE) luminogens (AIEgens) through four-fold Cu(I)-catalyzed azide–alkyne cycloaddition (CuAAC) “click” reactions. The shorter AIEgen, tetraphenylethylene (TPE), afforded two orientational isomers (TPE-CC-1A and TPE-CC-1B). The longer AIEgen, tetrabiphenylethylene (TBPE), afforded a single isomer (TBPE-CC-2). The click reaction employed is irreversible, yet it yielded remarkable four-fold click products above 40 %. The phenyl rings around the ethylene core generate propeller-shaped chirality owing to their orientation, which influences the chirality of the resulting cages. The shorter cages are a mixture of PP/MM isomers, while the longer ones are a mixture of PM/MP isomers, as evidenced by their x-ray structures. The newly synthesized cage molecules are emissive even in dilute solutions (THF) and exhibit enhanced AIE upon the addition of water. The aggregated cage molecules in aqueous solution exhibit turn-off emission sensing of nitroaromatic explosives, with selectivity to picric acid in the 25–38 nanomolar detection range.

A ferrocene-based tetradentate ligand featured with modular synthesis and rigid skeleton was reported. Its iron(II) complex facilitates asymmetric direct hydrogenation of ketones without the participation of extra strong-field ligand such as CO and isocyanide. Various chiral alcohols including the intermediate for montelukast could be prepared with satisfactory yields and enantioinduction.

Abstract

We herein reported the design and synthesis of a ferrocene-based tetradentate ligand that is featured with modular synthesis and rigid skeleton. Its iron(II) complex facilitates asymmetric direct hydrogenation of ketones without the participation of extra strong-field ligand such as CO and isocyanide. Hydride donor lithium aluminum hydride (LAH) converted non-reactive Fe(II) species to reactive Fe(II) hydride species. With this catalyst, various chiral alcohols including the intermediate for montelukast could be prepared with satisfactory yields and enantioinduction.

Detection of Ba²⁺ : Herein, we report on a highly Ba²⁺-selective, Ba²⁺-sensitive and pH independent fluorescent probe with a high photostability in water (cf. TOC). This fluorescent probe is equipped with a benzo-21-crown-7 as a highly selective Ba²⁺ ionophore and a tetramethylated BODIPY fluorophore.

Abstract

Herein, we report on highly Ba²⁺ selective fluorescence sensing in water by a fluorescent probe consisting of a benzo-21-crown-7 as a Ba²⁺ binding unit (ionophore) and a tetramethylated BODIPY fluorophore as a fluorescence reporter. This fluorescent probe showed a Ba²⁺ induced fluorescence enhancement (FE) by a factor of 12±1 independently of the pH value and a high Ba²⁺ sensitivity with a limit of detection (LOD) of (17.2±0.3) μM. Moreover, a second fluorescent probe consisting of the same BODIPY fluorophore, but a benzo-18-crown-6 as a cation-responsive binding moiety, showed an even higher FE upon Ba²⁺ complexation by a factor of 85±3 and a lower LOD of (13±3) μM albeit a lower Ba²⁺ selectivity. The fluorescence sensing mechanism of Ba²⁺ was further investigated by time-resolved fluorescence as well as transient absorption spectroscopy (TAS) and it turned out that within these probes a blocking of a photoinduced electron transfer (PET) by Ba²⁺ is very likely responsible for the FE.

Sulfur trioxide acts as a strong oxidizer towards halides as well as pseudohalides. Therefore, reactions of sulfur trioxide with cyanide anions do usually not lead to the formation of cyanido-sulfates anion but to oxidation of the cyanide ion. This problem can be avoided if a sulfur trioxide-pyridine complex is used instead of neat sulfur trioxide. In this way, the oxidation power is sufficiently reduced, and the pyridine molecule can be replaced by the cyanide anion under formation of the cyanido-sulfate anion, SO₃CN⁻. Thus sulfur trioxide gets rid of the badly smelling pyridine molecule, however, at the expense of gaining the toxic cyanide anion. More information can be found in the Research Article by M. S. Wickleder and co-workers (DOI: 10.1002/chem.202301761).