Chemistry - A European Journal最新文献

The catalytic performance of Mo-based transition-metal-dichalcogenide (TMD) monolayers is intrinsically tied to their physicochemical properties. However, the limited chemical diversity among these materials constrains their versatility for key catalytic processes, including carbon dioxide (CRR), nitrogen (NRR), and oxygen (ORR) reduction reactions. This study employs density functional theory (DFT) calculations to investigate the impact of chalcogen vacancies on the properties of MoS2, MoSe2, and MoTe2, focusing on the adsorption behaviors of CO, NO, and NO2. The findings reveal that chalcogen vacancies not only enhance surface reactivity but also impart distinctive physicochemical characteristics to each TMD. These effects arise from intrinsic bonding differences, resulting in distinct charge availability at exposed Mo atoms and variations in vacancy dimensions, which shape specific surface interactions. Hence, while adsorption differences between pristine surfaces are generally negligible for catalysis, vacancies amplify them by over an order of magnitude, resulting in pronounced material-specific behaviors. Moreover, varying vacancy dimensions affect how species incorporate into defects, further enhancing the differences. These characteristics unlock substantial potential of TMD sheets for distinct surface chemistries, transforming them from relatively similar to markedly different as defect density rises. Consequently, our findings provide fundamental insights for tailoring these materials toward applications in electro- and photocatalysis.

Hetero-tetra-metallic complexes, FeNOCuLnCo (Ln = Gd, Tb, Dy), combining magnetic properties and photo-isomerism, were obtained through the rational assembly of the photo-switching nitroprusside anion FeNO with new magnetic Schiff base CuLnCo precursors. Herein, we describe the synthesis and characterisation of these compounds followed by a demonstration of their multifunctional character. Particularly noteworthy is the FeNOCuTbCo complex, one of the few examples of a photo-isomerizable single-molecule magnet (SMM) and a significant first step toward achieving synergistic properties.

Alstrostine A and isoalstrostine A are monoterpenoid indole alkaloid glycosides with unique structures found in the plant families Apocynaceae and Rubiaceae. With molecular weights exceeding 900, nine chiral centers (excluding sugar rings), and complex fused-ring structures, the structural elucidation of these molecules using spectral analysis is highly challenging. Therefore, their structural identification through total synthesis is important in both natural product chemistry and synthetic organic chemistry. In this study, we successfully accomplished the first asymmetric total syntheses of these alkaloids in 18 or 19 steps. A key synthetic feature was a two- or three-component coupling reaction between secologanin and a pyrrolidinoindoline moiety based on our proposed biosynthetic pathway. This approach enabled the synthesis of all isomers of the pyrrolidinoindoline ring, which constitutes the upper fragment of the alstrostines, and allowed us to revise the stereochemistry of alstrostine A. Additionally, a compound previously isolated as alstrostine A from Palicourea luxurians (Rubiaceae) was successfully reidentified and renamed as epialstrostine A.

Macrocyclic complexes with spatially-arranged coordination sites have the potential to create unique supramolecular systems that combine the precise switching of self-assembled structures with the coordinative recognition of specific molecules. We now report a macrocyclic trinuclear Zn complex that undergoes a unique dimerization by molecular binding from the outside. The multinuclear complex was synthesized from a trispap ligand, a designed macrocyclic trimer of an N,N,O-type tridentate chelating unit pap. This macrocyclic ligand is capable of fixing the metal centers and retaining their exchangeable coordination sites. The macrocyclic trimer reacts with zinc acetate to form the trinuclear complex, in which the coordination sites of the three zinc atoms are aligned perpendicular to the macrocyclic plane and capped with the acetates. Subsequently, phosphate anion, PO43-, coordinates from one side of the macrocycle in a tripodal manner. This phosphate binding produced an electrically-neutral complex moiety with available coordination sites on the other side of the macrocycle which leads to the formation of the coordination-bridged dimer.

To explore intramolecular charge-transfer (ICT) pathways in three-redox-center organic mixed-valence (MV) radical cation, a tris(triarylamine) (TTA), in which three triarylamine (TA) redox-active centers are connected in a side-by-side fashion via 1,2,3-benzenetriyl bridging unit, has been newly synthesized. The MV state of the TTA radical cation has been investigated by a combination of experimental and theoretical methods, and the ICT pathway between three redox-active centers has been revealed. The intervalence CT (IVCT) band analysis gave an electronic coupling value comparable to the ortho-phenylene-bridged bis(triarylamine) radical cation. Dynamic electron spin resonance studies clarified that the TTA radical cation was a nondegenerate MV system exhibiting ICT between the central TA and the peripheral TAs through the ortho-phenylene-bridge.

The design of well-defined assemblies of chiral molecules is a prerequisite for numerous applications, such as chirality-induced spin selectivity (CISS). In this context, tripodal molecular films bear the advantage of better control of molecular orientation and alignment than analogous monopodal systems. To this end, we report on the synthesis and assembly property of C3 chiral syn-5,10,15-truxene triacetic acid. (S,S,S) and (R,R,R) enantiomers were isolated and adsorbed on underpotential deposited Ag(111)/Au/mica both individually and as a racemate. The enantiomers form a densely packed and well-ordered structure (including the azimuthal alignment), even though with small sizes of individual domains. The molecules adsorb predominantly in tripodal configuration, with all three docking groups bound to the substrate as carboxylates in a bidentate fashion. The truxene backbone is then oriented parallel to the substrate surface but the fluorene blades are twisted to some extent. The racemate monolayer turned out to be less densely packed and less well-ordered compared to the films of individual enantiomers, which underlines the fact that uniform chirality is primarily important for molecular ordering of the truxenes. We hope that the designed system will be useful in the context of CISS and stimulate further activities regarding chiral tripods.

Diboron reagents are known for their ability to promote the deoxygenation of amine or pyridine oxides, nitroarenes, and nitrones through the formation of B-O-B bonds. In this study, we have investigated the potential of diboron reagents to induce N-N bond cleavage in hydrazines, N-nitrosamines and azides. Our findings show that the combination of B2nep2 as diboron source and KOMe as a Lewis base can effectively promote the N-N cleavage of a wide variety of substrates. For hydrazines and nitrosamines, the presence of an aryl group is essential for the reaction to proceed, probably due to a better stabilization of the negative charge developed during N-N bond cleavage. Both types of azides, aromatic and aliphatic, are easily reduced, and the resulting amines can be in situ converted into the corresponding amides by simple treatment with a carboxylic acid. Experimental and theoretical calculations suggest a non-radical mechanism, with concerted B-B and N-N bond cleavage in the case of hydrazines and azides, and a stepwise mechanism in the case of N-nitrosamines, where deoxygenation occurs as the first step, involving the formation of an N-nitrene intermediate.

The utilization of visible light to split water into H₂ and O₂ offers a promising solution to address the escalating global energy crisis and environmental pollution. Compared to conventional three-dimensional (3D) photocatalysts, anisotropic two-dimensional (2D) materials exhibit enhanced photocatalytic activity due to their ultrahigh surface area, reduced charge migration distance, and improved efficiency. In this study, we employ a swarm-intelligence search combined with density functional theory (DFT) calculations to propose a novel series of stable 2D phosphorus sulfides, PₓSᵧ (x, y = 1-6), as promising candidates for photocatalytic water splitting.  The P3S-I monolayer exhibits an optimal bandgap (2.485 eV), appropriate band edge positions (-3.52 eV for CBM and -6.00 eV for VBM at the HSE06 level), high carrier mobility (3246.85 cm² V⁻¹ s⁻¹ for μₑ along the y-direction and 1039.80 cm² V⁻¹ s⁻¹ for μₕ along the x-direction), and strong optical absorption coefficients (exceeding 1 × 10⁵ cm⁻¹ within the visible spectrum). Notably, the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) are facilitated concurrently at the P and S sites, respectively, driven exclusively by photogenerated electrons and holes.

Radioactive iodine capture is a major concern for nuclear power generation and environmental protection. Many metal-organic frameworks (MOFs) have been designed and synthesized to adsorb iodine from vapor or solution, but most of them exhibited unsatisfactory iodine uptake performance because of the insufficiency of adsorption sites. Herein, we chose 1-vinyl-3-ethylimidazolium bromide (VIMB) and 1,2-diaminocyclohexane (DACH) with rich-electron group as guest molecules, respectively, and encapsulated them into a three-dimensional Zn-based MOF Zn-BINOL with large 1D channel (BINOL = (R)-2,2'-diethoxy-1,1'-binaphthyl-4,4',6,6'-tetrabenzoate), as a result, two efficient iodine adsorbents VIMB@Zn-BINOL and DACH@Zn-BINOL were obtained. The equilibrium iodine vapor adsorption amounts of them are 1448 and 1680 mg/g at 75 ºC, being about 2.1 and 2.4 times more than that of Zn-BINOL, respectively. This work will provide more synthetic methods on design and preparation of iodine adsorbents with good adsorption capacity.

In molecules with central chiral centers functionalized with aryl groups, the rotation of the single bond between the aryl group and the central chiral center may be hindered. Enantioconvergent alkylation reactions of racemic diastereomers to construct all-carbon quaternary stereocenters resulting in easing of the rotation around the axes are described. We demonstrated that the rotation of the bond between a central chiral carbon center and a dihydrobenzofuranone can be tuned by selection of either a tertiary carbon bearing a hydrogen or a quaternary carbon at the central chiral center. The products have the benefits of a central chiral center and a flexibly rotatable bond, which can facilitate interactions with other molecules.