Chemistry - A European Journal最新文献

Nitrate reduction reaction (NO3RR) involves an 8-electron transfer process and competes with the hydrogen evolution reaction process, resulting in lower yields and Faraday efficiency (FE) in the process of NH3 synthesis. Especially, Cu-based catalysts (Cu0 and Cu+) have been investigated in the field of NO3RR due to the energy levels of d-orbital and the least unoccupied molecular orbital (LUMO) π* of nitrate's orbital. Based on the above, we synthesized a Cu-based compound containing Cu3N (Cu+) through a simple one-step pyrolysis method, applied it to electrocatalytic NO3RR, and tested the performance of the Zn-NO3- battery. Through various characterization analyses, Cu-based catalysts (Cu+) are the key active sites in reduction reactions, making Cu3N a potential catalyst for ammonia synthesis. The research results indicate the application of Cu3N catalyst in NO3RR shows the best NH3 yield of 173.7 μmol h-1 cm-2, with FENH3 reaching 91.0% at -0.3 V vs. RHE, which is much higher than that of Cu catalyst without N. In addition, the Zn-NO3- battery based on Cu3N electrode also exhibits an NH3 yield of 39.8 μmol h-1 cm-2, 63.0% FENH3, and a power density of 2.7 mW cm-2, as well as stable cycling charge-discharge stability for 5 hours.

We report a general remote tribromo- and trichloromethylation process using CBr4 and CBrCl3 as ready available sources of trihalomethyl radicals. This method operates under mild and metal-free photocatalyzed conditions and enables the access to γ-trihalomethylated enals with complete regioselectivity in up to 71% isolated yield. Importantly, this protocol is easily adapted to the selective one-pot synthesis of the corresponding γ-dihalomethylidenated enals in up to 49% overall yield. Mechanistic studies are in favor of a radical chain propagation initiated by an oxidative quenching of the photocatalyst.

Polymorphism and its screening to select the best-performing form is in high demand. In low molecular weight organogels (LMWG), gelators are designed as they contain flexible groups, functionalities capable of varied H-bonding, and increased the potential to show polymorphism. We synthesized a bis-urea based LMWG G1 and isolated three distinct polymorphic phases (Form I, II, and III). G1 polymorphs showed noticeable differences in solubility; precisely, Form I is highly soluble compared to the other two. Gel screening was carried out for all three polymorphs using different stimuli like heat-cool, sonication, shaking, and grinding. Among the polymorphs, Form I was found to have better gelling ability which was reflected by the solvent scope, thermal stability (gel-sol transition temperature Tgel), minimum gelator concentration (M.G.C.), stimuli-responsiveness, morphology, and rheological properties. The differences in their gelation performance among the three polymorphs are associated with their solubility parameter. Stimuli like sonication, shaking, and grinding triggered Form I to form a gel.  Form II and III responded to heat-cool stimuli only due to poor solubility. Therefore, it is noted crucial to add polymorph screening as an integral part of the gel synthesis to avoid problems associated with reproducibility in the gel prophecy of LMWG systems.

Biofuel cells have become an interesting alternative for the design of sustainable energy conversion systems with multiple applications ranging from biosensing and bioelectronics to autonomously moving devices. However, as an electrochemical system, their performance is intimately related to mass transport conditions. In this work, the magnetohydrodynamic (MHD) effect is studied as an easy and straightforward alternative to enhance the performance of a biofuel cell based on the enzymes glucose oxidase (GOx) and bilirubin oxidase (BOD). The synergetic effect between the electric and ionic currents, produced by the enzymatic redox reactions, and a magnetic field orthogonal to the surface of the electrodes, leads to the formation of localized magnetohydrodynamic vortexes. Such an integrated convective regime generates an increase of the bioelectrocatalytic current and its concomitant power output in the presence of the external magnetic field. In addition, by fine-tuning the spatial arrangement of the anode and cathode, it is possible to benefit from the sum of anodic and cathodic MHD vortexes, leading to an enhanced power output of up to 300%.

The electrochemiluminescence (ECL) of ruthenium(II) tris(2,2'-bipyridyl) (Ru(bpy)32+) with tri-n-propylamine (TPrA) as the good coreactant can be unexpectedly enhanced by a weak coreactant, such as triethanolamine (TEOA). First, the intensity of ECL emitted by Ru(bpy)32+/TPrA can be remarkably amplified by 10.8-fold after adding some amount of TEOA. Moreover, the ECL layer thickness, measured by self-interference spectroscopy, is also doubled. The enhancement far exceeding the superposition of respective contribution of TPrA and TEOA was elucidated by a "chemical oxidation mechanism", in which TEOA+• acts as a chemical enhancer to oxidize TPrA in solution and to accelerate significantly the ECL reaction kinetics. This mechanism was proved by single-photon counting experiment and finite element simulations. In addition, the dual-coreactants strategy works well not only in solution with freely diffusive Ru(bpy)32+, but also on Ru(bpy)32+-functionalized microbeads, suggesting that ethanolamines could act as cheap, easily available and low-background enhancers for ECL-based bioanalysis and microscopy.

The structural variability and chemical stability of metal phosphonates under harsh conditions are attractive attributes that have drawn considerable attention in recent years. As the needs for more sustainable solutions rise, the demand for novel and tolerant materials also increases. Thus, herein we report, for the first time, the synthesis of a novel diphosphonic organic linker named pyrazole diphenyl phosphonate (PZDP), envisioning the fabrication of durable metal phosphonates. In view of this, a series of M-PZDP materials (M = Ca, Sr, Ba, Zn and Co) were synthesized employing either solvothermal or hydrothermal methods. The crystal structures of the Ca, Sr, Zn, and Co derivatives were determined revealing a 2D-pillared architecture. Zn-PZDP is an anionic framework with dimethylammonium cations. The Co-PZDP compound was tested as a heterogeneous catalyst in olefin epoxidation employing molecular oxygen.

We have developed a family of dinuclear complexes using 2,7-disubstituted 1,8-naphthalenediol ligands that bind by molecular recognition to two neighboring phosphate diesters of the DNA backbone with the dinuclear CuII and NiII complexes exhibiting a severe cytotoxicity for human cancer cells. To increase the binding affinity, we intended to synthesize the corresponding dinuclear FeIII complex. Surprisingly, we obtained a tetranuclear FeIII perylene-based complex instead of the expected dinuclear FeIII naphthalene-based complex. In order to establish a rational and reproducible synthesis, we carefully analyzed this reaction. This revealed a multistep oxidative cascade reaction including the pre-coordination of FeII ions in the N3-binding pockets, the Lewis-acid assisted MOM-deprotection of the pre-ligand by the pre-oriented FeII ions, two oxidative aromatic C-C coupling reactions, oxidation of the perylene-based backbone and of FeII to FeIII. The careful analysis of bond lengths, HOMA indices (harmonic oscillation model of aromaticity), FTIR and UV-Vis-NIR spectra supported by DFT calculations reveals the presence of an aromatic 18-electron oxidized perylenequinone ligand backbone. In summary, a multistep cascade reaction involving in total a 10-electron oxidation has been established for the straight-forward synthesis of an unprecedented perylenequinone-based ligand system.

We present a series of six hypervalent bismuth complexes Bi(R1PDPR2)X bearing ligands characterized by the pyridine-2,6-bis(pyrrolide) (PDP) structural motif. While bismuth holds considerable potential for facilitating efficient intersystem crossing (ISC), reports on phosphorescent molecular bismuth complexes are still scarce and mostly based on systems that exhibit inter‑ or intraligand charge transfer character of their optical excitations. Herein, the UV/vis absorptive, luminescent, and electrochemical properties of complexes Bi(R1PDPR2)X are explored, where the substituents R1 and R2, as well as the halide ligand X are varied. These compounds are characterized by an intense HOMO®LUMO transition of mixed ligand-to-metal charge transfer (LMCT) and interligand charge transfer (LL'CT) character, as shown by time-dependent density functional theory (TD-DFT) calculations. At 77 K in a 2-MeTHF matrix, these compounds exhibit red, long-lived phosphorescence with lifetimes ranging from 671 to 20 µs. Cyclic voltammetry measurements and TD-DFT calculations show that the substituents influence HOMO and LUMO energies to almost equal extent, resulting in nearly constant emission wavelengths throughout this series. Single-crystal X-ray diffraction studies of four of the six complexes exemplify the inherent Lewis acidity of the coordinated Bi3+ ion, in spite of its hypervalency.

A Pd(II)-catalyzed non-template synthesis of furo[2,3-b]pyrrolo[2,3-d]pyridines from b-ketodinitriles and buta-1,3-diynes has been accomplished via dual annulative cyclization. The participation of both the nitrile (-CN) groups led to the concurrent construction of three heterocycles viz. furan, pyrrole, and pyridine forming C-C, C=C, C-O, C-N, and C=N bonds in one pot. The synthetic utility of the protocol was further demonstrated through a few post-synthetic manipulations.

Two novel 1,10-phenanthroline-2,9-diamide ligands were constructed based on 2-phenylpyrrolidine and obtained as pure diastereomers. These ligands demonstrated advanced properties in liquid-liquid extraction tests. They revealed high efficiency of americium(III) extraction alongside with the record values of selectivity in the separation of americium from light lanthanides from strongly acidic media. An abrupt increase of extraction efficiency when moving along the lanthanide series from lanthanum to lutetium was observed. The examination of the extraction behavior of pure diastereomeric forms revealed noticeable differences in their selectivity while maintaining the overall extraction trend. The explanation of the discovered patterns was elucidated by a comprehensive study of the ability of the ligands to bind lanthanide nitrates in solutions. All the data collected (UV-vis and NMR titration, X-ray analysis of resulting complexes, solvation numbers estimation) were supported by quantum chemical calculation. These data clearly indicated that in case of light lanthanides the formation of 1:1 complexes is most preferable. In the same time, complexes with heavy lanthanides, such as ytterbium and lutetium, exist as ionic pairs which may consist of [L2M]z+ cations counterbalanced by metallates anions, which may result in formation of unusual composition species L2M2 or even L4M5 clusters.