Analytical Chemistry
DOI: 10.1021/acs.analchem.3c02348
Monthly Archives: September 2023
Supercritical CO2 Mediated Multi‐scale Structural Engineering in PdCu/C for Boosting Electrocatalytic Formic Acid Oxidation
We found that supercritical carbon dioxide could mediate multi-scale structure engineering in PdCu/C nanocatalysts, including defect engineering, phase engineering, morphology engineering and substrate engineering. The achieved PdCu/C with amorphous surface, BCC phase, nanoflake morphology and curved carbon substrate shows ultrahigh mass activity for formic acid oxidation as high as 3624 mA/mgPd.
Abstract
Nowadays, PdCu alloy nanocatalyst with excellent performance in electrocatalytic formic acid oxidation reaction (FAOR) is believed to have great potential in application of direct formic acid fuel cells. Structural engineering has shown great success in achieving PdCu alloys with high catalytic performance, while achievement of multi-scale structure engineering is still a great challenge. In this work, we found that supercritical carbon dioxide (SC CO2) could lead to multi-scale structure engineering in PdCu/C nanocatalysts, including surface defect engineering, phase engineering, morphology engineering and substrate structure engineering. With the assistance of SC CO2, amorphous phase in surface, the transformation from face-centered cubic (FCC) to body-centered cubic (BCC) phase, the morphology of 2D nanoflakes and the curved carbon as substrate all contribute to the ultrahigh mass activity for electrocatalytic FAOR as 3624.3 mA/mgPd in PdCu/C nanocatalysts, which is the highest value in PdCu alloy reported up to now. Therefore, this work not only displays the great potential of SC CO2 in multi-scale structure engineering, but also provides new inspiration of material design to achieve nanocatalysts with ultrahigh catalytic performance.
Ionization, intrinsic basicity, and intrinsic acidity of unsaturated diols of astrochemical interest: 1,1‐ and 1,2‐ethenediol: A theoretical survey
The structure, stability, and bonding characteristics of 1,1- and 1,2-ethenediol, their radical cations, and their protonated and deprotonated species were investigated using high-level ab initio G4 calculations.
Abstract
The structure, stability, and bonding characteristics of 1,1- and 1,2-ethenediol, their radical cations, and their protonated and deprotonated species were investigated using high-level ab initio G4 calculations. The electron density of all the neutral and charged systems investigated was analyzed using the QTAIM, ELF, and NBO approaches. The vertical ionization potential (IP) of the five stable tautomers of 1,2-ethenediol and the two stable tautomers of 1,1-ethenediol go from 11.81 to 12.27 eV, whereas the adiabatic ones go from 11.00 to 11.72 eV. The adiabatic ionization leads to a significant charge delocalization along the O-C-C-O skeleton. The most stable protonated form of (Z)-1,2-ethenediol can be reached by the protonation of both the anti-anti and the syn-anti conformers, whereas the most stable deprotonated form arises only from the syn-anti one. Both charged species are extra-stabilized by the formation of an O-H···O intramolecular hydrogen bond (IHB) which is not found in the neutral system. (Z)-1,2-ethenediol is predicted to be less stable, less basic, and more acidic than its cis-glycolaldehyde isomer. The most stable protonated species of (E)-1,2-ethenediol comes from its syn-syn conformer, although the anti-anti conformer is the most basic one. Contrarily, the three conformers yield a common deprotonated species, so their acidity follows exactly their relative stability. Again, the (E)-1,2-ethenediol is predicted to be less stable, less basic, and more acidic than its trans-glycolaldehyde isomer. Neither the neutral nor the protonated or the deprotonated forms of 1,1-ethenediol show the formation of any O-H···O IHB. The most stable protonated species is formed by the protonation of any of the two tautomers, but the most stable deprotonated form arises exclusively from the syn-anti neutral conformer. The conformers of 1,1-ethenediol are much less stable and significantly less basic than their isomer, acetic acid, and only slightly more acidic.
C,N‐Diarylformamidines as Valuable Building Blocks in the Synthesis of Heterocyclic Compounds
This review is devoted to the heterocyclization of C,N-diarylformamidines and covers publications from 1999 to 2022. The comprehensive information collected enables other researchers to quickly understand the possibility of constructing various complex heterocycles from simple, readily available reagents.
Abstract
Obtaining highly functionalized heterocyclic structures is an important topic of modern organic synthesis, as it reveals the possibility of constructing more complex systems and therefore, expanding the range of various drugs. Aiming at synthesizing complex molecules from simple and readily available reagents, the modification of C,N-diarylformamidines, well known in medicinal chemistry, is of great interest. This article reviews comprehensively the field of C,N-diarylformamidine chemistry and covers publications on this topic from 1999 to 2022.
PPh3‐Mediated Nucleophilic Sulfonation of Sulfonyl Chlorides with Arynes: Access to Manifold Aryl Sulfones
A novel PPh3-mediated nucleophilic sulfonation of sulfonyl chlorides with arynes has been demonstrated. This protocol exhibits broad functional group tolerance and provides a direct approach to a variety of aryl and alkyl sulfones.
Abstract
Sulfonyl chlorides are a class of cheap and readily available basic chemicals, which have routinely served as electrophilic reagents in their chemical transformations. Herein, we disclose a novel PPh3-mediated nucleophilic sulfonation method of sulfonyl chlorides with arynes. Different from the classical P(III)-mediated reductive deoxygenation reaction of sulfonyl chlorides, the valence state of the sulfur atom has not been changed. This protocol exhibits broad functional group tolerance and provides a direct approach to a variety of aryl and alkyl sulfones.
Host‐Guest Complexes of Pillar[5]arene as Components for Supramolecular Light‐Harvesting Systems with Tunable Fluorescence
![Host-Guest Complexes of Pillar[5]arene as Components for Supramolecular Light-Harvesting Systems with Tunable Fluorescence](https://onlinelibrary.wiley.com/cms/asset/3161adbc-ec10-4376-adcb-240a9b139634/cplu202300431-toc-0001-m.png)
A supramolecular light-harvesting system with high donor/acceptor ratio has been constructed from pillar[5]arene-based host-guest complex in water. The system exhibits tunable fluorescence emission and can be used as fluorescent ink for information encryption.
Abstract
A guest molecule containing a short alkyl spacer between the tetraphenylethylene group and the methylpyridinium group was designed and synthesized. After complexation with a water-soluble pillar[5]arene, the resulting host-guest complex can further self-assemble into fluorescence-emitting nanoparticles in water. By loading a commercially available dye Rhodamine 6G into the nanoparticles, an efficient artificial light-harvesting system with high donor/acceptor ratios (>400/1) was successfully constructed. The obtained systems show considerable antenna effects with values of more than 10 times. The system also exhibits tunable fluorescence emission behavior and can be used as a fluorescent ink for information encryption.
A „Magic Mushroom“ Multi‐Product Sesquiterpene Synthase
Shrooms going terpenoid: The sesquiterpene synthase CubA of the “magic mushroom” Psilocybe cubensis was identified as a multi-functional enzyme producing cubebol, β-copaene, and various other mono-, bi-, and tricyclic sesquiterpenes or -terpenoids. As related enzymes are encoded in numerous Psilocybe species, our results provide further insight into the true metabolic diversity of this genus.
Abstract
Psilocybe “magic mushrooms” are chemically well understood for their psychotropic tryptamines. However, the diversity of their other specialized metabolites, in particular terpenoids, has largely remained an open question. Yet, knowledge on the natural product background is critical to understand if other compounds modulate the psychotropic pharmacological effects. CubA, the single clade II sesquiterpene synthase of P. cubensis, was heterologously produced in Escherichia coli and characterized in vitro, complemented by in vivo product formation assays in Aspergillus niger as a heterologous host. Extensive GC-MS analyses proved a function as multi-product synthase and, depending on the reaction conditions, cubebol, β-copaene, δ-cadinene, and germacrene D were detected as the major products of CubA. In addition, mature P. cubensis carpophores were analysed chromatographically which led to the detection of β-copaene and δ-cadinene. Enzymes closely related to CubA are encoded in the genomes of various Psilocybe species. Therefore, our results provide insight into the metabolic capacity of the entire genus.
Benchmarking boron cluster calculations: Establishing reliable geometrical and energetic references for Bn (n = 1–4)
Abstract
Using full configuration interaction (FCI) and multi-reference configuration interaction methods (MRCI), reliable geometrical and energetic references for B n (n = 1–4) clusters were established. The accuracy of the computed results was confirmed by comparison with available experimental data. Benchmark calculations indicated that B97D3, B97D, VSXC, HCTH407, BP86 and CCSD(T) methods provided reasonable results for structural parameters, with mean absolute error (MAEs) within 0.020 Å. Among the tested density functional theory (DFT) methods, the VSXC functional showed the best performance in predicting the relative energies of B1B4 with a MAE of 12.8 kJ mol−1. Besides, B1B95, B971, TPSS, B3LYP, and BLYP functionals exhibited reasonable performance with MAE values of less than 15.0 kJ mol−1. T 1 diagnostic values between 0.035 and 0.109 at the CCSD(T) level revealed strong correlations in B2B4 clusters, highlighting the need for caution in using CCSD(T) as an energy reference for small boron clusters. The methods of CCSDT, CCSDT(Q) and CCSDT[Q], which incorporate three-electron and four-electron excitations, effectively improved the accuracy of the energy calculations.
Gemini surfactant‐stabilized Pd nanoparticles: Synthesis, characterization, and catalytic application in the reduction and reductive acetylation in the water solvent
The organogels have been prepared using long-chain gemini surfactants. Their rheological properties such as amplitude sweeping and viscosity shear profile have been studied. Further reductive acetylation was carried out in an aqueous medium using Pd NPs stabilized by organogels.
A series of Gemini surfactants (GSs) were prepared by reacting alkyl bromides with N,N,N′,N′-tetramethyl ethylenediamine. Various alkyl bromides used in for the preparation of GSs are 1,3-dibromo ethane, 1,3-dibromoethane, 1-Bromohexane, 1-Bromooctane, 1-Bromooctadecane and 1-Bromooctadodecane. Different solvents and temperatures were investigated for the formation of gels of prepared GSs. Among all, 1-Bromooctane, 1-Bromooctadecane-derived GSs formed organogels. Thus, synthesized long-chain organogels have been used to stabilize Pd NPs. The Pd NPs formation initially confirmed through Ultraviolet-visible, Scanning Electron Microscopy, and Atomic Force Micrograph studies. Later Fourier Tansform Infra Red, Thermo Gravimetric Analysis, and Zeta potential studies were also carried out to understand their properties extensively. The Pd NPs stabilized by GSs have been identified as a potential catalyst in the reductive N-acetylation of nitroaromatics at room temperature. The N-acetylated products were obtained in good yields in an aqueous medium. In addition, the potentiality of our catalyst has been also evaluated in the reduction of nitroaromatics in an aqueous medium, which is a green protocol. Further, the semi-empirical geometry optimizations of active GS gel confirmed the dihedral angle of 59° in between the two octyl moieties calculated from computational studies. The rheological properties such as amplitude sweeping, viscosity shear profile of the gel have also been studied.
Electrocatalytic Reduction of (Hetero)Aryl Halides in a Proton‐Exchange Membrane Reactor and its Application for Deuteration
We developed an electrocatalytic reduction of (hetero)aryl halides to substitute the halogeno groups to protons using a proton exchange membrane (PEM) reactor. Taking advantage of this transformation, deuterodehalogenation of (hetero)aryl bromides, which forms mono-deuterated (hetero)aryls, was demonstrated using heavy water as a deuterium source. The deuteration reaction was able to be optimized by Bayesian.
Abstract
We developed an electrocatalytic reduction of (hetero)aryl halides under mild conditions using a proton exchange membrane (PEM) reactor. This approach allows substituting the halogeno groups on the aryl rings to protons by water and electron. Taking advantage of this transformation, deuterodehalogenation of (hetero)aryl halides, which forms mono-deuterated (hetero)aryls, was demonstrated using heavy water as a deuterium source. The current efficiency and deuterium ratio could be increased by the conditions optimized by machine-learning method, Bayesian optimization.