Monthly Archives: September 2023

Post‐Synthetic Modification of Zr‐based Metal‐Organic Frameworks with Imidazole: Variable Optical Behavior and Sensing

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Post-Synthetic Modification of Zr-based Metal-Organic Frameworks with Imidazole: Variable Optical Behavior and Sensing

Post-synthetic modification (PSM) with imidazole makes UiO-66-NH2 metal-organic framework (MOF) luminescent. This enables it to detect health-hazardous pollutants such as acetone, aq. Fe3+, and aq. CO3 2− by luminescence ON/OFF. This PSM MOF exhibits the highest sensitivity for pollutants among other no rare-earth element MOFs reported thus far in the literature.


Abstract

UiO-66-NH2-IM, a fluorescent metal-organic framework (MOF), was synthesized by post-synthetic modification of UiO-66-NH2 with 2-imidazole carboxaldehyde via a Schiff base reaction. It was examined using various characterization techniques (PXRD, FTIR, NMR, SEM, TGA, UV-Vis DRS, and photoluminescence spectroscopy). The emissive feature of UiO-66-NH2-IM was utilized to detect volatile organic compounds (VOCs), metal ions, and anions, such as acetone, Fe3+, and carbonate (CO3 2−). Acetone turns off the high luminescence of UiO-66-NH2-IM in DMSO, with the limit of detection (LOD) being 3.6 ppm. Similarly, Fe3+ in an aqueous medium is detected at LOD=0.67 μM (0.04 ppm) via quenching. On the contrary, CO3 2− in an aqueous medium significantly enhances the luminescence of UiO-66-NH2-IM, which is detected with extremely high sensitivity (LOD=1.16 μM, i. e., 0.07 ppm). Large Stern-Volmer constant, Ksv, and low LOD values indicate excellent sensitivity of the post-synthetic MOF. Experimental data supported by density functional theory (DFT) calculations discern photo-induced electron transfer (PET), resonance energy transfer (RET), inner filter effect (IFE), or proton abstraction as putative sensing mechanisms. NMR and computational studies propose a proton abstraction mechanism for luminescence enhancement with CO3 2−. Moreover, the optical behavior of the post-synthetic material toward analytes is recyclable.

A General Enantioselective C−H Arylation Using an Immobilized Recoverable Palladium Catalyst

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A General Enantioselective C−H Arylation Using an Immobilized Recoverable Palladium Catalyst

The enantioselective C−H arylation of aryl bromides herein developed afforded 30 enantioenriched products with high yields and enantioselectivities. By exploiting the “release and catch” mechanism of recoverable SP-NHC-PdII catalyst, in combination with BozPhos as a broadly applicable chiral ligand, good performances have been obtained across different substrates containing methyl, cyclopropyl and aryl C−H bonds.


Abstract

We herein report a general and efficient enantioselective C−H arylation of aryl bromides based on the use of BozPhos as the bisphosphine ligand and SP-NHC-PdII as recoverable heterogeneous catalyst. By exploiting the “release and catch” mechanism of action of the catalytic system, we used BozPhos as a broadly applicable chiral ligand, furnishing high enantioselectivities across all types of examined substrates containing methyl, cyclopropyl and aryl C−H bonds. For each reaction, the reaction scope was investigated, giving rise to 30 enantioenriched products, obtained with high yields and enantioselectivities, and minimal palladium leaching. The developed catalytic system provides a more sustainable solution compared to homogeneous systems for the synthesis of high added-value chiral products through recycling of the precious metal.

Outstanding Compatibility of Hard‐Carbon Anodes for Sodium‐Ion Batteries in Ionic Liquid Electrolytes

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Outstanding Compatibility of Hard-Carbon Anodes for Sodium-Ion Batteries in Ionic Liquid Electrolytes

The 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide ([EMI][FSI]) and, especially, N-trimethyl-N-butylammonium bis(fluorosulfonyl)imide ([N1114][FSI]) have shown very good compatibility towards hard carbon electrode with excellent cycling behavior, which represents one of the best results obtained for hard carbon electrodes in ionic liquid electrolytes, exceeding even that exhibited in organic electrolytes, making them rather appealing for the realization of safe, reliable and highly performing Na-ion cells.


Abstract

Hard carbons (HC) from natural biowaste have been investigated as anodes for sodium-ion batteries in electrolytes based on 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide ([EMI][FSI]) and N-trimethyl-N-butylammonium bis(fluorosulfonyl)imide ([N1114][FSI]) ionic liquids. The Na+ intercalation process has been analyzed by cyclic voltammetry tests, performed at different scan rates for hundreds of cycles, in combination with impedance spectroscopy measurements to decouple bulk and interfacial resistances of the cells. The Na+ diffusion coefficient in the HC host has been also evaluated via the Randles-Sevcik equation. Battery performance of HC anodes in the ionic liquid electrolytes has been evaluated in galvanostatic charge/discharge cycles at room temperature. The evolution of the SEI (solid electrochemical interface) layer grown on the HC surface has been carried out by Raman spectroscopy. Overall the sodiation process of the HC host is highly reversible and reproducible. In particular, a capacity retention exceeding 98 % of the initial value has been recorded in[N1114][FSI] electrolytes after more than 1500 cycles with a coulombic efficiency above 99 %, largely beyond standard carbonate-based electrolytes. Raman, transport properties and impedance confirms that ILs disclose the formation of SEI layers with superior ability to support the reversible Na+ intercalation with the possible minor contributions from the EMI+cation.

Controlled Potential Electrolysis: Transition from Fast to Slow Regimes in Homogeneous Molecular Catalysis. Application to the Electroreduction of CO2 Catalyzed by Iron Porphyrin

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Controlled Potential Electrolysis: Transition from Fast to Slow Regimes in Homogeneous Molecular Catalysis. Application to the Electroreduction of CO2 Catalyzed by Iron Porphyrin

The resting state of a homogeneous molecular catalyst during a controlled potential electrolysis depends on operational parameters (catalytic rate constant, cell dimensions and stirring rate). A formal description is given and illustrated through the electroreduction of CO2 catalyzed by Iron porphyrin switching from fast (confined catalysis) to slow (bulk catalysis) regimes.


Abstract

Molecular catalysis of electrochemical reactions is a field of intense activity because of the current interest in electrifying chemical transformations, including both electrosynthesis of organic molecules and production of fuels via small molecule activation. Controlled potential electrolysis (CPE) is often coupled with in situ in operando spectroscopic methods with the aim to gather mechanistic information regarding the catalytic species involved. Herein, considering a simple mechanism for a homogeneous molecular catalysis of an electrochemical reaction, we establish the concentration profile of the catalyst in the electrolysis cell enabling to envision the information that can be obtained from the coupling of this CPE with a spectroscopic probe in the cell compartment. We show how the characteristic parameters of the system (catalytic rate constant, cell dimensions and stirring rate) affect the response with particular emphasis on the transition between two limiting cases, namely a ‘fast’ catalysis regime where catalysis only takes place in a small layer adjacent to the electrode surface and a ‘slow’ catalysis regime where catalysis takes place in the bulk of the solution. These formal concepts are then illustrated with an experimental example, the electroreduction of CO2 in dimethylformamide homogeneously catalyzed by iron tetraphenylporphyrin and followed by UV-vis spectroscopy.

Water‐Abundant Electrolytes: Towards Safer and Greener Aqueous Zinc‐Metal Batteries

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Water-Abundant Electrolytes: Towards Safer and Greener Aqueous Zinc-Metal Batteries

This concept article aims to emphasize how to fabricate green and safe water-abundant Zn metal batteries. Several typical and advanced strategies towards water-abundant electrolyte systems are reviewed. We hope to arouse the attention of researchers for safer and greener aqueous Zn metal batteries when a large amount of toxic or expensive non-aqueous components are added into electrolytes.


Abstract

Aqueous Zn metal batteries have been regarded as promising candidates as an alternative to Li-ion batteries in large-scale energy storage systems due to their low-cost, safe and environmentally benign advantages. However, because of the introduction of solvent water, several problems, for example dendrites, parasite reactions, hydrogen evolution, and so on, are brought into aqueous Zn metal batteries. Regrettably, when trying to solve these problems, most efforts have taken the form of adding a large amount of non-aqueous components, which are usually harmful to the environment and not conducive to greener and safer aqueous batteries. In this Concept, we will introduce several electrolyte systems and mainly focus on how to build a water-abundant electrolyte with fewer non-aqueous components. This work will review the literature and offer instructive guidance for environmentally benign Zn metal batteries.

Diverse Reactivity of a Ca(I) Synthon

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Diverse Reactivity of a Ca(I) Synthon

Although complexes with Ca−Ca bonds are still elusive, a complex with a bridging C6H6 2− dianion reacts like a CaI synthon. However, depending on the reagent, different modes of reactivity have been observed.


Abstract

Low-valent MgI complexes like (BDI)Mg−Mg(BDI) have found wide-spread application as specialty reducing agents (BDI=β-diketiminate). Also their redox reactivity was extensively investigated. In contrast, attempts to isolate similar CaI complexes led to reduction of the aromatic solvents or N2. Complex (DIPePBDI)Ca(μ 6,μ 6-C6H6)Ca(DIPePBDI) (VIII) should be regarded a CaII complex with a bridging C6H6 2− dianion (DIPePBDI=HC[C(Me)N-DIPeP]2, DIPeP=2,6-C(H)Et2-phenyl). It can react as a CaI synthon by releasing benzene and two electrons. Herein we describe the reactivity of VIII with benzene, biphenyl, naphthalene, anthracene, COT, Ph3SiCl, PhSiH3, a (BDI)AlI2 complex, H2, PhX (X=F, Cl, Br, I), tBuOH and tBuCH2I. The C6H6 2− dianion in VIII can react as a 2e − source, a nucleophile or a Brønsted base. In some cases radical reactivity cannot be excluded. Crystal structures of (DIPePBDI)Ca(μ 8,μ 8-COT)Ca(DIPePBDI) (1) and [(DIPePBDI)CaX ⋅ (THF)]2 (X=F, Cl, Br, I) (2–5) are described.

Tuning the Lewis Acidity of Neutral Silanes Using Perfluorinated Aryl‐ and Alkoxy Substituents

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Tuning the Lewis Acidity of Neutral Silanes Using Perfluorinated Aryl- and Alkoxy Substituents

A set of Lewis acids was synthesized by installing perfluorotolyl- and perfluorocresolato ligands on neutral Si(IV) atoms. Additionally, a heteroleptic silane was synthesized using perfluoropinacolato and perfluorophenyl substituents. The obtained silanes were fully characterized and a Lewis acidity assessment was conducted by the Gutmann-Beckett and Childs method.


Abstract

The emerging field of Lewis acidic silanes demonstrates the versability of molecular silicon compounds for catalytic applications. Nevertheless, when compared to the multifunctional boron Lewis acid B(C6F5)3, silicon derivatives still lack in terms of reactivity. In this regard, we demonstrate the installation of perfluorotolyl groups (Tol F ) on neutral silicon atoms to obtain the respective tetra- and trisubstituted silanes Si(Tol F )4 and HSi(Tol F )3. These compounds were fully characterized including SC-XRD analysis but unexpectedly showed no significant Lewis acidity. By using strongly electron-withdrawing perfluorocresolato groups (OTol F ) the tetrasubstituted silane Si(OTol F )4 was obtained, bearing an 8 % increased Δδ(31P) shift when applying the Gutmann-Beckett method, compared to literature-known Si(OPh F )4. Ultimately the heteroleptic Si(Ph F )2pin F was successfully synthesized and fully characterized including SC-XRD analysis, introducing a highly Lewis acidic silicon atom holding two silicon-carbon bonds.

Hydrogen diffusion on (100), (111), (110) and (211) gold faces

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Hydrogen diffusion on (100), (111), (110) and (211) gold faces

The surface diffusion barriers of H increase in the following Au series: (110) < (111) < (100) < (211). The presence of low-coordinated Au atoms significantly reduces the surface adsorption barrier of H. A U-shaped dependence of the surface diffusion energy of H on the centres of the s- and d-bands of the gold atoms has been revealed.


Abstract

Calculations showed that hydrogen adsorption into subsurface sites is most likely to occur on Au (110) and (211) faces. The presence of low-coordinated Au atoms on significantly reduces the barrier of subsurface adsorption of H. The barriers of H surface diffusion increase in the following Au series: (110) < (111) < (100) < (211). An analysis of the dependence of the surface diffusion barriers on the electronic structure of gold atoms on the respective faces revealed a U-shaped dependence of the centers of the s- and d-bands. This dependence is the result of the filling of the s- and d-bands on different faces of the gold. The results obtained suggest that it is possible to use band centers to determine surface diffusion barriers.

Unusual formation of Ir(III) complexes with non‐symmetrical NacNac ligands: Synthesis, characterization, and evaluation of catalytic activity in transfer hydrogenation reduction reactions

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Unusual formation of Ir(III) complexes with non-symmetrical NacNac ligands: Synthesis, characterization, and evaluation of catalytic activity in transfer hydrogenation reduction reactions

This graphical abstract describes how a new type of trans-dichloro-Ir(III) complexes derived from non-symmetrical NacNac-type ligands were unexpectedly obtained as the main reaction product from the former ligands and the dimeric species [Ir(COD)Cl2]. Finally, an evaluation was made of the catalytic activity of all complexes in the transfer hydrogenation reaction of ketones and imines.


A new type of trans-dichloro-Ir(III) complexes derived from non-symmetrical NacNac-type ligands was unexpectedly obtained as the main reaction product from the former ligands and the dimeric species [Ir(COD)Cl2]. One equivalent of LH was reacted with an excess of [Ir(COD)Cl]2 in dichloromethane or toluene as solvent and at room temperature. The general formula of the product is [IrCl2(COD)L] and was isolated as a sole product instead of the expected Ir(I) compound [Ir(COD)L]; all the new Ir(III) were prepared in high yields as microcrystalline solids. They were all stable under laboratory atmosphere, lasting for weeks in solution and for months in solid state. The structure of each compound was examined by 1D and 2D nuclear magnetic resonance (NMR) and high-resolution mass spectrometry (HRMS). Complex 1k was selected for an X-ray diffraction study. Finally, an evaluation was made of the catalytic activity of all complexes in the transfer hydrogenation reaction of ketones and imines.

Hantzsch Ester Modified Asymmetric BODIPY Probe with Ultra‐high Sensitivity for Ultra‐fast Detection of Endogenous Hypochlorite in Living Cells

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Hantzsch Ester Modified Asymmetric BODIPY Probe with Ultra-high Sensitivity for Ultra-fast Detection of Endogenous Hypochlorite in Living Cells

Two Hantzsch ester derived fluorescent probes were constructed based on asymmetric BODIPY-matrix. These probes both exhibited significant fluorescence turn-on with ultra-high sensitivity (LoD < 1 nmol/L), response to hypochlorite (ClO–) in 5 s, and displayed excellent selectivity to ClO– and favourable quantum yield. Notably, MeDHP-BCl achieved the real-time visualization of endogenous ClO– in living cells for its lower cytotoxicity and more remarkable fluorescence increment after activation.


Comprehensive Summary

Hypochlorite (ClO–) is an important reactive oxygen species produced by the immune system to fight off invading pathogens, but its over-expression can interfere with normal physiological process and induce serious diseases. Although a variety of molecular probes have been reported for detecting ClO–, the development of advanced fluorescent tools with faster response and higher sensitivity to precisely monitor ClO– remains a challenge. In this work, two Hantzsch ester (a derivative of 1,4-dihydropyridine) derived fluorescent probes MeDHP-BCl and MeDHP-PhBCl were constructed based on asymmetric BODIPY-matrix. These probes exhibit significant fluorescence turn-on in the ultra-sensitive (detection limit < 1 nmol/L) and ultra-fast response (≤ 5 s) to ClO–. The reaction has been determined to be a highly selective N-chlorination of Hantzsch ester which cannot be activated by various common bioactive species, including nitric oxide (NO) that could oxidize Hantzsch ester under aerobic physiological conditions in most reports. MeDHP-PhBCl possessed a relatively longer fluorescence emission wavelength and higher quantum yield after activation, while more notably, MeDHP-BCl displayed lower cytotoxicity and more remarkable fluorescence increment in the response to ClO–, enabling selective and precise visualization of endogenous ClO– over-expression in living RAW264.7 cells.