Silica-supported silver nanoparticles as an efficient catalyst for aromatic C-H alkylation and fluoroalkylation

Review and Theoretical Analysis of Fluorinated Radicals in Direct CAr-H Functionalization of (Hetero)arenes

We highlight key contributions in the field of direct radical CAr- H (hetero)aromatic functionalization involving fluorinated radicals. A compilation of Functional Group Transfer Reagents and their diverse activation mechanisms leading to the release of radicals are discussed. The substrate scope for each radical is analyzed and classified into three categories according to the electronic properties of the substrates. Density functional theory computational analysis provides insights into the chemical reactivity of several fluorinated radicals through their electrophilicity and nucleophilicity parameters. Theoretical analysis of their reduction potentials also highlights the remarkable correlation between electrophilicity and oxidizing ability. It is also established that highly fluorinated radicals (e.g. ⋅OCF3) are capable of engaging in single-electron transfer (SET) processes rather than radical addition, which is in good agreement with experimental literature data. A reactivity scale, based on activation barrier of addition of these radicals to benzene is also elaborated using the high accuracy DLPNO-(U)CCSD(T) method.

Non-Noble-Metal Mono and Bimetallic Composites for Efficient Electrocatalysis of Phosphine Oxide and Acetylene C-H/P-H Coupling under Mild Conditions

The present work describes an efficient reaction of electrochemical phosphorylation of phenylacetylene controlled by the composition of catalytic nanoparticles based on non-noble-metals. The sought-after products are produced via the simple synthetic protocol based on room temperature, atom-economical reactions, and silica nanoparticles (SNs) loaded by one or two d-metal ions as nanocatalysts. The redox and catalytic properties of SNs can be tuned with a range of parameters, such as compositions of the bimetallic systems, their preparation method, and morphology. Monometallic SNs give phosphorylated acetylene with retention of the triple bond, and bimetallic SNs give a bis-phosphorylation product. This is the first example of acetylene and phosphine oxide C-H/P-H coupling with a regenerable and recyclable catalyst.

Luminescent Sensors Based on the Assembly of Coinage Metal Nanoclusters

Coinage metals, such as Cu, Ag and Au, can form nanoclusters, which, when functionalized with ligands, have unique electronic and optical properties and are widely used in biomedical imaging, remote sensing, labeling, catalytic, etc. The mechanisms, structures and properties of nanocluster assemblies have been well reviewed. However, the collections and analyses of nanocluster assemblies for sensor application are few. This review examines different nanocluster sensor platforms with a focus on the assembly and analysis of the assembly processes and examples of applications.

Facile synthesis of silver nanocatalyst decorated Fe3O4@PDA core–shell nanoparticles with enhanced catalytic properties and selectivity

In this work, we have successfully prepared core–shell nanoparticles (Fe₃O₄@PDA) wrapped with Ag using a simple and green synthesis method. Without an external reducing agent, silver nanoparticles (Ag NPs) with good dispersibility were directly reduced and deposited on a polydopamine (PDA) layer. Fe₃O₄@PDA@Ag showed excellent catalytic activity and recyclability for 4-nitrophenol, and also exhibited good catalytic selectivity for organic dyes (MO and MB). This simple and green synthesis method will provide a platform for other catalytic applications.

In this work, we have successfully prepared core–shell nanoparticles (Fe₃O₄@PDA) wrapped with Ag using a simple and green synthesis method.

Acetonitrile and benzonitrile as versatile amino sources in copper-catalyzed mild electrochemical C-H amidation reactions

A mild, efficient electrochemical approach to the site-selective direct C–H amidation of benzene and its derivatives with acetonitrile and benzonitrile has been developed. It has been shown that joint electrochemical oxidation of various arenes in the presence of a copper salt as a catalyst and nitriles leads to the formation of N-phenylacetamide from benzene and N-benzylacetamides from benzyl derivatives (up to 78% yield). A favorable feature of the process is mild conditions (room temperature, ambient pressure, no strong oxidants) that meet the criteria of green chemistry.

Different pathways of C–H transformation depending on the substrate nature and oxidation potential.

Regioselective Direct C-H Trifluoromethylation of Pyridine

A highly efficient and regioselective direct C-H trifluoromethylation of pyridine based on an N-methylpyridine quaternary ammonium activation strategy has been developed. A variety of trifluoromethylpyridines can be obtained in good yield and excellent regioselectivity by treating the pyridinium iodide salts with trifluoroacetic acid in the presence of silver carbonate in N,N-dimethylformamide. The protocol features good functional group compatibility, easily available starting materials, and operational simplicity. Controlled experiments showed that the reaction may involve a nucleophilic trifluoromethylation mechanism.

Facile and Direct Preparation of Ultrastable Mesoporous Silica with Silver Nanoclusters: High Surface Area

We report the successful direct synthesis of an ultrastable mesoporous silicon dioxide framework containing silver nanoclusters using a modified true liquid crystal templating method. Our modification produced an extraordinary material with a high average Brunauer-Emmett-Teller specific surface area of 1785 m2 g-1 - the highest reported surface area to date - and an ultrastable mesoporous structure, which has been stable for nine years so far. This method eliminates the need for reduction of silver oxide into metallic silver and restricts the growth of silver clusters. The silver nanoclusters, with an average size of 1 nm, occupy the pores and walls of the framework. Analysis of the material using nitrogen adsorption/desorption method, high-resolution transmission electron microscopy, X-ray diffractometry, energy-dispersive X-ray diffractometry, X-ray photoelectron spectroscopy, and scanning electron microscopy is discussed herein.

Zn and Co redox active coordination polymers as efficient electrocatalysts

New redox active 1D helical coordination polymers M(fcdHp) (M(ii) = Zn(1), Co(2)) have been obtained.

Nano-architecture of silica nanoparticles as a tool to tune both electrochemical and catalytic behavior of NiII@SiO2

The present work introduces a facile synthetic route for efficient doping of [Ni^II(bpy)_x] into silica nanoparticles with various sizes and architectures. Variation of the latter results in different concentrations of the Ni^II complexes at the interface of the composite nanoparticles. The UV-Vis analysis of the nanoparticles reveals changes in the inner-sphere environment of the Ni^II complexes when embedded into the nanoparticles, while the inner-sphere of Ni^II is invariant for the nanoparticles with different architecture. Comparative analysis of the electrochemically generated redox transformations of the Ni^II complexes embedded in the nanoparticles of various architectures reveals the latter as the main factor controlling the accessibility of Ni^II complexes to the redox transitions which, in turn, controls the electrochemical behavior of the nanoparticles. The work also highlights an impact of the nanoparticulate architecture in catalytic activity of the Ni^II complexes within the different nanoparticles in oxidative C–H fluoroalkylation of caffeine. Both low leakage and high concentration of the Ni^II complexes at the interface of the composite nanoparticles enables fluoroalkylated caffeine to be obtained in high yields under recycling of the nanocatalyst five times at least.

The present work introduces a facile synthetic route for efficient doping of [Ni^II(bpy)_x] into silica nanoparticles with various sizes and architectures.

Ferrocene-Containing Sterically Hindered Phosphonium Salts

The synthesis and physical properties of the series of the ferrocenyl-containing sterically hindered phosphonium salts based on di(tert-butyl)ferrocenylphosphine is reported. Analysis of voltamogramms of the obtained compounds revealed some correlations between their structures and electrochemical properties. The elongation of the alkyl chain at the P atom as well as replacement of the Br⁻ anion by [BF₄]⁻ shifts the ferrocene/ferrocenium transition of the resulting salts into the positive region. DFT results shows that in the former case, the Br⁻ anion destabilizes the corresponding ion pair, making its oxidation easier due to increased highest occupied molecular orbital (HOMO) energy. Increased HOMO energy for ion pairs with the Br⁻ ion compared to BF₄⁻ are caused by contribution of bromide atomic orbitals to the HOMO. The observed correlations can be used for fine-tuning the properties of the salts making them attractive for applications in multicomponent batteries and capacitors.