Silver Carboxylate Research Articles

A general concept for highly efficient covalent laser patterning of graphene based on silver carboxylates

Three novel types of spatially resolved graphene architectures GA, GB, and GC respectively bearing CH3-, C6H5- and C3F7 groups are efficiently constructed by newly developed laser-writing concepts using silver carboxylates as corresponding photosensitizers. These 2D-structured samples are unequivocally characterized by Raman spectroscopy and SEM-EDS.

Continuous flow synthesis and antimicrobial evaluation of NHC* silver carboxylate derivatives of SBC3 in vitro and in vivo.

N-heterocyclic silver carbene compounds have been extensively studied and shown to be active agents against a host of pathogenic bacteria and fungi. By incorporating hypothesized virulence targeting substituents into NHC-silver systems via salt metathesis, an atom-efficient complexation process can be used to develop new complexes to target the passive and active systems of a microbial cell. The incorporation of fatty acids and an FtsZ inhibitor have been achieved, and creation of both the intermediate salt and subsequent silver complex has been streamlined into a continuous flow process. Biological evaluation was conducted with in vitro toxicology assays showing these novel complexes had excellent inhibition against Gram-negative strains E. coli, P. aeruginosa, and K. pneumoniae; further studies also confirmed the ability to inhibit biofilm formation in methicillin-resistant Staphylococcus aureus (MRSA) and C. Parapsilosis. In vivo testing using a murine thigh infection model showed promising inhibition of MRSA for the lead compound SBC3, which is derived from 1,3-dibenzyl-4,5-diphenylimidazol-2-ylidene (NHC*).

Liquid‐liquid‐phase Synthesis of exo‐Vinylene Carbonates from Primary Propargylic Alcohols: Catalyst Design and Recycling

AbstractA straight‐forward approach to separate catalyst from the exo‐vinylene carbonate (EVC) products of the carboxylative cyclisation of primary propargylic alcohols has been developed. The liquid‐liquid phase synthesis utilises lipophilic silver(I) carboxylate salts and N,N‐dioctyl modified phosphine (FatPhos) ligands to enhance catalyst solubility in non‐polar solvents. Following simple liquid‐liquid phase separation, EVCs relevant as monomers for poly(urethane) and poly(carbonate) synthesis were isolated in the non‐miscible polar phase in good yields. In situ reaction monitoring by ReactIR gave insights into the reaction kinetics and informed the conditions used to afford good EVC selectivity. Under optimised conditions, silver leaching into the product phase was very minor as confirmed by ICP‐MS. Furthermore, a protocol for catalyst recycling by liquid‐liquid separation was demonstrated, with modest loss of catalytic activity over 3 runs.

Ion-Functionalized Silver(I) Carboxylates: Synthesis and Application in Ru-Catalyzed Olefin Metathesis Reaction

The Grubbs–Hoveyda catalysts have a wide range of applications in catalyzed formation of the carbon-carbon double bonds. In this study, several imidazolium- functionalized or pyridinium-functionalized silver carboxylates have been prepared, and their reaction with Grubbs–Hoveyda 2nd generation (G–H 2nd) catalyst leads a new type of processes. Activity and selectivity of the catalysts have been preliminarily evaluated using cross olefin metathesis reactions.

Assessing the Efficacy of a Silver Carboxylate Antimicrobial Coating on Prosthetic Liners

ABSTRACT Introduction One of the leading issues facing persons with amputation is late development of antibiotic-resistant bacterial infections of the residual limb. To reduce this infection risk, this study assessed the antimicrobial properties and profile of a silver carboxylate complex coating applied to samples of common prosthetic liner materials against pathogens frequently encountered in amputation-site infections. Methods The antimicrobial efficacy of the coating was measured utilizing a Kirby-Bauer assay with two different types of commercially available prosthetic liners. The assay was run against four pathogens including coagulase-negative Staphylococcus epidermidis, methicillin-sensitive Staphylococcus aureus, Enterococcus faecalis, and multidrug-resistant Acinetobacter baumannii. Observations of bacterial inhibition were made at 24-, 48-, and 72-hr time points for all four pathogens. Dose response curves were created to assess the relative efficacy of the coating against each pathogen independent of prosthetic liners. Graphite furnace atomic absorption spectroscopy (GFAAS) was utilized to measure coating silver elution at 24-, 48-, and 72-hr time points. Results All conditions of the coating were variably antimicrobial against all tested pathogens in the Kirby-Bauer analysis. Dose response analysis further demonstrated the coating's antimicrobial profile against all tested pathogens. GFAAS demonstrated consistent silver release of the coating throughout 72 hrs. Conclusions The results of this study suggest the tested antimicrobial coating is effective against a broad range of drug-resistant pathogens. Due to its ability to reduce and inhibit bacterial growth along the prosthetic liner surface, the coating shows promise as an effective tool toward mitigating infection and malodor found at the residual limb-liner interface among persons with amputation.

Ligand Free Palladium‐Catalyzed Synthesis of α‐Trifluoromethylacrylic Acids and Related Acrylates by Three‐Component Reaction

AbstractAryl iodides and 2‐(trifluoromethyl)acrylic acid reacted together in ligand‐free Mizoroki‐Heck reaction furnishing a quick and efficient access to highly valuable α‐trifluoromethylacrylic acids. The useful transformation was independent with regard to the electronic nature of the aryl group substituent. A three‐component one‐pot version was also developed to give diverse substituted acrylates. The versatility of α‐trifluoromethylacrylic acids was demonstrated by quick access to 3‐CF3‐coumarins as well as fluorinated analogues of therapeutic or cosmetic agents. Finally, we proposed a catalytic cycle based on the silver carboxylate salt, identified as a key intermediate in the reaction.magnified image

Solid-State NMR, X-Ray Diffraction, and Theoretical Studies of Neutral Mononuclear Molecular Bis(triphenylphosphine)silver(I) Mono-Carboxylate and -Nitrate Systems

Neutral mononuclear molecular silver(i) carboxylate complexes of the form [(Ph3P)2Ag(O2XY)] with O2XY=O2CCH2Ph, O2CCHPh2, O2CC(CH3)3, O2CCH2C(CH3)3, and O2CCF3 (compounds 1–4 and 5β) have been investigated in the solid state using single-crystal X-ray structure determinations, 1D 31P CPMAS NMR and 2D 31P–31P CPCOSY NMR measurements, and ab initio computational modelling. The results show that these complexes contain P2AgO2 molecular cores with four-coordinate silver in which the carboxylate ligands are weakly bound to the silver atoms via the two oxygen atoms giving rise to unsymmetrical chelate units. Crystal structure determinations and solid-state NMR spectra have also been analysed for the mononuclear molecular silver(i) nitrate complex [(Ph3P)2Ag(O2NO)] (9α) and two polymorphs of its toluene monosolvate (11α, β). In 9α, the two PPh3 ligands are of the same chirality, whereas in 11α, β, they are opposed. The crystalline environments in the polymorphs have been explored by way of Hirshfeld surface analyses, after quantum-mechanical isolated-molecule calculations had shown that although the molecular energies of the experimental geometries of 9α, and 11α, β are significantly different from each other and from the energies of the optimized geometries, the latter, in contrast, do not differ significantly from each other despite the conformational isomerism. It has further been shown using 9α as an example that the energy dependence on variation of the P–Ag–P angle over a range of ~15° is only ~5 kJ mol−1. All this indicates that the forces arising from crystal packing result in significant perturbations in the experimental geometries, but do not alter the stereoisomerism caused by the donor atom array around the Ag atom. In the NMR study, a strong inverse correlation has been found between 1J(107/109Ag,31P) and the Ag–P bond length across all carboxylate and nitrate compounds.

Mechanism of the Palladium-Catalyzed C(sp3)–H Arylation of Aliphatic Amines: Unraveling the Crucial Role of Silver(I) Additives

DFT calculations have been combined with experiments to study the mechanism of γ-C(sp3)–H arylation of aliphatic amines promoted by palladium–glyoxylic acid cooperative catalysis, with a focus on the role of silver(I) additives. Glyoxylic acid (the cocatalyst) uses its aldehyde functionality to react with the amine substrate to form an iminoacetic acid. This acid acts as a transient directing reagent and metathesizes with Pd(OAc)2 (the precatalyst) to give a Pd(II)–diiminoacetate five-membered chelate, which has been shown computationally as the catalyst resting state and which has been experimentally synthesized and characterized. C(sp3)–H activation from the Pd(II)–diiminoacetate complex or its mononuclear derivatives would face a high kinetic barrier (>30 kcal/mol) arising mainly from breaking a stable five-membered N,O-chelate ring. The crucial role of the silver(I) carboxylate additive is in reacting with the Pd(II)–diiminoacetate complex to provide a heterodimeric Pd(II)–Ag(I) complex supported by bridging chelators and intermetallic Pd–Ag interaction, which would lead to a C(sp3)–H activation transition state with a considerably lower barrier (∼25 kcal/mol). The Pd(II)–Ag(I) complex has been detected by mass spectrometry, which provides the first experimental evidence of a Pd–Ag-containing active species in Pd-catalyzed C–H activation reactions using Ag(I) additives. After C(sp3)–H activation, the reaction proceeds through oxidative addition of Pd(II) and reductive elimination from Pd(IV) completing C–C formation, followed by ligand exchange to regenerate the catalyst resting state and release the arylated iminoacetic acid which continues on hydrolysis to give the final amine product and regenerate the glyoxylic acid cocatalyst. The computational and experimental findings taken together provide new mechanistic insight into the broad range of palladium-catalyzed C–H activation reactions that use silver(I) additives.

Regiocontrolled Heptafluoroisopropylation of Aromatic Halides by Copper(I) Carboxylates with Heptafluoroisopropyl-Zinc Reagents.

Copper(I)-mediated heptafluoroisopropylation of aryl halides (ArX: X = I, Br) is demonstrated using copper(I) carboxylates and a bis(heptafluoroisopropyl)zinc reagent Zn( i-C3F7)2(dmf)2, prepared from heptafluoroisopropyl iodide and diethylzinc. The air-tolerant solid heptafluoroisopropylzinc reagent is advantageous to conduct simple synthetic operations and successful to give the corresponding heptafluoroisopropyl arene derivatives via transmetalation to copper(I) center. The newly developed copper(I)-mediated heptafluoroisopropylation process can be advanced to the copper(I)-catalysis by silver carboxylate salts and complementary to the precedent radical-based processes.

Crystal Structures and Cytotoxicity of Four Silver(I)carboxylate Complexes with 1,2-Ethylenediamine Analogues

Four silver(I) compounds, [Ag(dapn)(dnbc)]n·1.5nH2O (1), [Ag(en)]n[Ag(dnbc)2]n·2nH2O (2), [Ag(en)]n[Ag(nbc)2]n·2nH2O (3) and [Ag(dapn)]n -(nbc)n·2nH2O (4), where dapn = 1,2-diaminopropane, dnbc = 3,5-dinitrobenzoate, en = 1,2-diaminoethane and nbc = 4-nitrobenzoate, have been synthesized and characterized by X-ray diffraction. The Ag(I) ions show T-shaped coordination geometry in compound 1 but linear coordination geometry in compounds 2, 3 and 4. There are ligand-unsupported Ag…Ag interaction in compounds 2 and 3 with Ag…Ag distance of 3.177 ~3.267 Å. All the four complexes showed high cytotoxicity properties.

Joining of copper at low temperatures using silver(I) carboxylates

The synthesis of three different Ag(I) carboxylates [(AgO2CCH2)3N] 1, [(AgO2C)2C5H8] 2, and [AgO2CC19H29] 3 and their suitability for joining of pure copper at low temperatures is reported. Upon heating silver(I) species 1–3, Ag nanoparticles are formed. Since nanoparticles exhibit a decreased melting and sintering temperature, low joining temperatures are possible. Major advantages of the Ag(I) carboxylates in comparison to conventional nanopastes are a low-cost synthesis, long-term stability, and simplified handling of the material. Besides description of the synthesis, the thermal behavior of 1–3 is discussed. Moreover, results of joining experiments, whereby the joints were characterized regarding to strength properties and microstructure, are discussed. The results show that with 1–3, partly equivalent strength properties, compared to a commercial Ag nanopaste, can be achieved. For pressureless joining, 1 and 2 represent a promising alternative to a conventional Ag nanopaste, since equivalent strengths can be reached. In particular, with 1, higher strengths can be achieved compared to the Ag nanopaste at a temperature of 250 °C and without pressure. However, at a higher temperature of 400 °C and a pressure of 40 MPa, strengths of the Ag nanopaste can be reached with 2 (with additives) and 3.

The synthesis, chemical and physical properties of silver(I) carboxylates and their use for joining of copper

The synthesis of [AgO2CCR2OC(O)OMe] (6, R = H; 7, R = Me) by treatment of HO2CCR2OC(O)OMe (4, R = H; 5, R = Me) with [AgNO3] in presence of NEt3 is reported. The reaction of 6 and 7 with 2 equiv of PPh3 gave [AgO2CCR2OC(O)OMe(PPh3)2] (8, R = H; 9, R = Me). The thermal behavior of 6 and 7 was studied by TG, DSC and TG-MS of which the latter evinced decarboxylation as initial decomposition step followed by AgC, CC and CO bond cleavages giving silver. For copper-to-copper joining, 6 and 7 were processed to spreadable pastes by mixing them with ethylene glycol (EG) or diethylene glycol (DEG). On contact of 7-EG with Cu sheets [Cu2(O2CCMe2OC(O)OMe)4·2H2O] (12) was formed. Therefore, only 6-EG and 6-DEG were used for pressureless joining of Cu at 250 °C. Thru addition of Ag µm-particles a tensile shear strength of 19 MPa was achieved, showing a significant higher value as received with commercially Ag nanopastes. The solid state structure of 5, 8, 9 and 12 was determined by single crystal X-ray structure analysis, showing [3+1] (P2O + O) (8), distorted tetrahedral (9) or octahedral (12) coordination spheres at the metal ion.

Thermal and laser sintering of a highly stable inkjet ink consisting of silver nanoparticles stabilized by a combination of a short chain carboxylic acid and a polymeric dispersant

A mixture of silver nanoparicles and its organic salt has been used for the development of conductive inks for inkjet printing. Silver nanoparticles stabilized with butanoic acid (C4) with the average size of 11.1±2.4 nm have been synthesized via the reduction of solid silver carboxylate with hydrazine hydrate in benzyl alcohol. An inkjet ink formulation consisting of the silver nanoparticles capped with butanoic acid (up to 50 wt.%) with the addition of polymeric BYK dispersant in a mixture of nontoxic solvents with different boiling temperatures and different polarities has been developed and its physical properties and stability have been studied. Silver layers were spin coated and printed on a polyimide film using the developed ink. Experiments on the thermal annealing of the silver films showed that the curing temperature can be below 200 °C to obtain a layer having the electrical resistivity less than 10 µΩ×cm. A study of the laser sintering of the printed and spin coated elements on a polyimide film using a diode laser operating at 453 nm in impulse mode showed that the best mode is a multi-pass sintering, which can be divided into two steps: the evaporation of the solvent and sintering of the silver nanoparticles.

Regularities of the formation of silver nanoparticles with oligostyrylmonocarboxylate ligands in ED-20 oligomer

Regularities of the formation of silver nanoparticles according to the reduction reaction of silver oligostyrylmonocarboxylate with ED-20 resin in the absence of hardening agent were studied at 60–75°C by UV/Vis spectroscopy and IR spectroscopy, transmission electron microscopy, and viscosimetry. Spherical silver nanoparticles with oligostyrylcarboxylate ligands characterized by diameter equal to 1.8 ± 0.2 nm and tendency toward ordered disposition in space were obtained. The process of formation of nanoparticles includes consecutive formation of diphilic complexes of silver carboxylate with epoxy resin, Ag+ → Ag0 reduction, and formation of (Ag0) n nuclei at the ends of the diexpoxy component and/or along the oligomer chain. The activation energy values of formation of nanoparticles during the “inductive period” and at the stage of accumulation as well as the activation energy of viscous flow of ED-20 were measured. The threshold temperature of formation of narrow-size silver nanoparticles in epoxy oligomer ED-20 equals 75°C.

Synthesis and characterization of silver nanoparticles from (bis)alkylamine silver carboxylate precursors

A comparative study of amine and silver carboxylate adducts [R1COOAg-2(R2NH2)] (R1 = 1, 7, 11; R2 = 8, 12) as a key intermediate in NPs synthesis is carried out via differential scanning calorimetry, solid-state FT-infrared spectroscopy, 13C CP MAS NMR, powder X-ray diffraction and X-ray photoelectron spectroscopy, and various solution NMR spectroscopies (1H and 13C NMR, pulsed field gradient spin-echo NMR, and ROESY). It is proposed that carboxyl moieties in the presence of amine ligands are bound to silver ions via chelating bidentate type of coordination as opposed to bridging bidentate coordination of pure silver carboxylates resulting from the formation of dimeric units. All complexes are packed as lamellar bilayer structures. Silver carboxylate/amine complexes show one first-order melting transition. The evidence presented in this study shows that phase behavior of monovalent metal carboxylates are controlled, mainly, by head group bonding. In solution, insoluble silver salt is stabilized by amine molecules which exist in dynamic equilibrium. Using (bis)amine-silver carboxylate complex as precursor, silver nanoparticles were fabricated. During high-temperature thermolysis, the (bis)amine-carboxylate adduct decomposes to produce silver nanoparticles of small size. NPs are stabilized by strongly interacting carboxylate and trace amounts of amine derived from the silver precursor interacting with carboxylic acid. A corresponding aliphatic amide obtained from silver precursor at high-temperature reaction conditions is not taking part in the stabilization. Combining NMR techniques with FTIR, it was possible to follow an original stabilization mechanism.Graphical abstractThe synthesis of a series (bis)alkylamine silver(I) carboxylate complexes in nonpolar solvents were carried out and fully characterized both in the solid and solution. Carboxyl moieties in the presence of amine ligands are bound to silver ions via chelating bidentate type of coordination. The complexes form layered structures which thermally decompose forming nanoparticles stabilized only by aliphatic carboxylates.

Stable Mono- and Dinuclear Organosilver Complexes

A series of mononuclear and dinuclear complexes of silver(I), supported by an N-heterocyclic carbene and bound to sp3-, sp2-, and sp-hybridized carbanions, has been synthesized. Synthetic routes include transmetalation from organozinc, organomagnesium, and organosilicon reagents, as well as the deprotonation of a terminal alkyne. These complexes exhibit greater thermal stability than typical organosilver reagents, permitting spectroscopic and structural characterization. The carbanion-bridged disilver cations feature three-center, two-electron bonding with short Ag···Ag distances. A mononuclear vinylsilver complex releases organic homocoupling products upon thermal decomposition, while mononuclear alkylsilver complexes exhibit nucleophilic behavior, for example, inserting CO2 to form silver carboxylates.

Correlating light and thermal stability of silver carboxylate complexes by infrared and 13C NMR spectroscopy

Bond nature of carboxylic groups can play an important role in Ag(I)-carboxylate compounds because light and thermal stability are important requirements for future applications such as antibacterial additives. A linear correlation between bond character and light stability of silver carboxylate complexes has been predicted by a direct relationship of infrared and 13C NMR spectroscopic data. This correlation is in agreement with the thermogravimetric analysis and provides a new approach to explore the interaction and the physical properties of metal-carboxylate bonds.

Role of Silver Salts in Palladium-Catalyzed Arene and Heteroarene C–H Functionalization Reactions

Silver carboxylate salts are widely used as additives in palladium-catalyzed C–H functionalization reactions. However, the role of these silver additives is often not fully understood. This paper describes an investigation of the role of AgOPiv in the stoichiometric activation of C6F5H at a well-defined PdII complex as well as in the PdII-catalyzed oxidative dimerization of 2-alkylthiophenes. Both in situ NMR spectroscopy and H/D exchange studies of the reactions of C6F5H implicate a role for AgOPiv in the C–H cleavage event, generating Ag–C6F5 as an intermediate. The catalytic studies show similar trends despite the different conditions and substrates, suggesting that AgOPiv promotes a similar metalation of the thiophene in the catalytic transformations. This proposal is supported by DFT calculations, which show energetically feasible pathways for concerted metalation–deprotonation of both 2-methylthiophene and pentafluorobenzene at [Ag(OPiv)]2. These studies suggest that initial metalation of C–H substr...

Preparation of electroconductive aluminum-silicon oxide ceramic sensors modified with silver and bismuth nanoparticles

AbstractCurrently, to provide complete information on measuring is one of the most essential problems for measuring devices. In order to obtain electrodes for recording of cardiac micropotentials in a wide range of frequencies, a process for modifying of the aluminum-silicon oxide ceramic matrix with bismuth or silver nanoparticles was investigated. It was found that when impregnating aluminum-silicon oxide ceramics with aqueous or organic solutions of the silver compounds with subsequent drying and calcinations, both the total amount of silver and its distribution over the thickness of the sample essentially depend on the nature of the silver precursor solution. Thus, when impregnating the aluminum-silicon oxide ceramics with an aqueous solution of silver nitrate followed by its reduction with formic acid, the silver content in the ceramic matrix does not exceed 15% and it is mainly distributed in the near-surface layer. The highest degree of impregnation (39%) and uniform distribution of silver throughout the volume of the sample are achieved by treatment of the ceramic matrix with a branched silver carboxylate (silver caprate) solution containing 250 g/L Ag, followed by drying and calcination of the samples at 250°C. It was shown that bismuth-containing electroconductive ceramics can be obtained by its impregnation with a solution of bismuth formate or caprylate followed by its calcination in vacuum at 280°C. The results of the study showed that the ceramic sensors modified with silver nanoparticles have a direct current drift of less than 5 nV/s while the noise level does not exceed±200 nV, which allows development of the measuring apparatus from 300 nV.

Infrared and Visible Photodissociation Spectra of Rhodamine Ions at 3 K in the Gas Phase.

Helium-tagging predissociation spectroscopy in the visible spectral range (He@VisPD) is shown for Rhodamine 123, Rhodamine 110, and Rhodamine 110's silver salt (silver carboxylate). It is shown that the spectra reflect single-photon absorption. The helium-tagged ions are in the ground vibrational state, and the He@VisPD spectra feature the Franck-Condon envelopes for the excitation to the first excited singlet state that agree very well with theoretical simulations. The S0 → S1 excitation energies are 2.712 ± 0.006 eV for Rhodamine 123, 2.700 ± 0.006 eV for Rhodamine 110, and 2.751 ± 0.006 eV for the silver salt of Rhodamine 110. The determined energies can be slightly blue-shifted due to the binding energy of helium. The Rhodamine ions were also characterized by helium-tagging infrared photodissociation spectroscopy. The distinctive spectral features of the individual derivatives are described and the spectra are compared to the classical solid-state IR spectra.