Ag Interactions Research Articles

A novel one-dimensional silver cylinder stabilized by mixed 2-mercaptobenzoic acid and ethylenediamine ligands

A novel infinite one-dimensional silver cylinder, namely poly[μ-ethylenediamine-μ(5)-(2-sulfanidylbenzoato)-μ(4)-(2-sulfanidylbenzoato)-tetrasilver(I)], [Ag(4)(C(7)H(4)O(2)S)(2)(C(2)H(8)N(2))](n), has been synthesized by one-pot reaction of equivalent molar silver nitrate and 2-mercaptobenzoic acid (H(2)mba) in the presence of ethylenediamine (eda). One Ag atom is located in an AgS(2)NO four-coordinated tetrahedral geometry, two other Ag atoms are in an AgS(2)O three-coordinated T-shaped geometry and the fourth Ag atom is in an AgSNO coordination environment. The two mba ligands show two different binding modes. The μ(2)-N:N'-eda ligand, acting as a bridge, combines with mba ligands to extend the Ag(I) ions into a one-dimensional silver cylinder incorporating abundant Ag···Ag interactions ranging from 2.9298 (11) to 3.2165 (13) Å. Interchain N-H···O hydrogen bonds extend the one-dimensional cylinder into an undulating two-dimensional sheet, which is further packed into a three-dimensional supramolecular framework by van der Waals interactions; no π-π interactions were observed in the crystal structure.

Pore Size Dependent Behavior of Hydrated Ag+ Ions Confined in Mesoporous MCM-41 Materials under Synchrotron X-ray Irradiation

The behavior of hydrated Ag+ ions in a 1.5 mol dm(-3) AgNO3 aqueous solution confined in mesoporous silica MCM-41 with different pore sizes was characterized by synchrotron X-ray absorption spectroscopy. The hydrated Ag+ ions are stabilized in 4-fold coordination down to 195 K in the pores (21 Å in diameter), whereas in the larger pores (28 Å) the hydrated Ag+ ions are reduced to Ag0 to form nano clusters with the Ag-Ag interactions of 2.80 Å.

Silver release from decomposed hyperaccumulating Amanita solitaria fruit-body biomass strongly affects soil microbial community

Interaction of Ag with communities of soil saprotrophic organisms was studied in two different soils using a metagenomic approach. Three levels of Ag were applied to the soil samples: 0, 0.008 and 0.505μg Ag/g soil. Silver was applied in mineral form as well as naturally bound in dry fruit-body biomass of the Ag-hyperaccumulating ectomycorrhizal fungus Amanita solitaria. Contrasting behavior of fungi and bacteria in reaction to Ag dosages was observed. The majority of bacterial ribotypes tended to prefer the soil with low doses of Ag, the ribotypes of fungi were more abundant in untreated soils and soils treated with the highest Ag concentration. Organically bound and mineral forms of Ag did not differ substantially in their effects on microbes in samples. The results indicate that decomposing Ag-rich fungal biomass can significantly alter the soil microbiota. This can contribute to formation of spot-like non-homogeneities in soil microbial distribution.

Comparative investigation of the interaction of Zn(II), Cd(II), Ag(I) and Pb(II) with dibenzo-substituted macrocyclic ligands incorporating both symmetrically and unsymmetrically arranged N, O and S donors: synthetic, solution and X-ray studies

A comparison of the interaction of Zn(II), Cd(II), Ag(I) and Pb(II) with a matrix of 18, 17-membered, dibenzo-substituted macrocyclic ligands (1–18) incorporating nitrogen, oxygen and/or sulfur heteroatom sites that share the same carbon backbone is reported. Potentiometric log K data for complexes of these metals with 5, 6, 8 and 9 incorporating unsymmetric arrangements of their donor sets were obtained and the results compared with previously determined stability data for the remaining symmetrical and unsymmetrical ligand complexes forming the above matrix. Structure–function relationships underlying the relative magnitudes of the respective log K values are discussed, with emphasis given to the influence of both the donor atom set and the donor atom sequence on the nature of the resulting complexes. The X-ray structures of [CdL(NO3)] (NO3)·CH3CH2OH (L = 4, SN4 donor set), [CdL(NO3)2]·CH3OH (L = 7, ON4 donor set), [AgL]PF6 (L = 4, SN4 donor set) and [AgL]PF6 (L = 9, OSN3 donor set) are presented along with that of the metal-free diprotonated nitrate salt (LH2)(NO3)2 (L = 6, S2N3 donor set).

Selective deposition on block copolymer film by thermal evaporation of silver

Selective deposition of Ag onto nanostructured block copolymer film template of poly(ethylene oxide) and poly(methacrylate) with azobenzene mesogen (PEO-b-PMA(Az)) has been done by thermal evaporation technique. A hexagonally arranged pattern or ordered strip structure of the PEO nanocylinders dispersed in the PMA(Az) matrix appears on the pure copolymer film surface after thermal annealing at 140°C or 110°C, respectively. Atomic force microscopy confirms that the deposited Ag atoms prefer to wet PMA(Az) matrix domains on the film surface, and finally aggregate into discrete nanoparticles in both cases. An ordered porous metallic layer is created on the hexagonally patterned copolymer template surface due to the preferential interaction of Ag toward the PMA(Az) phase. Alternatively, ordered array of metallic chains is formed on the template featured with strip structure. While the nominal layer thickness of the deposited Ag is 50nm, the ordered metallic nanostructure disappears, indicating the host copolymer template cannot guide the spatial distribution of the deposited metal any more.

Syntheses, characterization and antimicrobial activity of silver(I) complexes containing 2-hydroxymethyl-N-alkylimidazole ligands

Silver(I) complexes [Ag2(L)4](NO3)2 were synthesized by the reaction of AgNO3 with 2-hydroxymethyl-N-alkylimidazoles (L) (alkyl=benzyl, methyl, ethyl, propyl, butyl, heptyl, octyl and decyl) in ethanol at room temperature. The X-ray crystal structures of [Ag2(2-hydroxymethyl-N-ethylimidazole)4](NO3)2 (C2) showed a dimeric [Ag(L)4](NO3)2 and a monomeric [Ag(L)2]NO3 complex (L=2-hydroxymethyl-N-ethylimidazole) in its unit cell, while [Ag2(2-hydroxymethyl-N-benzylimidazole)4](NO3)2 (C8) showed only a dimeric complex [Ag2(L)4](NO3)2 (L=2-hydroxymethyl-N-benzylimidazole). Both complexes displayed a slightly distorted linear N–Ag–N arrangement and the presence of Ag–Ag interactions in the dimeric complexes was due to the π stacking of the imidazole moieties. The antimicrobial properties of the Ag(I) complexes were investigated against Escherichia coli, Staphylococcus aureus, Bacillus spizizenii and Candida albicans by the disk diffusion and the broth microdilution methods. The Ag(I) complexes containing 2-hydromethyl-N-alkylimidazole ligands with shorter alkyl chain length were predominantly active against E. coli. The complexes containing ligands with longer alkyl chain length displayed predominant activity against B. spizizenii. The broad spectrum antimicrobial activity displayed by these silver(I) complexes makes them potential alternatives to the commercially available antimicrobial agents.

Well‐Defined Nanoclusters as Fluorescent Nanosensors: A Case Study on Au25(SG)18

The fluorescence of nanoparticles has attracted much attention in recent research, but in many cases the underlying mechanisms are difficult to evaluate due to the polydispersity of nanoparticles and their unknown structures, in particular the surface structures. Recent breakthroughs in the syntheses and structure determinations of well-defined gold nanoclusters provide opportunities to conduct in-depth investigations. Devising well-defined nanocluster sensors based on fluorescence change is of particular interest not only for scientific studies but also for practical applications. Herein, the potential of the glutathionate (SG)-capped Au(25) nanocluster as a silver ion sensor is evaluated. The Ag(+) detection limit of approximately 200 nM, based on the fluorescence enhancement and good linear fluorescence response in the silver ion concentration range from 20 nM to 11 μM, in combination with the good selectivity among 20 types of metal cations, makes Au(25) (SG)(18) a good candidate for fluorescent sensors for silver ions. Further experiments reveal three important factors responsible for the unique fluorescence enhancement caused by silver ions: 1) the oxidation state change of Au(25) (SG)(18) ; 2) the interaction of neutral silver species (Ag(0) , reduced by Au(25) (SG)(18) (-) ) with Au(25) (SG)(18) ; and 3) the interaction of Ag(+) with Au(25) (SG)(18.) Experiments demonstrate the very different chemistry of hydrophobic Au(25) (SC(2) H(4) Ph)(18) and hydrophilic Au(25) (SG)(18) in the reaction with silver ions. This work indicates another potential application of gold nanoclusters, offers new strategies for nanocluster-based chemical sensing, and reveals a new way to influence nanocluster chemistry for potential applications.

Synthesis, Structure, and Photoluminescent Property of a Novel 2D Silver(I) Polymer Based on Short Ag-Ag Interactions

A new two-dimensional (2D) polymer, [Ag(2-Clnic)]n (2-Clnic = 2-chloronicotinate) (1), has been synthesized and characterized by IR, elemental analysis, single-crystal X-ray diffraction, and luminescence spectroscopy. X-ray crystal analysis reveals that complex 1 is constructed through π-π stacking and Ag…O interactions, which provide important roles in the assembly of intriguing structures and specific photophysical properties. In the solid state at room temperature, 1 is found to be luminescent with a purple emission band at 411 nm upon excitation at 360 nm.

Six low-dimensional silver(I) coordination complexes derived from 2-aminobenzonitrile and carboxylates

Six new Ag(I) coordination complexes, [Ag(abn)(4-cba)]2 (1), [Ag(abn)(3-cba)]2 (2), [Ag(abn)(fba)]2 (3), [Ag(abn)(3-mba)]2 (4), [Ag(abn)(moba)]2 (5), [Ag(abn)2(4-mba)]n (6), (abn=2-aminobenzonitrile, 4-cbaH=4-chlorobenzoic acid, 3-cbaH=3-chlorobenzoic acid, Hfba=3-fluorobenzoic acid, 3-mbaH=3-methylbenzoic acid, Hmoba=2-methoxybenzoic acid and 4-mbaH=4-methylbenzoic acid), have been synthesized and characterized by elemental analysis, IR spectra and single crystal X-ray diffraction. Complexes 1–4 are similar discrete binuclear Ag(I) motif containing monodentate μ1-Namino abn and μ2-η1:η1 carboxylates. The complementary Namino–H⋯Ncyano hydrogen bonds link the binuclear motifs into 1D chain which is further extended into 2D supramolecular sheet by Namino–H⋯Ocarboxyl hydrogen bonds. Notably, the electronic effect of substituents in 1–4 has deeply influence on the Ag⋯Ag interaction. Complex 5 is also a discrete binuclear Ag(I) motif but contains a monodentate μ1-Ncyano abn ligand. The 1D chain was observed in complex 6 where two different abn ligands with μ1-Ncyano and μ2-Ncyano, Namino coordination modes coexist and 4-mba is a chelating μ1-η1:η1 ligand. The results show that the different structures are predominantly attributed to the various ancillary carboxylate ligands and diverse coordination modes of abn ligand. Moreover, the emissive behaviors of them are discussed.

Silver Melonates and Coordination Modes of the Multidentate [C6N7(NCN)3]3– Anion

AbstractThree different silver melonates, Ag3[C6N7(NCN)3]·H2O (2a), Ag3[C6N7(NCN)3]·0.5NH3 (2b) and Ag3[C6N7(NCN)3]·2C2H8N2 (2c), and a nickel melonate, Ni3[C6N7(NCN)3]2·10NH3·6H2O (3), have been synthesised by the reaction of potassium melonate with silver nitrate either in an aqueous solution (2a), aqueous ammonia solution (2b) or an aqueous solution of ethylenediamine (2c) and with nickel nitrate in an aqueous ammonia solution (3). The crystal structure of 2c was determined by XRD [triclinic, P$\bar {1}$, a = 7.5499(4), b = 11.3438(6), c = 12.5741(7) Å, α = 72.138(4), β = 80.148(4), γ = 75.945(4)°, V = 984.90(9) Å3]. Silver atoms are coordinated to the terminal nitrogen atom of the cyanamide substituent as well as directly to the N atoms of the s‐heptazine core. Complex 2c crystallises in a layered structure. Adjacent Ag–melonate cation–anion units are connected by Ag–Ag interactions. The preferred coordination mode of metal ions at the melonate anion has been considered by quantum chemical calculations. Natural atomic charges calculated for the four nonequivalent, nucleophilic N atoms of the [C6N7(NCN)3]3– anion are (a) –0.596, (b) –0.619, (c) –0.675 and (d) –0.644. The metal coordination found experimentally in the melonates correlates with these relatively small charge differences and with the hard‐soft acid–base concept. However, (mono)protonation of the [C6N7(NCN)3]3– anion exclusively occurs at the terminal N atoms (b) of the s‐heptazine core, which is indicated experimentally and theoretically. Silver melonates 2a, 2b and 2c and nickel melonate 3 were further characterised by FTIR and 13C solid‐state magic‐angle spinning NMR spectroscopy, thermogravimetric/differential thermal analysis and elemental analysis. Solvent‐free complexes 2a and 2b, i.e. Ag3[C6N7(NCN)3], are thermally stable up to 500 °C. In contrast, 2c and 3 are thermally less stable.

A triple helix of double helicates: three hierarchical levels of self-assembly in a single structure

The bis-bidentate bridging ligand L reacts with Ag(I) ions to form a conventional dinuclear [Ag(2)L(2)](2+) double helicate; individual double helicate units assemble via Ag···Ag interactions into infinite chains, three of which wrap around a central spine of anions to give a triple helical braid, which is therefore an infinite triple helix composed of molecular double helicate subunits.

Coordination chemistry of Ag(i) with bridging ligands based on pyrazolyl–pyridine termini: polymers, helicates and a bow-tie

A series of Ag(I) complexes has been prepared containing bridging ligands based on two pyrazolyl–pyridine ligands connected by a flexible spacer. Crystallographic investigations reveal a remarkable range of structural types from simple mononuclear complexes to dinuclear double helicates, a distorted ‘bow-tie’ metallamacrocycle, and one-dimensional chains including a triple helical chain based on double helical molecular units linked by Ag⋯Ag contacts. The different structures arise as a result of the different interactions dominating in each complex, including aromatic π-stacking, Ag⋯Ag interactions, exocyclic lone pair interactions and inter-ligand π-stacking.

Real time plasmonic spectroscopy of the interaction of Hg2+ with single noble metal nanoparticles

In this work, we use dark-field optical microscopy (DFM) and hyper spectral imaging (HSI) to study the interactions of single Ag and Au nanoparticles (NPs) with Hg2+ in real time, at room temperature (25 °C). NPs were immobilized on glass substrates using 3-aminopropyltrimethoxysilane (APTMS) as the anchoring agent. Red, green and blue colors were assigned to the particles in hyper spectral images on the basis of their relative scattering intensities at 640, 550 and 460 nm, where the particles showed maxima in their scattering spectra. While Ag NPs showed all the colors, Au NPs were mostly red and rarely green in DFM images. The scattering spectra of Ag NPs were more blue shifted (with an average shift of 46 nm in the case of red particles) in a given time compared to Au NPs, after passing over Hg2+ solution and these shifts increased with time. Depending on the extent of blue shift, the colors of the particles got modified. Red particles appeared more reactive than green and blue, as revealed from the larger extent of shifts and their time dependence. The greater reactivity of red particles is attributed to their anisotropic nature possessing reactive tips, edges and more surface area due to their large size. The effect of quality of water on the scattering spectrum was checked by passing over deionized (DI) and tap waters separately, which showed that the effect is minimal compared to the presence of Hg2+, when data at a given time, flow rate and temperature were compared. Solution phase interactions of NPs with Hg2+ were also performed for comparison. These were characterized by UV-vis absorption spectroscopy, transmission electron microscopy (TEM) and energy dispersive analysis of X-rays (EDAX). Solution phase experiments showed citrate-induced aggregation of Ag NPs and partial reduction of Hg2+ to Hg0 upon exposure to Hg2+. Immobilized particles cannot aggregate and they show only reduction.

Non-adiabatic effects during the dissociative adsorption of O2 at Ag(111)? A first-principles divide and conquer study

We study the gas-surface dynamics of O2 at Ag(111) with the particular objective to unravel whether electronic non-adiabatic effects are contributing to the experimentally established inertness of the surface with respect to oxygen uptake. We employ a first-principles divide and conquer approach based on an extensive density-functional theory mapping of the adiabatic potential energy surface (PES) along the six O2 molecular degrees of freedom. Neural networks are subsequently used to interpolate these grid data to a continuous representation. The low computational cost with which forces are available from this PES representation allows then for a sufficiently large number of molecular dynamics trajectories to quantitatively determine the very low initial dissociative sticking coefficient at this surface. Already these adiabatic calculations yield dissociation probabilities close to the scattered experimental data. Our analysis shows that this low reactivity is governed by large energy barriers in excess of 1.1 eV very close to the surface. Unfortunately, these adiabatic PES characteristics render the dissociative sticking a rather insensitive quantity with respect to a potential spin or charge non-adiabaticity in the O2–Ag(111) interaction. We correspondingly attribute the remaining deviations between the computed and measured dissociation probabilities primarily to unresolved experimental issues with respect to surface imperfections.

An unusual 3D metal–organic framework, {[Ag4(μ4-pzdc)2(μ-en)2]·H2O}n: C–H⋯Ag, N–H⋯Ag and (O–H)⋯Ag interactions and an unprecedented coordination mode for pyrazine-2,3-dicarboxylate

A novel three-dimensional (3D) metal–organic framework of silver(I)-pyrazine-2,3-dicarboxylate (pzdc) with ethylenediamine ligand (en), {[Ag4(μ4-pzdc)2(μ-en)2]·H2O}n (1), was synthesized and structurally characterized by spectral methods (FT-IR and photoluminescence), elemental analysis, thermal analysis (TG, DTG, DTA) and single crystal X-ray diffraction techniques. X-ray crystallographic study of 1 revealed that the pzdc ligand adopts a new coordination mode. Four Ag(I) atoms with different coordination geometries are linked together with carboxylate groups to form 1D tetranuclear building block. The adjacent 1D blocks are connected through the en ligand to form a 2D layer structure, which is further connected to a 3D framework by argentophilic interaction (Ag1⋯Ag2 = 3.096 and Ag3⋯Ag4 = 3.3070 Å). The complex exhibits C–H⋯Ag, N–H⋯Ag intermolecular multicenter heteroacceptor (IMH) hydrogen-bonding interactions between the Ag(I) ions and hydrogen atoms of the en ligand and (O–H)⋯Ag interaction of the pseudo-agostic (IPA) between the Ag(I) ion and hydrogen atoms of the water molecule. In order to assess the potential of 1 in gas storage applications, we performed atomically detailed simulations. Furthermore, 1 exhibits green and unusual yellow luminescence in the solid state at room temperature. Complex 1 has also good antimicrobial activity (36–63 μg mL−1) on studied microorganisms.

Tetrakis[diamminesilver(I)] bis(2-hydroxy-5-methylbenzene-1,3-disulfonate) monohydrate

In the crystal structure of the title salt, [Ag(NH3)2]4(C7H6O7S2)2·H2O, the four independent AgI complex cations all lie on special positions of m site symmetry, as do the two independent 2-hy­droxy-5-methyl­benzene-1,3-disulfonate anions. The AgI cations exist in an almost linear coordination geometry [N—Ag—N = 175.2 (2), 178.08 (16), 175.8 (2) and 178.20 (19)°]. The water mol­ecule is disordered about a mirror plane. Two independent complex cations are linked by an Ag⋯Ag inter­action of 3.3151 (1) Å, furnishing a linear [Ag(NH3)2]n polycationic chain running along b. The free complex cations, polycationic chain and 2-hy­droxy-5-methyl­benzene-1,3-disulfonate anions inter­act via N—H⋯O and O—H⋯O hydrogen bonds, forming a three-dimensional network.

Effects of Lattice Polarity on Interfacial Space Charges and Defect Disorder in Ionically Conducting AgI Heterostructures

Heterostructured (β/γ)-AgI exhibits a spontaneous lattice polarization not accounted for in standard space-charge models. This polarization field dominates the positional variation of energies of isolated defects, and Ag(+) vacancies and interstitials are stabilized at alternate [β/γ] interfaces. This suggests enhanced Frenkel pair separation, analogous to electronic charge separation in polar semiconductor heterostructures. Stoichiometric systems are, however, characterized by associated Frenkel pairs due to strong V(Ag)-Ag(i) interactions and show no enhancement of defect numbers. In nonstoichiometric systems, lattice polarization does direct the distribution of the excess defect species, and defect-defect interactions enhance local Frenkel pair concentrations at interfaces, suggesting that nonstoichiometry is critical to the extreme room-temperature ionic conductivities observed in heterostructured AgI nanoplates.

A novel photoluminescent silver(I) wire supported by 4-tert-butylbenzoate and ligand-unsupported Ag⋯Ag interactions

Abstract A novel silver(I) wire sustained by 4-tert-butylbenzoate and ligand-unsupported Ag⋯Ag interactions, [Ag3(tbb)3(NH3)2]n (1, Htbb = 4-tert-butylbenzoic acid), has been synthesized and structurally characterized. In 1, three tbb ligands bind three Ag(I) ions to form a trinuclear subunit through ligand-supported Ag⋯Ag interactions. The inversion-related subunits are further extended to an infinite 1D zigzag Ag(I) wire through the ligand-unsupported Ag⋯Ag interactions. Argentophilicity (3.0283(14)–3.0910(17) A) plays an important role in determining the infinite silver(I) wire. The thermal stability and luminescent behavior of 1 were also discussed.

Structural optimization of Ag–Pd clusters based on different potential parameterizations

The putative stable structures of bimetallic Ag–Pd clusters are investigated. Gupta potential is applied to describe the interatomic interactions in Ag–Pd clusters. Experimental-fitted parameters and density-functional-theory (DFT)-fitted parameters are used to determine the lowest energy structures. Global optimization of Ag m Pd n ( m + n = 15) and Ag 3 m Pd 38−3 m ( m = 1–12) clusters is performed using adaptive immune optimization algorithm (AIOA). The growth rules of Ag–Pd clusters for both sets of parameterizations are studied, and the differences of structures and excess energies are compared. With the order parameters adopted to show the atomic distribution in the clusters, it is shown that for both parameterized clusters silver atoms have strong tendencies towards segregating at the surface of the structures. However, for both potentials, the atomic distribution of Ag and Pd atoms in Ag–Pd clusters is different because of the geometrical and symmetrical difference.

A discrete water hexamer with a new planar tetrameric water moiety trapped in the crystal host of [Ag(azelate)(4,4′-bipyridine)]·(H2O)3

Abstract The ultrasonic reaction of Ag2O, bipy and H2aze gave rise to a novel Ag(I) mixed-ligand coordination polymer, namely [Ag(aze)(bipy)]·(H2O)3 (1) (bipy = 4,4′-bipyridine, H2aze = azelaic acid). In 1, Ag(I) ions are linked by bipy and aze ligands to form a single two-dimensional (2D) undulated net with a (6,3) topology, incorporating Ag6(bipy)4(aze)2 windows of 22.58 × 11.06 A based on Ag⋯Ag distances. A pair of identical 2D single nets are interconnected via π⋯π stacking and unsupported Ag⋯Ag interactions to generate a 2D double-layered net. A discrete water hexamer composed of a new planar tetrameric water ring and two pendent water molecules is perpendicularly located in each hydrophilic cavity of the 2D bilayer and acts as a ‘glue’ to assemble adjacent 2D double-layered nets into a three-dimensional (3D) structure.