Coordination Of Ag Research Articles

Facile Energy Release from Substituted Dewar Isomers of 1,2-Dihydro-1,2-Azaborinines Catalyzed by Coinage Metal Lewis Acids.

Molecular solar thermal systems (MOST) represent an auspicious solution for the storage of solar energy. We report silver salts as a unique class of catalysts, capable of releasing the stored energy from the promising 1,2-dihydro-1,2-azaborinine based MOST system. Mechanistic investigations provided insights into the silver catalyzed thermal backreaction, concurrently unveiling the first crystal structure of a 2-aza-3-borabicyclo[2.2.0]hex-5-ene, the Dewar isomer of 1,2-dihydro-1,2-azaborinine. Quantification of activation energies by kinetic experiments has elucidated the advantageous energy change associated with Lewis acid catalysts, a phenomenon corroborated through computational analysis. By means of low temperature NMR spectroscopy, mechanistic insights into the coordination of Ag+ to the 1,2-dihydro-1,2-azaborinine were gained.

Facile Energy Release from Substituted Dewar Isomers of 1,2‐Dihydro‐1,2‐Azaborinines Catalyzed by Coinage Metal Lewis Acids

AbstractMolecular solar thermal systems (MOST) represent an auspicious solution for the storage of solar energy. We report silver salts as a unique class of catalysts, capable of releasing the stored energy from the promising 1,2‐dihydro‐1,2‐azaborinine based MOST system. Mechanistic investigations provided insights into the silver catalyzed thermal backreaction, concurrently unveiling the first crystal structure of a 2‐aza‐3‐borabicyclo[2.2.0]hex‐5‐ene, the Dewar isomer of 1,2‐dihydro‐1,2‐azaborinine. Quantification of activation energies by kinetic experiments has elucidated the advantageous energy change associated with Lewis acid catalysts, a phenomenon corroborated through computational analysis. By means of low temperature NMR spectroscopy, mechanistic insights into the coordination of Ag+ to the 1,2‐dihydro‐1,2‐azaborinine were gained.

Exclusive Coordination between Melem and Silver(I) Ions: From Irregular Aggregates to Nanofibers to Crystal Cubes.

There is growing focus on metal-free molecules and polymers owing to their potential applications in various energy and catalysis-related applications. Melem (2,5,8-triamino-s-heptazine, C6H6N10) has emerged as a metal-free material for solar-to-fuel conversion. However, its reactivity with metal ions or organic molecules has never been reported although it possesses multiple supramolecular interaction sites. In this work, we report on the synthesis of a novel metal-organic coordination framework (melem-Ag) by simply introducing Ag+ into the aqueous suspension of aggregated melem particles. Notably, as the reaction progresses, the melem disappears, and the morphology of the newly formed complex spontaneously evolves from nanofibers to single-crystalline blocks, which possess the same chemical structure, indicating that the morphology evolution is driven by Ostwald ripening. The structure of melem-Ag displays infinite nanocages of triangular pyramids consisting of melem molecules and Ag+, linked via Ag-N coordinate bonding and Ag-Ag argentophilic interactions. It is noteworthy that Ag+ is the only transition-metal cation that reacts with melem suspensions, even in the presence of other transition-metal cations (Co2+, Ni2+, Cu2+, and Zn2+). The coordination of Ag+ to melem results in metal-to-ligand charge transfer (MLCT), resulting in a quenched photoluminescence and enhanced light absorption. Exposing the melem-Ag crystals to UV light for varying time intervals results in the formation of colorful powders, which may be used for Ag-decorated photocatalysts.

Silver induced chirality controlled spin filtration observed in ss-DNA functionalized with MoS2.

Chiral molecules can exhibit strong spin-orbit coupling, which can result in a large spin polarization. This is due to the fact that the energy levels of the electrons in a chiral molecule are strongly influenced by the chiral structure of the molecule, which can result in the separation of the energy levels for electrons with different spin orientations. We report a controlled spin-selective transmission of electrons through 20 base-paired poly-cytosine molecules functionalized with MoS2 flakes on ITO glass via the quantum mechanical tunneling effect. A reversion in spin polarization was observed after the silver ions interact with poly-cytosine due to the strong coordination of Ag(I) with cytosine-cytosine (C-C) mismatches, indicating the formation of duplex structural motifs, as confirmed by the circular dichroism spectroscopy at room temperature. Manipulating the spin of an electron through such a small molecule merely controlled by special cations could pave the way for major advances in spin-independent charge transport, advanced bioanalytical system design, and related applications.

Cyclometalated luminescent platinum(II) complexes of dissymmetrical 2,2':4',2''-terpyridine and its self-assembled dimer presenting Pt-Ag dative bonds.

A series of cyclometalated (N^C^N) Pt(II)-platinum complexes featuring a terpyridine ligand with a non-coordinating nitrogen atom and a Pt-C bond was synthesized. In the presence of Ag+, the bis(isonitrile)Pt(II) complex formed a remarkable self-assembled helicoidal dimer stabilized by coordination of Ag(I) and metallophilic Pt-Ag interactions. Its assembly was observed in the solid state and maintained in solution. All complexes show strong luminescence and multiple emitting states, which could be rationalized based on solid state X-ray structures and coordinating environment.

Reaction mechanism of acetonitrile, olefins, and amines catalyzed by Ag2CO3: A DFT investigation

AbstractThe mechanism of Ag2CO3‐catalyzed reactions of acetonitrile, olefins, and amines was investigated by using the M06‐L‐D3/6‐311 + G(d,p) method and level, and solvation model based on solute electron density (SMD) model was applied to simulate the solvent effect. Calculations show that the Ag2CO3 could achieve the Csp3‐H activation by coordinating with the terminal nitrogen atom of CH3CN; then, the addition reaction happened between the obtained Ag‐complex intermediate and olefin via the coordination of Ag and benzene ring; finally, the obtained radical intermediate continues to go through one single electron transfer (SET) process, addition reaction, and H‐shift reaction to yield the final product. The computational results reveal that Fe3+ cation would have assisted the SET process successfully and the path of direct addition with the amine is the optimal. Fukui function and dual descriptor can be used to predict the reactive sites, and electron spin density isosurface graphs can analyze the structures and reveal the substances.

Post-modified ligand exchange of UiO-66 with high-exposure rhodanine sites for enhancing the rapid and selective capture of Ag(I) from wastewater

Highly efficient capturing of silver from wastewater is critical for environmental and economic sustainability but remains significantly challenging to achieve fast kinetics and precise selectivity. Herein, we present two approaches based on rhodanine (Rd)-modified UiO-66 including post-modified ligand exchange for UiO-66-Rdp-m and in-situ solvothermal for UiO-66-Rdi-s. The resultant UiO-66-Rdp-m and UiO-66-Rdi-s perform maximum adsorption capacity of 120 and 109 mg·g−1, respectively, which are both about 6 times higher than pristine UiO-66. Benefitting from high-exposure Rd groups over the surface, UiO-66-Rdp-m exhibits about 3 times faster kinetic adsorption and nearly 15 times higher maximum selectivity coefficient than UiO-66-Rdi-s. Experiment and calculation demonstrate that the excellent performance of Rd-modified UiO-66 is dominantly owing to S chelation in the Rd group. In addition, site energy distributions of the Dubinin-Ashtakhov isotherm model confirm that UiO-66-Rdp-m has more effective sites for Ag(I) adsorption relative to UiO-66-Rdi-s. While a higher density of Rd outside the UiO-66-Rdp-m provides a larger coordination number of S/Ag (1.41) than UiO-66-Rdi-s (0.59), which is attributed to its sufficient exposed active S sites for multidentate coordination of Ag(I), thus significantly enhancing adsorption rate and selectivity. These findings are exploited to shed new insight into the design of adsorbents for the efficient recycling of noble metals from water.

Rapid gelation of dual physical network hydrogel with ultra‐stretchable, antifreezing, moisturing for stable and sensitive response

AbstractDual physical network hydrogel possesses robust energy dissipation mechanism. However, the demanding conditions of the second monomer radical polymerization aren't benefit for the dispersion of conductive filler. Moreover, the stable and sensitive response under extreme environment puts forward the requirements for mechanical, antifreezing and moisture retention properties. Herein, a dual physical networks hydrogel (polyacrylic acid‐chitosan‐graphene/glycerol, noted as PAA‐CS‐G/Gly) was prepared rapidly (<0.5 h) without chemical cross‐linking agents at room temperature. The rapid gelation, ionic coordination of Ag+ together with certain viscosity chitosan promoted the dispersion of graphene. PAA‐CS‐G/Gly showed ultra‐stretchable properties (~2500%), good toughness (3.11 MJ/m3), breaking strength (0.27 MPa) and fatigue resistance. PAA‐CS‐G/Gly had good adhesion properties, outstanding tolerance for freezing (−80°C) and moisture retention. More importantly, PAA‐CS‐G/Gly strain sensor had excellent sensitivity (GF, up to 9.449) at 300% ~ 900% strain. It could sensitively detect human joint movements and even subtle activities such as talking and swallowing. PAA‐CS‐G/Gly hydrogel is expected to adhere directly to the human body for flexible monitoring of human size movement under extreme environmental conditions.

A highly selective Hg2+ colorimetric sensor and antimicrobial agent based on green synthesized silver nanoparticles using Equisetum diffusum extract.

Plasmonic nanoparticles such as Ag have gained great interest in the biomedical domain and chemical analysis due to their unique optical properties. Herein, we report a simple, cost-effective, and highly selective colorimetric sensor of mercury(ii) based on E. diffusum (horsetail) extract-functionalized Ag nanoparticles (ED-AgNPs). The ED-AgNPs were synthesized by exploiting the coordination of Ag+ with the various functional groups of ED extract under sunlight exposure for only tens of seconds. ED-AgNPs (63 nm) were characterized using various techniques such as UV-vis, FTIR, DLS, SEM and EDX. FTIR spectra suggested the successful encapsulation of the AgNPs surface with ED extract and XRD confirmed its crystalline nature. This ED-AgNPs colorimetric sensor revealed remarkable selectivity towards Hg2+ in aqueous solution among other transition metal ions through a redox reaction mechanism. Besides, the sensor exhibited high sensitivity with rapid response and a detection limit of 70 nM. The sensor demonstrated feasibility for Hg(ii) detection in spiked tap and river water samples. In addition, the synthesized ED-AgNPs revealed enhanced antimicrobial activity with higher efficacy against the Gram-positive bacterium (L. monocytogenes with an inhibition zone of 18 mm) than the Gram-negative bacterium (E. coli with an inhibition zone of 10 mm). The simplicity and adaptability of this colorimetric sensor render it a promising candidate for on-site and point-of-care detection of heavy metal ions in diverse conditions.

Anion-Controlled Assembly of a Silver-Responsive Bifunctional Coordination Polymer with Detection and Large Adsorption Capacity.

The recognition and adsorption of silver ions (Ag+) from industrial wastewater are necessary but still challenging. Herein, we constructed four Zn(II)-based coordination polymers (CPs), namely, [Zn(btap)2(NO3)2]n (1), [Zn(btap)(SO4)(H2O)3]n (2), {[Zn(btap)2(H2O)2]·(ClO4)2}n (3), and [Zn(btap)Cl2]n (4), by using 3,5-bis(triazol-1-yl)pyridine (btap) with different anionic Zn(II) salts. The crystal structures of 1-4, varying from one-dimensional beaded (1) and zigzag chain (2) to two-dimensional sql (3) and bex (4) typologies, were regulated by the coordination modes of btap and the counter-anions. The water stability, pH stability, thermostability, and luminescent properties of the CPs were investigated. The luminescence performances in a series of cations and anions were also explored. Considering the high density of chloride groups in the structure, 4 showed luminescence sensing for Ag+ [KSV = 9188.45 M-1 and a limit of detection (LOD) of 4.9 μM], as well as an excellent ability for Ag+ adsorption in aqueous solution (maximum adsorption capacity, 653.3 mg/g). Additionally, anti-interference experiments revealed that 4 had excellent recognition and adsorption capacities for Ag+ even when multiple ions coexisted. Moreover, XRD, EDS, and XPS analyses confirmed that the coordination of Ag+ with chloride groups in 4 resulted in excellent adsorption capacity and prevented ligand-to-ligand electron transfer, showing excellent detection ability. Suitable coordination sites were introduced to interact strongly with Ag+, along with detection and large adsorption capacity. Our strategy can effectively design and develop multifunctional CP-based materials, which are applicable in removal processes and environmental protection, by regulating anions in the self-assembly and introducing CP functional groups.

Synergistic antibacterial and wound-healing applications of an imidazole-based porous organic polymer encapsulated silver nanoparticles composite

Here, a novel antibacterial agent (IM-POP-Ag) through encapsulation of Ag nanoparticles (AgNPs) into an imidazole-based porous organic polymer (IM-POP) was developed for synergistic antibacterial and wound healing. IM-POP with an ultrahigh N content of 38.42 at% was synthesized via the copolymerization of cheap and industrially mass-produced imidazole-2-carbaldehyde and melamine, via catalyst-free Schiff base chemistry, which could realize the effectively anchor of Ag on the porous skeleton (with an Ag loading of 26.01 wt%), avoiding the aggregation and reducing the toxicity of AgNPs greatly. The inherent porosity of POP realizes the effectively control on the size of AgNPs and the coordination of Ag+ changed imidazole into imidazolium, gifting the antibacterial activity to the carriers. As a result, IM-POP-Ag presented a synergistic antibacterial activity against both Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli.). For example, at the same Ag content, the survival rates of E. coli and S. aureus in response to 200 μg mL−1 IM-POP-Ag (equivalent to 50 μg mL−1 AgNPs) were 3.44 ± 0.21% and 6.34 ± 0.40%, respectively, far outperforming that of bare AgNPs (12.19 ± 0.54% and 20.20 ± 0.19%). In vivo experiments on mice testified IM-POP-Ag could significantly promote the healing rate of infected wounds which could facilitate the growth of vessel and hair follicle, accelerating epithelialization. Hence, this novel and mass-produced antibacterial agent provides a new strategy and theoretical basis for the application of AgNPs with higher efficacy and biocompatibility in the near future.

Antibacterial Cellulose Nanocrystal-Incorporated Hydrogels With Satisfactory Vascularization for Enhancing Skin Regeneration.

Wound healing of skin defects remains a significant clinical problem due to inflammation, infection, and dysangiogenesis; especially, the promotion of microvasculature formation in healing of chronic wound or deep skin defects is critical as it supplies oxygen and nutrients to the impaired tissue, relieving uncontrolled inflammatory responses. The cellulose nanocrystals (CNCs) in the liquid crystalline phase, which facilitates cell proliferation and migration, has been shown to improve vascularization effectively. Therefore, we developed a novel injectable hydrogel based on Schiff base and coordination of catechol and Ag. The obtained hydrogels (CCS/CCHO-Ag) exhibited in situ forming properties, satisfactory mechanical performance, controlled release of Ag, antibacterial capacity, and biocompatibility. In addition, the hydrogels could also entirely cover and firmly attach wounds with irregular shapes, so as to reduce the re-injury rate. More importantly, experiments in vitro and in vivo demonstrated that CCS/CCHO-Ag hydrogels can promote neovascularization and tissue regeneration, thanks to their anti-inflammatory and antibacterial effects. In conclusion, these multifunctional hydrogels are well on the way to becoming competitive biomedical dressings, which show tremendous potential application in the field of tissue engineering.

Connecting morphology and photoluminescence emissions in β-Ag2MoO4 microcrystals

This work elucidates the morphology-photoluminescence (PL) emission relationships, based on experimental and calculated results, on β-Ag 2 MoO 4 samples synthesized by microwave-assisted hydrothermal method. It was shown that the solvent (water and ammonia) and temperature (120, 130, 140, and 150 °C) play a crucial role in the morphology and PL emissions. A crystal structure model, composed by the local coordination of both Ag and Mo atoms at bulk and exposed surfaces, was built, and the possible mechanism along the synthesis progress was proposed and analyzed. This study provides an idea for the preparation and development of β-Ag 2 MoO 4 based materials with desirable properties.

Mechanical response of silver/polyvinyl alcohol thin film: From one-step and cyclic nanoindentation

Polymer nanocomposite and its mechanical properties are the area of immense interest for material developers in academia and industry. Present study investigates mechanical behavior of novel hexagonal bipyramidal Silver-Poly (vinyl alcohol) nanocomposites (Ag/PVA NCs) thin film fabricated using aqua-mediated in-situ reduction at room temperature. Specimen was characterized through UV-Visible (λmax = 417 nm), PL (λ(em) = 482 nm), XRD (average crystallite size 29.7 nm and preferential growth of thin film along [111] plane), TEM (hexagonal bipyramidal morphology, size ∼26.25 nm), TGA (increased thermal stability), FTIR (peaks at 945, 604 cm-1 confirms coordination of Ag and PVA matrix) and SAED. Depth sensing single-step and multi-step nanoindentation was employed to extract material’s sensitive mechanical property. Hardness (H: 0.352 to 0.192 GPa) and elastic modulus (Er: 8.718 to 6.72GPa) decreased with increasing single-step loads (from 50 μN to 10 mN), which can be attributed to indentation size effect (ISE). Cyclic nanoindentation (p∼5 mN, 23 cycles) was performed to deeply understand material sensitive degree of dislocation-structure interaction for fatigue analysis. The reduction in % elastic recovery was found at higher loads. On account of smooth surface, elastic unloading (stiffness) values linearly (y = 1.3944x + 3.8676 with R2 = 0.9835) increased from cycle 1 to 23 and contact depth increases linearly (y = 0.0329x + 1.5697, R2 = 0.9901) with the number of cycles. Interpretation of p-h profile indicated H and Er decreases with increasing load, along with proceeding cycles and no fracture or breakage/ weakening of NCs / progressive and localized structural damage was observed which evidenced that surface was completely uniform and defect free.

Competition between the stabilizing effects of saturated alkyl substituents and pi bonds on complexes of silver ion (Ag+) with alkenes

AbstractThe coordination of Ag+ ions to alkenes is of both theoretical and practical interest. While much attention has been paid to how the nature of the C=C π bond affects the coordinative process, little attention has been directed toward the effect of saturated side chains on complex stabilization despite experimental evidence suggesting its importance. Calculations employing the M06‐2X DFT functional have revealed that saturated chains can exhibit as powerful a stabilizing effect on Ag+/alkene complex formation as increased alkyl substitution about the C=C bond. Natural bond orbital (NBO) analysis confirms the mechanism of stabilization to be that of agostic interactions of properly‐oriented CH σ‐bonds in the saturated chain with the Ag+ ion. Analysis by the extended transition state energy decomposition approach with the natural orbital for chemical valence method (ETS‐NOCV) and the reduced density gradient (RDG) model were used to better characterize the nature of the interaction as a near equivalent combination of electrostatic and orbital interactions.

In situ thermal-induced generation of {Ag0AgI} dimer within Co-Ag phosphonates

The thermal decomposition of AgNO3 is known to produce metallic Ag, but single-atomic dispersion is hard to achieve instead of the aggregation state of nanoparticles. Herein, we develop an efficient approach to thermally generate and stabilize single Ag atoms via the coordination effect. Two desired Co-Ag phosphonates [AgI2CoIII2(notpH3)2(NO3)]X [X = NO3− (1) or ClO4− (2)] were synthesized by solid-phase grinding method or solution crystallization. Both crystal structures reveal slightly different packing arrangements of various lattice anions and identical one-dimensional (1-D) coordination chains, formed in each case by the coordination of Ag(I) to the metalloligand Co(notpH3) and NO3− anion. The number of Ag(I) ions connected to each NO3− anion reduces from 5 in bulk AgNO3 to 2 in compounds 1 and 2, leading to the AgNO3 component stepwise decomposition at a lower temperature (<300 °C). During the thermal decomposition, the changes of supermolecular structures and Ag oxidation states were monitored by PXRD, IR and XAFS measurements. The most interesting finding is that 1 and 2 can retain chain structures and harvest Ag(0) atoms in the chain by controlling decomposition temperatures (220 °C for 1 and 254 °C for 2).

Conformational Adaptation of β-Peptide Foldamers for the Formation of Metal-Peptide Frameworks.

Metal-coordinated frameworks derived from small peptidic ligands have received much attention thanks to peptides' vast structural and functional diversity. Various peptides with partial conformational preferences have been used to build metal-peptide frameworks, however, the use of conformationally constrained β-peptide foldamers has not been explored yet. Herein we report the first metal-coordination-mediated assembly of β-peptide foldamers with 12-helical folding propensity. The coordination of Ag+ to the terminal pyridyl moieties afforded a set of metal-peptide frameworks with unique entangled topologies. Interestingly, formation of the network structures was accompanied by notable conformational distortions of the foldamer ligands. As the first demonstration of new metal-peptide frameworks built from modular β-peptide foldamers, we anticipate that this work will be an important benchmark for further structural evolution and mechanistic investigation.

Conformational Adaptation of β‐Peptide Foldamers for the Formation of Metal–Peptide Frameworks

AbstractMetal‐coordinated frameworks derived from small peptidic ligands have received much attention thanks to peptides’ vast structural and functional diversity. Various peptides with partial conformational preferences have been used to build metal–peptide frameworks, however, the use of conformationally constrained β‐peptide foldamers has not been explored yet. Herein we report the first metal‐coordination‐mediated assembly of β‐peptide foldamers with 12‐helical folding propensity. The coordination of Ag+ to the terminal pyridyl moieties afforded a set of metal–peptide frameworks with unique entangled topologies. Interestingly, formation of the network structures was accompanied by notable conformational distortions of the foldamer ligands. As the first demonstration of new metal–peptide frameworks built from modular β‐peptide foldamers, we anticipate that this work will be an important benchmark for further structural evolution and mechanistic investigation.

Versatile Coordination of AgI and CuI Ions towards cyclo-As5 Ligands.

The reactions of the cyclo‐As5 complex [Cp*Fe(η5‐As5)] (B) with the AgI and CuI salts of the weakly coordinating anion (WCA) [FAl{OC6F10(C6F5)}3]− ([FAl]−) are studied. These reactions allow the synthesis of the mononuclear complexes [M(η5 : η2‐B)2][FAl] (M=Ag (1), Cu (2)) when a ratio of B/M(FAl) 2 : 1 is used. Compound 1 shows an unusual disorder of the central AgI cation between two π‐coordinating cyclo‐As5 ligands, which is absent in 2 pointing to a weak interaction of the Ag center towards the cyclo‐As5 ligands in B. When the ratio of B/Ag(FAl) is changed to 3 : 1 or 1 : 1, the respective coordination compounds [Ag(η2‐B)3][FAl] (3) and [Ag2(η2 : η2‐B)2][FAl]2 (4) are accessible. The coordination modes of the cyclo‐As5 units in 1, 3 and 4 are all different, reflecting the adaptive coordination behavior of B towards AgI ions. The optimized geometries in the gas phase of 1–4 are determined by DFT calculations to support the bonding situation observed in their solid‐state structures.

A closed-loop sustainable scheme for silver recovery from water by reusable thiol-grafted graphene oxide

Two-dimensional graphene oxide was modified with mercaptoethylamine and then treated with sodium dithionite to produce a 3D thiol-grafted graphene oxide (TGO) composite, which was investigated for the highly selective recovery of silver ions from water. Scanning electron microscopy, powder X-ray diffraction, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy were used to characterize the material before and after Ag+ adsorption. Batch adsorption experiments were carried out as a function of the initial Ag+ concentration, agitation time, temperature, and pH. The maximum adsorptive capacity of Ag+ by TGO, obtained from the Langmuir model, which fit the isotherm data well, reached 134.1 mg/g at 25 °C and a pH of 5.0. In addition, the adsorption was an endothermic process, and the adsorption kinetics followed the pseudo-second-order model. TGO was highly selective for Ag+; the selectivity factor of Ag+ reached 445 compared to Cu2+ ions and exceeded 1900 compared to Zn2+, Mg2+, Ca2+, Na+, and K+ ions. The adsorption of Ag+ on TGO induced the release of H+, and increased adsorption with increasing pH was observed. The adsorbed Ag+ can be proportionally desorbed using 1% HNO3. The reusability of TGO was confirmed by five cycles of adsorption-desorption-regeneration. The adsorption column studies indicated that TGO was stable in water and can be used as a filtering material for Ag+ recovery. The binding mechanism of Ag+ by TGO was proposed as the coordination of Ag+ with the sulfur atom of the mercapto groups attached to TGO followed by the reduction of Ag+ to Ag0.