Ag Coordination Research Articles

Self-Assembled Nanohelixes Driven by Host-Guest Interactions and Metal Coordination.

Helical nanostructures fabricated via the self-assembly of artificial motifs have been a captivating subject because of their structural aesthetics and multiple functionalities. Herein, we report the facile construction of a self-assembled nanohelix (NH) by leveraging an achiral aggregation-induced emission (AIE) luminogen (G) and pillar[5]arene (H), driven by host-guest interactions and metal coordination. Inspired by the "sergeants and soldiers" effect and "majority rule" principle, the host-guest complexation between G and H is employed to fixate the twisted conformation of G for the generation of "contortion sites", which further induced the emergence of helicity as the 1D assemblies are formed via Ag(I) coordination and hexagonally packed into nano-sized fibers. The strategy has proved feasible in both homogeneous and heterogeneous syntheses. Along with the formation of NH, boosted luminescence and enhanced productivity of reactive oxygen species (ROS) are afforded because of the efficient restriction on G, indicating the concurrent regulation of NH's morphology and photophysical properties by supramolecular assembly. In addition, NH also exhibits the capacity for bacteria imaging and photodynamic antibacterial activities against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli).

Self‐Assembled Nanohelixes Driven by Host‐Guest Interactions and Metal Coordination

Helical nanostructures fabricated via the self‐assembly of artificial motifs have been a captivating subject because of their structural aesthetics and multiple functionalities. Herein, we report the facile construction of a self‐assembled nanohelix (NH) by leveraging an achiral aggregation‐induced emission (AIE) luminogen (G) and pillar[5]arene (H), driven by host‐guest interactions and metal coordination. Inspired by the “sergeants and soldiers” effect and “majority rule” principle, the host‐guest complexation between G and H is employed to fixate the twisted conformation of G for the generation of “contortion sites”, which further induced the emergence of helicity as the 1D assemblies are formed via Ag(I) coordination and hexagonally packed into nano‐sized fibers. The strategy has proved feasible in both homogeneous and heterogeneous syntheses. Along with the formation of NH, boosted luminescence and enhanced productivity of reactive oxygen species (ROS) are afforded because of the efficient restriction on G, indicating the concurrent regulation of NH's morphology and photophysical properties by supramolecular assembly. In addition, NH also exhibits the capacity for bacteria imaging and photodynamic antibacterial activities against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli).

Thermally and Photoinduced Spin-Crossover Behavior in Iron(II)-Silver(I) Cyanido-Bridged Coordination Polymers Bearing Acetylpyridine Ligands.

We report two new cyanido-bridged Fe(II)-Ag(I) coordination polymers using different acetylpyridine isomers, {Fe(4acpy)2[Ag(CN)2]2} 1 and {Fe(3acpy)[Ag(CN)2]2} 2 (4acpy = 4-acetylpyridine; 3acpy = 3-acetylpyridine) displaying thermally and photoinduced spin crossover (SCO). In both cases, the acetylpyridine ligand directs the coordination polymer structure and the SCO of the materials. Using 4-acetylpyridine, a two-dimensional (2D) structure is observed in 1 made of layers stacked on each other by silver-ketone interactions leading to a complete SCO and reversible thermally and photoswitching of the magnetic and optical properties. Changing the acetyl group to a 3-position, a completely different structure is obtained for 2. The unexpected coordination of the carbonyl group to the Fe(II) centers induces a three-dimensional (3D) structure, leading to statistical disorder around the Fe(II) with three different coordination spheres, [N6], [N4O2], and [N5O]. This disorder gives rise to an incomplete thermally induced SCO with a poor photoswitchability. These results demonstrate that the choice of the acetyl position on the pyridine dictates the structural characteristics of the compounds with a direct impact on the SCO behavior. Remarkably, this work opens interesting perspectives for the future design of Fe-Ag cyanido coordination polymers with judiciously substituted pyridine ligands to tune the thermally and photoinduced SCO properties.

Hybrid Ethylcellulose Polymeric Films: Ag(I)-Based Components and Curcumin as Reinforcing Ingredients for Enhanced Food Packaging Properties.

Bio-active ethylcellulose (EC) polymeric films have been obtained by incorporating curcumin (curc) and Ag(I)-based compounds, known for their antioxidant and antimicrobial activity, respectively, within the polymeric matrix. The recently reported Ag(I) coordination polymer, in both its structural forms (α-[(bpy)Ag(OTf)]∞ and β-{[(bpy)Ag][OTf]}∞), and the [(bpy)Ag(OTf)]∞-curc polymeric co-crystal (bpy=2,2'-bipyridine; OTf=trifluoromethanesulfonate) have been selected as Ag(I) species. The hybrid composite films have been prepared through the simple solvent casting method and characterized through Powder X-Ray Diffraction (PXRD), Differential Scanning Calorimetry (DSC) and Fourier Transform Infrared (FTIR) spectroscopy, Scanning Electron Microscope (SEM), UV-vis spectroscopy. The deep investigation of the film samples highlighted the non-inert behaviour of EC towards these specific active ingredients. Antimicrobial tests showed that EC films embedding the Ag(I)-based compounds present good antimicrobial performance, in particular against Staphylococcus aureus, used as a model of Gram-positive bacteria. In addition, Silver migration tests, performed on the Ag(I)-incorporating EC films, evidenced low values of silver release particularly in the case of the EC films incorporating [(bpy)Ag(OTf)]∞-curc.

A practical synthesis and X-ray crystal structure of (E)-4-(1-naphthylvinyl)pyridine and related compounds

The synthesis, structure, and photoreactivity of (E)-4-(1-naphthylvinyl)pyridine ((E)-4-1-nvp; 1) and its coordination compounds have been investigated. Synthesis of (1) via Wittig olefination resulted in a challenging isomer separation and purification process. By synthesizing (1) via a Horner–Wadsworth–Emmons reaction, high stereoselectivity and purity were achieved. The crystal structure of (1) revealed significant intramolecular rotation facilitated by CH···π interactions, ultimately preventing olefin stacking in both the solid-state structure of (1) and a cocrystal with a structural isomer. Novel Ag(I) and Zn(II) coordination complexes that utilize (1) as a ligand were also synthesized and fully characterized, facilitating the examination of the relationship between molecular planarity and secondary bonding contributions via Hirshfeld surface analyses. These findings deepen our understanding of intermolecular interactions involving (E)-4-1-nvp and offer insights for designing novel photoresponsive materials capable of solid-state [2 + 2] cycloaddition.

Retraction Note: One-Dimensional Ag(I) and Cu(I) Coordination Polymers Constructed from the Two N-donor Ligands: Structural Insights and Anti-brain Tumor Activity Evaluation

Retraction Note: One-Dimensional Ag(I) and Cu(I) Coordination Polymers Constructed from the Two N-donor Ligands: Structural Insights and Anti-brain Tumor Activity Evaluation

Ag(I) and Hg(II) Coordination Polymers Decorated from Fully Benzimidazole Substituted Cyclotriphosphazene Ligand and Adsorption Behaviour Against Methylene Blue

Ag(I) and Hg(II) Coordination Polymers Decorated from Fully Benzimidazole Substituted Cyclotriphosphazene Ligand and Adsorption Behaviour Against Methylene Blue

Bioactive Ag(I) coordination complexes as dopants for castor oil plasticized ethylcellulose films.

The effects exerted by new bioactive acylpyrazolonate Ag(I) derivatives of the general formula [Ag(QPy,CF3)(R-Im)] containing different substituents on the imidazole (R-Im) ancillary ligands and the natural plasticizer castor oil when both are added to the ethylcellulose (EC) biopolymer in the preparation of thin films as potential active food packaging materials are presented. The Ag(I) complexes [Ag(QPy,CF3)(Bn-Im)] and [Ag(QPy,CF3)(Bu-Im)], having benzyl and butyl substituents, whose single crystal molecular structures are reported, have proved to be highly compatible for efficient incorporation between the EC polymer and the hydrophobic plasticizer chains, giving rise, even at low concentrations, to homogeneous, robust and elastic films. The concomitant presence of these Ag(I) complexes and castor oil in the polymer EC matrix gives rise to thin films with improved antibacterial activity against Escherichia coli (E. coli) as a model of Gram-negative bacterial strains when compared to the non-plasticized ones, with very low Ag(I) migration in the three food simulants used (distilled water, ethanol 10% v/v and acetic acid 3% v/v) under two assay conditions (70 °C for 2 h and 40 °C for 10 days).

Anion-induced chiral assembly: construction of Ag(i) coordination polymers for photocatalytic degradation of organic dyes

Assembly of a racemic ligand with different Ag(i) salts leads to homo/heterochiral polymers. The photocatalytic experiments indicate CPs 4–8 are active for the degradation of rhodamine B and methylene blue under UV irradiation.

Structural, spectroscopic, and chemical bonding analysis of luminescent bis(diphenylphosphino)methane derived binuclear heteroleptic silver(I) complex of norharmane with argentophilic interaction

Silver(I) coordination compounds have a fascinating geometrical diversity, the ability to have different coordination numbers (typically from 2 to 4), and the ability to form argentophilic (Ag∙∙∙Ag) interactions. In this work, a binuclear Ag(I) heteroleptic complex with norharmane ‘β-carboline’ and bis(diphenylphosphino)methane (PP) ligands has been synthesized and characterized by various spectroscopic and single-crystal X-ray diffraction analyses. The bonding of Ag(I) coordination and Ag···Ag interaction is explored in depth. The theoretical approaches employed were perturbation theory within the context of the natural bond orbital (NBO) framework, quantum theory of atoms in the molecule (QTAIM), and electron localization function (ELF) analysis.

Synthesis, X-ray Structures and Hirshfeld Analysis of Two Novel Thiocyanate-Bridged Ag(I) Coordination Polymers

Two novel silver(I) coordination polymers, [Ag(4BP)(SCN)]n (1) and {(4BPH)+[Ag(SCN)2]−}n (2) (4BP = 4-benzoyl pyridine), have been synthesized. The two complexes were prepared using almost the same reagents, which were AgNO3, 4BP and NH4SCN. The only difference was the presence of 1:1 (v/v) HNO3 in the synthesis of 2. In the two complexes, the Ag(I) has distorted tetrahedral coordination geometry. The structure of both complexes and the involvement of the thiocyanate anion as a linker between the Ag(I) centers were confirmed using single-crystal X-ray diffraction. 4BP participated as a monodentate ligand in the coordination sphere of complex 1, while in 2 it is found protonated (4BP-H)+ and acts as a counter ion, which balances the charge of the anionic [Ag(SCN)2]− moiety. The thiocyanate anion shows different coordination modes in the two complexes. In complex 1, the thiocyanate anion exhibits a µ1,1,3 bridging mode, which binds three Ag(I) ions to build a boat-like ten-membered ring structure leading to a two-dimensional coordination polymer. In 2, there are mixed µ1,1 and µ1,3 bridging thiocyanate groups, which form the one-dimensional polymeric chain running in the a-direction. Several interactions affected the stability of the crystal structure of the two complexes. These interactions were examined using Hirshfeld surface analysis. The coordination interactions (Ag-S and Ag-N) have a great impact on the stability of the polymeric structure of the two complexes. Additionally, the hydrogen-bonding interactions are crucial in the assembly of these coordination polymers. The O…H (10.7%) and C…H (34.2%) contacts in 1 as well as the N···H (15.3%) and S···H (14.9%) contacts in 2 are the most significant. Moreover, the argentophilic interaction (Ag…Ag = 3.378 Å) and π- π stacking play an important role in the assembly of complex 2.

Preparation of pH-sensitive composite polyethersulfone membranes embedded by Ag(I) coordination polymer for the removal of cationic and anionic dyes

A pH-sensitive polyethersulfone (PES) membrane was prepared with the aid of newly synthesized Ag(I) coordination polymer (Ag(I)-CP) particles. Indicating obvious adsorptive property toward dyes, the Ag(I)-based metalorganic framework (MOF) was selected to be used as an additive to improve the dye selectivity of PES membranes for both cationic and anionic dyes. The performance examination and characterization of prepared membranes indicated the influence of Ag(I)-CP in PES membrane improvement. The effect of feed pH approved the membrane response to pH changes in dye removal results. By adjusting feed pH based on pHpzc of Ag(I)-CP, it is possible to remove both anionic and cationic dyes (97% of acid orange 7 (AO) & and 100% of methylene blue (MB)) from the effluent along with an enhanced permeated flux. The results offered a synergism in embedding Ag(I)-CP in PES membrane in dye removal efficiency. The additive particles can be applied with their natural size (200–300 nm) without severe influence on the uniformity of the membrane morphology if the optimum Ag(I)-CP content is considered.

2D and 3D Ag(I) coordination polymers with a 2-methylimidazole substituted cyclotriphosphazene ligand: Structures and dye adsorption properties

Coordination polymers are a promising crystalline framework for dye capture and separation in recent years. We are reporting herein the two new, Ag(I) coordination polymers, namely {[Ag3(MeIm-Cp)2](NO3)3}n (1) and {[Ag(MeIm-Cp)](CH3PhSO3)} (2), were synthesized from hexapodal-shaped 2-methylimidazole substituted cyclotriphosphazene, (MeIm-Cp). MeIm-Cp was characterised by 1H NMR, 31P NMR and mass analysis. Structure of each isolated compounds were assigned by single crystal X-ray crystallography. In complex 1, MeIm-Cp has a κ6N coordination mode by connecting six Ag(I) ions to constitute a 3D coordination framework whereas the ligand in complex 2 displays κ4N coordination mode via linking four Ag(I) ions together to create a 2D coordination polymer. Topologically, coordination polymer 1 exhibits a 4,4,6-connected three nodal net with point symbol {44.62}3{46.68.8}2, while coordination polymer 2 displays a four-connected network having the point symbol {43.63}. According to thermogravimetric analysis, the thermal stability of MeIm-Cp is higher than complexes. The synthesized coordination polymers were used for the adsorption of some cationic and anionic organic dyes in aqueous media, Dye adsorption studies were performed out using UV–Vis. absorption spectroscopy. Adsorption experiments show that complex 1 removes the anionic methyl orange (MO) and tartrazine (E102) from water but shows no adsorption behaviour toward the cationic methylene blue (MB).

Synthesis, crystal structures, photophysical and antibacterial properties of Ag(I) and Zn(II) coordination polymers based on a flexible bisacylhydrazone ligand

A flexible bisacylhydrazone ligand (H4L) was designed and synthesized from the condensation reaction of dialdehyde 3,3′-thiobis(methyiene)-bis-(5-methyl-salicylaldehyde) (b) with isonicotinic hydrazide. In the DMSO/methanol solution, two coordination polymers (CPs), formulated as {[Ag(H4L)NO3]·DMSO·2H2O}n (CP 1) and {[Zn2(H2L2-)2]·3DMSO·3H2O}n (CP 2), were synthesized from H4L with Ag(I) or Zn(II) ions, respectively. These two CPs were characterized via elemental analysis, FT-IR spectra, and single crystal X-ray determination. The results show that CP 1 exists as a 1D looped-chain polymer, while CP 2 exists as a 2D sheet polymer. The coordination configurations of the two CPs were analyzed and compared in detail, which disclose the terminal pyridyl nitrogen atoms exhibit obviously stronger coordination ability compared to other sites. In addition, photophysical, electrochemical and antibacterial properties of H4L and the two CPs were investigated.

3D Ag(I) coordination polymer sandwiched by water-muconate anionic layers: Synthesis, structure, Hirshfeld surface analysis, binding with BSA, and photocatalytic activity

The sonochemical reaction between silver salt, 1,3-bis(4-pyridylpropane (bpp) and trans,trans-muconic acid (H2muc) formed an Ag(I) coordination polymer with a 3D supramolecular sandwich architecture, {[Ag8(bpp)8(H2O)3].(muc)4.29(H2O)}n, (1) consisting of the silver-bpp cationic host that alternates with 2D water–muc guest anionic layers. The latter is formed by H-bonded water molecules-anions comprising hexagonal (H2O)6 clusters. The Hirshfeld surface and fingerprint plots have been used to quantify the weak intermolecular interactions in the crystal packing arrangement. The study showed that intermolecular hydrogen bonds are the most critical in constructing the titled supramolecular complex, accounting for 51.2% of the total Hirshfeld surface. Several spectrofluorimetric methods have been employed to investigate the binding interaction between Bovine Serum Albumin (BSA) and the titled complex. The complex induced significant fluorescence quenching of BSA, indicating a strong binding affinity for the protein. Static or ground state complex formation was envisaged as the primary quenching mechanism when the complex interacts with BSA. In addition, the Ag compound also offers photocatalytic properties by degrading the toxic organic methylene blue dye.

Five new luminescent Pb(II) and Ag(I) coordination polymers based on 1-(4-carboxybenzyl)-1H-pyrazole-3,5-dicarboxylic acid and different neutral ligands

Five new coordination polymers (CPs), namely {Pb1.5(L)} (1), {Pb3(L)2(2,2′-bpy)·2·5H2O} (2), {[Pb(HL)(phen)]·H2O} (3), {Ag2(HL)} (4) and {Ag(H2L)(phen)} (5), have been constructed by using 1-(4-carboxybenzyl)-1H-pyrazole-3,5-dicarboxylic acid (H3L) as an organic ligand. Compound 1 reveals a three-dimensional (3D) (4,6,7)-connected framework with the point symbol of {410·65}{46}2{48·613}2. Compound 2 exhibits a novel (3,6)-connected 3D framework based on a trinuclear Pb(II) cluster with point symbol {42.6}2{44.62.88.10}. Compound 3 is a 1D chain that is further assembled into a 3D supramolecular framework by hydrogen-bonds. Compound 4 shows a (3,6)-connected 3D structure based on a tetranuclear Ag(I) cluster with {4·62}2{42·610·83} topology. Compound 5 is a 0D structure, and can be further expanded into a 3D supramolecular network by various weak interactions. The solid-state luminescent spectra have been measured at room temperature. The results show that compounds 1–5 exhibit strong luminescent emission in the visible region, and can be tunable by varying excitation wavelengths.

Hydrogen evolution performance of a Ag(I) bis(benzimidazole) coordination polymer doped carbon paste composite electrode

A new Ag(I) coordination polymer, [Ag2(BBO)]n, H2BBO = 1,3-bis(benzimidazol-2-yl)-2-oxopropane, was synthesized by diffusion method and characterized. The structural analysis showed that the Ag(I) coordination polymer has a 2D layered structure, and each polymerization unit is composed of two BBO ligands and four Ag(I) ions, which form two types of structures (border silvers and center silvers). The hydrogen evolution reaction (HER) performance of the composite electrode CE-Ag formed by mixing the Ag(I) coordination polymer and carbon paste electrode was investigated by linear scanning voltammetry (LSV) and electrochemical impedance spectroscopy (EIS). The results showed that the overpotential (η10 298) of the obtained CE-Ag was positively shifted by 320 mV when the current density reached 10 mA cm−2 compared with the blank electrode (CE) and the Tafel slope of the CE-Ag was 158 mV dec−1. These indicated that CE-Ag was effective for the HER electrocatalytic reaction. In addition, the smaller charge transfer resistance Rct (40 Ω) of CE-Ag compared with that of CE (2263 Ω) further indicates the effective catalytic capacity of the Ag(I) coordination polymer for hydrogen evolution. The information obtained from this study will help to expand the application of Ag(I) coordination polymers in the field of electrochemistry.

Two one-dimensional silver(I) coordination polymer modified electrodes for hydrogen evolution reaction and H2O2 recognition

Two new Ag(I) coordination polymers (CPs), namely: [Ag4(m-MOPhHIDC)2(BBM)2]n (1) {[Ag(BBM)](NO3)}n (2) (m-MOPhHIDC = m-methoxyanisaldehyde imidazole dicarboxylate, BBM = 2,2-(1,4-butanediyl)bis-1,3-benzimidazole), have been synthesized by solvothermal method and characterized. Structural analyses show that both complexes are one-dimensional chain coordination polymers, but the one-dimensional chains have different shapes, in which CP-1 is "V" shaped, and CP-2 is "wave-shaped". The electrochemical properties of composite electrodes CE-1 and CE-2 formed by mixing two coordination polymers with carbon paste electrodes were investigated respectively. Electrocatalytic hydrogen evolution characteristics of two composite electrodes were investigated by linear scanning voltammetry (LSV) in 0.5 M H2SO4 electrolyte, at 298 K the results show that when the current density reaches 10 mA cm−2, their overpotential positively shifted by 284 and 289 mV compared to CE (905 mV). And the Tafel slope of the CE-1 and CE-2 was 162 and 164 mV dec−1, respectively. The CE-1 exhibited superior electrocatalytic ability than CE-2, which may be attributed to the different coordination modes of central silver ions in the two CPs. In addition, the composite electrodes CE-1 and CE-2 also have a good identification effect on H2O2, and the detection limits of 36.7 and 6.2 μM in the linear range of 0.5-4000 μM were determined by chronoamperometry. Results show that the Ag(I) CPs can be used as effective dualfunctional electrocatalysts.

Inhibition of Cancer Cell Proliferation and Bacterial Growth by Silver(I) Complexes Bearing a CH3-Substituted Thiadiazole-Based Thioamide

Ag(I) coordination compounds have recently attracted much attention as antiproliferative and antibacterial agents against a wide range of cancer cell lines and pathogens. The bioactivity potential of these complexes depends on their structural characteristics and the nature of their ligands. Herein, we present a series of four Ag(I) coordination compounds bearing as ligands the CH3-substituted thiadiazole-based thioamide 5-methyl-1,3,4-thiadiazole-2-thiol (mtdztH) and phosphines, i.e., [AgCl(mtdztH)(PPh3)2] (1), [Ag(mtdzt)(PPh3)3] (2), [AgCl(mtdztH)(xantphos)] (3), and [AgmtdztH)(dppe)(NO3)]n (4), where xantphos = 4,5-bis(diphenylphosphino)-9,9-dimethylxanthene and dppe = 1,2-bis(diphenylphosphino)ethane, and the assessment of their in vitro antibacterial and anti-cancer efficiency. Among them, diphosphine-containing compounds 3 and 4 were found to exhibit broad-spectrum antibacterial activity characteristics against both Gram-(+) and Gram-(-) bacterial strains, showing high in vitro bioactivity with IC50 values as low as 4.6 μΜ. In vitro cytotoxicity studies against human ovarian, pancreatic, lung, and prostate cancer cell lines revealed the strong cytotoxic potential of 2 and 4, with IC50 values in the range of 3.1-24.0 μΜ, while 3 and 4 maintained the normal fibroblast cells' viability at relatively higher levels. Assessment of these results, in combination with those obtained for analogous Ag(I) complexes bearing similar heterocyclic thioamides, suggest the pivotal role of the substituent groups of the thioamide heterocyclic ring in the antibacterial and anti-cancer efficacy of the respective Ag(I) complexes. Compounds 1-4 exhibited moderate in vitro antioxidant capacity for free radicals scavenging, as well as reasonably strong ability to interact with calf-thymus DNA, suggesting the likely implication of these properties in their bioactivity mechanisms. Complementary insights into the possible mechanism of their anti-cancer activity were provided by molecular docking calculations, exploring their ability to bind to the overexpressed fibroblast growth factor receptor 1 (FGFR1), affecting cancer cells' functionalities.

Unprecedented highly efficient photoluminescence in a phosphorescent Ag(I) coordination polymer.

A luminescent three-dimensional coordination polymer (CP) of [CdII(pmd){AgI(CN)2}2] (1; pmd = pyrimidine) comprising two different coordination modes of Ag+ ions was synthesised herein. 1 exhibited thermochromic luminescence, accompanied by positive thermal elongation of the Ag⋯Ag distance. Moreover, 1 showed a bright phosphorescence with the highest photoluminescence quantum yield (Φem), approximately 60% at room temperature, among previously reported phosphorescent Ag-based CPs or metal-organic frameworks.