Silver Complexes Research Articles

Evaluation of Salophen-Based Immobilized Copper Nanoparticles Biosynthesized Using Curcuma Longa Extract: Physicochemical Characterization and Biological Study

The treatment of infectious diseases has become more difficult today than in the past, as a result of the increasing resistance of pathogenic bacterial and fungal strains to antibiotics and antifungals. As a solution, it is necessary to design new antimicrobial agents to deal with these strains. Schiff bases and their metallic derivatives, especially silver and copper complexes, have a prominent place in the pharmaceutical industry due to their excellent inhibitory potential against microbial strains. In order to combine these inhibitory effects in a single compound, a novel Cu@Ag-salophen nanocomposite was prepared by immobilizing of biochemical synthesized copper nanoparticles from methanolic extract of Curcuma longa on an Ag(I) salophen Schiff base complex. The physicochemical characterization of prepared nanocomposite was attained by FTIR, UV/Vis, TEM, FESEM, EDAX, ICP-AES, and XRD analyses. All the synthesized compounds, including Schiff base ligand, Ag complex, Cu nanoparticles, and the Cu@Ag-salophen nanocomposite, were assessed for their potential activities on DPPH free radicals and 8 different pathogenic microorganisms. The IC50 values in the range of 4.02–71.49 μg/ml were assessed in DPPH scavinging studies, indicating their potential to be utilized as potent antioxidant agents to treat oxidative stress-related diseases. Among the tested compounds, the Schiff base ligand exhibited excellent antioxidant effects. Regarding the antimicrobial activities, the Schiff base ligand showed a wide spectrum of antimicrobial effects, with MIC, MBC, and MFC values ranging from 256 to 4096 μg/ml. However, the Ag complex alone did not exhibit any inhibitory effect against the tested microbial strains. Interestingly, when the copper nanoparticles were combined with it in the form of the Cu@Ag-salophen nanocomposite, the resulting material was able to prevent the growth of 5 out of 8 tested strains. Synergistic effects were observed with nanocomposite against P. aeruginosa, S. epidermidis, and A. fumigatus strains. These findings suggest that the functionalization of the ligand and the incorporation of additional nanoparticles could further improve the antimicrobial efficacy of the Cu@Ag-salophen nanocomposite, converting it into a more efficient antimicrobial agent.

In vitro and in silico anticancer potential of binuclear silver (I) N-heterocyclic carbene (NHCs) complexes: Investigation of interaction with surfactants

N-heterocyclic carbene (NHCs) silver complexes are getting tremendous attention for appealing biological potentials. The present study is planned to synthesize silver-NHC complexes to investigate their anticancer potential against breast, colon and ovarian cancer cell lines. The synthesized benzimidazolium salts (C1-C2) and their binuclear silver complexes (C3-C4) were assured through spectroscopy (UV–visible, FTIR, NMR and FLR), HPLC-DAD (high performance liquid chromatography), elemental analysis as well as mass spectrometry. Molecular docking studies indicated that compound C4 has lower binding energy values of −4.49, −1.95 and −2.95 kcal/mol for Bruton’s tyrosine kinase, Human topoisomerase II alpha and Aromatase cytochrome P450 protein targets respectively. The In Vitro cytotoxicity assay confirmed the C4 is better cytotoxic agent from other studied compounds of present study having lower IC50 values of 0.996 ± 0.04, 0.97 5 ± 0.04, 0.872 ± 0.05 and 0.987 ± 0.05 µg/mL against MCF-7, A-549, A-2780 and HCT-116 cell lines. Stability of compounds in solution form studied through spectroscopy and all compounds were found stable for studied course of time. Interactions of C3-C4 with surfactants (SDS, tween-20, tween-80) have confirmed the substantial interaction to improve aqueous solubility. Interaction of C3-C4 with surfactants indicates that there is potential affinity among test compounds and surfactants for complex formation spontaneously, having strongest binding affinity for SDS (sodium dodecyl sulfate) as compared to Tween-20 and Tween-80.

New Silver(I) Lawsone-based complexes: Synthesis, characterization, interaction with biological macromolecules, in vitro antineoplastic, antimetastatic, and antimicrobial activity

New silver(I) complexes of formula [Ag(Lw)]2 (1), [Ag(Lw)(B)], where (Lw= lawsonate, B = 2,2`bipyridine (bpy) (2), 1,10-phenanthroline (phen) (3) and [Ag(Lw)(PPh3)2], (PPh3=triphenylphosphine (4)) have been isolated and characterized using elemental analysis (C, H, N), and FTIR, NMR(1H, 13C and 31P), UV–visible spectroscopy along with thermal analysis and molar conductivity measurements. The resulting data showed that the lawsone coordinates to the Ag(I) as a mono-negative O,O-donor ligand. The interaction of the ligand and complexes with (ctDNA, calf thymus DNA, tRNA, yeast RNA, and BSA, bovine serum albumin) has been studied utilizing absorption and fluorescence spectroscopy. The binding constant data (Kb) revealed that the complexes interact with the biomolecules more strongly than the ligand (HLw). Furthermore, in vitro, cytotoxic activity against normal lung cells (WI38), and various malignant cells, including breast (MCF7 and MDA-231), and colon (HCT116) was studied using cisplatin as a standard drug. The IC50 and selective index (SI) data showed that complex (3) is more selective towards the HCT116 cells. Flow cytometric study of complex (3) revealed that cells are arrested in the G0/G1 phase and induced cell death by an apoptotic mechanism rather than necrosis. The anti-metastatic activity (wound healing) of complex (3) indicated its ability to prevent the migration of cancer cells. The antimicrobial activity of the compounds has been also studied against gram +ve, gram -ve bacteria, and yeast (C. Albican), using penicillin and miconazole, respectively as a reference to show that the complexes (1) and (3) possess the highest activity against these microorganisms.

Structure‐Activity Relationships of Glucose‐based PdII‐Bis(NHC) Complexes in a Model Suzuki‐Miyaura Reaction

AbstractThe authors of this work have optimized a novel synthetic route towards glucose‐based PdII‐bis(NHC) complexes in only 4 steps with total yields up to 73 %. The synthesis route encompasses an Appel reaction towards 6‐iodo‐glucopyranosides, followed by acyl‐protection, then quaternization with imidazoles and finally the conversion of these acyl‐protected glucosyl imidazolium salts to their respective palladium(II)bis(NHC) complexes, via an intermediary silver(I) complex. Overall, 11 acyl‐protected glucosyl imidazolium iodides as NHC‐precursors and 15 complexes have been synthesized. The structure‐activity relationships of different functionalizations in these complexes and their reactivity in a model Suzuki‐Miyaura between bromobenzene and 4‐tolueneboronic acid reaction has been investigated, and a highly reactive complex leading to >99 % yield at 0.005 mol% catalytic loading has been found.

Oxidation by Silver(III) Complex: Synthesis, Characterisation and Mechanisms of Un-catalysed and Catalysed Reactions

Oxidation by Silver(III) Complex: Synthesis, Characterisation and Mechanisms of Un-catalysed and Catalysed Reactions

Molecular recognition of dicyanoalkane guest in a cyclic dimeric silver(I) complex based on pillar[5]-bis-crown

We herein report the formation of the cyclic dimeric silver(I) complexes and the selective organic guest recognition. The reaction of pillar[5]-bis-crown with AgPF6 afforded a cyclic dimeric supramolecular complex [Ag4(L)2(H2O)2(CH3CN)2](PF6)4 in which the silver(I) atoms exist inside the crown ether cavities. The cyclic dimeric silver(I) complex reacts with 1,2-dicyanoethane (C2) to form a guest-inclusion complex [Ag4(C2@L)2(CH3CN)2](PF6)4, exhibiting its formation being controlled by the length of the guest molecules used. Additionally, the silver(I) supramolecular complex demonstrated molecular recognition for C2 in both solution and solid states.

Synthesis, characterization, crystal structure and anticancer study of symmetrical binuclear bis-N-heterocyclic carbene silver(I) complexes

The synthesis of binuclear silver(I)-NHC complexes from bis-benzimidazolium salts and silver(I) ions has been carried out via an in-situ deprotonation (NHC = N-heterocyclic carbene). The reaction between 1,3-dibromopropane and two moles of N-substituted alkyl benzimidazole (R = methyl, hexyl, heptyl, octyl, and 4-methyl-benzyl) resulted in the formation of bis-benzimidazolium salts, H2L‧2Br- (1–5). Subsequent reactions of the respective salts with excess Ag2O yielded the formation of bis-NHC binuclear silver(I) complexes with the formula of [Ag2L2]·2PF6 (Ag1-Ag5). All compounds were characterized by 1H and 13C NMR, FTIR, elemental analysis, molar conductivity measurement, melting point analysis, and solubility tests. Single crystal X-ray crystallography data reveals that Ag2 exists as a dinuclear complex with no significant intramolecular argentophilic interactions. Anticancer studies of salts 1-5 and complexes Ag1-Ag5 were carried out by employing breast cancer cell lines (MCF-7). None of the salts showed antiproliferative activity, while all the complexes possessed significant anticancer properties in a dose-dependent manner. The complexes indicate better activity than a positive control except for Ag4.

Silver(I) and Copper(I) Complexes of Dicarboxylic Acid Derivatives: Synthesis, Characterization and Thermal Studies

A family of silver(I) and copper(I) complexes containing carboxylate ligands were prepared from the corresponding carboxylic acids and Ag2O. The compounds were characterized by various spectroscopic methods and X-ray diffraction. In the solid state, the silver(I) salts are coordination polymers based on dinuclear silver species with bridging carboxylate ligands. The reaction of these silver salts with Ph3P gives four-coordinate, tetrahedral bis(phosphine) complexes. Analogous copper(I) bis(phosphine) compounds were prepared by the reduction of copper(II) carboxylates with Ph3P. Decomposition temperatures and thermal decomposition products were studied by TGA/DSC measurements. The metal compounds decomposed cleanly to their respective metals (silver or copper) at temperatures ranging from 206 to 338 °C.

Investigating the Suitability of Various Silver(I) Complexes for Use in a Cyanide-Free Silver Electrolyte

The suitability of various nitrogen, sulfur, oxygen, and phosphorus compounds as complexing agents in a silver electrolyte was examined by using potentiometric titration under practical conditions. The setup consisted of three electrodes to measure the pH and the activity of the silver ions simultaneously. Different ratios of silver to complexing agent from 1:10 to 1:1 at a constant ionic strength of 0.2 mol/L were investigated. The type of the complexes and their corresponding critical stability constants were evaluated by fitting the measured data using a self-developed algorithm. The pH and Nernst potential curve were calculated for the assumed complexes based on the law of mass action to find the best approximation. The correct definition of the occurring species is challenging and can lead to significant changes in the calculation of stability constants. For this reason, the measured silver potential curves were primarily used for the rating of the complexing agents. An evaluation of the measurements shows that the donor atom of the complexing agent and its ligand field strongly affected the stability and type of the complexes. Only a few complexing agents were found to be suitable for use in the cyanide-free silver electrolyte.

Acetylated galactopyranosyl N-heterocyclic monocarbene complexes of Silver(I) as novel anti-proliferative agents in a rhabdomyosarcoma cell line

Herein, four silver(I) complexes bearing acetylated d-galactopyranoside-based N-heterocyclic carbene ligands were synthesized and fully characterized by elemental analysis, NMR, and X-ray photoelectron spectroscopy. All complexes were obtained with an anomeric β-configuration and as monocarbene species. In this study, we investigated the biological effects of the silver(I) complexes 2a-d on the human rhabdomyosarcoma cell line, RD. Our results show concentration-dependent effects on cell density, growth inhibition, and activation of key signaling pathways such as Akt 1/2, ERK 1/2, and p38-MAPK, indicating their potential as anticancer agents. Notably, at 35.5 µM, the complexes induced mitochondrial network disruption, as observed with 2b and 2c, whereas with 2a, this disruption was accompanied by nuclear content release. These results provide insight into the utility of carbohydrate incorporated NHC complexes of silver(I) as new agents in cancer therapy.

Silver Complexes of Miconazole and Metronidazole: Potential Candidates for Melanoma Treatment.

Melanoma, arguably the deadliest form of skin cancer, is responsible for the majority of skin-cancer-related fatalities. Innovative strategies concentrate on new therapies that avoid the undesirable effects of pharmacological or medical treatment. This article discusses the chemical structures of [(MTZ)2AgNO3], [(MTZ)2Ag]2SO4, [Ag(MCZ)2NO3], [Ag(MCZ)2BF4], [Ag(MCZ)2SbF6] and [Ag(MCZ)2ClO4] (MTZ-metronidazole; MCZ-miconazole) silver(I) compounds and the possible relationship between the molecules and their cytostatic activity against melanoma cells. Molecular Hirshfeld surface analysis and computational methods were used to examine the possible association between the structure and anticancer activity of the silver(I) complexes and compare the cytotoxicity of the silver(I) complexes of metronidazole and miconazole with that of silver(I) nitrate, cisplatin, metronidazole and miconazole complexes against A375 and BJ cells. Additionally, these preliminary biological studies found the greatest IC50 values against the A375 line were demonstrated by [Ag(MCZ)2NO3] and [(MTZ)2AgNO3]. The compound [(MTZ)2AgNO3] was three-fold more toxic to the A375 cells than the reference (cisplatin) and 15 times more cytotoxic against the A375 cells than the normal BJ cells. Complexes of metronidazole with Ag(I) are considered biocompatible at a concentration below 50 µmol/L.

Syntheses and efficient phosphorescence of ionic silver(I) complexes based on benzothiazole-phosphine ligands

Two ionic mononuclear silver(I) complexes (1 and 2) with formula of [Ag(N^P)(Xantphos)]SbF6, where N^P = 2–(benzo[d]thiazol)–2–yl) diphenylphosphine derivatives, Xantphos = 4,5-Bis(diphenylphosphino)-9,9-dimethylxanthene, have been synthesized and characterized. Single crystal analysis reveals that the geometries around Ag(I) centers adopt distorted tetrahedron (1) and trigonal planar (2). In powder at 298 K, these complexes exhibit bright emissions with high photo-luminescent quantum yields of 55.2 % (1) and 46.7 % (2) and lifetimes of 0.426 ms (1) and 1.87 ms (2), respectively. The results suggested that these complexes containing bulky benzothiazole phosphine can realize efficient long-lived phosphorescence.

An experimental and computational studies, evaluating the in vitro antidiabetic and antioxidant activity, in silico prediction ADMET properties of 5‐chloro‐1H‐benzimidazole and its newly synthesized silver(I) complex

In this research, a new Ag(I) complex, namely, [Ag(5‐chloro‐1H‐benzimidazole)2(NO3)], has been synthesized using the benzimidazole‐based ligand 5‐chloro‐1H‐benzimidazole (5ClBZ). Ag(I) complexes were characterized by elemental analysis, UV‐Vis, FT‐IR, and1H NMR spectroscopy, and DFT analysis was used. The free ligand and its Ag(I) complexes were tried for their biochemical properties, including antioxidant and antidiabetic properties. To study the molecular structures of the title compounds, in silico ADME/Tox research was performed on the newly made complex and free ligand. The empirical guidelines relating to ADME were utilized to conduct molecular docking simulations and in‐depth drug‐likeness profiling. This was carried out to validate the conclusions and identify exact binding interactions. Based on the study's findings, it has been determined that these new compounds have significant potential as powerful therapeutic agents for controlling antioxidant and antidiabetic activities.

New silver, rhodium and iridium complexes with anthracene-functionalized N-heterocyclic carbene ligands: Crystal structures, cytotoxicity and fluorescence studies

In the present study, we have synthesized anthracene-functionalized metal complexes to investigate their cytotoxicity and photophysical properties. In this context, firstly, an Ag–NHC (NHC = N-heterocyclic carbene) complex (2a) has been synthesized by the interaction of Ag2O and N-(2-methylbenzyl)-N-((anthracen-9-yl)methyl)benzimidazolium chloride (1a). Corresponding Rh– (3a) and Ir–NHC (4a) complexes have also been synthesized by the transmetalation reaction between 2a and corresponding metal compounds. Additionally, for comparison purposes, an ether-functionalized Ag–NHC complex (2b) with N-(methoxyethyl)-N-((anthracene-9-yl)methyl)benzimidazole-2-ylidene ligand, and [AgL2]NO3 type complex (2c) with a N-coordinated N-((anthracen-9-yl)methyl)benzimidazole ligand have been synthesized. All complexes have been characterized by the combination of NMR and mass spectroscopic techniques, and elemental analyses. Moreover, solid state structures of 2a, 2b and 4a have been determined by the single crystal X-ray diffraction analysis. Cytotoxic potentials of all compounds have been tested against human lung adenocarcinoma alveolar basal epithelial cell line (A549) using the MTT assay, and all complexes performed strong anti-proliferative activity. Stability studies have disclosed that only 1a and 2c are able to retain their structure in the culture medium (DMEM) that biological assays were carried out. Photophysical measurements revealed that all compounds have similar emission bands because of the conjugation of anthracene group. Finally, 1a and 2c have been visualized by fluorescence confocal microscopy to investigate cellular uptake and subcellular distribution of the complexes, and the findings indicated that both compounds dispersed along the cell membranes nuclear regions.

Selective Tautomer Production and Cryogenic Ion Spectroscopy of Radical Cations: The Uracil and Thymine Cases.

The vibrational and electronic spectroscopy of the radical cations of two nucleobases (NB) (uracil and thymine) was studied by cryogenic ion photodissociation spectroscopy. The radical cations have been generated from the photodissociation of NB-Ag+ complexes. A charge transfer process from the NB to Ag+ governs the deactivation mechanism, leading to the formation of the radical cation without further tautomerization. Single- and double-resonance spectroscopy allows for structural assignments of both the silver complexes and the radical cations by comparison with DFT-based calculations. Interestingly, a tautomer-dependent fragmentation is observed in the thymine enol form that involves the loss of NCO, a fragment which was never reported before for this NB. This selective photodissociation of silver complexes containing aromatic chromophore greatly expands the current technique to produce isomer-selected radical cations in the gas phase providing benchmark experimental data to assess calculations of open-shell species.

Synthesis and Photophysical Properties of Silver(I) Coordination Polymers Bridged by Dimethylpyrazine: Comparison of Emissive Excited States between Silver(I) and Copper(I) Congeners.

Highly luminescent silver(I) coordination polymers [Ag2X2(PPh3)2(Me2pyz)]n (X = I, Br, Cl; Me2pyz: 2,5-dimethylpyrazine) were prepared together with copper congeners [Cu2X2(PPh3)2(Me2pyz)]n (X = I, Br). All the complexes showed thermally activated delayed fluorescence from the charge-transfer states in the visible region, from blue to red. The isomorphous relationship among the complexes allowed a detailed discussion of the effect of halogenido ligands and crystal packing on their luminescence energy. The relaxation in the emissive excited states (ESs) was determined to be more remarkable in silver complexes than in copper complexes despite their isomorphous structures, and the electronic effect of halogenido ligands was comparable to the effect of relaxation in emissive ESs.

Silver(I) complexes with voriconazole as promising anti-Candida agents

Recognizing that metal ions play an important role in modifying the pharmacological properties of known organic-based drugs, the present manuscript addresses the complexation of the antifungal agent voriconazole (vcz) with the biologically relevant silver(I) ion as a strategy for the development of new antimycotics. The synthesized silver(I) complexes with vcz were characterized by mass spectrometry, IR, UV–Vis and NMR spectroscopy and single-crystal X-ray diffraction analysis. The crystallographic results showed that complexes {[Ag(vcz)(H2O)]CH3SO3}n (1), {[Ag(vcz)2]BF4}n (2) and {[Ag(vcz)2]PF6}n (3) have polymeric structures in the solid state, in which silver(I) ions have a distorted tetrahedral geometry. On the other hand, DFT calculations revealed that the investigated silver(I) complexes 1–3 in DMSO exist as linear [Ag(vcz-N2)(vcz-N19)]+ (1a), [Ag(vcz-N2)(vcz-N4)]+ (2a) and [Ag(vcz-N4)2]+ (3a) species, respectively. The evaluated complexes showed an enhanced anti-Candida activity compared to the parent drug with minimal inhibitory concentration (MIC) values in the range of 0.02–1.05 μM. In comparison with vcz, the corresponding silver(I) complexes showed better activity in prevention hyphae and biofilm formation of C. albicans, indicating that they could be considered as promising agents against Candida that significantly inhibit its virulence. Also, these complexes are much better inhibitors of ergosterol synthesis in the cell membrane of C. albicans at the concentration of 0.5 × MIC. This is also confirmed by a molecular docking, which revealed that complexes 1a – 3a showed better inhibitory activity than vcz against the sterol 14α-demethylase enzyme cytochrome P450 (CYP51B), which plays a crucial role in the formation of ergosterol.

Tuning the CO2 Reduction Selectivity of an Immobilized Molecular Ag Complex beyond CO.

The electrochemical reduction of carbon dioxide (CO2) to produce fuels and chemicals has garnered significant attention. However, achieving control over the selectivity of the resulting products remains a challenging task, particularly within molecular systems. In this study, we employed a molecular silver complex immobilized on graphitized mesoporous carbon (GMC) as a catalyst for converting CO2 into CO, achieving an impressive selectivity of over 90% at -1.05 V vs RHE. Notably, the newly formed silver nanoparticles emerged as the active sites responsible for this high CO selectivity rather than the molecular system. Intriguingly, the introduction of copper ions into the restructured Ag-nanoparticle-decorated carbon altered the product selectivity. At -1.1 V vs RHE in 0.1 M KCl, we achieved a high C2 selectivity of 75%. Furthermore, not only the Ag-Cu bimetallic nanoparticle but also the small-sized Ag-Cu nanocluster decorated over GMC was proposed as active sites during catalytic reactions. Our straightforward approach offers valuable insights for fine-tuning the product selectivity of immobilized molecular systems, extending beyond C1 products.

Silver Organometallics that are Highly Potent Thioredoxin and Glutathione Reductase Inhibitors: Exploring the Correlations of Solution Chemistry with the Strong Antibacterial Effects.

The antibacterial activity of silver species is well-established; however, their mechanism of action has not been adequately explored. Furthermore, issues of low-molecular silver compounds with cytotoxicity, stability, and solubility hamper their progress to drug leads. We have investigated silver N-heterocyclic carbene (NHC) halido complexes [(NHC)AgX, X = Cl, Br, and I] as a promising new type of antibacterial silver organometallics. Spectroscopic studies and conductometry established a higher stability for the complexes with iodide ligands, and nephelometry indicated that the complexes could be administered in solutions with physiological chloride levels. The complexes showed a broad spectrum of strong activity against pathogenic Gram-negative bacteria. However, there was no significant activity against Gram-positive strains. Further studies clarified that tryptone and yeast extract, as components of the culture media, were responsible for this lack of activity. The reduction of biofilm formation and a strong inhibition of both glutathione and thioredoxin reductases with IC50 values in the nanomolar range were confirmed for selected compounds. In addition to their improved physicochemical properties, the compounds with iodide ligands did not display cytotoxic effects, unlike the other silver complexes. In summary, silver NHC complexes with iodide secondary ligands represent a useful scaffold for nontoxic silver organometallics with improved physicochemical properties and a distinct mechanism of action that is based on inhibition of thioredoxin and glutathione reductases.

A promising perspective through potential antimicrobial, anti‐cancer, and antiviral activity against SARS‐CoV‐2 of silver(I) complexes: Synthesis, characterization, density functional theory calculations, and in‐silico molecular docking studies

This study tends to accomplish the sustainable development goal, which calls for all healthy lives. Antibiotic resistance, cancer, and severe acute respiratory syndrome coronavirus all showed high death rates in recent years. Our approach is to make better medications available to fight these feared health issues. In this context, three silver(I) complexes (1–3) based on the antibiotic gemifloxacin (HGMF) were synthesized and thoroughly examined using analytical, spectral, and thermal methods. The density functional theory suggested that complex 1 has a bent coordination environment while 2 and 3 have a distorted trigonal planar geometry. The optimal donor and acceptor centers were determined by the natural‐bond orbital analysis. Interaction of complexes with calf‐thymus DNA has been investigated and their binding constants were ordered as 3 > 2 > 1. The antimicrobial activity against 10 pathogenic microorganisms demonstrated that complex 3 exhibited superior activity compared with standard antibiotics. Testing against mammalian cell lines, liver carcinoma, breast carcinoma, and colon carcinoma revealed that complex 3 showed remarkable cell growth inhibition activity with IC50 values ranging from 3.0 to 9.3 μg/mL. Studies of Molecular docking against SARS‐CoV‐2 main protease Mpro (ID: 6 WTT) proved a powerful type of interaction at the active site. Complex 3 exhibits a potent inhibition effect with a total binding energy of −12.58 kcal/mol compared with the reference ligand inhibitor K36 suggesting its ability to block viral protease. This study presents promising bioactive candidates that have a practical impact on various medicinal fields.