Quinoline Functionalized Schiff Base Silver (I) Complexes: Interactions with Biomolecules and In Vitro Cytotoxicity, Antioxidant and Antimicrobial Activities

A fluorescent chemosensor for selective detection of chromium (III) ions in environmentally and biologically relevant samples

A simple single step one pot multicomponent reaction was performed to synthesize N-(tert-butyl)-2-(furan-2-yl)imidazo[1,2-a]pyridine-3-amine (TBFIPA). The synthesized TBFIPA was subjected to library of cations to study its ability for selective and sensitive detection of specific metal ions. Selective detection of chromium ions by TBFIPA were found from the significant hypsochromic shift (335 nm → 285 nm) in the UV-Visible spectra. The fluorescent TBFIPA displays complete quenching of fluorescence under UV lamp (365 nm) only in the presence of chromium without the interference of common metal ions. Binding constant (ka) obtained from Benesi-Hildebrand plot is 0.21 × 105 M-1, limit of detection (LOD) and limit of quantification (LOQ) of TBFIPA toward Cr3+ ions are 4.70 × 10-7 M and 1.56 × 10-7 M, respectively. The mechanism proposed during complex formation were supported by stoichiometric Job continuous variation plot, 1H NMR titration and ESI-MS spectroscopic data. All the experimental confirmation for complex formation were corroborated with theoretical DFT studies optimized using RB3LYP/6-31G(d) basis set. The selectivity and sensitivity of TBFIPA toward Cr3+ ions are found suitable to design a user-friendly silica based portable test kit. Alongside, TBFIPA was successfully utilized for imaging onion epidermal cells. Furthermore, the results obtained for biological, environmental, and industrial samples provided solid evidence to estimate chromium ions using TBFIPA in these real samples.

Homo- and heterometallic complexes of Zn(II), {Zn(II)Au(I)}, and {Zn(II)Ag(I)} with pentadentate Schiff base ligands as promising anticancer agents

Two families of homo- and heterometallic complexes, [Zn2L1(μ-OH)(H2O)2](ClO4)2, [Zn2L2(μ-OH)(H2O)2](ClO4)2, [Zn2L3(μ-OH)(H2O)2](ClO4)2, 1∞[{L1Zn2(μ-OH)}{μ-[Ag(CN)2]}](ClO4), [{L1Zn2(μ-OH)}2{μ-[Au(CN)2]}{[Au(CN)2]2}](ClO4)·H2O, 1∞[{L2Zn2(μ3-OH)}2(H2O){μ-[Ag(CN)2]}](ClO4)3·THF·0.5MeOH, 1∞[{L2Zn2(μ3-OH)}2(H2O){μ-[Au(CN)2]}](ClO4)3·THF·H2O, and 1∞[{L3Zn2(μ-OH)}{μ-[Ag(CN)2]}][Ag(CN)2]·H2O, respectively, have been synthesized and characterized. The Schiff bases used as ligands were obtained by condensation reactions of 2,6-diformyl-p-cresol with N,N-dimethyl-ethylenediamine (HL1), 2-aminomethyl-pyridine (HL2), and 2-aminoethyl-pyridine (HL3), respectively. The cytotoxic/cytostatic and genotoxic effects in cultured human MCF-7 (luminal type A breast cancer), MDA-MB-231 (triple negative breast cancer), HeLa (cervical carcinoma), and Lep-3 (non-tumor embryonal fibroblastoid cells) were studied. The investigations were performed by thiazolyl blue tetrazolium bromide test (MTT test), neutral red uptake cytotoxicity assay, crystal violet staining, hematoxylin and eosin staining, double staining with acridine orange and propidium iodide, AnnexinV/FITC, and Comet assay in short-term experiments (24-72 h, with monolayer cell cultures) as well as by 3D colony-forming method in long-term experiments (28 days, with 3D cancer cell colonies). The results obtained revealed that: (i) applied at a concentration range of 0.1-100 μg mL-1, the compounds investigated decrease in a time- and concentration-dependent manner the viability and/or proliferation of the treated cells; (ii) complexes of {Zn(II)Au(I)} show relatively higher cytotoxic/genotoxic activity and antitumor potential as compared to {Zn(II)Ag(I)}; (iii) some of the complexes demonstrate more pronounced cytotoxic potential than commercially available antitumor agents cisplatin, oxaliplatin, and epirubicin.

The link between relative stability constant of DNA- and BSA-chromenopyrimidine complexes and cytotoxicity towards human breast cancer cells (MCF-7)

In this study, we synthesized and characterized ten chromenopyrimidine derivatives using analytical and spectroscopic methods. Studies on DNA and albumin binding affinity, as well as cytotoxicity tests on human breast cancer (MCF-7) cells, of the chromenopyrimidines, were conducted. The natural logarithm of the relative stability constant of DNA- and BSA-chromenopyrimidine complexes [ln(K_DNA/K_BSA)] was used as a criterion for selecting compounds for cytotoxicity studies. We found that ln(K_DNA/K_BSA) was inversely related to IC₅₀ values of the compounds in MCF-7 cells. The antiproliferative effects of the compounds were found to induce apoptosis in MCF-7 cells, which is a desired mechanism of cell death. Correlations between the DNA and albumin binding affinities of chromenopyrimidines were established. We propose that this relationship approach can, for a given set of compounds, assist in predicting the cytotoxicity of potential drug candidates towards MCF-7 cells based on their experimentally determined CT-DNA and BSA binding affinities.

Synthesis, characterization, and nonlinear optical properties of copper (II) ligand Schiff base complexes derived from 3-Nitrobenzohydrazide and benzyl

A new series of Cu (II) complexes were prepared using Schiff base ligand of N-N'-(1,2-diphenyl ethane-1,2-diylidene)bis(3-Nitrobenzohydrazide). The prepared ligand and Cu (II) complex were characterized using various physicochemical investigations such as X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), and Energy dispersive X-ray analysis (EDX), Fourier Transform Infrared (FT-IR), [Formula: see text] Nuclear Magnetic Resonance (NMR), [Formula: see text] NMR, Diffuse Reflectance Spectroscopy (DRS), Vibrating Sample Magnetometer (VSM), and Z-Scan technique (Nonlinear optical (NLO) properties). In addition, the prepared samples have been examined for their NLO characteristics with the help of the Density Functional Theory calculations which proved that the Cu (II) Complex is more polarized than Ligand. According to XRD and FESEM results, the nanocrystalline nature of the samples is confirmed. The metal-oxide bond assigned in the functional studies by FTIR. Magnetic studies demonstrate weak ferromagnetic and paramagnetic nature for Cu (II) complex and diamagnetic nature for the ligand, respectively. DRS spectrum exhibited higher reflectance for Cu (II) than the ligand. The band gap energies of the synthesized samples were estimated by employing the Tauc relation and Kubelka-Munk theory on reflectance data and found to be 2.89 eV and 2.67 eV for Cu (II) complex and ligand, respectively. Extinction coefficient and refractive index values were calculated using the Kramers-Kronig method. The z-scan technique was applied to estimate the NLO properties by a 532 nm Nd:YAG laser.

Multifunctional O-phenanthroline silver(I) complexes for antitumor activity against colorectal adenocarcinoma cells and antimicrobial properties by multiple mechanisms

A series of O-phenanthroline silver(I) complexes were synthesized and characterized by infrared (IR) spectroscopy, mass spectrometry (MS), ¹H nuclear magnetic resonance (NMR) spectroscopy and single-crystal X-ray crystallography. The cytotoxicity of the silver(I) complex (P-131) was evaluated in the cancer cell lines HCT-116, HeLa, and MDA-MB-231 and the normal cell line LO2 via MTT assays. The 50% inhibition concentration (IC₅₀) of P-131 on HCT116 cell line is 0.86 ± 0.03 μM. It is far lower than the IC₅₀ value of cisplatin (9.08 ± 1.10 μM), the IC₅₀ value of normal cell LO2 (76.20 ± 0.48 μM) is much higher than that of cisplatin (3.99 ± 0.74 μM), indicating that its anticancer effect is stronger than that of cisplatin, and its biological safety is greater than that of cisplatin. Furthermore, anticancer mechanistic studies showed that P-131 inhibited cell proliferation by blocking DNA synthesis and acted temporally on the nucleus in dividing HCT-116 cells. Moreover, P-131 increased intracellular reactive oxygen species (ROS) levels in a dose-dependent manner. Notably, 10 mg/kg P-131 showed better antitumor effects than oxaliplatin in an HCT116 human colorectal xenograft mouse model without inducing toxicity. Moreover, the microdilution broth method was used to evaluate the antimicrobial properties of P-131 against Pseudomonas aeruginosa and Candida albicans. A biofilm eradication study was also performed using the crystal violet method and confocal laser scanning microscopy.

Versatile applications of transition metal incorporating quinoline Schiff base metal complexes: An overview

Since the last decade, research on quinoline Schiff base metal complexes has risen substantially due to their versatile applications across many significant fields. Schiff bases are also known as azomethines, aldimines, and imines. Quinoline Schiff base-derived metal complexes are intriguing to study topics. These complexes are employed in biological, analytical, and catalytic fields. Researchers have found that Schiff bases are more biologically active when coordinated with metal ions. Research in the biological sciences has shown that heterocyclic compounds like quinoline and its derivatives are important. Because of their broad spectrum of activity, quinoline derivatives have been discovered to be effective therapeutic agents for various disorders. Even though various classical synthetic pathways mentioned in the literature are still in use, there is an urgent need for a new, more effective method that is safer for the environment, has a higher yield, generates less hazardous waste, and is easier to use. This highlights the critical need for a safe, eco-friendly approach to quinoline scaffold synthesis. This review focuses exclusively on Schiff base metal complexes derived from quinoline, fabricated and studied in the past ten years, and having anticancer, antibacterial, antifungal, antioxidant, antidiabetic, antiproliferative, DNA-intercalation, and cytotoxic activities.

Recent insights into antibacterial potential of benzothiazole derivatives

Antimicrobial resistance (AMR) is a worldwide concern among infectious diseases due to increased mortality, morbidity and treatment cost. According to WHO 2019 report, among the 32 antibiotics in the clinical trials, only six were classified as innovative and containing novel moiety. The remaining antibiotics from this list contain previously known moiety (WHO AMR 2019). Therefore, the development of novel antibiotics to control resistance problems is crucial. Benzothiazole derivatives are of great interest due to their wide range of biological activities and medicinal applications. Reported data indicated that benzothiazole derivatives displayed antibacterial activity by inhibiting the dihydroorotase, DNA gyrase, uridine diphosphate-n-acetyl enol pyruvyl glucosamine reductase (MurB), peptide deformylase, aldose reductase, casdihydrofolate reductase, enoyl acyl carrier protein reductase, dialkylglycine decarboxylase, dehydrosqualene synthase, dihydropteroate synthase and tyrosine kinase. The present review analyzed the synthesis, structure-activity relationship (SAR) and mechanism of action studies of benzothiazole derivatives as antibacterial agents reported by various research groups in the last five years (2018-2022). Different patents on the antimicrobial activity of benzothiazole derivatives have also been summarized. The finding of the present review will be beneficial for the researchers in the development of novel antibacterial molecules based on benzothiazole moiety.

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Recent developments in antimalarial activities of 4-aminoquinoline derivatives

Malaria is the fifth most lethal parasitic infection in the world. Antimalarial medications have played a crucial role in preventing and eradicating malaria. Numerous heterocyclic moieties have been incorporated into the creation of effective antimalarial drugs. The 4-aminoquinoline moiety is favoured in antimalarial drug discovery due to the diverse biological applications of its derivative. Since the 1960s, 4-aminoquinoline has been an important antimalarial drug due to its low toxicity, high tolerability, and rapid absorption after administration. This review focused on the antimalarial efficacy of the 4-aminoquinoline moiety hybridised with various heterocyclic scaffolds developed by scientists since 2018 against diverse Plasmodium clones. It could aid in the future development of more effective antimalarial agents.

Quinoline Hydrazide/Hydrazone Derivatives: Recent Insights on Antibacterial Activity and Mechanism of Action

Antibiotics are becoming gradually ineffective due to drug resistance, leading to greater difficulty in the treatment of infectious diseases. Therefore, the development of new chemical entities with different mechanisms of action is essential in the fight against resistant microorganisms. Various studies have shown that quinoline hydrazide/hydrazone derivatives possess several biological activities, such as antimalarial, antitubercular, anticancer, anti-inflammatory, and antimicrobial. Among these activities, the antibacterial activity of quinoline hydrazide/hydrazone derivatives is noteworthy. The synthetic flexibility of the quinoline ring has led to the development of a wide range of structurally diverse quinoline hydrazide/hydrazone derivatives, which can act at various bacterial targets such as DNA gyrase, glucosamine-6-phosphate synthase, enoyl ACP reductase, and 3-ketoacyl ACP reductase. This review emphasizes the antibacterial potential of various reported quinoline hydrazide/hydrazone derivatives based on substitution in the quinoline ring. The antibacterial activity of various metal-quinoline hydrazide/hydrazone complexes is also discussed. The aim of this review is to assemble and scrutinize the latest reports in this promising area of drug development.

New N4-Donor Ligands as Supramolecular Guests for DNA and RNA: Synthesis, Structural Characterization, In Silico, Spectrophotometric and Antimicrobial Studies

The present work reports the synthesis of new N4-donor compounds carrying p-xylyl spacers in their structure. Different Schiff base aliphatic N-donors were obtained synthetically and subsequently evaluated for their ability to interact with two models of nucleic acids: calf-thymus DNA (CT-DNA) and the RNA from yeast Saccharomyces cerevisiae (herein simply indicated as RNA). In more detail, by condensing p-xylylenediamine and a series of aldehydes, we obtained the following Schiff base ligands: 2-thiazolecarboxaldehyde (L1), pyridine-2-carboxaldehyde (L2), 5-methylisoxazole-3-carboxaldehyde (L3), 1-methyl-2-imidazolecarboxaldehyde (L4), and quinoline-2-carboxaldehyde (L5). The structural characterisation of the ligands L1-L5 (X-ray, ¹H NMR, ¹³C NMR, elemental analysis) and of the coordination polymers {[CuL1]PF₆}_n (herein referred to as Polymer1) and {[AgL1]BF₄}_n, (herein referred to as Polymer2, X-ray, ¹H NMR, ESI-MS) is herein described in detail. The single crystal X-ray structures of complexes Polymer1 and Polymer2 were also investigated, leading to the description of one-dimensional coordination polymers. The spectroscopic and in silico evaluation of the most promising compounds as DNA and RNA binders, as well as the study of the influence of the 1D supramolecular polymers Polymer1 and Polymer2 on the proliferation of Escherichia coli bacteria, were performed in view of their nucleic acid-modulating and antimicrobial applications. Spectroscopic measurements (UV-Vis) combined with molecular docking calculations suggest that the thiazolecarboxaldehyde derivative L1 is able to bind CT-DNA with a mechanism different from intercalation involving the thiazole ring in the molecular recognition and shows a binding affinity with DNA higher than RNA. Finally, Polymer2 was shown to slow down the proliferation of bacteria much more effectively than the free Ag(I) salt.

Silver(I) pyridinyl complexes with benzothiazole, thiophene, and furan moieties: DNA/protein-binding, antibacterial, antioxidant, and anticancer studies

We have synthesized and characterized nine Ag(I) complexes of Schiff bases containing thiophene, furan, and pyridine moieties for in vitro antibacterial, antioxidant, anticancer activities, and DNA/bovine serum albumin (BSA) binding studies. Based on the analytical and spectral analyses, a linear geometry was proposed for all the Ag(I) complexes, except for one (with the furan moiety), which formed a distorted T-shaped geometry. UV-vis absorption studies on the interactions of calf thymus-DNA (CT-DNA) with the nine Ag(I) complexes pointed to an intercalative binding mode. With a binding constant K_b of 3.75 × 10⁵ M^-1 , the complex bearing a benzothiazole moiety (1) interacted stronger with CT-DNA than the rest of the complexes. Fluorescence spectroscopic data revealed that the complexes had a modest binding affinity for BSA through static quenching. The complexes displayed good antioxidant properties, especially those with a benzothiazole moiety. Notable antibacterial activities against methicillin-resistant Staphylococcus aureus, Staphylococcus aureus, Salmonella typhimurium, Pseudomonas aeruginosa, Escherichia coli, and Klebsiella pneumoniae were observed for complexes with the furan and thiophene moieties. The in vitro anticancer studies of selected complexes against three cancer cell lines showed that the complexes were more effective against the inhibition of the growth of cervical cancer cells relative to cisplatin.

A study of structure-activity relationship and anion-controlled quinolinyl Ag(I) complexes as antimicrobial and antioxidant agents as well as their interaction with macromolecules

In this communication, we feature the synthesis and in-depth characterization of a series of silver(I) complexes obtained from the complexation of quinolin-4-yl Schiff base ligands ((E)-2-((quinolin-4-ylmethylene)amino)phenol L_a, 2-(quinolin-4-yl)benzo[d]thiazole L_b, (E)-N-(2-fluorophenyl)-1-(quinolin-4-yl)methanimine L_c, (E)-N-(4-chlorophenyl)-1-(quinolin-4-yl)methanimine L_d, (E)-1-(quinolin-4-yl)-N-(p-tolyl)methanimine L_e, (E)-1-(quinolin-4-yl)-N-(thiophen-2-ylmethyl)methanimine L_f) and three different silver(I) anions (nitrate, perchlorate and triflate). Structurally, the complexes adopted different coordination geometries, which included distorted linear or distorted tetrahedral geometry. The complexes were evaluated in vitro for their potential antibacterial and antioxidant activities. In addition, their interactions with calf thymus-DNA (CT-DNA) and bovine serum albumin (BSA) were evaluated. All the complexes had a wide spectrum of effective antibacterial activity against gram-positive and gram-negative bacterial and good antioxidant properties. The interactions of the complexes with CT-DNA and BSA were observed to occur either through intercalation or through a minor groove binder, while the interaction of the complexes with BSA reveals that some of the complexes can strongly quench the fluorescence of BSA through the static mechanism. The molecular docking studies of the complexes were also done to further elucidate the modes of interaction with CT-DNA and BSA.

Different Schiff Bases-Structure, Importance and Classification

Schiff bases are a vast group of compounds characterized by the presence of a double bond linking carbon and nitrogen atoms, the versatility of which is generated in the many ways to combine a variety of alkyl or aryl substituents. Compounds of this type are both found in nature and synthesized in the laboratory. For years, Schiff bases have been greatly inspiring to many chemists and biochemists. In this article, we attempt to present a new take on this group of compounds, underlining of the importance of various types of Schiff bases. Among the different types of compounds that can be classified as Schiff bases, we chose hydrazides, dihydrazides, hydrazones and mixed derivatives such as hydrazide-hydrazones. For these compounds, we presented the elements of their structure that allow them to be classified as Schiff bases. While hydrazones are typical examples of Schiff bases, including hydrazides among them may be surprising for some. In their case, this is possible due to the amide-iminol tautomerism. The carbon-nitrogen double bond present in the iminol tautomer is a typical element found in Schiff bases. In addition to the characteristics of the structure of these selected derivatives, and sometimes their classification, we presented selected literature items which, in our opinion, represent their importance in various fields well.

The effect of structural configuration on the DNA binding and in vitro antioxidant properties of new copper(ii) N2O2 Schiff base complexes

DNA interaction with cis and trans-copper NO complexes favours the cis configuration due to low energies observed in the cis configuration.

Schiff bases and their metal complexes with biologically compatible metal ions; biological importance, recent trends and future hopes

Schiff bases are in the field of medicinal and material chemistry for a long time. There are several advancements from time to time towards facile synthesis and potential applications. As medicines they have been applied as organic molecules as well as their metal complexes. The activities of metal complexes have been found to increase due to increase lipophilicity in comparison to the corresponding free ligand. Besides simple coordination compounds they have been applied as ionic liquid (IL)- supported and IL-tagged species with far enhanced efficiency. Among metal complexes recent advancement deals with photodynamic therapy to treat a number of tumors with fewer side effects. Schiff bases are efficient ligands and their complexes with almost all metal ions are reported. This mini-review article deals with complexes of Schiff bases with biologically compatible metal ions, Co(II), Cu(II), Zn(II), Pd(II), Ag(I), Pt(II) and their potential uses to combat cancerous cells. Strong hopes are associated with photodynamic therapy and IL-tagged and IL-supported Schiff bases and their complexes.

Synthesis and potential antimicrobial activity of novel α-aminophosphonates derivatives bearing substituted quinoline or quinolone and thiazole moieties

To develop novel antimicrobial agents, and based on the biologically active heterocyclic quinoline and thiazole substituted, a series of novel α-aminophosphonates (9a–h) and (10i–l) derivatives that incorporated quinoline or quinolone, and coumarylthiazole or 5-phenylthiazol-2-amine moieties were designed and synthesized via Kabachnik–Fields reaction in the presence of ionic liquid under ultrasound irradiation. All the new compounds were obtained in good yield with a simple workup and were confirmed using various spectroscopic methods. The in vitro antimicrobial activity of all synthesized compounds were screened in terms of MIC values against the selected strains of Gram-negative and Gram-positive bacteria and two fungal strains using the broth micro-dilution method. The results showed that most of the tested compounds showed moderate inhibitory activities against both Gram‐positive and ‐negative bacteria compared with reference drugs. The following compounds 9e, 9g, 9h, 9i and 9f, 9g, 9h, 10k, 10l are the most active against Gram-positive and Gram-negative bacteria strains, respectively, with MIC values ranging between 0.25 and 128 μg/mL. The synthesized compounds 9b, 9c, 9f, 9g, 9h, 10k, and 10l exhibited excellent antifungal inhibition with MIC values ranging between 0.25 and 32 μg/mL. Structure–activity relationship revealed that the presence of coumarylthiazole moiety and hydroxyl in the quinoline group increased the inhibitory activity against microbial strains pathogens. These results confirm that the synthesized compounds can be potential antimicrobial drugs candidate.

Synthesis and Spectroscopic Investigations of Schiff Base Ligand and Its Bimetallic Ag(I) Complex as DNA and BSA Binders

Generation of well-defined potential metallotherapeutics for cancer treatment, one of the most population-threatening diseases, is challenging and an active area of modern research in view of their unique properties and thus multiple possible pathways of action in cells. Specifically, Schiff base ligands were recognized as very promising building blocks for the construction of stable and active complexes of numerous geometries and topologies. Incorporation of Ag(I) ions allows for the formation of flat complexes with potential unoccupied coordination sites, thus giving rise to specific interactions between the metallotherapeutic and biomolecule of interest. Herein, we present the design, synthesis and characterization of new Schiff base ligand L and its Ag(I) bimetallic complex [Ag2L2]2+ with two planar moieties formed around the metal ions and connected through cyclohexane rings, confirmed by X-ray measurements. The compounds were described in context of their potential use as anticancer drugs through DNA and BSA binding pathways by several spectroscopic methods (CD, UV-Vis, fluorescence). We revealed that both, L and [Ag2L2]2+, interact with similar affinity with CT-DNA (Kb~106 M-1), while they differ in the type and strength of interactions with the model albumin-BSA. [Ag2L2]2+ binds BSA in both a dynamic and static manner with the Ksv = 8.8 × 104 M-1 in the Trp-134 and Trp-213 sites, whereas L interacts with BSA only dynamically (KSV = 2.4 × 104 M-1). This found further confirmation in the CD studies which revealed a reduction in α-helix content in the albumin of 16% in presence of [Ag2L2]2+.

Synthesis of new 7-amino-3,4-dihydroquinolin-2(1H)-one-peptide derivatives and their carbonic anhydrase enzyme inhibition, antioxidant, and cytotoxic activities

Six new monopeptides, seven new dipeptides, and two deprotected monopeptide dihydroquinolinone conjugates were prepared by the benzothiazole-mediated method and their structures were confirmed by nuclear magnetic resonance, mass, infrared spectroscopy, and elemental analysis methods. The human carbonic anhydrase (hCA) I and hCA II enzyme inhibition activities of the compounds were determined using the stopped-flow instrument. The synthesized peptide-dihydroquinolinone conjugates 2, 3, 6, 10, 13, and 15 showed inhibition against the hCA II enzyme in the range of 15.7-65.7 µM. However, none of the compounds showed inhibition of hCA I at a concentration of 100 µM. The antioxidant activities of the compounds were also examined using the DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging method at concentrations of 12.5-125 µg/ml, but when compared with the standard antioxidant compounds α-tocopherol and butylated hydroxyanisole (BHA), weak antioxidant activities were detected. The cytotoxic effects of four compounds against the A549 and BEAS-2B cell lines were also investigated. Among the compounds studied, compound 7 was found to be most effective, with the IC₅₀ values on the A549 cells for 48 and 72 h being 26.87 and 9.979 µg/ml, respectively, and the IC₅₀ values on the BEAS-2B cells being >100 µg/ml. None of the tested compounds showed antimicrobial activity in the concentration range (800-1.56 µg/ml) studied.

Ag(I) Complexes of Imine Derivatives of Unexpected 2-Thiophenemethylamine Homo-Coupling and Bis-(E)-N-(furan-2-ylmethyl)-1-(quinolin-2-yl)methanimine

Imines are fundamental organic compounds used as synthetic intermediates and as ligands in coordination chemistry. They are also found to be important pharmacophores in various bioactive compounds. In this report, two Schiff bases were prepared using the traditional condensation of 4-pyridinecarboxaldehyde with 2-thiophenemethylamine and 2-quinolinecarboxaldehyde with furfurylamine to form (E)-1-(pyridin-4-yl)-N-(thiophen-2-ylmethyl)methanimine (L1) and (E)-N-(furan-2-ylmethyl)-1-(quinolin-2-yl)methanimine (L2) respectively. L1 and L2 were complexed with silver perchlorate in 2:1 [M:L] stoichiometry to obtain complexes 1 and 2, respectively. The crystal structures of 1 and 2 were unequivocally determined by single-crystal X-ray diffraction analysis. The resulting structures revealed 2 to be a four-coordinate as expected. In contrast, an unexpected chemoselective hydrolytic cleavage of one mole of the (CH=N) imine ligands occurred in complex 2 and, further, the amines (thiophenemethylamine) homo-coupled to form a new imine ligand derivative in situ (L1a) before coordinating to the Ag(I) center along with L1. This observation described an alternative synthetic route to be explored to synthesize a diverse range of imine derivatives, which involves the Ag(I)-promoted homo-coupling of amines. Herein, the crystal structures of Ag(I) complexes of pyridinyl [Ag(L1)(L1a)]ClO4 (1) and quinolinyl [Ag(L2)2]ClO4 (2) Schiff bases are presented.

Evaluation of substituent bioactivity and anion impact of linear and T-shaped silver(i) pyridinyl complexes as potential antiproliferative, antioxidant, antimicrobial agents and DNA- and BSA-binders

The impact of ligand substituents and anion variation on the bio-activity of pyridinyl Ag(I) complexes was evaluated. The complexes showed potential therapeutic ability with notable anticancer, antioxidant, and antimicrobial activities.