Search Results (244)

Understanding how redox-active ligands coordinate to metal centers of different oxidation states is essential for applications ranging from metal remediation and recycling to drug discovery. In this study, coordination complexes of nickel(II), copper(II), and zinc(II) chloride salts were synthesized by mixing the salts with either arylazoformamide (AAF) or arylazothioformamide (ATF) ligands in toluene or methanol. The AAF and ATF ligands coordinate through their 1,3-heterodienes, N=N–C=O and N=N–C=S, respectively, and, due to their known strong binding, the piperidine and pyrrolidine formamide units were selected, as was the electron-donating methoxy group on the aryl ring. A total of 12 complexes were obtained, representing potential chelation events from ligand-driven oxidation of zerovalent metals and/or coordination of oxidized metal salts. The X-ray crystallography revealed a range of coordination patterns. Notably, the Cu(II)Cl₂ complexes, in the presence of ATF, produce [ATF-CuCl]₂ dimers, supporting a potential reduction event at the copper, while other metals with ATF and all metals with AAF remain in the 2+ oxidation state. Hirshfeld analysis was performed on all complexes, and it was found that most interactions across the complexes were dominated by H…H, followed by Cl…H/H…Cl, with metals showing very little to no interaction with other atoms. Spectroscopic techniques such as UV–VIS absorption, NMR (when diamagnetic), and FTIR, in addition to electrochemical studies support the metal–ligand coordination. Full article

This study investigates the corrosion inhibition efficiency of [2-(thiophen-2-yl)-1-(thiophen-2-ylmethyl)-1H-benzo[d]imidazole] and its Zn and Cu complexes for mild steel in 1.0 M HCl. The ligand was selected for its non-toxic profile and high electron density, favoring strong adsorption onto the metal surface. Electrochemical methods, including EIS, PDP, LPR, and CASP, were employed to evaluate the inhibitors’ performance. The results showed a significant decrease in corrosion current density and increased polarization resistance, with the Zn complex achieving the highest inhibition efficiency (93.8%). EIS fitting confirmed the formation of a protective film with high charge transfer and film resistance. Surface analyses by SEM and EDS revealed smoother steel morphology and inhibitor adsorption. XPS confirmed the presence of Fe³⁺, Zn²⁺and Cu²⁺ oxides, as well as all active inhibitor elements on the surface, supporting a mixed inhibition mechanism. The enhanced performance of the metal complexes is attributed to synergistic effects between the metal ions and the heterocyclic ligand, offering a promising strategy for the design of effective and environmentally friendly corrosion inhibitors. Full article

Three new complexes of Hg(II), with the general formulas [Hg₂(ox)₂(NA)₄]_n·3nH₂O (1), [Hg(NO₃)₂(NA)₂(H₂O)₂]·2NA (2), and [Hg₂(SO₄)₂(H₂O)₂(NA)₄]·6H₂O (3), where ox = oxalate and NA = nicotinamide, were synthesized and characterized by single crystal X-ray diffraction, elemental analysis, FT-IR, and fluorescence spectra. For complex (2), ¹³C and ¹H NMR spectra were recorded. Thermogravimetric analysis was also performed for complexes (1) and (2). Single crystal X-ray diffraction shows that in the polymeric complex (1) and the binuclear complex (3), the Hg(II) ions are hexacoordinated, whereas in the mononuclear complex (2), Hg(II) is octacoordinated. In complex (1), each oxalate group acts in a µ₄ coordination manner, the basal plan being made up by four oxygen atoms belonging to the two oxalate ligands, while the nicotinamide molecules occupy the axial positions. In complex (2), the nitrate groups coordinate in a bidentate chelating mode, whereas in complex (3), each sulphate ligand acts in a bidentate chelating–bis monodentate bridging manner. Full article

We report the mode of interaction of copper(II) ions with tyrosine (Tyr, L) in binary and ternary systems with Ado, AMP, ADP, and ATP (L’) as second ligands in an aqueous solution. The composition and overall stability constants of the complexes formed were determined using the potentiometric method. The coordination sites were identified through spectroscopic (VIS, EPR, IR) methods, as well as DFT and computational–molecular modeling. In the binary Cu(II)/Tyr system, the main reaction centers of the ligand molecule involved in the interactions with copper(II) ions are nitrogen (-NH₂ group), as well as oxygen atoms (-COO⁻ group), as confirmed, for example, by comparing the mode of coordination in the CuH₂(Tyr)₂ species and the [CuH₂(Tyr)₂(H₂O)] × 1.5H₂O solid complex obtained. In the ternary Cu(II)/L/L’ systems, MLHxL’ and mixed MLL’ protonated complexes are formed. Only in the ATP system were no MLL’(OH)_x hydroxocomplexes found. An increase in the number of phosphate groups in ADP and ATP molecules has no effect on their participation in the coordination in ternary species, and these ligands interact just like in binary species (i.e., in ADP, both α- and β-phosphate groups, and in ATP, only the γ-phosphate group). It was observed that the introduction of a second ligand into the Cu(II)/Tyr system did not change, over the entire pH range studied, the tyrosine coordination mode. Full article

Cyclen-based ligands are among the most preferred ones in radiopharmacy, where they are mainly applied for transferring radioisotopes through the human body. A crucial criterion is the stability of their metal–ligand complexes, which depends on the stabilization of the free ligand in solution. However, these flexible ligands can have numerous conformations, and for a reliable evaluation of the dissociation energy, the most stable one(s) in solution must be known. In the present study, the low-energy conformational space of four anionic (2-) cyclen-based ligands has been elucidated in aqueous solution by a joint molecular mechanics (MM)/Density Functional Theory (DFT) procedure. The results revealed a significant preference for C₂ symmetric structures, more or less resembling the arrangements in their metal complexes. The computed dissociation energies agree with the experimentally found stability trend for the Pb²⁺ complexes with ligands containing picolinate pendant arms. For complexes with mixed donor groups (carboxyl, amide, pyridine), significant thermodynamic stabilities were predicted. Full article

Adhesion of cell membranes is relevant to many biological processes and arises from the specific binding of membrane-anchored receptor proteins to their ligands present in the apposing membrane. Here, we employ a statistical–mechanical model and perform Monte Carlo simulations to study a system of adhered membranes in which the receptor and ligand proteins exhibit affinity for association with so-called lipid rafts, which are fluctuating nanoscale molecular clusters enriched in sphingolipid and cholesterol. We focus on equilibrium properties of the adhered membranes in the mixed phase, where both the membrane-anchored proteins and lipid rafts are distributed more-or-less uniformly within the membranes. Our simulation results show that lateral attraction between lipid rafts enhances the receptor–ligand binding, affecting the adhesion of the membranes. On the other hand, the receptor–ligand binding causes lipid rafts to be distributed less uniformly within the membranes and, simultaneously, leads to an increased co-localization of the membrane-anchored proteins with lipid rafts. We quantify and discuss all these effects, providing a detailed picture of the complex interplay between the adhesion of the membranes and the lateral distribution of the membrane-anchored proteins and lipid rafts. Our results broaden the understanding of the physical mechanisms that determine the supra-molecular organization of lipid rafts and membrane receptors in cell membranes. This understanding may help to elucidate how lipid rafts function in biological processes such as cell signaling and immune responses. Full article

Pyridinecarbonitriles (pyCN), also referred to as cyanopyridines, are promising ligands for the formation of pyridine-based coordination compounds due to their two different N-donor atoms, which enable versatile coordination modes. Copper(II) complexes containing pyCN derivatives are of particular interest for their potential applications in medicinal chemistry and materials science. In this study, the synthesis, structural characterization, and thermal and magnetic properties of three new copper(II) complexes with 3-pyCN, 4-pyCN, and ethyl picolinimidate, obtained in situ by means of alcoholysis of 2-pyCN, are reported: [Cu₂(μ-Ac)₄(3-pyCN)₂] (1), [Cu(H₂O)₂(Etpic)₂]NO₃ (2), and [Cu(NO₃)₂(CH₃CN)(4-pyCN)₂]·CH₃CN (3). Single-crystal X-ray diffraction confirmed that complex 1 features a dinuclear paddle-wheel structure with bridging acetato ligands and monodentate 3-pyCN molecules, coordinated through the ring nitrogen, while complexes 2 and 3 are mononuclear. Thermal analysis showed an intense and highly exothermic decomposition of complex 3, containing nitrate ligands. Magnetic measurements revealed strong antiferromagnetic coupling in the dinuclear complex 1, whereas complexes 2 and 3 displayed paramagnetic behavior with effective magnetic moments ranging from 1.8 μ_B to 2.0 μ_B, consistent with isolated Cu(II) centers. Full article

The aim of this paper is to obtain ethyl (2-(methylcarbamoyl)phenyl)carbamate and its metal complexes as promising antimicrobial agents. The title compound was synthesized using the ring-opening of isatoic anhydride with methylamine and further acylation with ethyl chloroformate. All metal complexes were successfully obtained after mixing the ligand dissolved in DMSO and water solutions of the corresponding metal salts and sodium hydroxide, in a metal-to-ligand-to base ratio 1:2:2. As a result, mixed ligand complexes of ethyl 2-(methylcarbamoyl)phenyl)carbamate and 3-methylquinazoline-2,4(1H,3H)-dione were obtained. The obtained complexes were characterized by their melting points, FTIR, NMR spectroscopy, and MP-AES. Then, the antimicrobial effect of the compounds against both Gram-negative and Gram-positive bacteria, yeasts, and fungi was studied. Only the Co(II) complex showed antimicrobial activity against almost all Gram-positive and Gram-negative bacteria. The cobalt complex exhibited promising antimicrobial activity against Gram-positive Micrococcus luteus with inhibition zones of 20 mm, Listeria monocytogenes (15 mm), Staphylococcus aureus (13 mm), as well as Gram-negative Klebsiella pneumoniae (13 mm) and Proteus vulgaris (13 mm). Given the potential of metal complexes as antimicrobial agents, understanding their cytotoxic effects is crucial for evaluating their therapeutic safety. To assess the in vitro biocompatibility of the experimental compounds, a range of cell viability assays was conducted using human malignant leukemic cell lines (LAMA-84, K-562) and normal murine fibroblast cells (CCL-1). The Ni(II) complex shows IC₅₀ = 105.1 µM against human malignant leukemic cell lines LAMA-84. Based on the reported results, it may be concluded that the mixed cobalt complex of 2-(methylcarbamoyl)phenyl)carbamate and 3-methylquinazoline-2,4(1H,3H)-dione can be attributed as a promising antimicrobial agent. Future in vivo tests will contribute to establishing the antimicrobial properties of this complex. Full article

A novel ruthenium(II) complex, [RuCl₂(η⁶-p-cymene)(bph-κN)] (1), was synthesized and structurally characterized using FTIR and NMR spectroscopy. Density functional theory (DFT) calculations supported the proposed geometry and allowed for comparative analysis of experimental and theoretical spectroscopic data. The interaction of complex 1 with human serum albumin (HSA) and calf thymus DNA was investigated through fluorescence quenching experiments, revealing spontaneous binding driven primarily by hydrophobic interactions. The thermodynamic parameters indicated mixed quenching mechanisms in both protein and DNA systems. Ethidium bromide displacement assays and molecular docking simulations confirmed DNA intercalation as the dominant binding mode, with a Gibbs free binding energy of −34.1 kJ mol⁻¹. Antioxidant activity, assessed by EPR spectroscopy, demonstrated effective scavenging of hydroxyl and ascorbyl radicals. In vitro cytotoxicity assays against A375, MDA-MB-231, MIA PaCa-2, and SW480 cancer cell lines revealed selective activity, with pancreatic and colorectal cells showing the highest sensitivity. QTAIM analysis provided insight into metal–ligand bonding characteristics and intramolecular stabilization. These findings highlight the potential of 1 as a promising candidate for further development as an anticancer agent, particularly against multidrug-resistant tumors. Full article

This study investigates the cytotoxic properties of metal complexes incorporating thio-uracil derivatives, specifically 2,4-dithiouracil and 6-propyl-2-thiouracil. The research focuses on the cytotoxic effects of Cu(II) and Pd(II) complexes with 6-propyl-2-thiouracil, as well as mixed-ligand transition metal Cu(II) and Au(III) complexes of 2,4-dithiouracil with 2-thiouracil and uracil. Cytotoxic activity was assessed against human cervical carcinoma cells (HeLa) and normal kidney cells from the African green monkey. The results demonstrated that incorporating Cu(II) and Au(III) into the compound structures significantly enhanced their cytotoxic effects. Notably, all tested complexes exhibited a stronger inhibitory effect on cancer cell proliferation compared to normal cells, with the palladium(II) complex of 6-propyl-2-thiouracil showing the lowest CD₅₀ value against the tumor cell line (0.00064 mM), which were 149 times lower than that of the ligand (0.0955 mM). These findings suggest that thio-uracil-based metal complexes, particularly those containing palladium (II) and gold(III), hold significant potential for further development as anticancer agents. Full article

This work describes the synthesis, crystal structure, and hydrophobicity tests of four bismuth(III)– and silver(I)–bromide complexes using the triammonium cations diethylenetriaminonium (H₃DETA³⁺) and N,N,N′,N″,N‴-pentamethyldiethylenetriammonium (H₃PMDTA³⁺). The prepared compounds are the 0D perovskites (H₃DETA)[BiBr₆] (1), (H₃DETA)₂[AgBr₄]Br₃ (2), and (H₃PMDTA)[BiBr₆] (3), as well as the 1D/2D mixed perovskite with minimum formula (H₃PMDTA)[Ag₃Br₆] (4), being the last three novel materials. Compounds 1 and 3 crystallize in the orthorhombic P2₁2₁2₁ space group and are discrete [BiBr₆]³⁻ units with the cation surrounding them. In both compounds, the bismuth(III) metal ion is found in a distorted octahedral coordination geometry. Compound 2 crystallizes in the monoclinic P2₁/c space group, and it is a mixed salt consisting of (H₃DETA)[AgBr₄] and (H₃DETA)Br₃, whereas the silver(I) complexes are also isolated. Finally, compound 4, which crystallizes in the orthorhombic space group Pbcn, is a combination of a 2D and 1D silver–bromide perovskite, with the cations filling the voids. The 2D structure has the minimal formula [Ag₄Br₇]³⁻, with the 1D coordination polymer [Ag₂Br₅]³⁻ being both built up by a combination of bromide ions acting as tetrahedra corner and edge-sharing bridging ligands. The silver(I) in 2 and 4 is found in a tetrahedral coordination geometry. All compounds were deposited on pristine FTO glass, resulting in an increase in the contact angle from 22° to 44°, 36°, 62°, and 54° for films of 1, 2, 3, and 4, respectively. Compounds 1 and 3 were also deposited onto Cs₂AgBiBr₆ film, and the contact angles were observed to be the same as when deposited directly onto the FTO cover glass. Full article

Two novel cyclometalated platinum(II) complexes based on 2-phenylpyridine (ppy) and 2,4-difluorophenylpyridine (dfppy) ligands in combination with a benzoylthiourea (4-(decyloxy)-N-((4-(decyloxy)phenyl)carbamothioyl)benzamide, BTU) functionalized with decyloxy alkyl chains as auxiliary ligands were synthesized and characterized for their mechanochromic and photophysical properties. Structural characterization was achieved through IR and NMR spectroscopy, single-crystal X-ray diffraction, and TD-DFT calculations. Both complexes exhibit significant photoluminescence with quantum yields up to 28.3% in a 1% PMMA film. The transitions in solution-phase spectra were assigned to mixed metal-to-ligand (MLCT) and intraligand (ILCT) charge–transfer characteristics. Temperature-dependent studies and thermal analyses confirm reversible phase transitions without mesomorphic behavior despite the presence of the two long alkyl chains. Both complexes displayed reversible mechanochromic and solvatochromic luminescence, with a change in emission color from green to red-orange emissions upon grinding and solvent treatment or heating at 80 °C. Full article

The alarming increase in antimicrobial resistance has intensified the search for novel therapeutic agents capable of combating resistant microbial strains. Copper complexes have emerged as promising antimicrobial agents due to their intrinsic redox activity, ability to disrupt microbial membranes, and interactions with vital biomolecules such as DNA and proteins. This review critically evaluates the antimicrobial potential of copper complexes reported between 2018 and 2025, emphasizing their structural diversity, mechanisms of action, and biological performance against a wide range of bacterial and fungal pathogens. Key findings reveal that Schiff base copper complexes, amino acid derivatives, heterocyclic ligands, and mixed-ligand systems exhibit potent antimicrobial activities, often surpassing standard antibiotics. Mechanistically, copper complexes induce reactive oxygen species (ROS) generation, inhibit enzyme function, cause DNA cleavage, and compromise cell membrane integrity. Furthermore, structure–activity relationship (SAR) analyses indicate that ligand type, coordination geometry, and lipophilicity significantly influence antimicrobial efficacy. Overall, the reviewed studies support the development of copper-based compounds as viable candidates for antimicrobial drug development. This review also identifies current challenges and gaps in knowledge, such as limited in vivo studies and toxicity assessments, which must be addressed to advance these compounds toward clinical application. Full article

Cancer is the second leading cause of death worldwide. Late diagnosis, low drug selectivity, high toxicity, and treatment resistance are challenges associated with pharmacological interventions. The commonly used therapies include surgery, radiotherapy, hormonal therapy, immunotherapy, and chemotherapy. Recently, Cu complexes have been studied owing to their biological functions and effects on tumor angiogenesis. In this review, we examined 23 types of cancer and revealed the use of cell lines. The synthesis of Cu complexes with ligands such as phenanthroline and thiosemicarbazones has also been reported. Such co-ligation is promising because of its high cytotoxicity and selectivity. Compared with cisplatin, Cu complexes, especially mixed complexes, showed better interactions with DNA, generating reactive oxygen species and inducing apoptosis. Nanoformulations have also been adopted to improve the pharmacological activity of compounds. They enhance the efficacy of complexes by targeting them to the tumor tissue, thereby improving their safety. Studies have also explored Cu complexes with clinically relevant pharmacophores, suggesting a “hybrid chemotherapy” against resistant tumors. Overall, Cu complexes have demonstrated therapeutic versatility, antitumor efficacy, and reduced adverse effects, showing great potential as alternatives to conventional chemotherapy and justifying future clinical investigations to validate their use. Full article

This study is dedicated to the design of multiple redox-active oligonuclear manganese complexes supported with a bis(tetradentate) ligand (TPDP = 1,3-bis(bis(2-pyridinylmethyl)amino)-2-propanol) for high-contrast electrochromism based on the reversible redox process between Mn(II) (colorless) and Mn(III) (dark brown). Pentanuclear Mn₅ complex 1 (colorless) was synthesized via a one-pot reaction of Mn²⁺ and TPDP, while tetranuclear Mn₄ complex 2 (brown) was obtained through aerial oxidation of complex 1. Mn₅ complex 1 features a central MnCl₆ unit connected to two Mn₂(μ-TPDP) fragments through μ₃-Cl⁻ and μ-Cl⁻, whereas Mn₄ complex 2 adopts a symmetric tetranuclear structure with two mixed-valence Mn₂^II,III(μ-TPDP)(μ-Cl) fragments that are further linked by μ-oxo. Electrochemical studies revealed multi-step reversible redox properties for both complexes, attributed to Mn^II/Mn^III processes with significant electronic coupling (ΔE_1/2 = 0.27–0.37 V) between Mn centers. Spectroelectrochemical analysis revealed dynamic optical modulation through the tunable d-d transition and ligand-to-metal charge transfer (LMCT) state through reversible multiple redox processes based on Mn(II) ⇆ Mn(III) interconversion. The fabricated electrochromic device (ECD) exhibited reversible and high optical contrast between the colored state (dark brown) and the bleaching state (colorless). The results highlight the potential of polynuclear manganese complexes as high-contrast electrochromic materials for next-generation smart windows and adaptive optical technologies. Full article