Search Results (123)

New copper(II) (C1) and palladium(II) (C2) complexes with S,O-tetradentate ligand (L) derived from thiosalicylic and thiopropionic acids were synthesized. In cell-based assays, (C1) exhibited the most pronounced activity within the tested compound series and was therefore advanced for mechanistic evaluation in 4T1 triple-negative breast cancer cells. (C1) significantly reduced 4T1 cell viability by inducing early and late apoptosis, accompanied by mitochondrial membrane depolarization and enhanced cytochrome C release. Consistently, (C1) increased the Bax/Bcl-2 ratio, promoting a pro-apoptotic shift. In parallel, (C1) triggered autophagy, as evidenced by decreased p62 and LC3B levels, induced G0/G1 cell-cycle arrest, and suppressed proliferative signaling by downregulating Ki67, cyclin D, and phosphorylated AKT. The DNA-binding studies showed moderate to strong affinity, favoring minor groove binding, with higher affinity for (C1) than for (C2). Tryptophan fluorescence quenching indicated a strong interaction with BSA via a predominantly static mechanism, more pronounced for (C1). Molecular docking at the DNA and BSA binding sites corroborated experimental findings and suggested favorable interactions between the complexes and apoptosis-related proteins (CASP3, BAX, and BCL2). The integrated experimental and computational data identify (C1) as a biologically active compound with multimodal biological effects in vitro, supporting further structural optimization and mechanistic investigation. Full article

The connection of a dianionic 2,2’-biimidazolate (biim²⁻) bridging unit to cis-[Cr(N^∩N)₂]³⁺ (N^∩N is a chelating didentate ligand) or cis-[Cr(N^∩N^∩N^∩N)]³⁺ building blocks (N^∩N^∩N^∩N is a chelating tetradentate ligand) produces heteroleptic pseudo-octahedral [CrN₆]⁺ chromophores. Their reduced cationic charge is compatible with the subsequent complexation of trivalent lanthanides (Ln³⁺) to give d-f {[(N^∩N)₂Cr(biim)]_nLn}⁽³⁺ⁿ⁾⁺ (n = 1–4), {[(N^∩N)₂Cr(biim)]Ln(Tp)₂}²⁺ and {[(N^∩N^∩N^∩N)Cr(biim)]Ln(Tp)₂}²⁺ adducts (Tp is tri(1H-pyrazol-1-yl)-λ⁴-borate). Moving from polyaromatic N^∩N (1,10 phenanthroline) to saturated N^∩N^∩N^∩N polyamine (cyclam) receptors controls the photophysical properties and leads to tunable light conversion in the target heterometallic complexes when Eu(III) is exploited as the activator for downshifting and Er(III) as the activator for upconversion. Full article

Salophen-type Schiff base ligands derived from salicylaldehyde and naphthalene aldehydes were synthesized and coordinated to Ni(II) to obtain three nickel complexes (NiL1–NiL3), which were evaluated as heterogeneous electrocatalysts for the methanol electro-oxidation reaction (MOR) in alkaline media. The ligands and complexes were fully characterized by FT-IR, ¹H NMR, EPR, DART-MS, and elemental analysis, confirming tetradentate coordination through imine nitrogen and phenoxide oxygen donors. Electrochemical studies were carried out using carbon paste electrodes modified with 15 wt % of each complex. Cyclic voltammetry revealed that the electrocatalytic activity is mediated by the Ni(II)/Ni(III) redox couple, with Ni(III) oxohydroxide species acting as the active sites for methanol oxidation. Among the evaluated systems, NiL1@CPE showed superior performance at low methanol concentrations, while NiL2@CPE and NiL3@CPE exhibited higher current densities at elevated methanol concentrations. Scan-rate studies indicated that the oxidation process is diffusion-controlled, and a linear response to methanol concentration was observed over a wide concentration range. The results demonstrate that ligand structure and coordination geometry play a crucial role in modulating the electrocatalytic behavior of Ni(II) Schiff base complexes, highlighting their potential as cost-effective molecular catalysts for alkaline methanol oxidation. Full article

Cisplatin’s chemotherapy is hindered by drug resistance and toxicity, making copper complexes a potential alternative. A novel copper(II) complex, [CuLBr], was synthesized from a tetradentate vicinal dioxime ligand (H₂L) and characterized. [CuLBr] features a distorted square pyramidal geometry with a CuN₄Br chromophore. DFT calculations showed a narrowed HOMO-LUMO gap and increased electrophilicity, enhancing its chemical reactivity. [CuLBr] exhibited potent biomimetic catalytic activity, functioning as an efficient superoxide dismutase mimic and catalase mimic. Biophysical studies (UV-Vis, fluorescence, and viscosity) demonstrated a strong, spontaneous affinity of [CuLBr] for calf thymus DNA and Human Serum Albumin, suggesting groove-binding and static quenching mechanisms. In vitro assays revealed superior anticancer activity against HepG-2, HCT-116, and MDA-MB-231 cell lines, with greater selectivity than the free ligand and doxorubicin. Molecular docking studies reveal a high binding affinity of [CuLBr] with key proteins, including ferredoxin-1 and VEGF. This may suggest potential dual mechanisms of action, involving the induction of cuproptosis and the inhibition of tumor angiogenesis. These findings position [CuLBr] as an effective multi-metal-based anticancer agent with advantageous selectivity. Full article

Although various phosphorescent organic light-emitting diodes (PhOLEDs) have been developed, their lifetimes remain shorter than those of fluorescent OLEDs. In this study, a novel Pt(II) complex featuring a tetradentate ligand composed of bipyridine and phenoxypyridine, referred to as LL-O, was synthesized and fully characterized to evaluate its potential as a dopant for PhOLEDs. Geometry-optimized calculations indicate that LL-O adopts a distorted square–planar structure around the Pt(II) center. The complex displays bluish-green emission with maxima at 490 and 518 nm. However, it exhibits a low photoluminescence quantum yield (4%), primarily due to a dominant non-radiative decay rate that surpasses the radiative decay rate. Natural transition orbital analysis reveals that the emission of LL-O originates from a combination of triplet ligand-centered (³LC), triplet ligand-to-ligand charge-transfer (³LL′CT), and triplet metal-to-ligand charge-transfer (³MLCT) transitions. This compound also demonstrates high thermal stability (decomposition temperature > 340 °C) and an appropriate HOMO energy level (−5.58 eV), making it suitable for use as a dopant in versatile PhOLEDs. Full article

According to the World Health Organization, breast cancer is the cancer that affects the largest number of people each year, especially women. Millions of women are diagnosed with it each year, and hundreds of thousands die from it. Research into new types of drugs, including metal complexes, including those containing tetradentate Schiff bases as ligands, offers a chance to reduce this number. Various cell lines are being used to test their effectiveness in cancer therapy, with the MCF-7 cancer cell line being the most commonly used. A literature search was conducted in four major databases: PubMed, SciELO. The Boolean operator “and” was used to refine the search strategy, combining the terms Schiff base, breast cancer, MCF-7 and metal complexes. Studies published between 2020 and 2025 investigating the cytotoxic activity of metal complexes with Schiff base ligands on the MCF-7 breast cancer cell line were included in the analysis. Articles were considered eligible if they were written in English. As a result of the database search, 37 scientific articles were selected and divided into three groups based on the ligand structure. The largest group of articles described the synthesis, structure, and anticancer activity of metal complexes with ligands based on the salicylaldehyde structure. These were included in the first group of complexes described. The second, extremely interesting and promising group of compounds consisted of metal complexes with ligands containing a sulfur atom. The last group included metal complexes with Schiff base ligands that were not included in the two previously mentioned groups. As indicated by the research results contained in the reviewed articles, Schiff base metal complexes constitute an interesting group of compounds characterized by a range of activities, including anticancer activity, which may in the future be used in anticancer therapy. They may also represent a cheaper and more effective alternative to platinum-based drugs. Full article

The reactions of UO₂(NO₃)₂·6H₂O or UO₂(O₂CMe)₂·2H₂O and 2,2′-{(1,2-ethanediyl)bis[nitrilo(phenyl)methylidene]}bisphenol (H₂L) in MeOH and DMF have provided access to complexes [UO₂(L)(MeOH)] (1) and [UO₂(L)(DMF)]·DMF (2·DMF), respectively. The molecular structures of the complexes are similar. The central U^VI atom is surrounded by five oxygen and two nitrogen atoms in a distorted pentagonal bipyramidal geometry; the two uranyl oxygen atoms are at the axial positions. Two phenolato oxygen and two imino nitrogen atoms from the tetradentate chelating (1.1111 using Harris notation) L²⁻ ligand are located at the equatorial plane, which is completed by the oxygen atom of a terminally ligated solvent (MeOH, DMF) molecule. Interestingly, the L²⁻ ligand adopts a chair (or stepped) conformation in 1 and a boat conformation in 2·DMF. The supramolecular features of 1 and 2·DMF are distinctly different due to the different H-bonding abilities of coordinated MeOH and DMF, and the presence of an extra-lattice solvent molecule in the latter. The solid complexes were studied by IR, Raman, electronic (UV/Vis), and emission spectroscopic techniques. Complex 1 decomposes in CHCl₃ and DMSO, whereas the molecular structure of 2 is retained in these solvents. A new polymorph of the free ligand, H₂L(B), has also been discovered and its crystal structure is described. Full article

The potentially tetradentate SNNS ligand N,N′-(ethane-1,2-diyl)bis(N″-(diethylcarbamothioyl)benzimidamide, H₂L, was synthesized by the reaction of ethylenediamine with two equivalents of the corresponding benzimide chloride. H₂L readily reacts with [AuCl(tht)] (tht = tetrahydrothiophene) under formation of the binuclear gold(I) complex [(AuCl)₂(H₂L-κS,S′)] (1) using its thiocarbonyl units as donors, while the nitrogen atoms remain uncoordinated, and no deprotonation was observed. The gold atoms establish almost linear Cl–Au–S bonds. The terminal Cl⁻ ligands can be replaced with thiocyanate units, giving [Au(SCN-κS)}₂((H₂L-κS,S′)] (2). The use of [Au(PPh₃)Cl] as a starting material gives the cation [{Au(PPh₃)}₂(H₂L-κS,S′)]²⁺ (3), which can be isolated as its PF₆⁻ salt. The products are air-stable compounds, which have been isolated in crystalline form and studied by X-ray diffraction and spectroscopic methods (IR, NMR, and MS). Full article

This review provides a comprehensive overview of recent advances in the synthesis, structural characterization, and applications of Ru(II), Ru(III), and Ru(VI) complexes, which bear tetradentate Schiff bases of salen type. Ruthenium complexes exhibit catalytic, electrochemical, and biological properties, serving as multifunctional platforms that integrate fundamental aspects of coordination chemistry with potential practical applications. Full article

A tetradentate Pt(II) complex with a 5/6/6 structural backbone, Pt(PhPiPy-O-PytmCz), was synthesized by incorporating two distinct cycloalkyl groups. These structural modifications significantly enhanced the photoluminescence quantum yield and effectively increased the distance between molecules, thereby mitigating undesirable intermolecular interactions and triplet-state quenching. This strategic molecular design resulted in an external quantum efficiency of 11.5% at a wavelength of 539 nm and significantly enhanced operational lifetimes in green phosphorescent organic light-emitting diodes (OLEDs). These findings are expected to inspire the development of new green luminescent materials and innovative strategies in OLED technology. Full article

Co(II) complexes have shown promising applications as single-molecule magnets (SMMs) in quantum computing and structural biology. Deciphering the Co(II) complexes may facilitate the development of SMM materials. Structural optimizations and calculations of chemical and magnetic properties were performed for Co(II) complexes with a tripodal tetradentate phenolate-amine ligand using MP2/aug-cc-pvdz, MP2/Def2svp, and CASSCF/Def2svp methods. The Second Order Perturbation Theory Analysis of Fock Matrix in NBO Basis unravels that Co(II) ions form unusual coordinate quasi-double bonds with ligand oxygen donor atoms, and the bond strengths range from 142.01 kcal/mol to 167.36 kcal/mol but lack further spectrometric evidence. The average 151.70 kcal/mol of the Co(II-O coordinates quasi-double bonds are formed mainly by two lone pairs of electrons from the ligand phenolate donor oxygen atoms. Dispersion forces contribute 24%, 28%, 27%, and 31% to the Co(II)-ligand interaction. Theoretical results of ZFS D, transversal ZFS E, and g-factor agree well with the experimental values. Magnetic susceptibility parameters calculated based on 5 doublet roots account for 85% of results computed 40 doublet roots are specified. These insights may aid in the rational design of SMM materials and Co(II) porphyrin fullerene conjugate for CO₂ electroreduction with superior magnetic properties. Full article

A zinc complex bearing a pyrazolone-based azomethine ligand has been synthesized for blue-emitting organic light-emitting diodes (OLEDs). The azomethine ligand H₂L and the complex [ZnL·H₂O] were characterized by IR, 1H NMR, XRD, and TGA/DSC techniques. According to a single-crystal X-ray diffraction analysis, the complex [ZnL·H₂O] has a molecular structure. Its solid-state PL maxima appear to be at 416 nm and emit moderate blue emission with a quantum yield (QY) of 2%, with a dehydrated form of the complex showing greater efficiency with a QY of 55.5%. ZnL-based electroluminescent devices for OLED applications were fabricated. The devices exhibit blue emission with brightness up to 5300 Cd/A. Full article

The chemical interaction of salicylic acid, formaldehyde, and sulfuric acid produced a disalicylic ligand (3,3′-dicarboxy-2,2′-dihydroxydiphenylmethane, DCM), which was then allowed to coordinate with copper (II) ions. The solid compounds’ chemical structures were determined using elemental analysis, UV-Vis, FT-IR, MS, ¹H-NMR, PXRD, SEM, TEM, magnetic studies, as well as molecular modeling based on DFT (density functional theory) calculations. It was proposed that the ligand coordinates in a tetradentate fashion with the copper ion to give a square-planar binuclear complex. A significant difference in the diffraction patterns between Cu(II)–DCM (amorphous) and DCM (crystalline) was displayed using an X-ray diffraction analysis. Spherical granules were identified throughout through morphology analysis using SEM and TEM. UV-Vis spectra were used to quantify the optical characteristics such as the energy gap, optical conductivity, refractive index, and penetration depth. The band gap values that lie within the semiconductor region suggested that the compounds could be used for electronic applications. The optimized structure of the synthesized Cu(II)–DCM complex was investigated using DFT and TD-DFT (time-dependent density functional theory) at the B3LYP/6-31G(d, p) level, with the LANL2DZ basis set for Cu in an ethanol solvent and the gas environment modeled by CPCM. The experimental data suggest a square-planar geometry of the Cu(II) binuclear complex. The theoretical calculations support the proposed structure of the compound. The cytotoxicity of the DCM against HCT–116 (human colon cancer) cells was tested, and the outcome exhibited good inhibitions of growth. A molecular docking (MD) examination was carried out to illustrate the binding mode/affinity of the prepared compounds (DCM and Cu(II)–DCM) in the active site of the receptor protein [CDK2 enzyme, PDB ID: 6GUE]. The compounds formed hydrogen bonds with the amino acid residues of the protein, increasing the binding affinity from −7.2 to −9.3 kcal/mol through the coordination process. The information from this current study, particularly the copper complex, is beneficial for exploring new compounds that have anticancer potential. 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

Vibrational circular dichroism (VCD) enhancement by low-lying electronic states (LLESs) is a fascinating phenomenon, but accounting for it theoretically remains a challenge despite significant research efforts over the past 20 years. In this article, we synthesized two transition metal complexes using the tetradentate Schiff base ligands (R,R)- and (S,S)-N,N′-Bis(3,5-di-tert-butylsalicylidene)-1,2-cyclohexanediamine with Co(II) and Mn(III), referred to as Co(II)-salen-chxn and Mn(III)-Cl-salen-chxn, respectively. Their stereochemical properties were explored through a combined experimental chiroptical spectroscopic and theoretical approach, with a focus on Co(II)-salen-chxn. Extensive conformational searches in CDCl₃ for both high- and low-spin states were carried out and the associated infrared (IR), VCD, ultraviolet-visible (UV-Vis) absorption, and electronic circular dichroism (ECD) spectra were simulated. A good agreement between experimental and simulated data was achieved for IR, VCD, UV-Vis, and ECD, except in the case of VCD of Co(II)-salen-chxn which exhibits significant intensity enhancement and monosignate VCD bands, attributed to the LLESs. Interestingly, detailed comparisons with Mn(III)-Cl-salen-chxn and previously reported Ni(II)-salen-chxn and Cu(II)-salen-chxn complexes suggest that the enhancement factor is predicted by the current density functional theory simulations. However, the monosignate signatures observed in the experimental Co(II) VCD spectrum were not captured theoretically. Based on the experiment and theoretical VCD and ECD comparison, it is tentatively suggested that Co(II)-salen-chxn exists in both low- and high-spin states, with the former being dominant, while Mn(III)-Cl-salen-chxn in the high-spin state. The study indicates that VCD enhancement by LLESs is at least partially captured by the existing theoretical simulation, while the symmetry consideration in vibronic coupling provides further insight into the mechanisms behind the VCD sign-flip. Full article