Copper(II) complexes with tridentate pyrazole-based ligands: synthesis, characterization, DNA cleavage activity and cytotoxicity

Structural features and antiproliferative activity of Pd(II) complexes with halogenated ligands: a comparative study between Schiff base and reduced Schiff base complexes

In order to investigate the structural features and antiproliferative activity of Pd(II) complexes containing halogenated ligands with different flexibility, several Schiff base and reduced Schiff base Pd(II) complexes, namely X1X2PicPd, X1X2PyPd, X1X2Pic(R)Pd, and X1X2Py(R)Pd (where X1 = X2 = Cl, Br and I; Pic: 2-picolylamine; Py = 2-(2-pyridyl)ethylamine), were synthesized and characterized by spectroscopic methods and, in the case of Br2PyPd, Cl2Py(R)Pd and ClBrPy(R)Pd, also by X-ray crystallography. The results of the X-ray crystallography showed that in both series of complexes the Pd(II) ion has a distorted square-planar geometry, although the coordination modes of the two ligands are different. In the Schiff base-type complexes the ligand acts as a tridentate chelate with NN'O donor atoms, whereas in the reduced Schiff base-type complexes the ligand acts as a bidentate chelate with NN' donor atoms. In both series of complexes, the chloride ions occupy the residual coordination sites of the Pd(II) ion. TD-DFT calculations were performed for a better understanding of the UV-Vis spectra. From these calculations it was found that the signal appearing at ∼400 nm in the complexes with reduced Schiff base ligands (X1X2Pic(R)Pd and X1X2Py(R)Pd) is mainly due to a HOMO → LUMO transition, while for the Schiff base complex ClBrPyPd the signal is due to a HOMO → LUMO+1 transition. For the complex I2PicPd, combinations of HOMO-4 → LUMO and HOMO-2 → LUMO transitions were found to be responsible for that signal. In regard to the biological activity profile, all complexes were first investigated as proteasome inhibitors by fluorometric methods. From these enzymatic assays, it emerged that they are good inhibitors with IC50 values in the low-micromolar range and that their inhibitory activity is strictly related to the presence of the metal ion. Subsequently they were also subjected to cell-based assays (the resazurin method) to assess their antiproliferative properties by using two leukemic cell lines, namely the drug-sensitive CCRF-CEM cell line and its multidrug-resistant sub-cell line CEM/ADR5000. In this test they displayed IC50 values in the sub-micromolar and low-micromolar range determined for a selected metal complex (Br2Pic(R)Pd) and ligand (Cl2Pic(R)), respectively. Moreover, docking studies were performed on the two expected molecular targets, i.e. proteasome and DNA, to shed light on the mechanisms of action of these types of Pd(II) complexes.

Novel binuclear copper(II) complexes with sulfanylpyrazole ligands: synthesis, crystal structure, fungicidal, cytostatic, and cytotoxic activity

New binuclear copper(II) [Cu(II)] tetraligand complexes (six examples) with sulfanylpyrazole ligands were synthesized. Electron spin resonance (ESR) studies have shown that in solution the complexes are transformed to the mononuclear one. Fungicidal properties against Candida albicans were found for the Cu complexes with benzyl and phenyl substituents. An in vitro evaluation of the cytotoxic properties of Cu chelates against HEK293, Jurkat, MCF-7, and THP-1 cells identified the Cu complex with the cyclohexylsulfanyl substituent in the pyrazole core as the lead compound, whereas the Cu complex without a sulfur atom in the pyrazole ligand had virtually no cytotoxic or fungicidal activity. The lead Cu(II) complex was more active than cisplatin. Effect of the S-containing Cu complex on apoptosis and cell cycle distribution has been investigated as well.

New copper(II) and oxidovanadium(IV) complexes with a vitamin B6 Schiff base: mechanism of action and synergy studies on 2D and 3D human osteosarcoma cell models

We report the synthesis, characterization and anticancer activity of a new Schiff base (H2L) derived from the condensation of pyridoxamine with pyridoxal and its novel copper(II) and oxidovanadium(IV) complexes: [Cu(HL)Cl] (1), [Cu(LH2)(phen)]Cl2 (2), [Cu(LH2)(amphen)]Cl2 (3), [VIVO(HL)Cl] (4), and [VIVO(LH2)(phen)]Cl2 (5), where phen is 1,10-phenanthroline and amphen is its 5-amino derivative. All compounds were characterized by analytical and spectroscopic techniques, namely FTIR, UV-vis and EPR spectroscopy. Their stability in aqueous media was evaluated, revealing that the presence of the phen co-ligand significantly increases the stability. The ternary Cu(II) complexes (2 and 3) impaired cell viability of osteosarcoma cells (MG-63) (IC50 values of 3.6 ± 0.6 and 7 ± 1.9 μM for 2 and 3), while 1 and the VIVO complexes did not show relevant anticancer activity. Complexes 2 and 3 are also more active than cisplatin (CDDP). Synergistic studies between 2 and sorafenib showed significant synergism on MG-63 cells for the following combinations: 2 (2.0 μM) + sorafenib (10.0 μM) and 2 (2.5 μM) + sorafenib (12.5 μM), whilst the combination of 2 and CDDP did not show synergy. Complex 2 interacts with DNA, inducing significant genotoxic effects on MG-63 cells from 1.0 to 2.5 μM and it increases the ROS levels 880% over basal. Moreover, 2 induces apoptosis at 1.0 and 2.0 μM, while its combination with sorafenib induces apoptosis and necrosis. Finally, compound 2 reduces the cell viability of MG-63 spheroids showing an IC50 value 7-fold lower than that of CDDP (8.5 ± 0.4 μM vs. 65 ± 6 μM). The combination of 2 and sorafenib also showed synergism on spheroids, suggesting that the combination of these drugs improves the anticancer effect against bone cancer cells.

Fine-tuning the cytotoxicity of ruthenium(II) arene compounds to enhance selectivity against breast cancers

Ruthenium-based complexes have been suggested as promising anticancer drugs exhibiting reduced general toxicity compared to platinum-based drugs. In particular, Ru(η6-arene)(PTA)Cl2 (PTA = 1,3,5-triaza-7-phosphaadamantane), or RAPTA, complexes have demonstrated efficacy against breast cancer by suppressing metastasis, tumorigenicity, and inhibiting the replication of the human tumor suppressor gene BRCA1. However, RAPTA compounds have limited cytotoxicity, and therefore comparatively high doses are required. This study explores the activity of a series of RAPTA-like ruthenium(II) arene compounds against MCF-7 and MDA-MB-231 breast cancer cell lines and [Ru(η6-toluene)(PPh3)2Cl]+ was identified as a promising candidate. Notably, [Ru(η6-toluene)(PPh3)2Cl]Cl was found to be remarkably stable and highly cytotoxic, and selective to breast cancer cells. The minor groove of DNA was identified as a relevant target.

Mechanistic Studies of Arene-Ruthenium(II) Complexes with Carbothioamidopyrazoles as Alternative Cancer Drugs

Arene-ruthenium(II) complexes with carbothioamidopyrazoles at the C-2 and C-5 positions have been recognized as chemotherapeutic agent alternatives to cisplatin and its oxaliplatin analogs. The aim of this study was to continue research on the biological aspect of arene-ruthenium(II) complexes and their anticancer activity. The present paper includes an additional 12 new tumor cells, analyzed by MTT, and employs a series of extended bioassays to better understand their potential mechanism of antitumor activity. The following tests were conducted: membrane permeability studies, intramolecular reactive oxygen and nitrogen species (ROS/RNS) assays, mitochondrial potential changes, DNA analysis by comet assay using the electrophoresis method, measurement of cleaved PARP protein levels, and determination of apoptotic and necrotic cell fractions by fluorescence microscopy. Additionally, the article presents lipophilicity studies based on RP-TLC and molecular docking studies. We hope that the presented data will prove useful in practical treatment, especially for patients with cancer.

Novel Biologically Active N-Substituted Benzimidazole Derived Schiff Bases: Design, Synthesis, and Biological Evaluation

Herein, we present the design and synthesis of novel N-substituted benzimidazole-derived Schiff bases, and the evaluation of their antiviral, antibacterial, and antiproliferative activity. The impact on the biological activity of substituents placed at the N atom of the benzimidazole nuclei and the type of substituents attached at the phenyl ring were examined. All of the synthesized Schiff bases were evaluated in vitro for their antiviral activity against different viruses, antibacterial activity against a panel of bacterial strains, and antiproliferative activity on several human cancer cell lines, thus enabling the study of the structure-activity relationships. Some mild antiviral effects were noted, although at higher concentrations in comparison with the included reference drugs. Additionally, some derivatives showed a moderate antibacterial activity, with precursor 23 being broadly active against most of the tested bacterial strains. Lastly, Schiff base 40, a 4-N,N-diethylamino-2-hydroxy-substituted derivative bearing a phenyl ring at the N atom on the benzimidazole nuclei, displayed a strong antiproliferative activity against several cancer cell lines (IC₅₀ 1.1-4.4 μM). The strongest antitumoral effect was observed towards acute myeloid leukemia (HL-60).

Synthesis, characterization, antioxidant potential, and cytotoxicity screening of new Cu(II) complexes with 4-(arylchalcogenyl)-1H-pyrazoles ligands

Two new Cu(II) complexes based on 4-(arylchalcogenyl)-1H-pyrazoles monodentate bis(ligand) containing selenium or sulfur groups (2a and 2b) have been synthesized and characterized by IR spectroscopy, high-resolution mass spectrometry (HRMS), and by X-ray crystallography. In the effort to propose new applications for the biomedical area, we evaluated the antioxidant activity and cytotoxicity of the newly synthesized complexes. The antioxidant activity of the Cu(II) complexes (2a - 2b) were assessed through their ability to inhibit the formation of reactive species (RS) induced by sodium azide and to scavenge the synthetic radicals 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2-azinobis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS⁺). Both copper complexes containing selenium (2a) and sulfur (2b) presented in vitro antioxidant activity. The (1a - 1b and 2a - 2b) compounds did not show cytotoxicity in V79 cells at low concentrations. Furthermore, the antiproliferative activity of free ligands (1a - 1b) and their complexes (2a - 2b) were tested against two human tumor cell lines: MCF-7 (breast adenocarcinoma) and HepG2 (hepatocarcinoma). Also, 2a was tested against U2OS (osteosarcoma). Our results demonstrated that 1a and 1b show little or no growth inhibition activities on human cell lines.The 2a compound exhibited good cytotoxic activity toward human tumor cell lines. However, 2a showed no selectivity, with a selectivity index of 1.12-1.40. Complex 2b was selective for the MCF-7 human tumor cell lines with IC₅₀ of 59 ± 2 μM. This study demonstrates that the Cu(II) complexes 2a and 2b represent promising antitumoral compounds, and further studies are necessary to understand the molecular mechanisms of these effects.

Copper(ii) complexes with 2-ethylpyridine and related hydroxyl pyridine derivatives: structural, spectroscopic, magnetic and anticancer in vitro studies

Copper(ii) complexes with 2-ethylpyridine (1 and 2), 2-(hydroxyethyl)pyridine (3) and 2-(hydroxymethyl)pyridine (4) have been synthesized and characterized. All inorganic compounds have been studied by X-ray diffraction, thermogravimetry, vibrational and EPR spectroscopy as well as theoretical methods. The geometry of the complexes 1, 3 and 4 adopts nearly perfect geometry close to square planar (1, 4) or square pyramid (3) stereochemistry, respectively. The distortion of five coordinated copper(ii) ions in complex 2 indicates intermediate geometry between square pyramidal and trigonal pyramidal geometry. Further, the magnetic measurements have shown antiferromagnetic behaviour of the prepared complexes in a wide range of temperatures. The antiferromagnetic behaviour of 2 should originate from the superexchange interactions between each copper(ii) ion by the mixed chloride and μ4-O ion pathways. Besides, the weak antiferromagnetic character of 2 can be also attributed to the presence of intrachain exchange between dimeric units through double oxide ion. In complex 3, strong antiferromagnetic coupling between Cu(ii) centres in the Cu2O2Cl2 moiety is found. The cytotoxicity of all compounds was tested in vitro against various cancer cell lines: human lung adenocarcinoma (A549), human breast adenocarcinoma (MCF7), human prostate carcinoma; derived from metastatic site: brain (DU-145) and two normal cell lines: human embryonic kidney (HEK293T) and human keratinocyte (HaCat). Furthermore, Pluronic P-123 micelles loaded with selected complexes (1 and 3) were proposed to overcome low solubility and to minimize systemic side effects. More detailed study revealed that complex 3 loaded inside micelles causes DU-145 cells' death with simultaneous decrease of mitochondrial membrane potential and a high level of reactive oxygen species generation. The stability of the compounds 1-4 in DMSO was confirmed by UV-Vis and FT-IR spectra studies.

2-Mercaptobenzimidazole clubbed hydrazone for Alzheimer’s therapy: In vitro, kinetic, in silico, and in vivo potentials

Alzheimer’s is a type of dementia that affects the affected person’s thinking, memory, and behavior. It is a multifactorial disease, developed by the breakdown of the neurotransmitter acetylcholine via acetylcholinesterase (AChE). The present study was designed to evaluate potential inhibitors of acetylcholinesterase that could be used as a therapeutic agent against Alzheimer’s disease (AD). For this course, synthetic compounds of the Schiff bases class of 2-mercaptobenzimidazole hydrazone derivatives (9–14) were determined to be potent acetylcholinesterase inhibitors with IC₅₀ values varying between 37.64 ± 0.2 and 74.76 ± 0.3 μM. The kinetic studies showed that these are non-competitive inhibitors of AChE. Molecular docking studies revealed that all compounds accommodate well in the active site and are stabilized by hydrophobic interactions and hydrogen bonding. Molecular dynamics (MD) simulations of selected potent inhibitors confirm their stability in the active site of the enzyme. Moreover, all compounds showed antispasmodic and Ca²⁺ antagonistic activities. Among the selected compounds of 2-mercaptobenzimidazole hydrazone derivatives, compound 11 exhibited the highest activity on spontaneous and K⁺-induced contractions, followed by compound 13. Therefore, the Ca²⁺ antagonistic, AChE inhibition potential, and safety profile of these compounds in the human neutrophil viability assay make them potential drug candidates against AD in the future.

A bibliographic survey of the supramolecular architectures sustained by delocalised C–I⋯π(arene) interactions in metal-organic crystals

A survey of the crystallographic literature of metal-organic crystal structures for the presence of C–I···π(arene) interactions where the iodide atom occupies a position close to plumb to the ring centroid, corresponding to a delocalised interaction, and is within the assumed sum of the van der Waals radii, i.e. 3.88 Å, has been undertaken. The majority of the 26 identified examples feature supramolecular chains of varying topology whereby C–I···π(arene) contacts are readily identified and apparently operating independently of other obvious supramolecular synthons. The next most prevalent supramolecular aggregate was zero-dimensional, containing up to a maximum of three molecules. While there were three examples of two-dimensional arrays among a series of isostructural crystal structures, no examples of three-dimensional structures largely sustained by C–I···π(arene) interactions were noted. This distribution of supramolecular aggregation patterns matched that noted for all-organic systems. In terms of the overall adoption rate, delocalised C–I···π(arene) interactions were found in 3% of crystals of metal-organic species where they could form, a percentage lower than 4% noted for all-organic crystals.

Design and Anticancer Properties of New Water-Soluble Ruthenium–Cyclopentadienyl Complexes

Ruthenium complexes are emerging as one of the most promising classes of complexes for cancer therapy. However, their limited aqueous solubility may be the major limitation to their potential clinical application. In view and to contribute to the progress of this field, eight new water-soluble Ru(II) organometallic complexes of general formula [RuCp(mTPPMS)_n(L)] [CF₃SO₃], where mTPPMS = diphenylphosphane-benzene-3-sulfonate, for n = 2, L is an imidazole-based ligand (imidazole, 1-benzylimidazole, 1-butylimidazole, (1-(3-aminopropyl)imidazole), and (1-(4-methoxyphenyl)imidazole)), and for n = 1, L is a bidentate heteroaromatic ligand (2-benzoylpyridine, (di(2-pyridyl)ketone), and (1,2-(2-pyridyl)benzo-[b]thiophene)) were synthesized and characterized. The new complexes were fully characterized by NMR, FT-IR, UV–vis., ESI-HRMS, and cyclic voltammetry, which confirmed all the proposed molecular structures. The antiproliferative potential of the new Ru(II) complexes was evaluated on MDAMB231 breast adenocarcinoma, A2780 ovarian carcinoma, and HT29 colorectal adenocarcinoma cell lines, showing micromolar (MDAMB231 and HT29) and submicromolar (A2780) IC₅₀ values. The interaction of complex 6 with human serum albumin (HSA) and fatty-acid-free human serum albumin (HSA^faf) was evaluated by fluorescence spectroscopy techniques, and the results revealed that the ruthenium complex strongly quenches the intrinsic fluorescence of albumin in both cases.

Co(II), Ni(II), and Zn(II) complexes based on new hybrid imine-pyrazole ligands: structural, spectroscopic, and electronic properties

The present work reports the theoretical investigation of Co(II), Ni(II), and Zn(II) complexes containing Schiff bases (used as ligands) derived from the reaction of 2-hydroxy-1-naphthaldehyde with N-(2-aminoethyl) pyrazoles. The spectral analyses were carried out using infrared, Raman, and UV-Vis spectroscopy. Vibrational analyses were performed in order to investigate the mechanisms involving metal-ligand and intra-ligand vibrations and indicated the possibility of charge transfer related to the transitions n[Formula: see text]* and [Formula: see text]*. Structure optimizations and normal coordinate force field calculations were performed via the density functional theory (DFT) method at the HSE06/6-311G(d,p)/LanL2DZ level. A thorough analysis was also conducted regarding the nonlinear optical (NLO) properties and the natural bond orbital (NBO) of the complexes. The results show that these complexes have prospective application as materials for NLO. Furthermore, the NBO analysis confirms the coordination between the lone pair (LP) electrons of the donor atoms (O and N) and the metal acceptors. Finally, studies were conducted regarding the electronic properties of the complexes; among the properties investigated included the frontier molecular orbitals (FMO) and the molecular electrostatic potential (MEP), allowing to determine the energy gap and charge distribution.

Antioxidant and cytotoxic activities of selected salicylidene imines: experimental and computational study

Selected salicylidene imines were evaluated for their antioxidant and cytotoxic potentials. Several of them exerted potent scavenging capacity towards ABTS radical and hydrogen peroxide. The insight into the preferable antioxidative mechanism was reached employing density functional theory. In the absence of free radicals, the SPLET mechanism is dominant in polar surroundings, while HAT is prevailing in a non-polar environment. The results obtained for the reactions of the most active compounds with some medically relevant radicals pointed out competition between HAT and SPLET mechanisms. The assessment of their cytotoxic properties revealed inhibition of ER-a human breast adenocarcinoma cells or estrogen-independent prostate cancer cells. Molecular docking study with the cyclooxygenase (COX) 2 enzyme was performed to examine the most probable bioactive conformations and possible interactions between the tested derivatives and COX-2 binding pocket.

Copper(II) Complexes of Sulfonated Salan Ligands: Thermodynamic and Spectroscopic Features and Applications for Catalysis of the Henry Reaction

Copper(II) complexes formed with sulfonated salan ligands (HSS) have been synthesized, and their coordination chemistry has been characterized using pH-potentiometry and spectroscopic methods [UV-vis, electron paramagnetic resonance (EPR), and electron-electron double resonance (ELDOR)-detected NMR (EDNMR)] in aqueous solution. Several bridging moieties between the two salicylamine functions were introduced, e.g., ethyl (HSS), propyl (PrHSS), butyl (BuHSS), cyclohexyl (cis-CyHSS, trans-CyHSS), and diphenyl (dPhHSS). All of the investigated ligands feature excellent copper(II) binding ability via the formation of a (O^-,N,N,O^-) chelate system. The results indicated that the cyclohexyl moiety significantly enhances the stability of the copper(II) complexes. EPR studies revealed that the arrangement of the coordinated donor atoms is more symmetrical around the copper(II) center and similar for HSS, BuHSS, CyHSS, and dPhHSS, respectively, and a higher rhombicity of the g tensor was detected for PrHSS. The copper(II) complexes of the sulfosalan ligands were isolated in solid form also and showed moderate catalytic activity in the Henry (nitroaldol) reaction of aldehydes and nitromethane. The best yield for nitroaldol production was obtained for copper(II) complexes of PrHSS and BuHSS, although their metal binding ability is moderate compared to that of the cyclohexyl counterparts. However, these complexes possess larger spin density on the nitrogen nuclei than that for the other cases, which alters their catalytic activity.

Copper(ii) complexes with tridentate halogen-substituted Schiff base ligands: synthesis, crystal structures and investigating the effect of halogenation, leaving groups and ligand flexibility on antiproliferative activities

To investigate the effect of different halogen substituents and leaving groups and the flexibility of ligands on the anticancer activity of copper complexes, sixteen copper(ii) complexes with eight different tridentate Schiff-base ligands containing pyridine and 3,5-halogen-substituted phenol moieties were synthesized and characterized by spectroscopic methods. Four of these complexes were also characterized by X-ray crystallography. The cytotoxicity of the complexes was determined in three different tumor cell lines (i.e. the A2780 ovarian, HCT116 colorectal and MCF7 breast cancer cell line) and in a normal primary fibroblast cell line. Complexes were demonstrated to induce a higher loss of cell viability in the ovarian carcinoma cell line (A2780) with respect to the other two tumor cell lines, and therefore the biological mechanisms underlying this loss of viability were further investigated. Complexes with ligand L₁ (containing a 2-pycolylamine-type motif) were more cytotoxic than complexes with L₂ (containing a 2-(2-pyridyl)ethylamine-type motif). The loss of cell viability in A2780 tumor cells was observed in the order Cu(Cl₂-L₁)NO₃ > Cu(Cl₂-L₁)Cl > Cu(Br₂-L₁)Cl > Cu(BrCl-L₁)Cl. All complexes were able to induce reactive oxygen species (ROS) that could be related to the loss of cell viability. Complexes Cu(BrCl-L₁)Cl and Cu(Cl₂-L₁)NO₃ were able to promote A2780 cell apoptosis and autophagy and for complex Cu(BrCl-L₁)Cl the increase in apoptosis was due to the intrinsic pathway. Cu(Cl₂-L₁)Cl and Cu(Br₂-L₁)Cl complexes lead to cellular detachment allowing to correlate with the results of loss of cell viability. Despite the ability of the Cu(BrCl-L₁)Cl complex to induce programmed cell death in A2780 cells, its therapeutic window turned out to be low making the Cu(Cl₂-L₁)NO₃ complex the most promising candidate for additional biological applications.

Probing DNA-Cleavage Efficiencies of Copper(II) Complexes: A Computational Perspective

Theoretical studies on DNA-cleavage efficiencies of Cu(II) complexes 1-3 were carried out using density functional theory (DFT). The optimized Cu(II) complexes were allowed to bind to glutathiones (GSH) and ascorbic acids (VC) by the docking program so that corresponding docking structures can be obtained. To predict DNA-cleavage efficiencies, the docking structures of Cu(II) complexes with GSH and VC were further optimized by DFT. The activation energies of electrons from GSH to complexes, the redox potentials of these complexes, and binding energies of these complexes with GSH and VC were calculated. The efficiencies of complexes cleaving DNA were predicted and found to be in agreement with the experimental results. Finally, three occupied molecular orbitals of docking structures (GSH-complexes) were analyzed, and the DNA-cleavage abilities of complexes were also explained by the electron distribution on the three occupied orbitals. This work has important implications understanding the DNA-cleavage mechanism of Cu(II) complexes, which might be helpful for designing novel anticancer Cu(II) complexes for the future.

A fluorescent Cu(ii) complex as a dual functional sensor for selective and sensitive detection of acetone and Cd(ii) pollutants

In this study, Cu²⁺ perchlorate complexes of 3,5-dimetylpyrazole(dmpy), namely [Cu(dmpy)₃(H₂O)₂](H₂O)(ClO₄)₂ (1), were prepared and characterized by X-ray diffraction (XRD), thermogravimetric analysis (TGA), infrared (IR) spectroscopy, elemental analysis, mass spectrometry, and ultraviolet visible (UV-Vis) spectroscopy. It was determined that Cu²⁺ coordinated to the nitrogen atoms of three dmpy molecules as well as to the oxygen atoms of two H₂O molecules in a square pyramidal geometry. To balance the charge, two uncoordinated perchlorate anions and one H₂O molecule were also present in the lattice. The resulting Cu²⁺ complex was involved in extensive hydrogen bonding, which stabilized the structure. The fluorescence properties of complex 1 were studied in acetonitrile at room temperature upon the addition of different organic solvents. It was confirmed that the complex exhibited remarkable acetone selectivity via a fluorescence quenching mechanism. At low concentrations, the fluorescence intensities were nearly completely quenched via a turn-off mode. Moreover, complex 1 displayed exceptional selectivity, fast detection time, and high sensitivity for Cd²⁺ in aqueous solutions via a fluorescence enhancement mechanism (turn-on mode). Hence, the prepared complex showed potential for application in Cd²⁺ detection. Notably, in an aqueous solution, complex 1 exhibited highly selective fluorescence enhancement effects (turn-on mode) with respect to Cd²⁺ and was not affected by the interference of other metal ions.

The prepared complex 1 exhibited highly sensitive and selective fluorescence quenching (turn-off) effect in the presence of acetone as well as fluorescence enhancement (turn-on) effect toward Cd²⁺ ions in aqueous solutions.

Unusual chemistry of Cu(ii) salan complexes: synthesis, characterization and superoxide dismutase activity

Cu(ii)-salan complexes: structural and spectral characterization, solvent assisted ring cleavage and correlation of superoxide dismutase activity with cyclic voltammetry data and steric effects.

Developing novel zinc(ii) and copper(ii) Schiff base complexes: combined experimental and theoretical investigation on their DNA/protein binding efficacy and anticancer activity

Zn(ii) and Cu(ii) Schiff base complexes having DNA and HSA binding efficacy have been exploited as cancer therapeutic agents.

Theoretical study on the DNA interaction properties of copper(II) complexes

Theoretical studies on DNA-cleavage and DNA-binding properties of a series of Cu(II) complexes [Cu(bimda)(diimine)] 1-5 have been carried out by density functional theory (DFT). The optimized structures of Cu(II) complexes were docked into parallel, antiparallel and mixed G-quadruplexes, with which the binding energies of complexes 1-5 were obtained. The cytotoxicities of these complexes can be predicted preliminarily by the binding energies. To explore the energy changes of Cu(II) complexes in duplex DNA, the optimized structures of these complexes were docked into the duplex DNA, and the obtained docking models were further optimized using QM/MM method. The DNA-cleavage abilities of complexes 1-5 can be predicted accurately and explained reasonably by the computed intra-molecular reorganization energies of these complexes. This work reported here has implications for the understanding of the interaction Cu(II) complexes with the DNA, which might be helpful for the future directing the design of novel anticancer Cu(II) complexes.

Synthesis, DNA binding, cellular DNA lesion and cytotoxicity of a series of new benzimidazole-based Schiff base copper(II) complexes

A series of new benzimidazole containing compounds 2-((1-R-1-H-benzimidazol-2-yl)phenyl-imino)naphthol HL(1-3) (R = methyl, ethyl or propyl, respectively) have been synthesized by Schiff base condensation of 2-(1-R-1-H-benzo[d]imidazol-2-yl)aniline and 2-hydroxy-1-naphthaldehyde. The reactions of HL(1-3) with Cu(NO3)2·2.5H2O led to the corresponding copper(II) complexes [Cu(L)(NO3)] 1-3. All the compounds were characterized by conventional analytical techniques and, for 1 and 3, also by single-crystal X-ray analysis. The interactions of complexes 1-3 with calf thymus DNA were studied by absorption and fluorescence spectroscopic techniques and the calculated binding constants (K(b)) are in the range of 3.5 × 10(5) M(-1)-3.2 × 10(5) M(-1). Complexes 1-3 effectively bind DNA through an intercalative mode, as proved by molecular docking studies. The binding affinity of the complexes decreases with the size increase of the N-alkyl substituent, in the order of 1 > 2 > 3, which is also in accord with the calculated LUMO(complex) energies. They show substantial in vitro cytotoxic effect against human lung (A-549), breast (MDA-MB-231) and cervical (HeLa) cancer cell lines. Complex 1 exhibits a significant inhibitory effect on the proliferation of the A-549 cancer cells. The antiproliferative efficacy of 1 has also been analysed by a DNA fragmentation assay, fluorescence activated cell sorting (FACS) and nuclear morphology using a fluorescence microscope. The possible mode for the apoptosis pathway of 1 has also been evaluated by a reactive oxygen species (ROS) generation study.

Hydrogen bonding and anticancer properties of water-soluble chiral p-cymene Ru(II) compounds with amino-oxime ligands

The investigation of the hydrogen-bonding effect on the aggregation tendency of ruthenium compounds [(η⁶-p-cymene)Ru(κNHR,κNOH)Cl]Cl (R = Ph (1a), Bn (1b)) and [(η⁶-p-cymene)Ru(κ²NH(2-pic),κNOH)][PF₆]₂ (1c), [(η⁶-p-cymene)Ru(κNHBn,κNO)Cl] (2b) and [(η⁶-p-cymene)Ru(κNBn,κ²NO)] (3b), has been performed by means of concentration dependence ¹H NMR chemical shifts and DOSY experiments. The synthesis and full characterization of new compounds 1c, [(η⁶-p-cymene)Ru(κNPh,κ²NO)] (3a) and 3b are also reported. The effect of the water soluble ruthenium complexes 1a-1c on cytotoxicity, cell adhesion and cell migration of the androgen-independent prostate cancer PC3 cells have been assessed by MTT, adhesion to type-I-collagen and recovery of monolayer wounds assays, respectively. Interactions of 1a-1c with DNA and human serum albumin have also been studied. Altogether, the properties reported herein suggest that ruthenium compounds 1a-1c have considerable potential as anticancer agents against advanced prostate cancer.

Vanadium(IV) and copper(II) complexes of salicylaldimines and aromatic heterocycles: Cytotoxicity, DNA binding and DNA cleavage properties

Five copper(II) complexes, [Cu(sal-Gly)(bipy)](1), [Cu(sal-Gly)(phen)] (2), [Cu(sal-l-Ala)(phen)] (3), [Cu(sal-D-Ala)(phen)] (4), [Cu(sal-l-Phe)(phen)] (5) and five oxidovanadium(IV) complexes, [V(IV)O(sal-Gly)(bipy)] (6), [V(IV)O(sal-Gly)(phen)] (7), [V(IV)O(sal-l-Phe)(H2O)] (8), [V(IV)O(sal-l-Phe)(bipy)] (9), [V(IV)O(sal-l-Phe)(phen)] (10) (sal=salicylaldehyde, bipy=2,2'-bipyridine, phen=1,10-phenanthroline) were synthesized and characterized, and their interaction with DNA was evaluated by different techniques: gel electrophoresis, fluorescence, UV-visible and circular dichroism spectroscopy. The complexes interact with calf-thymus DNA and efficiently cleave plasmid DNA in the absence (only 2 and 5) and/or presence of additives. The cleavage ability is concentration-dependent as well as metal and ligand-dependent. Moreover, DNA binding experiments show that the phen-containing Cu(II) and V(IV)O compounds display stronger DNA interaction ability than the corresponding bipy analogues. The complexes present cytotoxic activity against human ovarian (A2780) and breast (MCF7) carcinoma cells. Cell-growth inhibition (IC50) of compounds 1, 2 and 5 in human promyelocytic leukemia (HL60) and human cervical cancer (HeLa) cells were also determined. The copper complexes show much higher cytotoxic activity than the corresponding vanadium complexes and the reference drug cisplatin (except for the sal-Gly complexes); namely, the phenanthroline copper complexes 2-5 are ca. 10-fold more cytotoxic than cisplatin and more cytotoxic than their bipyridine analogues.

A family of ligand and anion dependent structurally diverse Cu(ii) Schiff-base complexes and their catalytic efficacy in an O-arylation reaction in ethanolic media

Catalytic O-arylation reactions have been studied by employing a variety of copper(ii) Schiff-base complexes under environmentally benign conditions.

Synthesis of mononuclear copper(II) complexes of acyclic Schiff's base ligands: spectral, structural, electrochemical, antibacterial, DNA binding and cleavage activity

The mononuclear copper(II) complexes (1&2) of ligands L(1) [N,N'-bis(2-hydroxy-5-methylbenzyl)-1,4-bis(3-iminopropyl)piperazine] or L(2) [N,N'-bis(2-hydroxy-5-bromobenzyl)-1,4-bis(3-iminopropyl) piperazine] have been synthesized and characterised. The single crystal X-ray study had shown that ligands L(1) and L(2) crystallize in a monoclinic crystal system with P21/c space group. The mononuclear copper(II) complexes show one quasireversible cyclic voltammetric response near cathodic region (-0.77 to -0.85 V) in DMF assignable to the Cu(II)/Cu(I) couple. Binding interaction of the complexes with calf thymus DNA (CT DNA) investigated by absorption studies and fluorescence spectral studies show good binding affinity to CT DNA, which imply both the copper(II) complexes can strongly interact with DNA efficiently. The copper(II) complexes showed efficient oxidative cleavage of plasmid pBR322 DNA in the presence of 3-mercaptopropionic acid as reducing agent through a mechanistic pathway involving formation of singlet oxygen as the reactive species. The Schiff bases and their Cu(II) complexes have been screened for antibacterial activities which indicates that the complexes exhibited higher antimicrobial activity than the free ligands.

Multinuclear ruthenium(ii) complexes as anticancer agents

The dinuclear ruthenium complex with X = H is four-times more cytotoxic than cisplatin against breast cancer cell lines; however, when X = NO₂ the ruthenium complex is less active than cisplatin.