Ni(II) and Cu(II) complexes with ONNO asymmetric tetradentate Schiff base ligand: synthesis, spectroscopic characterization, theoretical calculations, DNA interaction and antimicrobial studies

Design, synthesis, characterization, in vitro cytotoxic, antimicrobial, antioxidant studies, DFT, thermal and molecular docking evaluation of biocompatible Co(II) complexes of N4O4-macrocyclic ligands

Bioactive cobalt (II) macrocyclic complexes [Co(N4O4ML1)Cl2]-[Co(N4O4ML3)Cl2] have been synthesized by using the macrocyclic ligands [N4O4ML1], [N4O4ML2], and [N4O4ML3] that have an N4O4 core. These three macrocyclic ligands were all isolated in pure form, together with their complexes. Microanalytical investigations, FT-IR NMR, Mass, magnetic moments, electronic, PXRD, TGA, and EPR spectrum studies were used to analyse their structures. For these complexes, an octahedral geometry is proposed for the metal ion. By using molecular weights and conductivity measurements the monomeric and non-electrolytic nature has been confirmed. The Coats-Redfern and FWO methods are used to determine the thermodynamic characteristics of the ligands and their Co(II) complexes. The molecular modelling using the DFT technique displays the bond angle, bond lengths and quantum chemical properties. To determine their ability to prevent the growth of harmful fungus and bacteria, the ligands [N4O4ML1]- [N4O4ML3] and their complexes were tested in vitro against A. Niger, C. albicans and B. subtilis, S. aureus, E. coli and S. typhi fungal and bacterial organisms, respectively. By using DPPH free radical scavenger assays, the in vitro antioxidant capabilities of each compound were evaluated. The [Co(N4O4ML3)Cl2] antioxidative capabilities revealed significant radical scavenging power. The MTT assay was used to assess the toxicity of all the synthesised compounds under inquiry on MCF-7, HeLa, and A549 cancer cells. The findings revealed that the ligand and the compounds gave outstanding IC50 values in the range of 9.07-36.25 (uM) at a concentration of 25 ppm. Among all the substances evaluated, [Co(N4O4ML3)Cl2] complex was discovered to be the most active and least cytotoxic. Additionally, docking investigations of the produced compounds were carried out in order to validate the biological outcomes.

Effect of Cu(II) compound containing dipicolinic acid on DNA damage: a study of antiproliferative activity and DNA interaction properties by spectroscopic, molecular docking and molecular dynamics approaches

A polymeric compound formulized as [Cu(µ-dipic)2{Na2(µ-H2O)4]n.2nH2O (I), where dipic is 2,6-pyridine dicarboxylic acid (dipicolinic acid, H2dipic), was synthesized by sonochemical irradiation. The initial in-vitro cytotoxic activity of this complex compared with renowned anticancer drugs like cisplatin, versus HCT116 colon cell lines, shows promising results. This study investigated the interaction mode between compound (I) and calf-thymus DNA utilizing a range of analytical techniques including spectrophotometry, fluorimetry, partition coefficient analysis, viscometry, gel electrophoresis and molecular docking technique. The results obtained from experimental methods reveal complex (I) could bind to CT-DNA via hydrogen bonding and van der Waals forces and the theoretical methods support it. Also, complex (I) indicates nuclease activity in the attendance of H2O2 and can act as an artificial nuclease to cleave DNA with high efficiency.Communicated by Ramaswamy H. Sarma.

Syntheses and characterization of novel antimony (III) and bismuth (III) derivatives containing β-enamino ester along with antimicrobial evaluation, DFT calculation, and cytotoxic study

Four novel antimony (III) and bismuth(III) complexes of the kind Cl-Sb-O-C(OR)-CH(CH3 )C-NH-(CH2 )2 -NH-C(CH3 )CH:C(OR)-O [where R = -CH3 , M = Sb (1a); R = -C2 H5 , M = Sb (1b); R = -CH3, M = Bi (1c); R = -C2 H5 , M = Bi (1d)] were successfully prepared by reacting antimony(III)chloride and bismuth(III)chloride with sodium salt of β-enamino esters in 1:1 stoichiometry, which were further structurally characterized by physicochemical and IR, 1 H, 13 C NMR spectral and mass spectrometry. Structural analysis revealed that all four derivatives of both antimony and bismuth display octahedarl geometry which has been optimized through computational studies. These derivatives along with their parent ligands were subsequently assayed in vitro for antibacterial (Bacillus subtilis, Pseudomonas aeruginosa) and antifungal (Aspergillus niger and Candida albicans) activities. Synthesized complexes were more efficacious in terms of biological activities as compared to parent ligands Further synthesized compounds were evaluated for their in vitro cytotoxic activity against lung cancer cell line A549 using MTT method. IC50 value for all four complexes was determined and all of them are found active. Computational studies of the representative complexes have been done using B3LYP/631-G* basis sets to provide optimized geometry.

Development of New Azomethine Metal Chelates Derived from Isatin: DFT and Pharmaceutical Studies

Through the condensation of isatin (indoline-2, 3-dione) and aniline in a 1:1 ratio, a Schiff base ligand was synthesized and characterized via (¹H-NMR, mass, IR, UV-Vis) spectra. Elemental analyses, spectroscopy (¹H-NMR, mass, UV-Vis), magnetic susceptibility, molar conductivity, mass spectra, scanning electron microscope (SEM), and thermal analysis have all been used to characterize a series of Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II), and Cd(II) metal complexes derived from the titled ligand. The metal-to-ligand ratio is 1:1, according to the analytical data. The Schiff base ligand displayed bidentate behavior with NO coordination sites when it bonded to metal ions, as seen by the IR spectra. The magnetic moment measurement and UV-Vis spectral investigation showed the octahedral geometry of the Cr(III), Fe(III), Co(II), Ni(II), and Zn(II) complexes, whereas they suggested the tetrahedral geometry of the Mn(II), Cu(II), and Cd(II) complexes. The thermal analysis study confirmed the presence of both hydrated and coordinated water molecules in all the compounds, except for the Mn(II) complex, and showed that the complexes decomposed in three or five decomposition steps leaving the corresponding metal oxide as a residue. The ligand and its metal complexes' antibacterial efficacy were evaluated. The findings showed that the metal complexes had stronger antibacterial properties than the ligand alone. The ligand and its metal complexes' anticancer properties were also investigated. A DFT investigation is also reported to gather information regarding the electronic features of the ligand and its metal complexes. Finally, drug-likeness and ADME characteristics were also calculated as parameters.

Synthesis and characterization of the new ligand, 1,2,4-triazino[5,6-b]indol-3-ylimino methyl naphthalene-2-ol and its Ni(II) and Cu(II) complexes: comparative studies of their in vitro DNA and HSA Binding

A new ligand 1,2,4-triazino[5,6-b]indol-3-ylimino methyl naphthalene-2-ol (HL) was derived from 5H-[1,2,4]triazino[5,6-b]indol-3-amine and 2-hydroxy-1-naphthaldehyde. The metal complexes of the type [Ni(L)(Bipy)]1/2SO₄ (1), [Cu(L)(Bipy)(H₂O)₂]1/2SO₄ (2), [Ni(L)(Phen)]1/2SO₄ (3) and [Cu(L)(Phen)(H₂O)₂]1/2SO₄ (4) were synthesized. The ligand (HL) and complexes 1-4 were thoroughly characterized by elemental analysis and spectroscopic methods (FT-IR, ToF-MS, ¹H NMR, ¹³C NMR), molar conductance and magnetic moment determination. The Ni(II) complexes 1 and 3 adopt the square planar geometry and Cu(II) complexes 2 and 4 acquire distorted octahedral arrangement. In vitro DNA binding behavior of ligand (HL) and metal complexes 1-4 was explored by fluorescence spectral and ethidium bromide studies. The outcomes reveal that the complexes interact with DNA via non-covalent groove binding and electrostatic interactions. The higher binding constant (K) values of 4.35 × 10⁴ and 9.12 × 10⁴ M^-1 for complexes 2 and 4 indicate stronger binding ability with DNA. Moreover, in vitro human serum albumin (HSA) binding experiment with HL and complexes 1-4 reveals conformational modulations in the Trp-214 microenvironments in the subdomain IIA pocket.

Design, Structural Inspection and Bio-Medicinal Applications of Some Novel Imine Metal Complexes Based on Acetylferrocene

Some novel imine metal chelates with Cr³⁺, Mn²⁺, Fe³⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, and Cd²⁺ cations were produced from 2-acetylferrocene and 3-aminophenol. The new acetylferrocene azomethine ligand ((Z)-cyclopenta-1,3-dien-1-yl(2-(1-((3-hydroxyphenyl)imino)ethyl)cyclopenta-2,4-dien-1-yl)iron) and its metal ion chelates were constructed and elucidated using FT-IR, UV/Vis, ¹HNMR, DTA/TGA, CHNClM studies, mass spectrometry and SEM analysis. According to the TGA/DTG investigation, the ferrocene moiety spontaneously disintegrates to liberate FeO. The morphology of the free acetylferrocene azomethine via SEM analysis was net-shaped with a size of 64.73 nm, which differed in Cd(II) complex to be a spongy shape with a size of 42.43 nm. The quantum chemical features of the azomethine ligand (HL) were computed, and its electronic and molecular structure was refined theoretically. The investigated acetylferrocene imine ligand behaves as bidinetate ligand towards the cations under study to form octahedral geometries in case of all complexes except in case of Zn²⁺ is tetrahedral. Various microorganisms were used to investigate the anti-pathogenic effects of the free acetylferrocene azomethine ligand and its metal chelates. Moreover, the prepared ligand and its metal complexes were tested for anticancer activity utilizing four different concentrations against the human breast cancer cell line (MCF7) and the normal melanocyte cell line (HBF4). Furthermore, the binding of 3-aminophenol, 2-acetylferrocene, HL, Mn²⁺, Cu²⁺, and Cd²⁺ metal chelates to the receptor of breast cancer mutant oxidoreductase was discovered using molecular docking (PDB ID: 3HB5).

Fabrication, DFT Calculation, and Molecular Docking of Two Fe(III) Imine Chelates as Anti-COVID-19 and Pharmaceutical Drug Candidate

Two tetradentate dibasic chelating Schiff base iron (III) chelates were prepared from the reaction of 2,2′-((1E,1′E)-(1,2-phenylenebis(azanylylidene))bis(methanylylidene))bis(4-bromophenol) (PDBS) and 2,2′-((1E,1′E)-((4-chloro-1,2-phenylene)bis(azanylylidene))-bis(methanylylidene))bis(4-bromophenol) (CPBS) with Fe³⁺ ions. The prepared complexes were fully characterized with spectral and physicochemical tools such as IR, NMR, CHN analysis, TGA, UV-visible spectra, and magnetic moment measurements. Moreover, geometry optimizations for the synthesized ligands and complexes were conducted using the Gaussian09 program through the DFT approach, to find the best structures and key parameters. The prepared compounds were tested as antimicrobial agents against selected strains of bacteria and fungi. The results suggests that the CPBSFe complex has the highest activity, which is close to the reference. An MTT assay was used to screen the newly synthesized compounds against a variety of cell lines, including colon cancer cells, hepatic cellular carcinoma cells, and breast carcinoma cells. The results are expressed by IC50 value, in which the 48 µg/mL value of the CPBSFe complex indicates its success as a potential anticancer agent. The antioxidant behavior of the two imine chelates was studied by DPPH assay. All the tested imine complexes show potent antioxidant activity compared to the standard Vitamin C. Furthermore, the in vitro assay and the mechanism of binding and interaction efficiency of the tested samples with the receptor of COVID-19 core protease viral protein (PDB ID: 6lu7) and the receptor of Gram-negative bacteria (Escherichia coli, PDB ID: 1fj4) were investigated using molecular docking experiments.

Exploring the charge transfer dynamics of hydrogen bonded crystals of 2-methyl-8-quinolinol and chloranilic acid: synthesis, spectrophotometric, single-crystal, DFT/PCM analysis, antimicrobial, and DNA binding studies

The new chemistry of the hydrogen-bonded charge and proton transfer complex (HB CT) between electron-donor 2-methyl-8-quinolinol (2 MQ) and electron-acceptor chloranilic acid (CHLA) has been studied using electronic absorption spectroscopy in acetonitrile (ACN), methanol (MeOH), and ethanol (EtOH) polar media at room temperature. The stoichiometric proportion of the HB CT complex was observed to be 1 : 1 from the Job data and photometric titration process. The association constant (K CT) and molar absorptivity (ε CT) of the HB CT complex were determined by using the modified Benesi-Hildebrand equation in three polarities. Other spectroscopic physical parameters like the energy of interaction (E CT), ionization potential (I D), resonance energy (R N), standard free energy change (ΔG°), oscillator strength (f), and transition dipole moment (μ) were also evaluated. The HB CT complex structure was confirmed by different characterization techniques, such as FT-IR, NMR, TGA-DTA, and SEM-EDX analysis. Powder XRD and single-crystal XRD were used to determine the nature and structure of the synthesized HB CT complex. DNA binding studies for the HB CT complex produced a good binding constant value of 2.25 × 104 L mol-1 in UV-visible and 1.17 × 104 L mol-1 in fluorescence spectroscopy. The biological activity of the HB CT complex was also tested in vitro against the growth of bacteria and fungi, and the results indicated remarkable activity for the HB CT complex compared to the standard drugs, ampicillin and clindamycin. Hence, the abovementioned biological results of the synthesized HB CT complex show it could be used as a pharmaceutical drug in the future. Computational analysis was carried out by DFT studies using the B3LYP function with a basis set of 6-31G(d,p) in the gas phase and PCM analysis. The computational studies further supported the experimental results by confirming the charge and proton transfer complex.

Temperature and salt effects of the kinetic reactions of substituted 2-pyridylmethylene-8-quinolyl iron (II) complexes as antimicrobial, anti-cancer, and antioxidant agents with cyanide ions

Kinetics of substitution reaction of three high-spin pyridylmethylene-8-quinolyl iron (II) complexes by CN– ions were studied spectrophotometrically in various ratios of aqueous–methanol binary mixtures at 298 ± 0.2 K. Kinetics of the substitution reaction follow the rate law (k2[CN−][complex]) on applying of the conditions of the pseudo first order reaction. Reactivity of the reaction was investigated in terms of ligand moiety and solvent effects. The rate of the reaction increased as the co-solvent methanol ratio increased. This reactivity trend is predominantly due to increases in the activity coefficient of those hydrophobic complexes in the organic methanol co-solvent, depending upon the hydrophobicity of the substituent groups (R) in the coordinated ligand in the complexes. Reactivity trends of the prepared complexes in the presence of the inserted hydrophobic salts such as tetrabutylammonium bromide (TBAB), tetraethylammonium bromide (TEAB), and tetramethylammonium bromide (TMAB) or hydrophilic salt potassium bromide (KBr) were studied. The observed decrease in the rate constants with increasing salt concentration was due to the cationic character of the reacting complexes. In addition, the synthesized compounds were tested for antimicrobial activity against selected strains of microbes. The results showed that the order of reactivity of the investigated complexes against the selected microbes were as follows: ppaqFe > paaqFe > pmaqFe. In addition, the investigated ligands and their Fe(II) complexes were screened for anticancer activities against several cell lines of cancer. The ppaqFe complex showed the best cytotoxic efficiency against the selected cancer lines (IC50 = 8.75–21.50 µg/µl), whereas the pmaq ligand showed the lowest cytotoxic efficiency (IC50 = 58.25– 72.40). Furthermore, the antioxidant potential of the presented compounds was studied by applying DPPH assays and showed a potential activity compared with standard vitamin C. The excellent antimicrobial and anticancer activities of the investigated Fe(II) chelates compared with literature values are promising and deserve further study.

Development of New Thiazole Complexes as Powerful Catalysts for Synthesis of Pyrazole-4-Carbonitrile Derivatives under Ultrasonic Irradiation Condition Supported by DFT Studies

In this study, we are interested in preparing Fe(III), Pd(II), and Cu(II) complexes from new thiazole derivatives. All syntheses were elaborately elucidated to estimate their molecular and structural formulae, which agreed with those of mononuclear complexes. The square-planer geometry of Pd(II) complex (MATYPd) was the starting point for its use as a heterocatalyst in preparing pyrazole-4-carbonitrile derivatives 4a-o using ultrasonic irradiation through a facile one-pot reaction. The simple operation, short-time reaction (20 min), and high efficiency (97%) were the special advantages of this protocol. Furthermore, this green synthesis strategy was advanced by examination of the reusability of the catalyst in four consecutive cycles without significant loss of catalytic activity. The new synthesis strategy presented remarkable advantages in terms of safety, simplicity, stability, mild conditions, short reaction time, excellent yields, and use of a H₂O solvent. This catalytic protocol was confirmed by the density functional theory (DFT) study, which reflected the specific characteristics of such a complex. Logical mechanisms have been suggested for the successfully exerted essential physical parameters that confirmed the superiority of the Pd(II) complex in the catalytic role. Optical band gap, electrophilicity, and electronegativity features, which are essential parameters for the catalytic behavior of the Pd(II) complex, are based mainly on the unsaturated valence shell of Pd(II).

Synthesis and theoretical calculations of metal-antibiotic chelation with thiamphenicol: in vitro DNA and HSA binding, molecular docking, and cytotoxicity studies

New metal complexes showed the magic of the bivalent metal which have higher bioactivity than free ligand.

Synthesis, structural characterization, and biological studies of ATBS-M complexes (M(II) = Cu, Co, Ni, and Mn): Access for promising antibiotics and anticancer agents

A new bidentate Schiff base ligand (ATBS [4-bromo-2-(thiazole-2-yliminomethyl)phenol]) was synthesized via the condensation reaction of 2-aminothiazole with 5-bromosalicylaldehyde in ethanol. The reaction of ATBS with transition metal salts of Cu(II), Co(II), Ni(II), and Mn(II) afforded the corresponding ATBS-M complexes. Results from physicochemical and spectral analyses, such as elemental analysis, infrared, UV-Vis spectroscopy, magnetic susceptibility, and molar conductance, revealed a nonelectrolytic nature with octahedral (O_h ) geometry and a metal/ligand ratio of 1:2 for Cu(II), Co(II), and Ni(II), but 1:1 for the Mn(II) complex. The density functional theory (DFT) calculations are correlated very well with the proposed structure and molecular geometry of the complexes as [M(ATBS)₂ ] (M = Cu, Co, and Ni) and [Mn(ATBS)(H₂ O)₂ ]. Significantly, the prepared compounds showed strong inhibition activity for a wide spectrum of bacteria (Escherichia coli, Bacillus subtilis, and Staphylococcus aureus) and fungi (Candida albicans, Aspergillus flavus, and Trichophyton rubrum), with the ATBS-Ni complex being the most promising antibiotic agent. Molecular docking studies of the binding interaction between the title complexes with the bacterial protein receptor CYP51 revealed clear insights about the inhibition nature against the studied microorganisms, with the following order: ATBS-Cu > ATBS-Mn > ATBS-Ni > ATBS-Co for complex stability. Moreover, the cytotoxicity measurements of all prepared metal complexes against the colon carcinoma (HCT-116) and hepatocellular carcinoma (Hep-G2) cell lines showed exceptional anticancer efficacy of the complexes as compared with the free ATBS Schiff base ligand. Significantly, the results attested that ATBS-Cu is the most effective complex against HCT-116 cells, whereas ATBS-Mn has the highest cytotoxic efficiency against Hep-G2 cells. Furthermore, electronic spectra, viscosity measurements, and gel electrophoresis techniques were employed to probe the interaction of all prepared ATBS-metal complexes with calf thymus (CT)-DNA. Results confirmed that all complexes are strongly bound to CT-DNA via intercalation mode, with the ATBS-Co complex having the highest binding ability.

Non-Linear Optical Property and Biological Assays of Therapeutic Potentials Under In Vitro Conditions of Pd(II), Ag(I) and Cu(II) Complexes of 5-Diethyl amino-2-({2-[(2-hydroxy-Benzylidene)-amino]-phenylimino}-methyl)-phenol

Herein, we report facile procedures for synthesis of a new Schiff base ligand (H₂L,5-Diethylamino-2-({2-[(2-hydroxy-benzylidene)-amino]-phenylimino}-methyl)-phenol) and its Ag(I), Pd(II) and Cu(II) complexes. The structure of the H₂L ligand as well as its metal complexes was deduced based on wide range of analytical, structural and spectroscopic tools, along with theoretical evidence via density functional theory (DFT) calculations. The obtained results indicated that the Schiff base (H₂L) ligand acts as a tetradentate N₂O₂ donor with two azomethine nitrogen’s (N1, N2) and two deprotonated phenolic oxygens (O1, O2) atoms. A distorted octahedral structure is assigned to [CuL(OH₂)₂]·3/2H₂O complex and square planar structure for PdL and AgL complexes. The electronic structure and non-linear optical (NLO) property of the prepared compounds were discussed theoretically by the B3LYP/GENECP program. Results revealed that all complexes have non-planner geometries as indicated from the dihedral angles. The charge transfer occurs within the synthesized complexes as indicated from the calculated energy gap between HOMO and LUMO energies. The H₂L ligand and its complexes are excellent candidates for NLO materials as implied from their hyperpolarizabilities and polarizabilities values. The biological activities of the prepared complexes against selected microorganisms and cancer cell lines gave good growth inhibitory effect. The biocidal potencies of the ligand and its complexes can be arranged as follows: AgL > CuL > PdL > H₂L, as compared to the used standard drugs. The antiproliferative activity of the studied complexes against different carcinoma cell lines such as liver (Hep-G2), breast (MCF-7) and colon (HCT-116) followed the order H₂L < AgL< PdL < CuL < vinblastine. Probing the binding interactions of prepared complexes with calf thymus (CT)-DNA using electronic absorption, gel electrophoresis and viscosity measurements revealed strong interaction via intercalation modes, as also evidenced by their molecular docking study.

Synthesis and characterization of new Cr(III), Fe(III) and Cu(II) complexes incorporating multi-substituted aryl imidazole ligand: Structural, DFT, DNA binding, and biological implications

Designing new metal-based molecular antibiotics is an efficient approach to overcome the growing threat of antimicrobial resistance. In this paper, novel Cr(III), Fe(III) and Cu(II) complexes comprising substituted aryl imidazole ligand (MSEB), namely (2-(1-(2-hydroxyethyl)-4,5-diphenyl-1H-imidazole-2-yl)(4-bromophenol)) have been synthesized and characterized using infra-red (IR), ultraviolet-visible (UV-Vis) and ¹H, ¹³C NMR spectroscopic techniques, together with elemental (CHN) and thermogravimetric analyses, molar conductance, and magnetic susceptibility measurements. The combined results along with the DFT calculations revealed a 1:1 (M: L) stoichiometric ratio and the complexes adopted distorted-octahedral geometries to afford [Cr(MSEB)Cl₂(H₂O)₂], [Fe(MSEB)(NO₃)₂(H₂O)₂] and [Cu(MSEB)Cl(H₂O)₃] respectively. Biological studies showed that all complexes exhibited powerful antimicrobial activity against various strains of bacteria and fungi, S. aureus (+ve), E. coli (-ve) and P. aeruginosa (-ve) bacteria and T. Rubrum, C. albicans, and A. flavus fungi. Moreover, the three metal-complexes showed high in vitro cytotoxicity against Colon (HCT-116), Breast (MCF-7), and hepatic cellular (HepG-2) carcinoma cell lines, with MSEBCu complex being the most cytotoxic one. Finally the binding interactions of the complexes with CT-DNA were explored using UV-Vis spectroscopy, viscosity and gel electrophoreses measurements.