Free Ligand Research Articles

Biological function of sulfapyridine derivatives and their manganese(II) complexes

Three derivatives of Schiff bases, 6-chloro-chromensulfapyridine (CCSP), indol-3-sulfapyridine (ISP), and 5-chlorothiophen-2-sulfapyridine (CTSP), were synthesized and characterized by analytical, spectroscopic (IR, UV-Vis., 1H and 13C NMR, Mass, EPR), and electrochemical techniques. Antioxidant capabilities were recorded for both ligands and their Mn(II) complexes using DPPH scavenger and ascorbic acid as a reference. Compared with free ligands, the Mn(II) complexes exhibit greater antioxidant activity. In-vitro antibacterial and antifungal studies were performed by well diffusion technique. Results obtained from IC 50 value suggest that (CTCSP)2Mn (IC 50 = 210.8 μg/mL) has potent antimicrobials. In addition, in silico drug-likeness, absorption, distribution, metabolism, and excretion (ADME) properties were examined for the ligands and complexes.

Synthesis, characterizations, antitumor and antimicrobial evaluations of novel Mn(II) and Cu(II) complexes with NNN-tridentate s-Triazine-Schiff base ligand

The new s-triazine hydrazone, 2,4-bis(morpholin-4-yl)-6-[(E)-2-[1-(pyridin-2-yl)ethylidene]hydrazin-1-yl]-1,3,5-triazine, (L) ligand was used to synthesize three new metal complexes. Single-crystal X-ray diffraction analysis indicated that the [MnLCl2] (1) and [CuLCl2].H2O (2) complexes exhibit distorted trigonal bipyramidal coordination geometry with one NNN-tridentate ligand L and two chloride ions. The trigonality index (τ5) was calculated to be 0.332 and 0.235 Ǻ for complexes 1 and 2, respectively. In case of the [CuL(NO3)2] complex (3), the Cu(II) ion is hexa-coordinated with one NNN-tridentate ligand L, one bidentate nitrate and one monodentate nitrate. The supramolecular structure of complexes 1 and 3 was analyzed using Hirshfeld calculations; hydrogen bonding-based interactions have the largest contribution in their molecular packing. The anticancer and antimicrobial activities of the ligand and its complexes (1–3) were examined. The three complexes have higher anticancer activity against colon HCT-116 and lung A-549 cancer cell lines than the free ligand (L). The only exception is complex 1 which has less cytotoxic activity against lung A-549 cancer cell line than L. Interestingly, the Cu(II) complexes have higher cytotoxic activity than the Mn(II) complex, where complex 3 has the best anticancer activity against HCT-116 (IC50 = 7.78 ± 0.27 μg/mL) and A-549 (12.40 ± 0.54 μg/mL) cell lines. In addition, the three complexes showed greater activity against gram-positive bacteria (S. aureus and B. subtilis) than gram-negative bacteria (E. coli and P. vulgaris) where 3 has best antibacterial activity.

Assessment of Aptamer as a Potential Drug Targeted Delivery for Retinal Angiogenesis Inhibition.

AT11-L0 is an aptamer derivative of AS1411 composed of G-rich sequences that can adopt a G-quadruplex (G4) structure and target nucleolin (NCL), a protein that acts as a co-receptor for several growth factors. Hence, this study aimed to characterize the AT11-L0 G4 structure and its interaction with several ligands for NCL targeting and to evaluate their capacity to inhibit angiogenesis using an in vitro model. The AT11-L0 aptamer was then used to functionalize drug-associated liposomes to increase the bioavailability of the aptamer-based drug in the formulation. Biophysical studies, such as nuclear magnetic resonance, circular dichroism, and fluorescence titrations, were performed to characterize the liposomes functionalized with the AT11-L0 aptamer. Finally, these liposome formulations with the encapsulated drugs were tested on the human umbilical vein endothelial cell (HUVEC) model to assess their antiangiogenic capacity. The results showed that the AT11-L0 aptamer-ligand complexes are highly stable, presenting melting temperatures from 45 °C to 60 °C, allowing for efficient targeting of NCL with a KD in the order of nM. The aptamer-functionalized liposomes loaded with ligands C8 and dexamethasone did not show cytotoxic effects in HUVEC cells compared with the free ligands and AT11-L0, as assessed by cell viability assays. AT11-L0 aptamer-functionalized liposomes encapsulating C8 and dexamethasone did not present a significant reduction in the angiogenic process when compared with the free ligands. In addition, AT11-L0 did not show anti-angiogenic effects at the concentrations tested. However, C8 shows potential as an angiogenesis inhibitor, which should be further developed and optimized in future experiments.

Anion Coordination into Ligand Clefts

A tripodal anion receptor has been obtained by an easy and fast single-reaction synthesis from commercial reagents. The three ligand arms-bearing aromatic groups able to form anion–π interactions define ligand clefts where large anions, such as perchlorate and perrhenate, are included. We report here the synthesis of the ligand, its acid/base properties in an aqueous solution which has been used to direct the synthesis of anion complexes, and the crystal structure of the free ligand and its anion complexes H3L(ClO4)2·H2O and H3L(ReO4)2.

Dynamic Interconversion and Induced-Fit Guest Binding with Two Macrocycle-Based Coordination Cages.

We report the syntheses and host-guest chemistry of two interconvertible coordination cages, Pd2L2 and Pd1L1, from a dynamic macrocycle ligand (L) and a cis-blocking (tmen)Pd(NO3)2 (tmen = tetramethylethylenediamine) unit (Pd). The water-soluble macrocyclic L, which can bind various polycyclic aromatic hydrocarbon (PAH) guests in its cis-conformation, was constructed via four pyridinium bonds between two 2,4,6-tri(4-pyridyl)-1,3,5-triazine [TPT] panels and two p-xylene bridges. We selectively formed each cage either by changing the reaction concentration/solvent/temperature or through induced-fit guest encapsulation, while direct assembly of L and Pd resulted in a mixture of Pd2L2 and Pd1L1 in equilibrium. X-ray structures of the free ligand and the host-guest complexes confirmed the induce-fit adaptive changes in the ligand's conformation and the cage's cavity. This work demonstrates a useful strategy for designing multistimuli-responsive supramolecular hosts by coordination self-assembly with macrocyclic ligands featuring rich conformational freedom.

Design of rigid protein–protein interaction inhibitors enables targeting of undruggable Mcl-1

The structure-based design of small-molecule inhibitors targeting protein-protein interactions (PPIs) remains a huge challenge as the drug must bind typically wide and shallow protein sites. A PPI target of high interest for hematological cancer therapy is myeloid cell leukemia 1 (Mcl-1), a prosurvival guardian protein from the Bcl-2 family. Despite being previously considered undruggable, seven small-molecule Mcl-1 inhibitors have recently entered clinical trials.Here, we report the crystal structure of the clinical-stage inhibitor AMG-176 bound to Mcl-1 and analyze its interaction along with clinical inhibitors AZD5991 and S64315. Our X-ray data reveal high plasticity of Mcl-1 and aremarkable ligand-induced pocket deepening. Nuclear Magnetic Resonance (NMR)-based free ligand conformer analysis demonstrates that such unprecedented induced fit is uniquely achieved by designing highly rigid inhibitors, preorganized in their bioactive conformation. By elucidating key chemistry design principles, this work provides a roadmap for targeting the largely untapped PPI class more successfully.

Cytotoxic behavior and DNA/BSA binding activity of thiosemicarbazone based Ni(II) complex: bio-physical, molecular docking and DFT study

The bidentate ligand thiosemicarbazone (H3L) and its Ni(II) complex were synthesized and characterized by single crystal X-ray diffraction and various spectroscopic methods. The Ni(II) complex exhibits almost square planar geometry around the nickel ion, coordinated by two ligands through N & S donor centers. The important structural features of single crystal of the complex are [space group: P-1; a = 11.0594(9) Ǻ; b = 12.2339(9) Ǻ; c = 14.8835(9) Ǻ; α = 110.857(6); β = 91.029(6) and γ = 108.710(7)]. The DFT/TD-DFT simulations have been performed to determine the HOMO-LUMO energy, electronic spectroscopy data, the minimum energy optimized structure and to calculate the reactivity descriptors of the compounds using the B3LYP level of theory. The DFT and NBO analysis based on theoretical investigation helps to locate the MEP surface and bonding mode of the ligand in complex respectively. Different reactivity descriptors establish a correlate between their reactivity and bio-molecular affinity of the molecules. The binding abilities of the compounds with DNA and BSA were within the order of standard DNA and BSA binders. The bio-molecular conformational change as well as interactions of the compounds were monitored by biophysical analyses like; 3D fluorescence, FRET calculations and anisotropy studies with BSA. The potent drug likeness antineoplastic and bio-activity of the H3L and Ni(II) complex were assessed using online software PASS and ADMET. The antiproliferative activity of the compounds was evaluated against the normal human embryonic kidney (HEK293) cells and the human breast carcinoma (MCF-7) cancer cell line. The Annexin V-FITC, Propidium iodide assay in the presence of the free ligand H3L and its Ni(II) complex were performed using flow cytometric method for their cell death mechanisms. Reactive Oxygen Species (ROS) production assay using 2′,7′-Dichlorodihydrofluorescein diacetate (DCFDA) was evaluated in presence of the compounds.

Synthesis, spectroscopic characterization, molecular studies, and biological evaluation of (E)-N'-((7-methyl-2-oxo-1,2-dihydroquinolin-3-yl)methylene)morpholine-4-carbothiohydrazide and some of its transition metal complexes

Novel Ni(II), Cu(II), Zn(II), Cd(II), and Pd(II) complexes (1–6) with (E)-N'-((7-methyl-2-oxo-1,2-dihydroquinolin-3-yl)methylene)morpholine-4-carbothiohydrazide ligand (HL) were prepared and characterized via different analytical and spectroscopic techniques. The spectral data showed that the ligand is bound with copper(II) chloride, zinc(II) chloride, cadmium(II) chloride, and potassium tetrachloropalladate(II) in its neutral thione form in complexes 2, 4, 5, and 6, respectively. Furthermore, the ligand was coordinated with nickel (II) chloride and copper(II) acetate in complexes 1 and 3 as a monobasic tridentate in its thiol form. Thermogravimetric studies were performed for the prepared compounds and the pyrolytic mechanism was proposed for some complexes. DFT, TD-DFT, and NBO calculations were achieved at the B3LYP/LanL2DZ level of theory. Computational studies showed that the investigated compounds have high hyperpolarizability values (β) suggesting their potential use in the creation of non-linear optical materials. Many bacterial and fungal strains were used to assess the ligand and its metal complexes' antibacterial activities. In general, metal complexes have been shown to possess a stronger antibacterial and antifungal effect thanthe free ligand. Complex 5 exhibited respectable antibacterial activity versus Gram-positive bacteria. Furthermore, Zn(II) and Cd(II), complexes 4 and 5 have shown excellent activity against Gram-negative bacteria. Complex 4 exhibited a superior antifungal activity against two types of tested fungi compared with other compounds and standard Ketoconazole. Molecular docking of the ligand and its complexes 1, 2, and 5 were performed against tyrosyl-tRNA synthetase. The more negative values of the binding energy indicate that complexes 1 and 5 have higher inhibition efficiency than the free ligand.

Chemical speciation of caffeic and p-coumaric acids with selected lanthanides

Caffeic (CFA) and p-coumaric (p-CA) acids are biologically active compounds commonly found in plants and food of plant origin. Metal complexes of these acids exhibit diverse bioactivity, sometimes even higher than the free ligands. Lanthanide (Ln) complexes with organic ligands also attract the attention of researchers, due to their potential application as novel potential biologically active agents. The aim of the present study was the evaluation of the interactions of CFA and p-CA with representative lanthanides (Ln3+ = Eu3+, Gd3+, and Dy3+) in aqueous solution. Potentiometric, spectrophotometric, and 1H NMR techniques were used to study the acid-base behavior of CFA and p-CA, as well as their complexing ability towards Ln3+ cations, over a wide range of pH values (2 ≤ pH ≤ 8), in KCl(aq) at I = 0.2 mol dm−3 and T = 298.15 ± 0.1 K. The evaluation of the sequestering ability of both ligands towards the studied lanthanides, by means of pM and pL0.5 parameters, show that CFA is a better chelating agent.

Photoluminescent iridium(III) complexes with phenylvinylpyridine-base cyclometalating ligands: Synthesis, photophysical properties, and photocyclization

Photoresponsive materials have recently garnered significant research interest and have been designed using various molecules. A viable approach to develop photoresponsive materials is by integrating photoisomeric structures into the organic ligands of phosphorescent transition metal complexes. In this study, we designed two photoresponsive cyclometalating ligands, 2-phenyl-3-vinylpyridine (HL1) and trans-4-methyl-2-phenyl-3-styrylpyridine (HL2), via the replacement of a phenyl group with a pyridyl group in vinylbiphenyl. Upon photoirradiation under an argon atmosphere, both ligands underwent photocyclization and demonstrated hypochromism and bathochromic shifts in absorption. Notably, HL2 underwent additional oxidative dehydrogenation upon photoirradiation in the presence of oxygen, resulting in an elongated conjugation structure that exhibited significant fluorescence intensity increase at 363 nm. Additionally, three photoresponsive iridium(III) complexes cyclometalated with HL1 or HL2 were synthesized and characterized. The photocyclization process of the complexes was much faster than that of the free ligands because the phenylpyridine moiety became coplanar upon cyclometalation. Upon photoirradiation under an argon atmosphere, these complexes exhibited significant luminescence enhancement by about 10–20 folds because of photocyclization resulting in a rigid closed structure that limited nonradiative decay of the excited complexes. These molecules present a unique strategy to construct photocyclization complexes and provide important insights into the development of photoresponsive materials.

Is Smaller Better? Cu2+/Cu+ Coordination Chemistry and Copper-64 Radiochemical Investigation of a 1,4,7-Triazacyclononane-Based Sulfur-Rich Chelator.

The biologically triggered reduction of Cu2+ to Cu+ has been postulated as a possible in vivo decomplexation pathway in 64/67Cu-based radiopharmaceuticals. In an attempt to hinder this phenomenon, we have previously developed a family of S-containing polyazamacrocycles based on 12-, 13-, or 14-membered tetraaza rings able to stabilize both oxidation states. However, despite the high thermodynamic stability of the resulting Cu2+/+ complexes, a marked [64Cu]Cu2+ release was detected in human serum, likely as a result of the partially saturated coordination sphere around the copper center. In the present work, a new hexadentate macrocyclic ligand, 1,4,7-tris[2-(methylsulfanyl)ethyl)]-1,4,7-triazacyclononane (NO3S), was synthesized by hypothesizing that a smaller macrocyclic backbone could thwart the observed demetalation by fully encapsulating the copper ion. To unveil the role of the S donors in the metal binding, the corresponding alkyl analogue 1,4,7-tris-n-butyl-1,4,7-triazacyclononane (TACN-n-Bu) was considered as comparison. The acid-base properties of the free ligands and the kinetic, thermodynamic, and structural properties of their Cu2+ and Cu+ complexes were investigated in solution and solid (crystal) states through a combination of spectroscopic and electrochemical techniques. The formation of two stable mononuclear species was detected in aqueous solution for both ligands. The pCu2+ value for NO3S at physiological pH was 6 orders of magnitude higher than that computed for TACN-n-Bu, pointing out the significant stabilizing contribution arising from the Cu2+-S interactions. In both the solid state and solution, Cu2+ was fully embedded in the ligand cleft in a hexacoordinated N3S3 environment. Furthermore, NO3S exhibited a remarkable ability to form a stable complex with Cu+ through the involvement of all of the donors in the coordination sphere. Radiolabeling studies evidenced an excellent affinity of NO3S toward [64Cu]Cu2+, as quantitative incorporation was achieved at high apparent molar activity (∼10 MBq/nmol) and under mild conditions (ambient temperature, neutral pH, 10 min reaction time). Human serum stability assays revealed an increased stability of [64Cu][Cu(NO3S)]2+ when compared to the corresponding complexes formed by 12-, 13-, or 14-membered tetraaza rings.

Electrocatalytic and photocatalytic activity of a nickel (II) quinacridone complex

The undesirable influences of hazardous pollutants on the environment and the global demand for using renewable and environmentally clean energy sources necessitate the development of appropriate ways for controlling environmental pollution and also energy challenges. In this research, a square planar Ni (II) complex, [Ni(DMSO)2(QA)2](NO3)2, where QA = quinacridone, was synthesized and characterized. Afterward, the complex was exploited as an electrocatalyst for hydrogen evolution reaction (HER) in acidic media. Linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS) were applied to investigate the electrocatalytic properties of the Ni(II) complex toward the HER process. The overpotential and Tafel slope of the Ni(II) complex are 229 mV at 10 mA cm−2 and 76 mV dec−1, respectively. The Ni(II) complex is favored for its fast HER kinetics, proper durability, and low price. In addition, the Ni (II) complex was used as a photocatalyst in the photodegradation reaction of acridine orange (AO) under visible light at different pH values in H2O. The photocatalytic reaction progress was monitored by UV–Vis spectroscopy. Compared to the free QA ligand, the Ni(II) complex exhibited high efficiency in the photocatalytic reactions, and more than 96% of AO dye was degraded under the optimized conditions at 180 min. A small band gap, efficient light-harvesting capability, easy separation, adequate recyclability, and simple synthesis route make the prepared Ni(II) complex an eco-friendly and efficient photocatalyst for photocatalytic degradation reactions under visible light irradiation.

SYNTHESIS, CHARACTERIZATION OF COPPER(II) COMPLEX WITH TETRADENTATE N2O2 AND POTENTIAL CONTRIBUTION AS PROMISING ANTIBACTERIAL STUDIES

A square planar Schiff base complex, Cu(H2L) namely N,N’-bis(4-methyl-α-salicylidene)propane-1,3-diaminecopper(II) through the condensation reaction of ligand with copper(II) acetate in the molar ratio of 1:1 in acetonitrile solvent was successfully synthesized. The obtained complex was characterized using, elemental analysis of carbon, hydrogen and nitrogen (CHN), Fourier Transform Infrared spectroscopy (FTIR) and electronic spectra of ultraviolet-visible (UV-vis) spectroscopy. FTIR confirmed the coordinates the metal ion to form mononuclear complex via tetradentate (ONNO) atoms of the phenolic group and azomethine group, respectively. The antibacterial studies of H2L and its Cu(H2L) were determined by screening the compounds against selected various Gram (+) and Gram (-) bacterial strains such as Staphylococcus epidermidis, Bacillus subtilis, Staphylococcus aureus, Vibrio cholera, Enterobacter cloacae and Escherichia coli. Indeed, preliminary results exhibited Cu(H2L) more active than the free ligand and displayed promising antibacterial activity, while no effect has been observed on strains for H2L.

Zn(II)-complexes of diisatin dihydrazones as effective catalysts in the oxidation protocol of benzyl alcohol and effective reagents for biological studies

Two new dinuclear complexes of Zn2+ ion (ZnLC2 and ZnLC6, respectively) with two novel diisatin dihydrazone ligands of succinyl (H2LC2) and terephthalyl (H2LC2) derivatives were constructed. Their structure confirmation was achieved by different spectroscopic tools. The catalytic action of two ZnLCX was estimated under an aerobic atmosphere in the selective oxygenation protocol of benzyl alcohol within hydrogen peroxide. ZnLC6 represented more significant action by 88 % awarding of the monooxo-product, i.e. benzaldehyde, (with loaded catalyst amount = 0.005 mmol, at reaction temperature 70 °C for about 3 h), whereas ZnLC2 showed less reactivity with 87 % of the monooxo-product (with the same supplied amount, at 70 °C for 5 h).The biochemical action of H2LCX and ZnLCX was studied spectroscopically with some microbial-series and three human cancer cells. In addition, their biological action was studied through the interacting mode with calf thymus DNA (ctDNA) through viscometric and spectrophotometric assays. Both ZnLCX complexing reagents manifested a regarded inhibiting action versus the titled microbial (bacterial and fungal) series and with three human cancer cells growth (according to the zone values in mm of inhibition, MIC in μM, and IC50 values in µM) than that of free H2LCX ligands. ZnLC6 exhibited a distinguished interacting ability with ctDNA more than that interaction behavior of ZnLC2 based on the derived magnitudes of Kb (the binding constants), and ΔGb≠ (the Gibbs’ free energy), respectively. Such results referred to the lipophilic feature of the terphthalyl derivative compare to that of the succinyl one of the bonded ligands. Also, both ZnLC2 and ZnLC6 exhibited an observable higher reactivity over their both H2LC2 and H2LC6 ligands pointing to the function of Zn2+ ion and the structural effect of the free ligands for their progressing reactivity against the studied bacterial series, fungal series, human cancer cell lines and ctDNA.

A study of in vitro antimicrobial activities and antioxidant of lanthanide complexes with a tri dentate Schiff base ligand

The tridentate N3-type Schiff base 4-(anthracen-10-yl)-2,6-di(pyridin-2-yl)pyridine was synthesized from the condensation reaction of 2-acetyl pyridine and anthracene-10-carbaldehyde with ammonia using one pot methodology. This hybrid ligand was used for synthesis of lanthanide complexes (La, Sm and Eu) as novel potential biological agent. The lanthanide complexes were characterized on the basis of elemental, FT-IR, UV-Visible, mass spectrometry as well as molar conductivity. The complexes were screened for in vitro antibacterial and antifungal activities against the multidrug resistant pathogens such as Escherichia coli, Staphylococcus aureus and Aspergillus niger. The antimicrobial results revealed that Sm+3 complex has a good potency against different gram positive and gram negative bacteria in comparison with other complexes. All lanthanide complexes showed a moderate antioxidant activity with IC50. The DPPH· radical scavenging effects of the Schiff base ligand and its Ln (III) complexes were screened. The Ln (III) complexes were significantly more efficient in quenching DPPH· than the free Schiff base ligand.

Synthesis and Characterization of New Azo dye and applications in colorimetric analysis of trace metal ions in Aqueous Medium

The chelation behavior of azo dye HL derived from coupling 4-nitrophenyl diazonium salt with 7-hydroxycoumarin with Cd (II), Hg(II) and Fe (III) metal ions has been studied. Reaction of the azo dye with Cd (II) and Hg(II) ions at different pH gave new two complexes. At pH=8, complex of the formula [Cd(L)2]Cl2 was formed while at pH=4.5, the complex [Cd(L) Cl2]. 2H2O was obtained. Another two new complexes of the formula [Fe(L)2Cl2]Cl.2H2O have been obtained from the reaction of aqueous solution of the azo dye with FeCl3.6H2O. All the above preparations were performed after fixing the optimum pH and molar concentration. Wide range of molar concentrations was investigated and the concentration which obeyed the Lambert-Beer’s Law, was chosen. The effects of time on the stability of these complexes were checked. The stoichiometry of the above prepared complexes was determined using mole ratio and Job methods. A great bathochromic shift was observed in the UV–Vis absorption spectra of (10-6-10-8 mole/lit.) of an aqueous solution of the solid complexes. The vibration spectra of these complexes gave different changes compared to that of the free ligand. The 1H NMR spectra for one of the complexes were also performed.

Synthesis, Structural Characterization and Antimicrobial Activity of New Substituted Oxazole Thiosemicarbazone Ligand and its Co (II) and Ni (II) Complexes

The New ligand 5-methyl-2-(2-thienyl)-1,3-oxazole-4-carbaldehyde thiosemicarbazone (HL)(1) was synthesized. This ligand reacted with Co(II) and Ni(II) chloride in ratio 1:2 metal:ligand afforded two complexes, [Co(LH)]Cl2 (2) and [Ni(HL)2]Cl2 (3). The ligand and its metal (II) complexes have been characterized by spectroscopic techniques. The X-ray structural studies revealed that the free ligand exist in thione form and remain as neutral tridentate with NNS donor atoms in the tow complexes beside presence of uncoordinated chloride ions in the cavities of the crystal lattice of the complexes. One of these chlorides in complex (2) is hydrogen bonded to a proton of the amine of the ligand. While in complex (3) the chloride bonded to proton of imine (-N2H) of the ligand and the coordination environment has a distorted octahedral. The oxazole N and S atoms in the two complexes are cis to each other whereas the azomethine N atoms are trans coordinated. The ligand and its metal complexes were tested for their in vitro biological activity against six standard microorganisms: two Gram positive namely Bacillus subtilis and Micrococcus luteus, and one Gram negative bacteria Escherichia coli and three fungi: Saccharomyces cerevisiae (Baker’s yeast), Mucor spec., and Aspergillus niger, at a concentration 100µg/ml.

Design, spectroscopic characterization, DFT, molecular docking, and different applications: Anti-corrosion and antioxidant of novel metal complexes derived from ofloxacin-based Schiff base

A new tridentate Schiff base ligand derived from ofloxacin (oflo) with 2-aminophenol was synthesized and a series of d-transition metal complexes were prepared. The ligand and its metal complexes were investigated using elemental, spectral, and thermal studies. The molecular and electronic structure of the free ligand and its Zn(II) complex were refined theoretically, and the chemical quantum parameters were computed. SEM studies were conducted on the free ligand and its Ni(II) chelate to confirm their nanostructure. The anti-corrosive performance of HL for mild steel (MS) was employed using electrochemical frequency modulation (EFM), potentiodynamic polarization (PP) and electrochemical impedance spectroscopy (EIS) and showed a significant efficiency as anticorrosion agent (89.71%). Molecular docking studies were carried out between the ligand and its [Zn(HL)(H2O)Cl2] complex with active sites of 3T88, 3Q8U, and 3Q7K receptors and the complex showed the strongest binding with 3T88 receptor (-31.9 kcal mol−1). The antioxidant activity of the free ligand and its metal chelates had been carried out using the standard DPPH method and the free ligand showed the highest antioxidant activity (IC50 = 10.52 µg/mL). The in vitro antibacterial activity showed that all prepared compounds were biologically active and Fe(III) complex has the highest inhibiting activity against Proteus Vulgaris Gram-negative bacteria.

Spectroscopic Characterization, Cyclic Voltammetry, Biological Investigations, MOE, and Gaussian Calculations of VO(II), Cu(II), and Cd(II) Heteroleptic Complexes.

A novel hydrazone ligand (o-H2BMP) N-(benzo[d]thiazol-2-yl)-3-oxo-3-(2-(1-(pyridin-2-yl)ethylidene)hydrazinyl)propanamide alongside its Cu(II), Cd(II), and VO(II) complexes were prepared and structurally characterized via various spectroscopic analyses (Fourier transform infrared spectroscopy, UV-visible spectroscopy, 1H/13C NMR spectroscopy, liquid chromatography coupled to mass spectrometry, and electron paramagnetic resonance spectroscopy) as well as by elemental analysis, thermal gravimetry analysis/differential thermal analysis, and magnetic moment measurements. Powder X-ray diffraction analysis was also performed for the free ligand and its metal complexes to determine the crystallographic structures and atomic spacing. It also provided information on unit cell dimensions and the average crystallite size. Furthermore, geometric optimization and computational studies were carried out by applying Gaussian (09) software based on density-functional theory coupled with the B3LYP functional and LANL2DZ/6-31+G(d,p) mixed basis set to evaluate some distinct features such as molecular electrostatic potential, E HOMO, and E LUMO. Moreover, electrochemical measurements were performed for Cu(II) in the absence/presence of the chelating agent to predict the effect of complexation interaction in the solution state study. As part of the biological examination, antioxidant and antimicrobial assays were conducted for each compound individually, in addition to cytotoxicity evaluations via MTT assays for all isolated complexes compared to the corresponding metal salts. The MOE (molecular operating environment) approach was also applied to model the interface between the isolated compounds and proteins that were expressed in breast cancer at the atomic level.

A New Dinuclear Copper(II)-Hydrazone Complex: Synthesis, Crystal Structure and Antibacterial Activity

Abstract: Increasing microbial resistance has become a threatening situation for humanity. Therefore, new active antimicrobial compounds are needed to be synthesized. Copper complexes, one of these types of biologically active compounds, appear as compounds with a wide range of biological uses. Many scientific investigations have shown that copper complexes have antibacterial, antimalarial, anti-inflammatory, and anticancer activities. In this study, a new bis-copper(II) complex based on a hydrazone ligand (Ligand A) was designed, synthesized, and evaluated as an antimicrobial agent. The characterization of copper(II) complex was mainly done with single crystal X-ray diffraction and other spectroscopic techniques (FT-IR and Elemental Analysis). In order to determine the chemical structure and vibrational properties, theoretical calculations were carried out. Vibrational wavenumbers and HOMO-LUMO energy gap of copper(II) complex were investigated using the DFT/ B3LYP method, LanL2DZ basis set. The agreement between experimental and theoretical results were observed. Information about local and global chemical activity, the electrophilic and nucleophilic nature of copper(II) complex were theoretically obtained. The ligand and its copper(II) complex were investigated for their antibacterial effects against Gram (+) and Gram (-) bacteria. The results show that copper(II) complex was more effective in reducing cell viability of Enterococcus faecalis, Staphylococcus aureus, and Staphylococcus epidermidis than free hydrazone ligand, whereas it was not effective towards Gram (-) forms. Copper(II) complex displayed the highest antimicrobial activity against Staphylococcus aureus ATCC 25923 and S. epidermidis CECT 4183. The results suggested that the designed metal complex can be a good alternative to similar complex systems as an antimicrobial agent. Besides, there are not many studies in the literature on the antibacterial activities of the copper(II) complex and its ligand. For this reason, the study will contribute to the literature.