Metal complexes of novel Schiff base derived from iron sandwiched organometallic and 4‐nitro‐1,2‐phenylenediamine: Synthesis,characterization, DFT studies,antimicrobial activities and molecular docking

The condensation of 2‐acetylferrocene with 4‐nitro‐1,2‐phenylenediamine in a 1:1 molar ratio, resulting in formation of a novel bi‐dentate organometallic Schiff base ligand (L), (2‐(1‐((2‐amino‐5‐nitrophenyl)imino)ethyl)cyclopenta‐2,4‐dien‐1‐yl)(cyclopenta‐2,4‐dien‐1‐yl)iron. Also, its Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) complexes have been synthesized. The stoichiometric ratios of the prepared compounds were estimated using elemental analysis (C, H, N, M), molar conductivity, FT‐IR, UV‐Vis, ¹H‐NMR, SEM and mass spectral analysis. Furthermore, their TG and DTG properties were studied. The geometrical structure of the complexes was found to be octahedral. From spectral analysis, the Schiff base coordinated to metal ions through the azomethine and amine groups. DFT‐based molecular orbital energy calculations of the synthesized ligand have been studied, in which the ligand was theoretically optimized. The Schiff base and its metal complexes have been screened for their antimicrobial activities against different bacterial and fungal species by using disc diffusion method. The anticancer activities of the ligand and its metal complexes have also been studied towards breast cancer (MCF‐7) and human normal melanocytes (HFB‐4) cell lines. Molecular docking was also used to identify the interaction between the Schiff base ligand and its Cd(II) complex with the active site of the receptors of breast cancer mutant oxidoreductase (PDB ID: 3HB5), crystal structure of Staphylococcus aureus (PDB ID: 3Q8U) and yeast‐specific serine/threonine protein phosphatase (PPZ1) of Candida albicans (PDB ID:5JPE).     

Two MnII,CuII complexes derived from 3,5‐bis(1‐imidazoly) pyridine: Synthesis,DNA binding,Molecular docking and cytotoxicity studies

Two complexes [MnL₂ (H₂O)₂]·2ClO₄ (complex 1) and [CuL(H₂O)₃]·2NO₃ (complex 2) (where L = 3,5‐bis(1‐imidazoly) pyridine) were designed and synthesized. The structures of the complexes were characterized by X‐ray crystallography, elemental analyses, and infrared spectrum. The interaction capacity of the complexes with calf thymus DNA has been investigated by UV and fluorescence spectroscopy. Gel electrophoresis assay demonstrated the ability of the complexes to cleave the pBR322 plasmid DNA. Efficient binding properties of DNA were established by UV–vis, fluorescence, and gel electrophoresis. The intrinsic binding constants (K_b) were calculated to be 0.1524, 0.1041 for complexes 1–2, respectively. The cytotoxic activity of the two complexes exhibited a higher cytotoxicity against HeLa cell lines and lower cytotoxicity toward the normal cell lines. Flow cytometry demonstrated the cancer cell inhibitory rate of two complexes. Furthermore, computer‐aided molecular docking studies were performed to visualize the binding mode of the drug candidate at the molecular level. Interestingly, complex 1 exhibited a significant cancer cell inhibitory rate than cisplatin and other complexes.     

Synthesis,characterization, DNA interaction,apoptosis and molecular docking of Cu(II) and Mn(II) complexes with endo‐norbornene‐cis‐5,6‐dicarboxylic acid

Two new novel complexes, [Cu₄(Endc)₄(phen)₄]⋅7(H₂O)⋅2(O) and [Mn₂(Endc)₂(phen)₂(H₂O)₂]⋅(H₂O) (phen =1,10‐phenanthroline, H₂Endc = endo ‐norbornene‐cis ‐5,6‐dicarboxylic acid), were synthesized and structurally characterized using IR and ¹H NMR spectroscopies, elemental analysis and single‐crystal X‐ray diffractometry. Their reactivity with calf thymus DNA and HeLa cell DNA was measured using UV absorption and fluorescence spectroscopies. The results indicated that these complexes can bind to DNA with different binding affinity. Gel electrophoresis assay demonstrated the ability of the complexes to cleave pBR322 plasmid DNA. Apoptotic study showed that the complexes exhibit significant cancer cell inhibitory rates. Eventually, the complexes can suitably dock with a special DNA (PDB ID: 1AIO).     

Synthesis,characterization, molecular docking studies and in vitro screening of new metal complexes with Schiff base as antimicrobial and antiproliferative agents

A series of Cu(II), Co(II), Pd(II), Pt(II), Zn(II), Cd(II) and Fe(III) complexes were designed and synthesized using Schiff base 1‐phenyl‐2,3‐dimethyl‐4‐(N‐3‐formyl‐6‐methylchromone)‐3‐pyrazolin‐5‐one (HL). The new metal complexes were investigated using various physicochemical techniques including elemental and thermal analyses, molar electric conductivity and magnetic susceptibility measurements, as well as spectroscopic methods. Also, the crystal structures of ligand HL and the Pd(II) complex were determined using single‐crystal X‐ray diffraction analysis. For all compounds, the antimicrobial activity was studied against a series of standard strains: Staphylococcus aureus, Bacillus cereus, Enterococcus faecalis, Escherichia coli, Acinetobacter baumannii, Candida albicans, Candida krusei and Cryptococcus neoformans. The in vitro antiproliferative activity of the ligand and complexes was evaluated against ten cancer cell lines: MSC, A375, B16 4A5, HT‐29, MCF‐7, HEp‐2, BxPC‐3, RD, MDCK and L20B. At 10 μM concentration a significant cytotoxic effect of the Co(II), Pd(II) and Cd(II) complexes was observed against B16 4A5 murine melanoma cells. The Zn(II) complex is active against HEp‐2, RD and MDCK cancer cell lines, where IC₅₀ values vary between 1.0 and 77.6 and for BxPC‐3 the activity index versus doxorubicin is 3.7 times higher.     

New transition metal complexes of 9,10‐phenanthrenequinone p‐toluyl hydrazone Schiff base: Synthesis,spectroscopy, DNA and HSA interactions,antimicrobial, DFT and docking studies

The new complexes of Cu (II) and Ni (II) of a tridentate Schiff base ligand derived from 9,10‐phenanthrenequinone and p‐toluic hydrazide have been synthesized and characterized by elemental analysis, electrical conductometry, FT‐IR, Mass, NMR and UV–Vis. The DFT calculations were carried out at B3LYP/6‐31G*(d) level for the determination of the optimized structure of the ligand and its complexes. The as‐synthesized compounds were screened for their antimicrobial activity. Also, their binding behavior with fish salmon‐DNA (FS‐DNA) and human serum albumin (HSA) were studied by different kinds of spectroscopic and molecular modeling techniques. The fluorescence data at different temperatures were applied in order to estimate the thermodynamics parameters of interactions of ligand and its complexes with DNA and HSA. The results showed that the as‐made compounds could bind to FS‐DNA and HSA via the groove binding as the major binding mode. According to molecular docking calculation and competitive binding experiments, these compounds bind to the minor groove of DNA and hydrophobic residues located in the subdomain IB of HSA. In addition, the molecular docking results kept in good consistence with experimental data.     

Synthesis,physicochemical elucidation,biological screening and molecular docking studies of a Schiff base and its metal(II) complexes

A Schiff base 1-((3-nitrophenylimino)methyl)naphthalen-2-olate (HL) and its two novel complexes with Zn(II) and Co(II) metals were successfully synthesized and characterized by FTIR, ¹H NMR, ¹³C NMR, elemental analysis, magnetic susceptibility, TGA and EIS-MS. Crystal of Schiff base was also characterized by X-ray analysis and experimental parameters were found in line with the theoretical parameters. Quantum mechanical approach was also used to compare structural and calculated parameters and to ensure the geometry of metal complexes. The photometric behaviors of all the synthesized compounds were investigated in a wide pH range using BR buffers. Appearance of isosbestic point suggested the existence of Schiff base molecules in different tautomeric forms. Binding of synthesized complexes with calf thymus DNA was explored by photometric and voltammetric titrations and binding constants were calculated. The results indicated that ligand and its metal complexes bind to DNA by intercalation mode. Docking studies indicate their binding possibilities with topoisomerase II. Moreover, all these prepared compounds were screened for enzyme inhibition, antibacterial, cytotoxic and in vivo antidiabetic activities and found active against one or other activity. This effort just provides preliminary data for some biological properties and which can act as foundation stone for their application in drug development.     

Antioxidant,DNA interaction,molecular docking and cytotoxicity studies of aminoethylpiperazine‐containing macrocyclic binuclear copper(II) complexes

A series of new macrocyclic binuclear copper(II) complexes of the type [Cu₂L^1–5(ClO₄)](ClO₄) ( 1 – 5 ) were synthesized by template condensation between precursor compounds 2,6‐bis(4‐aminoethylpiperazin‐1‐ylmethyl)‐4‐substituted phenols and 2,6‐diformyl‐4‐substituted phenols. The synthesized precursors and complexes were characterized using regular physicochemical techniques. The rate constant values obtained for the hydrolysis of 4‐nitrophenylphosphate were in the range 1.83 × 10⁻²–4.19 × 10⁻² min⁻¹. Antioxidant studies against 2,2′‐diphenyl‐1‐picrylhydrazyl revealed the antioxidant potency of the synthesized complexes. Binding studies of the complexes with calf thymus DNA were conducted using electronic, viscometric and voltammetric techniques, and the obtained results suggested a non‐covalent groove mode of binding. The oxidative cleavage of pBR322 DNA in the presence of co‐reactant H₂O₂ and radical scavengers showed single strand scission and involvement of H₂O₂ radical in the cleavage process. Molecular docking studies were performed to insert complexes into the crystal structures of 1BNA and VEGFR kinase at active sites to determine the possible binding mode and predominant binding interactions. In vitro cytotoxicity of the complexes was tested against human epidermoid carcinoma cells (A431) by MTT assay, which revealed the effective anticancer activity of the complexes. Live cell and fluorescent imaging of A431 cells showed that the complexes induce cell death through apoptosis.     

Spectroscopic studies,structural characterization and electrochemical studies of two cobalt (III) complexes with tridentate hydrazone Schiff base ligands: Evaluation of antibacterial activities,DNA‐binding,BSA interaction and molecular docking

Co(III) complexes of tridentate Schiff base ligands derived from N‐(2‐hydroxybenzylideneamino)benzamide (H ₂ L ¹ ) and 2‐(2‐hydroxybenzylidene)hydrazine‐1‐carboxamide ( H ₂ L ² ) were synthesized and characterized using IR, Raman, ¹H–NMR and UV–Vis spectroscopies. X‐ray single crystal structures of complexes 1 and 2 have also been determined, and it was indicated that these Co(III) complexes are in a distorted octahedral geometry. The cyclic voltammetry (CV) of the complexes indicates an irreversible redox behavior for both complexes 1 and 2 . The antibacterial effects of the synthesized compounds have been tested by minimum inhibitory concentration and minimum bactericidal concentration methods, which suggested that the metal complexes exhibit better antibacterial effects than the ligands against Gram‐positive bacteria. The effects of the drug (drug  =  ligands and complexes) on bovine serum albumin (BSA) were examined using circular dichroism (CD) spectropolarimetry, and it was revealed that the BSA (BSA, as a carrier protein) secondary structure changed in the presence of the drug. Interaction of the drug with calf‐thymus DNA (CT‐DNA) was investigated by UV–Vis absorption, fluorescence emission, CV and CD spectroscopy. Binding constants were determined using UV–Vis absorption. The results indicated that the studied Schiff bases bind to DNA, with the hyperchromic effect and non‐intercalative mode in which the metal complexes are more effective than ligands. Furthermore, molecular docking simulation was used to obtain the energetic and binding sites for the interaction of the complexes with Mycobacterium tuberculosis enoyl‐acyl carrier protein reductase (InhA), and results showed that complex 1 has more binding energy.     

Synthesis,structural characterization,antimicrobial, antioxidant and DNA binding studies of some novel homo‐binuclear Schiff base metal (II) complexes

A novel bi‐nucleating Schiff base ligand, 6,6′‐(((1E,1′E)‐thiophene‐2,5‐diylbis (methaneylylidene))bis (azaneylylidene))bis (3,4‐dimethylaniline), and five binuclear M (II) complexes were synthesized. The bi‐nucleating Schiff base ligand and its metal complexes were characterized using various physicochemical techniques, e.g. elemental analyses, spectroscopic methods, conductivity and magnetic moment measurements. The low molar conductance of the complexes in dimethylsulfoxide shows their non‐electrolytic nature. The antibacterial activities were screened against pathogenic bacteria (Staphylococcus aureus, Escherichia coli, Pseudomonas putida and Bacillus subtilis). The antifungal activity was screened against Aspergillus niger, Aspergillus flavus and Rhizoctonia bataicola. The antimicrobial activity data showed that the metal complexes are more potent than the parent Schiff base ligand against microorganisms. The antioxidant activities of the synthesized compounds were investigated through scavenging activity against 2,2‐diphenyl‐2‐picrylhydrazyl, superoxide anion, hydroxyl and 2,2′‐ azinobis (3‐ethylbenzothiazoline‐6‐sulfonic acid) radicals. The complexes have superior radical scavenging activity than the free ligand and the scavenging effects of the Cu (II) complex are stronger than those of the other complexes. DNA binding studies were performed using electronic spectroscopy, fluorometric competition studies and viscosity measurements. The data indicated that there is a marked enhancement in biocidal activity of the ligand under similar experimental conditions because of coordination with metal ions.     

Spectroscopic,thermal, biological activity,molecular docking and density functional theoretical investigation of novel bis Schiff base complexes

New Schiff base ligand (H₂L, 1,2‐bis[(2‐(2‐hydroxyphenylimino)‐methyl)phenoxy]ethane) came from condensation reaction of bisaldehyde and 2‐aminophenol was synthesized in a molar ratio 1:2. Metal complexes and the ligand were completely discussed with spectroscopic and theoretical mechanism. The complexes with Fe(III), Cr(III), Mn(II), Co(II), Cu(II), Ni(II), Th(IV) and Zn(II) have been discussed and characterized by elemental analyses, molar conductance, IR, mass spectroscopy, thermal, magnetic measurements, and ¹H NMR. The results proved that the Schiff base was a divalent anion with hexadentate O₄N₂ donors came from the etheric oxygens (O1, O2), azomethine nitrogens (N1, N2) and deprotonated phenolic oxygens (O3, O4). Density Functional Theory using (B3LYP/6‐31G*) level of theory were implemented to predict molecular geometry, Mulliken atomic energetic and charges of the ligand and complexes. The calculation display that complexes had weak field ligand. The binding energy ranged from 650.5 to 1499.0 kcal/mol for Mn(II) and Th(IV) complexes, respectively. The biological behavior of the Schiff base ligand and its metal complexes were displayed against bacteria and fungi organisms. Fe(III) complex gave remarkable biological activity in comparison with the parent bis Schiff base.     

Inner metal complexes of tetradentate Schiff base: Synthesis,characterization, biological activity and molecular docking studies

A novel Schiff base ligand, namely 2,2′‐((1E,1′E)‐(1,3‐phenylenebis(azanylylidene))bis(methanylylidene))diphenol (H₂L), was synthesized by condensation of m‐phenylenediamine and 2‐hydroxybenzaldehyde (in 1:2 ratio). Series of complexes were obtained from the reaction of La(III), Er(III) and Yb(III) chlorides with H₂L. The ligand and complexes were characterized using elemental analysis, infrared, ¹H NMR, UV–visible and mass spectroscopies, magnetic susceptibility and conductivity measurements and thermal analysis. Infrared and ¹H NMR spectra indicated the coordination of the azomethine nitrogens and deprotonated phenolic oxygen atoms in a tetradentate manner (ONNO). The thermal behaviour of the complexes was studied from ambient temperature to 1000°C. The complexes were found to have water molecules of hydration and coordinated water molecules. The complexes were found to possess high biological activities against various organisms compared to the free ligand (Gram‐positive bacteria Staphylococcus aureus and Bacillus subtilis, Gram‐negative bacteria Salmonella sp., Escherichia coli and Pseudomonas aeruginosa and fungi Aspergillus fumigatus and Candida albicans). The more effective and probable binding modes between H₂L with different active sites of colon cancer (PDB code: 2hq6) and lung cancer (PDB code: 1x2j) receptors were investigated using molecular docking studies.     

Organoruthenium (II) complexes featuring pyrazole‐linked Schiff base ligands: Crystal structure,DNA/BSA interactions,cytotoxicity and molecular docking

Half‐sandwiched ruthenium (II) arene complexes with piano stool‐like geometry with the general formula [(p‐cymene)RuClL¹] and [(p‐cymene)RuClL²] [where L¹ = (Z)‐N′‐((1,3‐diphenyl‐1H‐pyrazol‐4‐yl)methylene)furan‐2‐carbohydrazide and L² = (Z)‐N′‐((1,3‐diphenyl‐1H‐pyrazol‐4‐yl)methylene)thiophene‐2‐carbohydrazide] were synthesized and characterized. The single crystal X‐ray data revealed that the complexes belong to the same crystal system (monoclinic) with octahedral geometry, where the ruthenium atom is surrounded by hydrazone ligand coordinated through ON atoms, one chloride labile co‐ligand and the remaining three coordination sites covered by an electron cloud of p‐cymene moiety. The interaction between the complexes and DNA/bovine serum albumin (BSA) was evaluated using absorption and emission titration methods showing intercalative modes of interaction. The DNA cleavage ability of the complexes was checked by agarose gel electrophoresis method exhibiting the destruction of DNA duplex arrangement. To understand the interaction between ruthenium complex and DNA/BSA molecule, molecular docking studies were performed. In vitro cytotoxicity of the complexes was examined by the 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide (MTT) assay on human lung cancer cell line, A549, and found that at lower IC₅₀, cell growth inhibition has occurred. Similarly, the IC₅₀ values of the complexes treated with cancerous cell lines have produced a significant amount of lactase dehydrogenase and nitrite content in the culture medium, which were evaluated as apoptosis‐inducing factors, suggesting that the ruthenium (II) arene hydrazone complexes with pyrazole ligands have promising anticancer activities.     

Spectroscopic investigation,DFT, fluorescence,molecular docking and biological studies of divalent and trivalent binuclear complexes prepared from benzoyl thiosemicarbazide derivative of 2‐benzylmalonohydrazide

The binuclear Cr (III), Mn (II) and Fe (III) complexes of N,N′‐(2,2′‐(2‐benzylmalonyl)bis (hydrazine‐1‐carbonothioyl))dibenzamide (H₄BPCD), which derived from the combination of 2‐benzylmalonohydrazide suspension with benzoyl‐isothiocyanate, have been isolated and investigated by the necessary analytical and spectroscopic techniques. The IR studies show that H₄BPCD dispose as a mono‐negative hexadentate ligand (NOS)₂ towards Mn (II) ion and tetra‐negative hexadentate (NOS)₂ towards both Cr (III) and Fe (III) ions. The values of molar conductance in DMSO suggested the non‐electrolytic nature for all complexes. The magnetic measurements and the electronic transitions data confirmed the hexa‐coordinate geometry of complexes. The DFT geometry optimization of all compounds and IR comparative study of both theoretical and experimental of H₄BPCD were carried out. Moreover, the H₄BPCD and its Cr (III) complex displayed intra ligand (π → π*) fluorescence emission spectra which corroborate their photoactive nature. The coordinated and crystalline water molecules have been investigated by (TG/DTG) studies. The kinetic and thermodynamic parameters were computed using Horowitz‐ Metzger, Coats‐Redfern and Broido methods. Biological studies of DNA binding, minimum inhibitory concentration, in vitro determination of SOD‐like activity and MTT‐cytotoxicity assay as well as molecular docking studies were tested for the ligand and its complexes.     

Chromium‐metformin ternary complexes: Thermal,DNA interaction and Docking studies

Three chromium ternary complexes with metformin (met) as a primary ligand and bipyridine (bipy) or ortho‐phenylenediamine (opda) or ortho‐phenanthroline (phen) as secondary ligand were synthesized. These complexes [Cr (Cl)₂(Hmet)(bipy)]‐( 1 ), [Cr (Cl)₂(Hmet)(opda)]‐( 2 ) and [Cr (Cl)₂(Hmet)(phen)]‐( 3 ) were characterized by LC–MS, elemental analysis, molar conductance, thermal analysis, infrared spectroscopy, electronic spectroscopy. The geometrical structures have been found to be octahedral. Degradation pattern of the compounds is shown by thermal studies. The Kinetic parameters‐ energy of activation (E_a), enthalpy (ΔH), entropy (ΔS) and free energy changes (ΔG) have been determined by thermogravimetric data. Coats‐Redfern integration method with thirteen kinetic models was used to calculate the kinetic and thermodynamic parameters for the degradation of all the complexes. The stabilities of the complexes were obtained from their molecular orbital structures from which the quantum chemical parameters were calculated using the HOMO‐LUMO energies. UV–Visible absorption, fluorescence, and viscosity measurements have been conducted to assess the interaction of the complexes with CT DNA. The complexes showed absorption hyperchromism in its UV–Vis spectrum with DNA. The binding constants K_b from UV–Vis absorption studies were 3.1x10⁴, 4.4x10⁴, 5x10⁴ M^?1 for 1, 2, 3 respectively and Stern–Volmer quenching constants (K_sq) from fluorescence studies were 0.137, 0.532, 0.631 for 1, 2, 3 respectively. Finally, viscosity measurements revealed that the binding of the complexes with CT‐DNA could be surface binding, mainly due to groove binding. The activity of complexes towards DNA cleavage decrease in the order of 3 > 2 > 1.The light switching properties of the complexes were also evaluated. The complexes were docked in to B‐DNA sequence, 5′(D*AP*CP*CP*GP*AP*CP*GP*TP*CP*GP*GP*T)‐3′ retrieved from protein data bank (PDB ID: 423D), using Discovery Studio 2.1 software.     

Synthesis,characterization, DNA binding,apoptosis and molecular docking of three Mn(II), Zn(II) and Cu(II) complexes with terpyridine‐based carboxylic acid

A series of novel cytotoxic compounds, [Mn(cpt)₂], [Zn(tpt)(H₂O)₂]?DMA?2(H₂O) and [Cu(tpt)]?DMA (cpt = 4′‐(4‐carboxyphenyl)‐2,2′:6′,2″‐terpyridine, tpt = 4‐(2,4,6‐tricarboxylphenyl)‐2,2′:6′,2″‐terpyridine, DMA = (CH₃)₂NH), were isolated and characterized. The structures of these complexes were characterized using single‐crystal X‐ray diffraction. The mode and extent of binding between fish sperm DNA and the complexes were investigated using fluorescence spectroscopy and molecular docking. These results indicate the ability of the complexes to bind to DNA with different binding affinities. The binding of the Zn(II) complex with DNA is stronger than that of the corresponding Cu(II) analogue, which is expected due to the z* effect and geometry. The ability of these complexes to cleave pBR322 plasmid DNA was demonstrated using gel electrophoresis assay, showing that the complexes have effective DNA cleavage activity. In addition, the cytotoxic effects of these complexes were examined on HeLa cells (human cervix epithelia carcinoma cells) in vitro. The three complexes exhibit different cytotoxic effects and decent cancer cell inhibitory rate. This means that the structures and type of metal have a great influence on the activity of these novel complexes.     

Polymer complexes. LXXI. Spectroscopic studies,thermal properties,DNA binding and antimicrobial activity of polymer complexes

Polymer complexes of Co(II), Ni(II), Mn(II), Cr(III) and Cd(II) were prepared by the reaction of 3‐allyl‐5‐[(4‐nitrophenylazo)]‐2‐thioxothiazolidine‐4‐one (HL) with metal ions. The structure of polymer complexes was characterized by elemental analysis, IR, UV–Vis spectra, X‐ray diffraction analysis, magnetic susceptibility, conductivity measurements and thermal analysis. Reaction of HL with Co(II), Ni(II), Mn(II), Cr(III) and Cd(II) ions (acetate or chloride) give polymer complexes ( 1–5 ) with general stoichiometric [M(L)(O₂CCH₃)(H₂O)₂]_n (where L = anionic of HL and M = Co(II) (1) or Ni(II) (2) ), [Mn(HL)₂(OCOCH₃)₂]_n (3) , [Cr(L)₂(Cl)(H₂O)]_n (4) and [Cd(HL)(O₂CCH₃)₂]_n (5) . The value of HOMO–LUMO energy gap (ΔE) for forms (A‐C) of monomer (HL) is 2.529, 2.296 and 2.235 eV, respectively. According to ΔE value, compound has minimum ΔE is the more stable, so keto hydrazone form (C) is more stable than the other forms (azo keto form (A), azo enol form (B)). The interaction between HL, polymer complexes of Co(II), Ni(II), Mn(II), Cr(III) and Cd(II) with Calf thymus DNA showed hypochromism effect. The HL and its polymer complexes were tested against some bacterial and fungal species. The results showed that the Cr(III) polymer complex (4) has more antibacterial activity than HL and polymer complexes (1–3 and 5) against Bacillus subtilis, Staphylococcus aureus and Salmonella typhimurium.     

Synthesis,antimicrobial activity and molecular docking of di‐ and triorganotin (IV) complexes with thiosemicarbazide derivatives

Six organotin (IV) complexes with two ligands derived from 2,3‐butanedione and thiosemicarbazide have been synthesized and fully characterized by several spectroscopic techniques, including ¹¹⁹Sn NMR and single crystal X‐ray diffraction. Reactions of the ligand diacetyl‐2‐(thiosemicarbazone)‐3‐(3‐hydroxy‐2‐naphthohydrazone), L¹H₂, with SnR₂Cl₂ (R = Me, Bu, Ph) lead to the obtaining of complexes 1 – 3 with general formula [SnR₂L¹] (R = Me 1 , R = Bu 2 , R = Ph 3 ), in which the ligand is doubly deprotonated and behaves as a N₂SO donor, whereas from the reactions of diacetyl‐2‐thiosemicarbazone, HATs, with the same organotin precursors any complex could be isolated. By contrast, reaction of HATs with SnR₃Cl induces the ligand cyclization to form a 1,2,4‐triazine‐3‐thione that binds to the metal as a monoanionic donor in a mono or bidentate manner to form compounds 4 – 6 with formula [SnR₃L²] (R = Me 4 , R = Bu 5 , R = Ph 6 ). The antimicrobial activity of the ligands and the six complexes was tested towards bacteria and fungi, including clinical isolated strains. The results show that the ligands are devoid of activity, except HATs that displays activity against Bacillus subtilis. Conversely, the complexes exhibit good antimicrobial properties against Gram positive and negative bacteria, yeasts and moulds. The best results are obtained for complexes [SnBu₃L²] 5 and [SnPh₃L²] 6 , indicating that their more lipophilic nature could play an important role in the ease of microbial cell penetration. In some cases, these complexes display similar or higher activity than that of ampicillin and miconazole, used as antibacterial and antifungal positive controls, respectively. Docking study with DHPS protein (S. aureus) has shown that out of six drugs, the compound 6 has the best binding affinity (?8.5 Kcal/mol).     

Novel metal complexes of 3-acetylcoumarin-2-hydrazinobenzothiazole Schiff base: Design,structural characterizations,DNA binding,DFT calculations,molecular docking and biological studies

Five new Cu (II), Zn (II), Pd (II), Ru (III) and Ag(I) complexes, derived from the 3-acetylcoumarin-2-hydrazinobenzothiazole Schiff base (Hachbt), have been synthesized and characterized. The structures were established with the aid of elemental analyses (C, H, N), FT-IR, ¹H-NMR, ESR, UV–visible and ESI-mass spectra. The complexes were also investigated by magnetic susceptibility, thermal gravimetric analysis (TG-DTA) and cyclic voltammetry measurements. The results suggest that the Schiff base ligand behaves in two different ways: neutral mono/bidentate or mono-negative bi/tridentate. The calf thymus DNA (CT DNA) binding affinities of Hachbt and its complexes have been examined by UV–visible spectroscopy. The antifungal activity of the compounds was also screened against two fungal species of wood-decay basidiomycetes using the agar dilution method. Different complexes caused a reduction in the fungal colony diameters at a media concentration of 100 μg/ml. The best antifungal activity was observed for the Pd (II) and Ag(I) complexes with a 60% and 79% reduction, respectively. The effect of the complexes on the ability of the same fungi to decolorize poly-R dye on agar plates was also tested. All of the complexes showed an enhanced effect on the decolorization ability and the Cu (II) and Ru (III) complexes exhibited the strongest effect at a media concentration of 5 μg/ml. Theoretical studies were performed for all the complexes using the DFT/B3LYP/6–31 + g(d) basis set for calculations on the ligand atoms and LAN2DZ for the Pd (II) complex. The optimized geometries were found to be in a good agreement with the proposed structures. The molecular docking calculations show that the binding affinity of the Pd (II) complex is −309.170-309.2 kcal/mol, which suggests complexation with the DNA minor groove.     

Synthesis, spectral characterization of Schiff base transition metal complexes: DNA cleavage and antimicrobial activity studies

A new series of transition metal complexes of Cu(II), Ni(II), Co(II), Mn(II), Zn(II), VO(IV), Hg(II) and Cd(II) have been synthesized from the Schiff base (L) derived from 4-aminoantipyrine, 3-hydroxy-4-nitrobenzaldehyde and o-phenylenediamine. Structural features were obtained from their elemental analyses, magnetic susceptibility, molar conductance, mass, IR, UV-Vis, ¹H NMR and ESR spectral studies. The data show that these complexes have composition of ML type. The UV-Vis, magnetic susceptibility and ESR spectral data of the complexes suggest a square-planar geometry around the central metal ion except VO(IV) complex which has square-pyramidal geometry. The redox behaviour of copper and vanadyl complexes was studied by cyclic voltammetry. Antimicrobial screening tests gave good results in the presence of metal ion in the ligand system. The nuclease activity of the above metal complexes shows that Cu, Ni and Co complexes cleave DNA through redox chemistry whereas other complexes are not effective.     

Synthesis and characterization studies of 3-formyl chromone Schiff base complexes and their application as antitumor,antioxidant and antimicrobial

A novel Schiff base namely (E)-3-((2,6-dihydroxypyrimidin-4-ylimino)methyl)-4H-chromen-4-one and its Co (II), N (II)i, Cu (II) and Cd (II) complexes have been synthesized and proved by elemental analysis, molar conductance, thermal analysis (TGA), Inductive Coupled plasma (ICP), magnetic moment measurements, X-ray powder diffraction, IR, EI-mass,¹H NMR, ¹³C NMR,UV–Vis. and ESR spectral studies. On the basis of these data, it is evident that the Schiff base acts as bidentate via oxygen atom of carbonyl group and azomethine nitrogen atom for Co (II) complex; monobasic bidentate ligand for Ni (II), Cu (II) and Cd (II) complexes via oxygen atom of hydroxyl group and nitrogen atom of pyrimidine ring. The results showed all complexes have octahedral geometry. The average particle size of the ligand and its complexes were found to be 1.010–0.343 nm. The pharmacological action (antioxidant, antimicrobial and anticancer) of the prepared compounds is studied. The antitumor activity of the ligand and its metal complexes is evaluated against human liver carcinoma (HEPG2) cell. The data displayed the Co (II) complexes strong cytotoxicity where IC₅₀ values of Co (II) complex and 5-fluorouracil (stander drug) are 9.33 and 7.86 μg/ml respectively. The Co (II) and Cd (II) complexes have antibacterial activity more than ampicillin (stander drug). The interaction of the synthesized compounds with calf-thymus DNA (CT-DNA) has been performed via absorption spectra and viscosity technique. The DNA- binding constants have been determined.