DNA interaction,antimicrobial and molecular docking studies of biologically interesting Schiff base complexes incorporating 4‐formyl‐N,N‐dimethylaniline and propylenediamine

Four new transition metal complexes incorporating a Schiff base ligand derived from propylenediamine and 4‐formyl‐N ,N ‐dimethylaniline have been synthesized using transition metal salts. The characterization of the newly formed complexes was done from physicochemical parameters and using various techniques like ¹H NMR, ¹³C NMR, IR, UV, electron paramagnetic resonance and mass spectroscopies, powder X‐ray diffraction and magnetic susceptibility. All the complexes were found to be monomeric in nature with square planar geometry. X‐ray powder diffraction illustrates that the complexes have a crystalline nature. The interaction of metal complexes with calf thymus DNA was investigated using UV–visible absorption, viscosity measurements, cyclic voltammetry, emission spectroscopy and docking analysis. The results indicate that the Cu(II), Co(II), Ni(II) and Zn(II) complexes interact with DNA by intercalative binding mode with optimum intrinsic binding constants of 4.3 × 10⁴, 3.9 × 10⁴, 4.7 × 10⁴ and 3.7 × 10⁴ M⁻¹, respectively. These DNA binding results were rationalized using molecular docking in which the docked structures indicate that the metal complexes fit well into the A‐T rich region of target DNA through intercalation. The metal complexes exhibit an effective cleavage with pUC19 DNA by an oxidative cleavage mechanism. The synthesized ligand and the complexes were tested for their in vitro antimicrobial activity. The complexes show enhanced antifungal and antibacterial activities compared to the free ligand.     

Dicoumarol complexes of Cu(II), Fe(II) and Fe(III): preparation,characterization, in‐vitro antibacterial and DNA binding activity

3‐3′‐Benzylidenebis[4‐hydroxycoumarin] or 4‐nitro,3‐3′‐benzylidenebis[4‐hydroxycoumarin] or 4‐methoxy,3‐3′‐benzylidenebis[4‐hydroxycoumarin] and their complexes with Cu(II), Fe(II) and Fe(III) were synthesized and characterized using ¹H‐NMR, ¹³C‐NMR, IR spectra, electronic spectra, magnetic measurements and elemental analyses. The ligands, metal salts, complexes, control and standard drug were tested for their in‐vitro antibacterial activity against Bacillus cereus, Staphylococcus aureus, Escherichia coli, Bacillus subtilis, Salmonella typhi, and Serratia marcescens. The metal complexes exhibit good activity against bacterial strains compared with parental compounds and moderate compared with the standard drug (ciprofloxacin). In‐vitro DNA‐binding activity was carried out using agarose gel electrophoresis. The synthesized compounds show effective DNA‐binding activity. Copyright © 2007 John Wiley & Sons, Ltd.     

DNA‐binding,antibacterial and spectral investigations of drug–Fe(II) complexes

The antibiotic agent ciprofloxacin is well known for its drug design and coordinating ability towards metal ions. Iron(II) complexes of ciprofloxacin with various neutral bidentate ligands have been prepared. The structure of complexes has been investigated using spectral, physicochemical and elemental analyses. Antibacterial activity has been carried out using agar plate technique against Staphylococcus aureus, Bacillus subtilis, Bacillus cereus, Salmonella typhi, Escherichia coli and Serratia marcescens. The results show a significant increase in antibacterial activity compared with parental ligands, metal salt and standard drugs (ofloxacin, levofloxacin). The DNA binding and cleavage efficacy were determined using absorption titration and gel electrophoresis techniques, respectively. The DNA binding and cleavage efficacy were increased in complexes compared with parental ligands and metal salt. Copyright © 2007 John Wiley & Sons, Ltd.     

Dose‐, time‐and lipophilicity‐dependent silver(I)–N‐heterocyclic carbene complexes: Synthesis,characterization and interaction with plasmid and Aedes albopictus DNA

Four new Ag(I)–N‐heterocyclic carbene (NHC) complexes ( 5 – 8 ) bearing symmetrically substituted NHC ligands have been synthesized starting from the corresponding benzimidazolium bromide salts which are accessible in a single step from N ‐substituted benzimidazoles (N ‐alkyl and N ‐aryl) and subsequently reacted with the basic metal source Ag₂O in acetonitrile–methanol. These compounds were characterized using elemental analyses, ¹H NMR, ¹³C NMR, Fourier transform infrared and UV–visible spectroscopic techniques, and molar conductivity. Single‐crystal structural studies for complex 5 show that the Ag(I) centre has a perfectly linear C–Ag–C coordination, with quasi‐parallel pairs of aromatic benzimidazole planes. All the complexes interact with Aedes albopictus DNA via intercalation mode by a large hypochromicity of 22 and 27% and smaller hypochromicity of 16 and 19%. Furthermore, all complexes exhibit efficient DNA cleavage activity via a non‐oxidative mechanistic pathway. The DNase activities of the test compounds revealed a time‐ and concentration‐dependent activity pattern. The Ag(I)–NHC complexes showed considerably higher DNA cleavage activity compared to their respective benzimidazolium salts at a lower concentration. The DNA cleavage of these complexes changed from a moderate effect to a good one, corresponding to the increasing lipophilicity order of the complexes as 5  <  6  <  7  <  8 (1.02, 1.05, 1.78 and 2.06 for 5 – 8 , respectively). This order is further corroborated with the DNA binding study, but with the exception of complex 5 , which shows a better binding ability for DNA (K _b = 3.367 × 10⁶) than complexes 6 – 8 (6.982 × 10⁵, 8.376 × 10⁵ and 1.223 × 10⁶, respectively).     

Mn(III) mixed‐ligand complexes with bis‐pyrazolones and ciprofloxacin drug: synthesis,characterization and antibacterial activities

The fluoroquinolone family member ciprofloxacin is well known for its drug design and coordinating ability towards metal ions. The coordination chemistry of this drug with metal ions of biological and pharmaceutical importance is of considerable interest. Novel Mn(III) mixed‐ligand complexes of ciprofloxacin with various bis‐pyrazolone‐based dinegative bidentate ligands were synthesized and characterized on the basis of their physical properties, magnetic susceptibility measurements, (FT‐IR and electronic) spectral studies. The FAB‐mass spectrum of [Mn(A⁹)(L)(H₂O)₂]·H₂O [where H₂A⁹ = 4,4′‐(p‐tolylmethylene)bis(3‐methyl‐1‐phenyl‐4,5‐dihydro‐1H‐pyrazol‐5‐ol) and HL = 1‐cyclopropyl‐6‐fluoro‐4‐oxo‐7‐(piperazin‐1‐yl)‐1,4‐dihydroquinoline‐3‐carboxylic acid] was determined. All the synthesized compounds were screened for their bioactivity. The mixed‐ligand complexes exhibited comparable activities against two Gram‐negative (Escherichia coli and Serratia marcescens) and two Gram‐positive (Staphylococcus aureus and Bacillus subtilis) microorganisms. Copyright © 2011 John Wiley & Sons, Ltd.     

DNA Binding and Cleavage Activity of cis‐Cobalt Aromatic Oxime Complexes and Its Pyridine/imidazole Adducts

cis‐Cobalt complexes with salicycaldoxime(SAO), (Z)‐1‐(2‐hydroxyphenyl)ethanonoxime (HEO), (Z)‐1‐(2,5‐dihydroxyphenyl)ethanonoxime (DEO), (Z)‐1‐(2,5‐dihydroxyphenyl)(phenyl)methanonoxime (DPO) and their adducts with pyridine (Py) and imidazole (Im) were synthesized and characterized by elemental analysis, magnetic susceptibility, UV‐Vis and IR spectra. The electrochemical studies were carried by cyclic voltammeter, the peak potential separation and formal potential of complexes were independent of sweep rate or scan rate (ν) indicating a quasi reversible one‐electron redox process. Absorption studies and thermal denature studies revealed that each of these octahedral complexes is an avid binder of calf thymus DNA. The apparent binding constants for mixed ligand complexes are in order of ～10³‐10³ M^?1. Based on the data obtained in the DNA binding studies a partial intercalative mode of binding is suggested for these complexes. The nucleolytic cleavage activity of parent complexes and their pyridine adduct were carried out on double stranded pBR322 circular plasmid DNA by using a gel electrophoresis experiment in the presence and absence of oxidant (H₂O₂). All the metal complexes show enhanced cleavage activity in presence of oxidant. The hydrolytic cleavage of DNA of Co(DEO)₂ and Co(DPO)₂ is evidenced from the control experiments showing discernable cleavage inhibition in the presence of the hydroxyl radical inhibitor DMSO and EDTA.     

In‐vitro antimicrobial,thermal and spectral studies of mixed ligand Cu(II) heterochelates of clioquinol and coumarin derivatives

The mixed‐ligand heterochelates of Cu(II) with 5‐chloro‐7‐iodo‐8‐hydroxyquinoline (clioquinol) and various uninegative bidentate ligands were prepared. The structure of mixed‐ligand heterochelates was investigated using spectral, physicochemical, elemental analysis and thermal studies. The FAB‐mass spectrum of [Cu(A²)(CQ)(H₂O)₂].2H₂O has been carried out. Magnetic moment and reflectance spectral studies reveal that an octahedral geometry has been assigned to all the prepared heterochelates. The kinetic parameters such as order of reaction (n), the energy of activation (E_a), the pre‐exponential factor (A), the activation entropy (ΔS^#), the activation enthalpy (ΔH^#) and the free energy of activation (ΔG^#) have been reported. The ligands, metal salts, heterochelates, control and standard drug were tested for their in‐vitro antibacterial activity against Escherichia coli, Pseudomonas aeruginosa, Serratia marcescens and Bacillus substilis. The metal complexes exhibit good activity against bacterial strains compared with parental compounds, and moderate compared with the standard drug (clioquinol). Copyright © 2010 John Wiley & Sons, Ltd.     

Antibacterial and Superoxide Dismutase Activity as Well as DNA Interactions of Ciprofloxacin‐Based Ternary Copper(II) Phenanthroline Complexes

. Five neutral mixed‐ligand mononuclear square‐pyramidal copper(II) complexes of the type [Cu(cpf)(Lⁿ)Cl] (cpf = ciprofloxacin and Lⁿ = phenanthroline derivatives) ( 1 – 5 ) were synthesized and characterized. The complexes were screened for their antibacterial activity and bactericidal activity against two Gram^(+ve) and three Gram^(–ve) microorganisms and the results showed that all complexes studied are more potent than the quinolone standard drug ciprofloxacin. Absorption titration, viscosity, and thermal denaturation measurement studies revealed that each of these square‐pyramidal complexes moderately interacts with calf thymus DNA. The binding constants for mixed ligand complexes are in order of 1.5 × 10⁴–3.0 × 10⁴ M^–1. Based on the data obtained in the DNA binding studies an intercalative mode of binding is suggested for these complexes. The nucleolytic cleavage activity of adducts and gyrase inhibition assay were studied on double stranded pUC19 DNA by gel electrophoresis experiments. From the SOD mimic study; the concentration of complexes ranging from 0.45 μM to 1.45 μM are enough to inhibit the reduction rate of NBT by 50 % (IC₅₀) in NADH/PMS system.     

Ruthenium(II) complexes containing 4‐methoxybenzhydrazone ligands: synthesis,characterization, DNA binding,DNA cleavage,radical scavenging and in vitro cytotoxic activity

Three ruthenium(II) hydrazone complexes of composition [RuCl(CO)(PPh₃)₂L] were synthesized from the reactions of [RuHCl(CO)(PPh₃)₃] with hydrazones derived from 4‐methoxybenzhydrazide and 4‐formylbenzoic acid (HL¹), 4‐methylbenzaldehyde (HL²) and 2‐bromobenzaldehyde (HL³). The synthesized hydrazone ligands and their metal complexes were characterized using elemental analysis and infrared, UV–visible, NMR (¹H, ¹³C and ³¹P) and mass spectral techniques. The hydrazone ligands act as bidentate ones, with O and N as the donor sites, and are predominantly found in the enol form in all the complexes studied. The molecular structures of the ligands HL¹, HL² and HL³ were determined using single‐crystal X‐ray diffraction. The interactions of the ligands and the complexes with calf thymus DNA were studied using absorption spectroscopy and cyclic voltammetry which revealed that the compounds could interact with calf thymus DNA through intercalation. The DNA cleavage activity of the complexes was evaluated using a gel electrophoresis assay which revealed that the complexes act as good DNA cleavage agents. In addition, all the complexes were subjected to antioxidant assay, which showed that they all possess significant scavenging activity against 2,2‐diphenyl‐2‐picrylhydrazyl, OH and NO radicals. The in vitro cytotoxic effect of the complexes examined on cancerous cell lines (HeLa and MCF‐7) showed that the complexes exhibit substantial anticancer activity. Copyright © 2016 John Wiley & Sons, Ltd.     

Synthesis,characterization, and biological and anticancer studies of mixed ligand complexes with Schiff base and 2,2′‐bipyridine

New mixed ligand complexes of transition metals were synthesized from a Schiff base (L¹) obtained by the condensation reaction of oxamide and furfural as primary ligand and 2,2′‐bipyridine (L²) as secondary ligand. The ligands and their metal complexes were studied using various spectroscopic methods. Also thermal analyses were conducted. The mixed ligand complexes were found to have formulae [M(L¹)(L²)]Cl_m ⋅n H₂O (M = Cr(III) and Fe(III): m  = 3, n  = 0; M = Cu(II) and Cd(II): m  = 2, n  = 1; M = Mn(II), Co(II), Ni(II) and Zn(II): m  = 2, n  = 0). The resultant data revealed that the metal complexes have octahedral structure. Also, the mixed ligand complexes are electrolytic. The biological and anticancer activities of the new compounds were tested against breast cancer (MCF‐7) and colon cancer (HCT‐116) cell lines. The results showed high activity for the synthesized compounds.     

Transition metal complexes of a novel quinoxaline‐based tridentate ONO donor ligand: synthesis,spectral characterization,thermal, in vitro pharmacological and molecular modeling studies

Co(II), Ni(II), Cu(II) and Zn(II) complexes of a novel tridentate heterocyclic ligand, 3‐{[(2‐benzoyl‐4‐chlorophenyl)imino]methyl}quinoxalin‐2(1H)‐one, have been synthesized. The ligand and the metal complexes were characterized using elemental analysis, molar conductance and magnetic susceptibility measurements, and UV–visible, Fourier transform infrared, ¹H NMR, ¹³C NMR, electron spin resonance and DART mass spectral data. The ligand behaves as a tridentate one, coordinating through two oxygen atoms from two keto groups and through the azomethine nitrogen atom. The thermal properties of the newly synthesized compounds were determined using thermogravimetric analysis. The ligand and its metal complexes were subjected to powder X‐ray diffraction analysis by which average crystallite size and unit cell parameters were calculated. The electrochemical behaviour of the compounds was studied using cyclic voltammetry. The ligand and the metal complexes were screened for their in vitro antimicrobial activities against the bacterial strains E. coli, K. pneumoniae, S. pneumoniae and S. aureus and the fungal species A. niger, A. flavus, P. chrysogenum and R. stolonifer. DNA binding, DNA cleavage and antioxidant activities of the compounds were also evaluated. The compounds bind with DNA through groove binding. The Cu(II) and Zn(II) complexes exhibit higher superoxide anion and hydrogen peroxide scavenging activities, respectively. The Cu(II) complex exhibits better anticancer activity against the MCF7 cell line. The compounds were subjected to molecular docking study against B‐DNA dodecamer d(CGCGAATTCGCG)₂ and vascular endothelial growth factor receptor kinase to justify the experimental DNA binding and MTT assay. Density functional theory studies were used to optimize the geometry of the compounds and to calculate the nonlinear optical properties. Copyright © 2016 John Wiley & Sons, Ltd.     

Spectral,thermal, biological and multi‐heating rate kinetic properties of Cu(II) complexes containing N2O2 donor ligands: 1,10‐phenanthroline and acyl coumarins

A series of newly synthesized coumarin‐based mixed‐ligand copper complexes with 1,10‐phenanthroline (Ph) were investigated by means of thermogravimetry, differential thermogravimetry, differential scanning calorimetry (DSC), electronic spectra and magnetic measurements. Structural and spectroscopic properties of neutral bidentate ligands as well as all complexes were studied on the basis of mass spectra, NMR (¹H and ¹³C) spectra, FT‐IR spectrophotometry and elemental analyses. IR spectral data suggest tetra‐coordinated N₂O₂ bonding of ligand toward metal ion. Dynamic scan of DSC experiments for copper complexes were obtained at different heating rates (2.5–20°C min^?1). Isoconversion methods of Kissinger and Ozawa were used for the determination of the pre‐exponential factor (A), activation energy (E_a) and order of reaction (n). Kinetic parameters for second‐step degradation obtained by Kissinger's and Ozawa's methods are in good agreement. The results indicate that complexes are much stronger free radical scavenger and antioxidant compounds than ligands. Antimycobacterial screening of ligand and its copper compound against Mycobacterium tuberculosis shows clear enhancement in antitubercular activity upon copper complexation. Also good antimicrobial activities of the complexes against Bacillus subtilis, Staphylococcus aureus, Escherichia coli, Salmonella typhus, Aspergillus niger, Candida albicans and Aspergillus clavatus have been found compared to its free ligands. Copyright © 2012 John Wiley & Sons, Ltd.     

Synthesis,Characterization, Crystal Structure,and Biological Activities of Transition Metal Complexes with 1‐Phenyl‐3‐methyl‐5‐hydroxypyrazole‐4‐methylene‐8′‐quinolineimine

The Schiff base ligand, 1‐phenyl‐3‐methyl‐5‐hydroxypyrazole‐4‐methylene‐8′‐quinolineimine, and its Cu^II, Zn^II, and Ni^II complexes were synthesized and characterized. The crystal structure of the Zn^II complex was determined by single‐crystal X‐ray diffraction, indicating that the metal ions and Schiff base ligand can form mononuclear six‐coordination complexes with 1:1 metal‐to‐ligand stoichiometry at the metal ions as centers. The binding mechanism and affinity of the ligand and its metal complexes to calf thymus DNA (CT DNA) were investigated by UV/Vis spectroscopy, fluorescence titration spectroscopy, EB displacement experiments, and viscosity measurements, indicating that the free ligand and its metal complexes can bind to DNA via an intercalation mode with the binding constants at the order of magnitude of 105–106 M ^–1, and the metal complexes can bind to DNA more strongly than the free ligand alone. In addition, antioxidant activities of the ligand and its metal complexes were investigated through scavenging effects for hydroxyl radical in vitro, indicating that the compounds show stronger antioxidant activities than some standard antioxidants, such as mannitol. The ligand and its metal complexes were subjected to cytotoxic tests, and experimental results indicated that the metal complexes show significant cytotoxic activity against lung cancer A 549 cells.     

Two Lanthanide(III) Complexes based on the Schiff Base N,N′‐Bis(salicylidene)‐1,5‐diamino‐3‐oxapentane: Synthesis,Characterization, DNA‐binding Properties,and Antioxidation

The Schiff base N,N′‐bis(salicylidene)‐1,5‐diamino‐3‐oxapentane (H₂L) and its lanthanide(III) complexes, PrL(NO₃)(DMF)(H₂O) ( 1 ) and Ho₂L₂(NO₃)₂ · 2H₂O ( 2 ), were synthesized and characterized by physicochemical and spectroscopic methods. Single crystal X‐ray structure analysis revealed that complex 1 is a discrete mononuclear species. The Pr^III ion is nine‐coordinate, forming a distorted capped square antiprismatic arrangement. Complex 2 is a centrosymmetric dinuclear neutral entity in which the Ho^III ion is eight‐coordinate with distorted square antiprismatic arrangement. The DNA‐binding properties of H₂L and its Ln^III complexes were investigated by spectrophotometric methods and viscosity measurements. The results suggest that the ligand H₂L and its Ln^III complexes both connect to DNA in a groove binding mode; the complexes bind more strongly to DNA than the ligand. Moreover, the antioxidant activities of the Ln^III complexes were in vitro determined by superoxide and hydroxyl radical scavenging methods, which indicate that complexes 1 and 2 have OH ^· and O₂^{– ·} radical scavenging activity.     

Synthesis,Spectral, X‐Ray Diffraction,DFT, and Nematicidal Activity of Mixed Ligand Complexes of Ethyl 2‐(2‐Hydroxybenzylidine)‐Hydrazine Carboxylate and 1,10‐Phenanthroline with Some Transition Metals

In this work, mixed ligand complexes derived from ethyl 2‐(2‐hydroxybenzylidine)‐hydrazine carboxylate (HL) and 1,10‐phenanthroline (Phen) as ligands were synthesized and their structures elucidated by elemental analysis, infrared (IR), electronic,¹H NMR, and mass spectra, X‐ray diffraction (XRD), magnetic susceptibility measurements, and TG/DTG analyses. The analytical and spectral data support the formation of the complexes with the central ion in each complex six‐coordinated and a slightly distorted octahedral geometry. The IR spectra showed that HL and Phen ligands act as neutral bidentates. The XRD patterns of the complexes showed their crystalline nature. The calculated bond length and the force constant F (U═O) in the uranyl complex are 1.738 Å and 685.90 Nm⁻¹, respectively. The molar conductance values of the synthetic complexes in DMF were found to be in the range 5.00–274.06 S cm²/mol at room temperature. The thermodynamic parameters were evaluated by using the Coats–Redfern (CR) and Horowitz–Metzeger (HM) methods. Theoretical molecular structures were investigated by the density functional theory/B3LYP method using the Gaussian 98 W basis set. The nematicidal activity of the ligands and its metal complexes was also studied.     

Nitrile‐functionalized Hg(II)‐ and Ag(I)‐N‐heterocyclic carbene complexes: synthesis,crystal structures,nuclease and DNA binding activities

Various nitrile‐functionalized benzimidazol‐2‐ylidene carbene complexes of Hg(II) and Ag(I) were synthesized by the interaction of 1‐benzyl/1‐butyl‐3‐(cyano‐benzyl)‐3 H‐benzimidazol‐1‐ium mono/dihexafluorophosphate with Hg(OAc)₂/Ag₂O in acetonitrile. Two of the benzimidazolium salts were structurally characterized by single crystal X‐ray diffraction technique. Structures of reported compounds were characterized by ¹ H, ¹³C NMR, FT‐IR, UV–visible spectroscopic techniques, and molar conductivity and elemental analyses. For bis‐benzimidazolium salt, dinuclear Hg(II)– and Ag(I)–carbene complexes were obtained. Nuclease activity and binding interactions of the synthesized benzimidazolium salts and their Ag(I)–carbene complexes with DNA were studied using agarose gel electrophoresis and, absorption spectroscopy and viscosity measurements, respectively. Ag(I)–carbene complexes showed higher DNA binding activity compared to their respective benzimidazolium salts. However, a benzimidazolium salt and two of the Ag(I) complexes showed remarkably higher nuclease activity both, in the presence and absence of an oxidizing agent. Copyright © 2012 John Wiley & Sons, Ltd.     

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.     

Novel 13,14‐dimethyl‐5,8‐dioxa‐2,11,13,14‐tetraaza‐1,12‐diphosphabicyclo [10.1.1] tetradecane 1,12‐dioxide ligand and its Ni(II), Co(II), and Cu(II) complexes: Synthesis,characterization, antimicrobial,DNA cleavage,and computational studies

A novel diazadiphosphetidine ligand derived from the reaction of 2,4‐dichloro‐1,3‐dimethyl‐1,3,2,4‐diazadiphosphetidine‐2,4‐dioxide and 2,2′‐(ethane‐1,2‐diylbis[oxy])bis(ethan‐1‐amine) and its Ni(II), Cu(II), and Co(II) complexes have been synthesized, characterized by spectroscopic, elemental analyses, magnetic susceptibility, and conductivity methods, and screened for antimicrobial, DNA binding, and cleavage properties. Spectroscopic analysis and elemental analyses indicate the formula [M(H₂L)Cl₂] for the Cu(II), Co(II), Ni(II), and Zn(II) complexes and octahedral geometry for all the complexes. The non‐electrolytic nature of the complexes in dimethyl sulfoxide (DMSO) was confirmed by their molar conductance values, which are in the range 12.32–6.73 Ω^?1 cm² mol^?1. Computational studies have been carried out at the density functional theory (DFT)‐B3LYP/6‐31G(d) level of theory on the structural and spectroscopic properties of diazadiphosphetidine H₂L and its binuclear Cu(II), Co(II), Ni(II), and Zn(II) complexes. Six tautomers and geometrical isomers of the diazadiphosphetidine ligand were confirmed using semiempirical AM1 and DFT method from DMOL³ calculations. The copper complex had the best antibacterial activity against Staphylococcus aureus (ATCC 29213). DNA cleavage activities of the compounds, evaluated on pBR322 DNA by agarose gel electrophoresis in the presence and absence of an oxidant (H₂O₂) and a free‐radical scavenger (DMSO), indicated no activity for the ligand and moderate activity for the complexes, with the copper complex cleaving pBR322 DNA more efficiently in the presence of H₂O₂.     

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.     

Copper(II) and Sodium(I) Complexes based on 3,7‐Diacetyl‐1,3,7‐triaza‐5‐phosphabicyclo[3.3.1]nonane‐5‐oxide: Synthesis,Characterization, and Catalytic Activity

The reaction of 3,7‐diacetyl‐1,3,7‐triaza‐5‐phosphabicyclo[3.3.1]nonane (DAPTA) with metal salts of Cu^II or Na^I/Ni^II under mild conditions led to the oxidized phosphane derivative 3,7‐diacetyl‐1,3,7‐triaza‐5‐phosphabicyclo[3.3.1]nonane‐5‐oxide (DAPTA=O) and to the first examples of metal complexes based on the DAPTA=O ligand, that is, [Cu^II(μ‐CH₃COO)₂(κO‐DAPTA=O)]₂ ( 1 ) and [Na(1κOO′;2κO‐DAPTA=O)(MeOH)]₂(BPh₄)₂ ( 2 ). The catalytic activity of 1 was tested in the Henry reaction and for the aerobic 2,2,6,6‐tetramethylpiperidin‐1‐oxyl (TEMPO)‐mediated oxidation of benzyl alcohol. Compound 1 was also evaluated as a model system for the catechol oxidase enzyme by using 3,5‐di‐tert‐butylcatechol as the substrate. The kinetic data fitted the Michaelis–Menten equation and enabled the obtainment of a rate constant for the catalytic reaction; this rate constant is among the highest obtained for this substrate with the use of dinuclear Cu^II complexes. DFT calculations discarded a bridging mode binding type of the substrate and suggested a mixed‐valence Cu^II/Cu^I complex intermediate, in which the spin electron density is mostly concentrated at one of the Cu atoms and at the organic ligand.