Metal complexes of azo coumarin derivative: synthesis,spectroscopic, thermal,and antimicrobial studies

Cu(II), Co(II), Ni(II), Cd(II), and Zn(II) complexes of 6-(2-phenyldiazenyl)-7-hydroxy-4-methyl coumarin (PAHC) are characterized based on elemental analyses, infrared, ¹H NMR, magnetic moment, molar conductance, mass spectra, UV-Vis analysis, thermogravimetric analysis (TGA), and X-ray powder diffraction. From the elemental analyses, it is found that the complexes have formulae [M(L)₂(H₂O) _n ] ? xH₂O (where M = Cu(II), Co(II), Ni(II), Cd(II), and Zn(II), n = 0–2, x = 1–4). The molar conductance data reveal that all the metal chelates are non-electrolytes. From the magnetic and solid reflectance spectra, it is found that the structures of these complexes are octahedral or tetrahedral. The synthesized ligand and metal complexes were screened for antibacterial activity against some Gram-positive and Gram-negative bacteria.     

Synthesis,antimicrobial screening,and DNA-binding/cleavage of new pyrazole-based binuclear CoII,NiII, CuII,and ZnII complexes

Pyrazolato endogenous bridged binuclear Co^II, Ni^II, Cu^II, and Zn^II complexes were prepared and characterized by spectro-analytical methods. The hexadentate N₄S₂ donor was synthesized by condensation of 3,5-dichloroformyl-1H-pyrazole with thiosemicarbazide in dry ethanol. All the complexes were binuclear and octahedral in nature. The ligand and complexes are screened for antimicrobial and DNA-binding/cleavage activities. The binding/cleavage activities with Escherichia coli DNA are monitored with absorption, hydrodynamic, thermal denaturation, and electrophoresis studies. The ligand possesses significant activity against microbes which is further enhanced upon complexation. The DNA-binding study reveals classical intercalation. The Ni^II and Cu^II complexes exhibit higher binding ability.     

Synthesis and characterisation of CoII,NiII and CuII complexes of a tridentate N5 macrocyclic ligand

Summary A novel tridentate macrocyclic ligand was synthesised by the reaction of 2,6-dipicolinic acid hydrazide and 2,3-butanedione. Complexes with Co^II, Ni^II and Cu^II are five-coordinate trigonal bipyramidal on the basis of analyses, electrical conductance, magnetic, electronic and infrared spectral studies. I.r. studies reveal that the ligand coordinates through the pyridine nitrogen and the amido-nitrogen.     

Ligational behavior of new mononucleating SNOO thiosemicarbazone ligands towards 3d metal(II) ions: synthesis and spectroscopic studies

A series of three new mononucleating thiosemicarbazone ligands possessing potential S, N, and O coordination sites have been prepared by the reaction of 2-formylphenoxy acetic acid with substituted thiosemicarbazides. Complexes of these ligands with Co^II, Ni^II, Cu^II, and Zn^II have prepared and characterized by physico-chemical and spectroscopic methods. In all the complexes, the dibasic tetradentate nature of the ligand is evident.     

Synthesis and properties of diphenoxo-bridged CoII, NiII, CuII, and ZnII complexes of a new tripodal ligand: generation and properties of MII-coordinated phenoxyl radical species

Four dinuclear complexes of composition [MII2(L)2].xS [M=Co, x=0.5, S=1,4-dioxane (1.0.5 1,4-dioxane); Ni, x=0 (2) [single crystals have x=2, S=diethyl ether (2.2 diethyl ether)]; Cu, x=0 (3); Zn, x=0.5, S=1,4-dioxane (4.0.5 1,4-dioxane)] have been synthesized using a new tripodal ligand [2,4-di tert-butyl-6-{[(2-pyridyl)ethyl](2-hydroxybenzyl)-aminomethyl}-phenol (H2L)], in its deprotonated form, providing a N 2O 2 donor set. Crystallographic analyses reveal that the complexes have a similar diphenoxo-bridged structure. Each metal ion is terminally coordinated by 2,4-di tert-butyl-phenolate oxygen, a tertiary amine, and a pyridyl nitrogen. From each ligand, unsubstituted phenolate oxygen provides bridging coordination. Thus, each metal center assumes M (II)N 2O 3 coordination. Whereas the geometry around the metal ion in 1.0.5 1,4-dioxane, 2.2 diethyl ether and, 4.0.5 1,4-dioxane is distorted trigonal-bipyramidal, in 3 each copper(II) center is in a square-pyramidal environment. Temperature-dependent magnetic behavior has been investigated to reveal intramolecular antiferromagnetic exchange coupling for these compounds (-J=6.1, 28.6, and 359 cm(-1) for 1.0.5 1,4-dioxane, 2, and 3, respectively). Spectroscopic properties of the complexes have also been investigated. When examined by cyclic voltammetry (CV), all four complexes undergo in CH2Cl2 two reversible ligand-based (2,4-di tert-butylphenolate unit) one-electron oxidations [E1/2(1)=0.50-0.58 and E1/2(2)=0.63-0.75 V vs SCE (saturated calomel electrode)]. The chemically/coulometrically generated two-electron oxidized form of 3 rearranges to a monomeric species with instantaneous abstraction of the hydrogen atom, and for 4.0.5 1,4-dioxane the dimeric unit remains intact, exhibiting an EPR spectrum characteristic of the presence of ZnII-coordinated phenoxyl radical (UV-vis and EPR spectroscopy). To suggest the site of oxidation (metal or ligand-centered), in each case DFT calculations have been performed at the B3LYP level of theory.     

Bi- and tetranuclear ligational deeds of a polyaza macrocycle having four diazine (N2) bridging components headed for CoII, NiII, CuII and ZnII ions: An emphasis on electrochemistry of non-innocent ligand system

Novel bi- and tetranuclear Co^II, Ni^II, Cu^II and Zn^II complexes having diazine bridging units have been prepared and characterised on the basis of analytical and spectroscopic techniques. With the help of electronic spectra and magnetic moment measurements, it is predicted that the Co^II and Ni^II complexes have octahedral geometry while Cu^II and Zn^II complexes found to be square pyramidal. Present Zn^II and Cu^II complexes are binuclear in nature, where as Co^II and Ni^II complexes are tetranuclear with feeble antiferromagnetic exchange interactions. UV–visible spectral studies, in the range 275–425 nm, evidence the significant blue shift in π → π* transition which provide the ease of stabilization of bonding molecular orbitals in the complexes. All complexes are monomeric in nature. Ligand and all complexes were found to be electrochemically active compounds. One electron transfer process is observed in ligand similarly, there is no significant change in the cyclic voltammograms of Co^II and Zn^II complexes, while Cu^II and Ni^II complexes show one and two electron transfer redox behaviours, respectively in the present macrocyclic ligand field.     

Synthesis, structural characterization and electrochemical studies of new macrocyclic Schiff base containing pyridine head and its metal complexes

A new macrocyclic ligand, 1,3,5-triaza-2,4:7,8:13,14-tribenzo-9,12-dioksa-cyclopentadeca-1,5-diene was synthesized by reaction of 2,6-diaminopyridine and 1,2-bis(2-carboxyaldehyde phenoxy)ethane. Then, its Cu(II), Ni(II), Pb(II), Co(III) and La(III) complexes were synthesized by the template effect by the reaction of 2,6-diaminopyridine and 1,2-bis(2-carboxyaldehyde phenoxy)ethane and Cu(NO₃)₂ · 3H₂O, Ni(NO₃)₂ · 6H₂O, Pb(NO₃)₂, Co(NO₃)₂ · 6H₂O, La(NO₃)₃ · 6H₂O, respectively. The ligand and its metal complexes have been characterized by elemental analysis, IR, ¹H and ¹³C NMR, UV-Vis spectra, magnetic susceptibility, thermal gravimetric analysis, conductivity measurements, mass spectra, and cyclic voltammetry. All complexes are diamagnetic and Cu(II) complex is binuclear. The Co(II) was oxidized to Co(III). The comparative electrochemical studies show that the nickel complex exhibited a quasi-reversible one-electron reduction process, while copper and cobalt complexes gave irreversible reduction processes in DMSO solution.     

Synthesis and electrochemical characterization of complexes of 1,2-bis[2-(pyridylmethylideneamino)phenylthio]ethanes with transition metals (CoII, NiII, CuII)

Transition metal (Ni^II, Co^II, and Cu^II) complexes with 1,2-bis[2-(3-pyridylmethylideneamino)phenylthio]ethane (1) and 1,2-bis[2-(4-pyridylmethylideneamino)phenylthio]ethane (2) were synthesized for the first time by slow diffusion of solutions of compounds 1 or 2 in CH₂Cl₂ into solutions of MX₂ · nH₂O (M = Ni, Co, or Cu; X = Cl or NO₃; n = 2 or 6) in ethanol. The reactions with Co^II and Cu^II chlorides afford complexes of composition M(L)Cl₂ (L = 1 or 2). The reactions of compound 1 with Ni^II salts produce complexes with 1,2-bis(2-aminophenylthio)ethane. The molecular structure of dinitrato[1,2-bis(2-aminophenylthio)ethane]nickel(ii) was confirmed by X-ray diffraction. The ligands and the complexes were investigated by cyclic voltammetry and rotating disk electrode voltammetry. The initial reduction of the complexes proceeds at the metal atom. The oxidation of the chlorine-containing complexes proceeds at the coordinated chloride anion. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 350–355, February, 2008.     

5-(Pyridylmethylidene)-substituted 2-thiohydantoins and their complexes with CuII, NiII, and CoII: Synthesis, electrochemical study, and adsorption on the cystamine-modified gold surface

A series of Cu^II, Ni^II, and Co^II complexes with 5-(pyridylmethylidene)-substituted 2-thiohydantoins (L) were synthesized by the reactions of the corresponding organic ligands with MCl₂·nH₂O. The resulting complexes have the composition LMCl₂ (M = Cu or Ni) or L₂MCl₂ (M = Co). The reactions with N(3)-unsubstituted thiohydantoins afford complexes containing four-membered metallacycles, in which the metal ion is coordinated by the S and N(3) atoms of the thiohydantoin ligand. The reactions of N(3)-substituted thiohydantoins give complexes in which the S and N(1) atoms are involved in coordination. Study by IR spectroscopy demonstrated that the pyridine nitrogen atom is not involved in coordination. Based on the results of electrochemical study of the ligands and complexes by cyclic voltammetry and calculation of their frontier orbitals by the PM3(tm) method, the mechanism of oxidation and reduction of these compounds was proposed. In the first reduction and oxidation steps, the metal atom in the copper and nickel complexes remains, apparently, intact, and these processes occur with the involvement of the ligand fragments, viz., the coordinated thiohydantoin ligand and chloride anion, respectively. In the cobalt complexes, the first reduction step occurs at the ligand; the first oxidation state, at the metal atom. Measurements of the contact angle of aqueous wetting and electrochemical study demonstrated that carboxy-containing 2-thiohydantoins and their complexes can be adsorbed on the cystamine-modified gold surface. The structures of the complexes on the surface differ from the structures of these complexes in solution. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 978–990, June, 2006.     

Fluorescein dye derivative: Synthesis,characterization, quantum chemical and promising antimicrobial activity studies

The dimethyl sulfite as an alkylating as well as alkoxylating reagent is well known in synthetic organic as well as organometallic chemistry for a long time. Herein, we have utilized dimethyl sulfite as an alkylating reagent and reacted with fluorescein derivative, N-fluorescein-lactam-hydrazine ( B ). This reaction leads to the generation of tetramethylated fluorescein lactam hydrazine ( A ). The newly designed and synthesized molecule ( A ) has been characterized by ¹H, ¹³C NMR and HRMS data. The antimicrobial activity of the synthesized alkylated fluorescein derivative has been tested against E. coli, P. aeruginosa, Salmonella typhimurium and S. aureus microbial agents. Time-kill assay results also confirmed that fluorescein derivative is a potent antimicrobial agent and revealed that the time-kill assay of fluorescein derivative is value-added than the well-known antibiotic. In addition, quantum chemical study was used to analyze its activity trend and correlated with the experimental data. The computed results of DFT revealed that the lipophilicity as well as the LUMO-HOMO band gap (ΔE_LUMO-HOMO = 4.75 eV) of compound A make it more suitable as an antimicrobial agent to match with in vitro antimicrobial experimental results. The MIC and MBC values of compound A were observed to be lower in contrast to fluorescein and ampicillin for all the tested bacterial strains, which were approximately 3- to 4-fold lower than MIC and MBC values of the later. Results obtained from the study clearly indicate that compound A has better antimicrobial and bactericidal activity in comparison to ampicillin and fluorescein. Synthesized compound can be a better substitute of traditionally used antibiotics, Ampicillin.     

Crystal Structure and Magnetic Properties of Trinuclear Transition Metal Complexes (MnII,CoII, NiII and CuII) with Bridging Sulfonate-Functionalized 1,2,4-Triazole Derivatives

Here we present the synthesis, structure and magnetic properties of complexes of general formula (Mn)(Me₂NH₂)₄][Mn₃(μ-L)₆(H₂O)₆] and (Me₂NH₂)₆[M₃(μ-L)₆(H₂O)₆] (M = Co^II, Ni^II and Cu^II); L⁻² = 4-(1,2,4-triazol-4-yl) ethanedisulfonate). The trinuclear polyanions were isolated as dimethylammonium salts, and their crystal structures determined by single crystal and powder X-ray diffraction data. The polyanionic part of these salts have the same molecular structure, which consists of a linear array of metal(II) ions linked by triple N1-N2-triazole bridges. In turn, the composition and crystal packing of the Mn^II salt differs from the rest of the complexes (with six dimethyl ammonia as countercations) in containing one Mn⁺² and four dimethyl ammonia as countercations. Magnetic data indicate dominant intramolecular antiferromagnetic interactions stabilizing a paramagnetic ground state. Susceptibility data have been successfully modeled with a simple isotropic Hamiltonian for a centrosymmetric linear trimer, H = −2J (S₁S₂ + S₂S₃) with super-exchange parameters J = −0.4 K for Mn^II, −7.5 K for Ni^II and −45 K for Cu^II complex. The magnetic properties of these complexes and their easy processing opens unique possibilities for their incorporation as magnetic molecular probes into such hybrid materials as magnetic/conducting multifunctional materials or as dopant for organic conducting polymers.     

Synthesis and spectroscopic characterization of a new macrocyclic Schiff base formed by the reaction of 1,5- bis (2-formylphenyl)pentane and 2,6-diaminopyridine,and a study of its metal complexes

A new dialdehyde 1,5-bis(2-formylphenyl)pentane was synthesized from 1,5-dibromopentane with salicylaldehyde and K₂CO₃; macrocyclic ligand was synthesized by reaction of 2,6-diaminopyridine and 1,5-bis(2-formylphenyl)pentane. Cu(II), Ni(II), Pb(II), Zn(II), Cd(II) and La(III) complexes were synthesized by reaction of the ligand and Cu(ClO₄)₂ · 6H₂O, Ni(ClO₄)₂ · 6H₂O, Pb(ClO₄)₂ · 6H₂O, Zn(ClO₄)₂ · 6H₂O, Cd(ClO₄)₂ · 6H₂O and La(ClO₄)₃ · 6H₂O, respectively. The ligand and its metal complexes have been characterized by elemental analysis, IR, ¹H and ¹³C NMR, UV–Vis spectra, magnetic susceptibility, conductivity measurements and mass spectra. All complexes are diamagnetic and Cu(II) complex is binuclear.     

Isolation of four new CoII/CoIII and NiII complexes with a pentadentate Schiff base ligand: syntheses, structural descriptions and magnetic studies

In this paper we report the temperature and pH dependent syntheses and systematic characterization of four new Co(II)/Co(III) and Ni(II) complexes with a pentadentate Schiff base ligand H(3)L obtained by condensing 1,3,-diaminopropan-2-ol with 2-hydroxyacetophenone in 1:2 molar ratio. The room temperature syntheses involving Co(II) and Ni(II) nitrates and the ligand H(3)L lead to the isolation of the dinuclear species [Co(2)L(2)(H(2)O)] (1), and the mononuclear complex [Ni(LH)] (3), respectively, whereas refluxing at basic pH leads to the tetranuclear complexes, [Co(II)(2)Co(III)(2)L(2)(μ(3)-OMe)(2)(NO(3))(H(2)O)(2)]NO(3)·2(H(2)O) (2), and [Ni(4)L(2)(μ(3)-OMe)(2)(H(2)O)(2)]·2H(2)O (4). 1 is found to be a simple mono alkoxo-bridged Co(III) dinuclear species, whereas 2 and 4 are both rhomb-like tetrameric complexes with double oxo bridges and μ(3)-methoxo bridges, derived from the methanol solvent, in an open dicubane arrangement. Moreover 2 shows six coordinate ordered Co(II) and Co(III) ions and 4 has both six- and five-coordinate Ni(II) centers. Compound 3 is assigned a tentative mononuclear structure based on IR, UV-Vis spectroscopic, (1)H-NMR and ESI mass study results and is supposed to have one Ni(II) center coordinated with a ligand fragment in square planar geometry. The variable temperature magnetic susceptibility study for 2 and 4 is performed which indicate for both 2 and 4 the presence of intracluster dominant ferromagnetic interactions.     

Hydrophilic polymer drug from a derivative of salicylic acid: synthesis, controlled release studies and biological behavior

Hydrophilic polymeric drugs bearing "Triflusal" (4-trifluoromethylsalicylic acid), a drug widely used as antithrombogenic agent (Disgren), have been prepared by free radical copolymerization of methacryloyloxyethyl [2-(acetyloxy)-4-(trifluoromethyl)] benzoate (HTRF) and N,N'-dimethylacrylamide (DMA). The reactivity ratios of both monomers have been determined by 1H NMR spectra by applying non-linear least square treatments to the copolymerization equation (terminal model), and the kinetic parameters obtained indicated that the microstructure of copolymer chains is homogeneous, with a random distribution of the active HTRF units along the copolymer chains. That means that for the copolymer system THDMA22 used in this work, HTRF units are mainly isolated in relatively long DMA sequences. Therefore, in this structure the intramolecular interactions between adjacent HTRF units are negligible. Release of Triflusal from THDMA22 has been studied in vitro using buffered solutions at pH = 2, 7.4 and 10 and 37 degrees C. The system showed an interesting pseudo-zero order release profile at pH = 7.4 during several months. It has been also evaluated the pharmacological activity and the behavior of the system in contact with biological media. In this sense, we have carried out some in vitro studies about the antiaggregant properties and biocompatibility of THDMA22. Results demonstrate that this copolymer inhibits platelet aggregation in its macromolecular form and presents a good biocompatibility with Human Osteoblastic Cells (HOS).     

The Bingel monoadducts of La@C82: synthesis, characterization, and electrochemistry

The reaction of La@C82 with diethyl bromomalonate in the presence of base (the Bingel reaction) generated five monoadducts which have been fully characterized. It was found that four of them (mono-A, -B, -C, and -D) are ESR-inactive, suggesting singly bonded regioisomers. In contrast, the fifth product (mono-E) is ESR-active, indicating that it possesses a cyclic moiety between the appended malonate group and the fullerene cage, analogous to conventional Bingel adducts. The differences in the molecular structures of mono-A, -B, -C, and -E result in varying thermal stabilities and electrochemical behavior. In particular, the singly bonded monoadducts undergo the retro-Bingel reaction either under thermal treatment or during electron transfer on the cyclic voltammetric timescale. However, mono-E shows remarkable thermal stability and perfect reversibility under the same experimental conditions.     

Complexes of CuII,NiII, and CoII with 2-cyano-2-(1-oxyl-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazol-2-yl)-1-R-ethylenolates

Copper(ii), nickel(ii), and cobalt(ii) complexes with deprotonated enaminoketone derivatives of 2-imidazoline nitroxide were synthesized. Their crystal structures were established by X-ray diffraction analysis, and their magnetic properties were investigated. All complexes exhibit strong (40—110 cm^–1) intramolecular ferromagnetic exchange interactions.     

Pt(II) complexes with bidentate and tridentate pyrazolyl-containing chelators: synthesis, structural characterization and biological studies

A series of four Pt(II) complexes anchored by bidentate or tridentate pyrazolyl-alkylamine chelators bearing different substituents at the azolyl rings has been prepared with the aim to assess their interest in the design of novel anticancer drugs. All complexes have been fully characterized by classical analytical methods and three of them were characterized also by X-ray diffraction analysis. Their solution behavior, together with lipophilicity measurements, cell uptake, antiproliferative properties, DNA interaction have been evaluated. Albeit all the complexes were less active than cisplatin on ovarian carcinoma A2780 cell line, greatly retained their activity in the cisplatin-resistant A2780cisR cell line and presented a lower resistance factor compared to cisplatin. Moreover, the Pt(II) complexes under investigation were less prone to undergo deactivation by glutathione, believed to be the major cellular target of cisplatin that inactivates the drug by binding to it irreversibly.     

Heterocyclic thiocarboxylato complexes of iron: synthesis,characterization, electrochemistry,and reactions

Heterocyclic-thiocarboxylato complexes of iron, CpFe(CO)₂SCO-het (het?=?2-C₄H₃O, 2-C₄H₃S, CH₂-2-C₄H₃S), have been synthesized via the reaction of iron sulfides, (μ-S _x )[CpFe(CO)₂]₂ (x?=?3,?4), with heterocyclic acid chlorides het-COCl. Photolytic substitutions of these complexes CpFe(CO)₂SCO-het with triphenylphosphine, triethylphosphite, triphenylarsine, and triphenylantimony [ER₃ (E?=?P, R?=?Ph, OC₂H₅; E?=?As, Sb, R?=?Ph)] exclusively gave the monosubstituted complexes CpFe(CO)(ER₃)SCO-het in good yields. The new complexes have been characterized by elemental analysis, UV-Vis, IR, ¹H, and ³¹P NMR spectroscopies and by cyclic voltammetry for a representative family (1, 4a–d). The solid state structures of CpFe(CO)₂SCO(2-C₄H₃S) (2), CpFe(CO)(PPh₃)SCO(2-C₄H₃S) (5a), CpFe(CO)(AsPh₃)SCO(2-C₄H₃S) (5b), and CpFe(CO)(SbPh₃)SCO(2-C₄H₃S) (5c) were determined by X-ray crystal structure analysis.