Transition metal complexes of acetamidomalondihydroxamate: synthesis,spectral, thermal and electrochemical studies

Acetamidomalondihydroxamate (K₂AcAMDH) and its manganese(II), iron(II), cobalt(II), nickel(II), copper(II) and zinc(II) complexes were synthesized and characterized by elemental analysis, UV–VIS, IR and magnetic susceptibility. The pK _a1 and pK _a2 values of the dihydroxamic acid in aqueous solution were found to be 8.0?±?0.1 and 9.7?±?0.1. The dihydroxamate anion AcAMDH behaves as a tetradentate bridging ligand through both hydroxamate groups, forming complexes with a metal to ligand ratio of 1?:?1 in the solid state. The FTIR spectra and thermal decompositions of the ligand and its metal complexes were recorded. The redox behavior of the complexes was investigated in aqueous solution by square wave voltammetry and cyclic voltammetry at neutral pH. In contrast to the solid state, in solution the copper(II) and zinc(II) ions form stable complex species with a metal to ligand ratio of 1?:?2. The iron(II) and nickel(II) complexes show a two-electron irreversible reduction behavior, while the copper(II) and zinc(II) complexes undergo reversible electrode reactions. The stability constants of the complexes were determined by square wave voltammetry.     

Synthesis, spectral and thermal properties of some transition metal(II) complexes with a novel ligand derived from thiobarbituric acid

Four novel metal(II) complexes, Ni(L)₂, Co(L)₂, Cu(L)₂, and Zn(L)₂ (L = 5-(2-(1,5-dimethyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazol-4-yl)hydrazono)-1,3-diethyl-2-thioxo-dihydropyrimidine-4,6(1H,5H)-dione), were synthesized using the procedure of diazotization, coupling and metallization. Their structures were identified by elemental analyses, ¹H NMR, ESI-MS and FT-IR spectra. The effect of different central metal(II) ions on absorption bands of the metal(II) complexes was researched. The thermal properties of the metal(II) complexes were investigated by thermogravimetry (TG) and differential scanning calorimetry (DSC). Furthermore, the thermodynamic parameters, such as activation energy (E*), enthalpy (?H*), entropy (?S*) and free energy of the decomposition (?G*) are calculated from the TG curves applying Coats–Redfern method. The results show that the metal(II) complexes have suitable electronic absorption spectra with blue-violet light absorption at about 350–450 nm, high thermal stability with sharp thermal decomposition thresholds.     

Spectral and thermal studies of thiobarbituric acid complexes

The complexes of 2-thiobarbituric acid with Fe(II), Fe(III), Co(II), Cu(II), Zn(II) and Cd(II) have been isolated and characterized on the basis of elemental analyses, molar conductance, magnetic moment and spectral studies. The thermal decomposition of the metal complexes was studied by TG and DTA techniques. The kinetic parameters namely, activation energy, entropy of activation and the reaction orders were estimated.     

Rhenium(II) nitrosyl complexes: synthesis,characterization, DFT calculations and DNA nuclease activity

The rhenium(II) dinitrosyl and mononitrosyl complexes, i.e. [Re(NO)₂(CN)₄]·(Phen)₂·2H₂O (1) and PhenH[Re(NO)(CN)₄(H₂O)]·(Phen)·3H₂O (2) have been isolated and characterized. The X-ray crystal structure of 2 reveals that Re(II) is octahedrally coordinated with one nitrosyl, four cyanides, and one water, with one phenanthroline protonated to compensate the charge of the Re(II) center. The crystal structure shows chemically significant non-covalent interactions like hydrogen bonding involving the uncoordinated water and π–π interactions between phenanthrolinium and phen. The structures of both complexes have been optimized by DFT. Absorption and emission spectral studies and viscosity measurements indicate that both 1 and 2 interact with calf thymus DNA through partial intercalation of DNA bases. The intrinsic-binding constants, obtained from UV–vis spectroscopic studies, are 1.2?×?10⁴ and 7.2?×?10⁴?M^?1 for 1 and 2, respectively. Both 1 and 2 are capable of inducing cleavage of plasmid DNA in the presence of H₂O₂ to form the supercoiled form to nicked circular form. The spectroscopic results of DNA binding are supported by molecular docking studies.     

Mononuclear metal complexes of organic carboxylic acid derivatives: synthesis, spectroscopic characterization, thermal investigation and antimicrobial activity

Two Schiff base ligands bearing organic acid moiety, vis., N-(2-thienylmethylidene)-2-amino-4-chlorobenzoic acid (HL(1)) and N-(2-hydroxybenzylidene)-2-amino-4-chlorobenzoic acid (H(2)L(2)) have been synthesized by the interaction of 2-thiophenecarboxaldehyde and 2-hydroxybenzaldehyde with 2-amino-4-chlorobenzoic acid. Co(II), Ni(II), Cu(II) and Zn(II) complexes of these ligands have been prepared. They are characterized on the basis of analytical data, molar conductance, IR, (1)H NMR, UV-vis, mass spectra, magnetic measurements, thermal analysis and X-ray powder diffraction technique. The molar conductance data reveal that these complexes are non-electrolytes. The ligands are coordinated to the metal ions in a terdentate manner with ONO/ONS donor sites of the carbonyl oxygen, azomethine nitrogen and phenolic oxygen or thiophenic sulphur. An octahedral structure is proposed for the prepared metal complexes and some ligand field parameters (D(q), B and beta) in addition to CFSE were calculated. The thermal stability of the metal complexes is evaluated. The Schiff base ligands and their metal complexes have been tested against four species of bacteria as well as four species of fungi and the results have been compared with some known antibiotics.     

Polymer‐supported metal complexes as antibacterial agents: synthesis,characterization and thermal degradation kinetics

Polymeric metal complexes were prepared using a synthesized novel terpolymer ligand involving anthranilic acid–o‐toluidine–formaldehyde by a polycondensation technique. The synthesized ligand and its metal complexes were characterized using elemental analysis and molar conductivity measurements, and FT‐IR, electronic, electron spin resonance and NMR (¹H and ¹³C) spectral methods. The surface morphology and the nature of the synthesized compounds were examined using scanning electron microscopy and X‐ray diffraction. The thermal stabilities of the ligand and its metal complexes were determined using thermogravimetric analysis (TGA). From the TGA results, various kinetic parameters, i.e. activation energy and order of reaction, and thermodynamic parameters, i.e. entropy change, apparent entropy, frequency factor and free energy change, were determined using the Freeman–Carroll and Sharp–Wentworth methods. In addition, a thermal degradation model was also proposed using the Phadnis–Deshpande method. The thermal stability of the ligand and its metal complexes was found to be appreciably high; in particular, the ligand showed very high stability compared to its metal complexes due to intramolecular hydrogen bonding. Furthermore, the synthesized compounds were subjected to in vitro antibacterial studies with various microorganisms. The results of the studies confirmed that the compounds showed better antibacterial results than a standard antibacterial drug. Copyright © 2014 John Wiley & Sons, Ltd.     

Synthesis and characterization of barbituric and thiobarbituric acid complexes

Summary Synthesis of barbituric and thiobarbituric acid complexes derived from cobalt(II), nickel(II) and copper(II) salts were carried out. The elemental analyses suggest a range of stoichiometries, 11, 12 and 13. Electronic spectra and magnetic susceptibility measurements were used to infer the structures. The i.r. spectra of the ligands and their complexes are used to identify the type of bonding.     

New metal complexes derived from S-benzyldithiocarbazate (SBDTC) and chromone-3-carboxaldehyde: synthesis,characterization, antimicrobial,antitumor activity and DFT calculations

Novel monobasic tridentate ONS donor ligand (HL) was synthesized from the condensation reaction of chromone-3-carboxaldehyde with S-benzyldithiocarbazate (SBDTC). Reaction of the ligand with the metal ions copper(II), nickel(II), cobalt(II), oxidovanadium(IV), cerium(III), manganese(II), zinc(II), and cadmium(II) afforded dimeric complexes with the general formula [ML(Y)_m(H₂O)_x]₂·(Y)_m·nH₂O·zCH₃OH, Y?=?NO₃ or Cl, m?=?0–2, x?=?0–2, n?=?0–2, and z?=?0–1 for all complexes except oxidovanadium(IV) complex which has the formula [VOL(H₂O)]₂(SO₄). Structures of the ligand and its metal complexes were established through elemental, spectroscopic data (FT-IR, UV-Vis, and mass), thermal analyses, as well as conductivity and magnetic susceptibility measurements. The geometrical structures of the metal complexes are octahedral and square planar. The ligand and its complexes were subjected to in vitro bioassays against the gram-negative and gram-positive bacteria and the fungus strain with good results for some of these compounds. The antitumor activity of the ligand and its copper(II) and oxidovanadium(IV) complexes were investigated against HepG2 cell line. The molecular parameters of the ligand and its metal complexes have been calculated on the basis of DFT level implemented in the Gaussian 09 program, and computed data were correlated with the experimental results. The HOMO→LUMO electron transition potentially occurs from S-benzyldithiocarbazate to chromone moieties with 4.048?eV. The Mn(II) complex has the highest value of energy barrier, while Cu(II) complex has the lowest value among the complexes. All synthesized complexes have energy gap lower than free ligand and therefore these complexes are more reactive than the free ligand.     

Green synthesis,characterization, and DFT calculations of diorganotin (IV) complexes of Schiff bases

Diorganotin (IV) complexes (1, 2, 3, 4), of the general formula R₂Sn(L)_m have been synthesized where R = n-But, n-Oct; m = 2 when L1 = N-[(Z)-(2-hydroxy-3-methoxybenzylidene)pyrazine-2-carboxamide and m = 1 when L2 = [3,4-bis-{[(E)-(2-hydroxy-3-methoxyphenyl) methylidene]amino}phenyl](phenyl)meth-anone. The prepared Schiff bases and diorganotin complexes have been characterized by elemental analysis, FTIR, and NMR (¹H, ¹³C, and ¹¹⁹Sn) spectroscopic studies. The molecular geometry, thermochemical values, and vibrational frequencies of two complexes in the ground state were calculated using the B3LYP density functional method with LANL2DZ basis set for Sn using Gaussian 09 software. A good correlation of theoretical and experimental results shows that in both the complexes the geometry around the central tin atom is tetrahedral. The studies were further extended to test and compare the in vitro cytotoxic activity of ligands and complexes against MCF-7 cell line by MTT assay. The IC50 values show that cytotoxic activity of ligands increased on complexation with tin metal.     

New aqua rhenium oxocomplex; synthesis,characterization, thermal studies,DFT calculations and catalytic oxidations

The aqua rhenium oxocomplex [ReO(OH)(H₂O)₄]^2? (1) has been prepared and characterized by spectroscopy, thermogravimetry, and elemental analysis and its reactivity towards triphenylphosphine has been evaluated. Complex (1) acts as a catalyst precursor in the presence of molecular oxygen for the oxidation of PPh₃ to OPPh₃. This proceeds through complex intermediates like [Re(PPh₃)_n]³⁺ (2), and [ReO(PPh₃)_n]³⁺ (3). The newly prepared complex (1) was also employed as catalyst for catalytic oxidation of cyclohexane. The geometry of [ReO(OH)(H₂O)₄]^2? has also been optimized in the singlet state by the DFT method with B3LYP level of theory.     

Antifungal active tetraaza macrocyclic transition metal complexes: Designing, template synthesis, and spectral characterization

Eight novel macrocyclic complexes as candidates of antifungal agent were designed and synthesized by incorporating an N₄ donor site via the template condensation of 4,4′-diaminodiphenylmethane, formaldehyde. p-anisidine, and metal salts. The structural features were determined on the basis of their elemental analyses, magnetic susceptibility, molar conductance, FAB Mass, UV-Vis, and IR spectral data. Electronic absorption spectral data of the complexes suggest a square-planar geometry around the central metal ion except the VO(IV) complex, which shows square-pyramidal geometry. The stoichiometry of the complexes had been found to be 1: 1 (metal: ligand). Electrolytic nature of the complexes is assessed from their high conductance data. Monomeric nature of the complexes is confirmed from magnetic susceptibility values. The X-band ESR spectra of the Cu(II) and VO(IV) complexes in DMSO at 300 and 77 K were recorded, and their salient features are reported. The antifungal activity of the macrocyclic metal complexes were screened in vitro against Aspergillus niger, Aspergillus fluvus, Trichoderma harizanum, Trichoderma viridae, and Rhizoctonia solani. The data showed that they possessed antifungal activity. The article is published in the original.     

Mixed benzohydroxamato-acetylacetonato metal complexes: spectral,thermal and photochemical behaviour

Summary Bis(acetylacetonato)VO^II,–Co^II,–Ni^II,–Cu^II,–Zn^II, –UO ₂ ^II and tris(acetylacetonato)Fe^III react with benzohydroxamic acid to yield the corresponding mixed ligand complexes as a result of displacement of one acetylacetone molecule. Intermolecular association may be the reason for six-coordination geometry around the metal ions. A t.g.a. study of the complexes shows, in most cases, initial loss of alcohol and water molecules associated with the complexes; subsequent decomposition steps are characterised by very sharp weight loss. The photochemical stability of the complexes has been studied. Intraligand excitation causes a decomposition in the case of Fe^III and VO^II-complexes but no detectable effect for Co^II, Ni^II, Cu^II, Zn^II, or UO ₂ ^II -complexes.     

Synthesis, structures and DFT calculations on alkaline-Earth metal azide-crown ether complexes

The first examples of azide complexes of calcium, strontium or barium with crown ethers have been prepared and fully characterised, notably [Ba([18]crown-6)(N3)2(MeOH)], [Sr([15]crown-5)(N3)2(H2O)], [Ca([15]crown-5)(N3)2(H2O)] and [Sr([15]crown-5)(N3(NO3)]. Crystal structures reveal the presence of a variety of coordination modes for the azide groups including kappa 1-, mu-1,3- and linkages via H-bonded water molecules, in addition to azide ions. The [Ba([18]crown-6)(N3)2(MeOH)].1/3 MeOH contains dinuclear cations with three mu-1,3-NNN bridges, the first example of this type in main group chemistry. The structures obtained have been compared with molecular structures computed by density functional theory (DFT). This has allowed the effects of the crystal lattice to be investigated. A study of the M--N terminal metal-azide bond length and charge densities on the metal (M) and terminal nitrogen centre (N terminal) in these complexes has allowed the nature of the metal-azide bond to be investigated in each case. As in our earlier work on alkali metal azide-crown ether complexes, the bonding in the alkaline-earth complexes is believed to be predominantly ionic or ion-dipole in character, with the differences in geometries reflecting the balance between maximising the coordination number of the metal centre, and minimising ligand-ligand repulsions.     

Structure investigation, spectral, thermal, X-ray and mass characterization of piroxicam and its metal complexes

[M(H2L)2](A)2.yH2O (where H2L: neutral piroxicam (Pir), A: Cl- in case of Ni(II) or acetate anion in case of Cu(II) and Zn(II) ions and y=0-2.5) and [M(H2L)3](A)z.yH2O (A: SO4(2-) in case of Fe(II) ion (z=1) or Cl(-) in case of Fe(III) (z=3) and Co(II) ions (z=2) and y=1-4) chelates are prepared and characterized using elemental analyses, IR, magnetic and electronic reflectance measurements, mass spectra and thermal analyses. IR spectra reveal that Pir behaves a neutral bidentate ligand coordinated to the metal ions through the pyridyl-N and carbonyl-O of the amide moiety. The reflectance and magnetic moment measurements reveal that these chelates have tetrahedral, square planar and octahedral geometrical structures. Mass spectra and thermal analyses are also used to confirm the proposed formulae and the possible fragments resulted from fragmentation of Pir and its chelates. The thermal behaviour of the chelates (TGA and DTA) are discussed in detail and the thermal stability of the anhydrous chelates follow the order Ni(II) congruent with Cu(II) Fe(II)相似文献   

Synthesis, characterization and thermal analysis of some new transition metal complexes of a polydentate Schiff base

A new polydentate Schiff base (H3L) was synthesized from the condensation of 2,6-diformyl-4-methylphenol and S-methylhydrazine-carbodithionate. The 1:1 metal complexes were obtained from the interaction of H3L and the metal ions Cr(III), Co(II), Ni(II), Cu(II), Cd(II) and Hg(II). The complexes were characterized by elemental analysis and IR spectroscopy. Detailed studies of the thermal properties of the complexes were investigated by thermogravimetry techniques.     

Coordination polymers of glutaraldehyde with glycine metal complexes: synthesis,spectral characterization,and their biological evaluation

Glycine metal complexes were prepared by the reaction of glycine with Mn(II), Co(II), Ni(II), Cu(II), and Zn(II) in 1?:?2 molar ratio. Thereafter their condensation polymerization was done with glutaraldehyde to obtain polymer metal complexes. All the synthesized polymer metal complexes were characterized by elemental analysis, FT-IR, ¹H-NMR, and UV-Vis spectrometry, magnetic susceptibility, and thermogravimetric studies. The analytical data of all the polymers agreed with 1?:?1 molar ratio of metal complex to glutaraldehyde and magnetic moment data suggest that PGG–Mn(II), PGG–Co(II), PGG–Ni(II), and PGG–Cu(II) have an octahedral geometry around the metal atom, whereas the tetrahedral geometry was proposed for PGG–Zn(II) polymer. The PGG–Mn(II) and PGG–Cu(II) showed octahedral geometry. Thermal behavior of the polymer metal complexes was obtained at a heating rate of 10°C?min^?1 under nitrogen atmosphere from 0°C to 800°C. The antimicrobial activities of synthesized polymers were investigated against Streptococcus aureus, Escherichia coli, Bacillus sphaericus, Salmonella sp. (Bacteria), Fusarium oryzae, Candida albicans, and Aspergillus niger (Yeast).     

Design and synthesis of chitin synthase inhibitors as potent fungicides

Chitin is a structural component of fungal cell walls but is absent in vertebrates,mammals,and humans.Chitin synthase is thus an attractive molecular target for developing fungicides.Based on the structure of its donor substrate,UDP-N-acetyl-glucosamine,as well as the modelled structure of the bacterial chitin synthase NodC,we designed a novel scaffold which was then further optimized into a series of chitin synthase inhibitors.The most potent inhibitor,compound 13,exhibited high chitin synthase inhibitory activity with an IC_(50) value of 64.5 μmol/L All of the inhibitors exhibited antifungal activities against the growth of agriculturally-destructive fungi,Fusarium graminearum,Botrytis cinerea.and Colletotrichum lagenarium.This work presents a new scaffold which can be used for the development of novel fungicides.     

Synthesis, spectroscopic and thermal characterization of some transition metal complexes of folic acid

Compounds having general formula: [M(FO)(Cl)(x)(H(2)O)(y)].zH(2)O, where (M=Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Hg(II), FO=folate anion, x=2 or 4, y=2 or 4 and z=0, 1, 2, 3, 5 or 15) were prepared. The obtained compounds were characterized by elemental analysis, infrared as well as electronic spectra, thermogravimetric analysis and the conductivity measurements. The results suggested that all folate complexes were formed by 2:1 molar ratio (metal:folic acid) as a bidentate through both of the two carboxylic groups. The molar conductance measurements proved that the folate complexes are electrolytes. The kinetic thermodynamic parameters such as: E*, DeltaH*, DeltaS* and DeltaG* were estimated from the DTG curves. The antibacterial evaluation of the folic acid and their complexes was also done against some Gram positive/negative bacteria as well as fungi.