A spectral study of 2-formylimidazole 4N-substituted thiosemicarbazones and their copper(II) complexes

Copper(II) complexes of 2-formylimidazole ⁴N-methyl-, ⁴N-dimethyl- ⁴N-ethyl- and 3-hexa-methyleneiminylthiosemicarbazone, along with two nickel(II) complexes of the latter thiosemicarbazone, have been synthesized. Infrared, electronic, NMR and ESR spectra have been used to characterize the complexes and the uncomplexed thiosemicarbazones. None of the complexes or thiosemicarbazones possess growth inhibitory activity against Aspergillus niger and Paecilomyces variotii.     

Synthesis,structural, spectroscopic,biological and catalytic activity of Co(II), Ni(II) and Cu(II) complexes of benzilic hydrazide (BH)

Co(II), Ni(II) and Cu(II) chloro complexes of benzilic hydrazide (BH) have been synthesized. Also, reaction of the ligand (BH) with several copper(II) salts, including NO₃ ^?, AcO^?, and SO₄ ^? afforded metal complexes of the general formula [CuLX(H₂O) _n ]·nH₂O, where X is the anion and n = 0, 1 or 2. The newly synthesized complexes were characterized by elemental analysis, mass spectra, molar conductance, UV–vis, IR spectra, magnetic moment, and thermal analysis (TG/DTG). The physico-chemical studies support that the ligand acts as monobasic bidentate towards metal ion through the carbonyl and hydroxyl oxygen atoms. The spectral data revealed that the geometrical structure of the complexes is square planar for Cu (II) complexes and tetrahedral for Co(II) and Ni(II) complexes. Structural parameters of the ligand and its complexes have been calculated. The ligand and its metal complexes are screened for their antimicrobial activity. The catalytic activities of the metal chelates have been studied towards the oxidative decolorization of AB25, IC and AB92 dyes using H₂O₂. The catalytic activity is strongly dependent on the type of the metal ion and the anion of Cu(II) complexes.     

Synthesis, spectral characterization and in vitro microbiological evaluation of novel glyoxal, biacetyl and benzil bis-hydrazone macrocyclic Schiff bases and their Co(II), Ni(II) and Cu(II) complexes

A series of binuclear Co(II), Ni(II) and Cu(II) complexes were synthesized by the template condensation of glyoxal, biacetyl or benzil bis-hydrazide, 2,6-diformyl-4-methylphenol and Co(II), Ni(II) or Cu(II) chloride in a 2:2:2 M ratio in ethanol. These 22-membered macrocyclic complexes were characterized by elemental analyses, magnetic, molar conductance, spectral, thermal and fluorescence studies. Elemental analyses suggest the complexes have a 2:1 stoichiometry of the type [M₂LX₂]·nH₂O and [Ni₂LX₂2H₂O]·nH₂O (where M = Co(II) and Cu(II); L = H₂L¹, H₂L² and H₂L³; X = Cl; n = 2). From the spectroscopic and magnetic studies, it has been concluded that the Co(II) and Cu(II) complexes display a five coordinated square pyramidal geometry and the Ni(II) complexes have a six coordinated octahedral geometry. The Schiff bases and their metal complexes have also been screened for their antibacterial and antifungal activities by the MIC method.     

Dipole moment measurements on metal complexes of monothio-β-diketones

Dipole moments have been reported for over 200 monothio-β-diketone complexes, Met(RCSCHCOR′), (n  2, 3). The data show that the nickel(II), palladium(II), platinum(II), and copper(II) complexes are cis-square-planar, the zinc(II) complexes are tetrahedral, and the chromium(III), iron(III), ruthenium(III), cobalt(III), and rhodium(III) complexes are facial (cis)-octahedral. Measurements of the dipole moments of a considerable number of the metal complexes by both the static polarization and dielectric relaxation methods have shown that atomic polarization is ca. 0.3 D in square-planar, 0.5 D in tetrahedral, and 0.9 D in octahedral complexes.A large number of complexes, Met(RCSCHCOR?_n (R  phenyl or X-substituted phenyl, R′ CF₃) have been studied. The difference in the values of the dipole moments depend upon: (a) the magnitude and vector direction of the PhX bond moments; (b) the inductive effect arising from the difference in electron density of the C¹ and C⁵ carbon atoms of the ligand moiety — this is affected by the nature and position of the substituent X on the phenyl ring; (c) the change in moment brought about by the mesomeric effect of the substituent X.     

Conventional and microwave synthesis,spectral, thermal and antimicrobial studies of some transition metal complexes containing 2-amino-5-methylthiazole moiety

Schiff base metal complexes of Cr(III), Co(II), Ni(II) and Cu(II) derived from 5-chlorosalicylidene-2-amino-5-methylthiazole (HL¹) and 2-hydroxy-1-naphthylidene-2-amino-5-methylthiazole (HL²) have been synthesized by conventional as well as microwave methods. These compounds have been characterized by elemental analysis, FT-IR, FAB-mass, molar conductance, electronic spectra, ¹H-NMR, ESR, magnetic susceptibility, thermal, electrical conductivity and XRD analyses. The complexes exhibit coordination number 4 or 6. The complexes are coloured and stable in air. Analytical data reveal that all the complexes exhibit 1:2 (metal:ligand) ratio. IR data show that the ligand coordinates with the metal ions in a bidentate manner through the phenolic oxygen and azomethine nitrogen. FAB-mass and thermal data show degradation pattern of the complexes. The thermal behaviour of metal complexes shows that the hydrated complexes lose water molecules of hydration in the first step; followed by decomposition of ligand molecules in the subsequent steps. XRD patterns indicate crystalline nature for the complexes. The Schiff bases and metal complexes show good activity against the Gram-positive bacteria; Staphylococcus aureus and Gram-negative bacteria; Escherichia coli and fungi Aspergillus niger and Candida albicans. The antimicrobial results also indicate that the metal complexes are better antimicrobial agents as compared to the Schiff bases.     

Reactions of cyanoacetylhydrazine complexes with salicylaldehyde and consequent metal-promoted reactions

The reactions of salicylaldehyde with a suspension of cyanoacetylhydrazine and/or malonic acid amido-hydrazide complexes in aqueous ethanolic solutions afford novel complexes. The structures of the isolated complexes have been elucidated by conventional physical and chemical measurements. The absence of the cyano group band at 2270 cm⁻¹ in the IR spectra of all complexes, except those of CO(II) and Ni(II) complexes, suggests the promotion of H₂O to the cyano group (CN) forming amido group. Several structures have been proposed in which salicylaldehyde behaves differently toward the cyanoacetylhydrazine complexes. Also, 1-salicylhydrazo-3-imino-3-(o-formyl) phenoxy propionic acid hydrazide is synthesized either by extraction from the isolated solid complexes using disodium ethylene-diaminetetraacetate or during refluxing of Co(II) and/or Fe(II) complexes with salicylaldehyde. This novel compound is confirmed by elemental analysis, spectra (IR and ¹H NMR) and mass spectra.     

Quantum chemical calculations of the isomer shift in iron(II) complexes of 1,2,4-triazoles with a 1 A 1 ⇔ 5 T 2 spin transition

DFT calculations have been performed to determine the isomer shift for a series of iron(II) clusters with nitrogen-containing ligands which serve as models of coordination units in Fe(II) complexes with 1,2,4-triazoles possessing a ¹ A ₁ ? ⁵ T ₂ spin transition. Good agreement has been found between the theoretical and experimental values of the isomer shift for both low-and high-spin phases. Our calculations confirmed the hypothesis about relationship between the experimentally observed differences in the isomer shift for the low-spin phases of the complexes and variations of the Fe-N mean bond length.     

Synthesis,characterization and antimicrobial activities of copper complexes derived from 4-aminoantipyrine derivatives

Cu(II) complexes have been synthesized from the Schiff base ligands derived from furfurlyidene-4-aminoantipyrine and aniline (L¹)/p-nitroaniline (L²)/p-hydroxyaniline (L³). They were characterized using analytical and spectral techniques. All the Cu(II) complexes exhibit square planar geometry. The X-band ESR spectra of the copper complexes in DMSO solution at 300 and 77 K were recorded and their salient features are reported. The in vitro biological screening effects of the investigated compounds were tested against the bacterial species, Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae, Proteus vulgaris and Pseudomonas aeruginosa and fungal species, Aspergillus niger, Rhizopus stolonifer, Aspergillus flavus, Rhizoctonia bataicola and Candida albicans by serial dilution method. A comparative study of inhibition values of the Schiff base ligands and their complexes indicate that the complexes exhibit higher antimicrobial activity than the Schiff base ligands. Superoxide dismutase and reducing power activities of the copper complexes have also been studied. Depending on the molecular structure, the [CuL²(OAc)₂] complex possess promising SOD mimetic activities.     

Synthesis, spectral and thermal studies of N,N − -pyridine-2,6-diyl bis[N −-phenyl(thiourea)] and its metal complexes

Four new metal complexes with the general formula, [ML·mH₂O]nH₂O (where, M = Cu(I), Co(II), Ni(II) or Zn(II); L = N,N ^?-pyridine–2,6-diyl bis[N ^?-phenyl (thiourea)] (PDPT); m = 1 or 3 and n = 0.5 or 4.0), have been synthesized and characterized by elemental analyses, spectral analyses (IR, UV–Vis., ¹H-NMR and MS), thermal analyses (TGA), conductivity and magnetic measurements. The results showed that the ligand (PDPT) acts in a mononegative tridentate manner towards Cu(I) ion coordinating via the two thiol sulfurs and pyridyl nitrogen groups with displacement of only one hydrogen atom from the thiol group, while the ligand behaves in a binegative tridentate manner towards the Co(II), Ni(II) and Zn(II) ions with displacement of two hydrogen atoms from the two thiol groups. The value of magnetic measurements showed a diamagnetic character of the copper complex indicating the reduction of Cu(II) to Cu(I). Semi-empirical calculations of the ligand and its metal complexes have been used to study the molecular geometry using ZINDO/1, PM3 and AM1. Also, the harmonic vibration spectra of the ligand and its metal complexes have been investigated with the purpose to assist the experimental assignment of metal complexes. The results of the optical absorption studies reveal that the optical transition is direct with band gaps energy (E_g) values 2.62, 1.98 and 1.85 eV for Cu, Co and Ni complexes, respectively, indicating that these complexes can behave as semi-conductors.     

Synthesis and spectral characterization of zinc(II) and cadmium(II) complexes of acetone-N(4)-phenylsemicarbazone: Crystal structures of acetone-N(4)-phenylsemicarbazone and a cadmium(II) complex

Seven Zn(II) and Cd(II) complexes of ON donor acetone-N(4)-phenylsemicarbazone (HL) have been synthesized and physico-chemically characterized by partial elemental analyses, molar conductance measurements, infrared, electronic and ¹H NMR spectral studies. The semicarbazone binds the metal as a neutral bidentate ligand in all the complexes. The crystal structures of acetone-N(4)-phenylsemicarbazone and [Cd(HL)₂Cl₂] have been determined by X-ray diffraction studies. The coordination geometry around cadmium(II) in the complex [Cd(HL)₂Cl₂] is distorted octahedral.     

Epr studies of copper(II) and oxovanadium(IV) dithiophosphate complexes in the solid state

A single crystal of Cu(dtp)₂ and numerous powdered copper(II) and oxovanadium(IV) dithiophosphate complexes magnetically diluted in the corresponding Ni and In complexes have been prepared and studied by EPR. It was shown that the values of A(³¹P) for all complexes are isotropic.Some assumptions about the origin of superhyperfine splitting in the EPR spectra of the complexes are discussed.     

Mixed Ligand Complex Formation of Cetirizine Drug with Bivalent Transition Metal(II) Ions in the Presence of 2-Aminomethylbenzimidazole: Synthesis,Structural, Biological,pH-Metric and Thermodynamic Studies

Mononuclear copper(II), cobalt(II) and nickel(II) complexes of cetirizine (CTZ = 2-[2-[4-[(4-chlorophenyl)phenyl methyl]-piperazine-1-yl]-ethoxy]acetic acid) in the presence of 2-aminomethyl-benzimidazole·2HCl (AMBI), as a representative example of heterocyclic bases, were synthesized and studied by different physical techniques. All mixed-ligand complexes have been fully characterized with the help of elemental analyses, molecular weight determinations, molar conductance, magnetic moments and spectroscopic data. The formulae of the isolated complexes are [M(AMBI)(CTZ)(NO₃)(H₂O)₂]·nH₂O where AMBI is the neutral bidentate 2-aminomethylbenzimidazole, CTZ the deprotonated cetirizine and n = 1 for Co(II) or 0 for Cu(II) and Ni(II) complexes. The measured molar conductance values in DMSO indicate that the complexes are non-electrolytes. The formation equilibria of the ternary complexes have been investigated. Ternary complexes are formed by a simultaneous mechanism. Stoichiometry and stability constants for the complexes formed are reported. The concentration distribution of the complexes in solution was evaluated as a function of pH. The thermodynamic parameters were calculated from the temperature dependence of the equilibrium constants and are discussed. The synthesized metal chelates have been screened for their antimicrobial activities against the selected types of Gram-positive (G⁺) and Gram-negative (G^?) bacteria. They were found to be more active against Gram positive than Gram negative bacteria. The antimicrobial activity in terms of metal ions obeys this order: Cu(II) > Ni(II) > Co(II).     

Coordination of secondary and tertiary amines to zinc tetraphenylporphyrin

Stability constants of 46 complexes of zinc(II) tetraphenylporphyrin with primary, secondary, and tertiary amines and thermodynamic parameters of their formation (ΔG ⁰, ΔH ⁰, ΔS ⁰) in chloroform at 283–308 K have been analyzed. Probable factors responsible for enhanced stability of the complexes with ligands containing n-octyl groups are discussed. The X-ray diffraction data for the 1: 1 complex of zinc(II) tetraphenylporphyrin with di-n-octylamine are given.     

Thermodynamic study of the complexation processes between 6,7-dihydro-3(H)-6-methyl-5-methoxy-7-oxo-vic-triazolo (4,5-d) pyrimidine and Cu(II), Zn(II), Cd(II) and Hg(II)

The compound 6,7-dihydro-3(H)-6-methyl-5-methoxy-7-oxo-vic-triazolo (4,5-d) pyrimidine (LH) has been characterized by IR, ¹H-NMR and UV-visible spectroscopy. Furthermore, its acid behaviour in aqueous solutions at variable temperatures and ionic strengths have been studied.The stability constants of the complexes formed by LH with Cu(II), Zn(II), Cd(II) and Hg(II) metal ions at different ionic strengths and temperatures have been calculated by the method of Chabereck and Martell. From these data, the thermodynamic functions for the corresponding complexation processes have been obtained.     

Spectral characterization and biological evaluation of Schiff bases and their mixed ligand metal complexes derived from 4,6-diacetylresorcinol

In the present study two new series of Copper(II), Nickel(II) and Cobalt(II) complexes with two newly synthesized Schiff base ligands 4,6-bis(1-(4-bromophenylimino)ethyl)benzene-1,3-diol (H₂L¹), 4,6-bis(1-(4-methoxyphenylimino) ethyl)benzene-1,3-diol (H₂L²) and organic ligands 8-hydroxy quinoline, 1,10-phenanthroline have been prepared. The Schiff bases H₂L¹ and H₂L² ligands were synthesized by the condensation of 4,6-diacetyl resorcinol with 4-bromo aniline and 4-methoxy aniline. The ligands and their metal complexes have been characterized by FT-IR, Mass, ¹H NMR, UV–Vis., elemental analysis, ESR and Thermal gravimetric analysis. The Schiff base and their metal complexes were tested for antimicrobial activity against gram positive bacteria Staphylococcus aureus, Streptococcus pyogenes and gram negative bacteria Escherichia coli, Pseudomonas aeruginosa and fungus Candida albicans, Aspergillus niger and Aspergillus clavatus using Broth Dilution Method.     

Synthesis, electrochemical and structural characterization of novel azacrown ether containing macrocyclic redox-active vic-dioxime ligand and its mononuclear transition metal complexes: Application of DEPT, HSQC, HMBC-NMR and cyclic voltammetry

This paper presents a new azacrown containing vic-dioxime; anti-N-(4-aminophenyl)aza-15-crown-5-glyoxime (LH₂), and its mononuclear nickel(II), copper(II), cobalt(II), cadmium(II) and zinc(II) complexes. The azacrown moieties appended at the periphery of the oxime provide solubility for the vic-dioxime ligand and complexes in common organic solvents. The mononuclear M(LH)₂ (M = Ni and Cu), M(LH)₂(H₂O)₂ (M = Co) and [M(LH)(H₂O)(Cl)] (M = Cd and Zn) complexes have been obtained with the metal:ligand ratios of 1:2 and 1:1. The structure of the ligand is confirmed by elemental analysis, Fourier transform infrared (FT-IR), ultraviolet-visible (UV-Vis), mass spectrometry (MS), one-dimensional (1D) ¹H, ¹³C NMR, distortionless enhancement by polarization transfer (DEPT) and two-dimensional (2D) heteronuclear single quantum coherence (HSQC) and heteronuclear multiple bond correlation (HMBC) techniques. The structures of the complexes are confirmed by elemental analyses, MS, UV-Vis, FT-IR and ¹H, ¹³C NMR techniques. Redox behaviors of the ligand and its complexes have been investigated by cyclic voltammetry at the glassy carbon electrode in 0.1 M TBATFB in DMSO. The antibacterial activity was studied against Staphylococcus aureus ATCC 29213, Streptococcus mutans RSHM 676, Enterococcus faecalis ATCC 29212, Lactobacillus acidophilus RSHM 06029, Escherichia coli ATCC 25922, Pseudomonasaeruginosa ATCC 27853. The antimicrobial test results indicate that all the complexes have low levels of antibacterial activity against both Gram negative and Gram positive bacterial species.     

Synthesis,characterization, antibacterial activities and carbonic anhydrase enzyme inhibitor effects of new arylsulfonylhydrazone and their Ni(II), Co(II) complexes

Ethane sulfonic acide hydrazide (esh: CH₃CH₂SO₂NHNH₂) derivatives as 5-methylsalicyl-aldehydeethanesulfonylhydrazone (5msalesh), 5-methyl-2-hydroxyacetophenoneethane sulfonylhydrazone (5mafesh) and their Ni(II), Co(II) complexes have been synthesized for the first time. The structure of these compounds has been investigated by elemental analysis, FT-IR, ¹H NMR, ¹³C NMR, LC/MS, UV–vis spectrophotometric method, magnetic susceptibility, thermal studies and conductivity measurements. The antibacterial activities of synthesized compounds were studied against Gram positive bacteria; Staphylococcus aureus, Bacillus subtilis, Bacillus magaterium and Gram negative bacteria; Salmonella enteritidis, Escherichia coli by using the microdilution broth method. The biological activity screening showed that ligands have more activity than complexes against the tested bacteria. The inhibition activities of these compounds on carbonic anhydrase II (CA II) have been investigated by comparing IC₅₀ and K_i values and it has been found that 5msalesh and its complexes have more enzyme inhibition efficiency than other compounds.     

Palladium assisted organic reactions: VI. A new method for the preparation of cyclopalladated benzalimines

A new, improved method is described for the preparation of cyclopalladated benzalimines; it consists of reacting the ortho-bromobenzalimine with bis(dibenzylideneacetone) palladium(0). A number of substituted o-bromobenzalimines has been studied; the bridged bromide dimers and the corresponding bromo (N-substituted benzalimine-6,C,N)triphenylphosphinepalladium(II) complexes have been fully characterised and ¹H and ¹³C NMR spectral data recorded. In the cases of the N-phenylbenzalimines studied, bis(triphenylphosphine) complexes were also isolated and characterised.     

Synthesis and Characterization of a New (E,E)-Dioxime and its Homonuclear Complexes

N′-(4′-Benzo[15-crown-5]naphthylaminoglyoxime (H₂L) and its sodium chloride complex (H₂L·NaCl) have been prepared from 2-naphthylchloroglyoxime, 4′-aminobenzo[15-crown-5] and sodium bicarbonate or sodium bicarbonate and sodium chloride. Nickel(II), cobalt(II) and copper(II) complexes of H₂L and H₂L·NaCl have a metal–ligand ratio of 1:2 and the ligand coordinates through the two N atoms, as do most of the vic-dioximes. The BF ₂ ⁺ -capped Ni(II), Co(III) and mononuclear complexes of thevic-dioxime were prepared. The macrocyclic ligands and their transition metal complexes have been characterized on the basis of IR, ¹H NMR spectroscopy and elemental analyses data.     

Etude des complexes sulfosalicylate de cuivre(III), nickel(II), cobalt(II) et uranyle(II) a l'aide d'une resine echangeuse de cations: Study of the sulphosalicylate complexes ofcopper(II), nickel(II), cobalt(II) and uranyl(II) by means of cation-exchange resins.

Study of the sulphosalicylate complexes of copper(II), nickel(II), cobalt(II) and uranyl(II) by means of cation-exchange resins.The conditional stability constants of the 1:1 complexes of the sulphosalicylate ions (L^3-) with copper(II), nickel(II), cobalt(II) and uranyl ions have been determined in a sodium perchlorate solution (0.1 M) and at various pH values by a cation-exchange method based on Schubert's procedure. The limits of application of the method are discussed. The variation with pH of the conditional stability constants can be explained by the existence of the complexes: CuH₂L, CuHL, CuL^-; NiH₂L⁺, NiHL, NiL^-; CoHL, CoL^-; UO₂H₂L⁺, UO₂HL, UO₂L^-, UO₂LOH^2-. The stability constants of these complexes are reported. Distribution diagrams of the various complexes of each element with pH and total concentration of sulphosalicylate parameters are given.