Crystal structures and voltammetric behavior of three copper(II) complexes derived from bulky Schiff bases

Three Schiff base copper(II) complexes have been prepared and characterized by elemental analysis, mass spectra, i.r., electronic spectra, _eff and X-ray crystal structures. Cyclic voltammetry studies on the complexes indicate a dependence of the cathodic potentials upon electronic effects, but independence on the solid state structure.     

Synthesis,magnetic and spectral studies of iron(III), cobalt(II,III), nickel(II), copper(II) and zinc(II) complexes of 2–formylpyridine N(4)-antipyrinylthiosemicarbazone

2–Formylpyridine N(4)-antipyrinylthiosemicarbazone and its metal complexes have been synthesized and characterized. Elemental analyses, molar conductivities, magnetic measurements and spectral (i.e., i.r., electronic, n.m.r. and e.s.r.) studies have been used to characterize the complexes. The i.r. spectra show that the thiosemicarbazones behave as bidentate or tridentate ligands either in the thione or thiolato form. Ligand field parameters have been calculated and the proposed stereochemistries are based on the various physical and spectral methods.     

Synthesis,magnetic and spectral studies of iron(III), cobalt(II,III), nickel(II), copper(II) and zinc(II) complexes of 4–formylantipyrine N(4)-antipyrinylthiosemicarbazone

4–Formylantipyrine N(4)-antipyrinylthiosemicarbazone and its metal complexes have been synthesized and characterized. Elemental analyses, molar conductivities, magnetic measurements and spectral (i.r., electronic, n.m.r., e.s.r.) studies have been used to characterize the complexes. The i.r. spectra show that the thiosemicarbazones behave as bidentate (NS) or tridentate ligands (ONS), either in the thione or thiolato form. Stereochemistries are proposed for the complexes on the basis of both spectral and magnetic studies.     

Synthesis and spectral studies of novel copper(II) chelates of sulphur-containing oximes

Summary Copper complexes of benzil--monoxime-2-iminoethanethiol (BMETH₂), benzil--monoxime-2-iminobenzenethiol (BMBTH₂), benzil--monoximethiosemicarbazone (BMTH₂) and benzil--monoximesemicarbazone (BMSH₂) were synthesized and characterized by physicochemical and spectroscopic measurements. The molar conductivities show that all of the complexes are nonelectrolytes. The i.r. spectra suggest that the ligands are tetradentate in all cases, whilst the electronic spectra suggest planar geometries for all the complexes. The calculated e.s.r. parameters show an axial dx ² - y ² ground state and suggest coordination through sulphur, in agreement with the i.r. results. In all of these complexes, the =N—;O group acts as a bridging function to give dimeric structures.     

New complexes of iron(III), cobalt(II), nickel(II) and copper(II) with Schiff bases derived from 2-aminocyclopent-1-ene-1-dithiocarboxylic acid

Summary Fe^III, Co^II, Ni^II and Cu^II, complexes of a new Schiff base ligand, prepared by condensing 2-aminocyclopent-1-ene-1-dithiocarboxylic acid with benzaldehyde (ACB), and also Cu^II and Ni^II complexes of a second Schiff base ligand prepared by condensing 2-aminocyclopent-1-ene-1-dithiocarboxylic acid with salicylaldehyde (ACS), have been prepared and characterized by elemental analyses, conductivity measurements, magnetic and spectral (electronic, i.r. and e.p.r.) studies. The i.r. spectra suggest that both ACB and ACS are acting as bidentate ligands, coordinating through one of the sulphur atoms and through the azomethine nitrogen atom. The magnetic moment of the Fe^III complex indicates spin crossover behaviour. Square planar structures have been assigned to the Cu^II and Ni^II complexes and a tetrahedral structure to the Co^II complex. The e.p.r. spectra of the Cu^II complexes suggest a square planar environment with rhombic distortion around the Cu^II ion.     

Antimicrobial activity studies of mononuclear and binuclear mixed-ligand copper(II) complexes derived from Schiff base ligands and 1,10-phenanthroline

Mixed-ligand complexes of copper(II) with 1,10-phenanthroline and various Schiff bases have been prepared and characterized by elemental analysis, electronic and i.r. spectra, magnetic moment and molar conductance data. The Schiff base behave as bidentate ligands, and the mixed-ligand copper(II) complexes of the ligands HL1, HL2 and HL4 are binuclear. The conductivity data for all the complexes are consistent with those expected for an electrolyte. Antimicrobial activities of some of the ligands and complexes have been tested against Bacillus megaterium and Candida tropicalis. 1H and 13C n.m.r. spectra have been recorded in order to solve the solution structure of the ligands. Thermal properties of all complexes have been studied by the d.t.a. and t.g.a. techniques.     

New heterotrinuclear complexes containing copper(II) and a group IV metal

Summary Heterotrinuclear complexes of the type [Cu₂(TETA)₂Cl₄M] (M = Si, Ge, Sn, Ti and Zr; TETA = triethylene tetramine) have been prepared by direct reaction of [Cu[TETA)]Cl₂ with MCl₄ in a 21 ratio in MeOH. The compounds have been characterized by elemental analyses, e.s.r., electronic and i.r. spectra, magnetic susceptibility and conductivity measurements. The results indicate that [Cu(TETA)]Cl₂ is square planar and ionic, while its heterotrinuclear complexes, [Cu₂(TETA)₂Cl₄M], are covalent with an octahedral environment around the copper(II) ion.     

Copper(II) complexes of 4-formylantipyrine N(4)-substitutedthiosemicarbazones

Copper(II) complexes between three 4-formylantipyrine N(4)-substituted thiosemicarbazones and four copper(II) salts have been prepared and characterized. I.r., electronic and e.s.r. spectra of the complexes, as well as i.r., electronic and 1H and 13C-n.m.r. spectra of the thiosemicarbazones, have been obtained. Both mononuclear and binuclear complexes have been formed with bridging ligands for the latter, being either chloro or acetato. The stoichiometries of the complexes are dependent on both the steric requirements of the thiosemicarbazone ligands and the electronic effects of their N(4)-substituents.     

Study of binuclear copper(II) complexes involving bridging Schiff bases—I

Summary The synthesis of binuclear complexes obtained by the reaction of aromatic diamines with the ternary complexes of copper(II) with bis(2-pyridyl)amine (dpa) as primary ligand and salicylaldehyde or 2-hydroxynaphthaldehyde as secondary ligand have been reported. The complexes have been characterized by elemental analyses, conductance, electronic and i.r. spectral studies. Magnetic measurements indicate antiferromagnetic exchange between two copper(II) centres. E.s.r. spectra exhibit a Ms=2 transition, supporting the antiferromagnetic coupling.     

Binuclear copper(II) complexes of 5-nitrosalicylaldehyde N(3)-substituted thiosemicarbazones

Summary Binuclear copper(II) complexes with six 5-nitrosalicylaldehyde N(3)-substituted thiosemicarbazones have been prepared and characterized. I.r., electronic and e.s.r. spectra of the complexes, as well as i.r., electronic, and ¹H-and ¹³C-n.m.r. spectra of the thiosemicarbazones, have been obtained. The crystal structure of a monomeric copper(II) complex of 5-nitrosalicylaldehyde piperidyl-thiosemicarbazone, H₂5NO₂Sapip, grown from DMF solution, has been solved. Neither the thiosemicarbazones or their binuclear copper(II) complexes show growth inhibitory activity against Aspergillus niger, but the copper(II) complexes show some activity against the fungus Paecilomyces variotii.     

Copper(II) complexes of 4-acetamidobenzaldehyde N(4)-substituted thiosemicarbazones

Mononuclear and binuclear copper(II) complexes with four 4-acetamidobenzaldehyde N(4)-substituted thiosemicarbazones have been prepared in EtOH solution and characterized by physical and spectral methods. I.r., electronic, and e.s.r. spectra of the complexes, as well as i.r., electronic, and n.m.r. spectra of the thiosemicarbazones, have been obtained. These thiosemicarbazones coordinate as anionic or neutral ligands via the thiosemicarbazone moiety's imine nitrogen and thiolate/thione sulfur, the former on loss of the hydrazido hydrogen, N(2)H.     

Nickel(II) and copper(II) complexes of 5-substituted-salicylaldehyde thiosemicarbazones

Binuclear nickel(II) and copper(II) complexes with four 5-methoxysalicylaldehyde N(3)-substituted thiosemicarbazones and nickel(II) complexes of four 5-nitro-salicylaldehyde N(3)-substituted thiosemicarbazones have been prepared and characterized. I.r., electronic, and e.s.r. spectra of the complexes, as well as i.r., electronic, and 1H- and 13C-n.m.r spectra of the thiosemicarbazones, have been obtained. None of these compounds show significant growth inhibitory activity against the fungi Aspergillus niger and Paecilomyces variotii.     

Copper(II), nickel(II), cobalt(II) and oxovanadium(IV) complexes of 1-(3-hydroxy-2-naphthyl)-5-(p-X-phenyl)pent-4-ene-1,3-diones

Complexes of 1-(3-hydroxy-2-naphthyl)-5-(p-X-phenyl)pent-4-ene-1, 3-diones (HXNP) (X = H, Cl, Me or OMe) with divalent metal ions, having the formula M(HXNP)2 (M = Cu, Ni or Co) and M(HXNP)2 · nB (n = 0,2: B = H2O or Py), have been prepared and characterized by elemental analyses, i.r., electronic, 1H-n.m.r. and e.s.r. spectroscopies and by magnetic susceptibility measurements. Spectral assignments show the metal ions to be coordinated through both carbonyl oxygen atoms and the effect of conjugation of the ligand structure (d–* interaction) is strong enough to stabilize the metal ligand bond. The observed hyperfine splitting constants and magnetic moments suggest that the copper complexes are monomers with a slightly distorted planar structure, having more covalent in plane -bonding. The magnetic and spectral properties of the dihydrates and dipyridinates of the cobalt and nickel complexes are commensurate with monomeric high-spin octahedral geometries; polymerization takes place on dehydration–depyridination of nickel(II) complexes. Oxovanadyl complexes of these -diketones have also been prepared; the ligand-to-metal ratio is 2:1 with square pyramidal geometry. The e.s.r. spectra of the complexes show the presence of one unpaired electron in the dxy orbital and the hyperfine splitting constants are sensitive to a change in solvent. The effect of bases on the redox behaviour of copper(II) complexes owing to geometry change is discussed.     

Mono- and binuclear copper(II) complexes of saccharin with 2-pyridinepropanol synthesis,spectral, thermal and structural characterization

Mono- and binuclear copper(II) saccharinate (sac) complexes containing 2-pyridinepropanol (pypr) have been prepared and characterized by elemental analyses, i.r., u.v.–vis., magnetic measurements and single crystal X-ray diffraction. The copper(II) ion in trans-[Cu(pypr)₂(sac)₂] has –1 site symmetry and is octahedrally coordinated by two bidentate neutral pypr (N, O) and two sac (O) ligands. The binuclear copper(II) complex, [Cu₂(-pypr)₂(sac)₂], is built up around a centre of symmetry and contains two strongly distorted square–planar coordinated copper(II) ions bridged by two alkoxo groups of the deprotonated pypr ligand, which also coordinates to the copper(II) ions through its nitrogen. In contrast to the mononuclear complex, the sac ligands in the binuclear complex is N-coordinated. The binuclear complex exhibits diamagnetic behaviour. The i.r. spectra and thermal decompositions of both complexes are described.     

2-thiouracil-based cobalt(II), nickel(II) and copper(II) complexes

Summary Cobalt(II), nickel(II) and copper(II) complexes of 2-thiouracil and its arylazo derivatives were prepared. The elemental analysis suggest a range of 11, 21 and 13 stoichiometries. Electronic spectra and magnetic susceptibility measurements were used to infer the structures and the i.r. spectra of the ligands and their complexes to identify the type of bonding.     

Palladium(II) complexes of ketimines

Summary New Pd^II complexes of biologically active ketimines containing the donor set have been synthesized and characterized by elemental analyses, molecular weight determinations and conductivity measurements. The i.r. and ¹H-n.m.r. spectra indicate a square planar structure for the complexes in which the ligand is monobasic bidentate with oxygen and azomethine nitrogen coordinating sites. Representative ketimines and their respective metal complexes were found to exhibit antimicrobial properties.Author to whom all correspondence should be directed.     

Synthesis and spectroscopic characterization of ternary complexes of copper(II) glycylglycine and substituted phenanthrolines

Summary Complexes of Cu(glygly)phen ygly = glycylglycine; phen = 4,7-dimethyl [(1)], 5,6-dimethyl [(2)], 5-NO₂[(3)], 5-Cl[(4)], 2-oxazolinyl (2-ox) [(5)] Phenanthroline and bis(2-oxazolinylphenanthroline)-copper(II) [(6)] were synthesized and characterized by conductivity measurements, e.p.r., i.r. and reflectance electronic spectroscopies.A broad u.v.-vis. band in the 620–640 nm range and a shoulder at ca. 825 nm suggest that these complexes are five-coordinate. The e.p.r. spectra indicate a stronger equatorial ligand field in the ternary complexes which is absent in the binary Cu-phen complexes, suggesting square pyramidal coordination, whose base contains the three donor atoms from glygly (O, N, N) and one donor from the phenanthroline nitrogen atom. The other nitrogen-containing ligand of the phenanthroline is in an apical position.The spectroscopic results can be correlated with electronic and steric effects attributable to the different substituents on the phenanthroline ligands.Only small variations in the structure of the ternary complexes occur as a function of the electronic effects of substituents on the aromatic phenanthroline ring ligands. Steric hindrance predominates in determining coordination geometry around copper(II).     

Synthesis,characterization and function of ternary copper(II) complexes

Ternary complexes of glycine, alanine, -alanine, serine and ethylenediamine with copper iminodiacetate have been prepared and characterized by their i.r., u.v.-vis. and e.s.r. spectra. The data suggest that the complexes possess axial symmetry and a distorted octahedral configuration in aqueous solution. The H2O molecule on the axial copper site can be replaced by O2–. The bonding parameters, which fall between 0.84 and 0.88, indicate that the bonds between copper(II) and the ligands possess more ionic character. The ternary complex containing serine displays the highest catalytic activity in dismutation of the superoxide radical O2–. This activity may be explained on the basis of the stabilization of CuII-O2– by hydrogen bonding.     

Electronic, e.p.r., cyclic voltammetric and biological activities of copper(II) complexes with macrocyclic ligands

Eight new macrocyclic ligands have been prepared by the reaction of the precursor diketone (benzil, glyoxal, diacetyl or 2,3-pentanedione) with a diamine (thiosemicarbazide or semicarbazide). Copper(II) complexes of these ligands have been synthesized and characterized by elemental analysis, molar conductance, magnetic susceptibility, i.r., u.v.–vis, ¹H-n.m.r., mass and e.p.r. spectral studies. Mass, n.m.r. and i.r. data indicate the condensation of the diamine and diketone and the whole molecular ion structure. g-Values are calculated for all of the complexes in polycrystalline form as well as in DMSO solution. Spin Hamiltonian values and bonding parameters have also been calculated which indicates that an unpaired electron is present in the orbital. The metal-ligand bonding parameters shows strong in-plane σ sigma and in-plane π bonding. The magnetic and spectral data indicate tetragonal geometry for all of the complexes except [CuH₂L⁴]Cl₂ and [CuH₂L⁴]Cl₂ which are square planar. From c.v. data reversible Cu^II/Cu^I couples are observed for these complexes. The macrocyclic complexes show more antibacterial and antiviral activity as compared to the ligands. The antibacterial activities of the compounds were tested against S. aureus, S. subtillis and E. coli.     

Spectral studies of metal complexes of a new type of bis(thiosemicarbazone)

Cobalt(II), nickel(II) and copper(II) complexes of two new bis(di-2-pyridyl ketone) dithiosemicarbazones have been prepared in EtOH solution and characterized by physical and spectral methods. The bis(di-2-pyridyl ketone) dithiosemicarbazones were prepared from dithiosemicarbazides derived from piperazine and N,N-dimethylethylenediamine. N.m.r., i.r., and electronic spectra of the dithiosemicarbazones and their complexes along with e.s.r. spectra of the copper(II) complexes have been recorded. The complexes are bi-, tri- and tetranuclear and involve the dithiosemicarbazones coordinating as dianionic, anionic and neutral ligands.