Copper(II) complexes of 2-formyl-, 6-methyl-2-formyl- and 2-benzoylpyridine N(4)-(2-methylpyridinyl)-,N(4)-(2-ethylpyridinyl)-and N(4)-methyl(2-ethylpyridinyl)thiosemicarbazones

Summary The title complexes of general formula [Cu(HL)Cl₂] or [Cu(L)Cl] have been isolated and characterized by ¹H and ¹³C-n.m.r., i.r. and electronic spectra. The i.r., electronic and e.s.r. spectral data for the Cu^II complexes are compared with those of previously studied complexes. The antitumour and antiviral activities of the thiosemicarbazones and their complexes are discussed.     

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) complexes of 6-methyl-2-acetylpyridine N(4)-substituted thiosemicarbazones

Summary Copper(II) complexes of 6-methyl-2-acetylpyridine N(4)-substituted thiosemicarbazones, coordinated either as a neutral or a monoanionic ligand, have been prepared and characterized. I.r., electronic and e.p.r. spectra of the complexes, as well as¹H- and¹³C-n.m.r. spectra of the thiosemicarbazones, have been recorded. Both the thiosemicarbazones and their copper(II) complexes show either modest or no growth inhibitory activity againstAspergillus niger, but theN(4)-dialkyl- and 3-azacyclo-derivatives, and particularly their copper(II) complexes, have considerable activity againstPaecilomyces variotii.     

Nickel(II) complexes of 2-aminoacetophenone N(4)-substituted thiosemicarbazones

Mononuclear nickel(II) complexes with 2-aminoacetophenone thiosemicarbazones and three N(4)-substituted thiosemicarbazones have been prepared in EtOH solution and characterized by physical and spectral methods. I.r. and electronic spectra of the thiosemicarbazones and their complexes, along with physical properties of the complexes, have been obtained. The 2-aminoacetophenone thiosemicarbazones coordinate both as neutral and anionic ligands via the thiosemicarbazone moiety's azomethine nitrogen and thione/thiolato sulfur [on loss of the N(2) hydrogen].     

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

Nickel(II) complexes with five 4-acetamidobenzaldehyde N(4)- substituted thiosemicarbazones have been prepared in EtOH solution and characterized by physical and spectral methods. N.m.r., i.r. and electronic spectra of the thiosemicarbazones and their complexes, along with physical properties of the complexes, have been recorded. These thiosemicarbazones coordinate as anionic ligands via the thiosemicarbazone moiety's azomethine nitrogen and thiolate sulfur [upon loss of the N(2) hydrogen] when reacted with NiCl2 in the presence of Et3N or with Ni(OAc)2.     

Copper(II) complexes of thiosemicarbazones derived from 2-acetylpyridine and its n-oxide

A series of Cu(II) complexes of the thiosemicarbazone, 3-azabicyclo[3.2.2]-nonene-3-thiocarboxylic acid 2-[1-(2-pyridinyl)ethylidene]hydrazide(HL) and the corresponding N-oxide (HLO) have been prepared and characterized. Both ligands undergo deprotonation and appear to coordinate via the thione sulfur, the imine nitrogen and the pyridyl nitrogen (or N-oxide oxygen). A single anionic ligand such as Cl^?, Br^?, NCS^? and N^?₃ completes the bonding to the Cu(II) center of these 4-coordinate complexes. When the complexes are prepared using Cu(II) perchlorate, the solids isolated contain a neutral thiosemicarbazone ligand as well as the deprotonated ligand. The solids are primarily characterized by IR, electronic and electron spin resonance spectroscopy. In addition, electronic and ESR spectra of their chloroform solutions were recorded. Most of the solids (except the nitrates) were unaltered upon dissolution. Simulation of the solution ESR spectra was used to estimate the coupling constants of the various coordinated nuclei.     

Characterization of copper(II) complexes of N4,N4-disubstituted thiosemicarbazones of 2-acetylpyridine by combined evaluation of electronic and ESR parameters

Copper(II) complexes of 2-acetylpyridine 4,4-dimethyl-3-thiosemicarbazone (L′H) and 2-acetylpyridine 4-(4-methylpiperidinyl)-3-thiosemicarbazone (LH) of the general formula CuLX (where L is a deprotonated ligand and X = F⁻, Cl⁻, Br⁻, I⁻, OAc⁻ and NO⁻₃) have been synthesized and characterized by elemental analysis, magnetic susceptibility measurements between 93 and 298 K in the polycrystalline state, i.r. spectra, electronic spectra, conductivity measurements and ESR spectra recorded in the polycrystalline state, in chloroform and dimethylformamide solution at room temperature and at 77K. The molar conductivities measured in dimethylformamide for all complexes show them to be non-electrolytes. The terdentate character of the ligands in all the complexes is inferred from i.r. spectral studies. The i.r. spectra also confirm the monodentate nature of the polyatomic anions such as nitrate and acetate. The electronic spectra in Nujol mulls, chloroform or dimethylformamide solution suggest planar geometry for all of the complexes. The calculated ESR parameters show an axial d_x²−y² ground state and suggest coordination through sulphur in agreement with the i.r. results. Little change in the value of g with temperature indicates no significant change in planarity of these four coordinated species. ESR spectra in solution at room temperature and 77 K also suggest a strong covalent environment with strong in-plane sigma and pi bonds provided by the ligands.     

Transition metal ion complexes of thiosemicarbazones derived from 2-acetylpyridine. Part 6. The chemical and antifungal properties of 2-acetylpyridine4 N-diethyl- and4 N-dipropylthiosemicarbazones and their copper(II) complexes

Summary Complexes of stoichiometry [CuLX] where X=Cl, Br and L=2-acetylpyridine⁴ N-diethyl- and⁴ N-dipropylthiosemicarbazone, HL4DE and HL4DP, respectively, have substantially more activity againstAspergillus niger andPaecilomyces variotii than the uncomplexed thiosemicarbazones. Spectral data (i.e., i.r., u.v.vis., and e.s.r) of the complexes are presented along with thermodynamic data for the thiosemicarbazones.     

Transition metal ion complexes of thiosemicarbazones derived from 2-acetylpyridine. Part 1. The4N-methyl derivative

Summary A series of metal ion complexes of the thiosemicarbazone,N-methyl-2[1-(2-pyridinyl)ethylidene]-hydrazinecarbothioamide (HL4M) has been prepared and spectrally characterized. HL4M coordinates either as a neutral bidentate ligand (i.e., pyridyl N and imine N) or as deprotonated tridentate ligand (i.e., pyridyl N, imine N and thiol sulphur). The cobalt(II) salts yield hexacoordinated cobalt(III) cations, and an isoelectronic species, [Ni(L4M)₂], has been formed from Ni(C₂H₃O₂)₂. The remaining nickel(II) complexes involve the neutral ligand, as do two of the three copper(II) complexes. HL4M possesses a weaker ligand field and has less covalency in its bonding than related thiosemicarbazones that possess anN-dialkyl-function.     

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.     

Nickel(II)-triphenylphosphine complexes of ONS and ONN chelating 2-hydroxyacetophenone thiosemicarbazones

The complexes [Ni(L¹)(PPh₃)] (1) and [Ni(L²)(PPh₃)]·HCl (2) were synthesized by the reaction of [Ni(PPh₃)Cl₂] and dibasic 2-hydroxyacetophenone-S-R-4-R¹-thiosemicarbazones (R/R¹: H/CH₃, L¹H₂; CH₃/H, L²H₂). The ligands and the complexes were characterized using elemental analysis, IR and ¹H NMR spectra. In both complexes, the thiosemicarbazone ligands coordinate to nickel(II) by giving two protons. Complex 1 is formed through the phenolate oxygen, azomethine nitrogen and sulfur atoms of L¹ and the P atom of a triphenylphosphine ligand. In complex 2, L² is functional through an ONN donor set, containing a thioamide nitrogen instead of a sulfur atom. X-ray analysis indicated distorted square planar structures for the complexes, and the nickel atoms lie slightly above the planes structured by the donor atoms. In the crystal forms of 1 and 2, some phenyl ring protons of the phosphine ligand give intramolecular hydrogen bonds with the donor atoms of the thiosemicarbazone moiety, namely the phenolate oxygen (in complexes 1 and 2) and N⁴ nitrogen (in complex 2).     

Copper complexes of pyridine 2-aldehyde and 2-acetylpyridine thiosemicarbazones

Copper complexes of two heterocyclic thiosemicarbazones were synthesized and characterized by magnetic-moment measurement, and ESR and IR spectroscopy. Implications of the magnetic and spectral data in relation to the structures of the complexes are discussed.     

Transition metal ion complexes of thiosemicarbazones derived from 2-acetylpyridine. Part 8. The chemical and antifungal properties of the nickel(II) complexes of 2-acetylpyridine4 N-diethyl- and4 N-dipropylthiosemicarbazones

Summary Nickel(II) complexes of 2-acetylpyridine⁴ N-diethyl- and⁴ N-dipropylthiosemicarbazone show less activity againstAspercallus niger than the free thiosemicarbazones. However, againstPaecilomyces variotii the nickel(II) complexes possess comparable activity at high concentrations and are more active at lower concentrations. Spectral and thermal information about the nickel(II) complexes, which coordinate the anionic thiosemicarbazone ligands in a tridentate manner, is included.     

Transition metal ion complexes of thiosemicarbazones derived from 2-acetylpyridine. Part 9. The chemical and antifungal properties of the iron(III) and cobalt(II,III) complexes of 2-acetylpyridine4 N-diethyl-and4 N-diopropylthiosemicarbazones

Summary ⁴ N-diethyl- and⁴ N-dipropylthiosemicarbazones of 2-acetylpyridine coordinate to Fe^III, Co^III and Co^II centres as tridentate NNS ligands. Spectral and physical data indicates that the size of the⁴ N-substituents can influence the stereochemistry and stoichiometry of the complexes, which show minimal ability to inhibit fungal growth and are considerably less active than the related copper(II) and nickel(II) complexes.     

The structure,magnetic and spectral properties of 4-acetylpyridine N-oxide complexes of copper(II) propionates

The synthesis and characterization of CuX₂L; (X = CH₃CH₂COO^?, ClCH₂CH₂COO^?, CH₃CHClCOO^? or CH₃CCl₂COO^?; and L = 4-acetylpyridine N-oxide) is reported. The characterization of these compounds was based on electronic, infrared and EPR spectra, as well as magnetic measurements over the temperature range. Several correlations between the spectral and magnetic data as well as pK_a values of the respective acids were found and discussed. On the basis of spectral and magnetic data the structures of the compounds are discussed.     

Spectral studies of iron(III) complexes of substituted thiosemicarbazones of 2-acetylpyridine

Summary Iron(III) complexes of four substituted thiosemicarbazones of 2-acetylpyridine of general. formula [FeL₂]ClO₄ (where L is a deprotonated ligand) have been synthesised and characterised by elemental analyses, magnetic susceptibility measurements in the polycrystalline state at room temperature, i.r. spectra, electronic spectra and e.s.r. spectra recorded in polycrystalline state, in methanol solution at room temperature and at 77 K. All the complexes are 1:1 electrolytes. The ligands coordinate via the pyridine nitrogen, imine nitrogen and thione sulphur. E.s.r. spectra and with magnetic studies suggest a spin-paired configuration for the iron(III) complexes.Author to whom all correspondence should be directed     

Spectral and biological studies of copper(II) complexes of 2-acetyl-pyridine thiosemicarbazones with bulky 4N-substituents

Summary Copper(II) complexes of a large number of 2-acetylpyridine ⁴N-alkyl thiosemicarbazones were prepared and characterized. I.r., electronic and e.s.r. spectra of the complexes, as well as ¹H and ¹³C n.m.r. spectra of the thiosemicarbazones, were obtained. Both the thiosemicarbazones and their complexes show either modest or no growth inhibitory activity against Aspergillus niger, but many have considerable activity against Paecilomyces variotii. There is a relationship between the antifungal activity and size of the ⁴N-substituent for both the thiosemicarbazones and their copper(II) complexes.     

Nickel(II) and copper(II) complexes of 2-(2-pyridyl)benzimidazole: synthesis and structural characterization

2-(2-Pyridyl)benzimidazole (PBI) was synthesized by solvent-free aldol condensation and complexed with nickel(II) and copper(II) nitrate and perchlorate salts by simple reactions at room temperature. The transition metal complexes [Ni(PBI)₂NO₃](NO₃) (1), [Ni(PBI)₃](ClO₄)₂·1.5H₂O (2), [Cu(PBI)₂NO₃](NO₃) (3), and [Cu(PBI)₃](ClO₄)₂·3H₂O (4) (PBI = 2-(2-pyridyl)benzimidazole) were synthesized in good yield and structurally characterized by X-ray crystallography, infrared absorption spectroscopy, and elemental analysis. Complexes 1 and 3 are isostructural, crystallizing in the same space group P2₁/c. Both the nickel(II) and copper(II) atoms have distorted square pyramidal geometries. The metal centers in these complexes are coordinated by two molecules of the bidentate ligand (PBI) and an O-atom of the coordinated nitrate anion. Complexes 2 and 4 are also isostructural but do not crystallize in the same space group: P-1 for 2 and Pccn for 4. The geometry around both the nickel(II) and the copper(II) centers is distorted octahedral. Here, the metal atoms are coordinated by three molecules of 2-(2-pyridyl)benzimidazole. The copper(II) complex 4 has 2-fold symmetry with one of the three PBI ligands being positionally disordered about the 2-fold axis. Intermolecular N–H···O hydrogen bonds, involving the NH H-atom and an O-atom of the coordinated nitrate anion, are observed in all four complexes. In 1 and 3, this gives rise to the formation of centrosymmetric dimer-like structures that are decorated by hydrogen-bonded nitrate anions. In 2 and 4 the perchlorate anions and the water molecules of crystallization are involved in N–H···O and O–H···O hydrogen bonds bridging two symmetry-related cations, thus forming cyclic arrangements. In the case of complex 4, this leads to the formation of two-dimensional hydrogen-bonded networks parallel to plane (011). Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Copper(II) complexes of 2-aminoacetophenone N(4)-substituted thiosemicarbazones

Mononuclear copper(II) complexes with 2-aminoacetophenone thiosemicarbazone and three N(4)-substituted thiosemicarbazones have been prepared in ethanolic 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 ¹H- and ¹³C-n.m.r. spectra of the thiosemicarbazones, have been obtained. The 2-aminoacetophenone thiosemicarbazones coordinate as neutral ligands via the thiosemicarbazone moiety's azomethine nitrogen and thione sulfur, except for the piperidylthiosemicarbazone, which undergoes deprotonation and coordinates via the thiolato sulfur, as well as through the azomethine nitrogen. Complexes formed in the presence of triethylamine also form complexes with the anionic form of these thiosemicarbazones.     

Electrochemical studies of transition metal complexes of 2-acetyl-pyridine thiosemicarbazones. Part 2. Correlations with spectral and antifungal properties of copper(II) complexes of 2-acetylpyridine 3-azacyclothiosemicarbazones

The electrochemical behaviour of a series of copper(II) complexes of 2-acetylpyridine 3-azacyclothiosemicarbazones is reported. The complexes undergo a quasireversible one electron reduction in the range −0.400 to −0.450 Vversus Ag/AgCl, attributable to the copper(II)/-copper(I) redox couple. The electrochemical, as well as spectral characteristics of these complexes, can be correlated with their antifungal activity againstAspergillus niger, Paecilomyces variotti, Penicillum rubrum andAspergillus terreus.