Transition metal ion complexes of thiosemicarbazones derived from 2-acetylpyridine. Part 7. Chemical and antifungal properties of 2-acetylpyridine4 N-ethylthiosemicarbazone and its metal complexes

Summary Spectral and thermal information, as well as activity againstAspergillus niger, have been obtained for 2-acetylpyridine⁴ N-ethylthiosemicarbazone and its iron(III), cobalt(II,III), nickel(II) and copper(II) complexes.     

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.     

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 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.     

Transition metal ion complexes of thiosemicarbazones derived from 2-acetylpyridine. Part 2. The4 N-dimethyl derivative

Summary Metal ion complexes of the thiosemicarbazone,N-dimethyl-2-[1-(2-pyridinyl)ethylidene]hydrazinecarbothioamide (HL4DM) have been prepared and characterized spectrally. HL4DM coordinates primarily as the deprotonated tridentate ligand (i.e., pyrïdylN, azomethineN, and thione sulphur). In contrast to related thiosemicarbazones, oxidation to cobalt(III) does not occur during complex formation with cobalt(II) halides. Oxidation does occur on reflux with ethanolic Co(BF₄)₂, but we isolated a planar cobalt(II) complex as well. Only with the tetrafluoroborate salts of cobalt(II) and nickel(II) are complexes isolated containing the neutral thiosemicarbazone. Square planar [Ni(L4DM)X]complexes where X=Cl, Br, and OH have been isolated and e.s.r. spectra of a 1% Cu/Ni complex are compared to the results of other workers.     

Transition metal ion complexes of thiosemicarbazones derived from 2-acetylpyridine. Part 4. The 3-piperidinyl derivative

Summary Metal ion complexes of the thiosemicarbazone, 3-piperidinyl-3-thiocarboxylic acid-2-[1-(2-pyridyl)ethylidene]hydrazide (HLpip) have been prepared and spectrally characterized. HLpip coordinates both as the deprotonated ligand (i.e., pyridylN, azomethineN, and thione sulphur) and the neutral ligand (i.e., pyridylN and azomethineN) with the sulphur possibly weakly coordinating in [Ni(HLpip)₂](BF₄)₂. All three preparative cobalt(II) salts yielded cobalt(III) cationic complexes. The nickel(II) and copper(II) chloride salts gave [M(Lpip)Cl] solids while complexes involving the neutral ligand were prepared with the corresponding bromide salts. Significant differences in the spectral properties of the various complexes are observed when compared to other thiosemicarbazones prepared from 2-acetylpyridine.     

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.     

Electrochemical studies of copper(II) 2-acetylpyridine4 N-dialkylthiosemicarbazones. Relation to their spectral,magnetic, and biological properties

Summary Quasireversible copper(II)/copper(I) couples are observed for [Cu(L)X], where X=Cl or Br, and L=an anion of a 2-acetylpyridine⁴ N-dialkylthiosemicarbazone. Irreversible reduction potentials of the tridentate (NNS) ligands increase as the size of the⁴ N-dialkyl-substituent increases. The growth inhibitory activity of the complex againstPaecilomyces variotii (but not other fungi tested) also decreases with increasing ligand size, suggesting that ease of ligand reduction is a significant factor in activity against this fungus.     

Transition metal ion complexes of thiosemicarbazones derived from 2-acetylpyridine. Part 3. The 3-hexamethyleneimine derivative

Summary Metal ion complexes of the thiosemicarbazone, 3-hexamethyleneimine-3-thiocarboxylic acid-2-[1-(2-pyridyl)-ethylidene]hydrazide (HLhexim) have been prepared and spectrally characterized. HLhexim coordinates primarily as the deprotonated tridentate ligand (i.e., pyridylN, azomethineN, and thione sulphur). The air oxidised cobalt(III) complex, [Co(LHexim)₂] (BF₄), was isolated from the preparation with cobalt(II) tetrafluoroborate, but other cobalt(II) salts yielded tetrahedral cobalt(II) compounds. Planar nickel(II) and copper(II) complexes were isolated from preparations with halide salts. Significant differences in the spectral properties of the various complexes are observed when compared to other thiosemicarbazones prepared from 2-acetylpyridine.     

Metal ion complexes of 2-picolinamineN-oxide

Summary A series of cobalt(II), nickel(II) and copper(II) complexes of 2-picolinamineN-oxide, HA, has been prepared. Solids of formula [M(HA)₃](BF₄)₂ (M=cobalt(II) or nickel(II); [Cu(HA)₂]X₂ (X=BF ₄ ^– , NO ₃ ^– ); [Co(HA)₂X₂] (X=Cl^– or Br^–); [Ni(HA)₂Cl₂] and [Cu(HA)X₂] (X=Cl^– or Br^–] have been isolated and characterized by partial elemental analyses, molar conductivities, magnetic susceptibilities, DSC-TGA, and spectral methods. All complexes were found to be monomeric, and their spectral parameters are compared with those of the metal ion complexes ofN-alkyl-2-picolinamineN-oxides, 2-dialkylaminopyridineN-oxides and 2-picolinamine. The cobalt(II) and nickel(II) halide complexes spectrally show a mixture of octahedral and tetrahedral centres.     

Transition metal ion complexes of theS-methyldithiocarbazate prepared from 2-acetylpyridine

Summary Metal ion complexes of 2-acetylpyridineS-methyldithiocarbazate, HNNS, have been prepared and spectrally characterised. Preparations in EtOH yield complexes in which the deprotonated ligand, NNS, is complexedvia its pyridyl nitrogen, azomethine nitrogen, and thione sulphur. The stoichiometries are: [M(NNS)₂]X (M=Fe³⁺, Co³⁺ and X=ClO ₄ ^– , [FeCl₄]^–, BF ₄ ^– , 1/2 [CoCl₄]^2– and 1/2 [CoBr₄]^2–), [M(NNS)X] (M=Ni²⁺, Cu²⁺ and X=Cl^–, Br^–), [Cu(NNS)H₂O]BF₄ and Ni(HNNS)(NNS)F(EtOH)]BF₄. The spectral (i.e., i.r., u.v.-vis.-n.i.r. and e.s.r.) and physical properties of these complexes are compared to those of theS-methyldithiocarbazates of 2-formylpyridine and 2-acetylpyridineN-oxide, as well as the related thiosemicarbazones prepared from 2-acetylpyridine. Thermal studies of the nickel(II) complexes indicate that the nature of thermal decomposition of coordinated NNS is different from that of HNNS.     

Metal ion complexes of 2-acetylpyridine 3-(4-methyl)piperazinyl-thiosemicarbazone

Metal complexes of stoichiometries, [M(HLppz4M)X₂] and [M(Lppz4M)X], are formed from nickel(II) and copper(II) halides and 2-acetylpyridine 3-(4-methyl)piperizinylthiosemicarbazone, HLppz4M. The [M(Lppz4M)X] complexes involve tridentate N(pyridyl), N(azomethinyl) and S(thiolate) coordination with a halo ligand completing the bonding. Neutral HLppz4M coordinatesvia the two nitrogen donors. Spectral evidence indicates the presence of a thiol hydrogen in Hppz4M complexes, the first to be reported for a coordinated thiosemicarbazone.     

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.     

Structural and spectral studies of di-2-pyridyl ketone N(4)-methyl- and N(4)-dimethylthiosemicarbazone and their metal complexes

Cobalt(II), nickel(II) and copper(II) complexes of di-2-pyridyl ketone N(4)-methyl- and N(4)-dimethylthiosemicarbazone have been prepared and characterized by physical and spectral methods. Use of different ligand-to-metal chloride molar ratios in the preparation of the complexes has produced both mononuclear and polynuclear species for the three metal ions. Crystal structures of the uncomplexed di-2-pyridyl ketone N(4)-methylthiosemicarbazone and a nickel(II) complex, di-2-pyridyl ketone N(4)-dimethylthiosemicarbazone, have been determined and aid the assignments of the i.r., n.m.r., u.v.–vis.–n.i.r. and e.s.r. spectra.     

Synthesis,structure and bioactivity of Ni2+ and Cu2+ acylhydrazone complexes

Two acylhydrazone complexes, bis{6‐methyl‐N′‐[1‐(pyrazin‐2‐yl‐κN¹)ethylidene]nicotinohydrazidato‐κ²N′,O}nickel(II), [Ni(C₁₃H₁₂N₅O)₂], (I), and di‐μ‐azido‐κ⁴N¹:N¹‐bis({6‐methyl‐N′‐[1‐(pyrazin‐2‐yl‐κN¹)ethylidene]nicotinohydrazidato‐κ²N′,O}nickel(II)), [Cu₂(C₁₃H₁₂N₅O)₂(N₃)₂], (II), derived from 6‐methyl‐N′‐[1‐(pyrazin‐2‐yl)ethylidene]nicotinohydrazide (HL) and azide salts, have been synthesized. HL acts as an N,N′,O‐tridentate ligand in both complexes. Complex (I) crystallizes in the orthorhombic space group Pbcn and has a mononuclear structure, the azide co‐ligand is not involved in crystallization and the Ni²⁺ centre lies in a distorted {N₄O₂} octahedral coordination environment. Complex (II) crystallizes in the triclinic space group P and is a centrosymmetric binuclear complex with a crystallographically independent Cu²⁺ centre coordinating to three donor atoms from the deprotonated L^? ligand and to two N atoms belonging to two bridging azide anions. The two‐ and one‐dimensional supramolecular structures are constructed by hydrogen‐bonding interactions in (I) and (II), respectively. The in vitro urease inhibitory evaluation revealed that complex (II) showed a better inhibitory activity, with the IC₅₀ value being 1.32±0.4 µM. Both complexes can effectively bind to bovine serum albumin (BSA) by 1:1 binding, which was assessed via tryptophan emission–quenching measurements. The bioactivities of the two complexes towards jack bean urease were also studied by molecular docking. The effects of the metal ions and the coordination environments in the two complexes on in vitro urease inhibitory activity are preliminarily discussed.     

Transition metal ion complexes of thiosemicarbazones derived from 2-acetylpyridineN-oxide. Part IV. Iron(III) and copper(II) complexes of the4 N-ethyl- and4 N-diethylthiosemicarbazones

Summary Copper(II) and iron(III) complexes of 2-acetylpyridineN-oxide⁴ N-ethyl- and⁴ N-diethylthiosemicarbazones have been prepared and characterized by physical and spectral methods. The⁴ N-ethyl-derivative coordinates as a neutral, bidentate ligand with copper(II), and the⁴ N-diethyl- as an anionic, tridentate ligand with both copper(II) and iron(III). The former ligand forms a mixed ligand complex (i.e., one neutral and one anionic ligand) with iron(III).     

Nickel(II) and copper(II) complexes of 2-acetylpyridine 4 N-(2-methylpyridinyl)-, 4 N-(2-ethylpyridinyl)- and 4 N-methyl(2-ethylpyridinyl) thiosemicarbazones

Summary Ni^II and Cu^II complexes of 2-acetylpyridine ⁴ N-(2-methylpyridinyl)-, ⁴ N-(2-ethylpyridinyl)- and ⁴ N-methyl(2-ethylpyridinyl) thiosemicarbazones (HL4pam, HL4pae, and HL4Mpae, respectively) of general formula [M(HL)X₂] have been isolated from boiling EtOH and characterized by physico-chemical and spectroscopic methods. The growth inhibition activities of the thiosemicarbazones and their complexes were measured against Aspergillus nicer and Paecilomyces variotii.     

Molecular structure and spectral properties of bromo(2-acetylpyridine4 N-methylthiosemicarbazonato)copper(II)

Summary The anion (loss of³ N hydrogen) of 2-acetylpyridine⁴ N-methylthiosemicarbazone coordinates in a planar conformation to copper(II) through the pyridyl nitrogen, azomethine nitrogen and thiolato sulphur atoms. The fourth coordination site is occupied by a bromo ligand and the complex is mononuclear and essentially planar. Bond distances and angles, as well as solid state and solution spectral properties, are compared to other recently reported copper(II) thiosemicarbazone complexes.     

Acetate and acetamide complexes of [Ni(Me4[12]aneN4)]PF6: a tale of two ligands

Although there are many examples of acetate complexes, acetamide complexes are virtually unknown. A side‐by‐side comparison in (acetato‐κ²O,O′)(1,4,7,10‐tetramethyl‐1,4,7,10‐tetraazacyclododecane‐κ⁴N)nickel(II) hexafluoridophosphate, [Ni(C₂H₃O₂)(C₁₂H₂₈N₄)]PF₆, (1), and (acetamidato‐κ²O,O′)(1,4,7,10‐tetramethyl‐1,4,7,10‐tetraazacyclododecane‐κ⁴N)nickel(II) hexafluoridophosphate, [Ni(C₂H₄NO)(C₁₂H₂₈N₄)]PF₆, (2), shows the steric equivalence between these two ligands, suggesting that acetamide could be considered as a viable acetate replacement for electronic tuning.     

Metal complexes of 2-acetylpyridine N(4)-dihexyl- and N(4)-dicyclohexylthiosemicarbazones

Summary 2-Acetylpyridine N(4)-dihexyl- and N(4)-dicyclohexylthiosemicarbazone, HAc4DHex and HAc4DCHex, respectively, and Fe^III, Co^II, Co^III, Ni^II, Cu^II and Zn^II complexes have been prepared and characterized by molar conductivities, magnetic susceptibilities and spectroscopic techniques. For many of the complexes, loss of the N(2)H hydrogen occurs, and the ligands coordinate to the metal centres as NNS monoanionic, tridentate ligands, e.g., [M(NNS)X] (M = Co^II, Ni^II, Cu^II, NNS = Ac4DHex or Ac4DCHex and X = Cl or Br), [Fe(NNS)₂]ClO₄, [Co(NNS)₂]BF₄, [Cu(NNS)NO₃] and [Zn(NNS)OAc]. Zn^II ion is also chelated by neutral ligands in [Zn(HNNS)X₂] (X = Cl, Br). In addition, [Ni(Ac4DHex)-(HAc4DHex)]X (X = BF₄, ClO₄) and [Ni(HAc4DCHex)₂]-(BF₄)₂ are reported where the neutral thiosemicarbazone is coordinated via the pyridyl nitrogen, azomethine nitrogen and thione sulfur. Crystal structure determinations of HAc4DCHex and [Cu(Ac4DHex)Br] show the former to contain the bifurcated hydrogen bonded form and the latter to be planar with no significant interaction between neighbouring centres.