Trivalent chromium,manganese, iron and cobalt chelates of a tetradentate N6 macrocyclie ligand

Summary Trivalent chromium, manganese, iron and cobalt salts reactin situ with 2,6-diaminopyridine and acetylacetone to form complexes of the 16-membered N₆ tetradentate macrocyclic ligand. The chelates are characterised as distorted square-pyramidal of [M(TML)X] type, where M = chromium(III), manganese(III), iron(III) and cobalt(III); X=Cl, Br, NO₃ or NCS for chromium(III) and iron(III) and X=(OAc) for manganese(III) and (OH) for cobalt(III). The ligand coordinates through all the nitrogen atoms through deprotonation of two of them, however, the pyridine nitrogens do not take part in coordination. The chelates incorporate one anion or hydroxyl group in the coordination sphere. The magnetic, electronic and i.r. spectral studies indicate lower symmetries for these chelates. The amount of distortion is calculated in terms of DT/DQ by applying NSH theory. X-ray measurements on powder form of the complexes show their isomorphic nature and also support the proposed structures.     

Synthesis spectroscopic and biological approach in the characterization of novel [N<Subscript>4</Subscript>] macrocyclic ligand and its transition metal complexes

A novel tetradentate nitrogen donor [N₄] macrocyclic ligand, i.e. 1,3,4,8,9,11-hexaaza-2,10-dithia-5,12-dioxo-7,14-diphenyl-cyclotetradecane (L), has been synthesized. Manganese(II),cobalt(II), nickel(II) and copper(II) complexes with this ligand have been prepared and subjected to elemental analyses, molar conductance measurements, magnetic susceptibility measurements, mass, ¹H-n.m.r. (Ligand), i.r., electronic, and e.p.r. spectral studies. On the basis of molar conductance the complexes may be formulated as [M(L)X₂] [where M = Mn^II, Co^II, Ni^II, and Co^II,and X = Cl⁻ & NO ₃ ⁻ ] due to their nonelectrolytic nature in dimethylformamide (DMF). All the complexes are of the high spin type and are six coordinated. On the basis of i.r., electronic and e.p.r. spectral studies an octahedral geometry has been assigned to Mn^II, and ^II, ^II, complexes, and tetragonal for copper(II) complexes. The antimicrobial activities of the ligand and its complexes, as growth inhibiting agents, have been screened in vitro against several species of bacteria and plant pathogenic fungi.     

Spectral,physicochemical and biological characterization of 2,5,11,14,19,20-hexaaza-3,12-dimethyl-4,13-dipropyl-tricyclo [13.3.1.1(6-10)]cosane-1(19),2,4,6(20),7,9,11,13,15,17-decaene and its transition metal complexes

The synthesis of a tetradentate nitrogen donor macrocyclic ligand i.e. 2,5,11,14,19,20-hexaaza-3,12-dimethyl-4,13-dipropyl-tricyclo[13.3.1.1(6-10)]cosane-1(19),2,4,6(20),7,9,11,13,15,17-decaene and its complexes with manganese(II), cobalt(II), nickel(II) and copper(II) have been reported. The complexes were characterized by elemental analyses, molar conductance measurements, magnetic susceptibility measurements, mass, ¹H-n.m.r. (Ligand), i.r., electronic, and e.p.r. spectral studies. On the basis of molar conductance the complexes may be formulated as [M(L)X₂] [where M = Mn(II), Co(II), Ni(II) and Cu(II), and X = Cl⁻ & NO ₃⁻ ] due to their nonelectrolytic nature in dimethylformamide (DMF). All the complexes are of the high spin type and are six coordinated. On the basis of i.r., electronic and e.p.r. spectral studies an octahedral geometry has been deduced for Mn(II), Co(II) and Ni(II) complexes, and tetragonal geometry for Cu(II) complexes. The antimicrobial activities of the ligand and its complexes, as growth inhibiting agents, have been screened in vitro against several species of bacteria and plant pathogenic fungi.     

Five coordinated complexes of divalent nickel and copper with ligands derived from acid hydrazides and acetylacetone

Summary Picolinic acid hydrazide (PH) and isonicotinic acid hydrazide (INH) react with acetylacetone to form complexes, containing open chain tetradentate ligands, through anin situ process in the presence of nickel and copper salts. The complexes were isolated and characterised as five-coordinate with the aid of analyses, magnetic, e.s.r., electronic and i.r. spectral studies.Attempts to obtain the free ligand were unsuccessful, but its solid complexes can be isolated. Acetylacetonebispicolinoyl hydrazone Ac(PH)₂ coordinates through azomethine and pyridine nitrogen atoms while acetylacetonebisisonicotinoyl hydrazone Ac(INH)₂ does so through azomethine nitrogens and amido oxygen atoms, giving rise to complexes of the MAc(PH)₂X or MAc(INH)₂X type where X=Cl, Br, NO₃ or NCS and M=nickel(II) and copper(II). Magnetic, e.s.r. and electronic spectra are consistent with five coordinate geometries incorporating one anion on the axial positions. Various ligand field parameters have been calculated and the amount of distortion assessed in terms of DT/DQ. The metal-ligand vibrations in the far i.r. are discussed.     

Preparation and characterisation of copper,cobalt and nickel complexes of tetradentate N6 macrocyclic ligand

Macrocyclic complexes of copper, nickel and cobalt were synthesised via template reactions. These 14-membered N₆ tetradentate macrocyclic complexes were characterised by magnetic, conductance, electronic and IR spectral studies. The macrocyclic ligand coordinates through the four azomethine nitrogen atoms which are bridged by 2,3-butanedione, moieties, but far IR spectra suggest that the pyridine nitrogens are not coordinated. These macrocyclic complexes are considered to have distorted octahedral configurations.     

Synthesis,spectroscopic studies and biological screening of 18-membered octaazamacrocyclic complexes derived from acetonylacetone and thiocarbohydrazide

A series of the macrocyclic complexes is synthesized by condensation of acetonylacetone and thiocarbohydrazide in the presence of divalent metal salts in the methanolic medium. The complexes are of the type: [M(TML)X₂] where, M = Co(II), Ni(II), Cu(II), Zn(II) and Cd(II); X = Cl⁻ CH₃COO⁻ and TML is a tetradentate macrocyclic ligand. The complexes have been characterized with the help of various physicochemical techniques like elemental analyses, conductance measurements, magnetic measurements, NMR, infrared and electronic spectral studies. The low value of molar conductance indicates them to be non-electrolyte. On the basis of various studies a distorted octahedral geometry may be proposed for all the complexes. All the synthesized metal complexes were also tested for their in vitro antibacterial activities against some bacterial strains. The results obtained were compared with standard antibiotic: Ciprofloxacin. Some of the tested complexes shows good antibacterial activities against some bacterial strains.     

Template synthesis and characterization of N<Subscript>6</Subscript> 12-membered macrocyclic complexes derived from isatin and ethylenediamine

Novel series of complexes of the type [M(TML)X₂], where TML is a tetradentate macrocyclic ligand; M = Co(II), Ni(II), Cu(II), Zn(II); X = Cl⁻, NO₃⁻, CH₃COO⁻, have been synthesized by template condensation of isatin and ethylenediamine in the presence of divalent metal salts in a methanolic medium. The complexes have been characterized with the help of elemental analyses, conductance measurements, molecular weight determination, magnetic measurements, NMR, infrared and far infrared spectral studies. The low value of molar conductance indicates them to be nonelectrolytes. All the complexes are supposed to have distorted octahedral geometry. The text was submitted by the authors in English.     

Synthesis and spectroscopic characterization of transition metal complexes of a 12-membered tetraaza [N<Subscript>4</Subscript>] macrocyclic ligand and their biological activity

Cobalt(II), nickel(II) and copper(II) complexes are synthesized with 1,3,7,9-tetraaza- 4,6,10,12-tetraphenyl-2,8-dithiacyclododecane, a tetradentate ligand (L) and characterized by elemental analysis, molar conductance measurements, magnetic susceptibitity measurements, mass, i.r., electronic and e.p.r. spectral studies. All the complexes are non-electrolytes so they may be formulated as [M(L)X₂] [where, M = Co(II), Ni(II) and Cu(II) and X = Cl⁻ and NO ₃ ⁻ ]. All the complexes are of high spin type. On the basis of i.r., electronic and e.p.r. spectral studies an octahedral geometry has been assigned for Co(II) and Ni(II) complexes and tetragonal geometry for Cu(II) complexes. The antimicrobial activities of the ligand and its complexes, as growth inhibiting agents, have been screened in vitro against two different species of bacteria and plant pathogenic fungi.     

Template synthesis, spectroscopic studies and biological screening of macrocyclic complexes derived from thiocarbohydrazide and benzil

A novel series of complexes of the type [M(TML)X₂]; where TML is a tetradentate macrocyclic ligand; M = Co(II), Ni(II), Cu(II) or Zn(II); X = Cl⁻, CH₃COO⁻ or NO ₃ ⁻ have been synthesized by template condensation of benzil and thiocarbohydrazide in the presence of divalent metal salts in methanolic medium. The complexes have been characterized with the help of elemental analyses, conductance measurements, molecular weight determination, magnetic measurements, electronic, NMR, infrared and far infrared spectral studies. Electronic spectra along with magnetic moments suggest the six coordinate octahedral geometry for these complexes. The low value of molar conductance indicates them to be non-electrolytes. The biological activities of metal complexes have been tested in vitro against a number of pathogenic bacteria to assess their inhibiting potential.     

Physicochemical and Biological Characterization of Transition Metal Complexes with a Nitrogen Donor Tetra-dentate Novel Macrocyclic Ligand

A novel tetradentate nitrogen donor [N₄] macrocyclic ligand, i.e. 3,5,13,15,21,22-hexaaza-2,6,12,16-tetramethyl-4,14-dithia-tricyclo[15.3.1.1(7–11)]docosane-1(21),2,5,7,9,11(22),12,15,17,19-decaene, has been synthesized. Mn(II), Co(II), Ni(II) and Cu(II) complexes with this ligand have been prepared and subjected to elemental analyses, molar conductance measurements, magnetic susceptibility measurements, mass, ¹H-n.m.r. (Ligand), i.r., electronic, and e.p.r. spectral studies. On the basis of molar conductance the complexes may be formulated as [M(L)X₂] and [Ni(L)]X₂ [where M = Mn(II), Co(II) and Cu(II), and X = Cl⁻ and NO₃⁻] due to their nonelectrolytic nature in dimethylsulphoxide (DMSO). All the complexes are of the high spin type and are six coordinated. On the basis of i.r., electronic and e.p.r. spectral studies an octahedral geometry has been assigned to Mn(II) and Co(II), square planar for Ni(II) complexes, and tetragonal for Cu(II) complexes. The antimicrobial activities of the ligand and its complexes, as growth inhibiting agents, have been screened in vitro against several species of bacteria and plant pathogenic fungi.     

Copper(II) and nickel(II) complexes of schiff bases

Summary The isolation of complexes of some nickel(II) and copper(II) salts with the Schiff base derived from 2-aminobenzimidazole and 4-methylbenzaldehyde (abimbz) is reported. They are of the general type M(abimbz)₂X₂ (M=Ni or Cu; X=Cl, Br, or ClO₄). The compounds have been characterized by elemental analyses, conductivity measurements, i.r., electronic and e.p.r. spectral studies and magnetic measurements. The i.r. spectra show that the ligand is bidentate through the tertiary nitrogen of the imidazole ring and the exocyclic imine nitrogen. Possible structures for the complexes are suggested.     

A new binucleating ligand incorporating four oxime groups and its copper(II), manganese(II) and cobalt(III) complexes

A new binucleating ligand incorporating four oxime groups, butane-2,3-dione O-[4-aminooxy-2,3-bis-(2-hydroxyimino-1-methyl-propylideneaminooxymethyl)-but-2-enyl]-dioxime, (H₄mto), has been synthesized and its dinuclear cobalt(III), copper(II), and homo- and hetero-tetranuclear copper(II)–manganese(II) complexes have been prepared and characterized by ¹H- and ¹³C-n.m.r., i.r., magnetic moments and mass spectral studies. Elemental analyses, stoichiometric and spectroscopic data indicate that the metal ions in the complexes are coordinated to the oxime nitrogen atoms (C=N) and the data support the proposed structure for H₄mto and its complexes. Moreover, dinuclear cobalt(III) and copper(II) complexes of H₄mto have a 2:1 metal:ligand ratio.     

Studies on 2,6-diacetylpyridine bis(2-furoylhydrazone) complexes of bivalent 3d-metal ions

Summary The chelating behaviour of neutral and deprotonated 2,6-diacetyl-pyridine bis(2-furoylhydrazone), H₂dapf, has been investigated in some new complexes of oxovanadium(IV), manganese(II), cobalt(II), nickel(II), copper(II) and zinc(II). The hydrazone reacts with the metal salts to yield complexes of two types; the addition compounds [VO(H₂dapf)]SO₄, [M(H₂dapf)Cl]Cl and the deprotonated complexes [M(dapf)H₂O] [M=manganese(II), cobalt(II), nickel(II), copper(II) or zinc(II)] in neutral and alkaline media, respectively. The complexes have been characterized by elemental analyses, molar conductance, magnetic susceptibility, electronic, i.r. and e.s.r. studies and their stereochemistries are discussed.     

Synthesis,characterization and catalytic studies of iron(III), cobalt(II), nickel(II) and copper(II) complexes containing triphenylphosphine and β-diketones

A series of new β-diketonato complexes have been synthesized from the reactions of iron(III), cobalt(II), nickel(II) and copper(II) Ph₃P complexes with β-diketones (acetylacetone, benzoylacetone and dibenzoylmethane). All the complexes have been characterized by elemental analyses, spectral studies (i.r., electronic., magnetic., e.p.r., ¹H-n.m.r.) and cyclic voltammetry. The new complexes have been used as catalysts for aromatic coupling and oxidation reactions. Higher catalytic activity has been observed for the nickel(II) complexes compared to the other complexes.     

Macrocyclic ligands with potential axial interactions. The preparation of copper(II), nickel(II) and cobalt(III) complexes of 7,14-o-hydroxyphenyl-5,12-dimethyl-1,4,8,11-tetraazacyclotetradeca-4,11-diene

Summary The new macrocyclic ligand 7,14-o-hydroxyphenyl-5,12-dimethyl-1,4,8,11-tetraazacyclotetradeca-4,11-diene (1=L) has been prepared and complexes with copper(II), nickel(II) and cobalt(III) characterised. The nickel(II) complex is a yellow square-planar species, while the purple-red copper(II) complex is probably tetragonal in both the solid state and solution. The complexes appear to have an N-meso arrangement of the chiral nitrogen centres with the HOC₆H₄ groups occupying equatorial sites so that axial interactions with the metal do not occur. A variety oftrans-[CoLX₂]ClO₄ complexes (X=Cl, Br, NO₂, or N₃) have been characterised.     

N-(salicylidene)nitrosophenylglycine Schiff base as NOOO-donor towards transition metal ions

A new tetradentate NOOO-donor ligand, N-(salicylidene)nitrosophenylglycine (H₂snpg) has been designed, synthesized and structurally characterized. Copper(II), nickel(II), cobalt(II), manganese(II) and zinc(II) complexes of H₂snpg have been prepared for the first time. The authenticities of the ligand and its metal complexes have been established on the basis of elemental analyses, molar conductance measurements, magnetic properties, spectral (i.r., ¹H-n.m.r., u.v.–vis. and mass) studies. The i.r. spectral studies of all the complexes exhibit a similar feature about the ligating nature of the ligand to the metal ions and revealed that the ligand has coordinated through the carbonyl oxygen, azomethine nitrogen, nitroso oxygen and deprotonated hydroxyl oxygen. The molar conductance data suggest them to be non-electrolytes. The antimicrobial activity of all the compounds was studied against Escherichia coli, Bacillus cirroflagellosus, Aspergillus niger and Candida albicans. All the complexes have shown a moderate to high fungal activity compared to the ligand.     

Synthesis and characterization of nickel(II), cobalt(II), copper(II), manganese(II), zinc(II), zirconium(IV), dioxouranium(VI) and dioxomolybdenum(VI) complexes of a new Schiff base derived from salicylaldehyde and 5-methylpyrazole-3-carbohydrazide

Summary Synthesis of a new Schiff base derived from salicylaldehyde and 5-methylpyrazole-3-carbohydrazide, and its coordination compounds with nickel(II), cobalt(II), copper(II), manganese(II), zinc(II), zirconium(IV), dioxouranium(VI) and dioxomolybdenum(VI) are described. The ligand and the complexes have been characterized on the basis of analytical, conductance, molecular weight, i.r., electronic and n.m.r. spectra and magnetic susceptibility measurements. The stoichiometries of the complexes are represented as NiL · 3H₂O, CoL · 2H₂O, CuL, MnL · 2H₂O, ZnL · H₂O, Zr(OH)₂(LH)₂, Zr(OH)₂L · 2MeOH, UO₂L · MeOH and MoO₂L · MeOH (where LH₂ = Schiff base). The copper(II) complex shows a subnormal magnetic moment due to antiferromagnetic exchange interaction while the nickel(II), cobalt(II) and manganese (II) complexes show normal magnetic moments at room temperature. The i.r. and n.m.r. spectral studies show that the Schiff base behaves as a dibasic and tridentate ligand coordinating through the deprotonated phenolic.oxygen, enolic oxygen and azomethine nitrogen.     

The coordination chemistry of macrocyclic diamides. Transition metal complexes of 5,7-dioxo-1,4,8,11-tetraazacyclotetradecane

Summary A convenient preparation of the 14-membered macrocyclic diamide 5,7-dioxo-1,4,8,11-tetraazacyclotetradecane (LH₂) is described. The pK _NH ⁺ values of the ligand are pK₁ = 5.76 and pK₂ = 9.63 at 25° and I = 0.1 mol dm^–3 (KNO₃). With metal ions able to ionise amide hydrogens, the ligand acts as a planar quadridentate, L^2–. Thus copper(II) and nickel(II) give the neutral complexes ML, and conductivity measurements confirm that they are nonelectrolytes in aqueous solution. Both the nickel(II) and copper(II) complexes are acid labile unlike the analogues of 1,4,8,11-tetraazacyclotetradecane (cyclam).The cobalt(III) complex [CoL(NH₃)₂]Cl has been characterised and¹H n.m.r. measurements established the N-meso stereochemistry at the chiral nitrogen centres.     

4-Cyanoaniline complexes with transition metal(II) halides

Summary Coordination compounds formed by the interaction of manganese(II), cobalt(II), nickel(II) and copper(II) chloride and bromide with 4-cyanoaniline (4-CA) have been prepared and characterized by molar conductance, magnetic susceptibilities, electronic and i.r. spectral measurements down to 200 cm^–1 in the solid state. The isolated complexes are M(4-CA)₂X₂ except for nickel(II) bromide which is NI(4-CA)₄Br₂. I.r. spectra, indicate that 4-CA, though a potentially bidentate ligand, nevertheless acts only as a terminally aniline (NH₂) bonded monodentate ligand in all the complexes. Tentative stereochemistries of the complexes have been suggested in the solid state.     

Synthesis,structural characterization,and antibacterial studies of a tetradentate macrocyclic ligand and Its Co(II), Ni(II), and Cu(II) complexes

A novel macrocyclic tetradentate ligand 1,5,8,12-tetraaza-2,4,9,11-tetraphenyl-6,7:13,14-dibenzocyclohexadeca- 1,4,8,11-tetraene (L) has been synthesized. Cobalt(II), nickel(II), and copper(II) complexes of this ligand have been prepared and characterized by elemental analysis, molar conductance measurements, magnetic susceptibitity measurements, and mass, IR, electronic, and ESR spectral studies. The molar conductance measurements correspond to a nonelectrolytic nature for all the complexes, which can be formulated as [M(L)X₂] (where M = Co(II), Ni(II), and Cu(II); X = Cl⁻ and NO₃⁻). On the basis of IR, electronic, and ESR spectral studies, an octahedral geometry has been assigned to the Co(II) and Ni(II) complexes, whereas a tetragonal geometry was found for the Cu(II) complexes. The investigated compounds and uncomplexed metal salts and the ligands were tested against bacterial species like Sarcina lutea, Escherchia coli, and Staphylococcus aureus. The metal complexes have higher activity than the free ligand and metal salts. The text was submitted by the authors in English.