Synthesis, Spectral Characterization and Electrochemical Properties of New vic-dioxime Complexes Bearing Carboxylate

Three new vic-dioxime ligands, [N-(ethyl-4-amino-1-piperidine carboxylate)-phenylglyoxime (L¹H₂), N-(ethyl-4-amino-1-piperidine carboxylate)-glyoxime (L²H₂), and N,N′-bis(ethyl-4-amino-1-piperidine carboxylate)-glyoxime (L³H₂)], and their Co(II) with Cu(II) metal complexes, were synthesized for the first time. Mononuclear complexes of these ligands with a 1:2 metal-ligand ratio were prepared with Co(II) and Cu(II) salts. The BF₂⁺-capped Co(II) and mononuclear complexes of the vic-dioxime were prepared for [Co(L¹·BF₂)₂] and [Co(L²·BF₂)₂]. The ligands act in a polydentate fashion bonding through nitrogen atoms in the presence of a base, as do most vic-dioximes. The cobalt(II) and copper(II) complexes are non-electrolytes as shown by their molar conductivities (Λ_M) in DMF. The structures of the ligands and complexes were determined by elemental analyses, FT-i.r., u.v.–vis., ¹H- and ¹³C-n.m.r. spectra, magnetic susceptibility measurements, and molar conductivity. The comparative electrochemical studies show that the stabilities of the reduced or oxidized species and the electrode potentials of the complexes are affected by the substituents attached on the oxime moieties of the complexes.     

Synthesis and magneto-spectral investigations of some six and nine coordinated complexes of lanthanides(III) derived from 4[N-(2′-hydroxy-1′-naphthalidene) amino]antipyrinethiosemicarbazone

The present work describes the synthesis and characterization of some six and nine coordinated complexes of trivalent lanthanide(III) with 4[N-(2′-hydroxy-1′-naphthalidene)amino]antipyrinethiosemicarbazone (HNAAPTS). All the complexes have the general composition LnX₃.n(HNAAPTS) (X = NO₃ ^?, n = 1; X = NCS^? or ClO₄ ^?, n = 2). The complexes were characterized through elemental analyses, molar mass, conductivity measurements, magnetic susceptibilities, and infrared and electronic spectra. Infrared spectra revealed that HNAAPTS acts as a neutral tridentate (N,N,S) donor. The coordination number in these complexes is either six or nine depending on the nature of the anionic ligand.     

A new vic-dioxime ligand containing two azo substituents and its mononuclear nickel(II), cobalt(II), and copper(II) complexes; synthesis, characterization, spectroscopic and biological studies

A new vicinal dioxime ligand containing azo and thione chromophores, namely 1,3-bis[4-(phenyldiazenyl)phenyl]-2-thiooxaimidazoline-4,5-dione dioxime (bppH₂), was synthesized by the reaction of cyanogen di-N-oxide with N,N′-bis(4-phenylazophenyl) thiourea in dichloromethane solution at −10 °C. Mononuclear complexes of bppH₂ with nickel(II), cobalt(II), and copper(II) were synthesized. The complexes, [Ni(bppH)₂], [Cu(bppH)₂], and [Co(bppH)₂] were characterized by several techniques using elemental analyses, conductivity measurements, FT-IR, and electronic spectral studies. The data suggest that the ligand coordinates through the N,N atoms, as do most vic-dioximes. The molar conductivities in DMF solution indicate nonelectrolytic nature for the complexes. Antimicrobial activities of the ligand and its metal complexes were estimated for five bacteria, namely Klebsiella pneumoniae, Micrococcus luteus, Mycobacterium smegmatis, Enterobacter cloaca and Bacillus megaterium and three fungi, namely Candida albicans, Kluyveromyces marxianus, and Rhodotorula rubra.     

Synthesis,characterisation and antifungal activity of a series of Cobalt(II) and Nickel(II) complexes with ligands derived from reduced <Emphasis Type="Italic">N</Emphasis>, <Emphasis Type="Italic">N</Emphasis>′-<Emphasis Type="Italic">o</Emphasis>-Phenylenebis(Salicylideneimine)

The synthesis and characterisation by elemental analysis, conductivity, FTIR, UV–Visible, ESR and magnetic measurements are described for a series of complexes of nickel(II) and cobalt(II) with three ligands (H₂L^1–3) derived from reduced N, N′-o-Phenylenebis(salicylideneimine). The complexes formed are identified as neutral species, where the ligands are coordinated through N and O donor atoms. The formulae obtained for the complexes are: [CoL(H₂O)₂] with octahedral geometry and [NiL] with tetrahedral geometry. Their antifungal activity is evaluated towards human pathogenic fungi including yeasts of the Candida genus, some opportunistic moulds belonging to the Aspergillus, Scedosporium genus and some dermatophytes. The cobalt complexes show a significant growth inhibition of yeasts tested and also to fungi of the genus Scedosporium which is of interest because these fungi are usually poorly susceptible to current antifungal including Amphotericin B and Itraconazole, chosen as reference in this study. The activity data show that the metal complexes are more potent than the parent ligand.     

Synthesis and characterization of 2,3-bis(hydroxyimino)-1,2,3,4-tetrahydro-pyrido[2,3-b]pyrazine and its nickel(II), cobalt(II), copper(II), palladium(II), cadmium(II) and cobalt(III) complexes

Summary 2,3-Bis(hydroxyimino)-1,2,3,4-tetrahydro-pyrido[2,3-b]pyrazine (H₂L), prepared from 2,3-diaminopyridine and cyanogen-di-N-oxide has been converted into nickel(II), palladium(II), copper(II), cobalt(II), and cobalt(III) complexes (H₂L) with a 12 metal:ligand ratio. The ligands coordinate through the two N atoms, as do most vicinal dioximes. [(LH)Cl(H₂O)Cd], contains a six-membered chelate ring. [Co(HL)₂(L)Cl] has also been prepared using triphenylphosphine, triphenylarsine, thiophene and chloride as axial ligands. The structure of thevic-dioxime and its complexes are proposed on the basis of elemental analysis, i.r.,¹H-n.m.r. and uv-visible measurements.     

Structure and complexation equilibria of metal(II) ions with 4-arylazopyrazoles

Summary Octahedral mononuclear and tetrahedral binuclear 4-arylazo-3,5-diaminopyrazole complexes of copper(II), nickel(II), cobalt(II) and manganese(II) have been prepared and characterized by elemental analysis, conductivity measurements and by i.r., ¹H n.m.r. and electronic spectroscopy. Complexation equilibria, stoichiometry and stability constants were measured in 40% (v/v) EtOH-H₂O medium and I = 0.1 mol dm ⁻³ NaClO₄. In mild acidic media, the ligands behave as neutral NN′ bidentates, while in alkaline media they act as N²N₂′ tetradentate ligands.     

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 BF₂⁺-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.     

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.     

Complexing behaviour of aromatic thioamides (ArCSNHCOR). Transition metal complexes of N-carboethoxy-4-chlorobenzene- and N-carboethoxy-4-bromobenzene thioamide ligands

N-Carboethoxy-4-chlorobenzene thioamide (Hcct or HL) and N-carboethoxy-4-bromobenzene thioamide (Hcbt or HL) react with bivalent (Ni, Co, Cu, Ru, Pd and Pt), trivalent (Ru and Rh) and tetravalent (Pt) transition metal ions to give [M^II(L)₂], [Ru^III(L)₃], [Rh^III(L)(HL)Cl₂] and [Pt(L)₂Cl₂] complexes, respectively. In the presence of pyridine, Co^II and Ni^II salts react with the ligands (HL) to give [M^II(L)₂Py] (M = Co and Ni) complexes. Soft metal ions abstract sulphur from the ligands to yield the corresponding sulphide, together with oxygenated forms of the ligands. All the metal complexes have been characterised by chemical analyses, conductivity, spectroscopic and magnetic measurements.     

Synthesis,crystal structure and magnetic properties of the complex Co[Me<Subscript>2</Subscript>NC(S)NP(S)(OPr-<Emphasis Type="Italic">i</Emphasis>)<Subscript>2</Subscript>]<Subscript>2</Subscript>

The reaction of N-(diisopropoxyphosphorothioyl)-N′,N′-dimethylthiourea [Me₂NC(S)NHP(S)(OPr-i)₂, HL) potassium salt with Co(II) cation in aqueous ethanol gave the chelate complex Co(L-S,S′)₂(CoL₂). The structure of the resulting compound was studied by means of IR spectroscopy, microanalysis, and X-ray analysis. The metal center was found to occur in a tetrahedral S₄ environment formed by the C=S and P=S sulfur atoms of two deprotonated ligands L. Magnetic properties of the complex CoL₂ were also studied.     

Synthesis of N-(4′-Benzo[15-crown-5])thiophenoxyphenylaminoglyoxime and its complexes with some transition metals

4-(Chloroacetyl)diphenyl thioether (1) was synthesized from chloroacetyl chloride and diphenyl thioether in the presence of AlCl₃ as catalyst in a Friedel-Crafts reaction. Subsequently, its keto oxime (2) and glyoxime (3) derivatives were prepared. N-(4′-Benzo[15-crown-5]thiophenoxyphenylaminoglyoxime (H₂L) and its sodium chloride complex (H₂L · NaCl) were prepared from 4-(thiophenoxy)chlorophenylglyoxime (3), 4′-aminobenzo[15-crown-5] and sodium bicarbonate or sodium bicarbonate and sodium chloride. Ni(II), Co(II) and Cu(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 BF₂-capped Ni(II) mononuclear complex of the vic-dioxime was prepared. The macrocyclic ligands and their transition metal complexes were characterized on the basis of FT-IR, ¹H NMR, ¹³C NMR spectroscopy and elemental analyses data.     

Studies on mixed ligand complexes,part III. Cobalt(III) heterochelates derived fromN,N′-tetramethylenebis(salicylideneimine),N,N′-ethylenebis(acetylacetoneimine) and bidentate OO and ON donor ligands

Summary The hydroxoaquo complex, Co(OH)(H₂O)(salbn) [salbnH₂ =N,N-tetramethylcnebis(salicylideneimine)] reacts with bidentate OO and ON donor ligands in ethanol at 100° to give hetcrochelate complexes of the type Co(AA)(salbn) (where AA = bidentate monobasic ligands such as picolinic acid, acetylacetone, tropolone,N-benzoylphenylhydroxyl-amine, acetoacetanilide, salicylaldehyde and 2-hydroxy-l-naphthaldehyde). Thecis-diammineN,N-ethylenebis(acetyl-acetoneimine)cobalt(lll)chloride reacts with bidentate ligands such as tropolonc to form the heterochelate complex Co(tropolone)(baen) [where baenH₂ =N,N-ethylenebis(acetyl-acetoneimine)]. These newly synthesized complexes have been characterized by elemental analysis, i.r. and electronic spectroscopy, molecular weight, electrolytic conductance and magnetic susceptibility measurements. Electronic spectra suggest that Co(tropolo ne)(baen) reacts with pyridine.     

Synthesis and characterisation of cobalt(II), cobalt(III) and rhodium(III) complexes ofN,N′, N″, N‴-tetra(2-cyanoethyl) cyclam [TCEC] andN,N′, N″, N‴-tetra)3-aminopropyl) cyclam [TAPC]

Summary Complexes of cobalt(II), cobalt(III) and rhodium(III) with TCEC and TAPC have been synthesised. TCEC with cobalt(II) gave [Co(TCEC)Br]Br and [Co(TCEC)Cl]Cl, five coordinate high spin square pyramid complexes, but the corresponding cobalt(III) complex could not be characterised. Rhodium(III) gave a six coordinate [Rh(TCEC)Cl₂]Cl complex, in which the two coordinated chlorides have acis-geometry and the four pendant arms lie on one side of the N₄ plane with none of the —CN groups coordinated TAPC on the other hand gives the cobalt(III) complex, [Co(TAPC)Br]Br₂, in which one of the amino groups of the four pendant arms is coordinated to cobalt. Rhodium(III) with TAPC gave [Rh(TAPC)Cl]Cl₂ in which one axial site is occupied by the amino group of one of the pendant arms and the other by Cl^–.     

The synthesis and characterization of copper(II)–<Emphasis Type="Italic">p</Emphasis>-aminosalicylate complexes with diamine ligands

The complexes were synthesized by the reaction between sodium salt of p-aminosalicylic acid (PAS) and Cu(II) for 1 and corresponding ethylenediamine (en) or its derivatives for 2–6. The complexes were characterized by using elemental analyses, FT-IR, UV–Vis, magnetic moment measurements, and thermal analyses techniques. In complex 1[Cu₂(PA)₄(H₂O)₂], two Cu(II) ions were found as bridged by four μ-O:O′ p-aminosalicylato (PA) ligands, forming a cage structure, and two aqua ligands to form dinuclear square-pyramidal geometry around Cu(II) ions. In the complexes 2–6, the PA (anionic form of p-aminosalicylic acid) coordinated to Cu(II) ions as monodentate manner by using its oxygen atom of deprotonated carboxylic acid and ethylenediamine derivatives coordinated to the Cu(II) ions in bidentate manner to form mononuclear octahedral complexes [Cu(PA)₂(L)₂] (L = ethylendiamine, N,N-dimethylethylendiamine, N,N′-dimethylethylendiamine, N,N,N′,N′-tetramethylethylendiamine, and 1,3-propanediamine, for complexes 2, 3, 4, 5, and 6, respectively). In all the complexes OH and NH₂ groups of PA ligands were not coordinated to metals.     

Binuclear cobalt(II/II) and cobalt(II/III) chelates with O<Subscript>2</Subscript>N<Subscript>2</Subscript> ligands: synthesis,structure and magnetic studies

Abstract  The title complexes and have been synthesized in excellent yields by reacting Co(OAc)₂·4H₂O with H₂L¹ and H₂L², respectively, in acetonitrile solution. Here, [L¹]²⁻ and [L²]²⁻ are the deprotonated forms of N,N-bis(2-hydroxybenzyl)-N′,N′-dimethylethylenediamine and N,N-bis(2-hydroxybenzyl)-2-picolylamine, respectively. The crystal structures of and were determined by x-ray crystallography. In , each cobalt atom has distorted trigonal bipyramid geometry, while in , each cobalt atom has distorted octahedral geometry. Variable temperature magnetic moment measurements show weak antiferromagnetic interaction in . The magnetic characterization for is in agreement with the presence of Co(II) and Co(III) centers. Graphical Abstract  The title complexes and have been synthesized in excellent yields by reacting Co(OAc)₂·4H₂O with dianionic N₂O₂ coordinating ligands. In complex 1, each cobalt atom has distorted trigonal bipyramid geometry, while in complex 2, each cobalt atom has distorted octahedral geometry. Variable temperature magnetic moment measurements show weak antiferromagnetic interaction in complex 1. The magnetic characterization for complex 2 is in agreement with the presence of Co(II) and Co(III) centers. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Studies on mononuclear transition metal chelates derived from a novel ( E,E )-dioxime: synthesis,characterization and biological activity

A novel vic-dioxime ligand with a thiourea moiety, (4E,5E)-1,3-bis{4-[(4-bromophenylamino)methylene]phenyl}-2-thiooxaimidazoline-4,5-dione dioxime (4) (bmdH₂) has been synthesized from N,N′-bis{4-[(4-bromophenylamino)methylene]phenyl}thiourea and (E,E)-dichloroglyoxime. The bmdH₂ ligand (4) forms transition metal complexes [M(bmdH)₂] with a metal?:?ligand ratio of 1?:?2 with M?=?Ni(II), Co(II), and Cu(II). The mononuclear Ni(II), Co(II) and Cu(II) complexes, [Ni(bmdH)₂] (5), [Co(bmdH)₂] (6) and [Cu(bmdH)₂] (7) have the metal ions coordinated through the two N,N atoms, as do most vic-dioximes. Elemental analyses, molar conductivity, magnetic susceptibility, IR, ¹H NMR spectra, and UV-Visible spectroscopy were used to elucidate the structures of the ligand and its complexes. Conductivity measurements have shown that the mononuclear complexes are non-electrolytes. In addition, the ligands and metal complexes were screened for antibacterial and antifungal activities by agar well diffusion techniques using DMF as solvent.     

Synthesis and spectroscopic studies of metal(II) complexes prepared withN-2-(5-picolyl)-N′-phenylthiourea

Summary The chlorides and bromides of cobalt(II), nickel(II) and copper(II) along with the acetates of the latter two metal ions and copper(II) tetrafluoroborate were used to prepare complexes ofN-2-(5-picolyl)-N-phenylthiourea (5MTUH). 5MTUH coordinates as a bidentate ligand via the pyridyl nitrogen and the sulphur atoms in the cobalt(II) complexes and the compounds isolated with Cu(BF₄)₂ and CuCl₂. Complexes of stoichiometry [Cu(5MTU)X] (X=Br or C₂H₃O₂) appear to have the deprotonated ligand coordinated via the pyridyl andN thioamide nitrogens and the sulphur atom. The nickel(II) complexes involve monodentate 5MTUH with sulphur being the donor atom. A violet, octahedral [Co(5MTUH)₂Cl₂] complex and a blue, tetrahedral [Co(5MTUH)Cl₂] complex have been isolated, but with CoBr₂ only an octahedral complex could be prepared.     

Synthesis,structure, and electrochemistry of <Emphasis Type="Italic">trans</Emphasis>-[Co<Superscript>III</Superscript>{(BA)<Subscript>2</Subscript>pn}(L)<Subscript>2</Subscript>]ClO<Subscript>4</Subscript> complexes

The structure, spectroscopic, and electrochemical properties of [Co{(BA)₂pn}(L)₂]ClO₄ complexes, where (BA)₂pn = N,N′-bis(benzoylacetone)-1,3-propylenediimine dianion and the two ancillary ligands (L) are pyridine, py (1), and 4-methylpyridine, 4-Mepy (2), have been investigated. These complexes have been characterized by elemental analyses, IR, UV–Vis and ¹H-NMR spectroscopy. The crystal structure of [Co{(BA)₂pn}(py)₂]ClO₄ (1) has been determined by X-ray diffraction. The coordination geometry around cobalt(III) is best described as a distorted octahedron. The electrochemical reduction of these complexes at a glassy carbon electrode in acetonitrile solution indicates that the first reduction process corresponding to Co^III–Co^II is electrochemically irreversible, which is accompanied by the dissociation of the axial N(py)–cobalt bonds. This process becomes quasi-reversible upon the addition of excess py ligands. The second reduction step of Co^II/I shows reversible behavior and is not influenced by the nature of the axial ligands. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Studies on the Synthesis and Thermodynamic Stability of Two Multidentate Ligands 2,9-disubstituted 1,10-phenanthroline

Two multidentate ligands: N,N′-di-(propionic acid-2′-yl-)-2,9-di-aminomethylphenanthroline (L₁) and N,N′-di-(3′-methylbutyric acid-2′-yl-)-2,9-di-amino-methylphenanthroline (L₂) were synthesized and fully characterized by ¹H NMR and elemental analysis. The binding ability of L₁ and L₂ to metal ions such as M(II) (M = Cu, Zn, Co and Ni) and Ln(III) (Ln = La, Nd, Sm, Eu, and Gd) has been investigated by potentiometric titration in aqueous solution and 0.1 mol dm⁻³KNO₃ at 25.0 ± °C. In view of the structure of L₁ and L₂, mononuclear metal complexes can be formed in solution. The stability constants of binary complexes of ligands L1 and L2 with metal ions M(II) and Ln(III) have been determined respectively and further discussed.     

Mononuclear and heterobimetallic palladium(II) and platinum(II) complexes containing the mixed ligands <Emphasis Type="Italic">N</Emphasis>-(2-pyridyl or 2-pyrimidyl) acetamide and tertiary diphosphine

Palladium(II) and platinum(II) complexes containing mixed ligands N-(2-pyridyl)acetamide (AH) or N-(2-pyrimidyl)acetamide (BH) and the diphosphines Ph₂P(CH₂) _n PPh₂, (n = 1, 2 or 3) have been prepared. The prepared complexes [Pd(A)₂(diphos)] or [Pd(B)₂(diphos)] have been used effectively to prepare bimetallic complexes of the type [(diphos)Pd(μ-L)₂M′Cl₂] where M′ = Co, Cu, Mn, Ni, Pd, Pt or SnCl₂; L = A or B. The prepared complexes were characterized by elemental analysis magnetic susceptibility, i.r. and UV–Vis spectral data. ³¹P–{¹H}-n.m.r. data have been applied to characterize the produced linkage isomers.