Synthesis,characterisation and electrochemical study of 4,4′-bis(salicylideneimino) diphenylethane and its complexes with cobalt(II), copper(II) and cadmium(II)

We have prepared and characterised a new series of metal complexes obtained from 4,4-bis(salicylideneimino)diphenylethane (saldipH₂) and cobalt(II), copper(II) and cadmium(II) chlorides. In every case, the coordinating atoms are N and O. However, each compound has its own structure:[Co(saldip)]·2 H₂O is monomeric and a mononuclear species, [Cu₂(saldip)₂(H₂O)] is a binuclear complex and finally the cadmium complex is formulated as:[(CdCl₂)₂(saldipH₂)]·CdCl₂. An electrochemical study (cyclic voltammetry) indicates that the reduction, as well as the oxidation, of copper in [Cu₂(saldip)₂(H₂O)] proceeds in two steps. For the reduction of the two other complexes, two steps are indicated out: the first is attributed to the reduction of the metal and the second to the reduction of the coordinated ligands.     

β-diketone complexes of manganese(II), cobalt(II), nickel(II) and palladium(II)

Summary The reactions of manganese(II), cobalt(II) and nickel(II) acetates (1 mole) with antipyrine-4-azo--ethylcyanoacetate (HL¹) and antipyrine-4-azo--acetylacetone (HL²) (1 mole) produce complexes of the M(L)₂ type. K₂PdCl₄ (1 mole) reacts with HL¹ and HL² (1 mole) to yield complexes of the general formula PdLCl, the ligands behaving as monobasic tridentates. The electronic spectral and magnetic data show the complexes to be high-spin octahedral, whereas the palladium(II) complexes are diamagnetic square planar. The complexes were characterized by elemental analyses, conductance measurements and i.r. and electronic spectra as well as magnetic susceptibility measurements and thermal (t.g.a. and d.t.a.) analysis.Nuclear Material Authority.     

2,4′-Bipyridyl complexes with cobalt(II) and nickel(II)

Summary Complexes of empirical formulae [ML₂Cl₂(OH₂)₂], [CoL₂Br₂(OH₂)₂]L·4H₂O, [NiL₂Br₂(OH₂)₂]L₂·2H₂O, [ML₂(OH₂)₄]L₂(NO₃)₂ and [ML₄(OH₂)₂](ClO₄)₂·2H₂O (M = Co^II, Ni^II, L = 2,4-bipyridyl) were synthesized and characterized by elemental and spectral analyses. The thermal decomposition of the complexes was also investigated.Author to whom all correspondence should be directed.     

Complexation between decamethyl-3,3′-bis(dipyrrolylmethene) and zinc(II), copper(II), and cobalt(II) acetates

Decamethyl-3,3′-bis(dipyrrolylmethene) dihydrobromide H₂L · 2HBr (H₂L is bis(3,4,7,8,9-pentamethylpyrrol-3-yl)methane), which is the simplest representative of a novel class of oligo(dipyrrolylmethenes) belonging to chromophore chelating nonmacrocyclic ligands, were examined by ¹H NMR, IR, and electronic absorption spectroscopy. Complexation reactions of H₂L · 2HBr with M(AcO)₂ (M = Zn(II), Cu(II), and Co(II)) in DMF at 298.15 K were monitored by electronic absorption spectroscopy and studied by the molar ratio method. The thermodynamic constants K ⁰ of these reactions were estimated. The d metal ions coordinate H₂L to give the binuclear homoleptic complexes [M₂L₂]. The reactions proceed through the intermediate binuclear heteroleptic complex [M₂L(AcO)₂] detected by spectroscopic methods. The thermodynamic stabilities of [M₂L₂] and [M₂L(AcO)₂] increase when moving from Cu(II) to Zn(II) and Co(II). The probability of formation and stability of [M₂L₂] containing 3,3′-bis(dipyrrolylmethene) are substantially higher than those of analogous complexes with the 2,2′-isomer (decamethyl-2,2′-biladienea, c). The low K ⁰ values for the complexation between H₂L and Cu(AcO)₂ are due to slow oxidation of the biladiene ligand into a bilatriene with participation of Cu²⁺ ions.     

Cobalt(III), nickel(II) and copper(II) complexes of N,N′-didodecildithiooxamide

The complexes of N,N′-didodecildithiooxamide (L): CoL₃(ClO₄)₃, NiL₂X₂ (X = Cl, Br, I, ClO₄, HSO₄), CuL₂X₂ (X = ClO₄, HSO₄) and CuLX₂ (X = Cl, Br) were prepared. The cobalt and nickel complexes are diamagnetic, with octahedral and planar coordination respectively. The copper complexes are paramagnetic with normal magnetic moments corresponding to a tetragonal coordination. The i.r. and far i.r. spectra are discussed.     

Synthesis, structural characterisation and thermal decomposition studies of some 2,4′-bipyridyl complexes with cobalt(II), nickel(II) and copper(II)

2,4-Bipyridyl (2,4-bipy orL) complexes with cobalt(II), nickel(II) and copper(II) of the formulae M(2,4-bipy)₂(CH₃COO)₂·2H₂O (M(II) = Co, Ni, Cu), Co(2,4-bipy)₂SO₄·3H₂O or Ni(2,4-bipy)₂SO₄·4H₂O have been prepared and their IR and electronic (VIS) spectra are discussed. The thermal behaviour of the obtained compounds has also been studied. The intermediate products of decomposition at different temperatures have been characterized by chemical analysis and X-ray diffraction.We thank dr. A. Malinowska for performing VIS spectra. This work was supported by the KBN project No. PB 0636/P3/93/04.     

Mixed-ligand complexes of iron(II), iron(III), copper(II), and cobalt(II) with pyrazolonic and 2,2′-bipyridine ligands

New mixed-ligand complexes, [M₂(BAMP)(bipy)₂][MCl₄]₂, M=Co⁺²(1), Cu⁺²(2), [M₂(TAMEN)(bipy)₂][MCl₄]₂, M=Fe⁺²(3), Co²⁺(4), and [Fe₂(TAMEN)(bipy)₂][FeCl₆]₂ (5), where BAMP and TAMEN stand for the Mannich bases N,N′-bis(antipyryl-4-methylene)-piperazine and N,N′-tetra(antipyryl-4-methylene)-1,2-ethane-diamine, respectively, have been obtained and characterized by elemental analyses, conductometric and magnetic susceptibility measurements at room temperature, mass spectrometry, UV-Vis, infrared, and mass spectroscopy, and ¹H NMR spectra for the ligands.     

Copper(II), nickel(II), cobalt(II) and oxovanadium(IV) complexes of substituted β-hydroxyiminoanilides

Complexes of the general formula, ML₂ [M = Cu^II, Ni^II, Co^II and OV^IV; L = 1,2,3,5,6,7,8,8a-octahydro-3-hydroxyimino-N-(4-X-phenyl)-l-phenyl-5-(phenylmethylene)-2-naphthalenecarboxamide (X = H, Me, OMe, Cl)] have been prepared and characterized on the basis of elemental analysis, magnetic moments and i.r., e.p.r. and electronic spectra. These metal complexes contain the N₄ chromophore with the ligand coordinating through nitrogens of the azomethine and deprotonated anilide functions. C.v. measurements indicate that the copper(II) complexes are quasi-reversible in acetonitrile solution. Square planar and square pyramidal structures are assigned respectively to the copper(II) and oxovanadium(IV) complexes, whereas tetrahedral geometry is assigned to the nickel(II) and cobalt(II) complexes. Deprotonated anilide nitrogen is involved in coordination and the presence of an electron-donating group para to the anilide function decreases the ΔE values of the d–d transitions while the value is found to increase when electron-withdrawing groups are substituted. Line spacing in the e.p.r. spectra of the copper(II) and oxovanadium(IV) complexes increases when methyl group is para to the anilide group, and decreases when this group is replaced by methoxy or chloro. The ν(C–N) of the anilide group and the ν(C-N) of the azomethine function of the oxime metal complexes are metal-sensitive and the blue shift for the above stretching frequencies follows the order: copper(II) > oxovanadium(IV) > nickel(II) ≈ cobalt(II). This revised version was published online in June 2006 with corrections to the Cover Date.     

Complexes of N-aroyl-N′-thiobenzohydrazide with cobalt(II), nickel(II) and zinc(II)

Summary New potential tetradentate ligands, N-benzoyl-N-thiobenzohydrazide (H₂BTBH) and N-salicyl-N-thiobenzohydrazide (H₂SBTH) have been prepared and characterized. Their complexes with Co^II, Ni^II and Zn^II have been prepared and characterized on the basis of elemental analyses, magnetic susceptibility measurements, and u.v.-vis., i.r. and ¹H-n.m.r. spectral studies. The bonding and stereochemistries of the complexes are discussed. H₂BTBH, H₂SBTH and the complexes have been screened towards a number of bacteria.     

Synthesis and crystal structure of complexes of manganese(II), cobalt(II), and nickel(II) isothiocyanates with ?-caprolactam

The possibility of ?-caprolactam (CPL) to coordinate to manganese(II), cobalt(II), and nickel(II) rhodanides has been investigated. New complexes trans-[M(CPL)₄(NCS)₂], where M = Mn (I), Co (II), and Ni (III), have been synthesized. The complexes have been studied by chemical analysis and IR spectroscopy. According to X-ray diffraction, complexes are isostructural to each other and crystallize in monoclinic space group P2₁/c, Z = 2. For I: a = 6.9457(2) ?, b = 17.7751(6) 0A, c = 12.8999(4) 0A, ?? = 104.2670(10)°, V = 1543.51(8) ?³, ??_calc = 1.342 g/cm³, R ₁ = 0.0426. For II: a = 6.8925(2) ?, b = 17.8189(8) ?, c = 12.7278(6) ?, ?? = 104.421(2)°, V = 1513.93(11) ?³, ??_calc = 1.377 g/cm³, R ₁ = 0.0280. For III: a = 6.7804(2) ?, b = 18.4631(4) ?, c = 12.4841(3) ?, ?? = 105.2950(10)°, V = 1507.49(7) ?³, ??_calc = 1.382 g/cm³, R ₁ = 0.0273. Structures I?CIII are molecular; the metal atom in each of them coordinates four CPL molecules and two NCS groups via oxygen and nitrogen atoms, respectively.     

Hydrogen-bonded networks based on manganese(II), nickel(II), copper(II) and zinc(II) complexes of N,N′-dimethylurea

A project related to the crystal engineering of hydrogen-bonded coordination complexes has been initiatied and some of our first results are presented here. The compounds [Mn(DMU)₆](ClO₄)₂ (1), [Ni(DMU)₆](ClO₄)₂ (2), [Cu(OClO₃)₂(DMU)₄] (3) and [Zn(DMU)₆](ClO₄)₂ (4) have all been prepared from the reaction of N,N-dimethylurea (DMU) and the appropriate hydrated metal perchlorate salt. Crystal structure determinations of the four compounds demonstrate the existence of [M(DMU)₆]²⁺ cations and ClO₄ ^– counterions in (1), (2) and (4), whereas in (3) monodentate coordination of the perchlorate groups leads to molecules. The [M(DMU)₆]²⁺ cations and ClO₄ ^– anions self-assemble to form a hydrogen-bonded one-dimensional (1D) architecture in (1) and different 2D hydrogen-bonded networks in (2) and (4). The hydrogen bonding functionalities on the molecules of (3) create a 2D structure. The complexes were also characterised by room-temperature effective magnetic moments and i.r. studies. The data are discussed in terms of the nature of bonding and the known structures.     

Potentiometric determination of the formation constants for complexes of 3,2′,2″-triaminopropyldiethylamine with cobalt(II), nickel(II), copper(II), zinc(II) and cadmium(II)

The tripodal tetraamine ligand N{(CH₂)₃NH₂}{(CH₂)₂NH₂}₂ (pee), has been investigated as an asymmetrical tetraamine chelating agent for Co^II, Ni^II, Cu^II, Zn^II and Cd^II. The protonation constants for this ligand and the formation constants for its complexes have been determined potentiometrically in 0.1 M KCl at 25 °C. The successive protonation constants (log K _n ) are: 10.22, 9.51, 8.78 and 1.60 (n = 1–4). One complex with formula M(pee)²⁺ (M = Co, Ni, Cu, Zn and Cd) is common to all five metal ions and the formation constant (log _ML) is: 12.15, 14.17, 16.55, 13.35 or 9.74, respectively. In addition to the simple complexes, Co^II, Cu^II and Zn^II also give hydroxo complexes, and Cu^II and Ni^II give complexes with monoprotonated pee. [Zn(pee)](ClO₄)₂ and [Cd(pee)Cl](ClO₄) complexes were isolated and are believed to have tetrahedral and trigonal-bipyramidal structures, respectively.     

Complexes of N-nicotinoyl-N′-2-furanthiocarbohydrazide with oxovanadium(IV), manganese(II), iron(II & III), cobalt(II), nickel(II), copper(II) and zinc(II)

A new potential tetradentate ligand, N-nicotinoyl-N-2-furanthiocarbohydrazide (H₂Nfth), and its complexes with VO^IV, Mn^II, Fe^II,III, Co^II, Ni^II, Cu^II and Zn^II have been prepared and characterized by elemental analyses, magnetic susceptibility measurements, u.v.–vis, i.r., n.m.r., ES⁺ and FAB mass spectral data. The room temperature e.s.r spectra of the VO^IV and Fe^III complexes yield g values, characteristic of octahedral complexes. The Mössbauer spectra of [Fe(HNfth)₂] and [Fe₂(Nfth)₃] at room temperature and at 78 K suggest the presence of high-spin iron(II) and iron(III), respectively. The complexes are electrically insulating at room temperature, however, their conductivities increase as the temperature increases from 333–383 K, with a band gap of 0.46–0.77 eV, indicating their semiconducting behaviour. H₂Nfth and its soluble complexes have been screened against several bacteria and fungi.     

Complexes of N-phenyl-N′-2-furanthiocarbohydrazide with oxovanadium(IV), manganese(III), iron(III), cobalt(II), nickel(II), copper(II) and zinc(II)

A new ligand, N-phenyl-N -2-furanthiocarbohydrazide (HPhfth), and its complexes with VO^IV, Mn^III, Fe^III, Co^II, Ni^II, Cu^II and Zn^II have been prepared and characterized by elemental analyses, magnetic susceptibility measurements, i.r., n.m.r., u.v.–vis., mass and FAB mass spectral data. The room temperature e.s.r. spectra of the VO^IV, Fe^III and Cu^II complexes yield <g> values characteristic of square pyramidal VO^IV, octahedral Fe^III and square planar Cu^II, respectively. The Ni^II and Cu^II complexes semiconduct, but the Zn^II complex is an insulator at room temperature. However, the conductivity increases as the temperature increases from 303–383 K, with a band gap of 0.21–1.01 eV. HPhfth and its soluble complexes have been screened against several bacteria and fungi.     

Synthesis and spectral studies of copper(II), nickel(II) and cobalt(II) complexes of 2-hydroxy-ω-4-X-cinnamoyl acetophenones and their pyridine adducts

Summary Complexes of the type M(HXCA)₂·nH₂O (M = Cu^II, Ni^II or Co^II; HXCA = 2-hydroxy--4-X-cinnamoyl acetophenone; X = H, Cl, Me or OMe; n = 0 or 2) have been synthesized, and characterized by elemental analysis, i.r., electronic, ¹H-n.m.r. and e.s.r. spectroscopies, and magnetic susceptibility measurements. The spectral data indicate that the ligand coordinates through both carbonyl and enolic oxygens. The anhydrous Cu^II complexes are monomeric and square planar, while the Ni^II and Co^II analogues possess polymeric high-spin octahedral structures. The diaquates and dipyridinates of Co^II and Ni^II have monomeric high-spin octahedral geometries.     

4,4′-Bipyridine complexes of molybdenum(II) and tungsten(II)

Treatment of [MI₂(CO)₃(NCMe)₂] with two equivalents of 4,4-bipyridine (4,4-bipy) in CH₂Cl₂ at room temperature gave the MeCN displaced products, [MI₂(CO)₃(4,4-bipy-N)₂] (1) and (2). Equimolar amounts of [MI₂(CO)₃(NCMe)₂] and L (L = PPh₃, AsPh₃ or SbPh₃) react to give [MI₂(CO)₃(NCMe)L], which when reacted in situ with 4,4-bipy yield the new complexes, [MI₂(CO)₃(4,4-bipy-N)L] (3)–(8). Reaction of equimolar quantities of [WI₂(CO)(NCMe)( ²-RC₂R)₂] (R = Me or Ph) and 4,4-bipy gave the new bis(alkyne) complexes, [WI₂(CO)(4,4-bipy-N)( ²-RC₂R)₂] (9) and (10). Treatment of [MI₂(CO)₃(NCMe)₂] with two equivalents of (9) or (10) in CH₂Cl₂ at room temperature affords the bimetallic complexes, [MI₂(CO)₃{WI₂(CO)(4,4-bipy-N,N)( ²-RC₂R)₂}₂] (11)–(14). Equimolar quantities of [MI₂(CO)₃(NCMe)(PPh₃)] (prepared in situ) and (9) or (10), react to give the 4,4-bipy-bridged complexes, [MI₂(CO)₃{WI₂(CO)(4,4-bipy-N,N)( ²-RC₂R)₂}(PPh₃)] (15)–(18). All the new complexes, (1)–(18) were characterised by elemental analysis (C, H and N), i.r. and ¹H-n.m.r. spectroscopy.     

Synthesis and crystal structures of cobalt(III), copper(II), nickel(II) and zinc(II) complexes derived from 4-methoxy-N′-(pyridin-2-ylmethylene)benzohydrazide with urease inhibitory activity

Abstract

Urease catalyzes the decomposition of urea into ammonia, which has harmful effects on both human health and fertile soil. Aiming at exploring novel urease inhibitors, a series of hydrazone compounds and their Co^III, Cu^II, Ni^II, and Zn^II complexes were prepared from 4-methoxy-N'-(pyridin-2-ylmethylene)benzohydrazide (HL). They are [CoClL(NCS)] (1), [CoL₂]·Cl·CH₃OH·H₂O (2), [CuL(NCNCN)]_n·nCH₃OH (3), [NiL(HL)]·ClO₄·CH₃OH (4) and [ZnClL(OH₂)]·CH₃OH (5). The compounds were characterized by physico-chemical methods. Structures of the complexes were further confirmed by single crystal X-ray diffraction. The metal ions in 1, 3, and 5 display square pyramidal coordination and 2 and 4 display octahedral coordination. The inhibitory effects of the compounds on Jack bean urease were evaluated. The results showed that 3 has effective urease inhibitory activity, with IC₅₀ value of (7.3?±?1.0) μmol L^?1.     

Manganese(II), nickel(II) and copper(II) complexes of (1,3-bis-aminomethyl) cyclohexane-N,N,N′,N′-tetrakisbenzimidazole

Summary Mn^II, Ni^II and Cu^II complexes of (1,3-bis-aminomethyl)-cyclohexane-N,N,N,N-tetrakisbenzimidazole (CDTB) have been prepared and characterized by spectral techniques. The complexes are monomeric and pseudo-octa-hedral, as evidenced by their e.p.r. spectra and analytical data. Parameters ², ², ² and for Cu^II complexes, and the crystal field splitting parameter (10 Dq) together with the Nephelauxetic ratio (), for Ni^II complexes, are reported.     

Synthesis of N,N′-bis(isopropylaminoethyl)-1,10-phenanthroli ne- 2,9-dimethanamine and N,N′-bis(diethylaminoethyl)-1,10-phenanthroline -2,9-dimethanamine and potentiometric determination of the formation constants of their complexes with manganese(II), cobalt(II), copper(II) and zinc(II)

Two hexadentate compounds incorporating 1,10-phenanthroline and four alkylamino donors have been prepared. The protonation constants and the formation constants of dipositive ion (Mn2+, Co2+, Cu2+ and Zn2+) complexes have been determined in aqueous solution by pH titration at 25 ± 0.1 °C and I = 0.1 mol·dm–3 NaNO3.     

Synthesis and characterization of binuclear μ-oxalato nickel(II), copper(II) and zinc(II) complexes with 3,3′-diamino-N-methyl-dipropylamine or trans-1,2-diaminocyclohexane

New binuclear complexes of the type [(Ni(Medpt)NO₃)₂ox] (1) (Medpt=3,3′-diamino-N-methyl-dipropylamine, H₂ox=oxalic acid), [(Ni(dach)₂)₂ox]NO₃·2H₂O (2) (dach=trans-1,2-diaminocyclohexane), [(Cu(Medpt))₂ox]X₂·yH₂O (X=NO₃, y=2 2/3 (3); X=ClO₄, y=0 (4)) and [(Zn(dach)₂)₂ox](ClO₄)₂·2H₂O (5) have been prepared and characterized by IR and UV–Vis spectroscopies. Spectroscopic data are consistent with oxalate-bridged structures between six-coordinated (N₃O₃ or N₄O₂) Ni(II) (compounds 1 or 2), five-coordinated (N₃O₂) Cu(II) (compounds 3 and 4) or six-coordinated (N₄O₂) Zn(II) (compound 5). The crystal structure of [(Cu(Medpt))₂ox](NO₃)₂·2 2/3 H₂O (3) has been determined by single-crystal X-ray analysis. The structure of (3) consists of centrosymmetric binuclear cations [(Medpt)Cu(ox)Cu(Medpt)]²⁺, nitrate anions and water molecules of crystallization. The copper atom is five-coordinated by two oxalate–oxygen and three Medpt–nitrogen atoms, in a hybrid arrangement between trigonal–bipyramidal and square–pyramidal. The temperature dependence of magnetic susceptibility (1.8–300 K) was measured for compounds 1–4. Magnetochemical measurements show that Ni(II) complexes are antiferromagnetically coupled, J=−29.4 (1) and −32.7 cm⁻¹ (2) (H=−JS₁S₂) while the Cu(II) complexes present a very weak coupling, J=−2.6 (3) and +1.9 cm⁻¹ (4), being antiferro- and ferromagnetic in nature.