Syntheses and characterization of cobalt(II) and iron(III) complexes with the Schiff basesN-(o-hydroxybenzylidene)-2-aminobenzimidazole andN-(o-hydroxybenzylidene)-2(2′-aminophenyl)benzimidazole

Summary N-(o-hydroxybenzylidene)-2-aminobenzimidazole (HL) andN-(o-hydroxybenzylidene)-2(2-aminophenyl)benzimidazole (HL) react with CoX₂ (X=Cl, Br, or NCS) and FeCl₃ yielding complexes of general formulae [Co(HL)₂X₂], [Co(HL)₂X₂], [FeCl₂(HL)₂] [FeCl₄], and [FeCl₂(HL)₂][FeCl₄]. Moreover, it was possible to isolate the complexes [Co(HL)Br₂] [Co(L)Cl] and [Co(L)Cl]. The complexes were characterized by elemental analyses, i.r. and electronic spectroscopies and conductivity and magnetic measurements at different temperatures.     

Titanium(III) and vanadium(III) chloride complexes with 2-pyridylphenylacetonitrile and 1,2-dicyano-1,2-diphenyl-1,2-di(2′-pyridyl)ethane

Summary 2-Pyridylphenylacetonitrile (ppa) and 1,2-dicyano-1,2-diphenyl-1,2-di(2-pyridyl)ethane (dcppe) react with titanium(III) and vanadium(III) chlorides yielding complexes of formulae: [TiCl₃(ppa)₂], [TiCl₃(ppa)₃], [VCl₃(ppa)], [TiCl₃(dcppe)] and [(VCl₃)₂(dcppe)]. The results obtained suggest pentacoordinated structures for complexes, except for [TiCl₃(ppa)₃] where an hexacoordinated stereochemistry around the metal is proposed.     

4-amino-2,6-dimethyl-5-oxo-3-thioxo-2,3,4,5-tetrahydro-l,2,4-triazine cobalt(II) complexes

Summary Cobalt(II) complexes of 4-amino-2,6-dimethyl-5-oxo-3-thioxo-2,3,4,5-tetrahydro-1,2,4-triazine (taz) were prepared by reacting the triazine with the corresponding cobalt salt. The isolated compounds were of the types: [CoCl₂(taz)], [CoX₂(taz)₂(H₂O)₂] (X = Br or I), [CoX₂(taz)₂] (X = Br, SCN or NO₃) and [Co(taz)₂(H₂O)₂]X₂(X = C1O₄, BF₄ or NO₃). Conductance, magnetic and spectroscopic (i.r. and vis.) data were used for structural assignments. Pseudooctahedral and pseudotetrahedral structures are proposed for the complexes, with the triazine molecule acting either as a monodentate nitrogen-donor or a bidentate nitrogen-sulphur-donor ligand.     

Synthesis,characterization, crystal structures, in vitro and in vivo antitumor activity of palladium(II) and zinc(II) complexes with 2-formyl and 2-acetyl pyridine N(4)-1-(2-pyridyl)-piperazinyl thiosemicarbazone

The present paper includes synthesis and spectral characterization of the novel prepared palladium(II) and zinc(II) complexes with 2-formyl pyridine N(4)-1-(2-pyridyl)-piperazinyl thiosemicarbazone, HFo4Npypipe, 1 and the 2-acetyl pyridine N(4)-1-(2-pyridyl)-piperazinyl thiosemicarbazone, HAc4Npypipe, 2. The Pd(II) complexes [PdCl(Fo4Npypipe)], 3, [PdCl(Ac4Npypipe)], 4 and the Zn(II) complexes [ZnCl₂(Fo4Npypipe)], 5 and [ZnCl₂(Ac4Npypipe)], 6 have been characterized by elemental analyses and spectroscopic studies. The crystal structure of the complexes [PdCl(Fo4Npippy)], 3 and [PdCl(Ac4Npippy)], 4, have been solved by single-crystal X-ray diffraction. The electronic, IR, UV/Vis, and NMR spectroscopic data of the complexes are reported. The results of the cytotoxic activity of 1–6 have been evaluated in vitro against the cells of three human cancer cell lines: MCF-7, T24, A-549 and a mouse L-929 (a fibroblast-like cell line cloned from strain L). For selected compounds 2 and 6 the acute toxicity and antitumor activity were evaluated on leukemia P388-bearing mice. The Zn(II) compounds 5 and 6 are considered as agents with potential antitumor activity, and can therefore be candidates for further stages of screening in vitro and/or in vivo.     

[Fe(C12H8N3O2)Cl2(ROH)], with R = Me and Et

The title octahedral complexes, [bis(pyridine‐2‐carbonyl)­amin­ate]­di­chloro­(methanol)­iron(III), [Fe(C₁₂H₈N₃O₂)­Cl₂‐(CH₄O)], and [bis­(pyri­dine‐2‐carbonyl)­amin­ate]­di­chloro‐(ethanol)­iron(III), [Fe­(C₁₂H₈N₃O₂)Cl₂(C₂H₆O)], both crystallize in space group and have similar structures. Mono­anionic bpca^? [bis(pyridine‐2‐carbonyl)­amin­ate] acts as a planar tridentate ligand in both cases. Coordination bond distances are in the range typical of high‐spin Fe^III complexes. Carbon–oxygen distances are typical of a C=O double bond suggesting the negative charge of the bpca^? ligand is localized on the central N atom.     

Selective removal of Cd(II), As(III), Pb(II) and Cr(III) ions from water resources using novel 2-anthracene ammonium-based magnetic ionic liquids

Facile synthesis of two 2-anthracene ammonium-based magnetic ionic liquids (MILs), 2-anthracene ammonium tetrachloroferrate (III) ([2A-A]FeCl₄) and 2-anthracene ammonium trichlorocobaltate (II) ([2A-A]CoCl₃) was performed by protonation of 2-aminoanthracene, followed complexation with FeCl₃/CoCl₂. The MILs were tested in the adsorptive removal of Cd²⁺, As³⁺, Pb²⁺ and Cr³⁺ from water sources. Upon treatment with 10 mg dosage of MILs in 10 mL aqueous solution of 50 ppm each of Cd²⁺, As³⁺, Pb²⁺ and Cr³⁺, adsorption capacity (mg/g) in the range of 5.73–55.5 and 23.6–56.8 for [2A-A]FeCl₄ and [2A-A]CoCl₃ respectively were recorded. Thus, the optimization, kinetic and isotherms studies were conducted using the [2A-A]CoCl₃ adsorbent. The [2A-A]CoCl₃ was more effective in pH 7–9, and equilibrium adsorption was achieved after 60 min contact time. The adsorption process proceeded via the Pseudo-second order pathway and the Langmuir isotherm model is the best fit for the adsorption process (with q_max = 227 – 357 mg/g) of all the targeted metal ions. The [2A-A]CoCl₃ adsorbent demonstrated practicality with large distribution and selectivity coefficients of the targeted ions, and up to six times regeneration.     

Complexes of NS and NSO donor ligands. Nickel(II), copper(II) and cobalt(II) complexes of glyoxal bis(morpholineN-thiohydrazone) and diacetyl bis(morpholineN-thiohydrazone)

Summary Reactions of glyoxal bis(morpholineN-thiohydrazone), H₂gbmth, with NiCl₂·6H₂O, Ni(OAc)₂·4H₂O, Ni(acac)₂· H₂O, CuCl₂·2H₂O, Cu(OAc)₂·H₂O, Cu(acac)₂, CoCl₂· 6H₂O, Co(OAc)₂·4H₂O and Co(acac)₂·2H₂O yield complexes of the type [M(gbmth)], [M=Ni^II, Cu^II or Co^II]. Diacetyl reacts with morpholineN-thiohydrazide in the presence of nickel salts to yield [Ni^II(dbmth)], [Ni^II(dmth)(OAc)]H₂O and [Ni^II(Hdmth)(NH₃)Cl₂] involving N₂S₂ and NSO donor ligands. Copper and cobalt complexes of N₂S₂ and NSO donor ligands with compositions [Cu^II(dbmth)], [Co^II(dbmth)]·4H₂O and [Co^II(H₂dbmth)]Cl₂, have been isolated. The compounds have been characterised by elemental analyses, magnetic moments, molar conductance values and spectroscopic (electronic and infrared) data.     

Co(II), Mn(II) and Cu(II) complexes of fluoroquinolones: Synthesis, spectroscopical studies and biological evaluation against Trypanosoma cruzi

[MnCl₂(NOR)(H₂O)₂] (1), [MnCl₂(SPAR)(H₂O)₂] (2), [CoCl₂(NOR)(H₂O)₂] (3) [CoCl₂(SPAR)(H₂O)₂] (4), [CuCl₂(phen)(NOR)] (5) and [CuCl₂(phen)(SPAR)] (6) complexes with norfloxacin (NOR) and sparfloxacin (SPAR) were obtained from MnCl₂·4H₂O, CoCl₂·4H₂O and CuCl₂(phen). In all cases the NOR and SPAR coordinate in the neutral zwitterionic form. The electron paramagnetic resonance spectra of the Cu(II) complexes (5) and (6) in aqueous and DMSO solutions indicate mixture of mononuclear and binuclear complex. Complexes (1-6), together with the corresponding ligands were evaluated for their in vitro trypanocidal effect, against both bloodstream trypomastigotes and intracellular forms of Trypanosoma cruzi. SPAR and NOR were poorly effective upon T. cruzi, complexes (3) and (4) were active against intracellular forms of the parasite. The complexes (5) and (6) displayed a higher activity upon both bloodstream and intracellular forms. The potency of fluoroquinolones, specially those coordinated to Cu(II)-phen justify further trypanocidal screening assays with this compounds in vitro as well as upon experimental models of T. cruzi infection.     

Organic amines reduce trans-dichlorotetrakis(pyridine)cobalt(III) chloride to cobalt(II)

Summary The reaction of dichlorotetrakis(pyridine)cobalt(III) chloride. [CoCl₂(Py)₄]Cl, with alkyl- or arylamines in EtOH or i-PrOH yielded [CoCl₂(Py)₂] in all cases. This reduction of Co^III to Co^II takes place only in the presence of the amines. [CoCl₂(Py)₂] in EtOH is oxidized by Cl₂ gas and in the presence of pyridine gives [CoCl₂(Py)₄] ⁺, while in pyridine alone [CoCl₂(Py)₄] is formed.     

Cu(II) and Zn(II) complexes with a fluoroquinolone antibiotic: Spectroscopic and X-ray absorption characterization

The synthesis of two complexes with the antibiotic flumequine, [Cu(Flumequine)₂(OH₂)₂] (1) and [Zn(Flumequine)₂(OH₂)₂]·H₂O (2) is reported. Their molecular structure was elucidated by combining various spectroscopic techniques. The EPR parameters combined with XAS data underline a tetragonal distorted octahedral geometry for the two complexes. The coordination occurs through the carbonyl and carboxylate oxygen atoms in the equatorial plane. The coordination sphere is completed by two water molecules in axial position.     

Reactions of palldium(II) compounds with carbon monoxide in alcohol/amine systems : a new route to palladium(O) carbonyl and carboalkoxy-palladium(II) complexes

Palladium(O) carbonyl complexes, Pd(CO)(PPh₃)₃ Pd₃(CO)₃(PPh₃)₃ and Pd₃(CO)₃(PPh₃)₄, can conveniently be prepared by the reaction of (PPh₃)₂PdCl₂ with carbon monoxide at room temperature in methanol/amine systems involving primary and secondary amines such as diethylamine and cyclohexylamine. These carbonyl complexes are interconvertible under suitable conditions. On the other hand, use of tertiary amine such as triethylamine and tri-n-butylamine in place of the above amines give selectively a carbomethoxy complex (PPh₃)₂PdCl(COOCH₃).     

The solid state and solution chemistry of dichlorobis(α-picoline)-cobalt(II)

Summary The thermal decomposition of [CoCl₂(-pic)₂] was investigated over the 108°C to 222°C range and the Intennediates CoCl₂(-pic) (s) and CoCl₂ (s) were observed, with the evolution of (-pic) (g). Quantitative thermodynamic and kinetic data were obtained by performing dynamic and isothermal studies on the complex Additional thermodynamic data were obtained by studying the CoCl₂/-pic system in acetone. The effect of the methylsubstituent on the metal-donor-N bond as well as on the thermodynamic quantities were discussed.     

Reactions of 2-pyridylphenylacetonitrile and 1,2-dicyano-1,2-di(phenyl)-1,2-di(2-pyridyl)ethane with titanium(IV), vanadium(IV), chromium(III) and iron(III) chlorides

Summary 2-Pyridylphenylacetonitrile (ppa) is oxidized by iron(III) chloride in dry ethanol to 1,2-dicyano-1,2-di(phenyl)-1,2-(2-pyridyl)ethane (dcppe). When 1,2-dichloroethane or ether are used as solvents, a 31 complex of dcppe with iron trichloride, [(FeCl₃)₃(dcppe)] is obtained.Titanium(IV), vanadium(IV) and chromium(III) chlorides react with ppa and dcppe, giving complexes of general formulae [MCl₄(ppa)] (M = Ti or V), [CrCl₃(ppa)_n] (n = 2 or 3), [(MCl₄)₂(dcppe)] (M = Ti or V) and [CrCl₃(dcppe)].     

Nickel(II) and zinc(II) complexes with N-(5,6-dihydro-4H-1,3-thiazin-2-yl)-2-aminobenzimidazole (BzTz): Synthesis,spectral and structural characterization

The reaction of nickel and zinc chlorides and nitrates with the ligand N-(5,6-dihydro-4H-1,3-thiazin-2-yl)-2-aminobenzimidazole (BzTz) leads to the formation of the new complexes: [NiCl₂(BzTz)₂] (1), [Ni(NO₃)(BzTz)₂(H₂O)₃](NO₃) (2), [ZnCl₂(BzTz)₂] (3) and [Zn(NO₃)₂(BzTz)₂] (4). They have been characterized by spectroscopic methods (electronic, infrared and NMR) and magnetic susceptibility measurements. Additionally, the crystal structures of the complexes 1 and 3 have been determined by X-ray single-crystal diffraction. The ligand exhibits the N-benzimidazole coordination mode on interacting with the metal centers. The X-ray structure of the complexes 1 and 3 reveals a distorted tetrahedral coordination geometry around the metal center, with the metallic atoms coordinated to two chlorine atoms and two benzimidazole nitrogen atoms. These two complexes are isostructural, crystallizing in the monoclinic system and Cc space group. In complex 2 the geometry around the nickel atom could be described as a distorted octahedron whereas in case of complex 4 the zinc atom is in a distorted tetrahedral environment.     

Synthesis,physico-chemical and biological studies on oxovanadium(IV) derivatives of mercaptotriazoles

Summary Complexes of 3-methyl- or 3-ethyl-4-amino-5-thiolato-1,2,4-triazole (LH) and its Schiff base derivatives with oxovanadium(IV), of the types [VOL₂(H₂O)], [VOL₂-(H₂O)] and [VOL(H₂O)₂] (where LH = Schiff bases derived from condensation of LH with benzaldehyde, 2-chlorobenzaldehyde, 4-methoxybenzaldehyde or acetophenone; LH₂ = Schiff bases derived from condensation of LH with salicylaldehyde or o-hydroxyacetophenone) have been prepared and characterized by elemental analyses, electrical conductance, magnetic moments and spectral data. The thermal behaviour of selected complexes was investigated by t.g., d.t.g. and d.s.c. techniques. The antifungal and antiviral activities of the Schiff bases and their corresponding complexes were also investigated.Author to whom all correspondence should be directed.     

Cobalt(II) and nickel(II) cloride complexes with 4,5-(<Emphasis Type="Italic">n</Emphasis>-pyridylethylene)-dithio-1,3-dithiol-2-thiones (<Emphasis Type="Italic">n</Emphasis> = 2, 4)

The NiCl₂ and CoCl₂ complexes with 4,5-(2-pyridylethylene)-dithio-1,3-dithiol-2-thione (L¹) and 4,5-(4-pyridylethylene)-dithio-1,3-dithiol-2-thione (L²) were described. The L¹ ligand shows bidentate coordination through the pyridyl N atoms and the thiol S atoms in a tetrahedral [CoCl₂(L¹)] complex (I) and in an octahedral [NiCl₂(L¹)₂](MeCN)₂ complex (II). The L² ligand exhibits monodentate coordination through the pyridyl N atom in tetrahedral complexes [CoCl₂(L²)₂ (III) and [NiCl₂(L²)₂] (IV). Complexes I, III, IV in crystal state are octahedral due to extra coordination of the thione S atoms or the chloride bridges responsible for the polymeric structure. The structure of the complex II · CH₂Cl₂ was determined by X-ray diffraction analysis. The crystals are monoclinic, space group P2₁/c, a = 11.895(2) Å, b = 13.374(3) Å, c = 21.873(4) Å, β = 95.30(3)°, Z = 2. The Ni atom has quasi-tetrahedral surrounding due to two chloride ions and two L¹ ligands coordinated through the pyridyl N atoms and the thiol S atoms.     

Heterobimetallic dioxomolybdenum(VI) complexes derived from bis(2-hydroxy-1-naphthaldehyde)malonoyldihydrazone: Synthesis and characterization

The heterobimetallic complexes [MMoO₂(L)(H₂O)₂] (where M = Zn²⁺ (1), Cu²⁺ (2), and Co²⁺ (4)) and [{MMoO₃(H₂L)(H₂O)₂}₂] (where M = Ni²⁺ (3) and Mn²⁺ (5)) are synthesized from bis(2-hydroxy-1-naphthaldehyde)malonoyldihydrazone (H₄L) using the monometallic precursor complex [MoO₂(H₂L)]·H₂O in ethanol. The composition of the complexes is established based on the data obtained from the elemental analysis and molecular weight determinations. The structure of the complexes is discussed in the light of data obtained from molar conductance, magnetic moment, electronic, EPR and IR spectroscopic studies.     

A cyclic voltammetric study of iron(II)/ruthenium(II) complexes with bis(tertiary phosphines)

Summary Nine complexes of Fe^IIRu^II with bis(tertiary phosphines), namely, 1,2-bis(diphenylphosphino)ethane (dppe), 1,2-bis (diphenylphosphino)ethylene (dppen) and o-phenylenebis (diphenylphosphine) (o-diphos) were studied using cyclic voltammetry. The half-wave potentials for the complexes studied are: (1) [FeCl₂(dppe)], 0.050V; (2) [Fe(NCS)₂(dppe)₂], 0.265V; (3) [RuCl₂(dppe)₂], 0.548V; (4) [FeCl₂(dppen)₂], 0.225V; (5) [Fe(NCS)₂-(dppen)₂], 0.290V; (6) [RuCl₂(dppen)₂], 0.690V; (7) [FeCl₂(o-diphos)₂] 0.160V; (8) [Fe(NCS)₂(o-diphos)₂] 0.582V; and (9) [RuCl₂(o-diphos)₂], 0.265V. The redox potentials are related to the nature of the ligand, the nature of the metal, the stereochemistry of the complex and the ligand field strength.     

Synthesis, photochemistry, and electrochemistry of ruthenium(II) polypyridyl complexes anchored by dicobalt carbonyl units

A novel hybrid complex system of ruthenium polypyridyl complexes anchored by dicobalt carbonyl units, [Ru(bpy)₂{phen-C{Co₂(CO)₄(dppm)}C-tolyl}](PF₆)₂ (1) and [Ru(bpy)₂{tolyl-C{Co₂(CO)₄(dppm)}C-phen-C{Co₂(CO)₄(dppm)}C-tolyl}](PF₆)₂ (2), has been prepared from the dicobalt carbonyl complex Co₂(CO)₆(dppm) (dppm = bis(diphenylphosphino)methane) and the ruthenium complex [Ru(bpy)₂(phen--tolyl)](PF₆)₂ (3) or [Ru(bpy)₂(tolyl--phen--tolyl)](PF₆)₂ (4).The present Ru-Co₂ hybrid complexes 1 and 2 are nonluminescent at room temperature, although precursor ruthenium polypyridyl complexes, such as 3 and 4, clearly show phosphorescence from the ³MLCT excited state. The emission quenching of these hybrid complexes indicates the intramolecular energy transfer from the ruthenium polypyridyl unit to the dicobalt carbonyl unit(s) and then to the ground state by a radiationless deactivation process accompanied by a vibrational relaxation of the dicobalt carbonyl unit(s). This interpretation is supported by spectral change measurements along with constant potential electrolysis and electrochemical data.     

Synthesis,crystal structures and catalytic epoxidation properties of dioxomolybdenum(VI) complexes with hydrazone ligands

A series of dioxomolybdenum(VI) complexes with similar hydrazone ligands have been prepared, specifically [MoO₂L¹(MeOH)] (1), [MoO₂L²(MeOH)] (2) and [MoO₂L³(MeOH)] (3), where L¹, L² and L³ are the dianionic forms of 2-chloro-N′-(2-hydroxybenzylidene)benzohydrazide, 2-chloro-N′-(2-hydroxy-5-methylbenzylidene)benzohydrazide and N′-(3-bromo-5-chloro-2-hydroxybenzylidene)-2-chlorobenzohydrazide, respectively. The complexes were characterized by physicochemical and spectroscopic methods and also by single-crystal X-ray determination. The hydrazone ligands coordinate to the Mo atoms through their phenolate O, imine N and enolic O atoms. The Mo atoms are six-coordinated in octahedral geometries. The complexes show high catalytic activities and selectivities in the epoxidation of cyclohexene with tert-butylhydroperoxide as primary oxidant.