Studies of bicarbonate binding by dinuclear and mononuclear Ni(II) complexes

Bicarbonate ion reacts with the dinuclear nickel(II) complex containing the taec ligand (taec = N,N',N' ',N' '-tetrakis(2-aminoethyl)-1,4,8,11-tetraazacyclotetradecane) in buffered aqueous solution to form the mu-eta(2),eta(2)-carbonate complex with a large effective binding constant for bicarbonate ion, log K(B) = 4.39 at pH = 7.4. In contrast, the dinuclear nickel(II) complex containing the o-xyl-DMC(2) ligand (o-xyl-DMC(2) = alpha,alpha'-bis(5,7-dimethyl-1,4,8,11-tetraazacyclotetradecan-6-yl)-o-xylene) does not react with bicarbonate or carbonate ion in aqueous solution. In propylene carbonate, the reaction of [Ni(2)(o-xyl-DMC(2))](4+) with bicarbonate proceeds rapidly to form the mu-eta(1),eta(1)-carbonate complex. The structure of this carbonate complex has been determined by an X-ray diffraction study that confirms the mu-eta(1),eta(1)-carbonate binding mode. A mononuclear analogue of [Ni(2)(taec)](4+), [Ni(2,3,2-tetraamine)](2+) does not form a detectable mononuclear or dinuclear product with bicarbonate ion in aqueous solution, but [NiDMC](2+) (DMC = 5,7-dimethyl-1,4,8,11-tetraazacyclotetradecane) reacts slowly with carbonate ion in aqueous solution to form a 2:1 complex.     

Monomeric and polymeric dinuclear complexes of Co(II) or Ni(II) with calix[4]arene-tetraphosphineoxide

Monomeric and polymeric 1:2 complexes of a novel calix[4]arene-tetraphosphineoxide with Co(II) or Ni(II) nitrates were synthesized and analyzed by the X-ray method. In the monomeric complexes each metal cation is coordinated by two bidentate NO₃-ligands as well as by two proximal P=O groups at the calixarene skeleton. In the nickel metallopolymer one sort of the cations is bound by the two proximal P=O-groups but other cations link neighboring calixarene molecules through Р=О···Ni···O=P chains. The complexes possess molecular cavities or channels filled by solvent molecules. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

New Ni(II) and Co(II) coordination compounds construction from the ditopic 1,2,3-triazol-based aromatic heterocyclic polycarboxylic ligand

Mononuclear compound I ([Co(Ptia)₂(H₂O)₄] ? H₂O) and 1D chain compound II ([Ni₄(Cptia)₄(H₂O)₁₂]_∞) have been constructed from the new ditopic 1,2,3-trazol-based aromatic heterocyclic carboxylic ligand, 4-(4-carboxy-1H-1,2,3-triazol-1-yl) benzoic acid) (H₂Cptia), under different pH conditions by using the hydrothermal method. Their structure was characterized by single crystal X-ray diffraction (СIF files CCDC nos. 1409531 (I) and 1409531 (II)), IR spectra, and elemental analysis. Compound I is a mononuclear compound. In II, two sets of parallel arrangement 1D chains orient in different directions. The results of their magnetic measurements display the antiferromagnetic interaction exists among the paramagnetic ions.     

Coordination compounds of Co(II), Ni(II) and Cu(II) with capric acid hydrazide

The reaction of aquo-ethanolic solutions of Co(II), Ni(II) and Cu(II) salts and ethanolic solution of capric acid hydrazide (L) yielded paramagnetic, high-spin bis- and tris(ligand) chelate complexes. The tris(ligand) complexes, [ML ₃]X ₂·nH₂O [M=Co(II), Ni(II);X=NO ₃ ^– , ClO ₄ ^– , 1/2SO ₄ ^2– ], have an octahedral structure formed on account of the bidentate (NO) coordination of three neutral hydrazide molecules. In the bis(ligand) complexes,ML ₂(NCS)₂ [M=Co(II), Ni(II)] and CuL ₂ X ₂·nH₂O (X=NO ₃ ^– , ClO ₄ ^– and 1/2SO ₄ ^2– ), the oxoanions and NCS^– take also part in coordination. The complexes have been characterized by elemental analysis, IR spectra, magnetic measurements, molar conductivity and TG analysis.

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Caprinsäurehydrazid-Komplexe von Co(II), Ni(II) und Cu(II)

Zusammenfassung Durch die Reaktion von wäßrig-ethanolischen Lösungen von Co(II)-, Ni(II)-und Cu(II)-Salzen mit einer ethanolischen Lösung von Caprinsäurehydrazid (L) wurden paramagnetische high-spin Bis- und Tris-Ligand-Chelatkomplexe erhalten. Tris-Ligand-Komplexe des Typs [ML ₃ X ₂·nH₂O [M=Co(II), Ni(II);X=NO ₃ ^– , ClO ₄ ^– , 1/2SO ₄ ^2– ], die eine oktaedrische Struktur besitzen, entstehen durch die Koordination von drei neutralen zweizähnigen (NO)-Hydrazidmolekülen. Bei den Bis-Ligand-KomplexenML ₂(NCS)₂ [M=Co(II), Ni(II)], sowie bei den Bis-Ligand-Komplexen CuL ₂ X ₂·nH₂O (X=NO ₃ ^– , ClO ₄ ^– , 1/2SO ₄ ^2– ) nehmen bei der Koordination außer Hydrazid auch die Säurereste teil. Die Komplexe wurden durch Elementaranalyse, IR-Spektren, magnetische Messungen, molare Leitfähigkeit und TG-Analysen charakterisiert.

     

Study of binary complexes of Cu(II), Ni(II) and Co(II) with sulfamethazine by voltammetry

Cyclic voltammetry (CV) and square-wave voltammetry (SWV) techniques have been used to study the binary complexes of Co(II), Ni(II) and Cu(II) with sulfamethazine (SMZ) at a static mercury drop electrode (SMDE) in 0.04 M Britton-Robinson (B-R) buffer. SMZ gave three peaks at 0.01, −1.32 and −1.55 V. Cu(II)-SMZ complex was recognized by a cathodic peak at −0.38 V. Ni(II)-SMZ complex was reduced at more positive potential (−0.77 V) than that of the hydrated Ni(II) ions (−1.08 V). Co(II)-SMZ complex is investigated at pH 7 and 8. The Co(II) complex at pH 7 is appeared as a shoulder at −1.19 V, whereas this peak becomes a well-separated form at pH 8. The study indicated that the SMZ serves as a catalyst in the reduction of Co(II) and Ni(II) ions. From electronic spectra data of the complexes, their stoichiometries of 1: 2 (metal-ligand) in aqueous medium are determined. The stability constants of the complexes are in agreement with the Irwing-Williams series (Co < Ni < Cu).     

Mononuclear Ni(II)-thiolate complexes with pendant thiol and dinuclear Ni(III/II)-thiolate complexes with Ni...Ni interaction regulated by the oxidation levels of nickels and the coordinated ligands

Compared to [Ni(II)(SePh)(P(o-C(6)H(3)-3-SiMe(3)-2-S)(2)(o-C(6)H(3)-3-SiMe(3)-2-SH))]- (1a) and [Ni(II)(Cl)(P(o-C(6)H(3)-3-SiMe(3)-2-S)(2)(o-C(6)H(3)-3-SiMe(3)-2-SH))]- (3a) with a combination of the intramolecular [Ni...H-S] and [Ni-S...H-S] interactions, complexes [NiII(SePh)(P(o-C(6)H(3)-3-SiMe(3)-2-S)(2)(o-C(6)H(3)-3-SiMe(3)-2-SH))]- (1b) and [Ni(II)(Cl)(P (o-C(6)H(3)-3-SiMe(3)-2-S)(2)(o-C(6)H(3)-3-SiMe(3)-2-SH))]- (3b) with intramolecular [Ni...H-S] interaction exhibit lower nu(S-H) stretching frequencies (2137 and 2235 cm(-1) for 1b and 3b vs 2250 and 2287 cm(-1) for 1a and 3a, respectively) and smaller torsion angles (27.2 degrees for 3b vs 58.9 and 59.1 degrees for 1a and 3a, respectively). The pendant thiol interaction modes of 1a, 3a, and 3b in the solid state are controlled by the solvent pairs of crystallization. Oxygen oxidation of dinuclear [Ni(II)(P(o-C(6)H(3)-3-SiMe(3)-2-S)(2)(o-C(6)H(3)-3-SiMe(3)-2-SH))](2) (4) yielded thermally stable dinuclear [Ni(III)(P(o-C(6)H(3)-3-SiMe(3)-2-S)(2)(o-C(6)H(3)-3-SiMe(3)-2-mu-S))](2) (5). The two paramagnetic d(7) Ni(III) cores (S = 1/2) with antiferromagnetic coupling (J = -3.13 cm(-1)) rationalize the diamagnetic property of 5. The fully delocalized mixed-valence [Ni(II)-Ni(III)] complexes [Ni2(P(o-C(6)H(3)-3-SiMe(3)-2-S)(3))(2)]- (6) and [Ni(2)(P(o-C(6)H(3)-3-SiMe(3)-2-S)(3))(P(o-C(6)H(3)-3-SiMe(3)-2-S)(2)(o-C(6)H(3)-3-SiMe(3)-2-SCH(3)))] (7) were isolated upon the reduction of 5 and the methylation of 6, respectively. The electronic perturbation from the sulfur methylation of 6 triggers the stronger Ni...Ni interaction and the geometrical rearrangement from the diamond shape of the [NiS(2)Ni] core to the butterfly structure of [Ni(mu-S)(2)Ni] to yield 7 with Ni...Ni distances of 2.6088(1) A. The distinctly different Ni...Ni distances (2.6026(7) for 5 and 2.8289(15) A for 6) and the coordination number of the nickels indicate a balance of geometrical requirements for different oxidation levels of [PS(3)Ni-NiPS(3)] cores of 5 and 6.     

Acid Co(II) and Ni(II) trifluoroacetate complexes: Synthesis and crystal structure

Anhydrous and partially hydrated acid trinuclear trifluoroacetates of divalent transition metals of the composition [M₃(CF₃COO)₆(CF₃COOH)₆)](CF₃COOH) and [M₃(CF₃COO)₆(CF₃COOH)₂(H₂O)₄)](CF₃COOH)₂, respectively, where M = Co (I, III) Ni (II, IV), were synthesized and studied by X-ray diffraction. Complexes I and II were obtained by crystallization from solutions of M(CF₃COO)₂ · 4H₂O in trifluoroacetic anhydride; complexes III and IV were synthesized under the same conditions with the use of 99% trifluoroacetic acid as a solvent. Crystals I are triclinic: space group $P\bar 1$ , a = 13.199(6) Å, b = 14.649(6) Å, c = 15.818(6) Å, α = 90.04(4)°, β = 114.32(4)°, γ = 108.55(4)°, V = 2611.3(19) ų, Z = 2, R = 0.0480. Crystals II are trigonal: space group $R\bar 3$ , a = 13.307(2) Å, c = 53.13(1) Å, V = 8148(2) ų, Z = 6, R = 0.1112. Crystals III are triclinic: space group $P\bar 1$ , a = 9.001(8) Å, b = 10.379(9) Å, c = 12.119(9) Å, α = 83.67(5)°, β = 72.33(5)°, γ = 83.44(5)°, V = 1068.3(15) ų, Z = 1 Å, R = 0.1031. Crystals IV are triclinic: space group $P\bar 1$ , a = 9.121(18) Å, b = 10.379(2) Å, c = 12.109(2) Å, α = 84.59(3)°, β = 72.20(3)°, γ = 82.80(3)°, V = 1080.94(40) ų, Z = 1, R = 0.0334.     

Thermal behavior of Co(II) and Ni(II) hydroxycarboxylate complexes obtained by two original synthesis methods

This paper presents a facile and rapid synthesis route of metallic Ni and Co nanocrystallites at ~150 °C in the mixture composed of the corresponding metal nitrates and 1,3-propanediol, as reducing agent. The metal oxides NiO, CoO, Co₃O₄ nanocrystallites were, also, successfully synthesized by thermal decomposition at 300 °C of the hydroxycarboxylate coordination products, obtained in the redox reaction between 1,3-propanediol and Ni(II) and Co(II) nitrates. The formation of the Ni(II) and Co(II) hydroxycarboxylate complexes depends on the diol which generates the carboxylate anion, the transition metal and the process parameters. Ni(II) and Co(II) nanocomposites were also synthesized by thermal decomposition of the complex combinations formed within the pores of the hybrid silica gels. One of the purposes of the present study was to investigate the phase constitution of the composites obtained in similar synthesis conditions, from Ni(II) and Co(II) complex combinations embedded in silica gels. These gels were submitted to various thermal treatments and the changes occurring during these treatments were described by X-ray diffraction. Thermal analysis is an excellent tool for the study of the processes implied in the formation and decomposition of the Co(II) and Ni(II) carboxylate complexes. X-ray diffraction evidenced the nanometer sized metal and/or metal oxide phases.     

Coordination compounds of heterocyclic azo derivatives. III. Co(II), Ni(II) and Cu(II) complexes of some arylazo-4,5-diphenylimidazole derivatives

The 3d transition metalion [Co(II), Ni(II) and Cu(II)] complexes of some 4,5-diphenylimidazole azo derivatives have been isolated and characterized by chemical analysis, conductance, electronic and IR spectra. These dyes are characterized by a high tendency towards complex formation with the neutral molecules coordinated to the metal ion as bidentate ligands. The molecular formula of the 1:1 and 1:2 complexes are suggested to be [MLX ₂(H₂O)₂] and [ML ₂ X ₂] or [ML ₂ X ₂]·2H₂O respectively, whereX=Cl^– or NO₃. the different bands observed in the visible spectra of methanolic solutions of the complexes have been assigned to the possible electronic transition type (L MCT and d-d). It is suggested that the complexes studied have a distorted octahedral geometry.

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Koordinatsverbindungen von heterocyclischen Azo-Derivaten, 3. Mitt.: Co(II)-, Ni(II)- und Cu(II)-Komplexe einiger Arylazo-4,5-diphenylimidazol-Derivate

Zusammenfassung Es wurden einige Komplexe von 4,5-Diphenylimidazol-azo-Derivaten mit den 3 d-Übergangsmetallen Co(II), Ni(II) und Cu(II) isoliert und mittels chemischer Analyse, Leitfähigkeitsmessungen und den Elektronen- bzw. IR-Spektren charakterisiert. Diese Farbstoffe zeigen eine sehr starke Tendenz zur Komplexbildung, wobei die neutralen Moleküle als zweizähnige Liganden an das Metallion koordinieren. Die Formeln für die 1:1- und 1:2-Komplexe werden mit [MLX ₂(H₂O)₂] und [ML ₂ X ₂] bzw. [ML ₂ X ₂]·2H₂O vorgeschlagen (X=Cl^– oder NO ₃ ^– ). Die verschiedenen Absorptionsbanden in den VIS-Spektren in methanolischer Lösung werden den möglichen e-Übergängen (L MCT und d-d) zugeordnet. Für die Komplexe werden verzerrte oktaedrische Geometrien vorgeschlagen.

     

Characterization and TG-MS studies of lactato and bipyridine-lactato complexes of Co(II) and Ni(II)

Two lactates and four new mixed ligand complexes with formulae Co(lact)₂·2H₂O, Ni(lact)₂·3H₂O, Co(4-bpy)(lact)₂, Co(2,4'-bpy)₂(lact)₂, Ni(4-bpy)(lact)₂·2H₂O and Ni(2,4'-bpy)₂(lact)₂ (where 4-bpy=4,4'-bipyridine, 2,4'-bpy=2,4'-bipyridine, lact=CH₃CH(OH)COO^-) were isolated and investigated. The thermal behaviour of compounds was studied by thermal analysis (TG, DTG, DTA). In the case of hydrated complexes thermal decomposition starts with the release of water molecules. The compounds decompose at high temperature to metal(II) oxides in air. A coupled TG-MS system was used to analyse the principal volatile products of thermolysis and fragmentation processes of obtained complexes. This revised version was published online in July 2006 with corrections to the Cover Date.     

Coordination compounds of Co(II), Ni(II), and Cu(II) valerates and benzoates with semicarbazide

Complexes of Co(II), Ni(II), and Cu(II) valerates and benzoates with semicarbazide were prepared. The compounds were characterized by chemical analysis, X-ray phase analysis, IR spectroscopy, diffuse reflection spectroscopy, and thermal gravimetric analysis.     

Co(II), Cu(II) and Zn(II) dinuclear complexes of a polypodal ligand containing phenolate and pyridyl donor groups

Acetate and perchlorate dinuclear metal complexes of Co(II), Cu(II) and Zn(II) with the cresolate polypodal ligand having mixed phenolate and pyridyl pendant functionalities, H₃L, have been synthesized. The complexes were characterized by microanalysis, LSI mass spectrometry, IR, UV–Vis spectroscopy, magnetic studies and conductivity measurements. Crystal structures of H₃L, [Cu₂(HL)(OAc)(H₂O)₂](OAc)·1.5H₂O and [Zn₂L(CH₃OH)₃](ClO₄)CH₃OH·2H₂O complexes, have been also determined.     

Dinuclear tetrapyridyl pendant-armed azamacrocyclic complexes of Co(II), Ni(II), Cu(II) and Cd(II)

The coordination capability of the new tetrapyridyl pendant-armed azamacrocyclic ligand L, towards Co(II), Ni(II), Cu(II) and Cd(II) ions was studied. The ligand and the complexes were characterized by microanalysis, LSI mass spectrometry, IR, UV-Vis and NMR spectroscopy, magnetic studies and conductivity measurements. Crystal structures of [Co₂L(CH₃CN)₂](ClO₄)₄·2CH₃CN and [Cd₂L(NO₃)₂](NO₃)₂·2H₂O complexes have been determined. The X-ray studies show the presence of dinuclear endomacrocyclic complexes with the metal ion in a similar distorted octahedral environment, coordinated by one pyridyl bridgehead group, two amine nitrogen atoms and two pyridyl pendant-arms. The sixth coordination position around the metal ion is completed by one acetonitrile molecule in [Co₂L(CH₃CN)₂](ClO₄)₄·2CH₃CN and by one monodentate nitrate anion in [Cd₂L(NO₃)₂](NO₃)₂·2H₂O. Different sort of intramolecular non-classical hydrogen bonds were found in the crystal lattice of both structures.     

Synthesis of pendant-type anthraquinone-bridged cofacial dinuclear platinum(II) complexes and their emission properties

Anthraquinone-bridged mononuclear and dinuclear complexes, [PtCl(AQ-amide-tpy)](PF6) (1), [Pt2Cl2(AQ-amide-tpy2)](PF6)2 (2), and [Pt2Cl2(AQ-eth-tpy2)](PF6)2 (3), were synthesized and their photochemical properties were investigated. Amide-bound mononuclear complex 1 exhibited only metal-to-ligand charge transfer (MLCT) absorption and emission, whereas dinuclear complex 2 exhibited a low-energy emission around 700 nm at room temperature. Emission lifetime analysis indicated that this emission was originated from the metal-metal-to-ligand charge transfer (MMLCT) excited state, implying the existence of an intramolecular Pt-Pt interaction at the photoexcited state. 3 with rigid ethynylene linkers showed a low-energy absorption around 520 nm (epsilon = approximately 1100 M(-1) cm(-1)) in addition to an 1MLCT absorption, which was ascribed to a 3MLCT absorption from the consideration of the Pt-Pt distance on a geometry-optimized structure. The emission of 3 appeared at 600 nm, which is higher in energy compared with the emission of 2. It is postulated that the restriction of the Pt-Pt distance flexibility in the rigid structure of 3 prevents the significant increase of the Pt-Pt interaction at the excited state.     

Orotic acid complexes of Co(II), Ni(II), Zn(II) and Cd(II) with imidazole

The [Co(HOr)(H₂O)₂(im)₂] (1), [Ni(HOr)(H₂O)₂(im)₂] (2), [Zn(H₂O)₂(im)₄](H₂Or)₂ (3) and [Cd(HOr)(H₂O)(im)₃] (4) complexes (H₃Or: orotic acid, im: imidazole) were synthesized and characterized by elemental analysis, magnetic and conductance measurements, UV-vis and IR spectra. The thermal behaviour of the complexes was also studied by simultaneous thermal analysis techniques (TG, DTG and DTA). The orotate ligand (HOr²⁻) coordinated to the Co(II), Ni(II) and Cd(II) ions are chelated to the deprotonated pyrimidine nitrogen (N₍₃₎) and the carboxylate oxygen, while do not coordinate to the Zn(II) ion is present as a counter-ion (H₂Or⁻). The first thermal decomposition process of all the complexes is endothermic deaquation. This stage is followed by partially (or completely) decomposition of the imidazole and orotate ligands. In the later stage, the remained organic residue exothermically burns. On the basis of the first DTG_max, the thermal stability of the complexes follows order: 2, 176°C>1, 162°C>4, 155°C>3, 117°C in static air atmosphere. The final decomposition products which identified by IR spectroscopy were the corresponding metal oxides.     

Synthesis and structural studies of Co(II), Ni(II) and Cd(II) complexes with 2-acetylpyridine

Three new mononuclear complexes [Co(2-Acpy)₂(H₂O)₂](NO₃)₂ (1), [Ni(2-Acpy)₂(H₂O)₂](NO₃)₂ (2) and [Cd(2-Acpy)₂(NO₃)₂] (3) (2-Acpy = 2-acetylpyridine) have been synthesized and characterized by elemental analysis, IR and UV–Vis spectroscopy. The structures of 1 and 3 were accomplished by single crystal X-ray diffraction. Crystallographic investigation of 1 reveals monomeric, dicationic units in which the cobalt(II) ion is six-coordinate. The coordination sphere is formed by two N, O bidentate acetylpyridine ligands and two water molecules. The crystal structure of 3 consists of monomeric units in which the cadmium is eight-coordinate. Both the organic ligand and nitrate groups are bidentate chelators. The supramolecular solid-state architecture is sustained by π–π interactions.