Hexa(1-vinylimidazole)Co(II) perchlorate

A new cobalt(II) complex of 1-vinylimidazole (vinim) has been synthesized as the perchlorate salt and structurally characterized. The molecular structure of the complex exhibits six coordination in which the geomety is a distorted octahedron. The vinylimidazole ring is coordinated through the imidazole nitrogen, as expected from earlier spectroscopic studies of related adducts. The space group is P2₁/n, with a = 8.512(2), b = 13.857(2), c = 16.146(2) Å, = 96.30(1)°, V = 989.31 ų, and Z = 2.     

Self-Assembly of Two Isomorphous Thiocyanate Complexes of Co(II) and Ni(II) with 3-Hydroxypicolinamide

Abstract  

The synthesis, thermal and spectral characterization, and crystal structure of isomorphous thiocyanate cobalt(II) and nickel(II) complexes with 3-hydroxypicolinamide (3-OHpia), [M(C₆H₆N₂O₂)₂(NCS)₂]·2H₂O, are reported. The metal(II) ions are chelated by two cis-oriented 3-OHpia and two thiocyanate ligands in distorted octahedral geometry. The distortion within the coordination sphere is mainly imposed by formation of the chelate rings. The compounds crystallize in monoclinic space group P2/c with two symmetrically independent molecules and a = 14.4945(2) ?, b = 8.5906(1) ?, c = 16.3865(3) ?, β = 105.987(2)°, Z = 4 (1) and a = 14.4927(5) ?, b = 8.5912(3) ?, c = 16.2712(6) ?, β = 105.740(4)°, Z = 4 (2). Commonly observed supramolecular amide synthons are not robust enough to accommodate thiocyanate ions and H₂O molecules. But instead, neutral complexes are linked through hydrogen bonds leading to two different hydrogen bonding ribbon motifs involving amide moieties and H₂O molecules [C(8)R ₂²(12) along c axis] and amide moieties and thiocyanate ions [C(8)R ₂²(16) along b axis] for symmetrically related molecules labelled as 1 [Co1 (1) and Ni1 (2)] and 2 [Co2 (1) and Ni2 (2)], respectively.     

Synthesis and Crystal Structure Determination of Dimeric Co(II) and Ni(II) with Pyridine 2,6-Dicarboxylic Acid

Abstract  

Two new dimeric complexes of Ni and Co with pyridine 2,6-dicarboxylic acid were synthesized, the structure of both these complexes were determined by single crystal X-ray crystallography and was characterized spectrally with the help of IR and UV spectrometers and the magnetic moments of both the reported complexes were recorded. Both of these complexes crystallize in the monoclinic space group P 2₁/c1. For the dimeric cobalt complex, formula C₁₄ H₂₁ Co₂ N₂ O₁₅; a = 8.3950(3) ?; α = 90°, b = 27.3702(8) ?; β = 98.211(2)°, c = 9.6235(3) ?; γ = 90° and Z = 3. For the dimeric Nickel complex, formula C₁₄ H₂₁ Ni₂ N₂ O₁₅, a = 8.330(10) A; α = 90°, b = 27.266(5) A; β = 98.61(10)^o, c = 9.653(10) A; γ = 90° and Z = 4. Both the dimeric complexes were observed to be hexa-coordinated with two different types of donor atoms (nitrogen and oxygen). Details of the synthesis, structures and spectroscopic properties have been discussed.     

Growth kinetics of ammonium oxalate monohydrate single crystals from aqueous solutions containing Co(II) and Ni(II) impurities

The growth kinetics of different faces of ammonium oxalate monohydrate (AO) single crystals from aqueous solutions containing different concentrations of Co(II) and Ni(II) ions at a constant temperature are described and discussed. It was found that: (1) at a given supersaturation σ, both Co(II) and Ni(II) ions lead to a decrease in the growth rates R of different faces of AO crystals, (2) the growth of a particular face of the crystals occurs above a critical supersaturation σ_d, but there is also another supersaturation barrier σ* when the rate abruptly increases with σ, and (3) the values of σ_d and σ* increase with increasing concentration c_i of the impurity. The experimental R(σ) data for different concentrations c_i of the impurities were analysed according to the model involving complex source of cooperating screw dislocations and concepts of instantaneous and time‐dependent impurity adsorption. Analysis of the data showed that: (1) adsorption of Co(II) and Ni(II) impurities occurs on the surface terrace of AO crystals, (2) there is a simple relationship between Langmuir constant K and the impurity concentration c_i* corresponding to maximum surface coverage, and (3) the ratio σ_d/σ* of the supersaturation barriers observed in the presence of both impurities increases with an increase in impurity concentration c_i, and may be explained from the standpoint of the mechanism of adsorption of impurity particles at kinks and ledges. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Transition metal(II) complexes of a biological buffer. Structural and spectroscopic study on Co(II), Ni(II), Cu(II), Zn(II), and Cd(II) complexes of N-[2-hydroxy-1,1-bis-(hydroxymethyl)ethyl]glycine

The structural and spectroscopic properties of complexes of N-[2-hydroxy-1,1-bis-(hydroxymethyl)ethyl]glycine (thmmg) with Co(II), Ni(II), Cu(II), Zn(II), and Cd(II) were investigated. The complex [Zn(thmmg)₂] crystallizes in the space groupP2₁/n, witha=8.796(2),b=9.050(3),c=9.926(2) Å,=97.35(1)° andZ=2; the copper(II) homolog is isomorphous. The complex [Ni(thmmg)₂]·6H₂O crystallizes in the space groupP2₁/n witha=8.432(8),b=8.495(2),c=15.967(1) Å,=95.57(2)° andZ=2; the cobalt(II) homolog is isomorphous. Ni(II) and Zn(II) complexes show an elongated octahedral coordination arising from two symmetry related amino acid molecules acting as a tridentate chelate through the amino nitrogen, one carboxylate oxygen, and one hydroxyl oxygen; the water molecules in the Ni(II) complex are not involved in metal coordination. The same ligand bonding mode may be suggested also for the Cu(II) and Co(II) complexes, while for Cd(II) only the nitrogen atom and the carboxylate oxygens seem to be involved in metal coordination.     

Synthesis and Characterization of Co(II) Coordination Polymer with a Flexible Bidentate Ligand

Crystallography Reports - A coordination polymer, {[Co(bib)3](BF4)2}n, was prepared for the first time at room temperature via the reaction between cobalt(II) chloride and flexible linker ligand,...     

Synthesis and Structural Characterization of Two Tetra-Coordinated Co(II) Complexes with Benzimidazole Derivatives

Crystallography Reports - Two mononuclear tetra-coordinated cobalt(II) complexes with molecular formula [Co(L)2(SCN)2] (L = 1-methylbenzimidazole (mbim), 1; L = 1-methyl-2-aminobenzimidazole...     

Two Co/Ni(II)-Based Coordination Polymers for Degradation of Dyes

Crystallography Reports - Two isostructural Co/Ni(II)-based coordination polymers, namely, {[Co1/2(bpba)(H2O)]?2H2O}n (1) and {[Ni1/2(bpba)(H2O)]?2H2O}n (2), where Hbpba = 3,5-bis...     

Kristallstrukturänderungen des Magnesiumnitrats-Hexahydrats,die infolge isodimorpher Substitution durch Co(II)- und Ni(II)-Ionen entstehen

The physico-chemical analysis data on the systems Mg(NO₃)₂ Co(NO₃)₂ H₂O and Mg(NO₃)₂ Ni(NO₃)₂ H₂O at 25.0°C have shown that due to isodimorphous substitution of Mg²⁺ in the crystals of Mg(NO₃)₂ · 6 H₂O for Co²⁺ or Ni²⁺, above a specific degree of ionic substitution, changes in the crystal structure of Mg(NO₃)₂ · 6 H₂O appear.     

Synthesis,structural, and spectroscopic characterization of hexakis (dimethyl sulfoxide)cobalt(II) tetrachlorocobaltate(II), [Co(Me2SO)6][CoCl4]

Well-formed single crystals of a compound having the empirical formula CoCl₂·3Me₂SO have been prepared using a vapour diffusion technique. X-ray diffraction methods confirm the previous spectrophotometric results of Cotton and Francis (1960a) and unequivocally demonstrate that this compound must be formulated as [Co(Me₂SO)₆]²⁺[CoCl₄]^2–. The compound crystallizes in the triclinic space groupP¯1 witha=18.601(3),b=9.613(2),c=9.044(2),=87.50(2)°,=98.64(2)°, =98.44(2)° andZ=2. Although a significant decrease of crystal quality with time and severe molecular disorder of Me₂SO are present, we have determined the coordination geometry around the cobalt centers. One cobalt atom is bound to six oxygen atoms of the Me₂SO moiety in a slightly distorted octahedral configuration; the mean Co-O distance is 2.083(12)Å. The second cobalt atom is surrounded by four chloride anions in an approximately tetrahedral configuration; the mean Co-Cl distance is 2.284(6) Å. The structure of the complex has been also investigated by means of ir measurements in the 4000-200 cm^–1 range.     

Structure of dichloroethanolaminecopper(II) and dibromoethanolaminecopper(II)

CuCl₂(NH₂CH₂CH₂OH) is monoclinic, space group C2/c, witha+11.092(2),b+10.012(2),c+6.401(1) Å, =121.71(1)°, andV=604.8(2)ų withZ+4. The structure was refined to a final value ofR+0.27 for 518 unique observed reflections with |F|>3. The ethanolamine and halide ions coordinate to the copper(II) ion forming a pseudoplanar four-coordinate monomeric CuCl₂L² complex (L²+bidentate ligand). The copper ion also interacts with the halides of neighboring complexes through the formation of semi-coordinate Cu-Cl linkages (2.926(1) Å) between oligomers. The copper thus attains a 4+2 elongated octahedral coordination geometry. In this space group, the ligand is statisticallydisordered The Cu-Cl distance is 2.267(1)Å while the Cu-N/O distances are 2.025(2)Å. The dibromide structure is isomorphous with the dichloride structure, with space group C2/c, anda+11.285(2),b+10.218(2),c+6.715(1) Å, =121.65(1)°, andV=659.2(2)ų.     

Structure and characterization of hexakis(imidazole) cobalt(II) complexes: [Co(Im)6(OBz)2] and [Co(Im)6(mB)2] (Im = imidazole, OBz = benzoate, mB = p-methoxybenzoate)

The crystal and molecular structures of the complexes of [Co(Im)₆(OBz)₂] and [Co(Im)₆(mB)₂] (Im = imidazole, OBz = benzoate, mB = p-methoxybenzoate) have been determined by X-ray crystallography. The crystal structures are very similar and consist of discrete molecules of [Co(Im)₆(OBz)₂] and [Co(Im)₆(mB)₂], respectively. They both crystallize in the triclinic system, space group the former with lattice parameters a = 7.6934(3), b = 10.4518(5), c = 11.6088(5) Å, = 73.920(1), = 79.023(1), = 73.681(1)°, and Z = 1; the latter with a = 9.8336(3), b = 10.5509(2), c = 10.8889(3) Å, = 61.450(1), = 76.832(1), = 71.157(1)°, and Z = 1. The cobalt(II) ions have octahedral geometry with a CoN₆ chromophore. In the solid state, the complexes all form a three-dimensional network through N—H···O hydrogen bonds. The electronic spectra and IR spectra data are in agreement with the structural data.     

Influence of complex formation upon inclusion of Mn(II), Co(II), Ni(II), and Cu(II) in ZnC2O4·2H2O

The inclusion of 3d‐impurities Mn(II), Co(II), Ni(II) and Cu(II) in a crystalline precipitate of ZnC₂O₄·2H₂O is investigated. This study is a part of the systematic one deal with the mechanism of inclusion of 3d‐ions in sparingly soluble oxalate systems. The experiments are carried out in bi‐ end multi‐component systems at two different mediums – one with deficiency of oxalate ions, another with excess. The insertion of 3d‐ions upon mass crystallization of ZnC₂O₄·2H₂O does not proceed by a simple ionic substitution. The results show that the inserted amount of impurity depends on some physicochemical characteristics of the neutral monooxalato complexes [MnC₂O₄]^o, [CoC₂O₄]^o, [NiC₂O₄]^o and [CuC₂O₄]^o. Good agreement between included impurity and the concentration of its complex in the solution is established. The stability constant of monooxalato complex affects the impurity inclusion. This effect depends on the medium nature. In the deficiency of oxalate ions the factor determining the inclusion is thermodynamic one – stability of monooxalato complexes. In the excess of oxalate ions inserted amount depends on kinetic factor – the formation rate of these complexes. In the term of that the insertion of Mn(II) is definitely different in the two mediums while that of the Ni (II) does not depend on the medium. The copper shows deviation from overall dependence in the two mediums due to the Jahn‐Teller distortion. Its double decreasing insertion in the excess of oxalate ions is related with stabilization of [Cu(C₂O₄)2]^2‐. The conclusions presume that by varying the background medium and taking in view the ions present in the solution, the amount of inserted impurities can be predicted and controlled. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Cobalt(II) and nickel(II) complexes ofN-protected amino acids. Crystal and molecular structure of bis (N-acetylglycinato)tetraaquocobalt(II)

Binary complexes of formula [M(II)(acgly)₂(H₂O)₄] (M(II)=Co(II), Ni(II), acgly=N-acetylglycinate ion) were synthesized, and for the Co(II) complex the crystal and molecular structure was determined. The crystals are monoclinic, space groupP2₁/c,a=4.838(1),b=10.785(2),c=14.340(6) Å,=96.96(2)°,Z=2. The structure was solved by the heavy-atom method and refined through full-matrix least-squares calculations toR=0.0394 for 1069 observed reflections. The coordination around the cobalt atom is slightly elongated octahedral arising from one carboxylate oxygen of each of the two centrosymmetrically related monodentateN-acetylglycinate anions and four water molecules.     

Photo-quenched of the luminiscence signal in Co(II)-doped alumina prepared by the sol-gel method

Co(II)-doped alumina monoliths prepared by the sol-gel method were laser irradiated producing fluorescence. The intensity of this defect-induced fluorescence was exponentially reduced with the irradiation time to practically disappear. The rate the fluorescence intensity decays was modeled as a double exponential function of the irradiation time; the characteristic times associated with the decays are in the range of seconds. The suppression of the luminescence was associated with the local heating produced by the highly focused laser beam in a small area (≈ 2 μm in diameter) on the sample. This heating process reduces physical (grain boundaries and surface states) and chemical (oxygen vacancies) defects present in the sol-gel samples. Some residual fluorescence still remains after long periods of illumination. The characteristic times for alumina samples are compared with those obtained for other metal oxides prepared also by the sol-gel method.