Disproportionation of manganese(II) (1-hydroxyethylidene) diphosphonate in reaction with 2-aminoethanol

Reaction of poorly soluble manganese(II) bis(1-hydroxyethylidene)diphosphonate tetrahydrate Mn(H₃L)₂ · 4H₂O with 2-aminoethanol H₂NCH₂CH₂OH in an aqueous solution on heating to 70–80°C causes the initial formation of soluble tris(2-hydroxyethanaminium) manganese(II) bis(1-hydroxyethylidene) diphosphonate Mn(H₃L)₂ · 3H₂NCH₂CH₂OH · 4H₂O, which next disproportionates into poorly soluble 2-hydroxyethanaminium manganese(II) (1-hydroxyethylidene)diphosphonate MnH₂L · H₂NCH₂CH₂OH and metal-cation-free coordination polymer of (1-hydroxyethylidene)diphosphonic acid with 2-aminoethanol. Poorly soluble MnH₂L · H₂NCH₂CH₂OH can be readily converted into the soluble form by treatment with 2-aminoethanol or 2-amino-2-(hydroxymethyl)propane-1,3-diol H₂NC(CH₂OH)₃.     

Dinuclear Cobalt(III) Complexes Showing a Co2O2 Metallacycle

The heptadentate Schiff base H₃L reacts with cobalt(II) acetate in methanol to form the discrete dinuclear complex Co₂L(OAc)₂(OMe)(H₂O)₂ ( 1 ·2H₂O). The reaction of 1 ·2H₂O with NMe₄OH·5H₂O in methanol gives rise to displacement of the acetate by methanolate groups, yielding Co₂L(OMe)₃(H₂O) ( 2 ·1H₂O). Recrystallizations of the Schiff base, 1 ·2H₂O and 2 ·H₂O in different solvents, produce single crystals of H₃L, 1 ·2.5H₂O and 2 ·2MeOH, respectively. The crystal structures of 1 ·2.5H₂O and 2 ·2MeOH show the cobalt atoms double bridged by and endogenous phenol oxygen atom and an exogenous methanolate oxygen donor, giving rise to Co₂O₂ cores with Co···Co distances of ca. 2.87 Å.     

Versatile coordinating behaviour of bis(acylhydrazone) ligands derived from imino- and methyl-iminodiacetic acid diethyl ester. Antimicrobial properties of their trinuclear copper(II) complexes

The coordinating properties of a new bis(pyridylhydrazone) ligand derived from iminodiacetic acid diethyl ester and 2-pyridinecarboxaldehyde (picolinaldehyde) H₃Imdp and of the bis(salicylhydrazone) H₅Imds and H₄MeImds ligands derived, respectively, from iminodiacetic acid diethyl ester and from methyl-iminodiacetic acid diethyl ester and salicylaldehyde were considered, by means of analytical and spectroscopic methods, towards first row transition metal ions. These ligands showed various coordination modes in complexation with Cu(II), Co(II), Mn(II) and Zn(II) ions. In particular, we have synthesized and characterized, by analytical, ¹H NMR and IR techniques, tri-, di- and mononuclear metal complexes of formula Co₃(HImdp)(NO₃)₄·2H₂O, Cu₃(HImdp)(NO₃)₄·C₂H₅OH·H₂O, Cu₃(HImdp)Cl_4, Zn₂(H₃Imdp)(ClO₄)₄·2H₂O, Co₃(HImds)Cl₂·CH₃OH·H₂O, Zn₂(H₃Imds)Cl₂·2H₂O, Co(H₄Imds)NO₃·2H₂O, Mn(H₄Imds)Cl·CH₃OH·H₂O, Cu(H₃Imds)·CH₃OH·H₂O and Cu(H₂MeImds)^.CH₃OH·3H₂O. Antibacterial, antifungal and antiprotozoal properties of H₅Imds and H₃Imdp together with three copper(II) trinuclear species of H₅Imds of formula Cu₃(HImds)(NO₃)₂^.2CH₃OH·2H₂O, Cu₃(HImds)(ClO₄)₂^.EtOH·2H₂O and Cu₃(HImds)SO₄·4H₂O are also discussed. The H₅Imds ligand and their trinuclear copper(II) complexes showed good activities versus Trichomonas vaginalis, Staphylococcus epidermidis and Acanthamoeba castellanii.     

Synthesis,characterization, electrochemical and crystal structure investigation of bis(2-((2-aminoethylimino)methyl)-6-methoxyphenolato) cobalt(III)

The mononuclear cobalt(III) complex [Co(L)₂]Cl ·?H₂O (1) (where L is H₂N(CH₂)₂N=CC₆H₃(OMe)(O^?)) has been prepared and characterized by IR, UV-Vis spectroscopy, conductivity measurements, elemental analysis, TGA, cyclic voltammetry and an X-ray structure determination. The cobalt(III) coordination sphere in [Co(L)2] is cis-CoN₄O₂ with the NNO ligands. Electrochemical studies of 1 using cyclic voltammetry indicate an irreversible cathodic peak (E _pc, ca ?0.60 V) corresponding to reduction of cobalt(III) to cobalt(II).     

Mechanism of thermal decomposition of cobalt acetate tetrahydrate

The thermal decomposition of cobalt acetate tetrahydrate (Co(CH₃COO)₂ · 4H₂O) has been studied via thermogravimetric (TG) analysis, in situ X-ray powder diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR). The results of TG and XRD showed that the parent salt melted and then the dissolved crystalline water was vaporized in two steps. The dehydration process was followed by a major step concerning the decomposition of the acetate group, leading to basic acetate as an intermediate, which then produced CoO and Co in N₂ and H₂ atmosphere, respectively. Three decomposition intermediates Co(CH₃COO)₂ · 0.5H₂O, Co(CH₃COO)₂, and Co(OH)(CH₃COO) were presumed. In situ XRD experiments revealed that the intermediate basic acetate was poorly crystallized or even amorphous. Evolved gases analysis indicated that the volatile products of acetate decomposition were water vapor, acetic acid, ethylenone, acetone, and CO₂. A detailed thermal decomposition mechanism of Co(CH₃COO)₂ · 4H₂O was discussed.     

Synthesis and Magnetic Properties of Two New Cobalt Complexes Constructed by Semirigid V‐shaped 5‐(4‐Carboxyphenoxy)‐pyridine‐2‐carboxylic Acid

Two cobalt complexes, [Co₃(L)₂(CH₃OH)₂(μ₃‐OH)₂] ( 1 ) and [Co(L)(bpe)_0.5] · H₂O ( 2 ) [H₂L = 5‐(4‐carboxyphenoxy)‐pyridine‐2‐carboxylic acid; bpe = 1, 2‐bis(4‐pyridyl)ethylene] were synthesized and fully characterized by elemental analyses, IR spectroscopy, single‐crystal X‐ray diffraction, thermogravimetric analysis (TGA), and magnetic analysis. Complex 1 has a two‐dimensional (2D) structure with puckered Co–O–Co chains, and 2 displays a three‐dimensional (3D) network containing one‐dimensional rectangular channels with dimensions of 9.24 × 13.84 Å. In complex 1 , variable‐temperature magnetic susceptibility measurements indicate antiferromagnetic interactions between cobalt magnetic centers.     

Synthesis, thermal and calorimetric investigations of cobalt(ii) trihydrogen hexaoxoperiodate tetrahydrate

A new cobalt(II) trihydrogen hexaoxoperiodate tetrahydrate has been synthesized: CoH₃IO₆·4H₂O and has been characterized by quantitative analysis, TG, DTA, DSC and IR spectroscopy. Based on DTA and DSC data, a thermal decomposition scheme has been proposed for this complex.     

New crystal forms of tris(2-aminoethanolato-O,N)cobalt(III): Structures and properties

Crystal forms of cobalt(III) tris(2-aminoethanolate) hydrates, i.e., red cubic crystals of the composition fac-[Co(NH₂CH₂CH₂O)₃] · 5.44H₂O (fac-I · 5.44H₂O) and blue prismatic crystals of the composition mer-[Co(NH₂CH₂CH₂O)₃] · 3H₂O (mer-I · 3H₂O) were studied by the ⁵⁹Co, ¹³C NMR and X-ray diffraction methods. It was found that mer-[Co(NH₂CH₂CH₂O)₃] · 3H₂O (mer-I · 3H₂O) is a new pseudopolymorphic modification of fac-[Co(NH₂CH₂CH₂O)₃] · 3H₂O (fac-I · 3H₂O), while fac-I · 3H₂O represents a new polymorphic modification of the complex mer-[Co(NH₂CH₂CH₂O)₃] · 3H₂O (mer-I · 3H₂O) described previously. The comparative analysis of the spectra revealed dynamic equilibrium between these geometric isomers; the fac-isomer is stable in aqueous solutions.     

Cu(OAc)2·H2O/NH2OH·HCl/CH3COONa: A Facile and Efficient Catalyst System for Copper‐catalyzed Azide–Alkyne Click Reactions in Water

A facile and efficient protocol has been developed for synthesis of 1,4‐disubstituted 1,2,3‐triazoles in good to excellent yields using Cu(OAc)₂·H₂O (0.5 mol%)/NH₂OH·HCl (0.5 mol%)/CH₃COONa (1.0 mol%) as the catalyst system. The presence of CH₃COONa (2 equiv) could ensure the in situ generation of Cu₂O as the active catalyst instead of CuCl from Cu(OAc)₂·H₂O (1 equiv)/NH₂OH·HCl (1 equiv). This protocol could be carried out in water under mild conditions.     

Zinc and Cobalt Complexes Derived from Tetradentate Tripodal Ligands with N2O2 Donorset as Model Compounds for Phosphatases

Starting from the tripodal tetradentate ligands ‐(3,5‐dibromo‐2‐hydroxybenzyl)(2‐hydroxybenzyl)(2‐pyridyl)methylamine (H₂L1), (3,5‐dibromo‐2‐hydroxybenzyl)(2‐hydroxy‐5‐nitrobenzyl)(2‐pyridyl)methylamine (H₂L2), and (3,5‐dichloro2‐hydroxybenzyl)(2‐hydroxy‐5‐nitrobenzyl)(2‐pyridyl)methylamine (H₂L3) the new isostructural dinuclear zinc compounds [Zn₂(L1)₂]·N(CH₂CH₃)₃ ( 1 ), [Zn₂(L2)₂]·2CH₃OH ( 2 ) and [Zn₂(L3)₂]·C₄H₁₀O ( 3 ) were synthesized. Due to their enzyme‐like trigonal bipyramidal N₂O₃ coordination environment of the zinc ions and the similar Zn···Zn distances the complexes can be considered to be structural models for the active sites in phospholipase C and nuclease P1. With H₂L3 also the dinuclear complex [Co₂(L2)₂(CH₃OH)]·2CH₃OH·0.5C₄H₁₀O ( 4 ) could be prepared. The new compounds were isolated and characterized by single crystal X‐ray crystallography as well as infrared spectroscopy. The cobalt compound 4 was additionally characterized by UV‐Vis spectroscopy and magnetic measurements. 1 crystallizes in the monoclinic space group P2₁/n with a = 11.2814(2), b = 28.6154(2), c = 13.1866(3) Å, β = 96.995(1)°, V = 4225.2(2) ų, Z = 4. 2 and 3 are monoclinic, space group C2/c with a = 23.084(5), b = 9.232(2), c = 21.849(4) Å, &β; = 96.83(3)°, V = 4623(2) ų, Z = 4, and a = 22.7834(3), b = 9.2463(1), c = 21.6351(3) Å, &β; = 97.592(1)°, V = 4517.7(2) ų, Z = 4, respectively. 4 crystallizes in the monoclinic space group I2/a with a = 22.4680(4), b = 20.5517(4), c = 22.8910(6) Å, &β; = 111.938(1)°, V = 9804.7(4) ų, Z = 8. 4 shows an effective magnetic moment of 6.72 μ_B at 300 K which clearly indicates the presence of two cobalt(II) high spin ions with Curie‐Weiss behaviour above 80 K. At lower temperatures a decrease of the effective magnetic moment was observed.     

Leurosine me­thio­dide–methanol–water (1/3/2)

The crystal structure of a methanol–water solvate ofleurosine me­thio­dide, (leurosine‐CH₃)⁺I^?·3CH₃OH·2H₂O (C₄₇H₅₉IN₄O₉·3CH₃OH·2H₂O), is described. The piperidine ring of the upper part of the mol­ecule adopts a sofa conformation. An intramolecular hydrogen bond between the tertiary N and the hydroxyl group of the vindoline moiety of the mol­ecule is present.     

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 BF ₂ ⁺ -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.     

Effect of organic bicarboxylates on the structures of cobalt(II) coordination polymers derived from a semi-rigid bis(benzimidazole) derivative

Two new Co(II) coordination polymers, [Co(L)(glu)] (1) and [Co(L)(npht)]·H₂O (2) (H₂glu = glutaric acid, H₂npht = 3-nitrophthalic acid, L = 1,4-bis(5,6-dimethylbenzimidazol-1-ylmethyl)benzene), have been hydrothermally synthesized by self-assembly of cobalt chloride with a semi-rigid bis(benzimidazole) derivative and different organic bicarboxylic acids. Single crystal X-ray diffraction analysis reveals that complex 1 is a one-dimensional tube-like coordination polymer containing one helical [Co-L] and two linear [Co-glu] chains. In complex 2, two npht ligands connect two Co(II) atoms to form a binuclear [Co(npht)]₂ subunit, which is further linked by L ligands with two kinds of conformations to form a 3-D CdSO₄-like framework. In addition, the electrochemical behaviors of the title complexes in bulk-modified carbon paste electrodes, and their thermal stabilities and fluorescent properties were investigated in this paper.     

Three multinuclear Co(II), Zn(II) and Cd(II) complexes based on a single-armed salamo-type bisoxime: syntheses,structural characterizations and fluorescent properties

Three multinuclear complexes, [Co(L)(OAc)Co(CH₃CH₂OH)₂]·H₂O, [Zn(L)(OAc)Zn(CH₃OH)], and [{Cd(L)(OAc)Cd(CH₃OH)}₂], containing a single-armed salamo-type bisoxime H₃L have been synthesized and characterized structurally. The Co(II) complex forms a dimeric unit by intermolecular hydrogen bond interactions of neighboring dimeric molecules. The Zn(II) complex also forms a dimeric unit by intermolecular hydrogen bond interactions. Interesting features of the crystal structure include O?O short contacts. Meanwhile, self-assembling infinite 1-D, 2-D, and 3-D supramolecular structures are formed by intermolecular hydrogen bond and C–H?π interactions. The Cd(II) complex forms an infinite 2-D supramolecular structure by intermolecular hydrogen bond interactions. The photophysical properties of the Co(II), Zn(II), and Cd(II) complexes have also been discussed.     

Zinc(II) Complex with 1,2-Bis(2-Pyridyl-1,2,4-Triazol-3-yl)ethane and Dianions of 1-Hydroxyethane-1,1-Diphosphonic Acid

Russian Journal of Coordination Chemistry - The reaction of ZnSO4·7Н2О with 1,2-bis(2-pyridyl-1,2,4-triazol-3-yl)ethane (Н2L) and 1?hydroxyethane-1,1-diphosphonic acid...     

Effect of the nature of the anion on the composition and structure of cobalt complex with monoethanolamine

A number of products formed in reactions of cobalt(II) salts with monoethanolamine (HEtm) in a neutral medium were synthesized and studied. X-Ray diffraction study showed that the nitrate and acetate form the dimers [Co(HEtm)₃][Co(Etm)₃](NO₃)₃ and [Co(HEtm)₃][Co(Etm)₃](CH₃COO)₃ · 8H₂O, respectively. In chloride solutions, cobalt is partially oxidized to give the trinuclear complex [Co^II{Co^III(Etm)₃}₂]Cl₃ · H₂Etm · 2H₂O. The reaction of the chelate [Co(Etm)₃] · 3H₂O with nitric acid is accompanied by complete protonation of the coordinated aminoethanolate ions, and the reaction with formic acid involves complete replacement of the coordinated ligand by acid residue anions and water molecules to give the coordination polymer {Co₂(μ-HCOO)₄(H₂O)₄} _n .     

Synthesis, Characterization, DNA-binding Properties and DNA Cleavage of a New Ternary Copper(Ⅱ) Complex with Mixed-ligands of Tridentate Schiff Base and 1,10-Phenanthroline

A new copper(II) complex, [Cu(naph‐leu)phen]CH₃OH·0.5H₂O, in which naph‐leu is the tridentate Schiff base ligand derived from the condensation of 2‐hydroxy‐1‐naphthaldehyde and L‐leucine, phen is phenanthroline, has been synthesized and characterized by elemental analyses, IR spectra and single crystal X‐ray diffraction. The DNA‐binding properties of this complex have been investigated by absorption spectra, fluorescence spectra and circular dichroism (CD) spectra, as well as viscosity measurement. Results show that this copper(II) complex binds to calf thymus DNA (CT‐DNA) in an intercalative mode and its intrinsic binding constant K_b is 4.87×10³ L·mol^?1. Furthermore, the DNA cleavage activity of this copper(II) complex has also been investigated by submarine gel electrophoresis. Interestingly, it was found that this complex can cleave the supercoiled plasmid pBR322 DNA to both nicked and linear forms.     

Synthesis,spectroscopic, thermal,free radical scavenging ability,and antitumor activity studies of cobalt(II) metformin complex

New [Co(Mfn-HCl)₂(NO₃)₂] · 6H₂O complex has been synthesized and characterized using microanalytical, molar conductance, spectroscopic (IR and UV-Vis), effective magnetic moment, and thermal analyses. The infrared spectroscopic results data received from the comparison between free Mfn · HCl ligand and its cobalt(II) complex proved that Metformin forms complex with cobalt(II) ions as a bidentate ligand through its two imino groups. The antioxidant activity of the Mfn · HCl and Co(II)-2Mfn · HCl complex were evaluated by using 1,1-diphenyl-2-picryl-hydrazyl (DPPH) radical scavenging method. Antitumor activity for Mfn · HCl ligand and its cobalt(II) complex was determined using Ehrlich Ascites carcinoma cell (EACC) line. It has been shown that the Co(II)-Mfn · HCl complex is much more effective as free radical scavenger and has higher antitumor activity than the free Mfn · HCl ligand.     

Supramolecular Hydrogen‐Bonded Frameworks from a New Bisphosphonic Acid and Transition Metal Ions

The reaction of 2‐morpholinoethylimino‐bis(methylenephosphonic acid) (H₄L) with cobalt(II), nickel(II) acetate, and cadmium(II) chloride in ethanol/water mixed solvents afforded three new crystal‐engineered supramolecular metal phosphonates, Co(H₃L)₂ · 2H₂O ( 1 ), Ni(H₃L)₂ · 2H₂O ( 2 ), and [Cd₂Cl₄(H₂O)₆]_0.5[H₄L] ( 3 ) by using a layering technique. The cobalt(II) ions in complex 1 are hexacoordinated by four phosphonate oxygen atoms and two imino nitrogen atoms. The mononuclear units of complex 1 are connected through hydrogen bonds to form a three dimensional supramolecular network. The structure of compound 2 is analogous to that of 1 except that the cobalt(II) ion in compound 1 is replaced by nickel(II) in compound 2 . In the molecular structure of compound 3 , cadmium is coordinated to three chloride ions and three aqua oxygen atoms to form a novel neutral dinuclear complex. Several hydrogen bonds connect the dinuclear complex and the neutral form of the ligand to build a supramolecular three dimensional structure.     

Synthesis,Crystal Structures and Properties of Two Novel Co（Ⅱ） and Cd（Ⅱ） Complexes of N-AcetyI-L-glutamic Acid and Imidazole Ligands

Two novel complexes {[Co（A-glu）（Im）2]·0.5H2O}n （1） and [Cd（A-glu）（Im）3]n （2） （H2A-glu=N-acetyl-L-glutamic acid, Im=imidazole） have been synthesized from the reaction of H2A-glu with Co（CH3COO）2·4H2O or Cd（CH3COO）2·2H2O in the presence of Im. Both of the complexes display different coordination environment and similar one-dimensional chain structure. The magnetic susceptibility measurements for 1 show a weak antiferromagnetic interaction between two cobalt（Ⅱ） ions bridged by A-glu ligand. The complex 2 exhibits an intense fluorescent emission in solid state at room temperature.