Tetragonal distortions and vibronic coupling in hexaflouro nickel(II) and copper (II) complexes

Two parameters, axial (R_a) and equatorial (R_e) metal-ligand distances, describe the tetragonal distortions of the NiF^4?₆ and CuF^4?₆ complexes under study. The experimental values of R_a plotted vs R_e exhibit a smooth curve type dependence valid for MF₆ chromophore of solid state compounds. In the model study it becomes explained by analyzing the shape of the adiabatic potential surface (APS) of the form of E_T(R_a, R_e). Around the energy minima the map of numerical values (obtained by the quantum-chemical CNDOUHF and INDOUHF methods) was transformed to an analytic form from which the quantitative characteristics of APS were obtained in a new, simple way. The set of equatorial-axial parameters as well as the set of vibronic parameters were evaluated and discussed in more detail.     

Stability constants of oxalate complexes of copper (II) and nickel (II) by paper electrophoresis

Summary Stability constants of copper (II) and nickel (II) oxalates have been determined by paper electrophoresis. Oxalic acid (0.005 mol dm⁻³) was added to the background electrolyte: 0.1 mol dm⁻³ HClO₄. The proportions of HC₂O ₄ ⁻ and C₂O ₄ ²⁻ were varied by changing the pH of the electrolyte, these anions yielding the complex ions MHC₂O ₄ ⁺ and M(C₂O₄) ₂ ²⁻ , average values of the stability constants for which are 10^2.4 and 10^7.6 respectively for Cu(II), and 10^2.3 and 10^6.5 for Ni(II) (μ=0.1,30°).     

Acid equilibria of methylthymol blue and formation constants of cobalt(II), nickel(II), copper(II) and zinc(II) complexes with methylthymol blue

Potentiometric and spectrophotometric studies on acid equilibria and reactions with Co(II), Ni(II), Cu(II) and Zn(II) for Methylthymol Blue (MTB) are described. The equilibrium constants have been calculated. MTB has been found to form 1:1 and 2:1 (mole ratio of metal to ligand) complexes, including protonated ones. The probable configuration of the complexes and the effects on the stabilities have been discussed.     

Acid equilibria of semi-methylthymol blue and formation constants of cobalt(II), nickel(II), copper(II) and zinc(II) complexes with semi-methylthymol blue

Potentiometric and spectrophotometric studies on Semi-Methylthymol Blue (SMTB or H(4)L) have been performed. The acid-base and Co(II), Ni(II), Cu(II) and Zn(II)-ligand reaction stoichiometries were determined, and the formation constants of the corresponding proton and metal complexes, and the molar absorptivities were calculated. Evidence was found for the formation of 1:1 Co(II), Ni(II) and Cu(II) complexes, and 1:1 and 1:2 Zn(II) complexes. Cu(II) formed the hydroxo-complex, Cu(OH)L(3-), but no hydroxo-complexes of the other metal ions were observed. Suggestions are made concerning the probable structure of the complexes.     

Apparent formation constants of dithiooxamide and substituted dithiooxamide complexes of cobalt(II,III), nickel(II) and copper(II) in strongly acidic media

The apparent stability constants of the complex species formed between cobalt(II, III), nickel(II) or copper(II) and dithiooxamide or some N,N′- and tetra-substituted dithiooxamides have been determined in strongly acidic media at 25 ° C. The configuration of the complexes in solution is discussed on the basis of the electronic spectra.     

Jahn—teller distortions in copper(II) complexes as determined from ESR powder spectra

Cations Cu(ligand)²⁺₆ doped in lattices of non-cubic Zn(ligand)₆(anion)₂ are shown to have ESR powder spectra, corresponding with two types of cations, distorted octahedral and regular octahedral. Upon lowering of the temperature the number of distorted molecules increases. Despite of the non-cubic symmetry the results are essentially similar to single crystal observations and investigations on cubic lattices.     

Calculations of microconstants and equilibrium formation constants for platinum(II) and palladium(II) halide complexes in solution

Distribution diagrams and formation functions for halide complexes [M(H₂O)_{4 ? n} Cl _n ]^{2 ? n} (M = Pt(II) or Pd(II)) and [PdCl_{4 ? n} Br _n ]^2? (n = 0?C4) in solution are analyzed in terms of the matrix model. Equilibrium constants for binding the first ligand $\left( {\bar K} \right)$ and corrections for the mutual influence between ligands (??) in the course of complex formation in solution are calculated. In examples analyzed, the substitution of chloride ion for water in the coordination sphere of platinum(II) and palladium(II) is an anti-cooperative process. The substitution of bromide ion for chloride ion in the coordination sphere of [PdCl₄]^2? is weakly cooperative. Quantum-chemical calculations show that platinum(II) and palladium(II) cis-bisaquadichloro complexes in the gas phase are thermodynamically less stable than trans-isomers. The cis-trans isomerization constants in the gas phase calculated by the DFT method and those found for solutions using the matrix model have the same order of magnitude.     

A urea adduct of bis(hinokitiolato)copper(II)

Bis(μ₂‐3‐isopropyl‐7‐oxocyclohepta‐1,3,5‐trien‐1‐olato)bis[(3‐isopropyl‐7‐oxocyclohepta‐1,3,5‐trien‐1‐olato)copper(II)]–urea–acetone (1/6/2), [Cu₂(C₁₀H₁₁O₂)₄]·6CH₄N₂O·2C₃H₆O, where 3‐isopropyl‐7‐oxocyclohepta‐1,3,5‐trien‐1‐olate is the systematic name for the hinokitiolate anion, contains three novel structural features. First, it contains a bis(hinokitiolato)copper(II) dimer, [Cu(hino)₂]₂, unlike any other, demonstrating that linkage isomerism is another avenue by which Cu(hino)₂ can transmute from one form to another. Second, [Cu(hino)₂]₂ is hydrogen bonded to two urea molecules, indicating that hydrogen bonding cannot yet be discounted from any proposed mechanism of action for the antimicrobial and antiviral properties of bis(hinokitiolato)copper(II). Finally, corrugated urea layers crosslinked by [Cu(hino)₂]₂ dimers are observed, suggesting that a new family of host–guest materials, i.e. metallo–urea clathrates, exists to challenge our understanding of crystal engineering and crystal growth and design. Selected details of the structure are that the [Cu(hino)₂]₂ dimers possess crystallographic inversion symmetry, the Cu atoms have square‐pyramidal coordination geometries, the basal Cu—O bonds are in the range 1.916 (2)–1.931 (2) Å, the apical Cu—O bond length is 2.582 (2) Å, the hinokitiolate bite angles are in the range 83.41 (7)–83.96 (8)°, the urea–Cu(hino)₂ interactions have an R₂²(8) motif, and the urea layers result from the close packing of R₈⁶(28) `butterflies' and R<sub>8</sub><sup>6</sup>(24) `strips of tape'.     

Electronic and structural variation among copper(II) complexes with substituted phenanthrolines

A series of copper(II) complexes with substituted phenanthroline ligands has been synthesized and characterized electronically and structurally. The compounds that have been prepared include the monosubstituted ligand complexes of the general formula [Cu(5-R-phen)(2)(CH(3)CN)](BF(4))(2), where R = NO(2), Cl, H, or Me, and the disubstituted ligand complex [Cu(5,6-Me(2)-phen)(2)(CH(3)CN)](BF(4))(2). The complexes [Cu(5-NO(2)-phen)(2)(CH(3)CN](BF(4))(2) (1), [Cu(5-Cl-phen)(2)(CH(3)CN)](BF(4))(2) (2), [Cu(o-phen)(2)(CH(3)CN)](BF(4))(2) (3), and [Cu(5-Me-phen)(2)(CH(3)CN)](BF(4))(2) (4) each crystallize in the space group C2/c with compounds 1, 2, and 4 comprising an isomorphous set. The disubstituted complex [Cu(5,6-Me(2)-phen)(2)(CH(3)CN)](BF(4))(2) (5) crystallizes in the space group P2(1)/c. Each structure is characterized by a distorted trigonal bipyramidal arrangement of ligands around the central copper atom with approximate or exact C(2) symmetry. The progression from electron-withdrawing to electron-donating substituents on the phenanthroline ligands correlates with less accessible reduction potentials for the bis-chelate complexes.     

Potentiometric determination of stability constants of inorganic cyclophosphate complexes with copper(II), cadmium(II) and lead(II) ions

The stability constants of the complexes of cyclophosphate anions and copper(II), cadmium(II) and lead(II) ions were determined by potentiometry with the use of ion-selective electrodes. For each metal ion, the stability constant of the 1:1 complex increases linearly with the charge on the phosphate ion. For the same cyclophosphate ion, the stability constants also increase with increase in the crystal radii of the cation, i.e. in the order: Cu²⁺ < Cd²⁺ < Pb²⁺. These results suggest that the complex formed is a typical outer-sphere type based on electrostatic forces.     

Temperature dependences of the formation constants of the cobalt(II) acetate complexes

The formation constant for the 1:1 complex between Co(II) and acetate ions (CoAc⁺) has been determined over the temperature range 25–75°C, both by spectrophotometry and by potentiometric titration. At an ionic strength of 1.0 M a near zero enthalpy of formation ws found.A spectrophotometer cell suitable for use up to ∼250°C is described and spectra of Co(II) acetate solutions are presented at temperatures up to 200°C. At elevated temperatures a tetrahedral species having the composition CoAc₂ is formed. The role of the complexation of Co(II) by acetate in the precipitation of Co₃O₄ from solutions of Co(II) acetate is briefly discussed.     

Ether formation on the tridentate Schiff base ligands of copper(II) complexes

A series of copper(II) complexes, CuL·imidazole, where L^2? are tridentate Schiff base ligands formed by condensation of salicylaldehyde with a series of amino acids, have been synthesized. Visible spectral data indicate that copper(II) in these complexes are five coordinate in the solid state and in solution. Electrospray mass spectrometry has been used to show how these complexes react in alcohol/NaOH solutions with and without the presence of d-galactose. In the absence of d-galactose where the amino acid in the ligand is serine, the alcohol group on the ligand is converted to its alkyl ether after sonication of the solution for up to 4?h. In the presence of d-galactose, an alkoxy group is added to the ligands except for the ligand containing serine after sonication of the solutions for up to 4?h. At the same time, d-galactose is oxidized to its aldehyde. Where the ligand contains methionine, oxygen is also added to the ligand, most likely to the thioether sulfur.     

A small methanoato ligand in the structural differentiation of copper(II) complexes

Several copper(II) methanoato complexes, namely mononuclear [Cu(O₂CH)₂(2-mpy)₂] (1) (2-mpy = 2-methylpyridine), binuclear [Cu₂(μ-O₂CH)₄(2-mpy)₂] (2), and the polynuclear {[Cu(μ-O₂CH)₂(2-mpy)₂][Cu₂(μ-O₂CH)₄]}_n (3) and {Na₂[Cu(μ-O₂CH)₂(O₂CH)₂][Cu₂(μ-O₂CH)₄]}_n (4), have been synthesized. The mononuclear complex 1 is formed by two asymmetric chelate methanoate anions and two 2-methylpyridine molecules, giving a highly distorted ‘elongated octahedral’ coordination sphere. Complex 1 decomposes outside the mother-liquid, transforming into a regular isolated binuclear paddle-wheel complex 2 with four intra-binuclear bridging methanoates and two axial 2-mpy ligands. The polynuclear complex 3 is formed of alternate mononuclear and binuclear building blocks resembling the central cores of 1 and 2, but with significant differences, especially for the methanoates of the mononuclear units. The oxygen atom of the mononuclear unit in the octahedral axial position in 3 is simultaneously coordinated to the axial position of the binuclear paddle-wheel central core, thus enabling a chain type of structure. A chain of alternate mononuclear and binuclear building blocks, as in the neutral compound 3, are found as well in the ionic polymeric compound 4, though two types of bridges are found in 4, while there is only one type in 3. Namely, the axial position of the octahedral mononuclear unit in 4 is occupied by the methanoate oxygen atom that is already a part of the binuclear paddle-wheel unit, while one equatorial methanoate from the mononuclear unit serves as a triatomic bridge to the axial position of the binuclear building block. A very strong antiferromagnetic interaction is found for all the complexes with the paddle-wheel building blocks [Cu₂(μ-O₂CH)₄] 2–4 (−2J = 444–482 cm⁻¹), attributed to the methanoate intra-binuclear bridges. On the other hand, this strong antiferromagnetism, found already at room temperature, reduces the intensity of the EPR S = 1 spin signals reported for the isolated paddle-wheel complex 2. For the polymeric 3, only the spin S = ½ signals are found in the EPR spectra, and they are assigned to the mononuclear building blocks. No signals with a clear origin are however seen in the room temperature EPR spectrum of the polymeric analogue 4, only the S = ½ signals in the low temperature spectra. This feature is suggested to be due to a specific influence between the adjacent S = 1 (binuclear) and S = ½ (mononuclear) species via their bridges.     

Equilibrium studies on Schiff base complexes of copper(II) and nickel(II): Ligand substitution and formation of mixed ligand complexes

Summary Vis spectrophotometry has been used to study various ligand substitution equilibria (1) and (2) involving four-coordinate copper(II) and nickel(II) his chelate complexes in methanol, propan-2-ol and toluene. MA₂ + HB MAB+HA, K₁ (1) MAB + HB MB₂ + HA, K₂ (2) The Schiff base ligands, HA and HB, which are monobasic and bidentate, represent salicylaldimine type N,O-ligands ( HSA=NR) (1) or pyrrole-2-aldimine type N,N-ligands ( HPA=NR) (2) with different branching at the - or (3-carbon of the organic group R. For both types of ligand the relative thermodynamic stability of their copper and nickel complexes is governed mainly by the steric demands of R, which determine the degree of tetrahedral distortion. The order of stability as given by = K₁ K₂ is: t-Bu < neo-Pent < i-Pr < i-Bu < Et < n-Pr. The K₁/K₂ ratio is strongly solvent dependent in the sense that the mixed ligand species MAB is stabilised in toluene relative to methanol. Such a solvent effect is not observed for . The MAB complexes could not be isolated. The vis spectrum of the mixed ligand species Ni(SA=NiPr, SA=NEt) was calculated by computer fitting of the experimental data.     

Preparation,structural and thermal characterization of cobalt(II) and copper(II) complexes with 3-hydroxypicolinamide

Cobalt(II) and copper(II) complexes of 3-hydroxypicolinamide (3-OHpia), namely [Co(3-OHpia)₂(H₂O)₂](NO₃)₂ (1), [Co(3-Opia)₂(H₂O)₂] (2) and [Cu(3-OHpia)₂(NO₃)₂] (3), were prepared and characterized by IR spectroscopy and TG/DTA methods. The molecular and crystal structures of 1 and 3 were determined by X-ray crystal structure analysis. Complexes 1 and 3 were obtained by reaction of 3-hydroxypicolinamide with cobalt(II) nitrate or copper(II) nitrate, respectively, in a mixture of ethanol and water. Complex 2 was prepared by reaction of cobalt(II) acetate and 3-OHpia in aqueous solution. X-ray structural analysis revealed octahedral coordination polyhedra in both 1 and 3 and the same N,O-chelated coordination mode of 3-OHpia. The coordination sphere of the cobalt(II) center in 1 is completed by two coordinated water ligands and that of the copper(II) center in 3 by two coordinated nitrate anions. There are also two uncoordinated nitrate ions in 1 which compensate the positive charge of cobalt(II). The crystal structures of 1 and 3 are dominated by intermolecular O–H···O and N–H···O hydrogen bonds. The thermogravimetric study indicated the loss of two coordinated water molecules in 1 and 2 and of one 3-OHpia ligand together with N₂ molecule in 3 at lower temperatures (up to 300 °C).     

Thermal and structural characterization of copper(II) complexes with phenyl-2-pyridylketoxime (HPPK)

Journal of Thermal Analysis and Calorimetry - Copper(II) complexes of different nuclearity with phenyl-2-pyridylketoxime (HPPK), such as mononuclear [Cu(HPPK)(PPK)X], whereby...     

Inorganic-metalorganic hybrids based on copper(II)-monosubstituted Keggin polyanions and dinuclear copper(II)-oxalate complexes. Synthesis, X-ray structural characterization, and magnetic properties

Reaction of in situ generated copper(II)-monosubstituted Keggin polyoxometalates and copper(II)-bipyridine-oxalate complexes in the corresponding alkaline acetate buffer led to the formation of hybrid metal organic-inorganic compounds K(2)[{SiW(11)O(39)Cu(H(2)O)}{Cu(2)(bpy)(2)(H(2)O)(2)(mu-ox)}(2)].14H(2)O (1), K(14)[{SiW(11)O(39)Cu(H(2)O)}{Cu(2)(bpy)(2)(mu-ox)}](2)[SiW(11)O(39)Cu(H(2)O)].55H(2)O (2), (NH(4))(4)[{SiW(11)O(39)Cu(H(2)O)}{Cu(2)(bpy)(2)(mu-ox)}].10H(2)O (3), and Rb(4)[{SiW(11)O(39)Cu(H(2)O)}{Cu(2)(bpy)(2)(mu-ox)}].10H(2)O (4). Their structures have been established by single-crystal X-ray diffraction. The main structural feature of these compounds is the presence of copper(II)-monosubstituted alpha-Keggin polyoxoanions as inorganic building blocks, on which the mu-oxalatodicopper metalorganic blocks are supported. Compound 1contains the discrete hybrid polyanion [{SiW(11)O(39)Cu(H(2)O)}{Cu(2)(bpy)(2)(H(2)O)(2)(mu-ox)}(2)](2)(-), whereas the polymeric hybrid polyanion [{SiW(11)O(39)Cu(H(2)O)}{Cu(2)(bpy)(2)(mu-ox)}(2)](n)(4)(n)(-) gives a monodimensional character to compounds 2-4. Magnetic and EPR results are discussed with respect to the crystal structure of the compounds. DFT calculations on both the [Cu(2)(bpy)(2)(H(2)O)(4)(mu-ox)](2+) cationic complex and the metalorganic blocks have been performed in order to determine the optimized geometry and the magnetic coupling constants, respectively.     

Composition and stability constants of copper(II) complexes with succinic acid determined by capillary electrophoresis

The advantage of capillary electrophoresis was demonstrated for studying a complicated system owing to the dependence of direction and velocity of the electrophoretic movement on the charge of complex species. The stability constants of copper(II) complexes with ions of succinic acid were determined by capillary electrophoresis, including the 1?:?2 metal to ligand complexes which are rarely mentioned. The measurements were carried out at 25 °C and ionic strength of 0.1, obtained by mixing the solutions of succinic acid and lithium hydroxide up to pH 4.2–6.2. It was shown that while pH was more than 4.5 the zone of copper(II) complexes with succinate moves as an anion. It is impossible to treat this fact using only the complexes with a metal-ligand ratio of 1?:?1 (CuL⁰, CuHL⁺). The following values of stability constants were obtained: log β(CuL) = 2.89 ± 0.02, log β(CuHL⁺) = 5.4 ± 0.5, log β(CuL₂^2?) = 3.88 ± 0.05, log β(CuHL₂^?) = 7.2 ± 0.3.     

Influence of heterocycles arrangement in structural isomeric ligands on coordination sphere of copper(II) complexes: Crystal structures and spectroscopic characterization

New copper complexes with two structural isomeric ligands, 2-(indazol-1-yl)-2-thiazoline (TnInA) and 2-(indazol-2-yl)-2-thiazoline (TnInL), have been synthesized and characterized by magnetic measurements, IR, electronic and EPR spectroscopies. Moreover, the molecular structures of [Cu(NO₃)(TnInA)₂(H₂O)](NO₃) · (H₂O) (1) and [Cu(NO₃)₂(TnInL)(H₂O)] (2) have been resolved by single-crystal X-ray diffraction studies. In compound 1 the copper ion is in a distorted octahedral geometry, with the equatorial plane formed by four nitrogen donor atoms from two organic ligands and the axial positions occupied by two oxygen atoms from a water molecule and a mono-coordinated nitrate anion. The coordination geometry around the copper atom in compound 2 can be described basically as a square pyramid with two nitrogen atoms from TnInL ligand, one oxygen atom from a water molecule and one oxygen atom from a nitrate group in the equatorial plane. The axial position is occupied by one oxygen atom from a nitrate group. Likewise, a second oxygen atom from the last nitrate group in equatorial position might involve in a weak sixth coordination position to give a (4 + 1 + 1^∗) coordination mode.