Interactions of hexamethyltetrabutyl-substituted biladiene-a,c with cobalt(II) and zinc(II) acetates

The thermodynamics of the reaction of 1,3,7,13,17,19-hexamethyl-2,8,12,18-tetrabutylbiladiene-a,c (H₂L) with cobalt(II) and zinc(II) acetates in dimethylformamide (298.15 K) was studied by spectrophotometric and calorimetric titration. It was found that H2L and Zn(II) form a mononuclear complex ZnL, and in the case of Co(II), a binuclear biligand complex Co₂L₂ is formed. Thermodynamic characteristics of the formation of Co(II) and Zn(II) complexes with biladiene-a,c in DMF at 298.15 K were determined.     

Formation of Mixed-Ligand Complexes of Metals(II) with Monoamine Complexones and Amino Acids in Solution

The formation of mixed-ligand complexes in the M(II)–Nta, Ida–L (M = Cu(II), Ni, Zn, Co(II), L = Ser, Thr, Asp, Arg, Asn) systems, where Ida and Nta are the residues of iminodiacetic and nitrilotriacetic acids, respectively, is studied using pH measurements, calorimetry and spectrophotometry. The thermodynamic parameters (logK, Δ_rG⁰, Δ_rH, Δ_rS) of their formation at 298.15 K and ionic strength I = 0.5 (KNO₃) are determined. The most likely scenario of amino acid residue coordination in the composition of mixed complexes is discussed.     

Mixed-Ligand Complexation of Zinc and Cobalt(II) Complexonates with Amino Acids in an Aqueous Solution

The formation of mixed-ligand complexes in the M(II)–Nta and Ida–L systems (M = Co, Zn; L = His, Orn, Lys, Gly, Im, en), where Ida and Nta are the residues of iminodiacetic and nitrilotriacetic acids, was studied by pH-metry, calorimetry, and NMR spectroscopy. The thermodynamic parameters (logK, Δ _r G⁰, Δ _r H, Δ _r S) of formation for these complexes were determined at 298.15 K and an ionic strength I = 0.5 (KNO3). The most probable pattern of coordination between a complexone and an amino acid in mixed-ligand complexes was revealed.     

Varieties in structures of Co(II), Ni(II) and Cu(II) coordination compounds based on dimethyl pyridin-2-ylcarbamoylphosphoramidate

A series of new 3d metal complexes based on dimethyl pyridin-2-ylcarbamoylphosphoramidate (HL) was synthesized. The compounds with general formula M(HL)₂Cl₂·nH₂O and M(L)₂·nH₂O (M=Co²⁺, Cu²⁺, Ni²⁺) were characterized by means of single-crystal X-ray analysis and IR spectroscopy. The organic ligands in all complexes are coordinated via oxygen atom of the carbonyl group and nitrogen atom of the heterocycle. The coordination environment of the central atoms is a distorted octahedron. The axial positions in the Co(II) and Ni(II) complexes with deprotonated ligands are occupied by water molecules. The Co(II) and Cu(II) complexes with phosphoryl ligands in a neutral form have different ligands in the axial positions: in the Co(II) complex, the positions are occupied by two water molecules, whereas in the Cu(II) complex, the positions are occupied by two chlorine anions. The structure of HL was experimentally and theoretically obtained by utilizing single-crystal X-ray analysis and DFT calculations. The computationally optimized geometric parameters for HL show a good agreement with the experimental results.     

Complexation between decamethyl-3,3′-bis(dipyrrolylmethene) and zinc(II), copper(II), and cobalt(II) acetates

Decamethyl-3,3′-bis(dipyrrolylmethene) dihydrobromide H₂L · 2HBr (H₂L is bis(3,4,7,8,9-pentamethylpyrrol-3-yl)methane), which is the simplest representative of a novel class of oligo(dipyrrolylmethenes) belonging to chromophore chelating nonmacrocyclic ligands, were examined by ¹H NMR, IR, and electronic absorption spectroscopy. Complexation reactions of H₂L · 2HBr with M(AcO)₂ (M = Zn(II), Cu(II), and Co(II)) in DMF at 298.15 K were monitored by electronic absorption spectroscopy and studied by the molar ratio method. The thermodynamic constants K ⁰ of these reactions were estimated. The d metal ions coordinate H₂L to give the binuclear homoleptic complexes [M₂L₂]. The reactions proceed through the intermediate binuclear heteroleptic complex [M₂L(AcO)₂] detected by spectroscopic methods. The thermodynamic stabilities of [M₂L₂] and [M₂L(AcO)₂] increase when moving from Cu(II) to Zn(II) and Co(II). The probability of formation and stability of [M₂L₂] containing 3,3′-bis(dipyrrolylmethene) are substantially higher than those of analogous complexes with the 2,2′-isomer (decamethyl-2,2′-biladienea, c). The low K ⁰ values for the complexation between H₂L and Cu(AcO)₂ are due to slow oxidation of the biladiene ligand into a bilatriene with participation of Cu²⁺ ions.     

Synthesis and crystal and molecular structure of the [Co(HL)Cl<Subscript>2</Subscript>] complex (H<Subscript>2</Subscript>L is an optically active terpene bis-pinane propylenediaminodioxime)

Interaction of Co(II) chloride with optically active bis-pinane propylenediaminodioxime (H₂L) gave a diamagnetic compound of Co(III) with a composition [Co(HL)Cl₂]. The crystal and molecular structure of the compound was determined by X-ray diffraction (XRD) analysis (Enraf-Nonius CAD-4 diffractometer, λMoK_α, 703 F _hkl , R = 0.0347). The crystals are orthorhombic with unit cell parameters a = 8.989(1) Å, b = 12.351(2) Å, c = 22.425(3) Å, V = 2487.7(6) ų, Z = 4, ρ_calc = 1.420 g/cm³, space group P2₁2₁2₁. The crystal structure of the complex is composed of discrete one-center molecules. In the complex, the Co³⁺ ion coordinates four N atoms of the tetradentate cycle-forming ligand (HL^? anion) and two Cl atoms. The coordination polyhedron of Co is a distorted octahedron Cl₂N₄.     

Studies on Mononuclear Chelates Derived from Substituted Schiff Base Ligands: Synthesis and Characterization of a New 5-Methoxysalicyliden-<Emphasis Type="Italic">p</Emphasis>-Aminoacetophenoneoxime and Its Complexes with Co(II), Ni(II), Cu(II), and Zn(II)

New complexes of Co(II), Ni(II), Cu(II), and Zn(II) with new Schiff bases derived by the condensation of p-aminoacetophenoneoxime with 5-methoxysalicylaldehyde are synthesized. The compounds are characterized by elemental analyses, magnetic susceptibility measurements, IR, ¹H and ¹³C NMR spectra, electronic spectral data, and molar conductivity. The thermal stabilities of the compounds are also reported. The Schiff base acts as bidentate O,N-donor atoms, and their metal complexes are supposed to possess a tetrahedral geometry with respect to the central metal ion. The general formula of the 5-methoxysalicyliden-p-aminoacetophenoneoxime Co(II), Ni(II), Cu(II), and Zn(II) complexes is Co(L)₂, Ni(L)₂, Cu(L)₂, and Zn(L)₂.     

Malonatobenzhydrazidediaquacobalt(II) hydrate: Synthesis,crystal and molecular structures

The coordination compound [Co(L)(Mal)(H₂O)₂]H₂O (I) (L is benzhydrazide, H₂Mal is malonic acid) has been synthesized and studied by IR spectroscopy, thermogravimetry, and X-ray diffraction. Crystals are triclinic, a = 7.610(4) Å, b = 7.854(2) Å, c = 12.751(2) Å, α = 75.12(3)°, β = 88.01(3)°, γ = 80.26(3)°, Z = 2, space group \(P\bar 1\). The structure is molecular. The Co²⁺ atom has a distorted octahedral coordination. The Co-O and Co-N bond lengths are 2.031-2.129(4) and 2.157(5) Å, respectively. The endocyclic O1Co1N1 bond angles are 77.3(2)° and 90.0(2)° in the five- and six-membered chelate rings, respectively. Molecules of complex I are linked via a great number of hydrogen bonds. The C…C contacts between phenyl rings additionally strengthen the structure.     

Thermochemical study of the complex formation of copper(II) and nickel(II) iminodiacetates with amino acids in aqueous solutions

The formation of mixed-ligand complexes in the M(II)–Ida–L systems (M = Cu, Ni, L = His, Orn, Lys), where Ida is the iminodiacetic acid residue, was studied by pH-metry, calorimetry, and spectrophotometry. The thermodynamic parameters (logK, Δ_rG⁰, Δ_rH, Δ_rS) of formation of the complexes were determined at 298.15 K and the ionic strength I = 0.5 (KNO₃). The most probable mode of coordination of the chelating agent and the amino acid in the mixed-ligand complexes was elucidated.     

Synthesis,crystal structures,and characterization of a new substituted 1,2,4-triazole and its two Co(II)/Mn(II) complexes

A new triazole-substituted ligand H₂L (H₂Trza = 3-amino-1H-1,2,4-triazole-5-acetate) and its two new isomorphic compounds [M(HTrza)₂(_H2O)₂] ? 2H₂O (Co(I) and Mn(II)) have been synthesized and characterized structurally. Their X-ray crystal structures (CIF files CCDC nos. 906893 for I and 906892 for II) show that H₂L belongs to a tetragonal system; space group P4₃ with a = b = 5.0445(13), c = 27.054(10) Å; Z = 4. Complex I belongs to a monoclinic system; space group P2₁/n with a = 7.6543(8), b = 7.3453(8), c = 13.6283(14) Å; β = 91.5990(10)°, Z = 2. Complex II belongs to a triclinic system; space group with a = 6.8550(15), b = 8.0630(18), c = 15.173(4) Å; α = 84.794(4)°, β = 79.005(3)°, γ = 73.779(4)°, Z = 2. X-ray analysis demonstrates that compound H₂L is found to contain a H₂Trza and a lattic water molecule; complexes I and II are discrete mononuclear species. The central Co(II) and Mn(II) atoms exhibit octahedral coordinations, type 4 + 2. In two compounds, the coordination entities are further organized via hydrogenbonding interactions to generate uniform supramolecular networks. Thermal stabilities of two compounds were examined by thermogravimetric analysis.     

Supramolecular 2D structure of [Co(2-Me-Pyz)<Subscript>2</Subscript>(H<Subscript>2</Subscript>O)<Subscript>4</Subscript>](NO<Subscript>3</Subscript>)<Subscript>2</Subscript>

The complex [Co(2-Me-Pyz)₂(H₂O)₄](NO₃)₂ is synthesized and its structure is determined. The crystals are monoclinic: space group P2₁/n, a = 10.685(2) Å, b = 6.837(1), c = 12.515(3) Å, β = 91.84(3)°, V = 913.8(3) ų, ρ_calcd = 1.042 g/cm ³, Z = 2. The Co²⁺ ion (in the inversion center) is coordinated at the vertices of the distorted octahedron by two nitrogen atoms of methylpyrazine and four oxygen atoms of the water molecules (Co(1)–N(1) 2.180(3), average Co(1)–O(w) 2.079(3) Å, angles at the Co atom 87.9(1)–92.1(1)°). Supramolecular pseudometallocycles are formed in the structure through the O(w)–H…N(1) hydrogen bonds between the coordinated H₂O molecules and the terminal nitrogen atoms of the 2-methylpyrazine molecules. Their interaction results in the formation of supramolecular layers joined by the NO₃ groups into a three-dimensional framework.     

Synthesis,experimental and theoretical characterization,and antimicrobial studies of some Fe(II), Co(II), and Ni(II) complexes of 2-(4,6-dihydroxypyrimidin-2-ylamino)naphthalene-1,4-dione

The work reported the synthesis and characterisation of Fe²⁺, Co²⁺, and Ni²⁺ complexes of 2-(4,6-dihydroxypyrimidin-2-ylamino)naphthalene-1,4-dione (HL). The spectroscopic and elemental analysis results obtained were consistent with the adoption of the formulas, [ML₂] (M = Fe and Co) and [ML₂(H₂O)] (M = Ni) for the metal complexes. Electronic spectra and magnetic moments of the metal complexes corroborated octahedral geometry for Ni(II) complex and tetrahedral geometry for Fe(II) and Co(II) complexes. However, quantum-chemical calculations using density functional theory predicted trigonal bipyramidal geometry for Ni(II) complex and provided corroborative explanations for the structures of the other complexes. Conductance measurements in dimethylsulfoxide indicate that the complexes are non-electrolytes. The antimicrobial potential of the compounds was evaluated against Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, Bacillus cereus, Proteus mirabilis, Klebsiella oxytoca, Aspergillus niger, A. flavus, and Rhizopus stolonifer. The compounds gave moderate to good antimicrobial activity. However, the bacterial and fungal organisms were more susceptible to the cobalt complex and ligand respectively than the other compounds at concentration of 10 mg/mL. The compounds were also assessed for their antioxidant potential using 1, 1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging assay. The compounds displayed good DPPH radical scavenging activities. The nickel complex exhibited the best DPPH radical scavenging activity compared to the other compounds.     

Synthesis and crystal structures of cobalt(III) and zinc(II) complexes with Schiff bases

Two new cobalt(III) and zinc(II) complexes, [Co(L¹)₂ (H₂O)] · ClO₄ (I) and [Ni(L²)₂ (H₂O)₂] · 2ClO₄ (II), where L¹ is the deprotonated form of 5-methoxy-2-[(2-morpholin-4-ylethylimino)methyl]phenol, and L² is the zwitterionic form of 2-[(2-isopropylaminoethylimino)methyl]-5-methoxyphenol, were synthesized and structurally characterized by elemental analyses, IR spectra, and single-crystal X-ray diffraction. The crystal of I is monoclinic: space group P2₁/c, a = 11.1512(4), b = 28.2424(11), c = 10.9655(4) Å, β = 95.746(2)°, V = 3436.1(2) ų, Z = 4. The crystal of II is triclinic: space group P2₁/c, a = 8.1441(2), b = 10.4531(3), c = 10.8849(3) Å, α = 84.0240(10)°, β = 76.9800(10)°, γ = 74.2280(10)°, V = 867.92(4) ų, Z = 1. Complex I consists of a mononuclear cobalt(III) complex cation and a perchlorate anion. Complex II consists of a crystallographic centrosymmetric mononuclear nickel(II) complex cation and two perchlorate anions. Each metal atom in the complexes is in an octahedral coordination.     

Low-temperature heat capacity and high-temperature thermal behavior of sodium lutetium molybdate phosphate Na<Subscript>2</Subscript>Lu(MoO<Subscript>4</Subscript>)(PO<Subscript>4</Subscript>)

The low-temperature heat capacity of Na₂Lu (MoO₄)(PO₄) was measured by adiabatic calorimetry in the range of 7.47–345.74 K. The experimental data were used to calculate the thermodynamic functions of Na₂Lu (MoO₄)(PO₄). At 298.15 K, the following values were obtained: C _p ⁰ (298.15 K) = 237.7 ± 0.1 J/(K mol), S ⁰(298.15 K) = 278.1 ± 0.8 J/(K mol), H ⁰(298.15 K) ? H ⁰ (0 K) = 42330 ± 20 J/mol, and Φ⁰(298.15 K) = 136.1 ± 0. 3 J/(K mol). A heat capacity anomaly was found in the range of 10-67 K with a maximum at T _tr = 39.18 K. The entropy and enthalpy of transition are ΔS = 12.39 ± 0.75 J/(K mol) and ΔH = 403 ± 16 J/mol. The thermal investigation of sodium lutetium molybdate phosphate in the high-temperature range (623–1223 K) was performed using differential scanning calorimetry. It was found that during melting in the range of 1030–1200 K, Na₂Lu(MoO₄)(PO₄) degrades to simpler compounds; the degradation scenario is verified by X-ray powder diffraction.     

4,7,13,16,21,24-hexaoxa-1,10-diazoniabicyclo[8.8.8]-hexacosane tetrachloromanganese(II) and tetrachlorozinc(II) hydrates: Synthesis and crystal structures

Two complex salts, i.e., 4,7,13,16,21,24-hexaoxa-1,10-diazoniabicyclo[8.8.8]hexacosane tetrachloromanganese(II) and tetrachlorozinc(II) hydrates, [H₂(Crypt-222)][MnCl₄] · 1.5H₂O (I) and [H₂(Crypt-222)][ZnCl₄] · 2H₂O (II) were synthesized and their crystal structures were studied by X-ray diffraction. Crystals I and II are trigonal (space group R \(\bar 3\) c, Z = 12); I: a = 11.033, c = 77.775 Å; II: a = 11.046, c = 77.555 Å (the structures were solved by the direct method and refined by the full-matrix least-squares method in anisotropic approximation to R = 0.056 (I) and 0.065 (II) for all 2634 (I) and 2636 (II) independent reflections; CAD-4 automated diffractometer, λMoK _α). The [MnCl₄]^2? or [ZnCl₄]^2? anion in structures I or II and the 2.2.2-cryptand dication (with two protonated N atoms) lie on crystal axis 3. The dication contains trifurcate hydrogen bonds N⁺-H(…O)₃. The bond lengths and bond angles in tetrahedral anions [MnCl₄]^2? or [ZnCl₄]^2? are disproportional, probably, due to the Jahn-Teller effect. The molecules of water of crystallization in crystals I, II are disordered over two positions.     

Coordination polymer 4,4,10,10-tetramethyl-1,3,7,9-tetraazaspiro[5.5]undecane-2,8-dione with cobalt(II) nitrate: Synthesis and molecular structure

The coordination polymer of cobalt(II) nitrate with bicyclic bis(urea), 4,4,10,10-tetramethyl-1,3,7,9-tetraazaspiro[5.5]undecane-2,8-dione (Sk) {[Co(C₁₁H₂₀N₄O₂)₂(H₂O), Co(C₁₁H₂₀N₄O₂)₂(H₂O)₂]⁴⁺(NO ₃ ^- )₄} _n (I), is synthesized for the first time, and its atomic structure is determined (CIF file CCDC no. 925792). The crystals of compound I are monoclinic: space group P2/c, a = 26.1284(6), b = 7.1763(2), c = 17.1825(5) Å, β = 105.042(3)°, V = 3111.43(15) ų, ρ_calcd = 1.474 g/cm³, Z = 2. The powder X-ray pattern at 293 K is refined using the Rietveld method to confirm the single-phase character of the obtained sample of powdered compound I: a = 26.1456(9), b = 7.1810(4), c = 17.1997(11) Å, β = 105.016(3)°, V = 3119.0(3) ų. The content of the major phase of compound I in the sample is 100 ± 1%, and impurity phases are absent. The crystal of compound I contains two types of chains oriented along the crystallographic direction [001] with similar structures but differed in the coordination numbers of the cobalt atoms. The Co(1) atom has a coordination number of 5 (trigonal bipyramid), and the coordination number of the Co(2) atom is 6 (octahedron). The nitrate anions are uncoordinated.     

Complexes of copper(II) and cobalt(II) halides with 4-(3,5-dimethyl-1<Emphasis Type="Italic">H</Emphasis>-pyrazol-1-yl)-6-methyl-2-phenylpyrimidine: Synthesis,structures, and properties

Copper(II) and cobalt(II) complexes with 4-(3,5-dimethyl-1H-pyrazol-1-yl)-6-methyl-2-phenylpyrimidine (L) of the general formula MLX₂ (M = Cu(II), X = Cl and Br; M = Co(II), X = Cl, Br, and I) were obtained. According to X-ray diffraction data, CuLBr₂ and CoLX₂ (X = Cl, Br, and I) are mononuclear molecular complexes. The ligand L is coordinated to the metal atom in a chelating bidentate fashion through the N atoms of the pyrimidine and pyrazole rings. The coordination polyhedron of the metal atom is extended to a distorted tetrahedron by two halide ions. In solution, CuLBr₂ undergoes slow transformation into CuL_(1?x)L′ _x Br₂ and the binuclear (X-ray diffraction data) Cu(I) complex [CuL_(1?x)L′ _x Br]₂ (L′ is 4-(4-bromo-3,5-dimethyl-1H-pyrazol-1-yl)-6-methyl-2-phenylpyrimidine). The complexes MLX₂ show weak antiferromagnetic interactions between the M²⁺ ions.     

Standard thermodynamic functions of complexation between copper(II) and glycine and L-histidine in aqueous solutions

The Cu²⁺–glycine–L-histidine system is studied calorimetrically at 298.15 K and an ionic strength of 0.2, 0.5, and 1.0 in aqueous solutions containing potassium nitrate. The standard thermodynamic parameters (Δ_rH°, Δ_rG°, Δ_rS°) of complexation processes are determined.     

Crystal structure and thermal analysis of diaquadi (1,2,4-triazol-5-one)zinc(II) ion nitrate

A new complex, diaquadi(1,2,4-triazol-5-one)zinc(II) ion nitrate formulated as {[Zn(TO)₂(H₂O)₂](NO₃)₂}_n (1) (1,2,4-triazole-5-one, abbreviated as: TO) was synthesized and characterized by elemental analysis, X-ray single crystal diffraction, infrared spectrum (IR), differential scanning calorimetry (DSC), thermogravimetric analysis and differential thermogravimetric analysis (TG-DTG). The X-ray structure analysis reveals that the complex is orthorhombic with space group Pbca and unit-cell parameters a=6.9504(2) Å; b=10.6473(3) Å; c=17.8555(5) Å. Based on the result of thermal analysis, the thermal decomposition process of the compound was derived. From measurement of the enthalpy of solution in water in 298.15 K, the standard molar enthalpy of solution of lignand TO and the complex were determined as 15.43±0.18 and 52.64±0.42 kJ mol^?1, respectively. In addition, the standard molar enthalpy of formation of TO(aq) was calculated as ?126.97±0.72 kJ mol^?1.     

Novel repaglinide complexes with manganese(II), iron(III), copper(II) and zinc(II): Spectroscopic,DFT characterization and electrochemical behaviour

Novel transition metal complexes with the repaglinide ligand [2-ethoxy-4-[N-[1-(2piperidinophenyl)-3-methyl-1-1butyl] aminocarbonylmethyl]benzoic acid] (HL) are prepared from chloride salts of manganese(II), iron(III), copper(II), and zinc(II) ions in water-alcoholic media. The mononuclear and non-electrolyte [M(L)₂(H₂O)₂]?nH₂O (M = Mn²⁺, n = 2, M = Cu²⁺, n = 5 and M = Zn²⁺, n = 1) and [M(L)₂(H₂O)(OH)]?H₂O (M = Fe³⁺) complexes are obtained with the metal:ligand ratio of 1:2 and the L-deprotonated form of repaglinide. They are characterized using the elemental and molar conductance. The infrared, ¹H and ¹³C NMR spectra show the coordination mode of the metal ions to the repaglinide ligand. Magnetic susceptibility measurements and electronic spectra confirm the octahedral geometry around the metal center. The experimental values of FT-IR, ¹H, NMR, and electronic spectra are compared with theoretical data obtained by the density functional theory (DFT) using the B3LYP method with the LANL2DZ basis set. Analytical and spectral results suggest that the HL ligand is coordinated to the metal ions via two oxygen atoms of the ethoxy and carboxyl groups. The structural parameters of the optimized geometries of the ligand and the studied complexes are evaluated by theoretical calculations. The order of complexation energies for the obtained structures is as follows:

$$Fe(III) complex < Cu(II) complex < Zn(II) complex < Mn(II) complex.$$

The redox behavior of repaglinide and metal complexes are studied by cyclic voltammetry revealing irreversible redox processes. The presence of repaglinide in the complexes shifts the reduction potentials of the metal ions towards more negative values.