Synthesis,crystal structures,and antibacterial activity of copper(II) and cobalt(III) complexes derived from 2-[(2-dimethylaminoethylimino)methyl]-4-methylphenol

A new tetranuclear copper(II) complex (I) and a new mononuclear cobalt(III) complex (II) have been synthesized from the Schiff base compound 2-[(2-dimethylaminoethylimino)methyl]-4-methylphenol. The complexes have been characterized by physico-chemical and spectroscopic methods, as well as single crystal X-ray determination (CIF files CCDC nos. 1447778 (I) and 1447779 (II)). The Cu atoms in complex I are in square pyramidal coordination, and the Co atom in complex II is in octahedral coordination. Crystal structures of the complex are stabilized by hydrogen bonds and π···π interactions. The complexes and the Schiff base compound were assayed for antibacterial activities against three Gram-positive bacterial strains (B. subtilis, S. aureus, and St. faecalis) and three Gram-negative bacterial strains (E. coli, P. aeruginosa, and E. cloacae) by MTT method. As a result, the complexes showed effective antimicrobial activity against the microorganisms tested.     

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.     

Luminescent properties of europium(III) and terbium(III) complexes with para- and ortho-ethoxybenzoic acids

The luminescent properties of europium(III) and terbium(III) complexes with para- and ortho-ethoxybenzoic acids are studied. The excitation energies of the triplet states of ligands are determined, a hypothesis is made about the efficient luminescence of europium(III) and terbium(III) complexes, the geometry of the coordination polyhedron of a europium complex is established, and the luminescence quantum yields of the complexes in solution are determined.     

Synthesis,characterization, spectroscopic and catalytic oxidation studies of Fe(III), Ni(II), Co(III), V(IV) and U(VI) Schiff base complexes with N,O donor ligands derived from 2,3-diaminopyridine

Fifteen new complexes of transition metals were designed using three Schiff base ligands and aldol condensation of 2,3-diaminopyridine with 5-R-2-hydroxybenzaldehyde (R = F, Cl, Br) in the 1:2 molar ratio. The tetradentate ligands N,N′-bis(5-R-2-hydroxybenzaldehyde) pyridine were acquired with the common formula H₂[(5-R-sal)₂py] and characterized by IR, UV–Vis spectra, ¹H-NMR and elemental analysis. These ligands produce 1:1 complexes M[(5-R-sal)₂py] with Fe(III), Ni(II), Co(III), V(IV) and U(VI) metal ions. The electronic property and nature of complexes were identified by IR, UV–Vis spectra, elemental analysis, X-ray crystallography and cyclic voltammetric methods. The catalytic activity of complexes for epoxidation of styrene with UHP as primary oxidant at minimal temperature (10 °C) has been planned. The spectral data of the ligands and their complexes are deliberate in connection with the structural changes which happen due to complex preparation. The electrochemical outcome has good conformability with what suggested for electronic interaction among metal center and ligand by the UV–Vis and IR measurements.     

Syntheses and Crystal Structures of Quinidinum-Zinc(II)-Trichloride and Quinidinum Iron(III) Tetrachloride Hydrogen Chloride Hydrate

A mononuclear coordination complex, quinidinum-zinc(II)-trichloride (I), and a multi-component ionic complex, quinidinum iron(III) tetrachloride hydrogen chloride hydrate (II), have been synthesized and characterized by elemental analyses, IR spectra, and single crystal X-ray diffraction (CIF files nos. 1497628 (I) and 1497629 (II)). The weak hydrogen-bonding interactions exist in both complexes I and II. Both complexes crystallize in the chiral space groups with the absolute configuration. Complex I crystallizes in the orthorhombic space group P2₁2₁2₁ with a = 7.6651(6), b = 11.4923(9), c = 24.653(2) Å, and Z = 4. Complex II crystallizes in the monoclinic space group P2₁ with a = 6.6425(15), b = 18.660(4), c = 10.958(3) Å, β = 104.973(3), and Z = 2.     

Synthesis,characterization, crystal structures,and antimicrobial activity of cobalt(II) and iron(III) complexes derived from N'-(2-hydroxybenzylidene)-3-methylbenzohydrazide

A new cobalt(II,III) complex, [Co^IIIL₂]₂[Co ₂ ^II (HL)₂(OH₂)₂(CH₃OH)₂] ? 2H₂O (I) and a new iron(III) complex, [Fe^III(HL)₂](NO₃) (II), where L^2– and HL^– are the dianionic and monoanionic form of N'-(2-hydroxybenzylidene)-3-methylbenzohydrazide, respectively, have been prepared and characterized by elemental analyses, infrared and UV-Vis spectroscopy and single-cyrstal X-ray diffraction (CIF files CCDC nos. 1417971 (I), 1417979 (II)). Complex I crystallizes in the monoclinic space group P2₁/n with unit cell dimensions a = 16.1665(9), b = 14.5692(8), c = 19.086(1) Å, β = 96.347(1)°, V = 4467.9(4) ų, Z = 2, R ₁ = 0.0521, and wR ₂ = 0.1411. Complex II crystallizes in the orthorhombic space group Pbcn with unit cell dimensions a = 12.475(1), b = 12.202(1), c = 18.859(2) Å, V = 2870.8(4) ų, Z = 4, R ₁ = 0.0796, and wR ₂ = 0.1981. The metal atoms in the complexes are in octahedral coordination. Crystals of the complexes are stabilized by hydrogen bonds. The efficiency of the aroylhydrazone and the two complexes was evaluated against B. subtilis, S. aureus, E. coli, P. fluorescence, C. albicans and A. niger, with the complexes demonstrating enhanced activity relatively to the free ligand.     

Development of liquid-liquid extraction and separation method for ruthenium(III) with 2-octylaminopyridine from succinate media: Analysis of catalysts

Ruthenium(III) has been efficiently extracted from 0.05 M sodium succinate at pH 9.5 by 2-octylaminopyridine in xylene and stripped with aqueous 10% (w/v) thiourea solution and determined spectrophotometrically. Various parameters viz., pH, weak acid concentration, reagent concentration, stripping agents, contact time, loading capacity, aq.: org. volume ratio, solvent has been thoroughly investigated for quantitative extraction of ruthenium(III). The utility of method was analyzed by separating the ruthenium(III) from binary mixture along with the base metals like Cu(II), Ag(I), Fe(II), Co(II), Bi(III), Zn(II), Ni(II), Se(IV), Te(IV), Al(III) and Hg(II) as well as platinum group metals (PGMs). Ruthenium(III) was also separated from ternary mixtures like Os(VIII), Pd(II); Pd(II), Pt(IV); Pd(II), Au(III); Pd(II), Cu(II); Fe(II), Cu(II); Ni(II), Cu(II); Co(II), Ni(II); Se(IV), Te(IV); Rh(III), Pd(II); Fe(III), Os(VIII). The stoichiometry 1: 2: 1 (metal: succinate: extractant) of the proposed complex was determined by slope analysis method by plotting graph of logD _[Ru(III)] versus logC _[2-OAP] and logD _[Ru(III)] versus logC _[succinate]. The interference of various cations and anions has been studied in detail and the statistical evaluations of the experimental results are reported. The method was successfully applied for the analysis of ruthenium in various catalysts, synthetic mixtures corresponding to the composition of alloys and minerals.     

A new high-spin iron(III) bis(aqua) complex with the <Emphasis Type="Italic">meso</Emphasis>-tetra(para-chlorophenyl)porphyrin: X-ray crystallography,Hirshfeld surface analysis,magnetic, EPR and electrochemical properties

Chemical preparation of the bis(aqua) iron(III) metalloporphyrin [Fe^III(TClPP)(H₂O)₂](SO₃CF₃)·2(Pnz)·3/4(C₆H₁₂)·2H₂O (TClPP?=?TClPP?=?5,10,15,20-tetra(para-chlorophenyl)porphyrinato and Pnz?=?phenazine) coordination complex (I) was made. The crystal structure of (I) was determined by X-ray single-crystal diffraction and elucidated by Hirshfeld surface approach. Magnetic, spectroscopic and electrochemical properties were also reported and discussed. The mean equatorial distance (Fe–Np) between the iron(III) atom and porphyrin nitrogen atoms is appropriate to a high-spin (S?=?5/2) iron(III) complex. The high-spin state is also confirmed by both magnetic and electron paramagnetic resonance (EPR) spectroscopy data. The repetitive building unit of the crystal structure provides [Fe^III(TClPP)(H₂O)₂]⁺ ion complexes, two non-coordinated Pnz molecules and two water molecules which are interconnected by O–H···O/N/Cl, C–H···O/F/Cl hydrogen bonds, and by C–X···π, C–H···π and π–π stacking intermolecular contacts, forming a 3D supramolecular network. The role and nature of these intermolecular interactions were quantitatively analysed by 3D Hirshfeld surface analysis and associated 2D fingerprint plots. Cyclic voltammetry measurements indicate a one-electron reversible reduction wave with an E_1/2 (Fe(III)/Fe(II) half-potential value of ?0.24 V, which confirms the high-spin S?=?5/2 state of the studied complex.     

Dioxygen activation with a cytochrome P450 model. Characterization and electrochemical study of new unsymmetrical tetradentate Schiff-base complexes with iron(III) and cobalt(II)

Salicylaldehyde or 5-bromosalicylaldehyde react with 2,3-diaminophenol to give two unsymmetrical Schiff-bases H₂L¹, H₂L², respectively. With Fe(III) and Co(II), these ligands lead to four complexes: Fe(III)ClL¹, Fe(III)ClL², Co(II)L¹, Co(II)L². The structures of these complexes were determined by mass spectroscopy, infrared and electronic spectra. Cyclic voltammetry in dimethylformamide (DMF) showed irreversible waves for both ligands. In the same experimental conditions, Fe(III)ClL¹ exhibited a reversible redox couple Fe(III)/Fe(II) while the three other complexes showed quasi-reversible systems. The behavior of some of these complexes in the presence of dioxygen and the comparison with cytochrome P450 are described.     

Synthesis and crystal structures of cobalt(III) and zinc(II) complexes derived from 4-chloro-2-[(2-morpholin-4-ylethylimino)methyl]phenol with urease inhibitory activity

A new mononuclear cobalt(III) complex, [CoL₂(N₃)]₂ · CH₃OH (I), and a new mononuclear zinc(II) complex, [ZnLCl(CH₃OH)] (II) (HL = 4-chloro-2-[(2-morpholin-4-ylethylimino)methyl]phenol), were prepared and structurally characterized by elemental analyses, infrared spectroscopy, and single- crystal X-ray diffraction. The crystal of I is monoclinic: space group P2₁/c, a = 18.742(2) Å, b = 15.197(2) Å, c = 25.646(2) Å, β = 125.996(3)°, V = 5909.8(11) ų, Z = 4. The crystal of II is monoclinic: space group P2₁/c, a = 7.257(1) Å, b = 24.707(2) Å, c = 9.637(1) Å, β = 101.557(2)°, V = 1692.9(3) ų, Z = 4. The Co atom in I is in an octahedral coordination, and the Zn atom in II is in a trigonal-bipyramidal coordination. The urease inhibitory test shows that complex I has strong urease inhibitory activity, while complex II has no activity.     

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.     

Transition metal chelates: Synthesis,physicochemical, thermal,and biological studies

The transition metal complex of Mn(II), Co(II), Ni(II), Cu(II), Ti(III), Cr(III), Fe(III), Zr(IV), and UO₂(VI) ion with a Schiff’s base ligand derived from 2-hydroxy-[2-oxo-1,2-dihydro-3H-indol-3-ylidene]-benzohydrazide have been prepared. The complexes have been characterized by elemental analysis data, IR and electronic absorption spectra, magnetic moments, and thermogravimetric analysis data. The complexes of the 1: 1 metal-to-ligand stoichiometry have been formed. The physico-chemical data have suggested the octahedral geometry for all the complexes except for Cu(II); the Cu(II) complex has been square planar. Thermal analysis data of the ligand and its complexes have been analyzed, and the kinetic parameters have been determined using the Horowitz–Metzger method. According to the solid-state electrical conductivity measurements, the ligand and its complexes are semiconducting in nature. The antimicrobial activity of the ligand and the complexes towards E. coli, S. typhi, P. aeruginosa, and S. aureus has been tested by the disc diffusion method.     

Synthesis,spectroscopic, and antimicrobial study of Ca(II), Fe(III), Pd(II), and Au(III) complexes of amoxicillin antibiotic drug

Synthesis, spectroscopic characterization, theoretical and antimicrobial studies of Ca(II), Fe(III), Pd(II), and Au(III) complexes of amoxicillin (amox) antibiotic drug are presented in the current paper. Structure of 1: 1 (metal: amox) complexes were elucidated on the basis of elemental analyses, and IR, Raman, ¹H NMR, and electronic spectral data. According to molar conductance measurements the complexes had electrolyte nature. Amoxicillin reacted with metal ions as a tridentate ligand coordinated with metal ions via–NH₂,–NH, and β-lactam carbonyl groups. The complexes were formulated as [Ca(amox-Na)(H₂O)]·Cl₂·4H₂O (1), [Fe(amox-Na)(H₂O)₃]·Cl₃·3H₂O (2), [Pd(amox-Na)(H₂O)]·Cl₂ (3), and [Au(amox-Na)(H₂O)]·Cl₃ (4). Kinetic thermodynamic parameters (E*, ΔS*, ΔH*, and ΔG*) were calculated based on the Coats–Redfern and Horowitz–Metzger methods using thermo gravimetric curves of TG and DTG. Nanosize particles of amoxicillin complexes have been studied by XRD, SEM, and TEM methods. Theoretical studies of the synthesized complexes have been performed.     

Stepwise magnetic behavior of the liquid crystal iron(III) complex

EPR and Mössbauer spectroscopy is used to study a new liquid crystal complex of iron(III) with a Schiff base: 4,4′-dodecyloxybenzoyloxybenzoyl-4-oxysalicylidene-2-aminopyridine with a PF ₆ ^? counterion. It is shown that Fe(III) ions exist only in the high-spin (HS, S = 5/2) state. It is found that under the influence of temperature the system demonstrates the stepwise behavior of the product of the integrated intensity of EPR lines (I) and temperature (proportional to χ T, where χ is the magnetic susceptibility) with an inflection point at ～80 K. Above 80 K a new EPR spectrum is detected due to the excited S = 2 state and the formation of dimeric molecules (through oxygen bridges) with a strong intramolecular antiferromagnetic exchange interaction J ₁ = 162.1 cm^?1. Below 80 K iron(III) complexes are organized in 1D chains where the exchange value J ₂ = 2.1 cm^?1. At 80 K there is a structural phase transition in the system: the transition from a 1D chain organization of HS Fe(III) centers to dimeric molecules. Based on quantum chemical calculations a model of the binuclear iron(III) complex is proposed.     

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.     

A dinuclear oxygen-bridged Schiff base iron(III) complex derived from <Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>′-bis(4-methoxy-2-hydroxybenzylidene)-2,2-dimethylpropane-1,3-diamine

The μ-oxo-bridged Fe(III) dimer complex [{Fe(4-MeOL1)}₂(μ-O)]?HOCH₃, (H₂-4-MeOL1 = N,N′-bis(4-methoxy-2-hydroxybenzylidene)-2,2-dimethylpropane-1,3-diamine), 1 is synthesized and characterized by single crystal X-ray diffraction. Complex 1 contains a [{Fe(4-MeOL1)}2(μ-O)] dimeric unit with a methanol solvent molecule of crystallization. Each Fe(III) ion has a distorted square-pyramidal coordination geometry. In the basal plane, the Fe(III) atom is coordinated by two N and two O atoms of the Schiff base ligand. The apical position is occupied by a bridging O^2– ion, linking another Fe(III) ion in the complex. There are intermolecular C–H…O and C–H…π interactions among the dinuclear complexes.     

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.

     

Synthesis,Crystal Structures,and Biological Activity of Manganese(III) Complexes Derived from BIS-Schiff Bases

Two new manganese(III) complexes, [Mn^IIIL¹(Dca)(MeOH)] (I) and [Mn^IIIL₂(N₃)₂] (II), where L¹ and L² are the dianionic form of N,N'-3,4-chlorophenylene-bis(5-methylsalicylaldimine) (H₂L¹) and N,N'-3,4-nitrophenylene-bis(5-methylsalicylaldimine) (H₂L₂), respectively, and Dca is dicyanoamide, have been synthesized and characterized. The complexes were characterized by elemental analyses, IR, UV-Vis spectra, molar conductivity, and single crystal X-ray diffraction (CIF files nos. 1054200 (I), 1054336 (II)). The Mn atoms in the structures are in octahedral coordination. In the crystal structure of complex I, molecules are linked through intermolecular O–H···N hydrogen bonds to form 1D chains running along the x axis. In both complexes, there exist π···π interactions among molecules. The complexes and the Schiff bases were assayed for antibacterial activities against three Gram-positive bacterial strains (B. subtilis, S. aureus, and St. faecalis) and three Gram-negative bacterial strains (E. coli, P. aeruginosa, and E. cloacae) by MTT method.     

A mononuclear nickel(II) complex and a dinuclear manganese(III) complex derived from N,N'-bis(5-methoxysalicylidene)-1,2-ethanediamine: Synthesis,crystal structures and catalytic epoxidation property

Synthesis and characterization of a mononuclear nickel(II) complex [NiL] · CH₃OH (I) and a dinuclear manganese(III) complex [Mn₂L₂(NCS)₂] (II) derived from the bis-Schiff base N,N'-bis(5-methoxysalicylidene)-1,2-ethanediamine (H₂L) are reported. The complexes were characterized by elemental analyses, IR spectra and molar conductivity. Single crystal X-ray structures of the complexes have been determined (CIF files CCDC nos. 1056778 (I) and 1056688 (II)). The Ni atom in I is in a square planar coordination, and the Mn atom in II is in an octahedral coordination. Catalytic property for epoxidation of styrene by the complexes using PhIO and NaOCl as oxidant has been studied. As a result, complex II is efficient for the styrene epoxidation.