Synthesis,characterization, and crystal structure of cobalt(II) and zinc(II) complexes with a bulky Schiff base derived from rimantadine

Two novel complexes, C₃₈H₄₈CoN₂O₂ (I) and C₃₈H₄₈N₂O₂Zn (II), were prepared through an analogous procedure with a corresponding metal chloride and a bulky Schiff base ligand (HL) which derived from rimantadine and salicylaldehyde in appropriate solvents, respectively. They were structurally characterized by the means of IR, UV-Vis, elemental analysis, molar conductance, PXRD and single-crystal X-ray diffraction (CIF files nos. 946735 (I), 893304 (II)). Single-crystal X-ray diffraction analysis reveals that I belongs to the triclinic system, \(P\overline 1 \) space group; each asymmetric unit consists of one cobalt(II) complex and one lattice ethanol molecule. In each complex molecule, cobalt(II) atom is four-coordinated via two oxygen atoms and two nitrogen atoms from the deprotonated Schiff base ligands, forming an approximate planar geometry. The crystal structure also involves strong O–H···O intermolecular hydrogen bonds between the solvent alcoholic and phenol O atoms of complex molecule. Complex II belongs to the monoclinic system, Cc space group. Each asymmetric unit consists of one zinc(II) ion and two deprotonated ligands. Zinc(II) atom lies on a twofold rotation axis and is four-coordinated via two nitrogen atoms and two oxygen atoms from the Schiff base ligands, forming a distorted tetrahedral geometry.     

Syntheses, characterization, antimicrobial and genotoxic activities of new Schiff bases and their complexes

Two new Schiff base ligands (L¹, L²) have been prepared from the reaction of 2,6-diacetylpyridine and 2-pyridinecarboxyaldehyde with 4-amino-2,3-dimethyl-1-phenyl-3-pyrozolin-5-on, and their Co(II), Cu(II), Ni(II), Mn(II), and Cr(III) metal complexes have also been prepared. The complexes are formed by coordination of N and O atoms of the ligands. Their structures were characterized by physico-chemical and spectroscopic methods. The analytical data shows that the metal to ligand ratio in the Schiff base complexes is 1:2. The Schiff base ligands and all complexes were evaluated for their in vitro antibacterial and antifungal activities by the disc diffusion method. In addition, the genotoxic properties of the ligands were studied.     

Transition metal complexes of furfural and benzil schiff bases derived from S-benzyldithiocarbazate

New nickel(II), copper(II), cobalt(III) and rohdium(III) complexes of two Schiff base ligands formed by condensation of furfural and benzil with S-benzyldithiocarbazate have been synthesized and characterized by elemental analysis and magnetic and spectroscopic measurements. The nickel(II) complexes, Ni(NS)₂ and Ni(ONS)₂ (NS and ONS stand for the uninegatively charged furfural and benzil Schiff bases, respectively) are square-planar and octahedral, respectively. The Cu(NS)Cl complex is paramagnetic with a magnetic moment fo 1.73 B.M. A halogen-bridged dimeric structure is proposed for this complex. The copper(II) complex, Cu(ONS)Cl is diamagnetic, suggesting strong antiferromagnetic interactions between a pair of copper(II) ions in a thiolo sulphur-bridged dimeric or polymeric structure. Cobalt(II) ions are oxidized in the presence of the Schiff bases with the concomitant formation of cobalt(III) complexes of empirical formulae, Co(NS)₃, Co(ONS)₂ClO₄ and Co(ONS)₂Cl, respectively, which are spin-paired and octahedral. The rhodium(III) complex of the furfural Schiff base, Rh(NS)₂Cl is tentatively assigned a halogen-bridged dimeric structre.     

Cobalt(II), nickel(II) and copper(II) complexes of a Schiff base ligand: synthesis,structural characterization and luminescence properties

A Schiff base ligand (HL), 2,4-dimethoxy-N-(5-chloro-2-hydroxybenzylidene)-benzenamine, derived from 5-chloro-2-hydroxybenzaldehyde and 2,4-dimethoxyaniline, and its metal complexes [Co(L)₂]·CH₃OH (1), [Ni(L)₂] (2), [Cu(L)₂] (3) have been synthesized. The compounds were characterized by analytical and spectroscopic methods. In addition, the structures of the Schiff base HL and its Co(II) complex were determined by single-crystal X-ray analysis. The Co(II) center is six-coordinate, being coordinated to two imine nitrogen, two phenolate oxygen and two methoxy oxygen atoms of two crystallographically independent Schiff base ligands. Luminescence properties of HL and its complexes were investigated both in solution and in the solid state.     

Syntheses,characterization and biological studies of zinc(II), copper(II) and cobalt(II) complexes with Schiff base ligand derived from 2‐hydroxy‐1‐naphthaldehyde and selenomethionine

Novel zinc(II), copper(II), and cobalt(II) complexes of the Schiff base derived from 2‐hydroxy‐1‐naphthaldehyde and D, L ‐selenomethionine were synthesized and characterized by elemental analysis, IR, electronic spectra, conductance measurements, magnetic measurements and powder XRD. The analytical data showed the composition of the metal complex to be ML(H₂O), where L is the Schiff base ligand and M = Co(II), Cu(II) and Zn(II). IR results confirmed the tridentate binding of the Schiff base ligand involving azomethine nitrogen, naphthol oxygen and carboxylato oxygen atoms. ¹H NMR spectral data of lithium salt of the Schiff base ligand [Li(HL)] and ZnL(H₂O) agreed with the proposed structures. The conductivity values of complexes between 12.50 and 15.45 S cm² mol^?1 in DMF suggested the presence of non‐electrolyte species. The powder XRD studies indicated that Co(II) complex is amorphous, whereas Cu(II) and Zn(II) complexes are crystalline. The results of antibacterial and antifungal screening studies indicated that Li(HL) and its metal complexes are active, but CuL(H₂O) is most active among them. Copyright © 2010 John Wiley & Sons, Ltd.     

Heterovalent trinuclear Co(III)-Co(II)-Co(III) complexes with N-(2-Carboxyethyl)salicylaldimines

The heterovalent trinuclear cobalt complexes [Co₂^IIIL₄ ⁱ · Co^II(H₂O)₄] · nXmY (L ⁱ are deprotonated Schiff bases derived from substituted salicylaldehydes and β-alanine; i = 1–3) were obtained and characterized. An X-ray diffraction study of the trinuclear cobalt complex with N-(2-carboxyethyl)salicylaldimine showed that the central Co(II) ion and the terminal Co(III) ions are linked by bridging carboxylate groups. Either terminal Co(III) atom is coordinated to two ligand molecules. They form an octahedral environment consisting of two azomethine N atoms, two phenolate O atoms, and two O atoms of two carboxylate groups. The central Co(II) atom is coordinated to four water molecules and to two O atoms of two bridging carboxylate ligands involved in the coordination sphere of the terminal Co(III) atoms.     

Synthesis and crystal structure of a novel trinuclear Schiff base cadmium(II) complex [Cd3L4] · 2ClO4 · 2CH3OH with antimicrobial activity

The Schiff base 2-ethoxysalicylaldehydethiosemicarbazone (HL) derived from 3-ethoxysalicylaldehyde and thiosemicarbazide and its centrosymmetric trinuclear cadmium(II) complex [Cd₃L₄] · 2ClO₄ · 2CH₃OH (I), have been successfully prepared. The structure of complex I was characterized by elemental analysis, IR spectrum, and single crystal X-ray crystallographic determination. The complex crystallizes in the monoclinic space group C2/c with unit cell dimensions a = 15.584(2), b = 19.540(2), c = 20.994(3) Å, β = 106.632(2)°, V = 6125.2(13) ų, Z = 4, R ₁ = 0.0558, and wR ₂ = 0.1696. The Schiff base coordinates to the Cd atoms through the phenolate O, ether O, imino N, and S atoms. The central Cd atom of complex I is coordinated by eight O atoms from four Schiff base ligands. The terminal Cd atoms of the complex are coordinated by six donor atoms from two Schiff base ligands. The effect of the complex on the antimicrobial activity against Staphylococcus aureus, Escherichia coli, and Candida albicans were studied.     

Dinuclear CoII/GdIII and CoIII/GdIII complexes derived from hexadentate Schiff bases: synthesis,structure, and magnetic properties

Two heterodimetallic complexes of formulae [LCo(MeOH)Gd (NO3)3] (1) and [LCo(AcO)2Gd(NO3)2] (2) (H2L = 1,3-bis[(3-methoxysalicylidene)amino]-2,2'-dimethylpropane) have been synthesized and characterized. The structure of 1 consists of discrete dinuclear entities. The cobalt(II) ion exhibits a square-pyramidal geometry, in which the basal plane is formed by the N2O2 set of the inner Schiff base site and the apical position is occupied by the methanol oxygen atom. The gadolinium(III) ion is ten-coordinate to three bidentate nitrate groups and the four oxygen atoms of the Schiff base. The phenolate oxygen atoms act as a bridge between both metal ions. Complex 2 is also formed by isolated dinuclear species. The cobalt(III) ion shows a distorted octahedral geometry in which the equatorial plane is formed by the N2O2 set of the Schiff base, and the axial positions are occupied by two oxygen atoms from both acetate groups. The gadolinium(III) ion is ten-coordinate to two bidentate nitrate groups, two oxygen atoms of the acetate groups, and the four oxygen atoms of the Schiff base. The metal ions are bridged through both the phenolate oxygen and the acetate groups, the latter acting as mu 2 ligands. Magnetic measurements on compound 1 allowed, for the first time, a quantitative evaluation of the J(Co,Gd) ferromagnetic interaction parameter (J = 0.90 cm-1). The CoII zero-field splitting has to be taken into account to fit the experimental data at low temperature (D = 4.2 cm-1). In complex 2, the magnetically isolated gadolinium center obeys a Curie law.     

Experimental and theoretical studies on bis[<Emphasis Type="Italic">μ</Emphasis>-2-methoxy-<Emphasis Type="Italic">N</Emphasis>′-(2-oxidobenzoyl)benzohydrazidato(3-)]dipyridinetricopper(II)

A novel homotrinuclear pyridine Schiff base copper(II) compound, [Cu₃(C₁₅H₁₁N₂O₄)₂(C₅H₅N)₂], has been synthesized and characterized by elemental analysis and X-ray single crystal deterimination. X-ray structural determination reveals that each copper(II) ion has a distorted square-planar geometry. The central copper ion is coordinated by two O and two N atoms from two Schiff base ligands, while each terminal copper ion is coordinated by one N and two O atoms of one Schiff base ligand and by one N atom of a pyridine molecule. Density funcational theory (DFT) method calculations of the structure, atomic charges distribution and natural bond orbital (NBO) analyses have been performed. The coordinate stabilization energies show that the trinuclear copper(II) compound is very stable.     

Syntheses and structures of 2,4-dichloro-6-(cyclopropyliminomethyl)phenol and its copper(II) complex

A new Schiff base ligand, 2,4-dichloro-6-(cyclopropyliminomethyl)phenol, and a copper(II) complex containing it have been synthesized and characterised. The ligand and complex crystallise in space groups Cmca and C2/c, respectively. In the complex, the Cu atom is four-coordinate (distorted tetrahedral), bonded to two imine N and two phenolate O atoms from two Schiff base ligands. Bond lengths associated with the donor atoms in the complex are different to those in the ligand. The structure is compatible with spectra of the bulk sample.     

Bis{μ‐2‐[3‐(cyclo­hexyl­ammonio)­propyl­imino­methyl]­phenolato}bis­[di­chloro­copper(II)]

The title compound, [Cu₂(C₁₆H₂₄N₂O)₂Cl₄], is a dinuclear copper(II) complex with inversion symmetry. Each Cu^II atom is five‐coordinated by two O and one N atom from two Schiff base ligands, and by two Cl atoms, giving an approximately trigonal–bipyramidal coordination environment.     

SYNTHESIS AND CHARACTERIZATION OF DIAQUA(3-pTOLYLIMINO-2-BUTANONE OXIMATO)(3-p-TOLYLIMINO-2-BUTANONE OXIME)NICKEL(II) PERCHLORATE

Abstract

[Ni(L^?1)(HL)(H₂O)₂].ClO₄ with a Schiff base ligand L (HL = 3-p-tolylimino-2-butanone oxime) was prepared and structurally characterized by IR, cyclic voltammetry and X-ray diffraction methods. The nickel atom has distorted octahedral coordination consisting of four nitrogen atoms and two oxygen atoms. The equatorial plane is formed by two oxime nitrogen atoms and two imine nitrogen atoms of two Schiff base ligand (L^?1 and HL) with Ni‐ N bond distances between 2.01(1) and 2.11(1)Å. Water oxygen atoms occupy axial positions with Ni‐ O bond distances of 2.06(1) and 2.15(1) Å. The oxime groups in the Schiff base ligands are coordinated to Ni atom through their nitrogen atoms. One asymmetric intramolecular hydrogen bridge between the two oxime groups is found in the title complex.     

Structural and spectroscopic characterization of a new luminescent NiII complex: bis{2,4‐dichloro‐6‐[(2‐hydroxypropyl)iminomethyl]phenolato‐κ3O,N,O′}nickel(II)

The design and preparation of transition‐metal complexes with Schiff base ligands are of interest due to their potential applications in the fields of molecular magnetism, nonlinear optics, dye‐sensitized solar cells (DSSCs), sensing and photoluminescence. Luminescent metal complexes have been suggested as potential phosphors in electroluminescent devices. A new luminescent nickel(II) complex, [Ni(C₁₀H₁₀Cl₂NO₂)₂], has been synthesized and characterized by single‐crystal X‐ray diffraction and elemental analysis, UV–Vis, FT–IR, ¹H NMR, ¹³C NMR and photoluminescence spectroscopies, and LC–MS/MS. Molecules of the complex in the crystals lie on special positions, on crystallographic binary rotation axes. The Ni^II atoms are six‐coordinated by two phenolate O, two imine N and two hydroxy O atoms from two tridentate Schiff base 2,4‐dichloro‐6‐[(2‐hydroxypropyl)iminomethyl]phenolate ligands, forming an elongated octahedral geometry. Furthermore, the complex exhibits a strong green luminescence emission in the solid state at room temperature, as can be seen from the (CIE) chromaticity diagram, and hence the complex may be a promising green OLED (organic light‐emitting diode) in the development of electroluminescent materials for flat‐panel‐display applications.     

Bis[di(hydroxymethyl)phosphinato]diaquacobalt(II), [Co(H2O)2{(HOCH2)2PO2}2]: Synthesis, properties, and crystal structure

The synthesis and some properties of the Co(II) complex with di(hydroxymethyl)phosphinic acid (HL) of the composition CoL₂·2H₂O are described. X-ray powder diffraction analysis confirmed the phase homogeneity of the polycrystalline sample. The crystal structure is determined by X-ray diffraction method. The Co atom is located in the center of octahedron formed by the O atoms of two ligands L and of two water molecules. The ligand L performs bidentate-chelate function and is bonded to the Co atom through the O atoms of the phosphinate group and of one alcohol group.     

Studies on Binuclear Co(II) and Cu(II) Complexes of Tridentate N-(2-Carboxyphenyl)Salicylideneimine

Homo Cu(II) and Co(II) binuclear complexes H[MLClMCl₂] formed by using the donor properties of the cis two oxygen atoms of the tridentate N-(2-carboxyphenyl)-salicylaldimine Schiff base derived from salicylaldehyde and anthranilic acid have been synthesized. It was found that the Cu(II) “complexed ligand” readily reacts with CoCl₂ to form mononuclear Co(II) and binuclear oxygen bridged Co(II) complex [Co₂-L₂](H₂O)₂. The structure of the so prepared complexes was investigated using microchemical analysis, molar conductance measurements as well as electronic and vibrational spectral studies. It was concluded that in the Cu(II) binuclear complex, the Cu(II) ion inside the “complexed ligand” has a planar structure while the other Cu(II) ion is distorted away from planarity. In the Co(II) binuclear complex, the Co atom of the “complexed ligand” is distorted from tetrahedral structure when it coordinates to the second Co atom.     

New azo‐azomethine‐based transition metal complexes: Synthesis,spectroscopy, solid‐state structure,density functional theory calculations and anticancer studies

A novel tetradentate azo‐Schiff base ligand (H₂L) was synthesized by 2:1 molar condensation of an azo‐aldehyde and ethylenediamine. Its mononuclear Cu(II), Ni(II), Co(II) and Zn(II) complexes were prepared and their structures were confirmed using elemental analysis, NMR, infrared and UV–visible spectroscopies and molar conductivity measurements. The results suggest that the metal ion is bonded to the tetradentate ligand through phenolic oxygens and imine nitrogens of the ligand. The solid‐state structures of the azo‐Schiff base ligand and its Cu(II) complex were determined using single‐crystal X‐ray diffraction studies. The azo‐Schiff base ligand lies on a crystallographic inversion centre and thus the asymmetric unit contains half of the molecule. X‐ray data revealed that keto–amine tautomer is favoured in the solid‐state structure of the ligand. In the structure of the Cu(II) complex, the Cu(II) ion is coordinated to two phenolate oxygen atoms and two imine nitrogen atoms of the azo‐Schiff base ligand with approximate square planar geometry. The anticancer activity of the synthesized complexes was investigated for human cancer cell line (MCF‐7) and cytotoxicity of the synthesized compounds was determined against mouse fibroblast cells (L929). The ligand and its complexes were found to show antitumor activity. The synthesized metal complexes were optimized at the B3LYP/LANL2DZ level and a new theoretical formula for MCF‐7 cells was also derived.     

Chloro[N,N′‐ethyl­enediimino­bis(acetyl­acetonato)]gallium(III)

In the title compound, [Ga(C₁₂H₁₈N₂O₂)Cl], the Ga atom is coordinated to a Cl atom and the two imine N and two enolate O atoms of the Schiff base ligand. The literature reveals few examples of a five‐coordinate GaO₂N₂Cl environment, and only two where both the N and the O atoms are contained within the same ligand. This configuration has the effect of constraining the complex into a square‐pyramidal geometry with less distortion than if formed by two or more ligands. The Ga—N and Ga—O distances are within the ranges expected for Ga–Schiff base derivatives. This compound is also the first group 13 complex containing the N,N′‐ethyl­ene­bis­(acetyl­acetoneimine) (acacen) ligand.     

Synthesis and spectroscopic studies of the cobalt(II) complex with methyl 2-pyridylmethylidenehydrazinecarbodithioate (HNNS)

A new cobalt(II) complex with the Schiff base methyl 2-pyridylmethylidenehydrazinecarbodithioate (HNNS), Co(NNS)₂, has been synthesized and characterized using single-crystal X-ray diffraction and spectroscopy (IR, UV–Vis, MS and EA). Complex [Co(NNS)₂] crystallizes in the orthorhombic, space group Pna2(1). The coordination geometry around Co(II) in the complex is distorted octahedral and the two ligands in the mer-configuration (S and tertiary N atom cis to each other and the iminic N atoms trans). Furthermore, the neutral molecule unit Co^II(NNS)₂ is connected by hydrogen bonds C–H ··· S and forms a three dimensional ordered network structure.     

Synthesis and crystal structures of <Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>'-bis(5-methylsalicylidene)ethane-1,2-diamine and its bromido-, phenolato-, and dicyanoamido-cobridged polymeric copper(II) complex

A bis-Schiff base N,N'-bis(5-methylsalicylidene)ethane-1,2-diamine (H₂L) was prepared and characterized by elemental analysis, ¹H NMR and ¹³C NMR spectra, MS, and single crystal X-ray diffraction (CIF file CCDC no. 1022761 (H₂L)). Reaction of the Schiff base with copper bromide and sodium dicyanoamide in methanol gave a novel bromido-, phenolato-, and dicyanoamido-cobridged polymeric copper(II) complex, ({Cu₂LBr[N(CN)₂]}₂)_n (I). Structure of complex I was characterized by elemental analysis and single crystal X-ray diffraction (CIF file CCDC no. 1022762 (I)). The smallest repeat unit of complex I is a dicyanoamide bridged tetranuclear copper(II) complex moiety, {Cu₂LBr[N(CN)₂]}₂, in which there possesses a crystallographic inversion symmetry. The tetranuclear moieties are further linked through Br atoms, forming a zigzag chain. The chains are further linked by dicyanoamide ligands, forming a 2D network. One Cu atom in complex I is coordinated by two N and two O atoms of the Schiff base ligand and one Br atom, forming square pyramidal geometry. The other Cu atom is coordinated by two N atoms of the Schiff base ligand, two N atoms of dicyanoamide ligands, and one Br atom, forming square pyramidal geometry. The bromido-, phenolato-, and dicyanoamido-cobridged Cu···Cu distances are 4.823(2), 2.955(1), and 7.121(3) Å, respectively. The [Cu₂L] units are linked by the bridging groups, to form 2D chains along the xy plane.     

Solution Equilibrium Studies on Salicylidene Aminoguanidine Schiff Base Metal Complexes: Impact of the Hybridization with L-Proline on Stability,Redox Activity and Cytotoxicity

The proton dissociation processes of two tridentate salicylidene aminoguanidine Schiff bases (SISC, Pro-SISC-Me), the solution stability and electrochemical properties of their Cu(II), Fe(II) and Fe(III) complexes were characterized using pH-potentiometry, cyclic voltammetry and UV-visible, ¹H NMR and electron paramagnetic resonance spectroscopic methods. The structure of the proline derivative (Pro-SISC-Me) was determined by X-ray crystallography. The conjugation of L-proline to the simplest salicylidene aminoguanidine Schiff base (SISC) increased the water solubility due to its zwitterionic structure in a wide pH range. The formation of mono complexes with both ligands was found in the case of Cu(II) and Fe(II), while bis complexes were also formed with Fe(III). In the complexes these tridentate ligands coordinate via the phenolato O, azomethine N and the amidine N, except the complex [Fe(III)L₂]⁺ of Pro-SISC-Me in which the (O,N) donor atoms of the proline moiety are coordinated beside the phenolato O, confirmed by single crystal X-ray crystallographic analysis. This binding mode yielded a stronger Fe(III) preference for Pro-SISC-Me over Fe(II) in comparison to SISC. This finding is also reflected in the lower redox potential value of the iron-Pro-SISC-Me complexes. The ligands alone were not cytotoxic against human colon cancer cell lines, while complexation of SISC with Cu(II) resulted in moderate activity, unlike the case of its more hydrophilic counterpart.