Nickel Schiff Base Research Articles

Preparation and characterization of nickel oxide nanoparticles via solid state thermal decomposition of dinuclear nickel(II) Schiff base complex [Ni2(Brsal-1,3-ph)2] as a new precursor

The synthesis and characterization of nickel oxide nanoparticles via solid state thermal decomposition of a dinuclear nickel(II) complex, [Ni2(Brsal-1,3-ph)2] as a new precursor is reported. [Ni2(Brsal-1,3-ph)2] complex is characterized by elemental analyses and Fourier transform infrared (FT-IR) spectroscopy. Thermogravimetric analysis reveals its thermal stability and decomposition pattern. Solid state thermal decomposition of the complex at 450 °C for 3 h produces nickel oxide nanoparticles which are characterized by FT-IR spectroscopy, X-ray powder diffraction, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). SEM and TEM images demonstrate the square shape of the NiO nanoparticles of between 10 and 15 nm.

Catalytic Asymmetric Synthesis of Spirooxindoles via Addition of Isothiocyanato Oxindoles to Aldehydes Under Dinuclear Nickel Schiff Base Catalysis

Catalytic Asymmetric Synthesis of Spirooxindoles via Addition of Isothiocyanato Oxindoles to Aldehydes Under Dinuclear Nickel Schiff Base Catalysis

Nickel(II) complexes with Schiff bases derived from 2-acetylpyrazine and tryptophan: synthesis, crystal structures and DNA interactions

A pair of stereoisomers of nickel Schiff base complexes, namely [Ni(C17H15N4O2)2·2CH3OH]n (1) (C17H15N4O2 = 2-acetylpyrazine-l-tryptophan) and [Ni(C17H15N4O2)2·2CH3OH]n (2) (C17H15N4O2 = 2-acetylpyrazine-d-tryptophan), were synthesized and characterized by physico-chemical and spectroscopic methods. The X-ray diffraction single-crystal analyses indicate that the structure of 2 is essentially 0D monomeric, while a 2D layer structure is formed through N–H…O intermolecular hydrogen bonds for 1. The interactions between complex 1 and calf thymus DNA were investigated by spectroscopic and viscometric methods. The results indicate that complex 1 interacts with DNA very strongly (K b = 1.01 × 107 mol−1 L and K sq = 1.11). The nature of the binding seems to be mainly an electrostatic interaction between DNA and the complex. However, other binding modes, such as hydrogen bonding, may also be present in this system.

Sodium-mediated self-assembly of two nickel(II) Schiff base complexes: crystal structure and characterizations

Sodium-assisted self-assembly of two nickel(II) Schiff base complexes under similar reaction conditions yield hetero-metallic compounds [{Ni(salpn)}2Na(ClO4)] (1) and [{Ni(salpr)}3Na][Ni(salpr)]2ClO4·2H2O (2) (where salpn = N,N′-bis-(salicylidene)-1,3-diaminopropane and salpr = N,N′-bis-(salicylidene)-1,2-diaminopropane). Both have been characterized by physico-chemical techniques and single-crystal X-ray diffraction. Crystal structure reveals that in the tri-metallic system of 1 sodium is sandwiched between two [Ni(salpn)] units while the hexametallic system of 2 consists of tetrametallic cluster ion [{Ni(salpr)}3Na]+ with encapsulated sodium by three [Ni(salpr)] units. In both complexes, sodium adopts distorted trigonal prismatic geometry leaving nickel(II) in a distorted square-planar environment. Structural characterization also reveals that 2 : 1 (for 1) and 3 : 1 (for 2) self-assemblies of metallo-ligand and sodium were achieved with slight variation in ligand backbone.

Synthesis and crystal structures of two new Schiff base cobalt(II) and nickel(II) complexes

The Schiff base ligand (HL) obtained from phenylmethanamine and 5-methoxysalicylaldehyde are used as ligands for Co(II) and Ni(II) resulting in complexes [Co(L)2] (I) and [Ni(L)2] (II), and their solid state structures were determined by X-ray crystallography. In both complexes, weak interactions play an important role in the molecular self-assembly. Complex I was stacked up to the 2D layers by C-H…O hydrogen bonds and C-H…π interactions. In contrast, complex II was extended into 2D sheet by C-H…O hydrogen bonds, the C-H…π interactions, and edge-to-face interactions.

Preparation and Characterization of NiO Nanoparticles Via Solid-State Thermal Decomposition of Nickel(II) Schiff Base Complexes [Ni(salophen)] and [Ni(Me-salophen)

This study focuses on the preparation and characterization of nickel oxide nanoparticles from nickel(II) Schiff base complexes as new precursors. At first nickel(II) complexes [Ni(salophen)] and [Ni(Me-salophen)] were synthesized and characterized by elemental analyses and FT-IR spectroscopy. Then NiO nanoparticles were prepared by solid-state thermal decomposition at 550 oC for 3.5 h. The FT-IR spectrum confirmed the composition of products. The crystalline structures and morphology of products were studied by X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). XRD results revealed that the obtained products were nickel oxide. SEM and TEM images demonstrated that the NiO nanoparticles have uniform shape with size between 35 and 70 nm.

Synthesis, antimicrobial, DNA-binding and photonuclease studies of Cobalt(III) and Nickel(II) Schiff base complexes

New metal complexes of the type [M(nih)(L)](PF6)n·xH2O and [M(nih)2](PF6)·xH2O (where M=Co(III) or Ni(II), L=1,10-phenanthroline (phen)/or 2,2′ bipyridine (bpy), nih=2-hydroxy-1-naphthaldehyde isonicotinoyl hydrazone, n=2 or 1 and x=3 or 2) have been synthesized and characterized by elemental analysis, magnetic, IR and 1H NMR spectral data. The electronic and magnetic moment 2.97–3.07B.M. data infers octahedral geometry for all the complexes. The IR data reveals that Schiff base (nih) form coordination bond with the metal ion through azomethine-nitrogen, phenolic-oxygen and carbonyl-oxygen in a tridentate fashion. In addition, DNA-binding properties of these six metal complexes were investigated using absorption spectroscopy, viscosity measurements and thermal denaturation methods. The results indicated that the nickel(II) complex strongly bind with calf-thymus DNA with intrinsic DNA binding constant Kb value of 4.9×104M−1 for (3), 4.2×104M−1 for (4), presumably via an intercalation mechanism compared to cobalt(III) complex with Kb value of 4.6×104M−1 (1) and 4.1×104M−1 (2). The DNA Photoclevage experiment shows that, the complexes act as effective DNA cleavage agent.

ChemInform Abstract: Catalytic Asymmetric Amination of Oxindoles under Dinuclear Nickel Schiff Base Catalysis.

AbstractThe binuclear nickel Schiff base complex NSB is an efficient catalyst for the asymmetric amination of oxindoles (I) with diester (II).

Synthesis, structures and urease inhibition studies of copper(II) and nickel(II) complexes with bidentate N,O-donor Schiff base ligands

Five mononuclear copper(II) and nickel(II) complexes of Schiff base ligands derived from 4-hydroxyphenethylamine and 2-phenylethylamine were synthesized and determined by single crystal X-ray analysis. The crystal structures of these complexes presented the square planar coordination geometry at the metal center. The inhibitory activity of all the obtained complexes was tested in vitro against jack bean urease. It was found that Schiff base copper(II) complexes, namely [Cu(C15H13BrNO2)2]·2(C6H7N) (1), [Cu(C15H12Br2NO2)2]·2(DMF) (2), Cu(C19H16NO2)2 (3) and Cu(C19H16NO)2 (5), showed strong inhibitory activity against jack bean urease (IC50=1.45–3.59μM), while Schiff base nickel(II) complex, [Ni(C19H16NO2)2]·2(DMF) (4), exhibited weak inhibitory activity (IC50>50μM). Their structure–activity relationships were further discussed.

Relation between Crystal Packing and Optical Anisotropy for Schiff Base-Nickel Complexes that Form Various Ladder-like Hydrogen-Bonding Networks

A series of nickel(II) complexes of a 2,6-dihydroxynaphtho-1-aldehyde Schiff base was synthesized. By means of in situ formation of metal-containing tectons, some of those complexes afforded sub-millimeter-scale single crystals directly from the reaction mixture. The complexes consisted in part of various ladder-like hydrogen-bonded networks, which forced the chromophore to arrange in anisotropic fashion, with the effect dependent on the length of the alkyl chains. The crystals exhibited a marked linear dichroism, and their solid-state polarization absorption spectra were recorded with an optical microscope. Using data from quantum chemical calculations and the crystal structure, we were able to elucidate the relationship between crystal packing and optical anisotropy. Analyses based on theoretical equations allowed us to explain the observed absorbance and to interpret the mechanism of the dichroism in detail.

The Interaction of Nickel(II) and Copper(II) Schiff Base Complexes with Diorganotin(IV) Dichlorides in Acetonitrile: A Thermodynamic Study

Adduct formation of nickel(II) and copper(II) Schiff base complexes, (NiL) and (CuL), as donors with diorganotin(IV) dichlorides as acceptors has been investigated spectrophotometrically, in acetonitrile. L is α,α′-Me2-salen, N,N ′-ethylenebis(α-methylsalicylideneiminate) (1), α,α′-Me2-salpn, N,N ′-1,2-propylenebis(α-methylsalicylideneiminate) (2), α,α′-Ph2-salen, N,N ′-ethylenebis(α-phenylsalicylideneiminate) (3), and α,α′-Ph2-salpn, N,N ′-1,2-propylenebis(α-phenylsalicylidene- iminate) (4). The trend of adduct formation of the nickel(II) and copper(II) Schiff base complexes with a given tin compound decreases as follows: M(α,α′-Me2-salen) > M(α,α′-Me2-salpn) > M(α,α′-Ph2-salen) > M(α,α′-Ph2-salpn). The trend of the reaction of R2SnCl2 toward a given nickel(II) or copper(II) Schiff base complex is Ph > Me > Bu. The trend of the metal reactivity in a given Schiff base toward a given diorganotin(IV)dichloride at the same temperature is Cu(II) > Ni(II).

New Acyclic Schiff-Base Nickel(II) Complexes and their Electrochemical, Kinetic, and Antimicrobial Studies

Five new nickel(II) complexes were synthesized. All the complexes were characterized by elemental and spectral analysis. Electronic spectra of the complexes show d–d transition in the range of 500–800 nm. Electrochemical studies of the complexes show an irreversible one-electron reduction process around –0.65 to –0.91 V and an irreversible one-electron oxidation process around 0.87 to 1.00 V. The reduction and oxidation potential of nickel(II) complexes shifts toward cathodic and anodic directions, respectively, upon increasing the chain length. The catalytic activity of the nickel(II) complexes on the hydrolysis of 4-nitrophenylphosphate was determined. All the nickel(II) complexes were screened for antibacterial activity.

Synthesis and characterisation of ammonium mediated assembly of two neutral nickel(II) Schiff base fragments

The 1:2 condensation of o-phenelenediamine and o-vanilline yields a compartmental N 2O 4 ligand N, N′-(1,2-Phenylene)-bis(3-methoxysalicylideneimine) [H 2L]. When nickel(II) thiocyanate is added to the methanol solution of H 2L, followed by addition of ammonium thiocyanate, an unusual nickel(II) compound, [NH 4(NiL) 2SCN]·H 2O ( 1), is separated out in which an ammonium ion is sandwiched between two neutral square planner NiL moieties. Hydrogen bonding interactions are observed among the ammonium ion, NiL moieties, the thiocyanate anion and the water of crystallization. The compound is characterized by C, H, N analysis, UV–VIS and IR spectroscopy, room temperature magnetic susceptibility measurement and X-ray crystal diffraction study. The compound crystallizes in monoclinic space group P2 1/ n with a = 13.8636(7) Å, b = 14.0267(7) Å, c = 22.2715(10) Å and β = 94.301(3)°.

Effective Oxidation of Alcohols with H5IO6 Catalyzed by Nickel(II) Schiff Base Complexes

Nickel(II)-Schiff base-triphenylphosphine complexes catalyze oxidation of alcohols to carbonyls in presence of minimum amount of periodic acid. The catalytic oxidation was developed in mild conditions and showed good yields. The effects of temperature, time, and concentrations of catalyst and co-oxidant were studied. Higher catalytic activity has been observed for NiL1 compared to the other complexes.

Hydrothermal and sonochemical synthesis of a nano-sized nickel(II) Schiff base complex as a precursor for nano-sized nickel(II) oxide; spectroscopic, catalytic and antibacterial properties

The Ni(II) complexes [Ni(L)2](ClO4)2 (1) and [Ni(L)2(NO3)2] (2), where L is the Schiff base ligand of 4,5,9,13,14-pentaaza-benzo[b] triphenylene, were synthesized and characterized by physico-chemical and spectroscopic methods. Nano-sized particles of (1) were prepared both by sonochemistry (3) and solvothermal (4) methods. NiO nanoparticles were obtained by calcination of the nano-structure complexes at 500 °C. The structures of the nano-sized compounds were characterized by X-ray powder diffraction and scanning electron microscopy. The thermal stabilities of the bulk complexes (1–2) and nano-sized particles (3–4) were studied by thermogravimetric and differential scanning calorimetry. The catalytic activities of complexes of (1–4) are reported. The free Schiff base and its Ni(II) complexes have been screened for antibacterial activities against three Gram-positive bacteria. The metal complexes are more active than the free Schiff base. Electrochemical studies show that the Ni complexes undergo irreversible reduction in MeCN solution.

Doubly Pyridazine-bridged Dicobalt(II) and Dinickel(II) Side-by-side Complexes of Variously Substituted Conjugated Bis-bidentate Ligands

A family of six acyclic bis-bidentate Schiff base ligands, Lx (prepared by condensation of 3,6-diformylpyridazine with a range of anilines: 2,4-dimethylaniline Lo,p-Me; 3,5-dichloroaniline Lm,m-Cl; 3,5-difluoroaniline Lm,m-F; p-toluidine Lp-Me; 4-aminophenol Lp-OH; 2,4,6-trimethylaniline Lo,o,p-Me), was complexed, 1:1, with cobalt(ii) or nickel(ii) perchlorate or tetrafluoroborate in refluxing dry acetonitrile. A family of dinuclear, doubly pyridazine-bridged complexes, M2II(Lx)2(solvent)n(ClO4)4 and [Ni2(Lo,o,p-Me)2(2H2O)4](BF4)4, resulted. An X-ray crystal structure determination on [Co2II(Lo,o,p)2(H2O)2(MeCN)2](ClO4)4·MeCN confirmed that it has the expected side-by-side architecture with axial solvent molecules completing the octahedral coordination sphere of the two cobalt(ii) ions. Magnetic analysis showed that the pyridazine bridges mediate weak-to-medium antiferromagnetic interactions between the metal ions. Specifically, for the cobalt(ii) complexes J was in the range –12 to –6 cm–1, while for the nickel(ii) complexes J was in the range –22 to –17 cm–1. There is no clear cut correlation of J values with electron-donating or -attracting properties of ligand substituent peripheral groups, although it is noted that the smallest J occurs in both the NiNi and CoCo families for the ligand Lo,o,p-Me.

Catalytic oxidation of alcohols by nickel(II) Schiff base complexes containing triphenylphosphine in ionic liquid: An attempt towards green oxidation process

Abstract A series of square planar nickel(II) complexes containing N,O donor Schiff base ligand, i.e. N-(2-pyridyl)-N′-(5-substituted-salicylidene)hydrazine and triphenylphosphine, have been synthesized and characterized by analytical and spectral methods. Catalytic activities of all the complexes have been studied for the oxidation of alcohols in ionic liquid media using NaOCl as oxidant.

Synthesis, Characterization, and Crystal Structure of an Azido-bridged Dinuclear Nickel(II) Complex Derived from 4-Nitro-2-[(2-isopropylaminoethylimino)methyl]phenol

An azido-bridged dinuclear Schiff base nickel(II) complex with the formula [Ni 2 L 2 (N 3 ) 2 ( μ 1,1 -N 3 ) 2 ] (HL = 4-nitro-2-[(2-isopropylaminoethylimino)methyl]phenol) was prepared and structurally characterized by elemental analysis, IR spectrum and single crystal X-ray diffraction. The structure has a crystallographic inversion center at the midpoint of the two nickel atoms. Each NiII atom in the complex is in an octahedral coordination. The molecules in the crystal are linked through the intermolecular hydrogen bonds of N–H···O, C–H···O, and C–H···N, forming layers.

Application of nickel‐catalysed reduction and azo dye reactions for the determination of tinidazole

A macrocyclic Schiff base nickel(ii) complex was synthesised via template synthesis by treating acetylacetone with 1,8-diaminonaphthalene in the presence of nickel chloride in a 2:2:1 ratio in an aqueous methanol solution at 75 °C for 30 min. It was characterised by elemental, infrared, proton and carbon nuclear magnetic resonance and mass spectral analysis and used as a catalyst for the reduction of tinidazole. The reduced tinidazole was treated with nitrous acid and 2-naphthol and the resulting azo dye was used for the spectrophotometric determination of the reduction product of tinidazole.

Bisphosphine‐Functionalized Cyclic Decapeptides Based on the Natural Product Gramicidin S: A Potential Scaffold for Transition‐Metal Coordination

The natural product Gramicidin S is a promising scaffold for novel oligopeptide-based bisphosphine ligands, combining the advantageous rigid chiral backbone with the close proximity of phosphine substituents. The required unnatural, phosphine-containing, amino acid building blocks were synthesized by means of a novel protocol that involves the enantioselective alkylation of a chiral nickel Schiff base template. Three Ni complexes were prepared with different alkyl chains between the phosphine group and the alpha-carbon atom of the incorporated glycine; the absolute stereochemistry of two of them was determined by single-crystal X-ray structure analysis. By detaching the template, enantiopure L-phosphine amino acids resulted enabling the solid-phase, stepwise construction of a linear sequence of the phosphine-modified oligopeptides. On cyclization three bisphosphine-substituted Gramicidin S analogues resulted, differing only in the size and shape of the linkage between the phosphine groups and the oligopeptides backbone. Their crystal structures suggest these species to have potential as chelating ligands.