Pyrazolate-based copper(II) and nickel(II) [2 x 2] grid complexes: protonation-dependent self-assembly, structures and properties

The pyrazole-based diamide ligand N,N'-bis(2-pyridylmethyl)pyrazole-3,5-dicarboxamide (H(3)L) has been structurally characterised and successfully employed in the preparation of [2 x 2] grid-type complexes. Thus, the reaction of H(3)L with Cu(ClO(4))2.6H(2)O or Ni(ClO(4))2.6H(2)O in the presence of added base (NaOH) affords the tetranuclear complexes [M(4)(HL(4))].8H(2)O (1: M = Cu, 2: M = Ni). Employment of a mixture of the two metal salts under otherwise identical reaction conditions leads to the formation of the mixed-metal species [Cu(x)Ni(4-x)(HL)(4)].8H(2)O (x相似文献   

Theoretical investigation on molecular structure of a new mononuclear copper(II) thiocyanato complex with tridentate Schiff base ligand

An asymmetrical Schiff base ligand, 4-bromo-2-(2-pyridylmethyliminomethyl)phenol (HL), and its copper(II) complex, [Cu(L)SCN] (1), have been synthesized. Complex 1 is experimentally characterized by elemental analysis, FT-IR and UV–vis spectroscopic techniques, and cyclic voltammetry. The structure of the complex has been established by single-crystal X-ray diffraction studies, which reveal a square planar geometry of the central copper(II) ion in 1. The neighboring molecules of the complex connect each other by π–π stacking interactions with centroid-to-centroid ring distance 3.653 Å. The ligand can display two possible tautomeric forms; therefore, 1 can have an alternate molecular structure. DFT calculations have been employed to investigate the structure and relative stabilities of the suggested tautomeric forms of the ligand and its corresponding copper(II) complex.     

Synthesis,crystal structure and antibacterial activity of four mononuclear Schiff base complexes of copper(II) and nickel(II)

Transition Metal Chemistry - Three mononuclear copper(II) complexes, viz. [CuL1] (1), [CuL2] (2), [CuL3] (3), and one nickel(II) complex, viz.[NiL3] (4) where...     

Metal complexes with thioether containing unsymmetrical N2S donor Schiff base ligand: Crystal and molecular structure of nickel(II) complex

Abstract

A thioether unsymmetrical N₂S donor Schiff base ligand, N-2-((2-nitrophenyl)thio)phenyl)-1-(pyrrole-2-yl)methanimine (HL) and its five complexes [NiL₂], [CuL₂], [ZnHL(H₂O)₂(OAc)₂], [CdHL(H₂O)₂(OAc)₂]·2H₂O and [MnHL(H₂O)₂(OAc)₂]·2H₂O were synthesized. The ligand and metal complexes were characterized by spectroscopic methods (FT-IR, ¹H and ¹³C NMR, UV–Vis), elemental analyses, mass spectrometry, and conductance measurements. Of these complexes, [NiL₂] was structurally characterized by single-crystal X-ray crystallography. In this complex, two ligands function as monobasic N₂S tridentate and coordinate through pyrrole-N, thioether-S, and azomethine-N, and the nickel(II) is in distorted octahedral environments.     

Synthesis, characterization, and X-ray crystal structures of copper(II) and nickel(II) complexes with Schiff base

New copper(II) complexes, [Cu₂L¹L²] · ClO₄ (I) and [Ni(L³)₂] (II), where L¹ is the monoanionic form of 2-[1-(2-emthylaminoethylimino)ethyl]phenol, L² is the dianionic form of N,N′-ethylene-bis(2-hydroxyacetophenonylideneimine), L³ is the mono-anionic form of 2-(1-iminoethyl)phenol, were prepared and characterized using elemental analysis, FT-IR spectroscopy, and X-ray single-crystal diffraction. In complex I, the Cu(1) atom is coordinated by the NNO tridentate ligand L¹ and the two phenolate O atoms of L², forming a square pyramidal geometry. The Cu(2) atom in complex I is coordinated by the NNOO tetradenate ligand L², forming a square planar geometry. The Ni atom in complex II is coordinated by two phenolate O and two imine N atoms from two ligands L³, forming a square planar geometry. In the crystal structure of I, the perchlorate anions are linked to the dinuclear copper(II) complex cations through intermolecular N-H...O hydrogen bonds. In the crystal structure of II, the mononuclear nickel complex molecules are linked through intermolecular N-H...O hydrogen bonds, forming a trimer.     

Electrochemical behaviour of the complexes of copper(II) with a Schiff base compartmental ligand

Summary The ethylenediamine Schiff base derivative ofo-acetoacetylphenol, H₄aapen, is a ligand able to form both mononuclear and dinuclear complexes with copper(II) ion. Mononuclear positional isomers can be obtained, having the copper in the O₂O₂ site and in the N₂O₂ site. The electrochemistry of these copper(II) complexes in dimethylsulfoxide shows that the two positional isomers are reduced at different potentials through an e.c.e. mechanism, in which a chemical reaction is coupled between two one-electron transfers, the N₂O₂ isomer being the less reducible. They also undergo complicated oxidation processes at high potentials, less significant in distinguishing the two isomers. The electrochemical behaviour of the dinuclear copper(II) complex parallels that of the two mononuclear isomers.     

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.     

Synthesis,crystal structures and yeast RNA-binding properties of copper(II) and nickel(II) complexes with a bidentate Schiff base

Abstract  

Trans-CuL₂ and cis-NiL₂ (L = 1-((furan-2-yl)methylene)-4-phenylthiosemicarbazide) were synthesized and characterized by physico-chemical and spectroscopic methods. Their X-ray crystal structures were determined. The complexes contain the same bidentate Schiff base ligand, but with different cis-NiN₂S₂ and trans-CuN₂S₂ square-planar coordination geometries. Three-dimensional supramolecular networks were formed through “face to face” π–π conjugated systems between phenyl and furan rings. The interactions with yeast RNA (yRNA) were investigated by UV spectra and electrochemical methods, which showed that the complexes intercalated into yRNA. The bonding of trans-CuL₂ to yRNA is the stronger of the two, suggesting that the trans geometry is more favorable for interaction with RNA.     

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.     

Synthesis and crystal structure of a new Schiff base ligand and its cobalt(II) complex

The crystal structures of cobalt(II) Schiff base complex (Co^IIL₂ · H₂O) and Schiff base ligand 3,5-dichlorosalicylidene-2-chlorophenylmethylamine (HL) have been determined by single-crystal X-ray analysis. The geometry around cobalt in Co^IIL₂ · H₂O is distorted tetrahedral. Co^IIL₂ · H₂O crystallizes in the monoclinic system, in space group C2/c, with crystallographic parameters: a = 12.9143(16) Å, b = 8.8326(16) Å, c = 25.115(3) Å, β = 92.791(10)°, V = 2861.4(7) ų, Z = 4, F(000) = 1420, and the final R indices (I > 2σ(I)) are R ₁ = 0.0440, wR ₂ = 0.1272. HL crystallizes in the monoclinic system, in space group P2₁/c, with crystallographic parameters: a = 11.9764(15), b = 8.2331(10), c = 14.2211(17) Å, β = 98.723(6)°, V = 1386.0(3) ų, Z = 4, F(000) = 640, and the final R indices (I > 2σ(I)) are R ₁ = 0.0397, wR ₂ = 0.1018.     

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.     

Synthesis and crystal structure of a new nickel(II) coordination polymer based on Schiff base

A new Schiff base coordination polymer, [Ni(C₁₈H₁₆N₃O₂)₂ · 2CH₃OH] _n (C₁₈H₁₆N₃O₂, 2-acetylpyridine-L-tryptophan), was synthesized and characterized by IR, UV, and X-ray diffraction singlecrystal analysis. The crystal crystallizes in the tetragonal crystal system, space group P4₃2₁2 with cell parameters a = 11.8912(11), c = 28.822(3) ?, V = 4075.5(6) ?³, Z = 4, F(000) = 1544, S = 1.187, ??_calcd = 1.199 g cm^?3, ?? = 0.525 mm^?1, the final R ₁ = 0.0515 and wR ₂ = 0.1513 for 3602 observed reflections (I > 2??(I)). The Ni(II) atom is six-coordinated by two nitrogen atoms from C=N, two nitrogen atoms from pyridine rings and two carboxylic oxygen atoms in different ligands, forming a distorted octahedron geometry. Each ligand serves as a bridging ligand to link Ni²⁺ ions through carboxylic oxygen atoms, leading to a two-dimensional coordination polymer.     

Synthesis and characterization of a thioether Schiff base ligand and its metal complexes and crystal structure determination of the nickel(II) complex

Reactions of 1,2-di(o-aminophenylthio)ethane with 3-ethoxy-2-hydroxybenzaldehyde yield the new hexadentate N₂S₂O₂ donor thioether Schiff base 1,2-bis(2-((2-(thio)phenylimino)methyl)-6-ethoxyphenol)ethane (H₂L). Ni(II), Zn(II), Cd(II), and Hg(II) complexes of this ligand were prepared. Of these complexes, [NiL]·2H₂O has been structurally characterized by X-ray crystallography. The coordination geometry around Ni(II) was described as octahedral. Zn(II), Cd(II), and Hg(II) complexes and the Schiff base ligand have been characterized by CHN analyses, molar conductivity, UV–vis, FT-IR, ¹H, and ¹³C NMR spectroscopy.     

The chiral helical structure of a copper(II) complex with a tridentate Schiff base ligand

In the title salt, catena‐poly[[[aquacopper(II)]‐μ‐3‐(2‐pyridylmethyleneamino)propanoato‐κ⁴N,N′,O:O′] perchlorate], {[Cu(C₉H₉N₂O₂)(H₂O)]ClO₄}_n, the monomeric unit contains a square‐based pyramidal Cu^II centre. The four basal positions are occupied by a tridentate anionic Schiff base ligand which furnishes an NNO‐donor set, with the fourth basal position being occupied by an O‐donor atom from the carboxylate group of an adjacent Schiff base ligand. The coordination sphere is completed by a water molecule at the apical position. Interestingly, each carboxylate group in the ligand forms a syn–anti‐configured bridge between two Cu^II centres, leading to left‐handed chiral helicity. The framework also exhibits O—H...O hydrogen bonds involving the water molecules and an O atom of the perchlorate anion.     

Nickel versus copper: enhanced antibacterial activity in a series of new nickel(II) Schiff base complexes

Five new Ni(II) Schiff base complexes [NiL^x(Solv)₂] denoted by NiL^x, x = 1–5, were synthesized and characterized. The Schiff base ligands were synthesized from the condensation of 5-bromo-2-hydroxy-3-nitrobenzaldehyde with different aliphatic and aromatic diamines. The X-ray crystal structure of NiL³ was determined. The ligands and complexes were tested as antibacterial agents against two gram(+) and two gram(?) human pathogenic bacteria. The complexes showed moderate antibacterial activity against both gram type bacteria. The new Ni(II) complexes showed enhanced antibacterial activity compared to the previously reported Cu(II) complexes of the same ligands.     

Synthesis,crystal structure,and antibacterial activity of two new mononuclear nickel(II) complexes of a NNS Schiff base

Two new mononuclear nickel(II) complexes, [Ni(L)(N₃)] (1) and [Ni(L)₂(NCS)₂] (2), where HL = 2-{[phenyl(pyridin-2-yl)methylidene]amino}benzenethiol, a tridentate Schiff base derived from 2-aminothiophenol and 2-benzoylpyridine, have been prepared and characterized. The syntheses of 1 and 2 have been achieved by the reaction of equimolar amounts of nickel perchlorate and HL in the presence of azide and thiocyanate, respectively. The complexes have been characterized by microanalytical, spectroscopic, single-crystal X-ray diffraction, and other physicochemical studies. Structural studies reveal that 1 and 2 adopt two different geometries, distorted square planar in 1 and octahedral in 2. The two mononuclear complex units are held together by π…π or C–H…π weak intermolecular interactions to develop supramolecular networks in their solid states. The antibacterial activity of 1, 2 and their constituent Schiff base has been tested against some gram(+) and gram(?) bacteria.     

Synthesis and spectroscopic characterization of copper(II) complexes with the polydentate chelating ligand 4,4'-[1,4-phenylenedi(nitrilo)dipente-2-one

A new series of complexes of 4,4'-[1,4-phenylenenedi(nitilo)]dipenten-2-one, (H(2)L) with CuX(2) x nH(2)O, X = Cl, Br, ClO(4), NO(3) and OAc; n = 1-6 as well as their ethylenediamine adducts have been synthesized and characterized by different physical techniques. The formulation of the complexes is assumed based on their elemental analysis and the molar conductivity. The products are found to be pH-dependent. The IR data showed that the ligand acts as dibasic tetradentate coordinated to copper(II) ions through the enolato-oxygen and the azomethine nitrogen atoms. Electronic, ESR spectra and room temperature magnetic moments indicate that complexes 1-9 are square planar while complexes 10 and 11 are square based pyramidal. The different electronic spectral and ESR parameters are calculated and used to describe the nature of ligand-metal bonding (sigma and pi) as well as to estimate the extent of distortion. A macrocyclic containing copper(II) complex, 12 have been isolated by the reaction of Schiff-base with copper(II)-ethylenediamine mixture. The ligand (H(2)L) is designed as a building block for larger molecules and superamolecular assemblies.     

Three heterotrinuclear Schiff base complexes of nickel(II) with cobalt(II), copper(II) and manganese(II)

The title compounds, bis­(di­methyl­form­amide)‐1κO,3κO‐bis{μ‐2,2′‐[2,2′‐di­methyl­propane‐1,3‐diyl­bis­(nitrilo­methylidyne)]­diphenolato}‐1κ⁴N,N′,O,O′:2κ²O,O′;2κ²O,O′:3κ⁴N,N′,O,O′‐di‐μ‐nitrito‐1:2κ²N:O;2:3κ²O:N‐dinickel(II)­cobalt(II), [CoNi₂(NO₂)₂(C₁₉H₂₂N₂O₂)₂(C₃H₇NO)₂], (I), ‐copper(II), [CuNi₂(NO₂)₂(C₁₉H₂₂N₂O₂)₂(C₃H₇NO)₂], (II), and ‐manganese(II), [MnNi₂(NO₂)₂(C₁₉H₂₂N₂O₂)₂(C₃H₇NO)₂], (III), consist of centrosymmetric linear heterotrinuclear metal complexes. The three complexes are isostructural. There are three bridges across the Ni–M atom pairs (M is Co²⁺, Cu²⁺ or Mn²⁺) in each complex, involving two O atoms of a μ‐N,N′‐bis­(salicyl­idene)‐2,2′di­methyl‐1,3‐propane­diaminate ligand and an N—O moiety of a μ‐nitrito group. The coordination sphere around each metal atom, whether Co²⁺, Cu²⁺, Mn²⁺ or Ni²⁺, can be described as distorted octahedral. The Ni?M distances are 2.9988 (5) Å in (I), 2.9872 (5) Å in (II) and 3.0624 (8) Å in (III).     

Homogeneous and heterogeneous styrene epoxidation catalyzed by copper(II) and nickel(II) Schiff base complexes

Both monomeric Schiff base complexes and 1D helical polymeric complexes of Cu(II) and Ni(II) were synthesized and characterized by physicochemical and spectroscopic methods. X-ray single-crystal studies were made on [K₂(CuL)₂Ni(CN)₄]_n·0.5nEt₂O and [K₂(NiL)₂Ni(CN)₄]_n·0.5nEt₂O. The polymers were screened as heterogeneous catalysts for styrene epoxidation. For comparison, the catalytic properties of the homogeneous and heterogeneous catalysts were also examined under identical reaction conditions, and the influence of various solvents and oxidants was studied. The polymeric catalysts showed better activities in chloroform when using tert-butyl hydroperoxide as oxidant, suggesting that heterogenization increased the activity of the catalyst under this condition.