Ligational behavior of a bidentate coumarin derivative towards CoII,NiII, and CuII: synthesis,characterization, electrochemistry,and antimicrobial studies

A series of new Co(II), Ni(II), and Cu(II) complexes of Schiff base derived from coumarin have been prepared and characterized by analytical and spectral methods. The Schiff base is synthesized by the condensation of 2,6-diaminopyridine and 3-acetylcoumarin in 1 : 1 stoichiometric ratio. All complexes have 1 : 1 metal : ligand ratio except the nickel complex, where it was found to be 1 : 2. UV-Vis spectra and magnetic moment studies confirm the existence of tetrahedral and octahedral geometries around cobalt(II) and nickel(II) metal ions, respectively, but copper(II) chloride/nitrate/sulfate complexes have square-planar geometry and copper(II) acetate complex is distorted octahedral. ESR spectra of copper complexes at room temperature and liquid nitrogen temperature were tetragonal. All the complexes were found to be more active against bacteria except Ni(II) complex; only CuLSO₄ and CuL(CH₃COO)₂ have shown the enhanced activity against fungi.     

Nickel(II) complexes chelated by 2-quinoxalinyl-6-iminopyridines: Synthesis, crystal structures and ethylene oligomerization

A series of nickel(II) complexes ligated by tridentate ligands of 2-quinoxalinyl-6-iminopyridines was synthesized and characterized by elemental and spectroscopic analysis as well X-ray diffraction analysis. X-ray crystallographic analysis revealed the nickel complexes as five-coordinated distorted trigonal bipyramidal geometry. In the presence of Et₂AlCl, these complexes displayed high catalytic activity for ethylene oligomerization and the dimmers were produced as main products. The nickel dibromide complexes exhibited relative higher activity than their dichloride analogues. Both elevation of the ethylene pressure and addition of auxiliary ligand have catalytic enhancement effects on all the complexes.     

Synthesis,Characterization, and DNA Binding Studies of a Nickel(II) Complex Containing the 1,3‐Bis(1‐propylbenzimidazol‐2‐yl)‐2‐oxapropane

A complex of formula [Ni(pobb)₂](pic)₂, (pobb = 1,3‐bis(1‐propylbenzimidazol‐2‐yl)‐2‐oxapropane, pic = 2,4,6‐trinitrophenol), has been synthesized and structurally characterized by physico‐chemical and spectroscopic methods. The crystals crystallize in the monoclinic system, space group C2/c, a = 25.766(11) Å, b = 14.943(7) Å, c = 19.543(14) Å, α = 90°, β = 129.722(4)°, γ = 90°, Z = 4. The coordination environment around nickel(II) atom can be described as a distorted octahedral geometry. The interactions of the ligand pobb and the nickel (II) complex with calf thymus DNA (CT‐DNA) are investigated by using electronic absorption titration, ethidium bromide‐DNA displacement experiments and viscosity measurements. The experimental evidence indicated the compounds interact with calf thymus DNA through intercalation.     

Polymeric and monomeric dipicolinate complexes with 4-hydroxymethyl pyridine: spectral, structural, thermal and electrochemical characterization

Polymeric copper(II), [Cu(μ-dpc)(μ-4-hymp)] _n (1), and monomeric nickel(II), [Ni(dpc)(4-hymp)(H₂O)₂]·H₂O (2), (dpc: dipicolinate, 4-hymp: 4-hydroxymethyl pyridine), dipicolinate complexes have been prepared and characterized by spectroscopic (IR, UV–Vis, EPR), thermal (TG/DTA), X-ray diffraction technique and electrochemical methods. In both the dipicolinate complexes, the dpc dianion acts as a tridentate ligand. In polymeric copper(II) complex, the 4-hymp and dpc ligands adopt a bridging position between the Cu(II) centers, forming the elongated octahedral geometry. The polymeric chains are linked to one another via O–H···O hydrogen bond interactions, forming the 3-D polymeric structure. The Ni(II) ion is bonded to dpc ligand through pyridine N atom together with one O atom of each carboxylate group, two aqua ligands and N pyridine atom of 4-hymp, forming the distorted octahedral geometry. The Ni(II) complexes are connected to one another via O–H···O hydrogen bonds, forming R ₄²(18) motifs in 2-D pattern. The powder EPR spectra of copper(II) complex have indicated that the paramagnetic center is in rhombic symmetry with the Cu²⁺ ion having distorted octahedral geometry. IR and UV–Vis spectroscopes all agree with the observed crystal structure.     

Synthesis,Crystal Structure,and Catalytic Performance of 2,6-Bis[1-（2,4,6-trimethylphenylimino）ethyl]pyridine Nickel（II） Complex

A novel nickel（II）-complex Ni[L]Cl2-CH3CN（1） containing the tridentate ligand 2,6-bis[1-（2,4,6- trimethylphenylimino）ethyl]pyridine（L） has been synthesized. The crystal structure of complex 1 was determined by single crystal X-ray diffraction analysis. The catalytic activity of complex 1 for the polymerization of ethylene was studied under activation with methylaluminoxane（MAO）.     

Synthesis and structure of the disc-like cluster C72H102N12Ni13O40

The disc-like cluster C₇₂H₁₀₂N₁₂Ni₁₃O₄₀ is first time synthesized based on N-(2-pyridyl)methyliminodipropionic acid. Single crystal X-ray diffraction is used to determine its atomic structure. The cluster consists of seven-nuclear core: nickel(II) hydrocomplex (Ni...Ni distance 3.012–3.032 Å) and six nickel chelates of the corresponding acid arranged around its perimeter (Ni...Ni distance 2.981–3.164 Å). In the chelate part of the complex, the ligand is pentadentate owing to the formation of a bridging bond, thus organizing a coordination geometry of the metal center as a distorted square bipyramid (4+2). Liquid chromatography-mass spectrometry is employed to study the structure of the obtained nickel(II) complexes.     

Spectroscopic,structural and magnetic studies of nickel(II) complexes with tetra- and pentadentate ligands

Abstract  Two new nickel(II) complexes, namely [Ni(BPSE)](BF₄) 1, and [Ni (5-BST)CH₃OH]ClO₄ 2 [BPSE = 2-benzoylpyridinesalicylidene ethylenediamine, 5-BST = 5-bromosalicylidene-tris(2-aminoethyl)amine] have been synthesized and characterized using various physico-chemical methods. The magnetic and spectroscopic data indicate a distorted square planar geometry for complex 1, while complex 2 is assigned a distorted octahedral geometry. Complex 1 crystallized in the triclinic space group P-1. Complex 2 adopts an octahedral geometry with space group symmetry P 21/n. The superoxide dismutase activity of these complexes has been measured. Graphical Abstract  This paper describes three new nickel (II) complexes viz; [Ni(BPSE)](BF4) 1, [Ni(BSE)] 2 and [Ni (5-BST) CH3OH] ClO4 3 [BPSE = 2-benzoylpyridine salicyledene-ethylenediamine, BSE = bis(salicylaldehyde) ethylenediamine, 5-BST = 5-bromosalicyledene-tris(2-amino ethyl) amine]. The magnetic and spectroscopic data indicate a distorted square planar geometry for complex 1 and 2, while the comlplex 3 is assigned a distorted octahedral geometry. Superoxide dismutase activity of these complexes have also been measured. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Nickel(II), copper(II), and cobalt(II) complexes derived from a new unsymmetrical ONS donor Schiff base ligand: synthesis,characterization, crystal structure,and catalytic activities

Ni(II), Cu(II), and Co(II) complexes, ML₂, with a new thioether containing ONS donors were synthesized, where L = deprotonated Schiff base. The analytical, spectral (FTIR, ¹H NMR, and UV-vis), conductivity, and magnetic studies show that the metal complexes possess octahedral geometry and are non-electrolytes. The coordination mode of ligand, 1, and nickel(II) complex, NiL₂, 2, was determined by single-crystal X-ray diffraction studies. Here, the nickel is coordinated to two oxygens, two nitrogens, and two sulfurs of two tridentate ligands with slightly distorted octahedral environment around nickel. The copper complex shows very good catalytic activities towards oxidation of organic thioethers to the corresponding sulfoxide predominantly using H₂O₂ as the oxidant.     

Synthesis,structural characterization and biological evaluation of mononuclear transition metal complexes of zwitterionic dehydroacetic acid N‐aroylhydrazone ligand

Synthesis and characterization of mononuclear transition metal complexes viz., Co(II), Ni(II), Cu(II) and Zn(II) with a newly designed ligand, (E)‐2‐benzamido‐N'‐(1‐(2‐hydroxy‐6‐methyl‐4‐oxo‐4H‐pyran‐3‐yl) ethylidene) benzohydrazide ( H ₂ L ) are reported. Molecular structures of H ₂ L , Ni(II) and Cu(II) complexes were determined by single‐crystal X‐ray diffraction studies. The structures were stabilized by various intra/inter‐molecular H‐bonding, C‐H···π and π···π stacking interactions. H ₂ L exists in zwitterionic form and acts in a monoanionic manner. Ligand/metal ratio was 2:1 for cobalt, nickel and zinc, whereas 1:1 for the copper complex. Co(II), Ni(II) and Zn(II) complexes display distorted octahedral geometry, while the Cu(II) complex shows distorted square pyramidal geometry around the metal ion. Hirshfeld surface analysis and 2D fingerprint plots revealed that H ₂ L and its complexes were supported mainly by H?H, O?H and C?H intermolecular interactions. The synthesized compounds were screened for in vitro anti‐inflammatory activity by gelatin zymography and the activity was comparable with tetracycline. Their cleavage behavior towards calf thymus DNA has been studied using agarose gel electrophoresis method. H ₂ L and Cu(II) complex were selected by National Cancer Institute (NCI) for in vitro single dose testing in the full NCI 60 cell lines panel assay. Finally, molecular docking simulation effectively proves the binding of all the synthesized compounds at cyclooxygenase‐2 (COX‐2) active sites.     

New anilinotropone-based titanium complexes: synthesis, characterization and application as catalysts for olefin polymerization

New titanium(IV) dichloride complexes containing 2-anilinotropone ligands have been synthesized and characterized. Bis(ligand)titanium dichloride complexes 1 and 2 were synthesized from reaction of TiCl4(THF)2 with 2 equivalents of the corresponding sodium salts of 2-(2,6-diisopropylanilino)tropone (L1) and 2-(2,3,4,5,6-pentafluoroanilino)tropone (L2), respectively. The mixed cyclopentadienyl-anilinotropone compound 3 was synthesized by reaction of the lithium salt of with CpTiCl3. The Cp-mixed micro-O bimetallic complex 4 was also isolated as a by-product owing to the adventitious presence of moisture. The molecular structures 1-4 of have been determined by single-crystal X-ray diffraction studies. Complexes 1 and 2 are isostructural and exhibit a C2-symmetric octahedral geometry, with a trans(N,N), cis(O,O) arrangement in complex 1, but with a trans(O,O), cis(N,N) arrangement in complex 2. The Cp-mixed complex 3 has a distorted square-pyramidal structure with the Cp ligand in the apical position. Bimetallic complex 4 shows a similar coordination geometry for the five-coordinate titanium atom and a pseudo-tetrahedral coordination for the second metallic centre. All new complexes, when activated with methylaluminoxane, are active in the polymerization of ethylene and propene.     

Nickel complexes bearing 2-(1H-benzimidazol-2-yl)-phenoxy ligands: Synthesis, characterization and ethylene oligomerization

A series of 2-(1H-benzimidazol-2-yl)-phenols and their nickel complexes have been synthesized and characterized by elemental and spectroscopic analysis. The molecular structures of ligand L4 and complex C5 were confirmed by X-ray diffraction analysis. X-ray crystallographic analysis revealed that complex C5 has a six-coordinated distorted octahedral geometry. Upon activation with Et₂AlCl, these nickel(II) complexes showed good activity for ethylene oligomerization. When PPh₃ was added as an auxiliary ligand to the catalytic system, an increased activity as high as 1.60 × 10⁷ g mol⁻¹ (Ni) h⁻¹ was observed. The ligand environment and reaction conditions remarkably affected the catalytic behavior of these nickel complexes.     

Cobalt(II), nickel(II), copper(II), and zinc(II) complexes with [3(5)]adamanzane, 1,5,9,13-tetraazabicyclo[7.7.3]nonadecane, and [(2.3)(2).2(1)] adamanzane, 1,5,9,12-tetraazabicyclo[7.5.2]hexadecane

Isolation of the free bicyclic tetraamine, [3(5)]adamanzane.H(2)O (1,5,9,13-tetraazabicyclo[7.7.3]nonadecane.H(2)O), is reported along with the synthesis and characterization of a copper(II) complex of the smaller macrocycle [(2.3)(2).2(1)]adamanzane (1,5,9,12-tetraazabicyclo[7.5.2]hexadecane) and of three cobalt(II), four nickel(II), one copper(II), and two zinc(II) complexes with [3(5)]adamanzane. For nine of these compounds (2-8, 10b, and 12) the single-crystal X-ray structures were determined. The coordination geometry around the metal ion is square pyramidal in [Cu([(2.3)(2).2(1)]adz)Br]ClO(4) (2) and trigonal bipyramidal in the isostructural structures [Cu([3(5)]adz)Br]Br (3), [Ni([3(5)]adz)Cl]Cl (5), [Ni([3(5)]adz)Br]Br (6), and [Co([3(5)]adz)Cl]Cl (8). In [Ni([3(5)]adz)(NO(3))]NO(3) (4) and [Ni([3(5)]adz)(ClO(4))]ClO(4) (7) the coordination geometry around nickel(II) is a distorted octahedron with the inorganic ligands at cis positions. The coordination polyhedron around the metal ion in [Co([3(5)]adz)][ZnCl(4)] (10b) and [Zn([3(5)]adz)][ZnCl(4)] (12) is a slightly distorted tetrahedron. Anation equilibrium constants were determined spectrophotometrically for complexes 2-6 at 25 and 40 degrees C and fall in the region 2-10 M(-1) for the halide complexes and 30-65 M(-1) for the nickel(II) nitrate complex (4). Rate constants for the dissociation of the macrocyclic ligand from the metal ions in 5 M HCl were determined for complexes 2, 3, 5, 8, 10, and 12. The reaction rates vary from half-lives at 40 degrees C of 14 min for the dissociation of the Zn([3(5)]adz)(2+) complex (12) to 14-15 months for the Ni([3(5)]adz)Cl(+) ion (5).     

New dinuclear nickel(II) complexes: synthesis, structure, electrochemical, and magnetic properties

The reaction of [NiBr(2)(bpy)(2)] (bpy = 2,2'-bipyridine) with organic phosphinic acids ArP(O)(OH)H [Ar = Ph, 2,4,6-trimethylphenyl (Mes), 9-anthryl (Ant)] leads to the formation of binuclear nickel(II) complexes with bridging ArP(H)O(2)(-) ligands. Crystal structures of the binuclear complexes [Ni(2)(μ-O(2)P(H)Ar)(2)(bpy)(4)]Br(2) (Ar = Ph, Mes, Ant) have been determined. In each structure, the metal ions have distorted octahedral coordination and are doubly bridged by two arylphosphinato ligands. Magnetic susceptibility measurements have shown that these complexes display strong antiferromagnetic coupling between the two nickel atoms at low temperatures, apparently similar to binuclear nickel(II) complexes with bridging carboxylato ligands. Cyclic voltammetry and in situ EPR spectroelectrochemistry show that these complexes can be electrochemically reduced and oxidized with the formation of Ni(I),Ni(0)/Ni(III) derivatives.     

Hydrothermal syntheses and crystal structures of two Zn(II) complexes with 1-substituted-1H-[1,2,3]-triazole-4-carboxylic acid

Two new Zn(II) complexes, [Zn(L)₂(H₂O)₂] where L is 1-substituted 5-methyl-1H-[1,2,3]-triazole-4-carboxylic acid, have been synthesized and characterized by elemental analysis, FT–IR, and solid-state fluorescent emission spectroscopy. Structures have been established by single-crystal X-ray diffraction, revealing the discrete nature of the complexes in which Zn centers adopt slightly distorted octahedral geometry. In the complexes, the 1-substituted 5-methyl-1H-[1,2,3]-triazole-4-carboxylic acid is bidentate.     

Synthesis, spectral characterization, and structural investigation of mononuclear salen-type Cu(II) and Zn(II) complexes of a potentially octadentate N2O6 Schiff base ligand derived from binaphthol

A new potentially octadentate N₂O₆ Schiff base ligand, H₂L derived from the condensation of 2,2′-(1,1′-binaphthyl-2,2′-diylbis(oxy))dianiline and o-vanillin, along with its copper(II) and zinc(II) complexes, is synthesized and has been characterized by elemental analyses, IR, UV–vis, ¹H and ¹³C NMR spectra, as well as conductivity measurements. H₂L forms mononuclear complexes of 1:1 (metal:ligand) stoichiometry with Cu(II) and Zn(II), and conductivity data confirm the non-electrolyte nature of these complexes. The [ZnL] and [CuL] complexes display very different solid-state structures, as determined by X-ray crystallography. While the [ZnL] complex has a distorted octahedral geometry about the metal, the [CuL] complex displays a distorted square planar geometry about the copper, with long Cu–O(ether) distances of 2.667 Å.     

Synthesis and spectral studies on Ni(II) complexes involving N-furfuryl-N-substituted benzyldithiocarbamates and PPh3: Anagostic and C–H…π(chelate) interactions in (N-furfuryl-N-(4-fluorobenzyl)dithiocarbamato-S,S′)(thiocyanato-N)(triphenylphosphine)nickel(II)

Twelve new nickel(II) complexes of functionalized dithiocarabamates [Ni(S₂CNRR')₂](1-6) and [Ni(S₂CNRR')(NCS)(PPh₃)](7-12) [where R=furfuryl; R'=2-hydroxy benzyl (1,7), 3-hydroxy benzyl (2,8), 4-hydroxy benzyl (3,9), 4-methoxy benzyl (4,10), 4-fluoro benzyl (5,11), 4-chloro benzyl (6,12)] have been prepared and characterized by elemental analysis, IR, UV-Vis and NMR (¹H and ¹³C) spectroscopy. IR spectra of the complexes support the bidentate coordination of dithiocarbamate ligands. Electronic spectral studies on complexes 1-12 indicate square planar geometry around the nickel(II) central atom. In the ¹³C NMR spectra, the upfield shift of NCS₂ carbon signal for heteroleptic complex (7-12) compared to homoleptic complexes (1-6) is due to the effect of PPh₃ on the mesomeric drift of electron density toward nickel through thioureide C-N bond. Single crystal X-ray structural analysis of complex 11 confirms that the coordination geometry about the Ni(II) is distorted square planar. A rare intramolecular anagostic interaction C–H^…Ni [Ni???H=2.804 Å] is observed. The packing of complex 11 is stabilized by non-conventional C–H^…S, C–H?F and C–H?π(chelate, NiS₂C) bonding interactions.     

2-Acetyloxymethyl-substituted 5,6,7-trihydroquinolinyl-8-ylideneamine-Ni(II) chlorides and their application in ethylene dimerization/trimerization

Six examples of 2-acetyloxymethyl-substituted 5,6,7-trihydroquinolinyl-8-ylideneamine-nickel(II) chlorides, [2-(CH₂OC(O)Me)-8-{N(Ar)}C₉H₈N]NiCl₂ (Ar = 2,6-Me₂C₆H₃ Ni1 , 2,6-Et₂C₆H₃ Ni2 , 2,6-i-Pr₂C₆H₃ Ni3 , 2,4,6-Me₃C₆H₂ Ni4 , 2,6-Et₂–4-MeC₆H₂ Ni5 , 2,4,6-t-Bu₃C₆H₂ Ni6 ), have been prepared by a one-pot template reaction of 2-(hydroxymethyl)-6,7-dihydroquinolin-8(5H)-one with nickel dichloride hexahydrate, the corresponding aniline and acetic acid. All complexes were characterized by elemental analysis and IR spectroscopy, while dinuclear Ni2 and mononuclear Ni3 ·OH₂ have additionally been the subject of single crystal X-ray diffraction studies; in both structures the acetyloxymethyl group remained uncoordinated. On activationof Ni1 – Ni6 with MMAO, hexenes (C6: ca. 48% 1-hexene) formed the major product of ethylene oligomerization along with minor quantities of butenes (C4); high overall activities of up to 1.33 × 10⁶ g·mol–1 (Ni)h–1 (for mesityl-containing Ni4 ) were achieved at 30 ^oCand 10 atm C₂H₄. By comparison with MAO as co-catalyst, Ni1 – Ni6 exhibited lower activities but displayed a specificity towards ethylene dimerization (C4: 64–99% 1-butene). Furthermore, sizable induction periods were a feature of the MAO runs with Ni1 /MAO reaching peak catalytic activity only after 45 mins.     

Metal complexes of C2-symmetric chiral bipyridine ligands. X-ray structure of [bis(nitrato)(4S,5S)-2,2-dimethyl-4,5-bis(2-pyridyl)-1,3-dioxolane cobalt(II)]

Chelating properties of C₂-symmetric chiral bipyridine ligands are discussed. In particular we report the syntheses of the cobalt(II), nickel(II), zinc(II) and copper(II) complexes of (4S,5S)-2,2-dimethyl-4,5-bis(2-pyridyl)-1,3-dioxolane. All compounds have been characterized by IR spectroscopy, and an X-ray diffraction analysis has been carried out on one of them: Co(L)(NO₃)₂. The ligand coordinates the cobalt atom by the two nitrogen donors N(1) and N(2). A seven-membered chelation ring is formed, presenting a remarkable non-crystallographic twofold pseudosymmetry around the axis connecting Co and the midpoint of the C(6)–C(7) bond. The metal also binds two monodentate nitrates, thus completing a distorted coordination tetrahedron.     

Bis -(3,5-dimethyl-pyrazolyl-1-methyl)-(3-phosphanyl-propyl)-amine complexes of copper(II), nickel(II), and cobalt(II)

A series of Cu(II), Co(II), and Ni(II) complexes of bis-(3,5-dimethyl-pyrazolyl-1-methyl)-(3-phosphanyl-propyl)-amine C₁₅H₂₆N₅P (1), prepared from 3-aminopropylphosphine and 1-hydroxymethyl-3,5-dimethylpyrazole were characterized. The nature of bonding and the geometry of the complexes have been deduced from elemental analysis, infrared, electronic, ¹H NMR, ³¹P NMR spectra, magnetic susceptibility, and conductivity measurements. The studies indicate octahedral geometry for nickel complex and square pyramidal geometry for copper and cobalt complexes. The EPR spectra of copper complex in acetonitrile at 300 K and 77 K were recorded. Biological activities of the ligand and metal complexes have been studied on Staphylococcus aureus, Escherichia coli, Aspergillus niger, and Aspergillus flavus by well-diffusion method. The zone of inhibition values were measured at 37°C for a period of 24 h. The electrochemical behavior of copper complexes was studied by cyclic voltammetry. Catalytic study indicates the copper complex has efficient catalytic activity in oxidation of amitriptyline.