Synthesis,characterization and biomolecular interactions of Cu(II) and Ni(II) complexes of acyclic Schiff base ligand

Mononuclear copper(II) (1) and nickel(II) complexes (2) of acyclic Schiff base ligand, N,N′-bis(2-hydroxy-1-naphthyl)-1,4-bis(3-iminopropyl) piperazine (L) were synthesized and characterized. The molecular structure of the ligand was confirmed using single crystal X-ray diffraction analysis. The complexes displayed good binding abilities to bovine serum albumin protein (BSA). The binding interactions of complexes 1 and 2 with calf thymus DNA (CT-DNA) was investigated by absorption, fluorescence, circular dichroism spectral analysis and molecular docking studies. Complex 1 showed greater interaction with DNA than nickel(II) complex 2. The cleavage studies with pBR322 DNA showed efficient oxidative cleavage in the presence of 3-mercaptopropionicacid (MPA) and for hydrogen peroxide for complexes 1 and 2 respectively.     

A mononuclear copper(II) complex of a protonated unsymmetrical dinucleating Schiff base ligand

Reaction of the unsymmetrical and potentially dinucleating Schiff base ligand HL¹ with copper(II) salts has given mono- and dinuclear metal complexes. The structure of a mononuclear complex of diprotonated HL¹, [Cu(H₂L¹)(OH₂)](ClO₄)₃·H₂O·CH₃OH_, has been determined.     

A tubular luminescent Zn(II) coordination polymer with unsymmetrical bridge ligand

A novel 1D tubular coordination polymer [ZnL(dca)₂]_n (dca = dicyanamide, L = 2-(3-pyridylmethylthio)-5-(4-pyridyl)-1,3,4-oxadiazole) constructed by the unsymmetrical bridge ligands L spirally winding around two double-chain pillars Zn(dca)₂ was synthesized and characterized.     

One-dimensional helical Cu(II) coordination polymer: Synthesis,structures, and properties

One new Cu(II) coordination polymer (1) based on 6,6′-dihydroxy-2,2′-bipyridine (H₂dhbp) was successfully prepared, with the formula of [Cu(μ₂-OH)(Hdhbp)]_n (1). Single-crystal X-ray analysis shows that compound 1 crystallizes in orthorhombic chiral space group P2₁2₁2₁ and exhibits a left-handed (L) helical [Cu(μ₂-OH)]_n-chain. Luminescence of 1 exhibits a broad emission around 440 nm, attributing to the metal to ligand charge transfer (MLCT). Magnetic susceptibility shows antiferromagnetic coupling within compound 1. Cyclic voltammetry (CV) experiments indicate a potential water oxidation electrocatalyst.     

A new 3-D neutral framework coordination polymer constructed via square pyramidal binuclear Cu(II) and nicotinato ligand

A new 3-D neutral metal–organic framework polymer, [Cu(NA)₂] 1, has been synthesized under hydrothermal reaction conditions. The structure of 1 is self-assembled from binuclear square pyramidal copper(II) coordinated by multidentate nicotinato ligands.     

Adsorption of Cu(II) onto silica gel-immobilized Schiff base derivative

4-chloroisonitroacetophenone 4-aminobenzylhydrazone (CAAH) chemically anchored on a silica gel surface, has been used for Cu(II) sorption from aqueous solution. The surface modification processes was performed after silanization of silica, then analyzed by elemental analysis, infrared spectroscopy, and thermogravimetry. The sorption behavior of copper(II) was evaluated by the use of batch and column methods. The influences of the concentration, temperature and pH for sorption on the immobilized silica gel with Schiff base were investigated. The obtained dynamic data were fitted to Freundlich, Langmuir and Dubinin-Raduskevich (D-R) isotherms. The mean sorption energy (E) of copper sorption onto silica gel was calculated from D-R isotherm indicating a chemical ion-exchange. The thermodynamic parameters such as Gibbs free energy change, enthalpy change and entropy change were calculated from the adsorption isotherms which were used to explain the mechanism of the adsorption.     

A new three-dimensional Cu(II) coordination polymer with triaminoguanidin building blocks

The reaction between the tris(2-hydroxybenzylidene)triaminoguanidin hydrochloride (H₆L)Cl and copper(II) chloride in the presence of triethylamine leads to a three-dimensional coordination polymer with two interpenetrating (10,3)-a networks of opposite chirality. Magnetic studies revealed strong antiferromagnetic coupling between copper ions of the spin frustrated trinuclear building unit.     

Manganese(II)-promoted ligand oxidation during the formation of a coordination polymer

During the synthesis of Mn(II) compounds from fluorene-2,7-dicarboxylate, the ligand undergoes in situ oxidation to generate a Mn(II) coordination polymer with the ligand fluorenone-2,7-dicarboxylate (FODC^2 −). It was demonstrated that the transformation occurs with dioxygen as reactant and Mn(II) as catalyst. The resulting coordination polymer, [Mn₃(FODC)₃(DMA)₄]⋅2.5DMA, displays a 2D network based on the [Mn₃(COO)₆(DMA)₄] unit with triple carboxylate bridges. Magnetic analyses were performed not only on temperature-variable susceptibility but also on field-variable magnetization, indicating weak antiferromagnetic interactions through the triple bridges.     

Dinuclear based polymeric copper(II) complexes derived from a Schiff base ligand: effect of secondary bridging moieties on geometrical orientations and magnetic properties

[1 + 1] condensation of salicylaldehyde and 2-aminobenzenesulfonic acid led to the formation of the acyclic Schiff base o-[(o-hydroxyphenyl)methylideneamino]benzenesulfonic acid (H₂L) which, upon reaction with Cu(II) salts in the presence of triethylamine or 4,4′-bipyridine, formed a 2D polymeric species [Cu₂L₂]_n (1) via sulfonate bridge and a 1D polymeric complex [{Cu₂L₂(4,4′-bipy)}·DMF]_n (2) via 4,4′-bipyridine bridge, respectively. The copper cations sit on O₄N basal- or O₃N₂ facial-edge-sharing inverted square pyramidal environments in 1 or 2, respectively. In spite of their comparable compositions, the relative orientations of the metal polyhedra affect the magnetic properties of these polymers since 1, in contrast to 2, presents a strong exchange interaction of an antiferromagnetic nature.     

Three Cu(II) coordination polymers with novel bi-triazole ligand: Synthesis,structure and EPR properties

Three Cu(II) coordination polymers: [Cu(XL)(NO₃)₂]_n (1), {[Cu(XL)(4,4′-bpy)(NO₃)₂]·CH₃CN}_n (1a) and {[Cu(XL)₃](NO₃)₂·3.5H₂O}_n (2) have been synthesized mainly based on a novel bi-triazole ligand N,N′-bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxdiimide bi(1,2,4-triazole) (XL) and characterized by X-ray crystallography, EPR spectra, elemental analyses, FT-IR spectra and PXRD patterns. Structure analyses reveal that compounds 1 and 1a exhibit 1D chains, and compound 2 features a 2D cationic framework. Additionally, the Cu(II) ions with various coordination environment in compounds 1, 1a and 2 exhibit different EPR properties.     

Tris(μ-phenoxo) bridged Cd(II) polymer synthesised from a symmetrical tripodal ligand: A novel observation for heptadentate monocapped trigonal antiprismatic Schiff base complex

A novel one-dimensional cadmium(II) polymer [Cd₂(L){HCON(CH₃)₂}N(CN)₂]_n (H₃L = condensation product of tris(2-aminoethyl)amine and salicylaldehyde) has been achieved from a tripodal Schiff base tris[(2-salicylaldeneimino)ethyl]amine or ‘trensal’. The structure confirmed from single crystal X-ray diffraction analysis reveals that each of the tris(μ-phenoxo) bridged individual Cd(II) dimeric units is interlinked via μ-(1,5) end-to-end (EE) dicyanamide [N(CN)₂]⁻ ligand framing a wavy chain polymer, which is believed to be the first report of its kind in the literature.     

Magnetic properties and structure of a new one-dimensional azido-bridged nickel(II) coordination polymer

A new one-dimensional nickel(II) coordination polymer with azido-bridge, [Ni(dpa)(N₃)₂] · H₂O 1 (where dpa is the 2,2′-dipyridylamine ligand) has been synthesized and crystal structure was determined by single-crystal X-ray diffraction. Complex 1 exhibits a zig-zag chain structural arrangement, and the hexa-coordinated Ni(II) ion exhibits a distorted octahedral coordination sphere. The chains topologies are built via three EO and one EE azido bridges. The study of the magnetic properties reveals dominating antiferromagnetic interactions between Ni(II) ions through the EE bridges.     

Structural diversity in Cu(II) and Cd(II) coordination complexes with 4-amino-1,2,4-triazole ligand

The syntheses and structures of the series of metal complexes, namely [CuCl₂(L)₂·H₂O)]_n (L = 4-amino-1,2,4-triazole), 1; {[Cu(L)₄][ClO₄]₂.H₂O}_n, 2; and [Cd₂Cl₄(L)₂.2H₂O]_n, 3 are reported. These were prepared by the self-assembly of Cu(II) and Cd(II) salts with L in MeOH/H₂O system. All these complexes have been characterized by elemental analysis, IR spectrum, and single crystal X-ray diffraction. Complexes 1–2 show 1-D polymeric infinite chains, while complex 3 shows 2D pleated net. The anions Cl⁻ in complexes 1 and 3 act as bridging or terminal ligands to the metal atoms while the ClO₄⁻ anions in 2 are not coordinated to the metal centers.     

Two cobalt(II) coordination polymers based on carboxylate ligand: Preparation,crystal structures and magnetic properties

Two new coordination polymers, [Co₂(L)_1.5(OH)(H₂O)₂]·2H₂O (1) and [CoL(bpp)] (2) (H₂L = 2,5-dibenzoylterephthalic acid and bpp = 1,3-bis(4-pyridyl)propane), have been synthesized and characterized by elemental analyses, IR spectra, and thermogravimetric analyses. Their structures were determined by single crystal X-ray diffraction analyses. Complex 1 exhibits a 3D framework assembled from tetra-nuclear cobalt-oxygen bridged by carboxylic O atoms with a (4¹²·6³) topology. Complex 2 possesses a 2D layered structure which extends into a 3D architecture via C–H···π interaction between propane proton and the phenyl ring or pyridine ring of an adjacent sheets. Furthermore, the magnetic properties of them are discussed.     

In situ synthesis and dielectric properties of copper(II) and nickel(II) chiral Schiff base complexes

Two chiral Schiff base-containing complexes, [Cu(L¹)](ClO₄)₂·H₂O (1, L¹ = (S,S)-N1,N2-bis((1H-imidazol-4-yl)methylene)cyclohexane-1,2-diamine) and [Ni(L²)₂](ClO₄)₂ (2, L² = (S,S)-N1-((1H-imidazol-4-yl)methylene)cyclohexane-1,2-diamine) were synthesized from the reaction mixture of 1H-imidazole-4-carbaldehyde, (S,S)-1,2-diaminocyclohexane and Cu(ClO₄)₂·6H₂O or Ni(ClO₄)₂·6H₂O in methanol. Single-crystal X-ray diffraction analyses reveal that the in situ generated chiral Schiff base ligands L¹ and L² are bisubstituted and monosubstituted, respectively, corresponding to the different metal ions Cu^II and Ni^II. Variable-frequency and -temperature dielectric properties of 1 and 2 have been studied.     

Temperature/anion-dependent self-assembly of Co(II) coordination polymers based on a heterotopic imidazole-tetrazole-bifunctional ligand: Structures and magnetic properties

Reactions of Co(II) with 5-(3-(1H-imidazol-1-yl)phenyl)-1H-tetrazolate (HIPT) resulted in three Co(II) coordination polymers (CPs), namely, {[Co(IPT)₂(H₂O)₂]·2H₂O}_n (1), [Co(IPT)₂]_n (2), and {[Co₃(IPT)₂(CH₃COO)₂(OH)₂(H₂O)₂]·2H₂O}_n (3). Compound 1 that obtained from CoCl₂·6H₂O at 120 °C is a 2D network based on Co(II) ions and μ₂-IPT⁻ ligands. Compound 2 that obtained from CoCl₂·6H₂O at 170 °C exhibits a 3D framework based on linear trinuclear Co(II) SBUs and features a pcu network topology. Compound 3, which obtained by using Co(Ac)₂ as salt, displays a 2D network based on 1D SBUs. The structures of compounds 1–3 are dependent on the temperatures and inorganic anions. The magnetic properties of compounds 2–3 were also explored.     

Thermal decomposition of Cu(II)-bis(8-hydroxy-5-quinolyl)methane coordination polymer

The volatile products formed when the coordination polymer of copper(II) and bis-(8-hydroxy-5-quinolyl)methane was heated in vacuum at elevated preselected temperatures were examined. The amount of weight loss at each temperature was determined with a recording thermal balance at each fixed temperature. Infrared spectrophotometry was used to aid in the identification of the major volatile component. A sample was pyrolyzed directly into the mass spectrometer. The results show that the volatile product is for the most part the organic ligand bis(8-hydroxy-5-quinolyl)methane and not derivatives of the copper complex or fragments of the ligand. The mechanism for the decomposition previously proposed is supported.