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The objectives of this study were to gain insights into structure-retention relationships and to propose the model to estimating their retention. Chromatographic investigation of series of 36 Schiff bases and their copper(II) and nickel(II) complexes was performed under both normal- and reverse-phase conditions. Chemical structures of the compounds were characterized by molecular descriptors which are calculated from the structure and related to the chromatographic retention parameters by multiple linear regression analysis. Effects of chelation on retention parameters of investigated compounds, under normal- and reverse-phase chromatographic conditions, were analyzed by principal component analysis, quantitative structure-retention relationship and quantitative structure-activity relationship models were developed on the basis of theoretical molecular descriptors, calculated exclusively from molecular structure, and parameters of retention and lipophilicity., (Copyright © 2016 John Wiley & Sons, Ltd.)

Highly ordered 2D-hexagonal mesoporous silica has been functionalized with 3-aminopropyltriethoxysilane (3-APTES). This is followed by its condensation with a dialdehyde, 4-methyl-2,6-diformylphenol to produce an immobilized Schiff-base ligand (I). This material is separately treated with methanolic solution of copper(II) chloride and nickel(II) chloride to obtain copper and nickel anchored mesoporous materials, designated as Cu-AMM and Ni-AMM, respectively. The materials have been characterized by Fourier transform infrared (FT-IR) and UV-vis diffuse reflectance (DRS) spectroscopy, powder X-ray diffraction (XRD), transmission electron microscopy (TEM), N(2) adsorption-desorption studies and (13)C CP MAS NMR spectroscopy. The metal-grafted mesoporous materials have been used as catalysts for the efficient and selective epoxidation of alkenes, viz. cyclohexene, trans-stilbene, styrene, α-methyl styrene, cyclooctene and norbornene to their corresponding epoxides in the presence of tert-butyl hydroperoxide (TBHP) as the oxidant under mild liquid phase conditions.

The thiocarbohydrazone Schiff-base ligand with a nitrogen and sulphur donor was synthesized through condensation of pyridine-2-carbaldehyde and thiocarbohydrazide. Schiff-base ligands have the ability to conjugate with metal salts. A series of metal complexes with a general formula [MCl2(H2L)]·nH2O (MNi, Co, Cu and Zn) were synthesized by forming complexes of the N1,N5-bis[pyridine-2-methylene]-thiocarbohydrazone (H2L) Schiff-base ligand. These metal complexes and ligand were characterized by using ultraviolet-visible (UV-Vis), Fourier Transform Infrared (FT-IR), 1H and 13C NMR spectroscopy and mass spectroscopy, physicochemical characterization, CHNS and conductivity. The biological activity of the synthesized ligand was investigated by using Escherichia coli DNA as target. The DNA interaction of the synthesized ligand and complexes on E. coli plasmid DNA was investigated in the aqueous medium by UV-Vis spectroscopy and the binding constant (Kb) was calculated. The DNA binding studies showed that the metal complexes had an improved interaction due to trans-geometrical isomers of the complexes than ligand isomers in cis-positions., (Copyright © 2011 Elsevier B.V. All rights reserved.)

The synthesis, structure, spectroscopic and electro-spectrochemical properties of steric hindered Schiff-base ligand [N,N'-(3,4-benzophenon)-3,5-Bu(t)(2)-salicylaldimine (LH(2))] and its mononuclear Cu(II), Co(II), Ni(II), Mn(II) and Fe(II) complexes are described in this work. The new dissymmetric steric hindered Schiff-base ligand containing a donor set of NONO was prepared through reaction of 3,4-diaminobenzophenon with 3,5-Bu(t)(2)-salicylaldehyde. Certain metal complexes of this ligand were synthesized by treating an ethanolic solution of the ligand with an equimolar amount of metal salts. The ligand and its complexes were characterized by FT-IR, UV-vis, (1)H NMR, elemental analysis, molar conductivity and thermal analysis methods in addition to magnetic susceptibility, electrochemistry and spectroelectrochemistry techniques. The tetradentate and mononuclear metal complexes were obtained by reacting N,N'-(3,4-benzophenon)-3,5-Bu(t)(2)-salicylaldimine (LH(2)) with some metal acetate in a 1:1 mole ratio. The molar conductance data suggest metal complexes to be non-electrolytes., (Copyright (c) 2009 Elsevier B.V. All rights reserved.)

The ligand design factors that may influence the isolation of metallosupramolecular helicates or mesocates still deserve to be investigated. In this sense, dinuclear nickel(II), copper(II) and zinc(II) compounds were obtained by electrochemical synthesis using a family of five Schiff base ligands, H2Ln (n = 1–5), derived from bisphenylmethane and functionalized with bulky tert-butyl groups in the periphery and ethyl groups in the spacer. Six of the new complexes were characterized by X-ray crystallography, thus demonstrating that the helicate structure is predominant in the solid state. 1H NMR studies were performed for the zinc complexes to analyze if the helical architecture of the metal complexes is retained in solution. These studies reveal that the presence of a tert-butyl group in the ortho position with respect to the OH group is an essential factor identified for the existence of a helicate conformation in solution. [ABSTRACT FROM AUTHOR]

Template condensation of S-methylisothiosemicarbazones of acetyl- or benzoylacetone with 8‑quinolinecarboxaldehyde in the presence of nickel(II) and copper(II) ions gave four new mononuclear coordination compounds [NiL1]I (I), [CuL1I] (II), [NiL2]I (III), and [CuL2I] (IV). The chemical composition of the products was confirmed by elemental analysis, IR spectroscopy, and mass spectrometry, and the crystal structure of compounds I and II was determined by X-ray diffraction analysis (CCDC nos. 2266386, 2266387). X-ray diffraction study revealed a square planar coordination environment of the central ion of the cationic Ni(II) complex and square pyramidal geometry for the molecular Cu(II) complex. [ABSTRACT FROM AUTHOR]

A mononuclear copper(II) complex [CuLa] (1), and three mononuclear nickel(II) complexes [NiLa] (2), [NiLa]·CH3OH (2·CH3OH) and [NiLb] (3), where La and Lb are the dianionic form of N,N'-bis(4-bromosalicylidene)-1,2-cyclohexanediamine (H2La) and N,N'-bis(4-fluorosalicylidene)-1,2-cyclohexanediamine (H2Lb), respectively, were prepared and structurally characterized by spectroscopy method and elemental analyses. The detailed structures were determined by X-ray single crystal diffraction. All the copper and nickel complexes are mononuclear compounds. The metal ions in the complexes are in square planar coordination, with the two phenolate oxygens and two imine nitrogens of the Schiff base ligands. The biological effect of the four complexes were assayed on the bacteria strains Staphylococcus aureus, Escherichia coli and Candida albicans, which show that the substituent groups of the ligands and the metal ions can influence the antimicrobial activities. Complexes 1 and 3 have strong activity against Staphylococcus aureus and Escherichia coli, which are comparable to the reference drug tetracycline. [ABSTRACT FROM AUTHOR]

The article presents a new method of producing anhydrous nickel(II) perrhenate of high purity, entirely from waste from the national Cu industry. This method consists mainly of the reaction of water-washed nickel(II) oxide (obtained by purification in a mixture of alcohols, and subsequent roasting of the Ni-containing sulfate semi-finished products (NSP) at 1200 °C) with perrhenic acid (obtained using the ion exchange method). After the dissolution of nickel(II) oxide in the acid (at a temperature in the range of 60–80 °C) and obtaining a pH of 5–8, the solution is sent to evaporate to dryness, also at a temperature not exceeding 80 °C. The obtained crude nickel(II) perrhenate is washed with methanol and subsequently dried at 160 °C to obtain its anhydrous form, with the following composition: 10.5% of Ni; 66.6% of Re; <5 ppm of Bi, As, Zn and Cu; <10 ppm Co, Mg, Fe, K, Pb, Na, Ca and Mo. Importantly, this composition allows for the use of the compound for the production of superalloys and catalysts. A patent application and a technological scheme were prepared for the developed method. It consists of seven technological operations, including six based on processes in the field of hydrometallurgy, and one in the field of pyrometallurgy (roasting). [ABSTRACT FROM AUTHOR]

As previously reported, we have synthesized an azo azomethine ligand 4-((E)-(2,5 dichloro phenyl) diazenyl)−2-((E)-((4-hydroxyphenyl) imine) methyl) phenol (L). The synthesized ligand has been used to prepare copper(II), nickel(II), and cobalt(II) metal complexes and characterized using various analysis techniques. To identify complexes, methods, such as elemental analyses, electrical conductivity, IR spectroscopy, mass spectrometry, magnetic moment, vibrating sample magnetometry (VSM), 1HNMR, UV–Vis, and thermal analysis were utilized, and a mononuclear structure was proposed for all compounds and all the complexes are non-electrolytes in nature. The chelation of the ligands to the metal ions occurs through phenolic oxygen and nitrogen atoms of the azomethine group of the ligands. According to various analytical and spectral data, a square planar structure is proposed for copper and nickel metal complexes and a quadrilateral structure is proposed for cobalt complexes. The antibacterial properties of ligands and complexes of copper(II), nickel(II), and cobalt(II) were investigated in vitro on standard bacteria as well as on bacteria isolated from clinical specimens (urine). The results revealed that the ligand and its metal complexes had a very high antibacterial activity against Staphylococcus aureus, but were ineffective against other studied bacteria. The synergistic effect of the compounds with the three antibiotics (vancomycin (V), methicillin (M), and trimethoprim (T)) was also investigated, along with the cytotoxicity of its ligand and copper complex in HFF cell line. At a concentration of 3.90 μl of these compounds, cell viability was significant. The structure of ligand and complexes was optimized by DFT calculations. Computational methods were performed for deeper understanding of the interaction between ligands and metal by EDA calculations. This result confirmed that the bonding between ligands to metal was mainly covalent. The complexes investigated are reported for the first time. The search for new antimicrobial agents against Staphylococcus aureus is an urgent medical need. Therefore, sensitive and selective diagnosis of this pathogenic bacterium is of great importance, which has been obtained in this study. The compounds synthesized from among the nine gram-negative and gram-positive bacteria are only sensitive to Staphylococcus aureus bacteria. [ABSTRACT FROM AUTHOR]

Four new complexes of copper(II), nickel(II) and zinc(II), [CuL2] (1), [Ni3L2(4-BrSal)2(CH3COO)2(CH3OH)2]-2CH3OH (2), [ZnBr2(HL)2] (3) and [ZnL(dca)]n (4), where L is 5-bromo-2-((cychlopentylimino)methyl)phenolate, HL is the zwitterionic form of 5-bromo-2-((cychlopentylimino)methyl)phenol, 4-BrSal is the monoanionic form of 4-bromosalicylaldehyde, dca is dicyanamide anion, were synthesized and characterized by elemental analysis, IR and UV-Vis spectroscopy. The structures of the complexes were further confirmed by single crystal X-ray structure determination. Complex 1 is a mononuclear copper(II) compound, with a crystallographic two-fold rotation axis symmetry. The Cu atom is in distorted square planar coordination. Complex 2 is a trinuclear nickel(II) compound, with an inversion center symmetry. The Ni atoms are in octahedral coordination. Complex 3 is a mononuclear zinc(II) compound, while complex 4 is a dca bridged polymeric zinc(II) compound. The Zn atoms are in tetrahedral coordination. The compounds were assayed for their antimicrobial activities. [ABSTRACT FROM AUTHOR]

Novel ligand, (E)-4-((4-(dimethylamino)benzylidene)amino)-1,5-dimethyl-2-phenyl-1,2-dihydro-3H-pyrazol-3-one, L and its nickel, copper, and zinc complexes were designed and physicochemically investigated using various spectroscopic studies. Ligand was additionally characterized by single-crystal X-ray crystallography. DFT and Hirschfeld surface analysis studies were also carried out. The well-characterized compounds were tested for their antimicrobial activities. [Display omitted] A novel series of metal complexes of 3d elements of the type, [MLCl 2 ] [M = Ni(II), Cu(II) & Zn(II), L = ligand] produced from an ampyrone-based ligand was discussed. A thorough investigation was carried out using elemental analyses, LC-MS, FT-IR, 1H- &13C NMR, and thermogravimetric analysis for the ligand and its complexes. The ligand was additionally characterized through single crystal X-ray crystallography, revealing a monoclinic system with the C 2/ c space group, featuring dimensions a = 17.8776(12) Å, b = 6.8982(6) Å, c = 29.862(2) Å, β = 101.170(5)°. Hirshfeld surface analysis was employed to unveil various intermolecular interactions in the ligand. Additionally, theoretical investigations were conducted to have a better understanding of the structures. Moreover, the antimicrobial efficacy of all investigated compounds was assessed. [ABSTRACT FROM AUTHOR]

The self-assembly reaction of the bis-Schiff base N,N′-bis(4-Bromosalicylidene)-1,3-pentanediamine (H2L) with nickel chloride and sodium azide in methanol afforded a new phenolate and end-on azide bridged trinuclear nickel complex [Ni3L2(μ1,1-N3)2(CH3OH)2]2CH3OH (1). The reaction of H2L with copper acetate produced a new phenolate and acetate bridged trinuclear copper complex [Cu3L2(CH3COO)2] (2). The complexes were characterized by elemental analysis, IR and UV-Vis spectroscopy. The crystal structures of the complexes have been determined by X-ray crystallography. In complex 1, the Ni atoms are in octahedral coordination, while in complex 2, the Cu atoms are in square pyramidal and octahedral coordination. The Schiff base ligand coordinates to the metal atoms through the two phenolate O and two imine N atoms. The antimicrobial activities of the complexes were assayed and evaluated. [ABSTRACT FROM AUTHOR]

Anew ligand N-((3,5-dichloropyridin-2-yl)carbamothioyl) pivalamide (L²) was synthesized by reaction of benzoyl isothiocyanate with 2-Amino-3,5- dichloropyridine by using acetonitrile as a solvent, The ligand was characterized by elemental analysis apparatus, FT-IR, 13C,¹H-NMR spectra, UV-Visible,, some transition metals complexes(Co, Ni, Cu, Zn ) of this ligand was prepared and characterized by FT-IR, UV-Visible spectra, conductivity measurements, magnetic susceptibility,From results the proposed molecular structure for these complexes as obtained, the following formula where M+2 = Co, Cu, Ni, Zn [M :L² ] [1 :1] Tetrahedral and [M:L² ] [1:2] Octahedral . The biological activity of the prepared compounds was measured and tested as antifungals against (Candida albicans, Aspergillus Niger) and using DMSO as a control solution The results showed that the prepared compounds possess antifungal activity at different concentrations, The effectiveness of the prepared ligands and their complexes with Zn(ll) ions were studied as anti-elevation of T3 and T4 thyroid hormones induced by thyroxine, and the results showed a decrease in T3 and T4 hormones after (20) days of taking these compounds. [ABSTRACT FROM AUTHOR]

Novel transition metal complexes of nickel(II), copper(II) and zinc(II) with a symmetrical tetradentate Schiff base, obtained by condensation of 1,3-diaminopropane and 3,5-diiodosalicylaldehyde, N,N′-bis(3,5-diiodosalicylaldehyde)-1,3-diaminoporpane (H2L), have been prepared and characterized by elemental (CHN), FT-IR, UV–Vis and 1H NMR spectroscopic techniques. Out of these, copper (Cu(L)) and zinc (Zn(L)) complexes were isolated in the form of single crystals and characterized by single-crystal X-ray diffraction studies. In the Cu(L) complex, the geometry was found to be slightly distorted square planar, whereas the Zn(L) complex adapted slightly distorted octahedral geometry due to the attachment of two pyridine rings. The antibacterial screening of the prepared compounds was carried out by taking two Gram-positive (Staphylococcus aureus and Bacillus cereus) and two Gram-negative (Escherichia coli and Pseudomonas aeruginosa) bacterial strains. The appearance of zones of inhibition clearly depicted that the complexes have more retardation potential as compared to the Schiff base ligand. [ABSTRACT FROM AUTHOR]

In this study, the new Schiff base ligands N,N′-bis[(1Z,2E)-1-(4-methylphenyl)-2-(hydroxyimino)-1-phenylethylidene]-4-methylbenzene-1,2-diamine and N,N′-bis[(1Z,2E)-1-(4-chlorophenyl)-2-(hydroxyimino)ethylidene]-4-methylbenzene-1,2 diamine have been synthesized. Their metal complexes with copper and nickel have been formed and characterized by FT-IR, UV-Vis, NMR, LC/MS-MS spectra, molar conductivity, magnetic susceptibility, elemental analysis, ICP-OES, and thermogravimetric analysis. The complexes demonstrate semiconducting features. [ABSTRACT FROM AUTHOR]

[Display omitted] • Synthesis and characterization of copper, nickel and palladium complexes bound by bidentate ligands with tunable H-bond donors. • X-ray diffraction analysis of depicts intramolecular H-bonding interaction between the two ligand scaffolds. • Variations on the primary , secondaryand tertiary coordination sphere lead to changes in the geometry of the metal complexes. • Analysis of the complexes in the solid state reveals that the H-bonding interactions can be disrupted, changing the geometry of the complexes. • DFT calculations explain why Cu favors twisted geometries while Ni and Pd favor square-planar geometries. In this article, we describe the synthesis and characterization of a family of copper, nickel and palladium complexes bound by bidentate ligands derived from ortho -phenylenediamine that contain tunable H-bond donors. The crystal structures of the reduced dianionic metal complexes (formulated as [MII(L2-) 2 ]2-) depict intramolecular H-bonding interaction between the two ligand scaffolds. Variations on the primary (Cu, Ni, Pd), secondary (H-bonding donor) and tertiary coordination sphere (solvent of crystallization and countercation), led to the isolation of the metal complexes in square-planar (SP) and/or twisted pseudo-tetrahedral geometry (TW). A detailed structural analysis of the complexes in the solid state revealed that the intramolecular H-bonding interactions can be altered by disrupting the bonds between the countercation, solvent of crystallization and the ligand scaffold, which leads to changes in the geometry of the complexes (SP or TW). DFT calculations are in agreement with our experimental observations, in which the Cu complexes were found to favor twisted geometries while the Ni and Pd complexes favored square-planar geometries. [ABSTRACT FROM AUTHOR]

[Cu(L)2] (1), [Co(L)2] (2), [Ni(L)2]·H2O (3) complexes where L is 2-{[(2-methoxyphenyl)amino]methylene}-5,5-dimethyl-cyclohexane-1,3-dionate are synthesized. Single crystals of complexes 1-3 are obtained. According to X-ray crystallographic data, in the Co and Ni complexes, a coordination polyhedron N2O4 is a distorted octahedron, and in the Cu complex, N2O2 is a distorted square. L is a tridentate ligand coordinated by oxygen atoms of carbonyl and methoxy groups as well as the nitrogen atom of the amide group. The cytotoxic properties of 2-{[(2-methoxyphenyl)amino]methylene}-5,5-dimethyl-cyclohexane-1,3-dione and respective complexes are studied on the Hep2 cell line (human laryngeal carcinoma). The compounds are shown to not exhibit cytotoxic properties in the studied concentration range (1-50 μM). Antibacterial, protistocidal, and fungistatic properties of HL, its structural analogue 2-anilinomethylidene-5,5-dimethylcyclohexane-1,3-dione (HL1), and complexes on their base are also studied. The antibacterial activity of HL and [Co(L1)2(C2H5OH)2] against S. aureus, of HL1 and [Co(L)2] against E. coli is revealed within 25-30% of the activity of reference drugs (ciprofloxacin, furazolidone). The [Ni(L1)2(C2H5OH)2] complex is found to have a pronounced protistocidal activity. Furthermore, the behavior of the [Ni(L)2]·H2O complex in phosphate buffered saline is analyzed at storage times t = 0 h, 24 h, 48 h and also in an aqueous solution at different pH values. [ABSTRACT FROM AUTHOR]

Two copper(II) complexes, [Cu2(L1)2]·2H2O (1) and [Cu3(L1)2(NCS)2] (2), and two nickel(II) complexes, [NiL2(NCS)] (3) and [Ni(L2)2(NCS)]·CH3OH (4), were prepared from the fluorine substituted Schiff bases N,N'-bis(4-fluorosalicylidene)-1,2-diaminopropane (H2L1) and 4-fluoro-2-[(2-isopropylaminoethylimino)methyl]phenol (HL2), respectively. The compounds were characterized by physico-chemical methods. Structures of the complexes were further confirmed by single crystal X-ray diffraction. The Cu ions in 1 are square pyramidal, and in 2 are square planar and octahedral. The Ni ion in 3 is square planar, and in 4 is octahedral. All the complexes have effective Jack bean urease inhibitory activities. Complex 1 has the most effective activity, with an IC50 value of 2.1 ± 1.3 μmol L−1. [ABSTRACT FROM AUTHOR]

Pyrimidine derivative Schiff base ligand (DPMC) stabilized metal nanoparticles of copper (DPMC-CuNPs) and nickel (DPMC-NiNPs) were synthesized by modified Brust-Schiffrin technique, which is a two-step phase transfer assisted synthesis. The prepared metal nanoparticles were confirmed by UV-Visible and Infrared spectroscopy. The size, surface morphology and the quality of the DPMC and its MNPs were analyzed by Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) methods respectively. Electrochemical behavior of the DPMC-CuNPs and DPMC-NiNPs was analyzed by cyclic voltammetry method. DNA binding studies of the synthesized compounds with CT-DNA were examined by four different techniques such as UV-Visible and emission spectroscopy, cyclic voltametry and viscometric measurments. Thermal denaturation and sono-chemical denaturation studies of DNA with the DPMC, DPMC-CuNPs and DPMC-NiNPs results also suggest the synthesized compounds have good DNA binding ability. Various antioxidant scavenging studies results shows that DPMC and its copper and nickel nanoparticles have significant antioxidant activity. Antimicrobial studies of the DPMC and its MNPs were studied by Agar-Agar well diffusion method. Anticancer studies of the DPMC and its MNPs show that the DPMC-CuNPs and DPMC-NiNPs have significant anticancer activity with least toxicity than the standard drug cis-platin. [ABSTRACT FROM AUTHOR]

The di dentate ligand type N2 have been prepared through two steps. The first included the reaction between one equivalent of ethylenediamine with tow equivalent of benzaldehyde the second included the reaction of first step precursor with one equivalent of sodiumborontetrahydride (NaBH4), to obtained the target ligand. Ni+2, Cu+2, Zn+2 from there action of the ligand Complexes were prepared with metal ions 1:1 ratio, the proposed compounds were characterized by FT-IR, UV-Vis, NMR for ligand, C.H.N spectroscopies, the biological activity as well as the molar conductivity and magnetic the success stability. Suggested geometry around the Zinc and Copper ions is tetrahedral and square planer around nickel ion. [ABSTRACT FROM AUTHOR]

Azo Schiff base ligand 2-hydroxy-3-methoxy-5-(tolyldiazenyl)benzaldehyde oxime (HL1) and 2-hydroxy-3-methoxy-5-(methoxyphenyl)benzaldehyde oxime (HL2) were prepared along with their transition metal complexes of Ni(II), Cu(II), and Zn(II). Ligands and their metal complexes were characterized by several analysis techniques. In- vitro antibacterial, antioxidant and anti-inflammatory activities of synthesized ligands and their metal complexes have been studied. Biological study showed that amongst all the synthesized compounds, Cu(II) complexes possessed excellent antibacterial activity than standard antibiotic Chloramphenicol. Ligands (HL1) and (HL2) showed excellent antioxidant as well as anti-inflammatory activity. Both the ligands were tested for their protective effect of free radicals against plasmid DNA and it was found that both the ligands showed good DNA nicking activity. [ABSTRACT FROM AUTHOR]

• Ni and Cu(II) complexes with (E)−1-((p -tolylimino)methyl)naphthalen-2-olate. • X-ray molecular structures of square-planar ni and Cu(II) complexes. • Mesomorphic properties of Cu(II) schiff base complex. • Combined analyses of experimental and theoretical (DFT/TD-DFT) results. Reaction of the Schiff base ligand (E)-1-((p -tolylimino)methyl)naphthalen-2-ol (HL) with nickel(II) and copper(II) acetate provides the bis[1-((p -tolylimino)methyl)naphthalen-2-olato-κ2N,O]Ni and Cu(II) complexes (1 and 2), respectively. X-ray structure determinations reveal coordination of two N,O-chelate Schiff base ligands to the metal ion in a square-planar geometry for both the complexes. The phase purity of bulk microcrystalline samples is confirmed by Powder XRD patterns. The solid-state magnetic moment (µ eff = 2.73 (1) and 2.06 µ B (2)) indicates paramagnetic nature of the complexes. Thermal analyses by differential scanning calorimetry (DSC) and polarizing light microscopic (PLM) observations suggest mesomorphic property for 2. Cyclic voltammograms recommend a quasi-reversible two one electron charge transfer processes for 2 in dimethylformamide. Geometry optimization and excited state properties by DFT/TD-DFT calculations reproduce the experimental bond distances and angles as well as the experimental electronic spectra. Reaction of the Schiff base (E)-1-((p -tolylimino)methyl)naphthalen-2-ol with nickel(II) and copper(II) acetate provides the square-planar bis[1-((p -tolylimino)methyl)naphthalen-2-olato-k2 N,O]Ni and Cu(II) complexes, respectively. [Display omitted] [ABSTRACT FROM AUTHOR]

The new bidentate (monobasic) Schiff base ligand 1-(3-((E)-(2,4-dihydroxybenzylidene) amino) phenyl) ethanone oxime H3L has been prepared froma condensation reaction of 3-aminoacetophenonoxime and 4 Hydroxysalicylaldehyde. Many physical and analytical instruments were used to characterizethe H3L as, (U.V-Vis, IR) spectroscopy and (1H, 13C) NMR spectra. Complexes of this ligand with Cr(III), Mn(II), Co(II), Ni(II), and Cu(II) have been preparedand recognized due tothe spectroscopy of (IR, U.V-Vis), magnetic susceptibility behavior, atomic absorption, and conductivity measurements. The different results confirmed the coordination behavior of the H3L by its rapid ability to coordinate with selected metal ions. The antibacterial activity of prepared compounds was also studied with selected two Gram-positive and two Gram-negative bacteria. Square planar structures for Ni(II) and Cu(II) complexes and Octahedral structure for three others. [ABSTRACT FROM AUTHOR]

Graphical abstract Described is the synthesis and characterization of two coordination complexes, a mononuclear Cu(II)L and a mononuclear Ni(II)L H2L = 1,1′-(((2-hydroxypropane-1,3-diyl)bis(azanylylidene)) bis(methanylylidene))bis(naphthalen-2-ol). Highlights • Described are Cu(II) and Ni(II) 1:1 coordination complexes of a Schiff base ligand. • Both complexes are 4-coordinate square planar with 2 phenolic oxygens and 2 imine nitrogens. • In contrast, the central pendant hydroxyl group was not observed to coordinate. Abstract With this work, we describe the synthesis and characterization of two new coordination complexes, a mononuclear Cu(II)L and a mononuclear Ni(II)L where the free base ligand is H 2 L = 1,1′-(((2-hydroxypropane-1,3-diyl)bis(azanylylidene)) bis(methanylylidene))bis(naphthalen-2-ol). In both metal complexes, the coordination environments are observed to be 4-coordinate square planar with two phenolic oxygens and two imine nitrogens coordinating the metal while the central pendant hydroxyl group was not observed to participate in coordination. In contrast to previously reported dinuclear complexes with similar ligand systems, the alkaline conditions presented in this work resulted in only the mononuclear coordination environments observed. [ABSTRACT FROM AUTHOR]

Urease catalyzes the decomposition of urea into ammonia, which has harmful effects on both human health and fertile soil. Aiming at exploring novel urease inhibitors, a series of hydrazone compounds and their CoIII, CuII, NiII, and ZnII complexes were prepared from 4-methoxy-N'-(pyridin-2-ylmethylene)benzohydrazide (HL). They are [CoClL(NCS)] (1), [CoL2]·Cl·CH3OH·H2O (2), [CuL(NCNCN)]n·nCH3OH (3), [NiL(HL)]·ClO4·CH3OH (4) and [ZnClL(OH2)]·CH3OH (5). The compounds were characterized by physico-chemical methods. Structures of the complexes were further confirmed by single crystal X-ray diffraction. The metal ions in 1, 3, and 5 display square pyramidal coordination and 2 and 4 display octahedral coordination. The inhibitory effects of the compounds on Jack bean urease were evaluated. The results showed that 3 has effective urease inhibitory activity, with IC50 value of (7.3 ± 1.0) μmol L−1. [ABSTRACT FROM AUTHOR]

A novel set of Cobalt(II), Copper(II) and Nickel(II) complexes of ligands, (E)-2-(((2,5- difluorophenyl)imino) methyl)phenol (A), (E)-2,4-dibromo-1-((2-hydroxybenzylidene) amino) anthracene-9,10-dione (D) & (Z)-1-((1-([1,1'-biphenyl]-4-yl)-2-bromoethylidene) amino)-2,4-dibromo anthracene-9,10-dione (E) were synthesized and characterized. Their structures were investigated on the basis of CHN, conductance measurements and spectral studies (1HNMR & 13CNMR, FTinfrared and Electronic spectroscopies), cyclic voltammetry. It has observed from spectral and analytical studies that metal complexes have the composition of (ML2.X2) and one mole of ligand behaves as bidentate chelating agents around the corresponding metal ion. From solubility test, we obtained that metal complexes of ligands A, D and E had no ionic properties and dissolve partially in polar and slightly in nonpolar solvents. These results confirmed the behavior of metal complexes as weak electrolyte from their low value of molar conductivity. Conductance data and solubility test of the complexes enhanced them to be (1:2 M:L ratio). All data confirmed an octahedral geometry of these complexes and their structures as {[M (A, D or E)2(CH3COO)2], when M= Co or Ni} and {[Cu (A, D or E)2 Cl2]}. Cyclic voltammetry measurements were accomplished of Cobalt(II), Copper(II) and Nickel(II) complexes using Pt wire as counter electrode and Ag/AgNO3 as reference electrode and (Bu4N+PF6+) as supporting electrolyte. The result exhibit the irreversible process showing single one electron transfer process of Cobalt(II) and Nickel(II) complexes and unique quasi-reversible redox couple is attributed to Cu(II) complexes. [ABSTRACT FROM AUTHOR]

Abstract The Schiff base ligand 2-(((2-(pyridin-2-yl)ethyl)imino)methyl)phenol (Salpea) was derived from the condensation reaction of 2-(2-pyridyl)ethylamine and salicylaldehyde. Three Schiff base complexes of the ligand were synthesized by reacting the Salpea ligand with Zn(II), Cu(II), and Ni(II) perchlorate hexahydrate salts. The compounds were analyzed by H-NMR, FT-IR, and UV–visible spectroscopies. CHN elemental analysis and x-ray crystallography were also employed for characterization in this research. Kinetic studies were performed on these complexes to evaluate their efficiency as catalysts for the hydrolysis of 4-nitrophenylphosphate (4NPP) in DMSO:H 2 O (1:1) solvent mixture using a TRIS buffer solution. It was determined experimentally that the complexes are catalytically active in hydrolysis of the phosphate ester studied (4NPP). Second order rate constants on the order of 10−3 M−1 s−1 were observed for the complexes studied. Graphical abstract Unlabelled Image Highlights • Three complexes have been synthesized (Zn(II), Cu(II), Ni(II) Salpea complexes) in an ongoing effort to synthesize complexes to use as biomimetics. • CHN analysis, 1H NMR, FT-IR, and x-ray crystallography have been employed in our studies to verify the structure of our complexes. • The complexes contain dinuclear cations bridged by phenoxy O atoms with a metal ion atom coordinated by nucleophile to assist in the hydrolysis mechanism. • It was determined experimentally that the complexes are catalytically active in hydrolysis of the model phosphate ester substrate studied. [ABSTRACT FROM AUTHOR]

Many Schiff bases prepared from 2-hydrazinobenzothiazole and isatin have been used to produce Co (II) complexes of the form [ML 2 ]Cl 2. Nitrogen from azomethine, oxygen from lactonyl, and nitrogen atoms of the thiazole ring contribute to coordinating the metallic ion. Complexes made entirely of metal have geometrical octahedrons, according to analytical, magnetic studies and spectroscopic (Infrared, Ultraviolet-Visible, ESR, FAB-mass) investigations. The conductivity measurements show the electrolytic behaviour of the metal complexes. The redox behaviour of the metal complexes is investigated using cyclic voltammetry. The antibacterial and antifungal activities of the Schiff bases and their metal complexes were examined using the Minimum Inhibitory Concentration method against Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, and S. typhi. Investigations into DNA cleavage were conducted using the agarose gel electrophoresis technique, and significant DNA cleavage was found. [ABSTRACT FROM AUTHOR]

A series of new dimer complexes of copper (II) and nickel (II) were designed and synthesized using the Schiff base ligands which was formed by the condensation of 2-aminothiophenol with 2- methoxybenzaldehyde, 3-formylbenzonitrile and 3-bromo-2-hydroxy-5-nitrobenzaldehyde, respectively. The synthesized metallic complexes were characterized by using different physicochemical and spectroscopic methods. The most plausible geometry for the 1:2 complexes appeared to be distorted square-planar or tetrahedral environments. All the synthesized metal complexes are found to be binuclear and confirmed by elemental analyses, magnetic susceptibility measurements and ESR spectroscopy. The Schiff base ligands (HL 1 /HL 2 /H 2 L) were coordinated to the metal ions through the ONS/SNN and/or N, S donor atoms. In order to prevent the oxidation of the thiol group during the formation of Schiff bases and its complexes, all of the reactions were carried out under an inert atmosphere of argon. The X-ray structures of the Schiff base ligands showed that in the crystalline form the SH groups were oxidized to produce a disulfide Schiff bases as a new double Schiff base ligands (L 1 a /L 2 a /H 2 L a ). The L 1 b ligand is a bicyclic ring system of N, S-containing heterocyclic. The crystal structures of the double Schiff bases were determined by single crystal X-ray diffraction. The molar conductivity values of the complexes in DMSO implied the presence of non-electrolyte species. The SOD-like activity of Schiff bases and its complexes were investigated by NBT-DMSO assay and IC50 values were evaluated. Their biological properties have also been studied. These complexes were also tested for their in vitro antibacterial screening activities against three bacteria ( Streptococcus aureus, Salmonella typhi, and Escherichia coli ) comparing with the Schiff base ligands. Most of the complexes have higher antibacterial activities than those of the free Schiff bases, double Schiff bases and the control. [ABSTRACT FROM AUTHOR]

[Display omitted] • Fluorescence silent Ni(II) based chemosensor, AR-1 has been unveiled towards " turn on " chromo-fluorogenic recognition of F- and Zn2+ over Cd2+. • The detection threshold values were acquired to be 1.3 μM (388 ppb) for Zn2+ and 3.4 μM (887 ppb) for F-. • The chemodosimetric recognition event has been authenticated via experimental as well as theoretical DFT studies. • AR-1 can be useful for monitoring copper deficiency myelopathy (CDM) based on Zn2+ detection capability from serum specimen. • AR-1 has also been employed towards three-input-two-output logic circuitry fabrication, which is unique of its kind in the relevant domain. Towards exploration of one-to-two unimolecular system, the applicability of a fluorescence silent Ni(II) based chemosensor, AR-1 comprised of NO 2 donor Schiff base ligand towards " turn on " chromo-fluorogenic recognition of F− and Zn2+ over Cd2+ via mutually independent pathways has been unveiled in the present work. The sensing phenomenon is very fast within ∼18 sec for Zn2+ and ∼24 sec for F− with the emergence of bright greenish cyan and yellowish green coloured fluorescence respectively. The detection threshold values were acquired to be 1.3 μM (388 ppb) for Zn2+ and 3.4 μM (887 ppb) for F−. UV–vis, fluorescence, mass spectroscopic and electrochemical investigation with theoretical DFT and TDDFT studies support the chemodosimetric sensing phenomenon. AR-1 , characterized by single crystal X-ray data, is equally responsive towards solid state sensing of the targeted analytes. Moreover, it has also been employed towards preparation of three-input-two-output logic circuitry, which is unique of its kind in the relevant domain. Most interestingly, to the best of our knowledge, AR-1 is the first Ni(II) based Schiff base chemoreceptor, which has been effectively implemented for real-time detection of Zn2+ from complex bio-matrix, like serum upto 1.83 μM (544 ppb). This may give an indication of copper deficiency myelopathy (CDM), of which early diagnosis may reduce the risk of irreversible neurological damage. [ABSTRACT FROM AUTHOR]

Cover Feature: Copper and Nickel Complexes of Oxamate-Phenol Containing Ligands: A Structural Dichotomy in Oxidized Species (Eur. J. Inorg. Keywords: Amidates; Copper; iminosemiquinone; Nickel; Phenoxyl ligands EN Amidates Copper iminosemiquinone Nickel Phenoxyl ligands 1 1 1 05/26/23 20230524 NES 230524 B The Cover Feature b shows a redox-active complex combining phenols and oxamato units. Both copper complexes catalyze the oxidation of benzyl alcohol into benzaldehyde and benzoic acid, albeit with different time scales. [Extracted from the article]

Two novel Schiff bases, L 1 = (2-benzo[d]thiazol-6-ylimino)methyl)-4,6-dichlorophenol), L 2 = (1-benzo[d]thiazol-6-ylimino)methyl)-6-bromo-4-chlorophenol) and their bivalent transition metal complexes [M(L 1 ) 2 ] and [M(L 2 ) 2 ], where M = Cu(II), Co(II) and Ni(II) were synthesized and characterized by elemental analysis, NMR, IR, UV–visible, mass, magnetic moments, ESR, TGA, SEM, EDX and powder XRD. Based on the experimental data a square planar geometry around the metal ion is assigned to all the complexes ( 1a-2c ). The interaction of synthesized metal complexes with calf thymus DNA was explored using UV–visible absorption spectra, fluorescence and viscosity measurements. The experimental evidence indicated that all the metal complexes strongly bound to CT-DNA through an intercalation mode. DNA cleavage experiments of metal(II) complexes with supercoiled pBR322 DNA have also been explored by gel electrophoresis in the presence of H 2 O 2 as well as UV light, and it is found that the Cu(II) complexes cleaved DNA more effectively compared to Co(II), Ni(II) complexes. In addition, the ligands and their metal complexes were screened for antimicrobial activity and it is found that all the metal complexes were more potent than free ligands. [ABSTRACT FROM AUTHOR]

The synthesis of chitosan Schiff bases, N-benzylidene chitosan (CTB), 4-dimethylamino-benzylidene chitosan (CTDB) and 4-nitro-benzylidene chitosan (CTNB), and their interaction with Cu, Zn and Ni were studied. The content of metal ions was determined by atomic absorption spectrometry, and the results showed that chitosan exhibited higher chelating capacity for the metal ions. Morphological changes of Schiff bases and complexes were demonstrated by SEM images. The presence of crystals attributed to copper sulfate adsorbed on the polymers surface was also observed, which indicates that part of the metal content is in the salt adsorbed and might influence in their further application studies. X-ray diffraction patterns showed that the formation of complexes resulted in the decrease in crystallinity. The thermal behavior of derivative and metal complexes were studied by thermogravimetric analysis, differential thermogravimetric analysis and differential scanning calorimetry. The results showed that the presence of new groups and metal ions bonded to chitosan affected their thermal stability. [ABSTRACT FROM AUTHOR]

The schiff base ligand and its complexes of divalent metal ions of Ni (II) and Cu (II) were synthesized. The ligand and the complexes were characterized by elemental analysis, potentiometry, molar conductance, melting point or decomposition temperatures and infrared analyses, The elemental analysis data show the formation of1:2 metal-ligand ratio. The ligand and complexes were screened for antibacterial activity against Escherichia coli and Staphylococcus au/eus, and antifungal activity against Aspergillums niger and Candida albican, using dises diffusion method. It bas been found tbat the ligand and the complexes showed different activities against microorganisms. The complexes show higher activity than the free Schiff base ligand. The molar conductance of the complexes measured is low, indicating their non-electrolytic nature. The potentiometric studies ofthe complex compounds revealed 1:2 metal to ligand ratio. [ABSTRACT FROM AUTHOR]

The synthesis, spectroscopic and structural characterization, electrochemical properties and theoretical studies of a series of eight robust neutral Nickel(II) and Copper(II) complexes ( 4 – 11 ) supported by unsymmetrically-substituted N 2 O 2 -tetradentate Schiff base ligands are reported. The M(salophen)-type compounds are substituted by either a pair of donor (anisyl, ferrocenyl, methoxy) or acceptor (fluoro, nitro) groups, forming D-π-D and A-π-A systems, respectively. The compounds were prepared in good yields by condensation of the free amino group of the desired ONN-tridentate half-unit with the appropriate substituted salicylaldehyde in the presence of hydrated Nickel(II) or Copper(II) acetate salts. They were characterized by elemental analysis, FT-IR, UV–vis, and for diamagnetic species by multinuclear NMR spectroscopy, mass spectrometry and cyclic voltammetry. The crystal structures of one Ni(II) ( 4 ) and four Cu(II) complexes ( 5 , 7 , 9 and 11 ) revealed a four-coordinate square-planar environment for the nickel and copper metal ions, with two nitrogen and two oxygen atoms as donors. In 4 , 5 , 7 and 9 , the crystallization solvent interacts through hydrogen bonding with the phenolato oxygen atoms of the Schiff base pocket, while 11 packs as centrosymmetric dimers with an apical Cu O short contact interaction (2.63 Å). the cyclovoltammograms of the nickel complexes present an irreversible mono-electronic Ni(II)/Ni(I) reduction wave while those of their copper counterparts exhibit a reversible or quasi-reversible one-electron Cu(II)/Cu(I) redox process. The electronic structures of the eight complexes were analyzed by DFT and TD-DFT calculations. [ABSTRACT FROM AUTHOR]

A new Schiff base thiosemicarbazone ligand with aqueous solubility, namely, sodium 3-{[(anilinocarbonothioyl)hydrazono]methyl}-4-hydroxy benzene sulfonate (NaH 2 L) was synthesized by condensation of 4-phenylthiosemicarbazide and sodium salicylaldehyde-5-sulfonate (NaSalSO 3 ) and characterized by elemental analysis, spectroscopic methods (UV–Vis, 1 H NMR, FTIR) and electrospray ionization mass spectrometry. A co-crystal (Na(H 2 L)·Na(SalSO 3 )) of NaH 2 L and NaSalSO 3 was prepared which confirmed the expected structure of the ligand. Reactions of NaH 2 L·0.5H 2 O with copper(II), nickel(II), and zinc(II) acetates were investigated under reflux conditions in methanol to produce following complexes [Cu 2 (L cycl ) 2 (H 2 O) 2 ]·2H 2 O ( CuL cycl ), Ni(HL)(H 2 O) 3 ( NiL ), and Zn(HL)(H 2 O) 3 ( ZnL ). In the copper case, dinuclear copper complex [Cu 2 (L cycl ) 2 (H 2 O) 2 ]·2H 2 O (where HL cycl − represents incorporating of 1,3-benzothiazole ligand, formed by in situ cyclization of H 2 L − ) was isolated. In the dimer structure copper atoms adopt a five-coordinate near square pyramidal geometry. Two oxygens derived from two sulfonate groups occupy the apical positions on both the metal centers and bridge them. The compounds have remarkable solubility in water at 25 °C: 50, 10, 50, and 50 g/L for NaH 2 L·0.5H 2 O, CuL cycl , NiL , and ZnL , respectively. The stability of the compounds was checked in acidic, neutral, and basic aqueous solutions. Antimicrobial activity results indicated CuL cycl and NiL possess activity against gram-positive bacteria and fungus while the free ligand and ZnL are inactive. Antioxidant activity of the compounds was evaluated and the ligand indicated the strongest radical scavenging relative to the complexes and l -ascorbic acid as a water-soluble standard. It was observed that copper and nickel complexes decreased the viability of the human chronic myeloid leukemia K562 cells in a dose- and time-dependent manner and the ligand and zinc complex were not active. The IC 50 values were 31 ± 2.5 and 6 ± 1.0 μg/mL (72 h) for copper and nickel complexes, respectively. Morphological and DNA fragmentation assay studies clearly indicated that the nickel complex as the strongest compound induce apoptosis in the K562 cell line. [ABSTRACT FROM AUTHOR]

Herein we report spectroscopic, thermal, non-isothermal decomposition kinetics and theoretical studies of two mononuclear Ni(II)- and Cu(II)-complex of general formula [M(L)(HO)]· xHO; {M = Ni(II) & Cu(II)} derived from tridentate 2,4-dichloro-6-{[(5-chloro-2-sulfanylphenyl)imino]methyl}phenol ligand (HL). These compounds were synthesized and characterized by various physicochemical and spectral techniques. Thermal decomposition of complexes was studied in four steps at different temperature regions to understand the degradation pattern of complexes under nitrogen atmosphere up to 1073 K at the 10 K min heating rate. The non-isothermal kinetic parameters viz. activation energy ( E*), pre-exponential factor ( Z), entropy of activation (Δ S*), enthalpy of activation (Δ H*) and free energy of activation (Δ G*) of degradation process were calculated using Coats-Redfern (C-R), Piloyan-Novikova (P-N) and Horowitz-Metzger (H-M) methods assuming first order degradation and proposing a random nucleation mechanism of thermal decomposition. Quantum chemical computational investigations were carried out at the B3LYP level using 6-31G basis set. The calculated harmonic vibrations were compatible with the observed FTIR and Raman frequencies. The thermodynamic properties ( C °; S ° and H °) with varying temperatures up to 500 K and non-linear optical properties were also evaluated at the same level of theory. Graphical Abstract: [ABSTRACT FROM AUTHOR]

A new colorimetric chemosensor 1 , containing the 7-nitrobenzo-2-oxo-1,3-diazolyl (NBD) moiety and the phenol one connected through Schiff-base linkage, has been synthesized. Sensor 1 showed remarkable color changes from pink to orange and pale brown, respectively, upon selective binding to Ni 2 + and Cu 2 + that can be identified by the naked-eye. The binding modes of sensor 1 to Ni 2 + and Cu 2 + were determined to be 1:1 stoichiometries using a Job plot and ESI-mass analysis. The sensor 1 showed high sensitivity toward Ni 2 + and Cu 2 + with the detection limits of 0.48 μM and 0.26 μM, respectively. The recognition properties of the sensor 1 toward Ni 2 + and Cu 2 + were explained by using photophysical experiments and theoretical calculations. Practically, sensor 1 functioned as a visible test strip for Ni 2 + and Cu 2 + . [ABSTRACT FROM AUTHOR]

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Five mono-nuclear Cu(II) and Ni(II) complexes and one dinuclear Zn(II) complex were synthesized from the Schiff bases N,N'-bis(3-ethoxy-2-hydroxybenzylidene)-1,2-phenylenediamine (H2LOEt-phda) and 2-ethoxy-6-({2-[(3-ethoxy-2-hydroxybenzylidene)amino]-benzyl}iminomethyl) phenol (H2LOEt-ambza): [Cu(LOEt-phda)(H2O)]·H2O(1), [Ni(LOEt-phda)]·H2O(2), [Cu(LOEt-ambza)]·H2O·EtOH (3), [Cu(LOEt-ambza)]·H2O (4), [Ni(LOEt-ambza)] (5) and [Zn2(LOEt-ambza)(μ-OAc)(OAc)] (6). The complexes were structurally characterized with elemental microanalyses, IR, UV-Vis and ESI-MS spectroscopic techniques as well as single crystal X-ray crystallography. The metal centers display distorted square planar geometries in 2-4 and 5 and distorted square pyramidal (SP) in 1, whereas in 6 an intermediate geometry between SP and TBP was observed around the first Zn2+ ion and a tetrahedral around the second ion, with one acetate is acting as a bridging ligand. In all cases, metal ions were incorporated into the N2-O2 binding site with no involvement of the alkoxy groups in the coordination. The LOEt-ambza-complexes 3-6 revealed significant dihedral angles between the phenol rings and the plane containing the central benzene ring, and large O2-O2 bond distances (5.1-5.9 Å'). Results are discussed in relation to other related Schiff base complexes. [ABSTRACT FROM AUTHOR]

Five new Ni(II) Schiff base complexes [NiLx(Solv)2] denoted by NiLx,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 NiL3was 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. [ABSTRACT FROM PUBLISHER]

We report the synthesis, characterization, crystal structures, nonlinear-optical (NLO) properties, and density functional theory (DFT) calculations of nickel(ii) and copper(ii) complex based ONO tridentate Schiff base ligands: two mononuclear compounds, [Ni(An-ONO)(NC5H5)] (5) and [Cu(An-ONO)(4-NC5H4C(CH3)3)] (6), and two heterobimetallic species, [M(Fc-ONO)(NC5H5)] (M = Ni, 7; Cu, 8), where An-ONOH2 (3) and Fc-ONOH2 (4) are the 1 : 1 condensation products of 2-aminophenol and p-anisoylacetone and ferrocenoylacetone, respectively. These compounds were characterised by microanalysis, FT-IR and X-ray crystallography in the solid state and in solution by UV-vis and 1H and 13C NMR spectroscopy. The crystal structures of 3–5, 7 and 8 have been determined and show for Schiff base complexes 5, 7 and 8 a four-coordinated square-planar environment for nickel and copper ions. The electrochemical behavior of all derivatives 3–8 was investigated by cyclic voltammetry in dichloromethane, and discussed on the basis of DFT-computed electronic structures of the neutral and oxidized forms of the compounds. The second-order NLO responses of 3–8 have been determined by harmonic light scattering measurements using a 10−2 M solution of dichloromethane and working with a 1.91 μm incident wavelength, giving rather high β1.91 values of 350 and 290 × 10−30 esu for the mononuclear species 5 and 6, respectively. The assignment and the nature of the electronic transitions observed in the UV-vis spectra were analyzed using time-dependent (TD) DFT calculations. They are dominated by LMCT, MLCT and π–π* transitions. [ABSTRACT FROM AUTHOR]

This review focuses light on the synthesis, structures and magnetic properties of copper and nickel complexes with salicylaldehyde-based diazine Schiff base ligands. [Display omitted] A variety of di- and poly-nuclear copper and nickel complexes with salicylaldehyde-based azine ligands have been synthesized and their structures and properties have been reported in literature. This review represents an overview on the synthetic strategies, structures and magnetic properties of these complexes. Only those complexes are considered in this review whose X-ray structures are available. Different methods of synthesizing di- and poly-nuclear complexes are discussed. The structures of the complexes and their magnetic properties are compared. [ABSTRACT FROM AUTHOR]

Nine mono-, di- and tetranuclear coordination clusters (M = CoII/III, NiII, CuII) using a monoanionic Schiff base ligand were synthesized and characterized by X-ray crystallography. A series of transformations occur in the ligand in certain compounds for which theoretical studies are presented. Synthetic aspects, topological issues and magnetic studies are discussed. [ABSTRACT FROM AUTHOR]

A series of new Ni(II), Cu(II), Co(II) and Pd(II) complexes were synthesized from the reaction of thioether containing Schiff base ligand with corresponding metal salts by a simple environmentally benign procedure. The molecular formulae of ligand and their complexes are (C 21 H 19 NO 2 S) 2 , 1 , [Ni(C 21 H 18 NO 2 S) 2 ]·CH 3 OH·H 2 O, 2 , [M(C 21 H 18 NO 2 S) 2 ] (3 and 4), where (M = Cu(II) and Co(II)) and [Pd(C 21 H 18 NO 2 SCl)](5). All complexes were characterized by elemental analysis, FT-IR, UV–Vis spectroscopy and single crystal X-ray diffraction analysis. The ligand was characterized by same techniques and with 1 H NMR spectroscopy. X-ray diffraction study reveals that copper complex adopts square planar geometry by coordinating via deprotonated hydroxyl oxygen, azomethine nitrogen of ligand to the copper centre and sulfur atoms remain unligated. As expected, nickel complex acquired a distorted octahedral geometry coordinating via deprotonated hydroxyl oxygen, azomethine nitrogen and thioether sulfur atoms of ligands. Interestingly, one water and one methanol molecule are attached at the out sphere of the nickel complex. Suzuki reaction was carried out in open atmospheric conditions using palladium complex as catalyst. The significant features of the palladium complex catalyzed reaction are good yield, simple workup procedure, easy purification and easy recovery technique of the catalyst. The reported palladium complex is phosphine free, air stable, moisture insensitive. The ligand and complexes show very good biological activities against Mycobacterium abscessus , Bacillus subtilis , Staphylococcus aureus , Proteus vulgaris , Mycobacterium smegmatis and Escherichia coli . [ABSTRACT FROM AUTHOR]

Four macrocyclic Schiff base ligands (L, L, L, and L) have been prepared. In the presence of Copper(II), original macrocycles were converted to the three new binuclear polymeric complexes [CuL](NO), [CuL](NO), and [CuL](NO). But in the presence of Nickel(II), macrocyclic rings remained unchanged and Schiff base complexes of [NiL(CHCN)(CHOH)](ClO) and [NiL](NO) were synthesized. All ligands and their related complexes were characterized by elemental analysis, IR spectroscopy, in the case of ligands H, C NMR and EI-Mass and for [CuL](NO) and [NiL(CHCN)(CHOH)](ClO) complexes X-ray crystal structure determination have been performed. Crystal structure showed 1D zigzag polymer for [CuL](NO) and macrocyclic structure for [NiL(CHCN)(CHOH)](ClO) complexes. The ligands and related polymeric complexes were screened for their antibacterial activities against six bacterial strains and the complexes showed antibacterial effects. [ABSTRACT FROM AUTHOR]

The behaviour of some Schiff bases in the presence of metal ions is very selective in complex formation. In this study, new, selective and easily prepared adsorbent materials have been developed. Multiwalled carbon nanotubes (MWCNTs) are quite suitable as supporting material for preparation of new solid phase adsorbents modified with Schiff bases due to their selective nature. Different Schiff bases were designed and synthesised as adsorbent agents for Ni(II) and Cu(II) ions, according to the literature, and MWCNTs were modified with these Schiff bases. The modification of CNTs was performed by adsorption from the alcoholic solution of Schiff base. The measurements of Ni(II) and Cu(II) ions were carried out using ICP-MS. Different parameters such as pH, model and eluent solution flow rates, eluent type, amount of ligand, sample volume and effect of foreign ions, which have an effect upon recovery of analytes, were investigated. The obtained results indicated that enrichment can be done with six modified adsorbent materials for Cu(II) at pH 9 and two modified adsorbent materials for Ni(II) at pH 8. It was concluded that four adsorbent materials were selective only for the enrichment of Cu(II). Merely one modified adsorbent material was noneligible for the enrichment of Cu(II) and Ni(II). The solid phase adsorbents prepared by modification with two of the Schiff bases used in this study showed an enrichment factor of 80 for both metal ions, whereas the solid phase adsorbents prepared by modification with four of the Schiff bases showed an enrichment factor of 40 for Cu(II) ions. The confirmation of the developed method was tested with certified reference materials with satisfactory results. [ABSTRACT FROM AUTHOR]

This paper explores the synthesis, spectroscopic and structural characterization, linear and nonlinear optical properties, as well as the electrochemical behavior of two series of robust neutral Ni(II)- and Cu(II)-centered organometallic macroacyclic salen-type Schiff base complexes, namely, the 5-nitrosubstituted derivatives M[Fc-C(O)CH = C(CH 3 )N- o -C 6 H 4 -N = CH-(2-O,5-NO 2 -C 6 H 3 )] (M = Ni ( 2 ), Cu ( 3 )), and their 3,5-difluorosubstituted analogues M[Fc-C(O)CH = C(CH 3 )N- o -C 6 H 4 -N = CH-(2-O-3,5-F 2 -C 6 H 2 )] (M = Ni ( 4 ), Cu ( 5 ); Fc = ferrocenyl = (η 5 -C 5 H 5 )Fe(η 5 -C 5 H 4 ))). Compounds 2 – 5 were synthesized in good yields (75–87%) in refluxing ethanol for 4 h, via template reaction by condensation of the tridentate half-unit metalloligand Fc-C(O)CH = C(CH 3 )-N(H)- o -C 6 H 4 NH 2 ( 1 ) with 5-nitrosalicylaldehyde and 3,5-difluorosalicylaldehyde, respectively, in the presence of hydrated nickel(II) and copper(II) acetate salts, respectively. Their composition and identity were inferred from elemental analysis, FT-IR, UV–Vis, and multinuclear NMR spectroscopy. Single crystal X-ray diffraction analysis of the two 3,5-difluorosubstituted compounds 4 and 5 indicates a slightly bowed structure of the unsymmetrical Schiff base scaffold. Both Ni 2+ and Cu 2+ ions are tetracoordinated in a distorted square planar environment, with two nitrogen atoms and two oxygen atoms as donors. The electrochemical behavior of the four binuclear complexes was investigated by cyclic voltammetry, showing greater anodic shifts of the reversible redox process ascribed to the Fe II /Fe III couple of the ferrocenyl donor fragment of the 5-nitrosubstituted derivatives compared to their 3,5-difluorosubstituted counterparts. Harmonic Light Scattering measurements showed that compounds 2 – 5 exhibited rather high second-order nonlinear responses, found between 200 and 267 × 10 − 30 esu, establishing a good correlation between redox potentials and the hyperpolarizability β 1.91 values. [ABSTRACT FROM AUTHOR]

[Display omitted] • Energy values for the binding of copper and nickel complexes were estimated. • Dissociation enthalpy of the metal–ligand bond comparison is Ni − L > Cu − L > Zn − L. • Flexibility structure vs methylene groups chain are expressed by energetic results. • The computational estimates are in quite good agreement with the experimental results. This work constitutes a new contribution for understanding the relationship between the metal–ligand bonding and, indirectly, the inherent reactivity of metallic complexes with tetradentate N 2 O 2 Schiff base ligands, being reported the energetic characterization of two transition metal complexes – (N,N '́-bis(salicylaldehydo)tetramethylenediiminate)nickel(II) and (N,N '-bis(salicylaldehydo)propylenediiminate)copper(II). The standard molar enthalpies of formation of these complexes were determined by solution-reaction calorimetry measurements. Their standard molar enthalpies of sublimation, at T = 298.15 K, were obtained by an effusion method. From these studies, the gas-phase enthalpies of formation of Ni(II) and Cu(II) complexes, at T = 298.15 K, were derived. Differences between the metal–ligand and mean hydrogen-ligand bond dissociation enthalpies were derived and discussed in structural terms, in comparison with identical parameters for complexes of the same metals with analogous tetradentate Schiff bases. High-level quantum chemical calculations have also been conducted, complementing the results obtained experimentally. [ABSTRACT FROM AUTHOR]

Oligomeric main-chain Schiff-base compounds 4 and 5 have been synthesized by the trans-esterification of their respective doubly functionalized monomeric precursors [M{(η5-C5H5)Fe(η5-C5H4)C(=O)CH=C(4-C6H4OH)NCH2CH2N=CH-(2-O,4-CO2H-C6H3)}] [M = Ni ( 2), Cu ( 3)] in dmf. The new compounds were characterized by elemental analysis, FTIR and multidimensional NMR spectroscopy, mass spectrometry, and cyclic voltammetry. Compounds 2, 3, and 6, the corresponding amide of 2, were characterized by X-ray structural investigation. Gel permeation chromatography established that oligomers 4 and 5 are formed of approximately six monomeric units, and differential scanning calorimetry and thermal gravimetric analysis indicated that they are thermally stable with decomposition temperatures exceeding 230 °C. Harmonic light scattering measurements showed that compounds 2- 5 exhibit rather high second-order nonlinear responses, between 224 × 10-30 and 399 × 10-30 esu, with hyperpolarizability β1.91 values that increase significantly on passing from the monomeric to the oligomeric species. [ABSTRACT FROM AUTHOR]