Mononuclear Nickel Research Articles

Synthesis, crystal structure, Hirshfeld surface analysis, DNA binding, DNA cleavage activity and molecular docking of a new Schiff base nickel(II) complex

A mononuclear nickel(II) complex, [Ni(o-van-tris)2]·2H2O (o-van-tris = Schiff base derived from o-vanillin and tris(hydroxymethyl)aminomethane), has been synthesized and structurally characterized. The single crystal structure shows a distorted octahedron geometry coordinated with Ni(II) atom, and 2 D plane structure has formed by O–H···O hydrogen bond interactions. An analysis to ascertain intermolecular interactions of the complex was performed based on the Hirshfeld surfaces and their associated two-dimensional fingerprint plots. The binding properties of the nickel(II) complex with CT-DNA have been investigated by spectroscopic methods and molecular docking. Absorption and fluorescence spectral studies reveal that the complex interacts with DNA through hydrogen bond and hydrophobic interactions with the DNA base pairs. Molecular docking studies show that the complex effectively docks in the major groove of DNA. The DNA cleavage experiment was performed by gel electrophoretic assay, indicating that DNA cleavage activity of the complex is concentration dependent and much sensitive to ionic strength. The efficient cleavage mediated via hydrolytically cleaving pathway. Communicated by Ramaswamy H. Sarma

A new mononuclear nickel complex with 5,5′-dimethyl-2,2′-bipyridine: Synthesis, structural investigation and catalytic properties

The new [Ni(dmbpy)(H2O)4]SeO4 complex (dmbpy = 5,5′-dimethyl-2,2′-bipyridine or C12H12N2), based on mononuclear nickel(II) and bi-atomic bridging ligands has been successfully synthesized by hydrothermal method. The crystals are characterized by X-ray single-crystal diffraction, crystallizing in the monoclinic system, space group P21/c. Their crystal structure consists of metallic cations octahedrally coordinated by four water molecules and two nitrogen atoms coming from the organic molecule [NiN2O4], and a selenate anion (SeO4)2-. Their crystal packing is ensured by a three-dimensional network of O-H…O hydrogen bonds between the cation and anion moieties, and π … π interactions between the pyridine rings of the organic moieties of the same layer. The thermal analysis discloses dehydration between 148 °C and 210 °C, leading to an anhydrous compound [Ni(dmbpy]SeO4. The study of vibrational absorption and Raman scattering spectra allows bringing additional information to those obtained by X-ray diffraction. The optical band gap was calculated from the UV–Vis absorbance spectra using classical Tauc relation which was found to be 3.58 eV. The catalytic evaluation of [Ni(dmbpy)(H2O)4]SeO4 on Heck and Sonogashira coupling reactions, activated by ultrasonic irradiation, results in encouraging yields for a very short times with a remarkable selectivity of the form (E) with respect to (Z) during the arylation of styrene, making this complex a promising catalyst for both types of reactions. The coupling products of the Heck and Sonogashira coupling reaction ((Z)-/(E)- Stilbene and Diphenylacetylene, respectively) were examined by 13C NMR and 1H NMR. These spectroscopic measurements provide extremely valuable information on the structure of the molecules obtained.

Trinuclear copper and mononuclear nickel complexes of oxime containing Schiff bases: Single crystal X-ray structure, catecholase and phenoxazinone synthase activity, catalytic study for the homocoupling of benzyl amines

Here we report the synthesis and characterisation of one trinuclear copper complex, [Cu3L3O]ClO4 (1), and one nickel complex, [Ni(L′H)2(dmso)2](ClO4)2) (2), with the Schiff base ligands (3Z)-3-((Z)-(1-(thiophen-2-yl)ethylidene)hydrazono)butan-2-one oxime (LH) and 1-(pyridin-2-yl)ethylidene)hydrazono)butan-2-one oxime (ĹH). Single crystal X-ray structures have been described for the ligand LH and the complexes 1 and 2. 1 shows high catecholase activity (kcat = 8.14 × 102 h−1 in MeOH) using 3,5-di-tert-butylcatechol as the substrate in methanol medium. 2 shows phenoxazinone synthase activity with a moderate value of kcat = 63.11 h−1 in dimethyl sulfoxide. This is the first report for phenox-azinone synthase activity by a nickel complex containing a ligand with oxime functionality. 1 has also been tested as a catalyst for the synthesis of benzylimine and substituted benzylimines from the corresponding amines. Substrates with electron withdrawing halo-substituted benzylamines undergo quantitative conversions to the corresponding benzylimines, whereas electron donating groups on the aromatic ring yielded lower conversions.

Structure, function, and biosynthesis of nickel‐dependent enzymes

Nickel enzymes, present in archaea, bacteria, plants, and primitive eukaryotes are divided into redox and nonredox enzymes and play key functions in diverse metabolic processes, such as energy metabolism and virulence. They catalyze various reactions by using active sites of diverse complexities, such as mononuclear nickel in Ni-superoxide dismutase, glyoxylase I and acireductone dioxygenase, dinuclear nickel in urease, heteronuclear metalloclusters in [NiFe]-carbon monoxide dehydrogenase, acetyl-CoA decarbonylase/synthase and [NiFe]-hydrogenase, and even more complex cofactors in methyl-CoM reductase and lactate racemase. The presence of metalloenzymes in a cell necessitates a tight regulation of metal homeostasis, in order to maintain the appropriate intracellular concentration of nickel while avoiding its toxicity. As well, the biosynthesis and insertion of nickel active sites often require specific and elaborated maturation pathways, allowing the correct metal to be delivered and incorporated into the target enzyme. In this review, the phylogenetic distribution of nickel enzymes will be briefly described. Their tridimensional structures as well as the complexity of their active sites will be discussed. In view of the latest findings on these enzymes, a special focus will be put on the biosynthesis of their active sites and nickel activation of apo-enzymes.

Formation and decomposition of Nickel(II) complexes with tridentate aminoether or aminoalcohol ligands

Tridentate aminoalcohol and aminoether ligands, iminodiethanol [H2(ide)] and bis(2-methoxyethyl)amine [bmoen], form mononuclear nickel(II) complexes, [Ni{H2(ide)}2][BPh4]2·3.5H2O (1), [Ni{H2(ide)}2][BPh4]2·BPh(ide)·(CH3)2CHOH (2), [Ni{H(ide)}{H2(ide)}][BPh4]·3CH3OH (3), and [Ni(bmoen)2][BPh4]2·H2O (4). In the decomposition procedure of 4 in dimethylformamide (dmf), mononuclear nickel(II) complexes, [Ni(bmoen)2(dmf)][BPh4]2·dmf (5), [Ni(bmoen)(dmf)3][BPh4]2·0.5H2O (6), and [Ni(dmf)6][BPh4]2 (7) were obtained. Since the crystal structures were unknown for 1, 4, and 6, each complex-cation structure was predicted on the basis of the term-splitting in the electronic spectra. The [Ni{H2(ide)}2]2+ complex cation in 1 and the [Ni(bmoen)2]2+ complex cation in 4 were predicted to be cis-fac structures, and the [Ni(bmoen)(dmf)3]2+ complex cation in 6 was predicted to be a fac structure. The predicted structures were consistent with the result of conformational analysis on the basis of the DFT calculation.

Capturing the Role of Phosphate in the Ni‐PY5 Catalyzed Water Oxidation

AbstractThe mononuclear Nickel complex Ni‐PY5 [PY5=2, 6‐bis(1,1‐bis(2‐pyridyl)ethyl)pyridine] has been disclosed to catalyze water oxidation electrochemically with an applied potential of 1.5 V at pH 10.8 in aqueous phosphate buffer solution. Density functional calculations were used to elucidate the reaction mechanism of water oxidation catalyzed by this nickel complex and to capture the role of the phosphate. The calculations demonstrated that the oxidations of the starting [OH2−NiII‐PY5]2+ complex by two sequential proton‐coupled electron‐transfer processes lead to the formation of a key intermediate [O=NiIV‐PY5]2+. O−O bond formation then takes place through a water nucleophilic attack on the high‐valent NiIV=O moiety of the catalyst, facilitated by a hydrogen phosphate anion, with a total barrier of 11.5 kcal mol−1. The calculated barrier agrees very well with the experimental turnover frequency of about 2000 s−1, which corresponds to a barrier of 12.9 kcal mol−1. The calculated deuterium kinetic isotope effect of 1.99 is also in excellent agreement with the experimental value of 2.06. Finally, we also predicted the catalytic activity of other PY5‐based first‐row transition metal complexes, namely, involving Mn, Fe, Co and Cu. The calculations showed that the Mn, Fe, Co complexes have higher barrier for water oxidation, while the Cu complex has lower barrier and higher water oxidation activity compared with the Ni complex.

Synthesis and structural characterization of a linkage isomer to a mononuclear Nickel(II) complex: Experimental and computational depiction of phosphoesterase efficiency

Synthesis and structural characterization of a linkage isomer, bis(2,2′-dipyridylamine)dithiocyanato(k-S)nickel(II), [Ni(dpa)2(k-SCN)2] (1) of a previously reported Ni(II) complex, [Ni(dpa)2(k-NCS)2] (dpa = 2,2′-dipyridylamine; SCN = thiocyanate) has been reported herein. X-ray structural analysis of 1 reveals that Ni(II) complex crystallizes in monoclinic system with P21/c space group and exists in trans configuration. The coordination geometry for 1 adopts a tetragonal structure. Supramolecular aspects of the Ni(II) complex indicate that N atom of SCN behaves as a donor and H atom of dpa ligand acts as a receptor in growing 1D crystalline structure along b axis in solid state. The aromatic rings in 1 prefer to exist in face-centred stacking with interplanar distance of 3.426 Å and supports strongly to form self-assembled 3D crystalline architecture. Hirshfeld surface analysis further recommends this crystalline assembly in solid state. 1 exhibits promising phosphatase activity towards disodium(4-nitrophenyl)phosphate (PNPP) in aqueous-methanolic medium. The hydrolytic phosphatase efficiency for 1 is determined in terms of turnover number (kcat) as 3.38 × 104 h−1. Moreover, density functional theoretical computations closely replicate the structural parameters and spectroscopic behaviour of 1.

Impacts of multi-element flame retardants on flame retardancy, thermal stability, and pyrolysis behavior of epoxy resin

N-substituted bis(diphenylphosphanyl)amine RN(PPh2)2 (PNP; R = CH2CH2CH2Si(OEt)3) and its mononuclear nickel(II) ethanedithiolate complexe RN(PPh2)2Ni(SCH2CH2S) (PNS; R = CH2CH2CH2Si(OEt)3) were prepared and used as multi-element flame retardants for epoxy resin (EP). Results of thermogravimetric analysis (TGA) revealed that the incorporation of PNP or PNS restrained the decomposition of EP and also improved the stability of char residues. Moreover, results of limited oxygen index (LOI), vertical burning test (UL-94), microscale combustion calorimeter (MCC), and cone calorimeter tests proved that both PNP and PNS endowed EP with good flame retardancy. Different chemical structures and action mechanisms of PNP and PNS resulted in different degrees of flame retardancy for EP. Although EP/PNP samples caused a little higher LOI values than those of EP/PNS ones, the incorporation of 7 wt% PNS endowed EP with a lower peak of heat release rate (PHRR) and total smoke production (TSP), thereby indicating better flame-retardant and smoke suppression effects. Furthermore, thermogravimetry-Fourier transform infrared spectroscopy (TG-FTIR) and pyrolysis gas chromatography/mass spectrometry (Py-GC/MS) were employed to analyze the pyrolysis behavior of EPs and flame retardants. The morphologies of char layers for EPs were examined by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). In comparison to PNP, PNS promoted the formation of a stronger protective char barrier comprising by P/Si/S/Ni elements and also restrained the effects of flammable gases on EP.

Preparation, Structure, Photoluminescent and Semiconductive Properties, and Theoretical Calculation of a Mononuclear Nickel Complex with 3-Hydroxy-2- Methylquinoline-4-Carboxylato Ligand

A novel nickel complex with mixed ligands [Ni(L)2(EtOH)2(MeOH)2] (HL = 3-hydroxy-2-methylquinoline-4-carboxylic acid) has been synthesized through solvothermal reaction and its crystal structure was determined by single-crystal X-ray diffraction technique. Single-crystal X-ray diffraction analyses reveals that the title compound crystallizes in the triclinic system of the P-1 space group, and exists as isolated mononuclear complex. The intermolecular hydrogen bonds lead to the formation of chains, and the layered supramolecular structure is formed by the strong ααααα stacking interactions. Solid-state photoluminescent characterization reveals that the title compound has an emission in the green region. Time-dependent density functional theory (TDDFT) calculation shows that the nature of the photoluminescence of the title compound originates from the ligand-to-ligand charge transfer (LLCT; from the HOMO of the p-orbital of ligand HMCA to the LUMO of the oxygen atoms). A wide optical band gap of 2.25 eV is found by the solid-state UV/vis diffuse reflectance spectrum.

Syntheses, characterization, crystal structures and Jack bean urease inhibitory activities of ZnII, CoII/III and NiII complexes derived from reduced Schiff base ligand

A series of new ZnII, CoII/III and NiII complexes derived from reduced Schiff base 6,6′-((propane-1,3-diylbis(azanediyl))bis(methylene))bis(2-ethoxyphenol) (H2L), [Zn3L2(N3)2] (1), [Co2L(N3)2(CH3COO)]·CH3OH (2) and [Ni(HL)(OH2)(CH3OH)]·ClO4 (3), were prepared and characterized by physico-chemical methods. Crystal structures of the complexes were determined by single crystal X-ray diffraction. Complex 1 is a trinuclear zinc(II) compound. Complex 2 is a dinuclear cobalt(II/III) compound. Complex 3 is a mononuclear nickel(II) compound. The cobalt complex and the nickel complex have effective urease inhibitory activities, with IC50 values of 19.8 and 11.6 μmol·L−1, respectively. However, the zinc complex 1 has no such activity. Molecular docking study of complexes 2 and 3 with the active center of Jack bean urease was studied.

Crystal Structure of Mono- and Trinuclear Ni(II) Complexes with Bis-Azomethine Based on 2-Amino-3-Formylpyridine

The structure of a new mononuclear nickel(II) complex with bis-azomethine [Ni(H2L)]+ · CH3COO– · H2O, resulting from condensation of 1,3-diaminopropan-2-ol with 2-amino-3-formylpyridine (H3L), was studied by X-ray diffraction (CIF files CCDC nos. 1562927, 1562928). Apart from the mononuclear complex, the reaction gave a minor amount of the trinuclear metal chelate [Ni3L'(H2O)2]+ · (CH3COO)– · CH3OH · H2O, where L' is N5O2-donor ligand containing two 3-(((2-aminopyridin-2-yl)methylene)amino)-1-aminopropan-2-ol moieties linked by a 2-aminopyridine-3-methylene group.

Synthesis, Characterization, Thermal and Non-Isothermal Degradation Studies of Two Mononuclear Nickel and Copper Complexes Containing Schiff Base Moiety

Synthesis, Characterization, Thermal and Non-Isothermal Degradation Studies of Two Mononuclear Nickel and Copper Complexes Containing Schiff Base Moiety

Tetrazolo[1,5-a]pyrimidine-based metal(II) complexes as therapeutic agents: DNA interaction, targeting topoisomerase I and cyclin-dependent kinase studies

A series of mononuclear nickel(II), copper(II) and zinc(II) complexes of the type [ML1‒3Cl2] (1–9) have been synthesized and characterized. All the complexes interact with CT–DNA through groove mode of binding and bring about prominent nuclease activity on plasmid DNA. The complexes strongly inhibit the topoisomerase I, and also strongly interact with cyclin-dependent kinase receptor. The cytotoxicity activity were assessed aganist three human cancer cell lines such as lung (A549), cervical (HeLa) and colon (HCT–15), in which the complex 5 shows highest activity against the colon (HCT-15) cancer cell. The apoptotic studies were also reported.

Synthesis, physicochemical and biological characterization of Ni(II) complex with imidazole-4-acetate anion as new antifungal agent

The neutral mononuclear nickel(II) complex with an imidazole-4-acetate anion (iaa), having the formula $$[\hbox {Ni(iaa)}_{2}(\hbox {H}_{{2}}\hbox {O})_{2}]{\cdot }\hbox {H}_{{2}}\hbox {O}$$ , was characterized by single-crystal X-ray diffraction, IR, farIR, UV-Vis-NIR spectra and magnetic measurements. The imidazole-4-acetate anion in this complex is a chelating ligand where an azomethine nitrogen atom of the imidazole ring and carboxylate oxygen atoms are donor atoms. The immediate environment of the central nickel(II) ion is described by distorted cis-octahedron ( $$\hbox {NiN}_{{2}}\hbox {O}_{4}$$ chromophore). The analysis of biological properties of $$[\hbox {Ni(iaa)}_{2}(\hbox {H}_{{2}}\hbox {O})_{2}] {\cdot } \hbox {H}_{{2}}\hbox {O}$$ complex has shown that this complex at non-cytotoxic concentration against normal human BEAS-2B cell has antifungal properties. The biophysical studies have shown that of [ $$[\hbox {Ni(iaa)}_{2}(\hbox {H}_{{2}}\hbox {O})_{2}] {\cdot } \hbox {H}_{{2}}\hbox {O}$$ ] interacts with DNA without degradation and with BSA as a model protein. SYNOPSIS Synthesis and characterization of neutral mononuclear nickel(II) complex with imidazole-4-acetate anion (iaa) is reported. The results suggest that $$[\hbox {Ni(iaa)}_{2}(\hbox {H}_{{2}}\hbox {O})_{2}] {\cdot } \hbox {H}_{{2}}\hbox {O}$$ complex interacts weakly with DNA via weak intercalative or groove binding mode. The ability of nickel(II) complex to bind to protein (BSA) has been confirmed in this study. From biological point of view, $$[\hbox {Ni(iaa)}_{2}(\hbox {H}_{{2}}\hbox {O})_{2}] {\cdot } \hbox {H}_{{2}}\hbox {O}$$ complex has antifungal properties at non-cytotoxic concentration against normal human cell line.

A transparent electrode with water-oxidizing activity

Hydrogen production by water splitting is a promising method to store energy. Water-oxidation reaction is a bottleneck in water-splitting systems. Herein, a mononuclear nickel(II) phosphine complex with 1,2-bis(dicyclohexylphosphino)ethane ligand, was synthesized and characterized by X-ray crystallography method. The water-oxidizing catalyst under the electrochemical condition was studied. The role of Ni compound for the water-oxidation reaction on the surface of fluorine-doped tin oxide as one of the true catalysts was investigated by the electrochemical methods and Scanning Electron Microscopy coupled with Energy Dispersive X-ray (SEM/EDX) Spectroscopy. The big ligand around the Ni ion causes a very small size of Ni-based particles on the surface of the electrode, which are the active catalysts for the water-oxidation reaction. Such small nanosized Ni-based compounds are transparent and have no effect on the transparency of the obtained fluorine-doped tin oxide. Thus, it is a promising method to synthesize a transparent fluorine-doped tin oxide with water-oxidizing activity.

Dual-site aqua mononuclear nickel(II) complexes of non-heme tetradentate ligands: Synthesis, characterization and reactivity

Mononuclear compounds [Ni(BQCNMe2)(H2O)2](ClO4)21 and [Ni(BQCNH2)(H2O)2](ClO4)22 of N,N′-dimethyl-N,N′-di(quinolin-8-yl)cyclohexane-1,2-diamine (BQCNMe2) and N,N′-di(quinolin-8-yl)cyclohexane-1,2-diamine (BQCNH2) were synthesised and characterized by elemental analysis, IR/UV-Vis spectroscopy, cyclic voltammetry (CV)/differential pulse voltammetry (DPV) and X-ray powder pattern. [Ni(BQCNMe2)(en)](ClO4)23 and [Ni(BQCNMe2)(phen)](ClO4)24 were prepared by reacting 1 with ethylenediamine (en) and 1,10-phenanthroline (phen) respectively while [Ni(BQCNH2)(en)](ClO4)25 and [Ni(BQCNH2)(phen)](ClO4)26 were obtained from the reaction of 2. Compounds [Ni(BQENMe2)(en)](ClO4)27 and [Ni(BQENH2)(en)](ClO4)2.CH3CN 8 (BQENMe2 is N,N′-dimethyl-N,N′-bis(8-quinolyl)ethane-1,2-diamine) and BQENH2 is N,N′-bis(8-quinolyl)ethane-1,2-diamine) were synthesised similarly. Compounds 6 and 8 were characterized by single crystal X-ray diffractometry and their structural features are presented. The reactivity of 2 with H2O2/base was investigated. A new peak at 570 nm in the UV-Vis spectrum corresponding to 2a was obtained which on addition of 2-phenylpropionaldehyde (2-PPA) decays giving pseudo-first order rate constant of 9.2 × 10−3 s−1 and acetophenone as a major product. The catalytic hydroxylation of cumene and ethylbenzene by 1 and 2 in the presence of meta-chloroperbenzoic acid (m-CPBA) was investigated.

Electrochemical Synthesis, Properties, and Structure of 1,10-Phenanthroline Adducts of Mononuclear Copper, Cobalt, and Nickel Chelates in the N,N,O-Ligand Environment

1,10-Phenanthroline (Phen) adducts [M(L)Phen] in copper(II), cobalt(II), and zinc(II) chelates based on N,N,O-tridentate tosylamino-functionalized pyrazole-containing Schiff base (H2L), resulting from condensation of 2-tosylaminoaniline with 3-methyl-1-phenyl-4-formylpyrazol-5-ol, were obtained by electrosynthesis. The composition and structure of the mixed-ligand complexes were confirmed by elemental analysis, IR spectroscopy, and magnetochemical measurements. The structures of azomethine H2L and mixed-ligand copper(II) complex were determined by X-ray diffraction.

Synthesis of water-soluble bis-N,O-chelate nickel(II) complexes based on new ligands – P-pyridyl-containing phospholane oxides

A series of new N,O-hybrid ligands was synthesized by oxidation of pyridyl-substituted phospholanes. These ligands were employed in the first synthesis of water-soluble mononuclear nickel(II) complexes [NiL2(H2O)2](BF4)2 and [NiL2(MeCN)2](BF4)2. Physicochemical properties and crystalline structures of the synthesized compounds were thoroughly studied.

5-Methyl-2-hydroxy-acetophenone-S-methyl-thiosemicarbazone and its nickel-PPh3 complex. Synthesis, characterization, and DFT calculations

A tridentate Schiff base ligand (5-methyl-2-hydroxy-acetophenone-S-methyl-thiosemicarbazone, H2L) and its mononuclear nickel complex, [NiL(PPh3)], were obtained and characterized by spectroscopic techniques. Structural analysis of the compounds was supported by complementing crystallographic studies. The X-ray data related to molecular geometries was used in the DFT/B3LYP calculations with 6-311G (d, p) and LANL2DZ (for nickel atom) basis sets. Atomic charge distribution data indicated that the negative charges of free thiosemicarbazidato ligand were transferred to nickel (II) by the formation of the metal complex. To understand the nucleophilic or electrophilic reaction capabilities the ligand and nickel complex, the molecular electrostatic potential (MEP) and electrostatic potential (ESP) analyses have performed.

Synthesis, X-ray Structural Characterization, and DFT Calculations of Mononuclear Nickel(II) Complexes Containing Diamine and Methacrylate Ligands.

The mononuclear Ni(II) complexes [Ni(en)2(H2O)2](MAA)2 (1) and [Ni(pn)2(MAA)2] (2), where MAA, en and pn are methacrylate, ethylendiamine and 1,3-propylendiamine, respectively, have been synthesized and characterized by elemental analysis, FT-IR and UV�Vis spectroskopy. Structures of the complexes have been determined by single-crystal X-ray diffraction analyses. In the nickel(II) complexes 1 and 2 nickel(II) ion is six-coordinate and has a distorted octahedral geometry. Ni(II) is bonded to four nitrogen atoms of the two diamines and additionally to two oxygen atoms of aqua ligand in 1, and two oxygen atoms of methacrylate ligands in 2. The theoretical geometries of the studied compounds have been calculated by means of density functional theory (DFT) at the B3LYP/6-311+G(d,p)/LanL2DZ level and considering effective core potential (ECP). The comparison of the results indicates that the employed DFT method yields good agreement with experimental data.