Macrocyclic Nickel Research Articles

Highly active macrocyclic nickel(II) complex for hydrogen evolution reaction in neutral aqueous conditions

Hydrogen (H2) production via water splitting under completely aqueous conditions particularly using an earth-abundant component for both half reactions is very appealing and may reduce our dependence on fossil fuels. In this work, we present a water-soluble molecular nickel(II) complex bearing a macrocyclic N‒heterocyclic carbene (NHC)/pyridine hybrid ligand, ([NiL](PF6)2 (L = bis(2‒pyridyl-methylimidazolylidene)methane as a catalyst for hydrogen evolution reaction (HER) under completely aqueous conditions. The catalyst displayed an outstanding catalytic activity for HER in a phosphate electrolyte of neutral pH, as established by a series of techniques. Long-term (11 h) bulk electrolysis at 0.88 V overpotential provides a maximum of 173.5C charge and total ca. 165.08 μmol (∼15 μmol per hour) H2 with Faradaic efficiency of 98%, while without a catalyst less than 3C was produced within the same time. To the best of our knowledge, the investigation of water reduction with Ni–NHC type catalyst under aqueous conditions has not been reported to date.

Improved Electrochemical Hydrogen Peroxide Detection Using a Nickel(II) Phthalimide-Substituted Porphyrazine Combined with Various Carbon Nanomaterials.

A metal-free porphyrazine derivative with peripheral phthalimide substituents was metallated with a nickel(II) ion. The purity of the nickel macrocycle was confirmed using HPLC, and characterized by MS, UV-VIS, and 1D (1H, 13C) and 2D (1H-13C HSQC, 1H-13C HMBC, 1H-1H COSY) NMR techniques. The novel porphyrazine was combined with various carbon nanomaterials, such as carbon nanotubes-single walled (SWCNTs) and multi-walled (MWCNTs), and electrochemically reduced graphene oxide (rGO), to create hybrid electroactive electrode materials. The carbon nanomaterials' effect on the electrocatalytic properties of nickel(II) cations was compared. As a result, an extensive electrochemical characterization of the synthesized metallated porphyrazine derivative on various carbon nanostructures was carried out using cyclic voltammetry (CV), chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS). An electrode modified with carbon nanomaterials GC/MWCNTs, GC/SWCNTs, or GC/rGO, respectively, was shown to have a lower overpotential than a bare glassy carbon electrode (GC), allowing for the measurement of hydrogen peroxide in neutral conditions (pH 7.4). It was shown that among the tested carbon nanomaterials, the modified electrode GC/MWCNTs/Pz3 exhibited the best electrocatalytic properties in the direction of hydrogen peroxide oxidation/reduction. The prepared sensor was determined to enable a linear response to H2O2 in concentrations ranging between 20-1200 µM with the detection limit of 18.57 µM and sensitivity of 14.18 µA mM-1 cm-2. As a result of this research, the sensors produced here may find use in biomedical and environmental applications.

Perfluorocycloparaphenylenes

Perfluorinated aromatic compounds, the so-called perfluoroarenes, are widely used in materials science owing to their high electron affinity and characteristic intermolecular interactions. However, methods to synthesize highly strained perfluoroarenes are limited, which greatly limits their structural diversity. Herein, we report the synthesis and isolation of perfluorocycloparaphenylenes (PFCPPs) as a class of ring-shaped perfluoroarenes. Using macrocyclic nickel complexes, we succeeded in synthesizing PF[n]CPPs (n = 10, 12, 14, 16) in one-pot without noble metals. The molecular structures of PF[n]CPPs (n = 10, 12, 14) were determined by X-ray crystallography to confirm their tubular alignment. Photophysical and electrochemical measurements revealed that PF[n]CPPs (n = 10, 12, 14) exhibited wide HOMO–LUMO gaps, high reduction potentials, and strong phosphorescence at low temperature. PFCPPs are not only useful as electron-accepting organic materials but can also be used for accelerating the creation of topologically unique molecular nanocarbon materials.

Coordination Polymers of the Macrocyclic Nickel(II) and Copper(II) Complexes with Isomeric Benzenedicarboxylates: The Case of Spatial Complementarity between the Bis-Macrocyclic Complexes and o-Phthalate

Starting from isomeric benzenedicarboxylate dianions, phthalate (1,2-bdc2–), isophthalate (1,3-bdc2–), and terephthalate (1,4-bdc2–), and the nickel(II) and copper(II) macrocyclic cations of 3R-1,3...

Effect of the Structure of Nickel(II) Coordination Polymers as Precursors of Nickel Hydroxide Coatings on their Structure and Electrocatalytic Properties in The Oxidation of Urea in Basic Solutions

The structure of coordination polymers formed by a macrocyclic nickel(II) complex and aromatic carboxylates as precursors of nickel hydroxide coatings was shown to be an essential factor determining their phase composition and electrochemical characteristics as well as electrochemical properties in the oxidation of urea in basic solutions accompanied by the release of molecular hydrogen.

Identification of four isomers of Dihydroxynaphthalene by using a Briggs-Rauscher oscillating system

A novel method for identification of four isomers of dihydroxynaphthalene (DHN) was reported by their different perturbation effects on a Briggs-Rauscher (BR) oscillating system. In the system, macrocyclic nickel (II) complex NiL(ClO4)2 is used as the catalyst, where the ligand L in the complex is 5,7,7,12,14,14‑hexemethyl‑1,4,8,11‑tetraazacyclotetradeca‑4,11‑diene. By putting equal amount of the same concentrations of four isomers (1,4‑dihydroxynaphthalene (1,4-DHN), 1,5‑dihydroxynaphthalene (1,5-DHN), 2,3‑dihydroxynaphthalene (2,3-DHN) and 2,7‑dihydroxynaphthalene (2,7-DHN)) into BR system, the system could or couldn't be perturbed, being reflected in quite different oscillating behaviors after addition of isomers. These four isomers were identified in their concentration range of 5.0 × 10−6 to 2.5 × 10−4 mol/L. An explanation of such perturbation mechanism is that, 1,4-DHN couldn't be oxidized by BR matrix, but 1,5-DHN, 2,3-DHN and 2,7-DHN could be oxidized by HOO to yield 5‑Hydrox‑1,4‑naphthoquinone, phthalic acid and 6,7‑dihydroxyperylene‑1,12‑quinone (DHPQ), respectively.

Chiral Recognition of Racemic Proline based on Chiral Macrocyclic Nickel(II) Complex: Synthesis and Crystal Structures

The reactions of dl‐proline with chiral macrocyclic NiII complex [Ni(SS‐L)](ClO4)2 in acetonitrile/water gave a six‐coordinate enantiomer formulated as [Ni(SS‐L)(l‐Pro)](ClO4)2·H2O (1). Another enantiomer of [Ni(RR‐L)(d‐Pro)](ClO4)2·H2O (2) was obtained when [Ni(RR‐L)](ClO4)2 was used (L = 5,5,7,12,12,14‐hexamethyl‐1,4,8,11‐tetraazacyclotetradecane, Pro = proline). Single‐crystal X‐ray diffraction analyses of complexes 1 and 2 revealed that the NiII atom has a distorted octahedral coordination arrangement, being coordinated by four nitrogen atoms of L in a folded configuration, plus two carboxylate oxygen atoms of proline in mutually cis positions. Complexes 1 and 2 are supramolecular stereoisomers, which are constructed with hydrogen bonding linking of [Ni(SS‐L)(l‐Pro)]2+ and [Ni(RR‐L)(d‐Pro)]2+ monomers to form one‐dimensional zigzag chains. The homochiral natures of complexes 1 and 2 were confirmed by solid CD spectroscopy.

A nickel catalyzed acceptorless dehydrogenative approach to quinolines.

A general, efficient and environmentally benign, one-step synthesis of substituted quinoline derivatives was achieved by acceptorless dehydrogenative coupling of o-aminobenzylalcohols with ketones and secondary alcohols catalyzed by a cheap, earth abundant and easy to prepare nickel catalyst [Ni(MeTAA)], featuring a tetraaza macrocyclic ligand (tetramethyltetraaza[14]annulene (MeTAA)). A wide variety of substituted quinolines were synthesized in high yields starting from readily available o-aminobenzylalcohols and ketones or secondary alcohols. A few controlled reactions were carried out to establish the acceptorless dehydrogenative nature of the reactions.

Capped Mesoporous Silica Nanoparticles for the Selective and Sensitive Detection of Cyanide.

The development of easy and affordable methods for the detection of cyanide is of great significance due to the high toxicity of this anion and the potential risks associated with its pollution. Herein, optical detection of cyanide in water has been achieved by using a hybrid organic-inorganic nanomaterial. Mesoporous silica nanoparticles were loaded with [Ru(bipy)3 ]2+ , functionalized with macrocyclic nickel(II) complex subunits, and capped with a sterically hindering anion (hexametaphosphate). Cyanide selectively induces demetallation of nickel(II) complexes and the removal of capping anions from the silica surface, allowing the release of the dye and the consequent increase in fluorescence intensity. The response of the capped nanoparticles in aqueous solution is highly selective and sensitive towards cyanide with a limit of detection of 2 μm.

Further insight into the electrocatalytic water oxidation by macrocyclic nickel(ii) complexes: the influence of steric effect on catalytic activity

Macrocyclic nickel(ii) complexes with axially oriented methyl groups can impose a steric effect on the axial position of the in situ formed NiIII center, which results in higher NiIII/II oxidation potentials and suppresses the axial coordination of phosphate anions with the NiIII center.

Encapsulation of a hexaaza macrocyclic nickel(ii) complex in zeolite Y: an experimental and theoretical investigation

In this study, a 1,8-dimethyl-1,3,6,8,10,13-hexaazacyclotetradecane nickel(ii) complex was encapsulated in the supercages of zeolite Y for the photocatalytic removal of methylene blue under visible light.

Synthesis, characterization, and crystal structure of macrocyclic nickel(II) complexes bearing a,e-cis-1,4-chdc and e,e-trans-1,4-chdc (chdc = cyclohexanedicarboxylate) ligands

ABSTRACTTwo macrocyclic nickel(II) complexes, [Ni(L)(a,e-cis-1,4-chdc)]·4H2O (1) and [{Ni(L)(H2O)}2(e,e-trans-1,4-chdc)](ClO4)2 (2) (L = 1,4,8,11-tetraazacyclotetradecane, cyclam), were prepared by the reaction of [Ni(L)](ClO4)2 and a,e-cis-/e,e-trans-1,4-chdcH2 in basic solvents. Both complexes were characterized by EA, IR, and TGA techniques. In addition, molecular structures were determined by single crystal X-ray diffraction methods. In 1, the a,e-cis-1,4-chdc ligand bridges nickel(II) macrocycles to form an undulated 1D coordination polymer, whereas the complex 2 shows a dimer in which the e,e-trans-1,4-chdc ligand bridges two nickel(II) cyclams.

Vanadium Polyoxoanions within Coordination Polymers Based on a Macrocyclic Nickel Complex: Structural Diversities and Single‐Crystal to Single‐Crystal Transformation

Five three‐dimensional (3D) coordination polymers, {(NiL)[(NiL)(V16O42)]}n·2nH2O (1), [(NiL)3(VO3)6]n·5nH2O (2), [(NiL)3(V6O18)]n·7nH2O (3), [(NiL)3(V8O23)]n (4), and [(NiL)4(V10O29)]n (5), have been obtained by the reaction of the macrocyclic nickel complex [NiL](ClO4)2 (L = 1,4,8,11‐tetraazacyclotetradecane) with NH4VO3 under different conditions. Single‐crystal X‐ray diffraction analyses revealed that the [VO3]– anion assumes diverse species and structures in these five coordination polymers, including the [V16O42]n4n– sheet, [V6O18]6– ring, [VO3]nn– chain, [VO3]nn– sheet, and [V10O29]n8n– chain. The [V16O42]n4n– sheets, [V6O18]6– rings, [VO3]nn– chains, [VO3]nn– sheets, and [V10O29]n8n– chains are linked together through [NiL]2+ bridges to form the 3D frameworks of 1–5. The single‐crystal to single‐crystal transformation between 2 and desolvated 2 was successfully realized. Electrochemical measurements indicate that 2 and 4 are potential catalysts for water splitting.

Electron Transfer Reactivity of the Aqueous Iron(IV)-Oxo Complex. Outer-Sphere vs Proton-Coupled Electron Transfer.

The kinetics of oxidation of organic and inorganic reductants by aqueous iron(IV) ions, Fe(IV)(H2O)5O(2+) (hereafter Fe(IV)aqO(2+)), are reported. The substrates examined include several water-soluble ferrocenes, hexachloroiridate(III), polypyridyl complexes M(NN)3(2+) (M = Os, Fe and Ru; NN = phenanthroline, bipyridine and derivatives), HABTS(-)/ABTS(2-), phenothiazines, Co(II)(dmgBF2)2, macrocyclic nickel(II) complexes, and aqueous cerium(III). Most of the reductants were oxidized cleanly to the corresponding one-electron oxidation products, with the exception of phenothiazines which produced the corresponding oxides in a single-step reaction, and polypyridyl complexes of Fe(II) and Ru(II) that generated ligand-modified products. Fe(IV)aqO(2+) oxidizes even Ce(III) (E(0) in 1 M HClO4 = 1.7 V) with a rate constant greater than 10(4) M(-1) s(-1). In 0.10 M aqueous HClO4 at 25 °C, the reactions of Os(phen)3(2+) (k = 2.5 × 10(5) M(-1) s(-1)), IrCl6(3-) (1.6 × 10(6)), ABTS(2-) (4.7 × 10(7)), and Fe(cp)(C5H4CH2OH) (6.4 × 10(7)) appear to take place by outer sphere electron transfer (OSET). The rate constants for the oxidation of Os(phen)3(2+) and of ferrocenes remained unchanged in the acidity range 0.05 < [H(+)] < 0.10 M, ruling out prior protonation of Fe(IV)aqO(2+) and further supporting the OSET assignment. A fit to Marcus cross-relation yielded a composite parameter (log k22 + E(0)Fe/0.059) = 17.2 ± 0.8, where k22 and E(0)Fe are the self-exchange rate constant and reduction potential, respectively, for the Fe(IV)aqO(2+)/Fe(III)aqO(+) couple. Comparison with literature work suggests k22 < 10(-5) M(-1) s(-1) and thus E(0)(Fe(IV)aqO(2+)/Fe(III)aqO(+)) > 1.3 V. For proton-coupled electron transfer, the reduction potential is estimated at E(0) (Fe(IV)aqO(2+), H(+)/Fe(III)aqOH(2+)) ≥ 1.95 V.

Determination of Butylated Hydroxyanisole by Briggs‐Rauscher Oscillating Reaction Catalyzed by a Macrocyclic Nickel (II) Complex

AbstractA novel analytical approach for quantitative measurement of butylated hydroxyanisole (BHA) is dis‐ cussed in this paper. Such a method depends on the inhibitory effect of BHA on a Briggs‐Rauscher (B‐R) oscillating reaction. Unlike the classical B‐R system which involves Mn2+ as the catalyst, such a B‐R sys‐ tem is catalyzed by a macrocyclic nickel (II) complex [NiL](ClO4)2, where L in the complex is an unsatu‐ rated ligand 5,7,7,12,14,14‐hexemethyl‐1,4,8,11‐tetraazacyclotetradeca‐4,11‐diene. By perturbation of BHA on the system, the oscillation was inhibited in the presence trace amounts of BHA and the inhibition time was found to be proportional to the concentration of BHA over the range 1.00×10−7–1.20×10−4 mol/L. Two calibration curves were obtained: the first linear regression is over the range of 1.00×10−7–2.00×10−6 mol/L, and the second linear regression is over the range between 2.00×10−6 and 1.20×10−4 mol/L, with a lowest limit of detection of 4.00×10−8 mol/L. UV spectra measurements were employed to clarify the possible perturbation mechanism caused by BHA on the B‐R oscillating reaction.

An Application of Chemical Oscillation: Distinguishing Two Isomers between Cyclohexane-1,3-dione and 1,4-cyclohexanedione

In the analytical field, previous applications of chemical oscillation focused on quantitative analysis. We report in this paper a novel qualitative method electrochemically distinguishing two positional isomers by utilizing their perturbation effects on a catalyzed Briggs–Rauscher (BR) oscillation. The catalyst in the system is a macrocyclic nickel (II) complex NiL(ClO4)2, where the ligand L in the complex is 5,7,7,12,14,14-hexemethyl-1,4,8,11-tetraazacyclotetradeca-4,11-diene. The experimental results indicated that addition of cyclohexane-1,3-dione (1,3-CHD) or 1,4-cyclohexanedione (1,4-CHD) could affect the profiles of potentiometric oscillations, but their changes in the profiles are greatly different. When 1,3-CHD was injected into the oscillating system, there was an initial spiking of the oscillations, accompanying by quenching of oscillations before the regeneration of oscillations. While 1,4-CHD was injected into the dynamic mixture, the oscillatory system responded to the perturbation with only slight decrease followed by a sharp increase in the potential, before it resumed to its normal oscillation state. The perturbation of 1,3-CHD involves inhibition time, whereas the perturbation of 1,4-CHD does not. Hence these two positional isomers could be distinguished by using their different perturbation effects on a BR dynamic system in the range of 9.0×10−4 to 8.0×10−3M. Our assumption is that, perturbation of 1,3-CHD on the oscillating system involves a radical oxidization process to produce carboxylic acid, whereas perturbation of 1,4-CHD assumes idiodation and elimination steps to form 1,4-benzoquinone. Such different perturbation mechanisms are responsible for the difference in potentiometric oscillation profiles change. This hypothesis was confirmed by products analysis by FTIR and UV spectra.

High-efficiency counter electrodes using graphene hybrid with a macrocyclic nickel complex for dye-sensitized solar cells

Nanocomposites using graphene hybrid with a fully conjugated macrocyclic nickel complex were successfully prepared via a simple redox reaction of graphene oxide and an octaaza-bis-α-diimine macrocyclic nickel complex. The dye-sensitized solar cells fabricated with the graphene/macrocyclic nickel complex-based nanocomposite counter electrode reached a power conversion efficiency of 8.30%, which was higher than that of the platinum counter electrode under the same conditions. The nanocomposites exhibited excellent electrocatalytic performance for the reduction of triiodide due to the well-distributed catalytic nickel center on the graphene surface.

Nanoparticulate Ni(OH)2 Films Synthesized from Macrocyclic Nickel(II) Cyclam for Hydrogen Production in Microbial Electrolysis Cells

Hydrogen production in microbial electrolysis cells (MECs) is a promising approach for energy harvesting from wastewater. The kinetic barriers toward proton reduction necessitate the use of catalysts to drive hydrogen formation at appreciable rates and low applied potentials. Towards this end, cost effective alternatives to platinum catalysts are of paramount interest. In this study, Ni(OH)2 films were synthesized by electrophoretic deposition from a Ni(II)cyclam precursor solution at varying concentrations (6 mM, 15 mM, and 23 mM). The films were characterized by scanning electron microscopy and X-ray photo-electron spectroscopy to confirm the deposition of Ni(OH)2. The Ni(OH)2-modified electrodes were then examined by both traditional electrochemical measurements and in an MEC for hydrogen production. Tafel analysis indicates an exchange current density of ∼0.36 mA cm−2 with a Tafel slope of ∼120 mV decade−1 consistent with a rate determining proton adsoprtion step. The hydrogen production rates increased with increasing Ni(II)cyclam concentration in the precursor solution, with the 23 mM-derived film exhibiting a rate comparable to that of a Pt-based catalyst in MEC tests.

Macrocyclic dinuclear nickel(II) and manganese(II) complexes: synthesis, X-ray crystal structures, DNA cleavage, and antimicrobial activity studies

Three dinuclear macrocyclic complexes, [Ni2L1(μ-OAc)(H2O)(CH3O)](ClO4)2·4(H2O) (1), [Mn2L2(μ-OAc) (H2O)]ClO4·H2O (2) and [Mn2L3(μ-OAc)]ClO4·H2O (3), (where H2L1, H2L2 and H2L3 are the [2 + 2] condensation products of 2,6-diformyl-4-fluorophenol with diethylenetriamine and N,N-bis(3-aminopropyl)-2-thiopheno-ethylamine, respectively), have been synthesized and characterized. The electrochemical characteristics showed that the metal centers are more electropositive when strongly electron-withdrawing groups are attached to the macrocyclic ring, and hence more easily reduced. All three complexes have been found to promote cleavage of plasmid pBR322 DNA from the supercoiled form I to the open circular form II. The antibacterial activities of the complexes were also studied.

A Three-Dimensional Dynamic Metal-Organic Framework with Fourfold Interpenetrating Diamondoid Networks and Selective Adsorption Properties.

A three-dimensional metal-organic framework (1) with fourfold interpenetrating diamondoid networks was constructed using a macrocyclic nickel(II) complex and a tetracarboxylic ligand 4,4',4″,4‴-(cyclohexane-1,2-diyibis(azanetriyl))tetrakis(methylene)tetrabenzoic acid as building blocks. Despite the fourfold interpenetration, 1 possesses one-dimensional channels that are occupied by water and CH3CN guest molecules. Once the guest molecules were removed, the framework and pores in desolvated 1 are dynamic with large adsorption hysteresis loops, which exhibit selective gas adsorption for CO2 at 195 K over N2 and H2 at 77 K and selective adsorption for methanol, ethanol, and n-propanol over isopropanol at 298 K.