Polymeric Nickel Research Articles

Thermal behavior of polymeric nickel(II) oxalate complex obtained through nickel(II) nitrate/ethylene glycol reaction

This paper analyzes the thermal decomposition of polymeric nickel(II) oxalate complex, a homopolynuclear coordination compound having the formula [Ni(C2O4)(H2O)2]n?xnH2O. The thermolysis was conducted in both dynamic oxidative and inert atmospheres by simultaneously applying thermogravimetry (TG), differential thermogravimetry (DTG) and differential thermal analysis (DTA). The proposed decomposition mechanism was confirmed using evolved gas analysis (EGA) technique via the Fourier transform infrared spectroscopy (FTIR) of the gaseous decomposition products. The solid-state decomposition products formed during heating were investigated by chemical analysis, FTIR, Raman spectroscopy and X-ray diffraction (XRD). The structure, morphology and properties of the final decomposition products were characterized by XRD, FTIR, energy dispersive X-ray spectroscopy (EDX) and transmission electron microscopy (TEM). These analyses show that the final decomposition product in oxidative atmosphere was nickel oxide, shaped as polygonal particles with widely distributed sizes. As for the results in inert atmosphere, they outlined a mixture of Ni and NiO as rhombohedral particles in a 3:2 molar ratio.

Solvent Effects on the Electronic and Ionic Conductivity in Polymeric Nickel(II) Complex of N,N'-Bis(3-Methoxysalicylidene)ethylenediamine

Solvent Effects on the Electronic and Ionic Conductivity in Polymeric Nickel(II) Complex of N,N'-Bis(3-Methoxysalicylidene)ethylenediamine

SOLVENT EFFECTS ON THE ELECTRONIC AND IONIC CONDUCTIVITY IN POLYMERIC NICKEL(II) COMPLEX OF N,N′ BIS(3 METHOXYSALICYLIDENE)ETHYLENEDIAMINE

The electrochemical oxidation-reduction of polymeric nickel(II) complex of N,N′-bis(3-methoxysalicylidene)ethylenediamine was investigated in acetonitrile and 1,2-dichloroethane-based solutions by a combination of in situ conductance measurements, quartz crystal microbalance, and cyclic voltammetry. The type of electrolyte solution is shown to have a pronounced effect on the variations in the electrical conductance and ion and solvent transfer at the polymer/solution interface when the polymer is electrochemically switched between various oxidation states.

Overcoming the Low Reactivity of Aryl Chlorides: Amination via Reusable Polymeric Nickel–Iridium Dual Catalysis under Microwave and Visible Light

Overcoming the Low Reactivity of Aryl Chlorides: Amination via Reusable Polymeric Nickel–Iridium Dual Catalysis under Microwave and Visible Light

Uncovering the mechanism of water-promoted electrochemical degradation of NiSalen polymers

Polymeric nickel complexes with salen-type ligands (NiSalen) can serve as useful materials for a range of applications, including sensors, catalytic systems and energy storage devices. Although they surpass convenient conductive polymers in some aspects, they are still in the shadow of them. What pushes researchers away from NiSalen polymers is the low reproducibility of their electrochemical response, which sometimes can vary from day to day. Despite the convenient conductive polymers, which electrochemistry is often tolerant to moisture, most of the NiSalen polymers are highly water sensitive, which causes the uncertainty of their behavior, including the degradation of electrochemical activity and electrical conductance. In the present study, we demonstrate how NiSalen polymers degrade in the presence of H2O, and how the 3-substituent alternates the ultimate site of the H2O attack on the polymer. By a combination of the computational, electrochemical and spectroelectrochemical techniques, we demonstrate that the water-promoted degradation of the NiSalen polymer occurs only while it is oxidized. We have found that H2O attacks the Ni atom of the polymer, switching off charge transport along the polymer chain, but an introduction of CH3O-groups in the ligand structure changes the binding mode of H2O, protecting the polymer from degradation.

Reversible Redox Processes in Polymer of Unmetalated Salen-Type Ligand: Combined Electrochemical in Situ Studies and Direct Comparison with Corresponding Nickel Metallopolymer.

Most non-metalized Salen-type ligands form passivation thin films on electrode surfaces upon electrochemical oxidation. In contrast, the H2(3-MeOSalen) forms electroactive polymer films similarly to the corresponding nickel complex. There are no details of electrochemistry, doping mechanism and charge transfer pathways in the polymers of pristine Salen-type ligands. We studied a previously uncharacterized electrochemically active polymer of a Salen-type ligand H2(3-MeOSalen) by a combination of cyclic voltammetry, in situ ultraviolet–visible (UV–VIS) spectroelectrochemistry, in situ electrochemical quartz crystal microbalance and Fourier Transform infrared spectroscopy (FTIR) spectroscopy. By directly comparing it with the polymer of a Salen-type nickel complex poly-Ni(3-MeOSalen) we elucidate the effect of the central metal atom on the structure and charge transport properties of the electrochemically doped polymer films. We have shown that the mechanism of charge transfer in the polymeric ligand poly-H2(3-MeOSalen) are markedly different from the corresponding polymeric nickel complex. Due to deviation from planarity of N2O2 sphere for the ligand H2(3-MeOSalen), the main pathway of electron transfer in the polymer film poly-H2(3-MeOSalen) is between π-stacked structures (the π-electronic systems of phenyl rings are packed face-to-face) and C-C bonded phenyl rings. The main way of electron transfer in the polymer film poly-Ni(3-MeOSalen) is along the polymer chain, while redox processes are ligand-based.

The activity of monomeric and polymeric nickel complexes with Salen-type ligands as photosensitive materials for electrochemical solar cells

The influence of polymerization conditions on the photovoltaic effect in polymeric nickel complexes with salen-type ligands in an aprotic electrolyte was studied. The possibility of using both monomeric and polymeric nickel complexes with salen-type ligands as active materials for electrochemical solar cells was investigated. It was shown that the hydroxyl-substituted monomeric complex could potentially be used as anode sensitizer in the Gratzel cell, while the polymeric complex could be used as active cathode material for photoelectrochemical cells with an aprotic electrolyte.

Electrocatalytic Oxidation of Methanol by a Polymeric Ni Complex-Modified Electrode Prepared by a One-Step Cold-Plasma Process.

In this work, a polymeric nickel complex-modified indium tin oxide (ITO) electrode was prepared by a one-step cold-plasma process of acrylic-Ni complex precursors. Also, the work provides the electrocatalytic oxidation of methanol by a polymeric Ni complex-modified electrode prepared by a simple one-step cold-plasma process. The acrylic-Ni complex precursors were synthesized by complexation of nickel (II) chloride, and acrylic acid in a small amount of water; subsequently we added N,N′-methylene-bis-acrylamide as a crosslinking agent to the complex solution. We characterized the prepared polymeric Ni complex-modified (Ni-modified) catalytic electrode by X-ray photoelectron spectroscopy, field emission scanning electron microscopy, and electrochemical methods. Electrochemical characterization showed stable redox behavior of Ni(III)/Ni(II) couples. Cyclic voltammetric experiments have shown that electrocatalytic oxidation of methanol can occur on Ni-modified catalytic electrodes, while not observed on bare ITO. As a result, this work provides the simple and easy preparation of electrocatalysts by one-step plasma process for methanol fuel cell.

6,6′-{[Ethane-1,2-diylbis(azaneylylidene)]bis(methaneylylidene)}bis[2-(hexyloxy)phenolato] Nickel(II)

Polymeric nickel complexes of salen ligands meet a wide range of applications in catalysis and electrochemistry. Because these polymers usually form very rigid films, the introduction of the conformationally flexible fragments in the corresponding monomers favors the amorphization and, thus, the mass transport. Herein we report a preparation of the hexyloxy-substituted monomeric NiSalen complex by the direct alkylation of the hydroxy-substituted complex. The resulting product was characterized by the 1H and 13C nuclear magnetic resonance (NMR), ESI-high resolution mass spectrometry (ESI-HRMS, and Fourier-transform infrared spectroscopy (FTIR). The crystal structure of the product was examined by an XRD, indicating the formation of the solvate with dichloromethane. The obtained product was found to be highly soluble in non-polar solvents, in contrast to typical NiSalens.

Switching from Biaryl Formation to Amidation with Convoluted Polymeric Nickel Catalysis

A stable, reusable, and insoluble poly(4-vinylpyridine) nickel catalyst (P4VP-NiCl2) was prepared through the molecular convolution of poly(4-vinylpyridine) (P4VP) and nickel chloride. We proposed ...

Полимерные комплексы никеля с лигандами саленового типа как многофункциональные компоненты катодов литий-ионных аккумуляторов

This work describes the method of preparation of composite lithium-ion battery cathodes that allows total replacement of conventional polymer binders and electroconductive carbon black additives with redox-active conductive polymeric nickel complexes of salen-type Schiff base ligands in the electrode layer. The structure and electrochemical behavior of the electrodes prepared by this method have been investigated. Polymeric metal complexes have been shown to successfully perform the functions of binding and conductive components and also reversibly store charge in the lithium iron phosphate cathodes, which could result in the improvement of the specific capacity of the cathode layer, as compared with the conventional electrodes.

Литий-ионный суперконденсатор с положительным электродом на основе углеродного материала, модифицированного полимерным комплексом никеля с основанием Шиффа

A lithium-ion supercapacitor with a positive electrode based on a highly porous carbon material modified with an electronically conducting polymeric nickel Schiff base complex has been developed for the first time. The electrochemical capacity of the obtained device was over 40% higher than the capacitance of the cell with a non-modified positive electrode without compromising other performance parameters (working voltage, resistance, number of charge-discharge cycles).

Theoretical calculation of the exchange coupling constant in some polymeric nickel(II) complexes using range-separated functionals

The magnetic parameters (J, g) of two nickel(II) 1D polymers (Ni(en)(ox) and Ni(ox) (ampy)2; where en = ethylene diamine, ox = oxalate, ampy = 4-amino-pyridine) were calculated using 6-311+G* basis set and six range-separated DFT functionals (CAM-B3LYP, LC-BLYP, wB97, wB97X, wB97X-D3 and B2T-PLYP) together with the hybrid B3LYP method for sake of comparison. We found that the wB97, CAM-B3LYP and wB97X-D3 methods gave approximate value of J for compound 1 and the B2T-PLYP method was found to be the best method for compound 2. The g values were calculated by the coupled perturbed approach. However, we assume that a higher approximation is needed in order to give satisfactory results for g. A new equation has been proposed to relate the experimental susceptibility to the J and g parameters. The Curie-Weiss law was included in this equation resulting in a good explanation of the steep part of the experimental curve below 20 K.

Double μ2-(phenoxido)-bridged dinuclear and polynuclear nickel(II) complexes: Magnetic properties and DNA/protein interaction

One dinuclear and one 1D polymeric nickel(II) complex, namely {[Ni2(HL)2(pa)2(H2O)2]·DMF} (1) and {[Ni2(HL)2(ppda)(H2O)2]·DMF·H2O}n (2) (H2L = (E)-2-((1-hydroxybutan-2-ylimino)methyl)phenol, pa = 3-phenylacrylate, ppda = p-phenylenediacrylate) have been synthesized and characterized by X-ray single crystal structure determination. Complex 1 is double phenoxo-bridged dinuclear Ni(II) complex, whereas complex 2 is a 1D polynuclear chain where double phenoxo-bridged dinuclear units are connected through bridging ppda ligands. The variable temperature magnetic behavior of the complexes was studied using the Hamiltonian H = −JS1S2, S1 = S2 = SNi and confirms the presence of an overall antiferromagnetic interaction in both complexes. Good agreement between the experimental and simulated curves were found using the parameters: gNi = 2.15, DNi = 4.0 cm−1 and JNi–Ni = −0.60 cm−1 for 1, and gNi = 2.15, DNi = 4.8 cm−1 and JNi–Ni = −3 cm−1 for 2. The interactions of the complexes with CT-DNA were investigated using UV–Vis absorption and fluorescence spectroscopic methods and they show that both the complexes interact with CT-DNA. The intrinsic binding constants values for interaction with CT-DNA are 3.9(±0.10) × 105 and 3.43(±0.09) × 105 M−1 for 1 and 2, respectively. The interactions of the complexes with bovine serum albumins (BSA) and human serum albumins (HSA) were also studied using electronic absorption and fluorescence spectroscopic techniques and the results show that both complexes interact with the serum albumins via a ground state association process.

Radical formation in polymeric nickel complexes with N2O2 Schiff base ligands: An in situ ESR and UV–vis–NIR spectroelectrochemical study

A series of electrochemically generated polymeric nickel (II) Schiff base complexes was investigated by in situ electron spin resonance (ESR)/ultraviolet–visible–near infrared (UV–vis–NIR) spectroelectrochemistry and the combination of cyclic voltammetry and quartz crystal microbalance (QCM) techniques. The comparative analysis of the in situ ESR and UV–vis–NIR (including low-energy NIR range) spectra of poly-[Ni(Schiff)] films recorded during their oxidation at ambient temperature was performed, which allowed us to monitor the formation of different charge carriers in the polymer at different doping levels and elucidate their structure as well as the extent of their delocalization. The polymer doping level achieved by its oxidation within selected range of potentials was determined by combining the results of cyclic voltammetry and QCM measurements. The influence of the substituents in the diamine backbone and phenolate moieties of the ligand on the spectroscopic properties of the oxidized polymers and number of electrons per monomer unit exchanged in the redox processes was studied in detail. Integration of data from all techniques allowed us to propose the existence of both inter- and intrachain delocalization of radical cations generated in the doped polymers and show that the highest doping levels (up to two positive charges per a monomer unit) are attained in the poly-[Ni(Schiff)] films with highly localized biphenoxyl radical cations.

Electrochemical transformations of polymers formed from nickel (II) complexes with salen-type ligands in aqueous alkaline electrolytes

The polymeric nickel complexes with salen-type ligands can serve as useful materials for a range of applications, including catalytic systems and energy storage devices. Despite the fact that electrochemical properties of such complexes were investigated in detail in non-aqueous solutions, there has still remained scarce information about their behavior in aqueous systems. This work is devoted to studying such properties of poly[Ni(salen)] films in aqueous alkaline electrolytes. By combination of electrochemical methods with X-ray photoelectron and Raman spectroscopy it was shown that the redox transformations observed result in ligand exchange and formation of nickel hydroxide thin films deposited on the working electrodes. The obtained material consists of uniformly distributed nanoparticles with the characteristic size of about 10 nm. Catalytic activity of the produced modified electrodes in reactions of ethanol and methanol oxidation, as well as their ability to be charged and discharged reversibly for more than 1000 cycles, makes them promising materials for applications in catalytic and energy storage devices.

Effect of Structure of Polymeric Nickel Complexes with Salen-Type Ligands on the Rate of Their Electroactivity Decay in Solutions of Water-Containing Electrolytes

The influence of the structure of diimine bridge in the Schiff’s bases (derivatives of N,N'-ethylenebissalicylimine) on the rate of the loss of electroactivity of their complexes with nickel in acetonitrile containing 0.1 M of tetraethylammonium tetrafluoroborate (anhydrous and upon addition of 1 wt % of water) has been studied. It has been shown that the presence of bulky yet light methyl groups in the structure of diimine bridge significantly reduced the loss of electroactivity (37% of the initial capacity retained after 50 cycles) as compared to the ligand containing no substituents and containing phenyl group as the substituent (17 and 20%, respectively, of initial capacity retained after 50 cycles).

Effect of phosphorus content on mechanical properties of polymeric nickel composite materials with a diamond-structure microlattice.

Periodical and ordered polymer–nickel-coated composite materials with a diamond-structure microlattice and various contents of phosphorus (4.10 wt%, 8.01 wt%, 12.25 wt%, 16.08 wt%, 20.21 wt%) were fabricated via electroless nickel–phosphorus (Ni–P) coating onto diamond-structured polymeric templates using a 3D printing stereo lithography apparatus. With the increase in P content, the crystal morphology transfers from crystal to non-crystal. By controlling identical 1.0 μm-thickness of 5 different content coatings onto templates, the properties of 5 different microlattice composites were tested by uniaxial compression. To confirm the thickness and P content, several mathematical models were developed to direct the subsequent experiments and all theoretical predictions are in agreement with factual characterization. The composite with 8.01 wt% phosphorus content and density of 240.4 kg m−3 performs best, with the maximum compressive strength reaches 1.08 MPa, which is 2.1 times higher than that of polymer templates.

Polymeric nickel complexes with salen-type ligands for modification of supercapacitor electrodes: impedance studies of charge transfer and storage properties

Polymeric transition metal complexes with salen-type Schiff base ligands are considered as promising materials for modification of electrical double layer capacitor electrodes. Electrochemical properties of these polymers that define their performance in supercapacitors should be influenced by the ligand structure but this influence has never been systematically investigated. This article describes results of a comparative study of capacitance and charge transfer rate in polymeric nickel complexes with six different salen-type ligands using electrochemical impedance spectroscopy, analyzes advantages and limitations of this method vs. cyclic voltammetry, and provides some insights into the structure and morphology of nickel-salen type polymers. Analysis of results obtained by different analytical techniques shows that introduction of methoxy-substituents into the phenyl rings of the salen ligand and different substituents to the diamine bridge of the ligand causes noticeable changes in electrochemical properties of corresponding polymeric nickel complexes. Experimentally obtained values of gravimetric and volumetric capacitance, as well as effective charge diffusion coefficient provide guidelines for selection of most suitable nickel-salen type polymers for application in energy storage devices, including supercapacitors.

Heterometallic palladium-copper and palladium-nickel complexes with pivalate bridges

Reactions of (α-Pic)2Pd(OOCCMe3)2 (I) with dinuclear copper pivalate dihydrate and polymeric nickel bispivalate afforded the complexes (α-Pic)2Pd(μ-OOCCMe3)2Cu2(μ-OOCCMe3)4 (II) and Pd(μ- OOCCMe3)4Ni(α-Pic) (III), respectively, which were structurally characterized. The lantern dimers in complex II show no Cu···Cu bonds (Cu···Cu, 2.671(3) A) and are united to form chains through the axial bridging pivalate groups inherited from palladium monomer I. In contrast, complex III features heterometallic palladium- nickel lanterns in which the Ni atom has an axial α-picoline ligand, while the Pd atom has no axial ligand; instead, a short Pd–Ni bond is formed (2.4976(3) A). For triplet-state complex III and its zinc analog Pd(μ-OOCCMe3)4Zn(α-Pic) (IV), quantum chemical calculations and topological analysis of the electron density were performed.