Monomeric and polymeric dinuclear complexes of Co(II) or Ni(II) with calix[4]arene-tetraphosphineoxide

Monomeric and polymeric 1:2 complexes of a novel calix[4]arene-tetraphosphineoxide with Co(II) or Ni(II) nitrates were synthesized and analyzed by the X-ray method. In the monomeric complexes each metal cation is coordinated by two bidentate NO₃-ligands as well as by two proximal P=O groups at the calixarene skeleton. In the nickel metallopolymer one sort of the cations is bound by the two proximal P=O-groups but other cations link neighboring calixarene molecules through Р=О···Ni···O=P chains. The complexes possess molecular cavities or channels filled by solvent molecules. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Fabrication of a Hierarchical Ni(OH)2@Ni3S2/Ni Foam Electrode from a Prussian Blue Analogue-Based Composite with Enhanced Electrochemical Capacitive and Electrocatalytic Properties

Developing high-efficiency, cost-effective, and durable electrodes is significant for electrochemical capacitors and electrocatalysis. Herein, a 3D bifunctional electrode consisting of nickel hydroxide nanosheets@nickel sulfide nanocubes arrays on Ni foam (Ni(OH)₂@Ni₃S₂/NF) obtained from a Prussian blue analogue-based precursor is reported. The 3D higher-order porous structure and synergistic effect of different compositions endow the electrode with large specific surface area, facile ion/electron transport path, and improved conductivity. As a result, the Ni(OH)₂@Ni₃S₂/NF electrode exhibits a high specific capacity of 211 mA h g⁻¹ at a current density of 1 A g⁻¹ and 73 % capacity retention after 5000 cycles at 5 A g⁻¹. Moreover, the Ni(OH)₂@Ni₃S₂/NF electrode has superior electrocatalytic activity for the hydrogen evolution reaction with low overpotentials of 140 and 210 mV at current densities of 10 and 100 mA cm⁻², respectively. The synthetic strategy for the unique higher-order porous structure can be extended to fabricate other composite materials for energy storage and conversion.     

Metal complexes of a phenol-tailed porphyrin with different hydrogen bonds

Hydrogen bonds are very common and important interactions in biological systems, they are used to control the microenvironment around metal centers. It is a challenge to develop appropriate models for studying hydrogen bonds. We have synthesized two metal complexes of the phenol-tailed porphyrin, [Zn(HL)] and [Fe(HL)(C₆H₄(OH)(O))]. X-ray crystallography reveals that the porphyrin functions as a dianion HL^2? and the phenol OH is involved in hydrogen bonds in both structures. In [Zn(HL)], an intramolecular hydrogen bond is formed between the carbonyl oxygen and OH. In [Fe(HL)(C₆H₄(OH)(O))], the unligated O(5) of the ligand is involved in two hydrogen bonds, as a hydrogen bond donor and a hydrogen bond acceptor. The overall electronic effect on the ligand could be very small, with negligible impact on the structure and the spin state of iron(III). The structural differences caused by the hydrogen bonds are also discussed.     

Nano-electrochemical detection of hydrogen or protons using palladium nanoparticles: distinguishing surface and bulk hydrogen.

The benefits of using nanoparticle-modified electrodes are exemplified through the electrochemical detection of protons and/or hydrogen. It is shown that a palladium-nanoparticle-modified boron-doped diamond allows voltammetric information relating to the relative roles played by the surface and the bulk metal to be obtained for the proton-hydrogen system at palladium surfaces which is not accessible using palladium macroelectrodes or microelectrodes.     

Electrochemical and catalytic properties of nickel(II) complexes with bis(imino)acenaphthene and diazadiphosphacyclooctane ligands

1. Download : Download high-res image (92KB)
2. Download : Download full-size image

     

Synthesis and properties of one-dimensional Ni(Ⅱ) and Ni(Ⅱ)Cu(Ⅱ) complexes linked by hydrogen bond

Four dithiooxalato (Dto) bridged one-dimensional Ni(ll) and Ni(ll)Cu(ll) complexes (Me6[14]dieneN4)Ni2(Dto)2) (1), (Me6[14]dieneN4)CuNi(Dto)2 (2), (Me6[14]aneN4)Ni2(Dto)2 (3), and (Me6[14]aneN4)CuNi(Dto)2(4), were synthesized. These complexes have been characterized by elemental analysis, IR, UV and ESR spectra. The crystal structure of complex 3 was determined. It crystallizes in the monoclinic system, space group C2/c with a = 2.2425(4) nm, b = 1.0088(2) nm, c=1.4665(3) nm, β= 125.32(3)° ;Z=4; R = 0.076, Rw = 0.079. In the complex, Ni(1) coordinates four sulphur atoms of two Dto ligands in plane square environment. Ni(2) lies in the center of mac-rocyclic ligand. For Dto ligand, two sulphur atoms coordinate Ni(1), and O(1) coordinates Ni(2) and forms weak coordination bond. O(2) is linked to N(2) of macrocyclic ligand through hydrogen bond.     

Fabrication of an electrode-viologen-hydrogenase heterogeneous system and the electrochemical hydrogen evolution

An indium tinoxide (ITO) electrode was chemically modified by one layer of viologen (VIO) deri vative, which possessed a persistent and reproducible electrochemical response. A monolayer of a thermal stable hydrogenase from Thiocapsa roseopersic ina was stabilized on a synthesized poly-l-lysine subphase surface and transferred on to the electrode for fabrication of an ITO-VIO-hydrogenase heterogeneous system. Electrochemical properties of both the ITO-VIO monolayer and the heterogeneous ITO-VIO-hydrogenase system have been investigated. Hydrogen evolution could be measured by potentiostating the VIO-hydrogenase-covered ITO electrode to “electroplate” [(VIO⁺)_n]_surf and a large increase in hydrogen evolution was observed when using an electrolytesolution containing sodium dithionite. We discuss the possible electron transfer process.     

Anodically electrodeposited Co+Ni mixed oxide electrode: preparation and electrocatalytic activity for oxygen evolution in alkaline media

Co+Ni mixed oxides on Ni substrate were prepared through anodic electrodeposition from Co(NO₃)₂ and Ni(NO₃)₂ aqueous solutions with five different Co²⁺/Ni²⁺ ratios beside only Co²⁺. By the electrochemical measurements, the optimum performance in electrocatalytic activity for oxygen evolution reaction in alkaline media was obtained on the Co+Ni mixed oxide deposited from the solution containing Co²⁺/Ni²⁺ ratio of 1:1. The mixed oxide is corresponding to about 68 at% Co contents with spinel-type NiCo₂O₄ phase and porosity surface structure. The electrochemical kinetic parameters including exchange current density, Tafel slopes, reaction order with respect to [OH⁻] and standard electrochemical enthalpy of activation were analyzed also. A possible mechanism involving the formation of a physisorbed hydrogen peroxide intermediate in a slow electrochemical step was presented, which accounts for the values of the experimental results.     

Electrocatalytic Hydrogen Production by a Nickel(II) Complex with a Phosphinopyridyl Ligand

A novel nickel(II) complex [Ni(L)₂Cl]Cl with a bidentate phosphinopyridyl ligand 6‐((diphenylphosphino)methyl)pyridin‐2‐amine (L) was synthesized as a metal‐complex catalyst for hydrogen production from protons. The ligand can stabilize a low Ni oxidation state and has an amine base as a proton transfer site. The X‐ray structure analysis revealed a distorted square‐pyramidal Ni^II complex with two bidentate L ligands in a trans arrangement in the equatorial plane and a chloride anion at the apex. Electrochemical measurements with the Ni^II complex in MeCN indicate a higher rate of hydrogen production under weak acid conditions using acetic acid as the proton source. The catalytic current increases with the stepwise addition of protons, and the turnover frequency is 8400 s^?1 in 0.1 m [NBu₄][ClO₄]/MeCN in the presence of acetic acid (290 equiv) at an overpotential of circa 590 mV.     

Polypyrrole Shell@3D‐Ni Metal Core Structured Electrodes for High‐Performance Supercapacitors

Three‐dimensional (3D) nanometal films serving as current collectors have attracted much interest recently owing to their promising application in high‐performance supercapacitors. In the process of the electrochemical reaction, the 3D structure can provide a short diffusion path for fast ion transport, and the highly conductive nanometal may serve as a backbone for facile electron transfer. In this work, a novel polypyrrole (PPy) shell@3D‐Ni‐core composite is developed to enhance the electrochemical performance of conventional PPy. With the introduction of a Ni metal core, the as‐prepared material exhibits a high specific capacitance (726 F g^?1 at a charge/discharge rate of 1 A g^?1), good rate capability (a decay of 33 % in C_sp with charge/discharge rates increasing from 1 to 20 A g^?1), and high cycle stability (only a small decrease of 4.2 % in C_sp after 1000 cycles at a scan rate of 100 mV s^?1). Furthermore, an aqueous symmetric supercapacitor device is fabricated by using the as‐prepared composite as electrodes; the device demonstrates a high energy density (≈21.2 Wh kg^?1) and superior long‐term cycle ability (only 4.4 % and 18.6 % loss in C_sp after 2000 and 5000 cycles, respectively).     

Transition Metal (Mn,Fe, Co,Ni)‐Doped Graphene Hybrids for Electrocatalysis

The development of electrocatalysts is crucial for renewable energy applications. Metal‐doped graphene hybrid materials have been explored for this purpose, however, with much focus on noble metals, which are limited by their low availability and high costs. Transition metals may serve as promising alternatives. Here, transition metal‐doped graphene hybrids were synthesized by a simple and scalable method. Metal‐doped graphite oxide precursors were thermally exfoliated in either hydrogen or nitrogen atmosphere; by changing exfoliation atmospheres from inert to reductive, we produced materials with different degrees of oxidation. Effects of the presence of metal nanoparticles and exfoliation atmosphere on the morphology and electrocatalytic activity of the hybrid materials were investigated using electron microscopy, energy‐dispersive X‐ray spectroscopy, X‐ray photoelectron spectroscopy, and cyclic voltammetry. Doping of graphene with transition metal nanoparticles of the 4th period significantly influenced the electrocatalysis of compounds important in energy production and storage applications, with hybrid materials exfoliated in nitrogen atmosphere displaying superior performance over those exfoliated in hydrogen atmosphere. Moreover, nickel‐doped graphene hybrids displayed outstanding electrocatalytic activities towards reduction of O₂ when compared to bare graphenes. These findings may be exploited in the research field of renewable energy.     

Ferrocene incorporating host-guest dyads with electrochemically controlled three-pole hydrogen bonding properties

We describe the electrochemically controlled hydrogen bonding interactions between the isobutyl flavin/2,6-diferrocenylamidopyridine (2·5) and 9,10-phenanthrenequinone/1-ferrocenyl-3-hexylurea (4·6) dyads. Cyclic and square wave voltammetry studies have shown that the binding efficiencies between these moieties can be electrochemically actuated in non-polar (CH₂Cl₂ for 2·5) or polar (DMF for 4·6) organic solvents between three distinct states.