The synthesis and characterization of a new (E,E)-dioxime containing 20-membered tetraazadioxa macrocyclic moieties and its mononuclear complexes

A new (E,E)-dioxime, (2Z,3Z)-9,20-bis[(4-methylphenyl)sulfonyl]-1,4,7,8,9,10,11,12,14,15,17, 18,19,20,21,22-hexadecahydro-13,16-ethano[1,4,7,11,14,18]dioxatetraazacycloicosino[2,3-g] quinoxaline-2,3-dione dioxime (6) (H₂L) has been synthesized by reacting cyanogen-di-N-oxide (5) with 4,15-bis[(4-methylphenyl)sulfonyl]-2,3,4,5,6,7,9,10,12,13,14,15,16,17-tetradecahydro-8,11-ethano-1,18,4,8,11,15-benzodioxatetraazacycloicosine-20,21-diamine (4). Mononuclear complexes (7) and (8) of this ligand have been synthesized by reacting the vic-dioxime (H₂L) with NiCl₂.6H₂O and CoCl₂.6H₂O respectively. The BF₂⁺ capped Ni(II) and Co(III) complexes (9) and (10) of the dioxime have been synthesized from (7) and (8), respectively. The new compounds were characterized by a combination of elemental analysis, ¹H- and ¹³C-NMR, IR. and MS. spectral data.     

Novel Polymeric Membrane Sensors Based on Mn(III) Porphyrin and Co(II) Phthalocyanine Ionophores for Batch and Flow Injection Determination of Azide

Two novel potentiometric azide membrane sensors based on the use of manganese(III)porphyrin [Mn(III)P] and cobalt(II)phthalocyanine [Co(II)Pc] ionophores dispersed in plasticized poly(vinyl chloride) PVC matrix membranes are described. Under batch mode of operation, [Mn(III)P] and [Co(II)Pc] based membrane sensors display near‐ and sub‐Nernstian responses of ?56.3 and ?48.5 mV decade^?1 over the concentration ranges 1.0×10^?2?2.2×10^?5 and 1.0×10^?2?5.1×10^?5 mol L^?1 azide and detection limits of 1.5×10^?5 and 2.5×10^?5 mol L^?1, respectively. Incorporation of both membrane sensors in flow‐through tubular cell offers sensitive detectors for flow injection (FIA) determination of azide. The intrinsic characteristics of the [Mn(III)P] and [Co(II)Pc] based detectors in a low dispersion manifold show calibration slopes of ?51.2 and ?33.5 mV decade^?1 for the concentration ranges of 1.0×10^?5?1.0×10^?2 and 1.0×10^?4?1.0×10^?2 mol L^?1 azide and the detection limits are1.0×10^?5 and 3.1×10^?5 mol L^?1, respectively. The detectors are used for determining azide at an input rate of 40–60 samples per hour. The responses of the sensors are stable within ±0.9 mV for at least 8 weeks and are pH independent in the range of 3.9?6.5. No interferences are caused by most common anions normally associated with azide ion.     

Catalytic Properties of Single-Phase Intermetallic Compounds

Unsupported and silica-supported intermetallic compounds were prepared. Some characterizations revealed that they were composed of single-phase compounds having their specific surface. The catalytic activity of TiPt₃ was higher than that of Pt for the H₂–D₂ equilibration and hydrogenation of ethylene. Ni₃Sn gave higher selectivity than Ni for the partial hydrogenation of acetylene and the dehydrogenation of cyclohexane into benzene. RuTi/SiO₂ and Pd₃Bi/SiO₂ gave much higher selectivity than their component pure metals in FT synthesis and the oxidative acetoxylation of toluene, respectively.     

Disposable electrochemical flow cells for catalytic adsorptive stripping voltammetry (CAdSV) at a bismuth film electrode (BiFE)

Catalytic adsorptive stripping voltammetry (CAdSV) has been demonstrated at a bismuth film electrode (BiFE) in an injection-moulded electrochemical micro-flow cell. The polystyrene three-electrode flow cell was fabricated with electrodes moulded from a conducting grade of polystyrene containing 40% carbon fibre, one of which was precoated with Ag to enable its use as an on-chip Ag/AgCl reference electrode. CAdSV of Co(II) and Ni(II) in the presence of dimethylglyoxime (DMG) with nitrite employed as the catalyst was performed in order to assess the performance of the flow cell with an in-line plated BiFE. The injection-moulded electrodes were found to be suitable substrates for the formation of BiFEs. Key parameters such as the plating solution matrix, plating flow rate, analysis flow rate, solution composition and square-wave parameters have been characterised and optimal conditions selected for successful and rapid analysis of Co(II) and Ni(II) at the ppb level. The analytical response was linear over the range 1 to 20 ppb and deoxygenation of the sample solution was not required. The successful coupling of a microfluidic flow cell with a BiFE, thereby forming a “mercury-free” AdSV flow analysis sensor, shows promise for industrial and in-the-field applications where inexpensive, compact, and robust instrumentation capable of low-volume analysis is required.     

Temperature-modulated nanostructures of ytterbium-doped Cobalt Selenide (Yb-CoSe) for photovoltaic applications

This research investigated the influence of temperature variation on the properties of ytterbium-doped cobalt Selenide (Yb-CoSe) nanostructures synthesized via the electrodeposition technique. The structural, optical, morphological, and elemental features of the synthesized films were investigated through X-ray diffractometry (XRD), ultraviolet–visible (UV–vis) spectroscopy, scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDX) respectively. XRD results showed prominent peaks with a cubic phase. Good absorbance values in the visible region and reduced band gap energies upon the introduction of ytterbium were obtained from the optical analysis. Morphological results gave nanoclusters of varying sizes spread throughout the substrate surface. The elemental constituents of the deposited films were evident from the EDX spectra. The synthesized films have significant potential to be used in solar cells and optical devices.     

Colorimetric and fluorescence dual-mode detection of arsenic（v） based on cobalt oxyhydroxide nanoplatesEI北大核心CSCD

The oxidase-like activity of cobalt oxyhydroxide （CoOOH） nanosheets is inhibited by arsenic （V） in the system, thereby attenuating the oxidation of p-phenylenediamine （PPD） by CoOOH nanosheets, and changing the absorbance of the solution. Based on this principle, and the fluorescence inner filter effect （IFE） of p-phenylenediamine oxide （oxPPD） on the dye acridine orange （AO）, a colorimetric and fluorescence dualmode method for the quantitative detection of As（V） was established. The variation of absorbance and fluorescence intensity of As（V） with different concentrations was investigated, and the effects of the concentrations of CoOOH nanosheet and PPD, pH of buffer solution, and temperature of reaction were optimized. The results showed that under the optimized conditions, the concentration of As（Ⅴ） had a good linear relationship with the corresponding signal intensity, and the detection limits of colorimetric and fluorescence method were 5 and 10 nmol/L, respectively. The method has been used for the determination of arsenic（V） in lake water located the city center. © 2023, Youke Publishing Co.,Ltd. All rights reserved.     

Cobalt-Catalyzed Enantioselective Hydrogenation of Trisubstituted Carbocyclic Olefins: An Access to Chiral Cyclic Amides

The enantioselective hydrogenation of cyclic enamides has been achieved using an earth-abundant cobalt-bisphosphine catalyst. Using CoCl₂/(S,S)-Ph-BPE, several trisubstituted carbocyclic enamides were reduced with high activity and excellent enantioselectivity (up to 99 %) to the corresponding saturated amides. The methodology can be extended to the synthesis of chiral amines by base hydrolysis of the hydrogenation products. Preliminary mechanistic investigations reveal the presence of a high spin cobalt (II) species in the catalytic cycle. We propose that the hydrogenation of the carbon-carbon double bond proceeds via a sigma-bond-metathesis pathway.     

CoN1O2 Single-Atom Catalyst for Efficient Peroxymonosulfate Activation and Selective Cobalt(IV)=O Generation

High-valent metal-oxo (HVMO) species are powerful non-radical reactive species that enhance advanced oxidation processes (AOPs) due to their long half-lives and high selectivity towards recalcitrant water pollutants with electron-donating groups. However, high-valent cobalt-oxo (Co^IV=O) generation is challenging in peroxymonosulfate (PMS)-based AOPs because the high 3d-orbital occupancy of cobalt would disfavor its binding with a terminal oxygen ligand. Herein, we propose a strategy to construct isolated Co sites with unique N₁O₂ coordination on the Mn₃O₄ surface. The asymmetric N₁O₂ configuration is able to accept electrons from the Co 3d-orbital, resulting in significant electronic delocalization at Co sites for promoted PMS adsorption, dissociation and subsequent generation of Co^IV=O species. CoN₁O₂/Mn₃O₄ exhibits high intrinsic activity in PMS activation and sulfamethoxazole (SMX) degradation, highly outperforming its counterpart with a CoO₃ configuration, carbon-based single-atom catalysts with CoN₄ configuration, and commercial cobalt oxides. Co^IV=O species effectively oxidize the target contaminants via oxygen atom transfer to produce low-toxicity intermediates. These findings could advance the mechanistic understanding of PMS activation at the molecular level and guide the rational design of efficient environmental catalysts.     

Adapting Synthetic Models of Heme/Cu Sites to Energy-Efficient Electrocatalytic Oxygen Reduction Reaction

In nature, cytochrome c oxidases catalyze the 4e⁻ oxygen reduction reaction (ORR) at the heme/Cu site, in which Cu^I is used to assist O₂ activation. Because of the thermodynamic barrier to generate Cu^I, synthetic Fe-porphyrin/Cu complexes usually show moderate electrocatalytic ORR activity. We herein report on a Co-corrole/Co complex 1-Co for energy-efficient electrocatalytic ORR. By hanging a Co^II ion over Co corrole, 1-Co realizes electrocatalytic 4e⁻ ORR with a half-wave potential of 0.89 V versus RHE, which is outstanding among corrole-based electrocatalysts. Notably, 1-Co outperforms Co corrole hanged with Cu^II or Zn^II. We revealed that the hanging Co^II ion can provide an electron to improve O₂ binding thermodynamically and dynamically, a function represented by the biological Cu^I ion of the heme/Cu site. This work is significant to present a remarkable ORR electrocatalyst and to show the vital role of a second-sphere redox-active metal ion in promoting O₂ binding and activation.     

Oxo-bridged Tri- and Tetra-nuclear Cobalt Complexes Supported with Amide-Based Nitrogen Donor Ligands

This work presents two mixed-valent μ₃-oxo-bridged trinuclear [(Co²⁺)₂Co³⁺] complexes 1 and 2 and a μ₄-oxo-bridged tetranuclear [Co²⁺₄] complex 3 . Crystal structures of 1 and 2 showed the presence of triangular complexes having two Co²⁺ and one Co³⁺ centers bridged by a μ³-oxo group. In contrast, complex 3 exhibited a tetrahedrally arranged μ₄-oxo-bridged [Co²⁺₄] core. A significant feature is the stabilization of unusual μ-oxo-bridged complexes exclusively supported with all nitrogen donor ligands. The X-ray photoelectron spectroscopy confirmed the multiple oxidation states of cobalt ions in these complexes. Such oxo-bridged cobalt complexes were investigated for their catalytic activity towards H₂O₂-mediated oxidation of assorted benzyl alcohols.