Electrocatalytic properties of a dinuclear cobalt(III) coordination compound in molecular oxygen reduction reaction

A new dinuclear cobalt(III) coordination compound, [Co₂L(μ‐N₃)(N₃)₂]·CH₃OH ( 1 ), was synthesized and characterized by elemental analysis, spectroscopic methods, and single‐crystal X‐ray analysis in which H₃L is a heptadentate ligand obtained by the condensation of triethylenetetramine with 5‐bromo‐2‐hydroxybenzaldehyde. X‐ray analysis revealed that two cobalt(III) ions have distorted octahedral geometry and are connected together by a phenoxy and an azide bridging ligand. The catalytic activity of compound 1 for oxygen (O₂) reduction reaction was investigated. Compound 1 can efficiently catalyze the reduction of O₂ by a weak electron donor, ferrocene (Fc), at the polarized water–1,2‐dichloroethane interface. It was found that compound 1 can catalyze O₂ reduction to H₂O₂, whereas in the presence of Fc, it can catalyze the reduction of O₂ to water.     

A new polypyridyl-based Ru (II) complex as a highly efficient electrocatalyst for CO2 reduction

A new polypyridyl Ru (II) complex, cis-[Ru (Me₄phen)₂(CH₃CN)₂](NO₃)₂ (Me₄phen = 3,4,7,8-tetramethyl-1,10-phenanthroline) has been prepared and fully characterized by elemental analysis, X-ray crystallography, cyclic voltammetry and spectroscopic techniques. The solid-state structure of the complex indicated that the Ru (II) center is sitting in an N₄N′₂ coordination environment with a distorted octahedral geometry. Cyclic voltammetry technique was used to investigate the catalytic activity of the Ru (II) complex on the electrocatalytic reduction of CO₂ to CO in acetonitrile. The effect of the different reaction parameters, including the scan rate, concentration of the electrocatalyst [complex Ru (II)] and reaction temperature, on the catalytic activity was also investigated. The results showed that the electrocatalytic activity of the complex increases with increasing electrocatalyst concentration and scan rate. Further, the CO₂ reduction peak current decreases at lower temperatures owing to the inverse relationship between the temperature and activation energy. The theoretical calculations confirmed the proposed electrocatalytic mechanism comprising seven steps.     

Synthesis and characterization of Ni(II) complexes bearing of 2‐(1H–benzimidazol‐2‐yl)‐phenol derivatives as highly active catalysts for ethylene oligomerization

Novel Ni(II) complexes of 2‐(1H–benzimidazol‐2‐yl)‐phenol derivatives (HL_x: x  =  1–5; C1–C5 ) have been synthesized and characterized. In the mononuclear complexes, the ligands were coordinated as bidentate, via one imine nitrogen and the phenolate oxygen atoms. The structures of the compounds were confirmed on the basis of FT‐IR, UV–Vis, ¹H‐, ¹³C–NMR, inductively coupled plasma and elemental analyses (C, H and N). The purity of these compounds was ascertained by melting point (m.p.) and thin‐layer chromatography. The geometry optimization and vibrational frequency calculations of the compounds were performed using Gaussian 09 program with B3LYP/TZVP level of theory. All Ni(II) complexes were activated with diethylaluminum chloride (Et₂AlCl), so that C2 showed the highest activity [6600 kg mol^?1 (Ni) h^?1], where the ligand contains a chlorine substituent. Oligomers obtained from the complexes consist mainly of dimer and trimer, and also exhibit high selectivity for linear 1‐butene and 1‐hexene. Both the steric and electronic effects of coordinative ligands affect the catalytic activity and the properties of the catalytic products.     

1D Azido bridged Cu(II) coordination polymer with 1,3-oxazolidine ligand as an effective catalyst for green click synthesis of 1,2,3-triazoles

A new 1D azido bridged Cu(II) coordination polymer with 1,3-oxazolidine based ligand, [Cu(H₃L)(μ_1,3-N₃)(N₃)]_n ( 1 ), was synthesized and characterized by elemental analysis and spectroscopic methods. The structure of 1 was also determined by single crystal X-ray analysis which indicated the 1D polymeric chain is generated by end-to-end (EE) azide bridge. The obtained compound was employed as catalyst in green click synthesis of β-hydroxy-1,2,3-triazoles from one-pot three-component cycloaddition reaction of epoxide-azide-alkyne. The catalytic reactions were carried out in water as a safe, cheap and green solvent. The catalytic studies indicated that the obtained 1D azido bridged Cu(II) coordination polymer is an active catalyst for preparing β-hydroxy-1,2,3-triazoles. The effect of temperature on the selectivity of the catalytic system was studied and the results indicated this catalytic system has high selectivity at low temperatures. The structure the product obtained from the reaction of 2,3-epoxypropylphenylether, azide and 1-ethynyl-1-cyclohexanol ( T4 ) was determined by single crystal X-ray analysis. The results indicate Cu(II) coordination polymers can be a new class of catalytic systems for green click synthesis of 1,2,3-triazoles.     

Synthesis and characterization of Graphitic Carbon Nitride/Mesoporous Nano-Silica (g-C3N4/KCC-1) nanocomposite as a novel highly efficient and recyclable photocatalyst for degradation of antibiotic in aqueous solution

Research on Chemical Intermediates - Among the pharmaceutical compounds, penicillin G (PG) antibiotic has frequently introduced in waters and wastewater. The present study has investigated a novel...     

High performance fuzzy-Padé controllers: Introduction and comparison to fuzzy controllers

In this paper, a new highly convergent, efficient, and fast response control technique entitled as fuzzy-Padé control method is introduced. It provides a simple methodology to exploit the heuristic knowledge in controlling a system. Fuzzy–Padé controllers originate from a unification of heuristic knowledge expressed as the rule base, and Padé approximants. In this method, fuzzy singleton rules are used to generate the rule base. Accordingly, unknown parameters in the Padé approximant are determined using these rules. The fuzzy-Padé controllers possess certain advantages over fuzzy controllers, and they can be applied in situations where fuzzy controllers previously failed. To demonstrate the effectiveness and robustness of the method, the simulation results for three case studies, the single inverted pendulum, ball and beam, and parallel double inverted pendulum systems are presented. In the case studies, it is shown that the fuzzy-Padé controller has greater convergence region, is quite faster, and its energy consumption is much lower than the fuzzy controller.     

A mild,simple and efficient method for selectiveα-monobromination of 1,3-diketones and β-ketoesters using pyridinium bromochromate

Pyridinium bromochromate has been found to be a highly efficient and selective reagent for theα-monobromination of 1,3-diketones andβ-keto-esters in the absence of base,Lewis acid,or other catalyst.The products were formed in high to excellent yields under mild reaction conditions and in short reaction times.     

Characterization of modules of finite projective dimension via Frobenius functors

Let M be a finitely generated module over a local ring R of characteristic p > 0. If depth(R) = s, then the property that M has finite projective dimension can be characterized by the vanishing of the functor Extⁱ_R(M, ^fnR){{\rm Ext}^i_R(M, ^{f^n}R)} for s + 1 consecutive values i > 0 and for infinitely many n. In addition, if R is a d-dimensional complete intersection, then M has finite projective dimension can be characterized by the vanishing of the functor Extⁱ_R(M, ^fnR){{\rm Ext}^i_R(M, ^{f^n}R)} for some i ≥ d and some n > 0.