Silver(Ⅱ) 5,10,15,20-tetra(ethoxycarbonyl) porphyrin:An unexpected six-coordinate linear assembled structure

A novel six-coordinated silver porphyrin linear assembly was observed in silver(II) 5,10,15,20-tetra(ethoxycarbonyl) porphyrin crystal.     

Magnetization of sol-gel prepared zinc ferrite nanoparticles: Effects of inversion and particle size

Nanoparticles of ZnFe₂O₄ have been prepared by using sol-gel method in two different mediums (acidic and basic) in order to observe the influence of the medium on the magnetic properties of the obtained nanoparticles. X-ray diffraction and Mössbauer studies of these samples show the presence of single-phase spinel structure. The average size of the particles as determined by X-ray diffraction increases with the annealing temperature from 18 to 52 nm. With the increase in particle size, magnetization decreases while the magnetization blocking temperature increases. Magnetization studies show that the samples prepared in basic medium have more ferrimagnetic nature as compared to those prepared in acidic medium. We understand this increase in magnetization as reflective of the increased degree of inversion (transfer of Fe³⁺ ions from octahedral to tetrahedral sites) in the particles of smaller size unit cells. From lattice parameter calculations on different particles it is determined that inversion is more favorable in the particles prepared in a basic medium than in the acidic medium due to the smaller cell size in the former.     

Selective substitution of corroles: nitration,hydroformylation, and chlorosulfonation

This work demonstrates the feasibility and power of electrophilic substitution on the peripheral carbon atoms of triarylcorroles as a synthetic tool to new derivatives. The large difference in the reactivity of the various carbon atoms on the macrocycle was shown to be of electronic rather than steric origin. A careful choice of reagents and a delicate control of reaction conditions allowed the selective syntheses of novel derivatives, in all of which substitution took place selectively in only the directly joined pyrrole rings of the macrocycle. This was proven by a combination of X-ray crystallography of the various products and detailed analysis of their NMR spectra.     

Metallocorroles as Nonprecious‐Metal Catalysts for Oxygen Reduction

The future of affordable fuel cells strongly relies on the design of earth‐abundant (non‐platinum) catalysts for the electrochemical oxygen reduction reaction (ORR). However, the bottleneck in the overall process occurs therein. We have examined herein trivalent Mn, Fe, Co, Ni, and Cu complexes of β‐pyrrole‐brominated corrole as ORR catalysts. The adsorption of these complexes on a high‐surface‐area carbon powder (BP2000) created a unique composite material, used for electrochemical measurements in acidic aqueous solutions. These experiments disclosed a clear dependence of the catalytic activity on the metal center of the complexes, in the order of Co>Fe>Ni>Mn>Cu. The best catalytic performance was obtained for the Co^III corrole, whose onset potential was as positive as 0.81 V versus the reversible hydrogen electrode (RHE). Insight into the properties of these systems was gained by spectroscopic and computational characterization of the reduced and oxidized forms of the metallocorroles.     

Stainless steel supported NiS/CeS nanocomposite for significantly enhanced oxygen evolution reaction in alkaline media

Journal of Solid State Electrochemistry - The discovery of highly active and cost-effective materials capable of catalyzing the oxygen evolution reaction (OER) is essential for water splitting. In...     

Development of some important nitrogen donor ligands for transition metal homogeneous catalysis

This review provides a broad overview of the literature related to the importance of ligands in homogeneous catalysis. In particular, it describes the types of nitrogen donor ligands that have typically been used for homogeneous catalysis. We surveyed the important transition metal homogenous catalysts explicitly from 2011 up to early 2014 and summarize their comparative catalytic activities. Generally, the main factors observed are the ligand structure, electron donor property and steric bulk which can affect the catalytic activity. Electron count and inductive effect can also influence the efficiency of homogeneous catalyst.     

Structural,Optical and Electrical Properties of Cu0.6CoxZn0.4−xFe2O4 (x = 0.0, 0.1, 0.2, 0.3, 0.4) Soft Ferrites

A series of cobalt-inserted copper zinc ferrites, Cu_0.6Co_xZn_0.4−xFe₂O₄ (x = 0.0, 0.1, 0.2, 0.3, 0.4) having cubic spinel structure were prepared by the coprecipitation method. Various characterization techniques, including XRD, FTIR, UV-vis and I–V were used to investigate structural optical and electrical properties, respectively. The lattice constant was observed to be decreased as smaller ionic radii Co²⁺ (0.74 Å) replaced the higher ionic radii Zn²⁺ (0.82 Å). The presence of tetrahedral and octahedral bands was confirmed by FTIR spectra. Optical bandgap energy was determined in the range of 4.44–2.05 eV for x = 0.0 to 0.4 nanoferrites, respectively. DC electrical resistivity was measured and showed an increasing trend (5.42 × 10⁸ to 6.48 × 10⁸ Ω·cm) with the addition of cobalt contents as cobalt is more conductive than zinc. The range of DC electrical resistivity (10⁸ ohm-cm) makes these nanomaterials potential candidates for telecommunication devices.     

Moments of the asset price for the Barndorff-Nielsen and Shephard model

In this paper, we derive closed-form formulas for moments of the asset price in the Barndorff-Nielsen and Shephard (BN–S) stochastic volatility model. We also present similar results where the market is driven by a BN–S-type stochastic process. It is shown that in both cases the results depend on the cumulant transform of the background driving Lévy process for the models. In this paper, we have also obtain various approximate expressions for the expected value of the square-root process for the shifted asset price with respect to the BN–S model.