Polyoxometalate–molybdenylacetylacetonate hybrid complex: A reusable and efficient catalyst for oxidation of alkenes with tert-butylhydroperoxide

The hybrid complex consist of molybdenylacetylacetonate complex covalently linked to a lacunary Keggin-type polyoxometalate, K₈[SiW₁₁O₃₉] (POM), was synthesized and characterized by elemental analysis, SEM, XRD, diffuse reflectance UV–Vis and FT-IR spectroscopic methods. The hybrid complex, [MoO₂(acac)–POM] (1), was used for alkene epoxidation with tert-BuOOH in 1,2-dichloroethane as solvent. The complex (1) can catalyze epoxidation of various olefins including non-activated terminal olefins. The effect of reaction parameters such as oxidant, solvent, and temperature on the epoxidation of cyclooctene was also investigated. This heterogeneous catalyst was reused several times in the oxidation of cyclooctene.     

Highly efficient dye-sensitized solar cell prepared by electrophoretic deposition method: the effect of TiO<Subscript>2</Subscript> films thickness on the performance of cells

In this work, nanocrystalline P25 TiO₂ films with different thicknesses were deposited on FTO coated glass substrates by an electrophoretic deposition technique (EPD) and applied as the work electrode for dye-sensitized solar cells (DSSC) using cis-bis(isothiocyanato)(2,2'-bipyridyl-4,4'-dicarboxylato)(4,4'di-nonyl-2'-bipyridyl) ruthenium(II) (Z907, Dyesol) as sensitizing dye.The results showed that the increasing the thickness of TiO₂ films lead to increase the adsorption of the dye on the TiO₂ layers which in turns improved the short-circuit photocurrent (J_sc) and open-circuit voltage (V_oc), respectively. Furthermore, it was found that the effects of the surface states on the recombination of the photo-injected electrons (electron–hole pairs) in the TiO₂ films strongly depend on theTiO₂ electrode annealing temperature. Finally, a DSSC with a 32.82 μm thickness for TiO₂ film annealed at 600°C produced the highest conversion efficiency with an incident solar energy of 100 mW/cm² (η = 8.23%, J_sc = 15.98, V_oc = 0.73, FF = 0.7).     

Catalytic oxidation of olefins with hydrogen peroxide catalyzed by [Fe(III)(salen)Cl] complex covalently linked to polyoxometalate

The catalytic activity of a hybrid compound [Fe(salen)-POM] (1) consisting of Fe(III)(salen)Cl [H₂salen = N,N′-bis(salicylidene)ethylenediamine] complex covalently linked to a Keggin type polyoxometalate, K₈SiW₁₁O₃₉, (POM) was studied in the oxidation of various olefins in acetonitrile, using hydrogen peroxide as oxygen source. While, [Fe(salen)-POM] catalyst showed moderate to good catalytic activity and product selectivity in the oxidation reactions, the complex Fe(III)(salen)Cl showed poor catalytic activity in these reactions. The effect of other parameters such solvent, oxidant, temperature and the metal type in Schiff base complex were also investigated.     

Nanomagnet-Bound Imidazole as a Heterogeneous Axial Ligand for MnIII(salophen)Cl: An Efficient, Recoverable and Recyclable Catalyst for Epoxidation of Alkenes with Sodium Periodate

Efficient alkene epoxidation with sodium periodate catalyzed by manganese(III) salophen supported on nanomagnetic materials is reported. First, the iron nanomagnets were silica coated, functionalized with imidazole and then manganese salophen was successfully bonded to their surface. The catalyst, [Mn^III(salophen)Cl]@SiIm-Fe, was characterized by elemental analysis, FT-IR and UV/Vis spectroscopic techniques, SEM and ICP. The [Mn^III(salophen)Cl]@SiIm-Fe was used for alkene epoxidation with sodium periodate at room temperature. Different aromatic and aliphatic terminal alkenes were epoxidized efficiently using sodium periodate as an oxidant. The effect of reaction parameters such as solvent and oxidant in the epoxidation of cis-cyclooctene was investigated. This new heterogenized epoxidation catalyst is easily recovered with a magnet and showed no appreciable loss of activity even after four consecutive runs.     

Physical synthesis of quantum circuits using templates

Similar to traditional CMOS circuits, quantum circuit design flow is divided into two main processes: logic synthesis and physical design. Addressing the limitations imposed on optimization of the quantum circuit metrics because of no information sharing between logic synthesis and physical design processes, the concept of “physical synthesis” was introduced for quantum circuit flow, and a few techniques were proposed for it. Following that concept, in this paper a new approach for physical synthesis inspired by template matching idea in quantum logic synthesis is proposed to improve the latency of quantum circuits. Experiments show that by using template matching as a physical synthesis approach, the latency of quantum circuits can be improved by more than 23.55 % on average.     

Oxidation of alkanes with hydrogen peroxide catalyzed by Schiff base complexes covalently anchored to polyoxometalate

The catalytic activity of a hybrid compound [Fe(salen)-POM] (1) consisting of metallosalen moiety, [Fe^III(salen)Cl], covalently linked to a Keggin type polyoxometalate, K₈SiW₁₁O₃₉ (POM), in the oxidation of hydrocarbons with hydrogen peroxide was investigated. Reaction products were identified by gas chromatography and satisfactory yields were obtained. While, the Fe(salen)-POM catalyst showed high catalytic activity and product selectivity in the oxidation reactions, the metallosalen alone, [Fe^III(salen)Cl], showed very poor catalytic activity in these reactions. The ability of various transition metal ions in this oxidation system was also investigated. Among a series of hybrid compounds, Fe(salen)-POM showed the highest activity.     

Application of tin(IV) porphyrin complexes as novel catalysts for the synthesis of new copolyurethanes with cyclopeptide moiety

New electron deficient tin(IV) porphyrins were used as efficient catalysts for the reaction of 4,4′‐methylene‐bis‐(4‐phenylisocyanate) (MDI), with L‐leucine anhydride cyclodipeptide (LAC) and polyethyleneglycol‐400 (PEG‐400) and the results were compared with those obtained in the presence of a commercial catalyst, dibutyltin dilaurate (DBTDL). Molar ratio of catalysts to MDI, polymerization reaction time, viscosity, and yield of the resulting poly(ether‐urethane‐urea)s (PEUU) were compared in the presence of different catalysts. The rate of N?C?O conversion in the presence of each catalysts under the same reaction conditions was also compared and followed by FT‐IR N?C?O absorption band. FT‐IR, GPC, and viscosity studies have shown that tin(IV) porphyrins afford higher viscosity and reaction progress. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Diastereoselective Synthesis of Pyrazolines using a Bifunctional Brønsted Acidic Ionic Liquid under Solvent‐Free Conditions

An efficient protocol for the excellent diastereoselective synthesis of pyrazolines via a three‐component reaction of aldehydes, hydrazines and dimethyl acetylenedicarboxylate (DMAD) in the presence of a bifunctional Brønsted acidic ionic liquid as a reusable catalyst under solvent‐free conditions is reported. Easy work‐up, short reaction times, high yields of the products and an environmentally benign procedure avoiding toxic organic solvents are other significant features of this method.