A brief review on structural concepts of novel supramolecular proton transfer compounds and their metal complexes

Our research group has been interested in synthesis of proton transfer compounds as new supramolecular synthons for the onepot preparation of self-assembled transition metal complex-organo-networks since 2000. We have focused on the proton delivery from acids, which are considered as suitable proton donors, to amines as proton acceptors. The results were production of several proton transfer ion pairs possessing some remaining donor sites applied for coordination to metallic centers in preparation of metal-organic structures. Some of the complexes showed contributions of both cationic and anionic fragments of the starting ion pair, while some others contained only one of these species as ligand. Much of the investigations on reviewed compounds focused on the concept of supramolecular systems, co-crystallization, stereochemically active lone pairs, coordination polyhedron and mainly on various interactions involve including van der Waals, ion pairing, hydrogen bondings, face to face π-π stackings and edge to face C-H...π, C-O...π, N-H...π, S-O...π, Ti...π and Hg-Cl...π interactions. The mentioned interactions are the most commonly used strategies in the extension of supramolecular structures.     

Polyvinylpolypyrrolidone-bound boron trifluoride (PVPP-BF3); a mild and efficient catalyst for synthesis of 4-metyl coumarins via the Pechmann reaction

Polyvinylpolypyrrolidone-supported boron trifluoride has been studied for synthesis of 4-methyl coumarin by the Pechmann reaction. The reaction proceeded smoothly with hydroxyl phenols and ethyl acetoacetate in good yields in ethanol at reflux conditions. The polyvinylpolypyrrolidone-boron trifluoride complex is a non-corrosive and stable solid catalyst elevated Lewis acid property.     

Some Physico-Chemical and Biological Properties of Triazeno Sugars

Replacement of the alkyl group of l-aryl-3-alkyltriazenes with a sugar moiety did not significantly modify their tautomeric behaviour. The same replacement done on 1-aryl-3-alkyl-3-methyl-triazenes did not affect to any large extent their rotameric properties. In contrast, the most prominent biological properties, anticancer activity and toxicity, of 1-aryl-3-methyltria-zenes disappeared on replacement of the methyl group with a sugar moiety. Unexpectedly, the N-acetyltriazene 15 was highly cyto-toxic.     

Controllable one-step synthesis of ZnO nanostructures using molybdophosphoric acid

ZnO nanostructures were synthesised in a hydrothermal reaction of zinc acetate in the presence of molybdophosphoric acid (H₃[PMo₁₂O₄₀]) as well as its vanadium-substituted acid (H₄[PMo₁₁VO₄₀]) at various times, temperatures, and concentrations. The ZnO nanostructures were characterised by X-ray diffraction, transmission electron microscopy, and Fourier transform infrared spectroscopy. The results demonstrated that the synthesised products are crystalline with a zincite hexagonal phase. Various ZnO nanostructures, such as nanoparticles, microrods, and nanosheets, were produced by changing the experimental conditions. The photocatalytic degradation of methyl orange was also investigated using the ZnO nanoparticles thus prepared. These particles exhibited high performance in the photocatalytic degradation of MO and almost 100 % decolourisation occurred within only 20 min.     

A new robust DEA model and super-efficiency measure

Applications of traditional data envelopments analysis (DEA) models require knowledge of crisp input and output data. However, the real-world problems often deal with imprecise or ambiguous data. In this paper, the problem of considering uncertainty in the equality constraints is analyzed and by using the equivalent form of CCR model, a suitable robust DEA model is derived in order to analyze the efficiency of decision-making units (DMUs) under the assumption of uncertainty in both input and output spaces. The new model based on the robust optimization approach is suggested. Using the proposed model, it is possible to evaluate the efficiency of the DMUs in the presence of uncertainty in a fewer steps compared to other models. In addition, using the new proposed robust DEA model and envelopment form of CCR model, two linear robust super-efficiency models for complete ranking of DMUs are proposed. Two different case studies of different contexts are taken as numerical examples in order to compare the proposed model with other approaches. The examples also illustrate various possible applications of new models.     

Light expanded clay aggregate (LECA) as a support for TiO<Subscript>2</Subscript>, Fe/TiO<Subscript>2</Subscript>, and Cu/TiO<Subscript>2</Subscript> nanocrystalline photocatalysts: a comparative study on the structure,morphology, and activity

In this work, TiO₂ and doped TiO₂ photocatalysts (Fe/TiO₂ and Cu/TiO₂) were synthesized by the sol–gel method. The main objective of this study was to investigate the influence of dopants on the structure, morphology, and activity of the catalysts in powder and immobilized states. XRF, XRD, and SEM methods were used to characterize the catalysts. The structure and phase distribution of the nanocrystalline powders were identified by XRD. Nanoparticles crystallite size and the degree of crystallinity were affected by doping. The anatase contents of catalysts were achieved as follows: TiO₂ (5.89 %) < Fe/TiO₂ (42.17 %) < Cu/TiO₂ (70.28 %). It was indicated that the activity of the catalysts strongly depends on the anatase content. Under the same circumstances, copper-modified TiO₂ exhibited a twofold higher photocatalytic activity compared with TiO₂. The nanostructured catalysts were immobilized on light expanded clay aggregate (LECA) granules in order to investigate the effect of a novel support on the activity of the catalysts. Morphological changes are recognizable in the SEM images. Activity tests indicated that the best catalytic performance was assigned to Cu/TiO₂/LECA. After 120 min of irradiation, 61 % degradation of phenol in synthetic wastewater was achieved. The high photocatalytic activity of Cu/TiO₂/LECA confirms that LECA is as an excellent support.     

Sensitivity computations of eddy viscosity models with an application in drag computation

This paper presents a numerical study of the sensitivity of an eddy viscosity model with respect to the variation of the eddy viscosity parameter for the two‐dimensional driven cavity problem and flow around a cylinder. The main objective is to provide a comparison between computing the sensitivity using sensitivity equation and computing the sensitivity using finite difference methods and also numerically illustrate the application of the sensitivity computations in improving drag flow functional. Copyright © 2006 John Wiley & Sons, Ltd.     

Novel Complexes of Gallium(III), Indium(III), and Thallium(III) with Pyridine‐Containing Proton Transfer Ion Pairs Obtained from Dipicolinic Acid – Synthesis,Characterization and X‐ray Crystal Structure

Three new complexes of group thirteen metals, gallium(III), indium(III), and thallium(III) with proton transfer compounds, obtained from 2,6‐pyridinedicarboxylic acid (dipicolinic acid), were synthesized and characterized using elemental analysis, IR, ¹H and ¹³C NMR spectroscopy and single crystal X‐ray diffraction. The gallium(III) and indium(III) complexes were prepared using (pydaH₂)(pydc) (pyda = 2,6‐pyridinediamine, pydcH₂ = dipicolinic acid) and thallium(III) complex was obtained from (creatH)(pydcH) (creat = creatinine). The chemical formulae and space groups of the complexes are (pydaH)[Ga(pydc)₂] · 3.25H₂O · CH₃OH, ( 1 ), [In(pydc)(pydcH)(H₂O)₂] · 5H₂O, Pna2₁ ( 2 ) and [Tl₂(pydcH)₃(pydc)(H₂O)₂], ( 3 ). Non‐covalent interactions such as ion‐pairing, hydrogen bonding and π‐π stacking are discussed. The complexation reactions of pyda, pydc, and pyda + pydc with In³⁺ and Ga³⁺ ions in aqueous solution were investigated by potentiometric pH titrations, and the equilibrium constants for all major complexes formed are described.     

Carbon–carbon coupling reactions catalyzed by supported Pd porphyrins

The tetrakis(4‐N‐methylpyridinium)porphyrinatopalladium(II) iodide, [Pd(TMPyP)]I₄, supported on Dowex 50WX8 and Amberlite IR‐120 ion‐exchange resins, was used as heterogeneous, recyclable and active catalyst for the Suzuki–Miyaura and Heck cross‐coupling reactions. These catalysts were applied to coupling of various aryl halides with phenylboronic acid and styrene in Suzuki and Heck reactions, respectively, and the corresponding products were obtained in excellent yields and short reaction times. The catalysts could be recovered easily by simple filtration and reused several times without significant loss of their catalytic activity. The catalysts were characterized by diffuse‐reflectance UV–visible spectroscopy and scanning electron microscopy, and their stability was confirmed by TGA. Copyright © 2014 John Wiley & Sons, Ltd.