Magnetically nano core–shell Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>@Cu(OH)<Subscript>x</Subscript>: a highly efficient and reusable catalyst for rapid and green reduction of nitro compounds

Magnetically separable nano core–shell Fe₃O₄@Cu(OH)_x with 22 % Cu content was prepared by the addition of sodium hydroxide to a mixture of CuCl₂·2H₂O and nano Fe₃O₄ in water. Characterization of the impregnated copper hydroxide was carried out by X-ray fluorescence (XRF), X-ray diffraction (XRD) atomic absorption spectroscopy (AAS), scanning electron microscopy (SEM), value stream mapping (VSM) and Brunauer–Emmett–Teller (BET) analysis. The core–shell nanocatalyst exhibited the excellent catalytic activity toward reduction of various nitro compounds to the corresponding amines with NaBH₄. All reactions were carried out in H₂O (55–60 °C) within 3–15 min to afford amines in high to excellent yields. Reusability of core–shell Cu(OH)_x catalyst was examined 9 times without significant loss of its catalytic activity.     

On the intersection graph of a finite group

For a finite group G, the intersection graph of G which is denoted by Γ(G) is an undirected graph such that its vertices are all nontrivial proper subgroups of G and two distinct vertices H and K are adjacent when H ∩ K ≠ 1. In this paper we classify all finite groups whose intersection graphs are regular. Also, we find some results on the intersection graphs of simple groups and finally we study the structure of Aut(Γ(G)).     

Synthesis,spectroscopy, and X-ray crystal structures of copper(II) complexes of the tridentate ONS ligand formed by condensation of 4,4,4-trifluoro-1-(2-thienyl)-2,4-butanedione with S-benzyldithiocarbazate

A new tridentate ONS ligand, H₂L, has been synthesized by condensing thenoyltrifluoroacetone(4,4,4-trifluoro-1-(2-thienyl)-2,4butaneanedione) with S-benzyldithiocarbazate and its structure determined by X-ray diffraction. In the solid state, the Schiff base exists as the ketoamine-thioketo tautomer but in solution and in the presence of copper(II), it converts to the enol-thiol form and deprotonates to give copper(II) complexes of formula, [CuL] and [CuLL¹] (L = doubly deprotonated form of the ligand; L¹ = py, bipy or phen] which have been characterized by magnetic, spectroscopic, and X-ray diffraction studies. An X-ray crystallographic analysis shows that [CuL(py)] has a square-planar geometry with the ligand coordinated to the copper(II) center via the enolate oxygen, the azomethinic nitrogen and the thiolate sulfur, the fourth coordination position being occupied by pyridine. The [CuL(bipy)] complex is five-coordinate with a structure close to square-pyramidal in which the Schiff base acts as a doubly deprotonated tridentate ONS ligand and bipy is bidentate.     

1,3-Dibromo-5,5-dimethylhydantoin as an efficient homogeneous catalyst for synthesis of benzoxazoles, benzimidazoles, and oxazolo[4,5-b]pyridines

Abstract  

A simple and highly efficient method for synthesis of benzoxazoles, benzimidazoles, and oxazolo[4,5-b]pyridines is described. Condensation of orthoesters with o-substituted anilines or 2-amino-3-hydroxypyridine was performed in the presence of catalytic amounts of commercially available, inexpensive, and moisture-stable 1,3-dibromo-5,5-dimethylhydantoin under solvent-free conditions. The corresponding heterocycles were obtained in good to excellent yields. The main advantages of the present procedure are mild reaction conditions, short reaction times, high yields of products, easy work-up, and absence of solvent.     

Simultaneous determination of gliquidone, pioglitazone hydrochloride, and verapamil in formulation and human serum by RP-HPLC

In the present study, a reverse-phase high performance liquid chromatography method was developed, validated and applied for the simultaneous determination of gliquidone, pioglitazone hydrochloride and verapamil in tablets and human serum. Chromatographic separation was achieved on a C18 column (5 μm, 25 × 0.46 cm) with a mobile phase consisting of methanol-water-acetonitrile (80:10:10 v/v/v) with a flow rate of 0.7 mL/min and pH adjusted to 3.50 with phosphoric acid at 230 nm. Glibenclamide was used as internal standard. The experimentally derived limit of detection and limit of quantitation were determined to be 0.24, 0.93, 0.40, and 0.80, 3.11, 1.36 μg/mL for gliquidone, pioglitazone, and verapamil, respectively. There were no interfering peaks due to the excipients present in the pharmaceutical tablets. Thus, the proposed method is simple and suitable for the simultaneous analysis of active ingredients in dosage forms and human serum.     

Dicarboxylate-bridged (Mo2)n (n = 2, 3, 4) paddle-wheel complexes: potential intermediate building blocks for metal-organic frameworks

The treatment of the dimeric paddle-wheel (PW) compound [Mo(2)(NCCH(3))(10)][BF(4)](4)1 with oxalic acid (0.5 equiv.), 1,1-cyclobutanedicarboxylic acid (1 equiv.), 5-hydroxyisophthalic acid (1 equiv.) (m-bdc-OH) or 2,3,5,6-tetrafluoroterephthalic acid (0.5 or 1 equiv.) leads to the formation of macromolecular dicarboxylate-linked (Mo(2))(n) entities (n = 2, 3, 4). The structure of the compounds depends on the length and geometry of the organic linkers. In the case of oxalic acid, the dimeric compound [(CH(3)CN)(8)Mo(2)(OOC-COO)Mo(2)(NCCH(3))(8)][BF(4)](6)2 is formed selectively, whereas the use of 2,3,5,6-tetrafluoroterephthalic acid affords the square-shaped complex [(CH(3)CN)(6)Mo(2)(OOC-C(6)F(4)-COO)](4)[BF(4)](8)3. Bent linkers with a bridging angle of 109° and 120°, respectively, lead to the formation of the molecular loop [(CH(3)CN)(6)Mo(2)(OOC-C(4)H(6)-COO)](2)[BF(4)](4)4 and the bowl-shaped molecular triangle [(CH(3)CN)(6)Mo(2)(m-bdc-OH)](3)[BF(4)](6)5. All complexes are characterised by X-ray single crystal diffraction, NMR ((1)H, (11)B, (13)C and (19)F) and UV-Vis spectroscopy.     

Quasirecognition by prime graph of finite simple groups L n (2) and U n (2)

Let G be a finite group. The prime graph ??(G) of G is defined as follows. The vertices of ??(G) are the primes dividing the order of G and two distinct vertices p, p?? are joined by an edge if G has an element of order pp??. Let L=L _n (2) or U _n (2), where n?R17. We prove that L is quasirecognizable by prime graph, i.e. if G is a finite group such that ??(G)=??(L), then G has a unique nonabelian composition factor isomorphic to L. As a consequence of our result we give a new proof for the recognition by element orders of L _n (2). Also we conclude that the simple group U _n (2) is quasirecognizable by element orders.     

Stability analysis of graphene based laminated composite sheets under non-uniform inplane loading by nonlocal elasticity

Size dependent buckling of composite laminates made of isotropic graphene layers interlaid with bonding agents is considered. Nonlocal theory of elasticity is used in the buckling analysis to reflect the size scale effects on the critical buckling loads which is discussed in detail. The method is capable of predicting the relative buckling modes for non-uniform inplane loading applied through the thickness of the laminate. All modes of buckling in which the layers may displace together or opposite one another are investigated to study their scale dependent effects. Displacement or load controls are implemented through independent parameters as constraints to form special combination of buckling modes. Each graphene sheet is considered as a Kirchhoff plate model. The interlaid bonding agent is laterally treated as Winkler elastic foundation between graphene layers while neglecting their other load carrying capacities. Various numerical results are obtained reflecting the nonlocality effects. It is observed that in cases of higher load ratios and simpler buckling modes, the effect of nonlocality tends to drastically increase. The results of simpler examples studied are verified by another reference.     

Recent advances in oxidation catalysis using ionic liquids as solvents

Ionic liquids are an interesting alternative to classical solvents presenting several advantages. A variety of catalysts show good or even enhanced activities when applied in ionic liquids. Oxidation catalysis represents a large segment of industrial chemistry, providing both bulk chemicals and intermediates for high value added special products and pharmaceuticals. Particularly for the latter products organometallic and inorganic catalysts are being developed that can be applied in systems consisting of or containing ionic liquids. This work provides an overview on recent developments in this field.