Volume 72, Issue 12

An efficient approach for the synthesis of oxazoles through the Van Leusen reaction in the presence of β-cyclodextrin is described. In aqueous medium using β-cyclodextrin as a supramolecular catalyst, tosylmethyl isocyanide was deprotonated by triethylamine and subsequently underwent an addition/cyclization reaction with aldehydes to produce corresponding oxazoles in excellent yields. This protocol improves the Van Leusen reaction with the use of catalytic amounts of base at low temperature in green media.

We report a class of organic–inorganic hybrid material based on nano-colloidal silica-tethered polyhedral oligomeric silsesquioxanes with eight branches of 3-aminopropyltriethoxysilane [nano-colloidal silica@APTPOSS (a series of polyhedral oligomeric silsesquioxanes with eight branches of 3-aminopropyltriethoxysilane)]. It was characterized by 1 H NMR spectroscopy, dynamic light scattering, scanning electron microscope, energy dispersive spectroscopy and thermogravimetric analysis. An easy and rapid method for the synthesis of bis-thiazolidinones has been presented by one-pot pseudo-five-component reaction of benzaldehydes, ethylenediamine and 2-mercaptoacetic acid using nano-colloidal silica@APTPOSS. The reusability of the catalyst and little catalyst loading, excellent yields, short reaction times, using the sonochemical procedure as a green process and an alternative energy source are some benefits of this method.

The neutral, four-fold protonated pyridine-3,5-dicarbox(3,5-dicarboxylatoanilide) (H 4 L) reacts with Mn(II) salts under hydrothermal conditions to yield a new complex: [Mn 2 (L)(H 2 O) 2 ]·H 2 O ( 1 ), which has been characterized by single crystal X-ray diffraction, infrared spectroscopy, and elemental and thermogravimetric analyses. Complex 1 exhibits a binodal (4,8)-connected 3D framework with flu (4 12 .6 12 .8 4 )(4 6 ) 2 topology. The magnetic properties of 1 were investigated.

The synthesis of three neutral bis-cyclometalated iridium(III) complexes [Ir(pba) 2 (S^S)] (pbaH=4-(2-pyridyl)benzaldehyde; S^S=Et 2 NCS 2 − ( 1 ), i PrOCS 2 − ( 2 ), ( n PrO) 2 PS 2 − ( 3 )) from [{Ir( μ -Cl)(pba) 2 } 2 ] and the corresponding sodium or potassium dithiolates in methanol-dichloromethane is described. The composition of complexes 1–3 is discussed on the basis of 1 H NMR, 13 C NMR, IR, and mass spectroscopy, and the crystal structures of 1 and 3 were determined by X-ray crystallography. The absorption and emission spectra show that the [Ir(pba) 2 (S^S)] complexes may be effective candidates as green-emitting phosphorescent materials. The stability of the three cyclometalated iridium(III) complexes towards different transition metal ions was also investigated in acetonitrile-water solvent.

The tetranuclear Zn(II) complex, [{ZnL( μ -OAc)Zn(CH 3 CH 2 CH 2 OH)} 2 ], derived from an asymmetrical Salamo-type chelate ligand H 3 L (5-methoxy-6′-hydroxy-2,2′-[ethanedioxybis(nitrilomethylidyne)]diphenol) has been synthesized and structurally characterized by elemental analysis, IR spectrum, X-ray crystallography, UV/Vis and fluorescence spectra. The structure is made up of four Zn(II) atoms, μ 2 -coordinated acetate ions and two coordinated n -propanol molecules, and forms an infinite one-dimensional supramolecular structure via intermolecular C–H···π interactions. The four Zn(II) atoms are penta-coordinated and show slightly distorted trigonal bipyramidal and tetragonal pyramidal symmetries.

Bioassay-guided fractionation of Aloe vera (L.) Burm.f. resulted in the isolation and characterization of one new C -glucosyl chromone, 7-methoxy-6′- O -coumaroylaloesin ( 1 ), along with the known dihydroisocoumarin feralolide ( 2 ). The structure of 1 was elucidated on the basis of 1D, 2D-NMR, and mass spectrometry. Both compounds 1 and 2 were tested for their effects on the growth of cancer cells in culture and it was observed that unlike compound 1 , compound 2 displayed concentration-dependent antiproliferative effects on breast cancer cells (MDA-MB-231) and ovarian cancer cells (SKOV-3). Additionally, only feralolide ( 2 ) demonstrated good urease, weak α -glucosidase enzyme inhibition, and weak antioxidant effects.

Li 3 K 3 Eu 7 (BO 3 ) 9 was prepared by high-temperature solid state synthesis at 900°C in a platinum crucible from lithium carbonate, potassium carbonate, boric acid, and europium(III) oxide. The title compound crystallizes in the orthorhombic space group Pca 2 1 (no. 29) ( Z =4). The structure was refined from single-crystal X-ray diffraction data: a =21.126(2), b =6.502(2), c =17.619(2) Å, V =2420.1(2) Å 3 , R 1=0.0183 and wR 2=0.0412 for all data. The crystal structure of Li 3 K 3 Eu 7 (BO 3 ) 9 is isotypic to Li 3 K 3 Y 7 (BO 3 ) 9 featuring isolated BO 3 units and LiO 6 octahedra forming [Li 3 B 4 O 21 ] units in the ac plane, which are linked by additional BO 3 units. The K + and Eu 3+ cations are arranged in the cavities of the structure.

Ni 6 B 22 O 39 ·H 2 O was synthesized in a high-pressure/high-temperature reaction at 5 GPa/900°C. It crystallizes in the orthorhombic space group Pmn 2 1 (no. 31) with the lattice parameters a =7.664(2), b =8.121(2) and c =17.402(2) Å. The crystal structure is discussed with regard to the isotypic compounds M 6 B 22 O 39 ·H 2 O ( M =Fe, Co) and the structurally related phase Cd 6 B 22 O 39 ·H 2 O. Furthermore, the characterization of Ni 6 B 22 O 39 ·H 2 O via X-ray powder diffraction and vibrational spectroscopy is reported.

α -Y 2 B 4 O 9 was synthesized in a high-pressure/high-temperature experiment at 12.3 GPa/1020°C. The crystal structure has been determined via single-crystal X-ray diffraction. α -Y 2 B 4 O 9 is isotypic to the lanthanide borates α - Ln 2 B 4 O 9 ( Ln =Sm–Ho) and crystallizes in the monoclinic space group C 2/ c (no. 15) with the following lattice parameters: a =25.084(2), b =4.3913(2), c =24.726(2) Å, and β =99.97(1)°. The compound was further characterized via X-ray powder diffraction as well as IR and Raman spectroscopy.

β -Y(BO 2 ) 3 was synthesized in a Walker-type multianvil module at 5.9 GPa/1000°C. The crystal structure has been elucidated through single-crystal X-ray diffraction. β -Y(BO 2 ) 3 crystallizes in the orthorhombic space group Pnma (no. 62) with the lattice parameters a = 15.886(2), b = 7.3860(6), and c = 12.2119(9) Å. Its crystal structure will be discussed in the context of the isotypic lanthanide borates β - Ln (BO 2 ) 3 ( Ln = Nd, Sm, Gd–Lu).

The plumbide EuPdPb was synthesized in polycrystalline form by reaction of the elements in a sealed niobium ampoule in a muffle furnace. The structure was refined from single-crystal X-ray diffractometer data: TiNiSi type, Pnma , a =752.4(2), b =476.0(2), c =826.8(2) pm, wR 2=0.0485, 704 F 2 values and 20 variables. The europium atoms are coordinated by two tilted and puckered Pd 3 Pb 3 hexagons (280–289 pm Pd–Pb) with pronounced Eu–Pd bonding (312–339 pm). Temperature-dependent magnetic susceptibility measurements show Curie-Weiss behaviour and an experimental magnetic moment of 7.35(1) μ B per Eu atom. EuPdPb orders antiferromagnetically at T N =13.8(5) K and shows a metamagnetic transition at a critical field of 15 kOe. 151 Eu Mössbauer spectra confirm divalent europium ( δ =–10.04(1) mm s −1 ) and show full magnetic hyperfine field splitting ( B hf =21.1(1) T) at 6 K.

Transparent-yellow single crystals of YbF 2 were obtained as only crystalline product from the solid-state reaction of Yb and teflon designed to yield ‘Yb 3 C 3 F 2 ’ in addition to some amorphous black material. The first single-crystal structure determination of YbF 2 (cubic space group Fm 3̅ m , CaF 2 -type structure, a =559.46(16) pm; R 1=1.2%, wR 2=3.2%) was the starting point to compare isostructural binary fluorides M F 2 and hydrides M H 2 ( M =Ca, Yb, Eu, Sr and Ba) exhibiting an as-yet unexplained small volume per formula unit for YbH 2 .