Anion binding vs. deprotonation in colorimetric pyrrolylamidothiourea based anion sensors

A pyrrolylamidothiourea deprotonates in the presence of one equivalent of not only fluoride, but also acetate, benzoate or dihydrogen phosphate in DMSO solution with structural studies using synchrotron radiation confirming thiourea deprotonation in the solid state.     

A general route to protected quaternary alpha-amino acids from beta-amino alcohols via a stereocontrolled radical approach

A radical-based approach facilitates the highly stereocontrolled functionalisation of beta-amino alcohols, opening up a new, generally applicable methodology for the preparation of quaternary alpha-amino acids.     

Anion-binding modes in a macrocyclic amidourea

A macrocyclic amidourea shows anion dependent binding modes with a variety of different putative anionic guests.     

A slow gravity compensated atom laser

We report on a slow guided atom laser beam outcoupled from a Bose–Einstein condensate of ⁸⁷Rb atoms in a hybrid trap. The acceleration of the atom laser beam can be controlled by compensating the gravitational acceleration and we reach residual accelerations as low as 0.0027 g. The outcoupling mechanism allows for the production of a constant flux of 4.5×10⁶ atoms per second and due to transverse guiding we obtain an upper limit for the mean beam width of 4.6 μm. The transverse velocity spread is only 0.2 mm/s and thus an upper limit for the beam quality parameter is M ²=2.5. We demonstrate the potential of the long interrogation times available with this atom laser beam by measuring the trap frequency in a single measurement. The small beam width together with the long evolution and interrogation time makes this atom laser beam a promising tool for continuous interferometric measurements.     

Two-dimensional crystal growth and stacking of bis(phthalocyaninato) rare earth sandwich complexes at the 1-phenyloctane/graphite interface

Initial stages of two-dimensional crystal growth of the double-decker sandwich complex Lu(Pc*)2 [Pc* = 2,3,9,10,16,17,23,24-octakis(octyloxy)phthalocyaninato] have been studied by scanning tunneling microscopy at the liquid/solid interface between 1-phenyloctane and highly oriented pyrolytic graphite. High-resolution images strongly suggest alignment of the double-decker molecules into monolayers with the phthalocyanine rings parallel to the surface. Domains were observed with either hexagonal or quadrate packing motifs, and the growing interface of the layer was imaged. Molecular resolution was achieved, and the face of the phthalocyanine rings appeared as somewhat diffuse circular features. The alkyl chains are proposed to be interdigitating to maintain planar side-by-side packing.     

Polymer‐free,low tension graphene mechanical resonators

Graphene resonators are fabricated using a polymer‐free, direct transfer method onto metal reinforced holey carbon grids. The resonators are distinguished by the absence of organic residues and excellent crystallinity. The normal mode frequencies are measured using a Fabry–Perot technique; resonance curves indicate highly linear behaviour but very little built‐in strain, which is consistent with device geometry examined by atomic force microscopy. We conclude that the oscillators' restoring force is due instead to graphene's intrinsic bending rigidity; our measurements indicate a value of approximately 1.0 eV, consistent with previous theoretical and experimental work. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Colorimetric determination of molybdenum with disodium-1,2-dihydroxybenzene-3,5-disulfonate

A procedure for the colorimetric determination of molybdenum with disodium-1, 2-dihydroxybenzene-3,5-disulfonate (Tiron) has been presented. The maximum absorbancy of the yellow colored complex is at 390 mμ the optimum pH range is 6.6-7.5; and the Tiron concentration is 1.5-2%.The color reaction conforms to Beer's law and has a practical sensitivity of 0.1 p.p.m. molybdenum. The color formation is instantaneous and stable for at least three weeks. There is no temperature effect over the range of 15° — 40° C.The tolerances of the colored complex to many diverse ions have been established. The separation of molybdenum from interfering ions is accomplished by precipitation of the former with α-benzoinoxime. Molybdenum and tungsten are separated photometrically.The colorimetric determination of molybdenum with Tiron was successfully applied to a variety of steels and other materials.     

Efficient synthesis of (3R,3aS,6aR)- hexahydrofuro[2,3-b]furan-3-ol from glycolaldehyde

A one-step diastereoselective (up to 98:2) synthesis of the bis-furan alcohol of Darunavir and other HIV drug candidates has been achieved utilizing the novel cyclization of glycolaldehyde and 2,3-dihydrofuran. The cycloaddition was catalyzed by a variety of catalysts including those formed from tin(II) triflate and common chiral ligands such as BINAP and Evans's box ligands. An efficient and unique enzymatic process enhanced the enantiomeric purity to provide the target in optically pure form.     

Anion binding vs. sulfonamide deprotonation in functionalised ureas

Sulfonamide groups, commonly used as neutral hydrogen bond donors in a wide variety of anion receptors, deprotonate upon addition of certain basic anionic guests in two simple functionalised ureas.     

1,3-diindolylureas and 1,3-diindolylthioureas: anion complexation studies in solution and the solid state

1,3-Diindolylureas and thioureas have been synthesised and their anion complexation properties in solution studied. Whilst diindolylthioureas showed only moderate affinities and selectivities, diindolylureas show remarkably high affinity for dihydrogen phosphate in solution for an acyclic, neutral receptor in water/[D(6)]DMSO mixtures. These easy-to-make compounds adopt relatively planar conformations in the solid-state and are able to donate four hydrogen bonds and yet not fill the coordination sphere of carbonate or phosphate, allowing two or three receptors to bind to each anion in the solid-state.