Homogeneous oxidation reactions catalysed by in situ-generated triazolylidene copper(I) complexes

Transition Metal Chemistry - Four new Cu complexes bearing triazolylidene ligands 1-(R)-3-methyl-4-phenyl-1H-1,2,3-triazol-3-ium-5-yl: R?=?phenyl (2a), mesitylenyl (2b), propyl (2c),...     

NH3 gas sensing properties of nanocrystalline ZnO based thick films

Zinc acetate derived precursor used in the present sol-gel synthesis of zinc oxide nanoparticles is described. The reaction product obtained before and after reflux of propanolic zinc acetate solution have been studied by UV-vis, photoluminescence and FT-IR studies which confirm the formation of oligomeric precursor Zn4O(Ac)6 (Ac=CH3COO). The formation of approximately 7 nm zinc oxide nanoparticles were confirmed by X-ray diffraction (XRD) and Transmission electron microscopic studies (TEM). The gaseous ammonia gas sensing characteristics of the nano-zinc oxide sensor showed high sensitivity compared to sensor fabricated with commercial zinc oxide powder.     

Second‐sphere coordination in anion binding: sodium hexa­ammine­cobalt(III) tetra­kis­(4‐fluoro­benzoate) monohydrate

In sodium hexa­amminecobalt(III) tetra­kis­(4‐fluoro­benzoate) monohydrate, Na[Co(NH₃)₆](C₇H₄FO₂)₄·H₂O, determined at 180 K, [Co(NH₃)₆]³⁺ cations lie on centres of inversion and form layers in which their C₄ axes lie perpendicular to the layer planes. 4‐Fluoro­benzoate anions lie on twofold axes and general positions and adopt near‐planar geometries. Na⁺ cations and water mol­ecules lie on twofold axes, forming [NaO₅] square pyramids that lie between the [Co(NH₃)₆]³⁺ cations. The second‐sphere inter­actions between [Co(NH₃)₆]³⁺ cations and 4‐fluorobenzoate anions comprise edge‐to‐face and vertex‐to‐face arrangements. The structure is closely comparable with that of the benzoic acid salt, demonstrating that fluorination of the anion in the para position has no significant influence on the second‐sphere inter­actions and minimal influence on the gross crystal structure.     

Nanoparticulate metal complexes prepared with compressed carbon dioxide: correlation of particle morphology with precursor structure

Nanoparticles of metal complexes are rare because of the limited methods for their preparation. Described in this communication is the use of precipitation with compressed antisolvent (PCA) to process nanoparticles of neutral metal-salen complexes. PCA is a semicontinuous technique utilizing supercritical carbon dioxide (scCO2) as the precipitant. The scCO2 dissolves into a solution of the complex and simultaneously extracts the solvent, resulting in formation of nanoparticles of uniform morphology. Spectroscopic and analytical methods were used to support the assignment that the nanoparticles are composed of metal complexes. Scanning electron microscopy reveals that planar complexes, such as [NiIIsalen], afford rodlike particles with average diameter and length of 85 and 700 nm, respectively. Complexes with nonplanar molecular structures produce nanoparticles with varied structures; for instance, PCA of the six-coordinate [Ru(salen)(NO)(Cl)] complex yields spherical nanoparticles with average diameters of 50 nm. These findings suggest a correlation between the structures of molecular precursors and the morphology of the processed particles, which possibly could be used as a bottom-up approach to the preparation of functional nanoparticles.     

1,6-Hexanedithiol monolayer as a receptor for specific recognition of alkylmercury

1,6-Hexanedithiol monolayer acts as an unusually specific recognition agent for CH3Hg+ when the microcantilever is used as the transducer; the mechanism of the sensor is discussed.     

Phase transfer of oleic acid capped Ni(core)Ag(shell) nanoparticles assisted by the flexibility of oleic acid on the surface of silver

The phase transfer protocols in vogue for the oleic acid capped silver nanoparticles, viz., salt-induced precipitation and redispersion or phosphoric acid-induced method, are examined and compared thoroughly. A comprehensive evaluation with respect to the mechanistic aspects involved is made and the merits and demerits of the different procedures are delineated. It is found that the salt-induced precipitation and redispersion is more versatile in that the precipitate can actually be redispersed in both aqueous and organic media. However, in terms of mechanism both the routes seem to be very similar wherein the orientational change of oleic acid on the silver surface in the two different environments-organic and aqueous-plays a crucial role in the adaptability of the system to the different environments. Subsequently, this change of orientation of oleic acid on silver surface in aqueous and organic media has been utilized to phase transfer Ni-based nanoparticulate systems. The nascent oleic acid-capped Ni nanoparticles, which were synthesized by a foam-based protocol, were dispersible in water but not in nonpolar organic media such as cyclohexane or toluene. Then, just by coating a thin shell of silver on them we could achieve complete phase transfer of the Ni(core)Ag(shell) from aqueous to organic media following similar procedures used for oleic acid-capped silver nanoparticles. Here, the phase transfer seems to be facilitated by the orientational flexibility of oleic acid on the silver surface as opposed to other metal surfaces as evidenced from the infrared and thermogravimetric analyses of oleic acid-capped Ni and Ni(core)Ag(shell) nanoparticles. This orientation-assisted phase transfer method could be generalized and can be adapted to other systems where, if the nascent nanoparticles cannot be phase transferred as is, they can be coated by a silver shell and oleic acid making them suitable for dispersion in both aqueous and organic media.     

Colorimetric determination of microgram quantities of isonicotinic acid hydrazide (isoniazid)

Microchimica Acta - The orange yellow colour of the vanadium(V)-isoniazid complex measured at 420 nm (Filter No. 42) is utilized as the basis for the colorimetric determination of isoniazid in the...     

Self-assembly of octarhenium-based neutral luminescent rectangular prisms

Self-assembly of rhenium-based nanoscale rectangular prismatic boxes has been achieved in quantitative conversion. The fac-rhenium corner provided three mutually perpendicular coordination sites and served as a good candidate for the construction of 3-D boxes. These are the first Re-based, neutral, luminescent prisms of M(8)L(2)L'(8) type that has been characterized crystallographically. Their luminescent properties and molecular recognition capabilities make these molecular prisms interesting supramolecules.