Highly Substituted Δ3-1,2,3-Triazolines: Solid-State Emitters with Electrofluorochromic Behavior

Highly substituted Δ³-1,2,3-triazolines can be prepared by reaction of triarylvinyl Grignard reagents with functionalized organic azides. The heterocycles are fluorescent in the solid state, and—depending on the substituents—they can display aggregation-induced emission. Upon oxidation, the triazolines form stable radical cations with altered photophysical properties. Therefore, they represent rare examples of solid-state emitters with intrinsic electrofluorochromic behavior.     

Nanohydroxyapatite and its textures as potential carriers of promising short-lived lead isotopes

Russian Chemical Bulletin - The possibility of sorption and cocrystallization binding of lead(n) with nanohydroxyapatite (HAP) acting as a potential carrier of short-lived lead radionuclides...     

Easy to optimize: dynamic combinatorial libraries of metal-dye complexes as flexible sensors for tripeptides

A dynamic combinatorial library (DCL) of dye complexes of Cu2+ and Ni2+ was used to sense the sequence isomeric tripeptides His-Gly-Gly, Gly-His-Gly, and Gly-Gly-His. The DCL sensor was obtained by mixing buffered aqueous solution of three commercially available dyes together with CuCl2 and NiCl2. The addition of the peptide analytes resulted in characteristic changes in the UV-vis spectrum of the mixture, which allowed the identification of the peptide. Due to the modular nature of the sensor, it was possible to optimize the sensor by variation of the amounts and ratio of its constituent building blocks. The composition of the best sensor was found to vary substantially, depending on the sensing problem to be addressed. Whereas a Cu2+/Ni2+ ratio of 1:3 gave the best differentiation for Gly-His-Gly and Gly-Gly-His, a sensor containing exclusively Cu2+ was found to provide the best discrimination between His-Gly-Gly and Gly-Gly-His.     

Higher order stability effects in a natural convection boundary layer over a vertical heated wall

 The stability of a laminar boundary layer flow under natural convection on a vertical isothermally heated wall is studied analytically. The analysis is performed by using two different two-dimensional linear models: (1) The non-parallel flow model in which the steady mean flow as well as the disturbance amplitude functions can change in the streamwise direction; (2) The parallel flow model in which the effects of the mean flow and disturbance changes in the streamwise direction are neglected. The linear non-parallel stability analysis is based on the so-called parabolised stability equations (PSEs) which have been successfully applied to the stability analysis of forced convection boundary layers. In this study the PSE equations are applied to natural convection boundary layers in order to show the difference between parallel and non-parallel stability analysis. A second part of this study deals with the effects of variable properties, which are always present in natural convection flows. They are analysed by an extended version of the Orr–Sommerfeld equation (EOSE). Received on 31 May 2000     

Reactions of Alkynes with [RuCl(cyclopentadienyl)] Complexes: The Important First Steps

Cyclopentadienyl–ruthenium half‐sandwich complexes with η²‐bound alkyne ligands have been suggested as catalytic intermediates in the early stages of Ru‐catalyzed reactions with alkynes. We show that electronically unsaturated complexes of the formula [RuCl(Cp^)(η²‐RC≡CR′)] can be stabilized and crystallized by using the sterically demanding cyclopentadienyl ligand Cp^ (Cp^=η⁵‐1‐methoxy‐2,4‐tert‐butyl‐3‐neopentyl‐cyclopentadienyl). Furthermore we demonstrate that [RuCl₂(Cp^)]₂ is an active and regioselective catalyst for the [2+2+2] cyclotrimerization of alkynes. The first elementary steps of the reaction of mono(η²‐alkyne) complexes containing {RuCl(Cp*)} (Cp*=η⁵‐C₅Me₅) and {RuCl(Cp^)} fragments with alkynes were investigated by DFT calculations at the M06/6‐31G* level in combination with a continuum solvent model. Theoretical results are able to rationalize and complement the experimental findings. The presence of the sterically demanding Cp^ ligand increases the activation energy required for the formation of the corresponding di(η²‐alkyne) complexes, enhancing the initial regioselectivity, but avoiding the evolution of the system towards the expected cyclotrimerization product when bulky substituents are present. Theoretical results also show that the electronic structure and stability of a metallacyclic intermediate is strongly dependent on the nature of the substituents present in the alkyne.     

Experimental and theoretical studies of Si/P substituted orthorhombic Fe2P

A Mössbauer spectroscopic study of orthorhombic Fe₂P_1–x Si _x withx 0.35 was performed. A large spread in magnetic hyperfine fields was found at the six Fe positions ranging from 10–26 T at 4.2 K. Small rearrangements in the crystal positions as compared to the hexagonal phase cause large changes in the magnetic field. Large changes in Fe magnetic moments have also been obtained in a spin-polarized LMTO band calculation performed on orthorhombic Fe₂P as compared to a similar calculation of hexagonal Fe₂P.