Infrared Spectra of the Square Planar Rhodium(I) Complexes cis-[Rh(CO)2(pyridine) (X)] (X = Cl,Br): Isotopic Labelling Studies and Normal Coordinate Analysis

Abstract

The infrared spectra (4000 - 50 cm^?1) of the square planar rhodium(I) complexes cis-[Rh(CO)₂ (pyridine) (X)] (X = Cl, Br) and their isotopomers with pyridine-d ₅ and ¹³CO have been determined. Assignments are based on earlier studies on pyridine and its complexes and on the shifts in infrared bands which are caused by the isotopic substitutions employed. Normal coordinate analysis following the procedure of Becher and Mattes has been used to confirm the empirical assignments. The two v(RhC) bands are observed near 490 and 450 cm^?1. v(RhN) is found near 210 cm^?1 and v(RhX) occurs at 310 (X = Cl) and 235 (X = Br) cm^?1. At frequencies below 200 cm^?1, the bands are assigned to bending modes in the following sequence: δ (RhN) > δ (CRhC) > δ (RhCl) > γ (RhCl) > γ (RhN).     

Comment: Electron-transfer reactions in the 9-mesityl-10-methylacridinium ion: impurities, triplet states and infinitely long-lived charge-shift states?

The likelihood of an infinitely long-lived, charge-shift state being formed by the target compound is re-assessed in light of persistent claims that such chemistry is both viable and observable.     

Multirate methods for the transient analysis of electrical circuits

Multirate integration is an important tool to increase the speed of the transient analysis of circuits. This paper shows an approach for the “Compound-Fast” multirate algorithm how to control the errors at the coarse and the refined time-grid by means of the independent stepsizes of these grids. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

The synthesis of 3-hydroxymethyldibenzo[b,f]thiepin 5,5-dioxide,a prostaglandin antagonist

An economic synthesis of 3-hydroxymethyldibenzo[b,f]thiepin 5,5-dioxide, a novel prostaglandin antagonist, is described. The key step in the synthesis is the formation of a carboxyphenylacetic acid by carboxylation of a toluic acid dianion, followed by cyclisation to the tricyclic ketone. Readily available starting materials are used in the synthesis and conditions have been found at each stage to give pure intermediates, requiring little purification, in high yield.     

Solid-phase microextraction: Artefact formation and its avoidance

Summary The application of solid-phase microextraction (SPME) for the flavour analysis of strawberry and apple fruits has been studied. An SPME liquid sampling method based on poly(acrylate)-coated fibers was developed. Immediate thermal desorption of the adsorbed compounds led to the formation of Maillard products due to the high concentration of carbohydrates and amines in the samples, remaining on the surface of the fiber. Artefact formation was significantly reduced by rinsing the fiber with water prior to thermal desorption.     

Detection of nanoscale events in dispersed polymer particles containing a charge-transfer fluorescence probe

A probe molecule, which shows an unusually large change in fluorescent properties in response to changes in its environment, was introduced into a monodisperse polystyrene latex. Upon addition of low-molecular-weight compounds, the ensuing swelling process of the latex could be followed via the changes in the fluorescence spectrum of the probe molecule. Polymerization reactions of monomers, introduced into the particles, could also be monitored by means of this approach. Using glycidylmethacrylate as the monomer led to the formation of particles in which two distinctly different surroundings could be detected after such a polymerization. © 1995 John Wiley & Sons, Inc.     

The photoelectron spectra of 4-methylene thiacyclohexane derivatives through-bond interaction

The photoelectron spectra of 4-methylene thiacyclohexane, 4-difluo romethylene thiacyclohexane and trans-2-methylene-6-thiaperhydronaphthalene are described and compared with thiacyclohexabne, difluoromethylene-cyclo hexane and cis-2-methylene-6-thiaperhydronaphthalene.A through bond interaction between the sulphur lone pair and the vinyl-π-system is observed. The results are discussed in relation with the sigma-coupled transition observed in the electronic absorption spectra of the dicyano methylene derivatives by P. Pasman.