Beta-functionalised polythiophenes as microelectrode modifiers in low conductive media

A study on polythiophene coated microelectrodes is reported, the goal being that of checking the capability of these electrochemical systems to work in low conductive media. The possibility of electrochemically p-doping the polymer in the presence of very low concentrations or even in the absence of supporting electrolyte in the solution is ascertained, opening the way to the use of similar systems in pure solvent media. This result is obtained in such conditions that the presence of residual charges--and corresponding counterions--trapped inside the film coating can be reasonably hypothesised.     

Formation of inclusion organoactinide complexes with boron-containing macrocycles

Reaction of the organoactinide complexes (C5Me5)2AnMe2 (An = Th, U) with catecholborane yields an inclusion complex where the actinide is encapsulated inside a 15-membered, hexaoxo, trianionic macrocycle built from alternating catechol and catecholborate fragments. In the presence of LiOH, a dimer of two encapsulated actinide macrocycles is formed. The X-ray molecular structure for all the complexes is presented.     

Solvent effects in the polymerization of propylene catalyzed by octahedral complexes

The effect of solvents (toluene, dichloromethane, and hexane) was studied on the polymerization of propylene with the octahedral complexes bis(trimethylsilyl)benzamidinate titanium dichloride(a), bis(acetylacetonate) titanium dichloride(b), and bis(diethylamino) titanium di‐2‐(diphenylphosphanylamino)pyridine as catalytic precursors and methylalumoxane as the cocatalyst. For comparison, the polymerization was also performed in plain liquid propylene without the addition of any solvent. The obtained polymers were fractionated by refluxing hexane. The activity of the complexes and the molecular weights and tacticities of the whole polymers and their different fractions were the studied parameters. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4505–4516, 2005     

Vibrational energy distribution of CO in the oxidation of C on Pt

CO, excited to its seventh vibrational level, is generated by C oxidation on Pt at 1000–1400 K. Analysis of its Fourier transform IR emission spectrum suggests a non-equilibrium, yet statistical, vibrational distribution. A long-lived reaction complex involving 2–3 Pt atoms is postulated.     

Design of organometallic group IV heteroallylic complexes and their catalytic properties for polymerizations and olefin centered transformations

The use of metallocenes in many stoichiometric and catalytic processes has been the impetus for the development of new organometallic complexes, especially those containing early transition metals. The formation of coordinative unsaturated complexes using allylic, benzamidinate and aminopyridine families is presented. The synthesis and structural parameters of the new complexes, their activation and use in the polymerization of alpha-olefins and dienes, in the dehydrogenative coupling of silanes and in the hydroamination reactions comprise the objectives of this review.     

Singer's Formant in Sopranos: Fact or Fiction?

Although it is generally agreed that the singer's formant (F_S) is a prerequisite for successful stage performance, the results of this research do not support its presence in the soprano voices of trained female singers. Results are based on a recent investigation testing 10 advanced/professional sopranos in two groups singing sustained vowels at three frequencies: high (932 Hz), mid (622 Hz), and low (261 Hz). Spectrographic analysis shows that the nature of harmonic energy varies in relation to pitch. A resonance band somewhat resembling the tenor F_S was usually evident in vowels sung at low and mid pitch. However, unlike the F_S of typically less than 1 kHz bandwidth associated with tenors, sopranos singing similar pitches produced corresponding bandwidths which were significantly broader, usually at least 2-kHz wide. Vowels sung by sopranos at high-pitch levels exhibited strong fundamental frequency production with strong reinforcement of adjacent harmonics extending to 5 kHz and beyond. This type of production in essence nullifies the necessity for a typical F_S. Absence of the F_S in strong soprano voices might also imply the adaptation of a sufficiently different overall vocal tract configuration, so that techniques geared to developing maximal projection should not be the same as those developed to maximize the F_S in other voices.     

Dehydrocoupling reactions of amines with silanes catalyzed by [(Et2N)3U][BPh4]

Dehydrocoupling reactions of primary amines RNH₂ with PhSiH₃ were catalyzed by [(Et₂N)₃U][BPh₄] to give the corresponding aminosilanes PhSiH_3−n(NHR)_n (n=1–3), the relative yields of the products were found to be dependent on the experimental conditions and on the nature of R. For a primary silane (PhSiH₃), the reactivity of RNH₂ follows the order primary>secondary>tertiary. Similar dehydrocoupling reactions using secondary amines with secondary silanes were found to be less reactive. Homodehydrocoupling of the silane was found not to be a competing reaction at room temperature. The hydride [(RNH)₂UH][BPh₄], which is plausibly formed in the reaction of [(RNH)₃U][BPh₄] with PhSiH₃ is a likely intermediate in the catalytic cycle.     

Octahedral Complexes in the Polymerization of α-Olefins

Summary : A series of dimethyl titanium benzamidinate complexes has been prepared containing various functional groups at the aromatic ring. These functional groups were selected to study their electronic or steric effects at the cationic metal center in the polymerization of propylene. Quantitative structure activity relationship (QSAR) studies showed that a linear relationship is observed only for the Taft Parameter (Es). Mono- and bis-benzamidinate complexes were found to produce similar polymers indicating that alike active species are obtained regardless of the starting complex. Deuterium labeled 2-D-propene showed that a new epimerization mechanism for this type of complexes is operative.