Mössbauer spectroscopic studies on mixed-valence states in trinuclear iron carboxylates

Mixed-valence states of iron atoms in newly synthesized mixed-valence trinuclear iron carboxylate complexes with -bonding ligands, such as acrylate, diphenylacetate, 1-naphthylacetate, and cyclohexylacetate which has no -bonding, were studied by means of Mössbauer spectroscopy. The cyclohexylacetate complex shows a temperature-dependent valence delocalization, while the 1-naphthylacetate complex shows temperature-independent mixed-valence states. The acrylate and diphenylacetate complexes show temperature-dependent mixed-valence states, although they do not reach an averaged-valence state at room temperature.     

Selective vinyl cationic polymerization of monomers with two cationically polymerizable groups. IV. New initiating systems for selective and living polymerization of p-isopropenylphenyl glycidyl ether

A variety of cationic initiators were employed for p-isopropenylphenyl glycidyl ether (IPGE), an α-methylstyrene derivative with an epoxy pendant, and optimum initiators and reaction conditions were evaluated in terms of its selective vinyl polymerization and living polymerization. Despite the coexistence of two cationically polymerizable groups in IPGE, binary initiating systems (HI, CF₃COOH, or CH₃CH(OiBu)-OCOCH₃, each coupled with ZnI₂) and sulfonic acids (CF₃SO₃H and CH₃SO₃H) selectively polymerized the vinyl group of IPGE in CH₂Cl₂ at ?78°C to produce soluble polymers with epoxy pendant groups in high yield. Metal halides (BF₃OEt₂ and AlEtCl₂) polymerized both the vinyl and epoxy groups of IPGE to give crosslinked insoluble polymers. In contrast, under these conditions, the HI/ZnI₂ system also led to a long-lived polymer, the molecular weight of which increased upon addition of a fresh feed of monomer to a completely polymerized reaction mixture, whereas the use of other initiators resulted in nonliving polymers. At higher temperatures (?40 and ?15°C), soluble poly(IPGE) was also obtained with HI/ZnI₂, but the polymer yield decreased with raising temperature, because of the occurrence of termination reaction.     

Structure of carbon onions and nanotubes formed by arc in liquids

Since carbon nanotubes and onions were discovered, many methods have been proposed for their production. For applications the main requirements are low capital cost, high purity of the produced material, simplicity of technique, and its potential for scale up. Recently a cathodic arc between two graphitic electrodes immersed in liquids has been demonstrated to be a simple method to produce carbon nanoparticles such as nanotubes and onions. In this paper high-resolution transmission electron microscopy is employed to examine the shape of the nanoparticles and the purity of the final material produced under various conditions. In this study we have used an arc discharge in two different liquids--liquid nitrogen and distilled water--and we have changed the grade of the carbon electrodes. The variety in structure, shape, and size of the produced particles is discussed in line with a model proposed to describe the physical process.     

Fluorometric assay of nicotinamide methyltransferase with a new substrate, 4-methylnicotinamide

A fluorometric method for the assay of nicotinamide methyltransferase has been established using rat liver 9000 x g supernatant fluid as a model enzyme preparation. 1,4-Dimethylnicotinamide formed enzymatically from a new substrate, 4-methylnicotinamide, is quantified by means of its fluorescence reaction with 4-methoxybenzaldehyde in aqueous alkali. The lower limit of determination of 1,4-dimethylnicotinamide is 100 pmol in the enzymatic reaction mixture. The apparent Km values for 4-methylnicotinamide and for nicotinamide, which is a known substrate for this enzyme, were 0.19 and 0.13 mM, respectively, whereas the relative activity of 4-methylnicotinamide as a methyl acceptor was about 1.5 times the value of nicotinamide.     

Crystal and molecular structure of lycorine-chlorohydrin: Revision of the stereochemistry

Action of POCl₃ and HCl on 1-O-acetyllycorine gave, quantitatively, O-acetyllycorine-chlorodhydrin, which was convertible, in good yield, to lycorene-α-oxide and so-called lycorine-cis-chlorohydrin. The configuration of the latter compound was revised establishing as trans by a single crystal X-ray analysis.