Volume 78, Issue 10

It is well known that chemistry plays a key role in societal upliftment. The pursuit of improved quality of life for present and future generations provides the impetus to bring innovative chemistry to bear upon the creation and development of novel materials. Thus, it was deemed fitting and timely to launch a new initiative as the 1st International Symposium on Novel Materials and their Synthesis (NMS-1), which was held jointly with the 15th International Symposium on Fine Chemistry and Functional Polymers (FCFP-XV). This event was organized in Shanghai on 17-20 October 2005 by Fudan University to celebrate its Centennial Anniversary. The National Natural Science Foundation of China, Shanghai Key Laboratory of Molecular Catalysis and Innovative Materials, and the Shanghai Society of Chemistry and Chemical Industry provided valuable support. The Symposium was carried out under the auspices of IUPAC. The main objectives of the Symposium were to present state-of-the-art synthesis and preparation of novel materials, and to discuss their performance and applications potential. The breadth of these themes offered scope to disseminate novel ideas and findings within a multidisciplinary scientific community. At the same time, the event provided a forum for the exchange of updated knowledge and experience in the research and development communities, and with authorities and industry, as well as giving newcomers the opportunity to meet with international authorities in specialized fields. Finally, it was hoped that visitors would use the occasion to learn something about Fudan University, Shanghai, and China. The Symposium was attended by 188 delegates from 29 countries and areas. Among them, 117 were from overseas. The scientific program comprised 116 lectures and 35 posters, and was characterized by detailed and lively discussion of the four main themes: - innovative catalytic and other synthetic methods, including chiral and asymmetrical synthesis - innovative polymer materials, including conducting, semiconducting, opto-electronic, and biobased polymers, their properties, and characteristics - energy materials, including fuel cells, solar cells, lithium batteries, and supercapacitors - other novel materials, including drugs, perfumes, agricultural chemicals, electrical materials, photosensitive materials, displaying materials, and fine ceramics and their preparation The program served to emphasize that novel materials and their synthesis are dynamic research areas that are attracting growing interest from researchers, engineers, industries, and governments. Furthermore, novel materials continue to find applications that serve the needs and interests of consumers. A selection of eight papers based upon invited presentations to FCFP-15/NMS-1 is published in this issue, and demonstrates the quality and scope of the Symposium themes. During the Symposium, it was recognized that it would be highly desirable to provide an ongoingforum for scientific exchange in this important field, and it was recommended that it should be continuedand regularized. Future Symposia in this series will be hosted by Fudan University in Shanghai duringodd years, and will be held in other countries or regions during even years. Yuping Wu Conference Editor

In this article, we review the possibility of combining conjugated polymers with nanometer-scale devices (nanodevices), in order to introduce the properties associated with conjugated polymers into such nanodevices. This approach envisages combining the highly topical disciplines of polymer electronics and nanoelectronics to engender a new subdirection of polymer nanoelectronics, which can serve as a tool to probe the behavior of polymer molecules at the nanometer/molecular level, and contribute to clarifying transport mechanisms in conjugated polymers. In this study, we exemplify this combination, using a family of linear and conjugated polymers, poly( p -phenylene-ethynylene)s (PPEs) with thiolacetate-functionalized end groups.

The alternating copolymerization of carbon dioxide and epoxide to give polycarbonate has attracted the attention of many chemists, because it is one of the most promising methodologies for the utilization of carbon dioxide as a safe, clean, and abundant raw material in the synthetic chemistry. Recent developments of the catalysts for the alternating copolymerization are based on the rational design of metal complexes, especially complexes of transition metal with well-defined structures.

Fine holographic gratings were fabricated using siloxane- and mesogen-containing compounds. A grating with 40 % diffraction efficiency was formed with 10 wt % non-liquid-crystalline 4-methoxyphenyl 4-[4-(pentamethyldisiloxanyl)butoxy]benzoate and trimethylolpropane triacrylate. 4-Methoxyphenyl 4-[4-(1,1,3,3,5,5,5-heptamethyltrisiloxan-1-yl)butoxy]-benzoate gave 50 % diffraction efficiency and angular selectivity of 5°. Siloxane-containing liquid-crystalline compounds were also effective in fabricating fine gratings. These compounds induced distinct phase separation over a concentration range from 6 to 20 wt % in the formation of holographic gratings. The use of ring-opening polymerizable bifunctional epoxides as one of the reactive cross-linking matrix components, together with penta- or tetra-acrylate initiated by 3,3'-carbonylbis(7-diethylaminocoumarin)diphenyliodonium hexafluorophosphate, greatly improved the diffraction efficiency. Fine gratings with 70 and 78 % diffraction efficiency and angular selectivity of 5° were formed with 10 wt % 4-cyano-4'-[(5-heptamethyltrisiloxan-1-yl)pentyloxy]-biphenyl and 4-cyanophenyl 4-[(5-heptamethyltrisiloxan-1-yl)pentyloxy]benzoate using pentaerythritol pentaacrylate-neopentylglycol diglycidyl ether-tripropylene glycol diacrylate (4:5:1) as the polymer matrix component.

Cellulose is a biodegradable polymer produced sustainably in large quantities by nature. It has been used by mankind for centuries because of its favorable properties, but suffers disadvantages such as the high cost of production and limited processibility. For example, it cannot be melted and is only soluble in less common solvents. The latter limitation can be overcome through appropriate derivatization of cellulose, which increases the solubility range and may generate thermoplastic materials. This paper will review three new developments leading to enhanced utilization of cellulosics. Firstly, an overview is given of the progress in the formulation of fiber-reinforced thermoplastic cellulose composites to facilitate extrusion processing. Cellulose-polypropylene composites show enhanced properties in comparison with neat polypropylene, and offer scope for replacing composites containing glass fibers, owing to resultant advantages in weight, recyclability, and ease of disposal. Progress is also reported in improving the predictability of essential physical quantities and melt flow in cellulose esters. Finally, an account is given of the successful development of microcrystalline cellulose (CFM) derivatives, synthesized in a heterogeneous manner, as chiral recognition agents in liquid chromatography. The structural features of these materials are decisive for their use. A model is proposed for the morphology of the cellulosic fibrils.

Several aliphatic nitro compounds have been employed as stabilized carbanions in the conjugate addition to a variety of electron-poor alkenes (Michael reaction). Depending on the nature of the alkene, new carbon-carbon single or double bonds can be generated. However, all the Michael adducts can be efficiently utilized as key building blocks for the synthesis of a huge array of fine chemicals, including homo- and heterocyclic structures.

An intriguing umpolung of the reactivity of imines possessing electron-withdrawing groups was observed. For example, N-alkylation-coupling reaction of the imines derived from glyoxylates was conducted with dialkylaluminum chloride in acetonitrile to give N-monoalkylated 1,2-diamines in good yields. On treatment of various α-imino esters with organoaluminum reagents and allyltributyltin in the presence of benzoyl peroxide (BPO), the tandem reaction proceeded to give the N-alkylation/C-allylation products in good yields. Diethyl 2-[ N -( p -methoxyphenyl)imino]-malonate underwent amination reactions with alkyl Grignard reagents to give N-alkylation products in good yields. The obtained N-alkylation products were readily converted into N -alkyl- p -anisidines by the oxidative removal of the malonate moiety. In order to enhance the reactivity of imines, an iminium salt was prepared using the oxidation of amino ketene silyl acetal with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ), and the subsequent nucleophilic addition to this iminium species proceeded to afford α-amino esters in good yields.

The treatment of benzene solutions of the cations [Re(NO) 2 (PR 3 ) 2 ][BAr F 4 ] (R = Cy and R = i Pr; [BAr F 4 ] = tetrakis{3,5-bis(trifluoromethyl)phenyl}borate) with phenyldiazomethane afforded the moderately stable cationic rhenium(I) benzylidene dinitrosyl bis(trialkyl) phosphine complexes as [BAr F 4 ] - salts in good yields. The cationic rhenium dinitrosyl bisphosphine complexes catalyze the ring-opening metathesis polymerization (ROMP) of highly strained nonfunctionalized cyclic olefins to give polymers with relatively high polydispersity indices, high molecular weights, and Z configurations of the double bonds in the polymer chain backbones of over 80 %. The benzylidene derivatives are almost inactive in ROMP catalysis with norbornene and in olefin metathesis. NMR experiments gave first hints for the initial formation of carbene complexes when [Re(NO) 2 (PR 3 ) 2 ][BAr F 4 ] was treated with norbornene. The carbene formation is initiated by an unique reaction sequence where the cleavage of the strained olefinic bond starts with phosphine migration forming a cyclic ylid carbene complex. The [2+2] addition of a norbornene molecule to the Re=C bond leads to the rhenacyclobutane complex, which is expected to be converted into an iminate complex by attack of the ylid function onto one of the N NO atoms followed by Wittig-type phosphine oxide elimination. The formation of phosphine oxide was confirmed by NMR spectroscopy. This species is thought to drive the ROMP metathesis with alternating rhenacyclobutane formations and cycloreversions. The proposed mechanism is supported by density functional theory (DFT) calculations.

We report an effective method for the synthesis of a core-shell Si/C nanocomposite, and its application as anode material for lithium ion (Li-ion) batteries. Polyacrylonitrile (PAN)-coated Si nanoparticles are formed by emulsion polymerization, and this precursor is heat-treated under argon to generate a Si/C core-shell nanocomposite. The conductive carbon shell envelops the silicon nanoparticles and suppresses aggregation of the nanoparticles during cycling. Meanwhile, the carbon shell combines closely with the nanocores, and significantly enhances the kinetics of lithium intercalation and de-intercalation, as well as the apparent diffusion coefficient of Li-ions. Consequently, the core-shell Si/C nanocomposite exhibits better electrochemical performance than pure Si nanoparticles, indicating that this is a promising approach to improve cyclability and kinetics of nano-anode materials for Li-ion batteries.

Stereochemical configuration is determined by the relationship of atoms in three-dimensional space, yet remains most commonly represented in two-dimensional media such as printed publications or computer screens. Recommendations are provided for the display of three-dimensional stereochemical information in two-dimensional diagrams in ways that avoid ambiguity and are likely to be understood correctly by all viewers. Examples are provided for all types of stereochemical configuration, with explanation of which styles are preferred and which should be avoided. Principal recommendations include: Know your audience: Diagrams that have a wide audience should be drawn as simply as possible. Avoid ambiguous drawing styles. Avoid the use of perspective diagrams and class-specific drawing styles (Fischer projections, Haworth projections, etc.) when structures are to be interpreted by computers. Use solid wedges to indicate bonds that project above the plane of the paper and hashed wedges to indicate bonds that project below the plane of the paper; in both cases, the bonds must be oriented with the narrow end at the stereogenic center. Avoid connecting stereogenic centers with a stereobond.