Volume 81, Issue 1

IUPAC is a global, scientific organization that contributes to the worldwide understanding of chemistry and the chemical sciences. It is certainly true that young chemists are shaping our science, and it is important for IUPAC to provide encouragement to our young colleagues. IUPAC accomplishes this goal through the IUPAC Prize for Young Chemists. This prestigious annual prize honors four to five chemists for important and outstanding research carried out during recent Ph.D. studies. The work is mainly judged on the basis of a 1000-word essay which is supported by recommendations from the senior scientist(s) with whom the candidate collaborated. As immediate Past President of IUPAC, I have had the pleasure of chairing an international prize selection committee of eminent chemists with a wide range of expertise in chemistry that adjudicated essays from 42 applicants from 16 countries. Reading these outstanding essays provided a wonderful overview of new trends in chemistry. Due to the large number of excellent candidates, it was not an easy task to pick the winners, but in the end the committee arrived at a unanimous decision and awarded the 2008 IUPAC Prize for Young Chemists to the following five chemists: - Emilie V. Banide , University College Dublin, Dublin, Ireland, with a thesis entitled "From allenes to tetracenes: Syntheses, structures and reactivity of the intermediates" - Christopher Thomas Rodgers , University of Oxford, UK, with a thesis entitled "Magnetic field effects in chemical systems" - Akinori Saeki , Osaka University, Osaka, Japan, with a thesis entitled "Nanometer-scale dynamics of charges generated by radiations in condensed matter" - Andrea Rae Tao , University of California, Berkeley, CA, USA, with a thesis entitled "Nanocrystal assembly for bottom-up plasmonic materials" - Scott Warren , Cornell University, Ithaca, NY, USA, with a thesis entitled "Nanoparticle-block copolymer self-assembly" Each winner received a cash prize of USD 1000 and a trip to the 42nd IUPAC World Chemistry Congress, which will take place in Glascow, Scotland, 2-7 August, 2009. Here the winners will have the opportunity to present their work, which is an important stage of any research project. To reach an even wider audience, the prize winners were invited to submit manuscripts on aspects of their research for publication in Pure and Applied Chemistry ( PAC ). It is a pleasure to see that all five prize winners have taken advantage of this offer. The result is the five refereed papers which contain critical reviews of high quality and appear in this issue of PAC . Finally, it is an honor and a pleasure to congratulate each of the winners (and their supervisors) for winning the 2008 IUPAC Prize. It is IUPAC's hope that each of them has been encouraged to continue to do exciting research that will contribute to a bright future for the molecular-based sciences, which are so important for our common future. Bryan R. Henry IUPAC Immediate Past President and Chairman of the IUPAC Prize Selection Committee

Each step of the conversion of a series of 9-alkynyl-9 H -fluorenes into the corresponding fluorenylidene-allenes that dimerize and proceed sequentially via head-to-tail and tail-to-tail dialkylidene-cyclobutanes, en route to electroluminescent tetracenes, has been characterized X-ray crystallographically. Allenes possessing substituents of very different electronic and steric character, such as aryl, halogeno, silyl, phosphino, and ferrocenyl, exhibit novel and unexpected reactivity patterns. The silyl-allenes dimerize to yield 1,2-bis(fluorenylidene)cyclobutanes of intrinsic C 2 symmetry as a result of the overlapping fluorenylidenes with their large wingspans. Thermal rearrangement of a bis(fluorenyl)-bis(trimethylsilyl)-diallene generates the tetrabenzo- quater cyclopentadiene, C 60 H 36 , which represents 60 % of the C 60 framework. An attempt to isolate a "push-pull" allene, whose central carbon possesses carbene character, was made by incorporating a cation-stabilizing substituent (ferrocenyl) and an aromatic anionic moiety (fluorenide) at the termini. However, the allene underwent facile dimerization to the very heavily congested 3,4-di(spirofluorenyl)-1,2-bis(ferrocenyl-chloromethylene)cyclobutane that exhibits a very long (1.65 Å) C(3)-C(4) bond. Extension of this chemistry to dibenzosuberenylidene-allenes led to a straightforward route to the hitherto difficultly available dibenz[ c,d,h ]azulene system. Moreover, the reaction of 5-phenylethynyl-5 H -dibenzo[ a,d ]cyclohepten-5-ol with dicobalt octacarbonyl yielded, surprisingly, the first isolated example of a (μ-alkyne)Co 2 (CO) 5 (η 2 -alkene)complex, the long-sought first intermediate in the proposed mechanism of the Pauson-Khand reaction (PKR).

Chemical reactions that involve radical intermediates can be influenced by magnetic fields, which act to alter their rate, yield, or product distribution. These effects have been studied extensively in liquids, solids, and constrained media such as micelles. They may be interpreted using the radical pair mechanism (RPM). Such effects are central to the field of spin chemistry of which there have been several detailed and extensive reviews. This review instead presents an introductory account of the field of spin chemistry, suitable for use by graduate students or researchers who are new to the area. It proceeds by giving a brief historical overview of the development of spin chemistry, before introducing the essential theory. This is then illustrated by application to a series of recent developments in solution-phase magnetic field effects (MFEs). The closing pages of this review describe the role played by spin chemistry in the remarkable magnetic compass sense of birds and other animals.

The dynamics of short-lived charges generated by pulsed radiations such as electron beam (EB) and photon was investigated to elucidate their reactivity, electronic properties, and spatial behavior on a nanometer scale. Chemical reactions of radical cations (hole) and anions (electron) in condensed matter (organic liquids, polymers, and conjugated materials) occupy an important place in postoptical nanolithography and organic electric devices. The spatiotemporal evolution of charges during geminate ion recombination was measured by a highly improved picosecond (ps) pulse radiolysis and incorporated into a Monte Carlo simulation to clarify the key role of the charges in the formation of latent image roughness of chemically amplified resists (CARs). The dynamics and alternating-current (AC) mobility of transient charge carriers in conjugated materials such as polymer and organic crystals were studied by the combination of microwave conductivity and optical spectroscopies, revealing the potential plausibility for high-performance electric devices. Anisotropy measurement and methodology to resolve the sum of mobility into hole and electron components without electrodes have also been demonstrated.

Plasmonic materials are emerging as key platforms for applications that rely on the manipulation of light at small length scales. Sub-wavelength metallic features support surface plasmons that can induce huge local electromagnetic fields at the metal surface, facilitating a host of extraordinary optical phenomena. Ag nanocrystals (NCs) and nanowires (NWs) are ideal building blocks for the bottom-up fabrication of plasmonic materials for photonics, spectroscopy, and chemical sensing. Faceted Ag nanostructures are synthesized using a colloidal approach to regulate nucleation and crystallographic growth direction. Next, new methods of nanoscale organization using Langmuir-Blodgett (LB) compression are presented where one- and two-dimensional assemblies can be constructed with impressive alignment over large areas. Using this method, plasmon coupling between Ag nanostructures can be controlled by varying spacing and density, achieving for the first time a completely tunable plasmon response in the visible wavelengths. Lastly, these assemblies are demonstrated as exceptional substrates for surface-enhanced Raman spectroscopy (SERS) by achieving high chemical sensitivity and specificity, exhibiting their utility as portable field sensors, and integrating them into multiplexed "lab-on-a-chip" devices.

Control over the structure of metals at the mesoscale (2-50 nm) is crucial for emerging applications such as energy conversion, sensing, and information processing. The self-assembly of nanoparticles with block copolymers provides a natural entry point to materials of this length scale. The field's historical development, relevant physical models, and recent results are presented.

CHEMRAWN XII was the first of the CHEMRAWN series of conferences to be held in Southern Africa. CHEMRAWN ( chem ical r esearch a pplied to w orld n eeds) is a standing committee of IUPAC and has over the years organized a number of important conferences focusing on specific issues of global interests. These conferences often bring together scientists, government leaders and policy makers to address major global issues which could be resolved via chemistry. CHEMRAWN XII took place at Stellenbosch University, South Africa over the period 2-5 December 2007. Delegates came from all over Africa as well as from other parts of the developed and developing world. The conference was organized along the following broad themes: - adequate, safe, and affordable food for Africa - African agriculture in a global context: chemistry as the enabler - securing and sustaining water and soil quality for agricultural production - technologies to reduce post-harvest food loss - the role of agriculture in building a sustainable energy base - the role of chemicals in sustainable agriculture - the safe development and application of biotechnology in agricultural production - value-added and niche chemicals from agricultural produce This issue of Pure and Applied Chemistry ( PAC ) contains some of the papers presented at CHEMRAWNXII. The topics of these papers encompass many of the major themes of the conference andreflect the varied contributions of speakers from a range of countries. It is heartening to see papers fromresearchers based at institutions in developing countries. I would like to thank all those colleagues whomade the effort to submit full manuscripts arising from their lectures at the conference. Selwyn Mapolie Conference Editor

Plants respond to insect attack by releasing complex blends of phytogenic volatile organic compounds. Selection of a host plant by the leafminer Liriomyza huidobrensis is influenced by such volatile chemicals (allelochemicals) released by the host plant. In the case of potato plants, the allelochemicals identified are mainly volatile monoterpenes and sesquiterpenes. A potato plant that is already infested by other individuals of the same species of insects shows a quantitative difference in emission of such allelochemicals, which in turn plays an important role in the host preference behavior exhibited by the insect. Olfactometer tests (using whole, potted potato plants as well as excised leaves) showed that L. huidobrensis adults were more attracted to already infested plants for feeding and egg-laying than they were to uninfested plants, demonstrating that volatile chemicals from infested plants function as kairomones in this insect-plant relationship. However, when the potato plants were grown in soil treated with aqueous neem extract, this relationship was disturbed and the insects did not exhibit any consistent feeding or egg-laying response to neem-treated infested or uninfested host plants. This indicates that neem compounds disturb secondary metabolite production in the potato plant, which in turn has an influence on insects that use volatile plant allelochemicals as cues for host identification and location. Results of this study can help in a better understanding of neem as an environment-friendly botanical pesticide for use in sustainable agriculture.

This paper describes the isolation and physicochemical characterization of starch obtained from Parkia biglobosa (African locust bean). The results show that the properties of starch from this source compare favorably with those of corn starch BP, and suggest that it could be useful as a stabilizer in baking powders and as an emulsifier in the food industry.

The Diels-Alder adducts of ethyl ( E )-3-nitroacrylate and furan provided a common and versatile template for the stereocontrolled synthesis of an isomer of the natural product oryzoxymycin and polyhydroxylated cyclohexyl β-amino acid derivatives. The strategy for the synthesis of the polyhydroxylated cyclic β-amino acid derivatives involved base-induced fragmentation of the oxanorbornene skeleton and face selective oxidation reactions. A Pd-catalyzed transfer hydrogenation reaction in the presence of organic acids is also described. This reaction is amenable to being enantioselective through use of optical pure chiral organic acids.

The authors have proposed their own newly developed universal procedure for assessing waste and selecting methods of processing the waste for agricultural purposes. Increasingly more rigorous environmental legal regulations, especially pertaining to sustainability in agricultural and chemical production, were the most convincing motivation for such approach. The procedure is based on technological and environmental safety criteria. Special attention is devoted to the chemical processing of hazardous wastes into fertilizer products and the underlying reasons for such methodology. As opposed to physical and biochemical processes, in chemical processes the agents used completely change the chemical structure of the waste materials or at least that of some of their components. As a result, new phases are formed and the harmful properties of the initial material are eliminated. Prospects for the chemical processing of hazardous wastes are demonstrated using as an example the utilization of asbestos wastes. There are vast amounts of asbestos materials installed in industrial, communal, and service facilities. Landfill asbestos waste disposal is the common practice, but this does not solve properly the problem of environmental hazard. The proposed utilization concept consists in destroying asbestos with a phosphoric acid solution in a two-stage process. The obtained suspension is then filtered, and the solution of phosphates containing an excess of phosphoric acid is subsequently neutralized with lime and processed into phosphate fertilizers of TSP (triple superphosphate) or DCP (dicalcium phosphate) type. Experiments showed that the process yielded asbestos-free products which did not contain any respirable fibers. Comparative immunological tests showed that the products did not cause any degeneration of human lung cells exposed to them, as opposed to the original asbestos, which had a highly damaging effect on the cells.

This study presents a simple, sensitive, rapid, and low-cost amperometric method for direct and quantitative determination of glyphosate and glufosinate herbicides. Electrochemical synthesis and characterization of poly(2,5-dimethoxyaniline)-poly(4-styrenesulfonic acid) (PDMA-PSS) nanoparticles was achieved by cyclic voltammetry (CV) and scanning electron microscopy (SEM). The nanobiosensor was constructed by immobilizing the enzyme horseradish peroxidase (HRP) electrostatically onto the surface of a rotating gold disk electrode modified with PDMA-PSS nanoparticles. The biosensing principle was based on determination of the sensor response to glyphosate and glufosinate by amperometric methods. Hydrogen peroxide (H 2 O 2 ) was used to measure activity of the enzyme before injection of the herbicides into the electrolyte solution. The enzyme electrode was stable for a long period of time and was used for over 60 measurements. Glyphosate and glufosinate analyses were realized on spiked corn samples within a concentration range of 2.0-78.0 μg L -1 , corroborating that the nanobiosensor is sensitive enough to detect herbicides in these matrices. Based on a 20-μL sample injection volume, the detection limits were 0.1 μg L -1 (10 -10 M) for both glyphosate and glufosinate without sample clean-up or preconcentration.

The aim of this work was to determine the basis of resistance in a sub-Saharan sweetpotato variety, New Kawogo, to the African sweetpotato weevil Cylas puncticollis. This insect feeds on the roots, reducing quality and yield, and is the most important production constraint of sweetpotato in Africa. Laboratory bioassays were designed to determine how the performance of weevils differed on susceptible and resistant roots. Subsequently, liquid chromatography-mass spectrometry (LC-MS) analysis of the root surface and root latex identified quantitative and qualitative differences in the chemical profiles with higher levels of octadecyl and hexadecyl esters of hydroxycinnamic acids reported in the resistant variety. The compounds were synthesized to confirm their identity and incorporated into artificial diets for bioassays on C. puncticollis. High levels of mortality and developmental inhibition were recorded for larvae feeding on treated diets, and the effect was dose-dependent. Thus, in contrast to previous work on resistant African sweetpotato cultivars, resistance in New Kawogo is not only active, but is quantifiable and manageable for breeding. Work is underway to determine what effect these compounds have on the weevils at a molecular level. The inheritance of the root latex esters will be studied in new crosses and mapped in new populations using quantitative trait loci (QTLs) that are currently being developed.

Various chemical species of mercury differ considerably with regard to their route of absorption and their distribution in the body, yet many of them and their metabolites exhibit high-affinity binding to sulfanyl groups of proteins. Among all metals, mercury appears to have the most diverse effects on the immune system. Depending on the animal species and experimental conditions, mercury compounds may cause immunosuppression or immunostimulation, autoimmune reactions, or hypersensitivity. Mercury-sensitive strains of rats and mice are often used as model organisms to study the time course and events in autoimmunity. Within about 14 days after onset of oral mercury(II) exposure, levels of immunoglobulins E and G (IgE and IgG) increase, including autoantibodies to biomolecules such as laminin and fibrillarin. Antigen-antibody complexes are formed and are the cause of subsequent autoimmune diseases of blood vessels and organs. Mercury may induce local mercury hypersensitivity in humans, but the evidence for a role of mercury in autoimmune disease of humans is at best weak. Models for the immune effects of mercury are presented on the basis of current knowledge.