Volume 85, Issue 5

IUPAC’s vision statement declares that the Union advances the worldwide role of chemistry for the benefit of Mankind. And one of its long-range goals states “IUPAC will utilize its global perspective and network to contribute to the enhancement of chemistry education, the career development of young chemical scientists, and the public appreciation of chemistry”. In pursuit of this spirit, the Union established in 2000 the IUPAC Prize for Young Chemists and has been honoring since then outstanding young research chemists at the beginning of their careers by making annual awards. The prizes are given for the most outstanding Ph.D. theses in the area of the chemical sciences, as described in 1000-word essays. As immediate Past President of IUPAC, I was honored to chair the prize selection committee of eminent chemists, who enjoyed reading essays of 41 applicants from 22 countries. After critical evaluation of the originality and excellence of the essays and research results, the committee decided unanimously to award 2012 Prizes for the following six essays: - “Study of the factors affecting the selectivity of catalytic ethylene oligomerization”, Khalid Albahily , University of Ottawa, Ottawa, Canada (following earlier studies at King Saud University, Saudi Arabia and Texas A&M University, College Station, TX, USA) - “Nanowire nanoelectronics: Building interfaces with tissue and cells at the natural scale of biology”, Tzahi Cohen-Karni , Harvard University, Cambridge, MA, USA (following earlier studies at Technion Israel Institute of Technology and Weizmann Institute of Science, Israel) - “Synthetic investigations featuring boron-rich and multidentate chalcoether-containing ligands”, Alexander Spokoyny , Northwestern University, Chicago, IL, USA (following earlier studies at University of California, Los Angeles, CA, USA) - “Quantification of virtual chemical properties: Strain, hyperconjugation, conjugation, and aromaticity”, Judy I-Chia Wu , University of Georgia, Athens, GA, USA (following earlier studies at Tung-Hai University, Taiwan) - “New materials for intermediate-temperature solid oxide fuel cells to be powered by carbon- and sulfur-containing fuels”, Lei Yang , Georgia Institute of Technology, Atlanta, GA, USA (following earlier studies at Beihang University and Tsinghua University, China) - “Transition metal catalysis: Activation of CO 2 , C–H, and C–O bonds en route to carboxylic acids, biaryls, and N-containing heterocycles”, Charles Yeung , University of Toronto, Toronto, Canada (following earlier studies at University of British Columbia, Vancouver, Canada) All the awardees were invited to present posters on their research at the 44th IUPAC World Chemistry Congress, Istanbul, Turkey, 11–16 August 2012. Upon IUPAC’s invitation, 4 of the 6 winners offered review papers on their research topics for consideration as publications in this issue of Pure and Applied Chemistry . Finally, it is an honor and a pleasure to congratulate each of the winners and their supervisors for winning the 2012 IUPAC Prize for Young Chemists. It is hoped that each of them will continue to contribute to a bright future for chemical sciences and technologies and to take active roles in IUPAC bodies in the future. Nicole Moreau IUPAC Immediate Past President and Chair of the IUPAC Prize Selection Committee

The interface between nanoscale electronic devices and biological systems enables interactions at length scales natural to biology, and thus should maximize communication between these two diverse yet complementary systems. Moreover, nanostructures and nanostructured substrates show enhanced coupling to artificial membranes, cells, and tissue. Such nano–bio interfaces offer better sensitivity and spatial resolution as compared to conventional planar structures. In this work, we will report the electrical properties of silicon nanowires (SiNWs) interfaced with embryonic chicken hearts and cultured cardiomyocytes. We developed a scheme that allowed us to manipulate the nanoelectronic to tissue/cell interfaces while monitoring their electrical activity. In addition, by utilizing the bottom-up approach, we extended our work to the subcellular regime, and interfaced cells with the smallest reported device ever and thus exceeded the spatial and temporal resolution limits of other electrical recording techniques. The exceptional synthetic control and flexible assembly of nanowires (NWs) provides powerful tools for fundamental studies and applications in life science, and opens up the potential of merging active transistors with cells such that the distinction between nonliving and living systems is blurred.

200 years of research with carbon-rich molecules have shaped the development of modern chemistry. Research pertaining to the chemistry of boron-rich species has historically trailed behind its more distinguished neighbor (carbon) in the periodic table. Notably, a potentially rich and, in many cases, unmatched field of coordination chemistry using boron-rich clusters remains fundamentally underdeveloped. Our work has been devoted to examining several basic concepts related to the functionalization of icosahedral boron-rich clusters and their use as ligands, aimed at designing fundamentally new hybrid molecular motifs and materials. Particularly interesting are icosahedral carboranes, which can be regarded as 3D analogs of benzene. These species comprise a class of boron-rich clusters that were discovered in the 1950s during the “space race” while researchers were developing energetic materials for rocket fuels. Ultimately, the unique chemical and physical properties of carborane species, such as rigidity, indefinite stability to air and moisture, and 3D aromaticity, may allow one to access a set of properties not normally available in carbon-based chemistry. While technically these species are considered as inorganic clusters, the chemical properties they possess make these boron-rich species suitable for replacing and/or altering structural and functional features of the organic and organometallic molecules—a phenomenon best described as “organomimetic”. Aside from purely fundamental features associated with the organomimetic chemistry of icosahedral carboranes, their use can also provide new avenues in the development of systems relevant to solving current problems associated with energy production, storage, and conversion.

This article emphasizes two underappreciated aspects of hyperconjugation in hydrocarbons, two-way hyperconjugation and hyperconjugation in tight spaces. Nonplanar polyenes [e.g., cyclooctatetraene ( D 2 d ), biphenyl ( D 2 ), styrene ( C 1 )], the nonplanar rotational transition states (TSs) of planar polyenes (e.g., perpendicular 1,3-butadiene), as well as the larger nonplanar Hückel or Möbius annulenes, are stabilized by effective σ-electron delocalization (involving either the C–C or C–H bonds) via two-way hyperconjugation . The collective consequence of two-way hyperconjugation in molecules can be nearly as stabilizing as π-conjugation effects in planar polyenes. Reexamination of the σ- vs. π-bond strength of ethylene results in surprising counterintuitive insights. Strained rings and cages (e.g., cyclopropane and tetrahedrane derivatives, the cubyl cation, etc.) can foster unexpectedly large hyperconjugation stabilizations due to their highly deformed ring angles. The thermochemical stabilities of these species rely on a fine balance between their opposing destabilizing geometrical features and stabilizing hyperconjugative effects in tight spaces (adjustable via substituent effects). We hope to help dispel chemists’ prejudice in viewing hyperconjugation as merely a “mild” effect with unimportant consequences for interpreting the structures and energies of molecules.

Traditional organic synthesis is driven by the need for functional molecules. The development of green chemical methods, however, is an increasingly important challenge in the context of global sustainability. To this end, the direct use of abundant carbon feedstocks in synthesis (such as CO, CO 2 , methanol, arenes, alkanes, α-olefins, and biological raw materials) aims to minimize waste production and increase efficiency.

The chemical diversity of natural antioxidants (AOXs) makes it difficult to separate, detect, and quantify individual antioxidants from a complex food/biological matrix. Moreover, the total antioxidant power is often more meaningful to evaluate health beneficial effects because of the cooperative action of individual antioxidant species. Currently, there is no single antioxidant assay for food labeling because of the lack of standard quantification methods. Antioxidant assays may be broadly classified as the electron transfer (ET)- and hydrogen atom transfer (HAT)-based assays. The results obtained are hardly comparable because of the different mechanisms, redox potentials, pH and solvent dependencies, etc. of various assays. This project will aid the identification and quantification of properties and mutual effects of antioxidants, bring a more rational basis to the classification of antioxidant assays with their constraints and challenges, and make the results more comparable and understandable. In this regard, the task group members convey their own experiences in various methods of antioxidants measurement.

We present an overview on the applicability of fluorescence correlation spectroscopy (FCS) for the accurate determination of translational diffusion coefficients and thus, via the Stokes–Einstein relation, of molecular size. We consider several of the most common sources of optical aberrations and their impact on the outcome of conventional FCS measurements. We describe also a new variant of FCS, dual-focus FCS, which is robust against most of the considered aberrations, and we report reference values of diffusion coefficients for several fluorescent dyes across the visible spectrum.

The document gives definitions of terms met in the conventional thermal and thermomechanical characterisation of polymeric materials.

The biennial review of atomic-weight determinations and other cognate data has resulted in changes for the standard atomic weights of five elements. The atomic weight of bromine has changed from 79.904(1) to the interval [79.901, 79.907], germanium from 72.63(1) to 72.630(8), indium from 114.818(3) to 114.818(1), magnesium from 24.3050(6) to the interval [24.304, 24.307], and mercury from 200.59(2) to 200.592(3). For bromine and magnesium, assignment of intervals for the new standard atomic weights reflects the common occurrence of variations in the atomic weights of those elements in normal terrestrial materials.