Spotlights on Recent JACS Publications

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Spotlights pubs.acs.org/JACS

Spotlights on Recent JACS Publications

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FROM SOLAR ENERGY TO ELECTRICITY: A DIFFERENT ROUTE Sunlight is a major renewable energy source with substantial benefits for Earth’s environment and economy. Most solar energy conversion technologies generate power through transport of energized electrons. Shane Ardo and colleagues take a different route and study underexplored solar energy conversion processes that generate power from light-driven ion transport instead of electron transport (DOI: 10.1021/jacs.7b00974). The authors modify Nafion, a widely used ion-exchange membrane, with photoacid dyes to sensitize the membranes and initiate proton transport. Spectroscopic measurements confirm covalent bond formation between the photoacid and the membrane. Under visible light illumination, the modified membrane exhibits photovoltaic action through transport of ions driven by a change in the strength of a protic bond in the photoacid dye. These results represent the first demonstration of photovoltaic action through light-driven ion transport in an ionexchange membrane and offer promise for this membrane to be used in solar cells or as a separate ionic photoelectrochemical device. Hui Jin, Ph.D.

A RARE DNA BASE LINKS UP WITH PROTEINS IN THE NUCLEUS The modified nucleobase 5-formylcytosine (5fc) has recently been found to exist stably for weeks in mammalian DNA. But what does it do? Chuanzheng Zhou and colleagues show that one of its roles may be to cross-link proteinswith potential influence on chromatin remodeling, transcription, and DNA methylation (DOI: 10.1021/jacs.7b05495). Previous work has shown that 5fc reacts with primary amines in proteins. To understand how this modified base may behave in the cell, Zhou and colleagues have to find a way to introduce it into nucleosome core particlesstrands of nuclear DNA tightly wound around histone proteins, which make up chromatin without interfering with the particles’ formation in situ. So they add a photolabile protecting group to block the modified base’s formyl group. Once they incorporate the protected base into a nucleosome core particle, they deprotect it with light and characterize its activity. They find that the base forms reversible cross-links with primary amines on histones. This study has potentially important implications for the fate and role of 5fc and may help to explain the existence of multiple modified nucleobases in genomic DNA. Deirdre Lockwood, Ph.D.

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SOLID-STATE NMR GETS UP CLOSE WITH CATALYSIS Preparing fuels, fabrics, fertilizers, pharmaceuticals, and other materials for day-to-day living is increasingly accomplished via catalytic processes, improving sustainability over conventional methods. To this end, scientists have designed highly efficient well-defined single-site heterogeneous catalysts whose structure−activity relationship must be elucidated. In this Perspective, Christophe Copéret and colleagues discuss recent advances in the application of solid-state nuclear magnetic resonance (NMR) spectroscopy to describe, in molecular detail, the structure and dynamics of the surface active sites in heterogeneous catalysts (DOI: 10.1021/jacs.6b12981). The authors detail how sensitivity-enhancing hyperpolarization methods combined with 2D NMR experiments can, in some cases, render high-resolution three-dimensional structures of active sites, which constitutes a paradigm shift for the field. However, due to the inherently small amount, complex environment, and dynamic nature of surface active sites, line broadening and low intensity continue to pose challenges that will need to be addressed by future research efforts. Other issues are that NMR experiments are mostly performed under conditions far from operating conditions and that current hyperpolarization methods are not universally compatible with catalysts; hence, alternative hyperpolarization methods will be necessary. The authors also discuss how the combination of NMR data with computational methods can help to understand the electronic structure of catalytic intermediates, paving the way for predicting the reactivity of heterogeneous catalysts. Erika Gebel Berg, Ph.D. © 2017 American Chemical Society

COMMON PRECURSORS YIELD UNCOMMON BIRADICAL STRUCTURES Birger Dittrich, Gernot Frenking, Wolfgang Kaim, Herbert Roesky, and colleagues report the synthesis and characterization of the first organosilicon biradicals containing H or CH3 groups in the vicinity of the radical center (DOI: 10.1021/ jacs.7b06610). Radicals, which contain at least one unpaired electron, are the reactive intermediates of many chemical and biological processes. Biradicals contain an even number of electrons, yet they present two free radical centers that act independently of each other. Biradicals have long been an interesting topic in inorganic chemistry due to the high reactivity and exciting physical properties of the species. To synthesize biradicals that are stable at room temperature, scientists typically use bulky substituents on the central atoms. It is a challenging task to create stable biradicals that comprise of small substituent groups, such as H or CH3 groups. The team reports on the one-step synthesis of three biradicals with Si−H and Si−CH3 bonds, using commodity carbene group precursors. Characterization with X-ray crystallography, EPR spectroscopy, and theoretical calculations shows that all three compounds created are stable in the solid state at room temperature for at least 6 months under inert conditions. The work opens up a new direction in biradical synthesis. Christine Herman, Ph.D.

Published: August 30, 2017 11629

DOI: 10.1021/jacs.7b08780 J. Am. Chem. Soc. 2017, 139, 11629−11629