Catálogo de publicaciones - revistas

<jats:title>Opening one ring to tack on another</jats:title> <jats:p> Curious chemists have long sought to learn just how tightly carbon atoms can be bound together. For instance, it's possible to form a bond between two opposite corners of an already strained four-membered ring to make an edge-sharing pair of triangles. Gianatassio <jats:italic>et al.</jats:italic> have now devised a general use for these and related molecular curiosities. They show that appropriately modified nitrogen centers can pop open the most highly strained bond, leaving the more modestly strained ring motif intact. In this way, small rings can emerge as a convenient diversifying element in compounds, including new pharmaceutical candidates. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6270" page="241" related-article-type="in-this-issue" vol="351" xlink:href="10.1126/science.aad6252">241</jats:related-article> </jats:p>

<jats:title>Tunable lasers</jats:title> <jats:p> Lasers emit coherent light at wavelengths that are well defined. These wavelengths are usually fixed once the device has been fabricated. Now, Chakraborty <jats:italic>et al.</jats:italic> have combined an atomically thin graphene sheet with terahertz quantum cascade lasers to realize a terahertz laser that can be tuned via the carrier doping level of the graphene layer (see the Perspective by Polini). The demonstration opens up the possibility of reversible control over the laser emission through the integration of graphene waveguides. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6270" page="246" related-article-type="in-this-issue" vol="351" xlink:href="10.1126/science.aad2930">246</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6270" page="229" related-article-type="in-this-issue" vol="351" xlink:href="10.1126/science.aad7995">229</jats:related-article> </jats:p>

<jats:title>The Moon's time-variable exosphere</jats:title> <jats:p> Earth's Moon does not have a conventional gaseous atmosphere, but instead an “exosphere” of particles ejected from the surface. Colaprete <jats:italic>et al.</jats:italic> have used NASA's LADEE orbiter to investigate how the exosphere varies over time, by using the glow from sodium and potassium atoms as a probe (see the Perspective by Dukes and Hurley). The exosphere composition varies by a factor of 2 to 3 over the course of a month, as different parts of the Moon are exposed to sunlight. There are also increases shortly after the Moon passes through streams of meteoroids. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6270" page="249" related-article-type="in-this-issue" vol="351" xlink:href="10.1126/science.aad2380">249</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6270" page="230" related-article-type="in-this-issue" vol="351" xlink:href="10.1126/science.aad8245">230</jats:related-article> </jats:p>

<jats:title>Amino acids can lend palladium a hand</jats:title> <jats:p> Metals such as rhodium and palladium (Pd) are adept at activating otherwise inert carbon-hydrogen bonds toward useful reactivity. To get properly oriented, they often require some help from oxygen or nitrogen groups nearby. Appending and removing these directing groups, however, detracts from the efficiency of chemical synthesis. Zhang <jats:italic>et al.</jats:italic> show that amino acids can act as temporary directing groups in the Pd-catalyzed coupling of arenes with aldehydes or ketones. By reversibly binding to these latter substrates just long enough for the Pd catalysis to ensue, the amino acids eliminate the need for more laborious directing group manipulations. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6270" page="252" related-article-type="in-this-issue" vol="351" xlink:href="10.1126/science.aad7893">252</jats:related-article> </jats:p>