Volume 5 Issue 10, October 2013

Volume 5 Issue 10

The cover image shows an artistic impression of large single crystals comprising covalent organic networks. A team led by James Wuest made these materials through the reversible polymerization of organic monomers bearing four tetrahedrally oriented nitroso groups and characterized them using single-crystal X-ray diffraction. Such a modular construction is typically used to build monocrystalline materials held together by non-covalentbonding interactions, but is now also shown to work for covalently bonded analogues.

Article p830; News & Views p810

IMAGE: SOPHIE DUBOIS ONCE UPON A TIME IN THE LAB (ORIGINAL PAINTING: ACRYLIC ON CANVAS, 2012).

COVER DESIGN: ALEX WING

Thesis

  • Thesis |

    When it comes to practical chemistry demonstrations designed to provoke the senses, Bruce Gibb suggests that we should follow our noses rather than it all being about bangs and flashes.

    • Bruce C. Gibb

Books and Arts

Research Highlights

Blogroll

News and Views

  • News & Views |

    Millimetre-sized single crystals of covalent organic frameworks have been constructed by taking advantage of a reversible dimerization reaction of nitroso groups.

    • Michael Mastalerz
  • News & Views |

    Covalently bonding groups to the walls of carbon nanotubes has been previously observed to quench their photoluminescence. Now, it has been shown that, if you get the chemistry just right, their photoluminescence can in fact be significantly brightened by introducing defects through functionalization.

    • Qing Hua Wang
    •  & Michael S. Strano
  • News & Views |

    Preparing powerful reactive intermediates such as enolates and homoenolates for C–C bond formation used to require strong bases and stoichiometric reagents. They can now be catalytically generated from α-functionalized aldehydes or even from saturated esters under mild conditions using N-heterocyclic carbene catalysts.

    • Jeffrey W. Bode
  • News & Views |

    Although caesium is well known in its oxidation state +I, many chemists have speculated about a possible higher state. Such a species has not yet been prepared, but based on quantum-chemical calculations CsFn compounds have now been predicted to be stable.

    • Sebastian Riedel
    •  & Peter Schwerdtfeger

Review

Articles

  • Article |

    Modular construction using connectable molecular subunits is a powerful strategy for making new carbon-based materials. So far, large crystals have been produced only from subunits linked by weak interactions. Covalently bonded analogues have now been prepared by reversible self-addition polymerization of suitable monomers and structurally characterized by single-crystal X-ray diffraction.

    • Daniel Beaudoin
    • , Thierry Maris
    •  & James D. Wuest
  • Article |

    Direct β-carbon activation of saturated carbonyl compounds represents a significant fundamental challenge in organic chemistry. Here, the catalytic activation of saturated ester β-sp3 carbon as nucleophile via N-heterocyclic carbene organocatalysis is reported. The catalytically generated nucleophilic β-carbon undergoes enantioselective reactions with various electrophiles.

    • Zhenqian Fu
    • , Jianfeng Xu
    • , Tingshun Zhu
    • , Wendy Wen Yi Leong
    •  & Yonggui Robin Chi
  • Article |

    The controlled functionalization of single-walled carbon nanotubes has been shown to brighten their photoluminescence up to 28 times, which challenges our current understanding of how chemical defects affect low-dimensional carbon materials. This significantly improved photon conversion efficiency promises to advance a broad range of optoelectronic and imaging applications based on carbon nanotubes.

    • Yanmei Piao
    • , Brendan Meany
    • , Lyndsey R. Powell
    • , Nicholas Valley
    • , Hyejin Kwon
    • , George C. Schatz
    •  & YuHuang Wang
  • Article |

    Caesium has so far not been found in oxidation states higher than +1, but quantum chemical calculations have now shown that, under high pressures, 5p inner shell electrons of caesium can participate in — and become the main components of — bonds. Caesium is predicted to form stable CsFn molecules that resemble isoelectronic XeFn.

    • Mao-sheng Miao
  • Article |

    Biological receptors communicate information through ligand-induced conformational changes. A synthetic receptor with a boron-containing binding site that can selectively and reversibly complex a ligand (such as a purine nucleoside) is shown to function in a similar fashion. The resulting conformational change is relayed through the receptor, communicating structural information about the ligand to a spectroscopic reporter more than 2 nm away.

    • Robert A. Brown
    • , Vincent Diemer
    • , Simon J. Webb
    •  & Jonathan Clayden
  • Article |

    Diversity oriented synthesis (DOS) aims to build structurally diverse compound libraries — potentially useful in drug discovery — from a small number of starting materials. Here, the build/couple/pair algorithm — commonly used in DOS — is extended to incorporate variations in the coupling step as well as in the starting materials. This produces a compound library with exceptionally high diversity in fewer than five steps from a common precursor.

    • Henning S. G. Beckmann
    • , Feilin Nie
    • , Caroline E. Hagerman
    • , Henrik Johansson
    • , Yaw Sing Tan
    • , David Wilcke
    •  & David R. Spring
  • Article |

    The site-specific incorporation of dendritic DNA amphiphiles into a DNA cage controls whether the resultant structures show intermolecular self-assembly or intramolecular assembly. Intramolecular assembly creates a hydrophobic core within the cage that is capable of encapsulating small molecules. These molecules can be released on addition of specific DNA strands.

    • Thomas G. W. Edwardson
    • , Karina M. M. Carneiro
    • , Christopher K. McLaughlin
    • , Christopher J. Serpell
    •  & Hanadi F. Sleiman
  • Article |

    A base-stabilized silicon analogue of a reactive carbon species (vinyl carbene) is reported that features a silicon–silicon double bond and a silylene functionality, coordinated by an N-heterocyclic carbene. Ultraviolet–visible light and nuclear magnetic resonance spectroscopy in solution confirms that disilenyl silylene exists in equilibrium with the corresponding cyclotrisilene and free N-heterocyclic carbene.

    • Michael J. Cowley
    • , Volker Huch
    • , Henry S. Rzepa
    •  & David Scheschkewitz
  • Article |

    An asymmetric pentalene-containing C1(51383)-C84 fullerene cage is found in two different metal carbide metallofullerenes. This particular cage can, in simple steps, rearrange into many well-known fullerene cages that are more stable and more symmetric, suggesting it is likely that metallofullerenes are generated by a ‘top-down’ formation mechanism.

    • Jianyuan Zhang
    • , Faye L. Bowles
    • , Daniel W. Bearden
    • , W. Keith Ray
    • , Tim Fuhrer
    • , Youqing Ye
    • , Caitlyn Dixon
    • , Kim Harich
    • , Richard F. Helm
    • , Marilyn M. Olmstead
    • , Alan L. Balch
    •  & Harry C. Dorn
  • Article |

    The trioxacarcins are polyoxygenated natural products that potently inhibit the growth of cultured human cancer cells. Here, the syntheses of trioxacarcin A, DC-45-A1 and structural analogues are described — the majority of which were found to be active in antiproliferative assays. A convergent, component-based route comprising sequential stereoselective glycosylation reactions allows assembly of these analogues in 11 steps or fewer.

    • Thomas Magauer
    • , Daniel J. Smaltz
    •  & Andrew G. Myers

In Your Element

  • In Your Element |

    Somobrata Acharya explores the history, properties and uses of lead — an ancient metal that is still very relevant to today's technologies, but should be used with caution.

    • Somobrata Acharya