Chemical Science Blog

Reprogramming the genetic code of bacteria to incorporate an unnatural amino acid has allowed scientists in the Netherlands to create a new metalloenzyme capable of catalysing an enantioselective reaction.

The artificial metalloenzymes were applied in a catalytic asymmetric Friedel–Crafts alkylation reaction

‘Nature is extremely good at catalysing reactions with very high rate accelerations and very high selectivity. But it does so, from our perspective, with a relatively limited set of reactions,’ explains Gerard Roelfes from the University of Groningen, the Netherlands, who led the study. His group is targeting existing reactions that use traditional catalysts, but fail to achieve the same rate acceleration and selectivity as enzyme catalysed reactions.

Read the full article in Chemistry World»

Read the original journal article in Chemical Science:
Novel artificial metalloenzymes by in vivo incorporation of metal-binding unnatural amino acids
vana Drienovská, Ana Rioz-Martínez, Apparao Draksharapu and Gerard Roelfes  
Chem. Sci., 2015, Advance Article
DOI: 10.1039/C4SC01525H, Edge Article

University chemistry students are taught that the shapes and electronics of inorganic complexes are predictable. For example, d8 square-planar Pd(ii) and Pt(ii) complexes are invariably low spin, while d3–d7 tetrahedral complexes are high spin. Now, researchers in the US have thrown away the textbook by synthesising a square-planar Fe(ii) complex that is not only high spin, but has a different core (FeO2NCl) to the only other examples of this complex type, all of which feature an FeO4 core. 

Read the full article in Chemistry World» 

Read the original journal article in Chemical Science:
A high-spin square-planar Fe(II) complex stabilized by a trianionic pincer-type ligand and conclusive evidence for retention of geometry and spin state in solution
M. E. Pascualini, N. V. Di Russo, A. E. Thuijs, A. Ozarowski, S. A. Stoian, K. A. Abboud, G. Christou and A. S. Veige  
Chem. Sci., 2015, Advance Article
DOI: 10.1039/C4SC02634A, Edge Article

Scientists in South Korea have developed a reversible electrochemical mirror (REM) that can switch between a transparent and reflective state, and remain reflective for up to two hours without external electrical power. Such mirrors could be used in smart windows to control lighting and reduce cooling costs for buildings.

The REM, developed by the group of Eunkyoung Kim at Yonsei University, consists of a thin layer of silver-containing electrolyte sandwiched between two transparent electrode panes…

Read the full article in Chemistry World»

Read the original journal article in Chemical Science:
Switchable silver mirrors with long memory effects
Chihyun Park, Seogjae Seo, Haijin Shin, Bhimrao D. Sarwade, Jongbeom Na and Eunkyoung Kim  
Chem. Sci., 2014, DOI: 10.1039/C4SC01912A

Researchers in China have achieved ferromagnetism in graphitic carbon nitride, g-C₃N₄, by introducing hydrogen dangling bonds into its two-dimensional structure, making the material suitable for spintronic devices.

Spintronics exploits the intrinsic spin of electrons and their associated magnetic moments and charges to make solid-state devices such as storage media and sensors. Generally, the materials used to make these devices are ferromagnetic, that is, they form permanent magnets. Ultrathin 2D nanosheets can be used to construct such devices because they exhibit spin ordering within their structures.

Read the full article in Chemistry World»

Read the original journal article in Chemical Science:
Hydrogen dangling bonds induce ferromagnetism in two-dimensional metal-free graphitic-C3N4 nanosheets
Kun Xu, Xiuling Li, Pengzuo Chen, Dan Zhou, Changzheng Wu, Yuqiao Guo, Lidong Zhang, Jiyin Zhao, Xiaojun Wu and Yi Xie  
DOI: 10.1039/C4SC02576H
This article is Open Access

All of the referee-recommended articles below are free to access until 9th November 2014

DNA display of fragment pairs as a tool for the discovery of novel biologically active small molecules
J.-P. Daguer, C. Zambaldo, M. Ciobanu, P. Morieux, S. Barluenga and N. Winssinger  
Chem. Sci., 2014, Advance Article
DOI: 10.1039/C4SC01654H, Edge Article

Macromolecular prodrugs of ribavirin: towards a treatment for co-infection with HIV and HCV
Anton A. A. Smith, Kaja Zuwala, Mille B. L. Kryger, Benjamin M. Wohl, Carlos Guerrero-Sanchez, Martin Tolstrup, Almar Postma and Alexander N. Zelikin  
Chem. Sci., 2015, Advance Article
DOI: 10.1039/C4SC02754J, Edge Article
This article is Open Access

Organic/Inorganic Double-Layered Shells for Multiple Cytoprotection of Individual Living Cells
Daewha Hong, Hojae Lee, Eun Hyea Ko, Juno Lee, Hyeoncheol Cho, Matthew Park, Sung Ho Yang and Insung S Choi  
Chem. Sci., 2014, Accepted Manuscript
DOI: 10.1039/C4SC02789B, Edge Article
This article is Open Access

Ultra-sensitive pH control of supramolecular polymers and hydrogels: pKa matching of biomimetic monomers
B. J. Cafferty, R. R. Avirah, G. B. Schuster and N. V. Hud  
Chem. Sci., 2014, Advance Article
DOI: 10.1039/C4SC02182G, Edge Article

Scientists in the US have developed a method for successfully transporting chemotherapeutic d-peptides into the cell cytosol.

D-peptides – also known as mirror peptides, as their constituent amino acid building blocks are mirror images of the naturally occurring l-amino acids – have been an intriguing target in drug development for many years. Their unnatural stereochemistry results in high resistance to proteolytic degradation as intracellular enzymes are unable to act upon them – usually a major pathway for the destruction and removal of ‘foreign’ peptides, including those intended as therapeutic agents, in cells. However, transporting these molecules across cell membranes has been a significant barrier to their potential application.

Read the full article in Chemistry World»

Read the original journal article in Chemical Science – it’s free to access until 11th November:
Delivery of mirror image polypeptides into cells
Amy E. Rabideau, Xiaoli Liao and Bradley L. Pentelute  
Chem. Sci., 2014, Advance Article, DOI: 10.1039/C4SC02078B

In this Chemical Science Edge article, Michael Ward, Christopher Hunter and co-workers at the Department of Chemistry, University of Sheffield report tunable host-guest chemistry of an octanuclear cobalt(II) coordination cage with a range of organic guests. The resultant non-covalently bound guests have very different binding constants in different pH environments, making binding tunable and completely reversible.   

The team found that the coordination cage provided a good guest space for a range of organics, including substituted adamantanes. Substitutents which could be charged, such as carboxylic acids and amines, were particularly useful to drive and rationalize the binding observed. NMR also played a powerful role in this work. In this context, the paramagnetic complex host resulted in clear distinguishable signals, differentiating free or bound cage species, and thereby acting as a shift reagent. This effect could also be quantified, allowing the strength and extent of the host-guest binding to be shown. 

Coordination cage and NMR study of effect on chemical shift and binding extent with changing pH

An example with potentially high importance is described using 1-aminoadamantane, a prescription drug used to treat Parkinson’s disease and as an influenza anti-viral. Complete reversible binding was achieved with a binding constant difference of three orders of magnitude between the protonated and neutral forms of the drug. Similar behaviour was observed with other N-basic materials like nicotine and the anaesthetic substituted imidazole drug, demotidine. Mechanistic considerations were further examined with experiments using carboxylic acids, where solvation effects were also shown to play a key role.  

In this article, a practical example of pH controlled, reversible guest binding of functional organic molecules is described. An elegant and practical application of NMR spectroscopy is also shown. Applications for delivery and controlled release of suitable drug, catalyst or other functional organic material cannot be far off.   

Read this Chemical Science Edge article today!   

pH dependent binding of guests in the cavity of a polyhedral coordination cage: reversible uptake and release of drug molecules
William Cullen, Simon Turega, Christopher A. Hunter and Michael D. Ward.,
doi 10.1039/c4sc02090a

We are delighted to share with you the top 25 most downloaded articles in Chemical Science from April–June 2014.

Top 25 most downloaded Chemical Science articles for Q2 2014

Novel hole transporting materials based on triptycene core for high efficiency mesoscopic perovskite solar cells
Anurag Krishna, Dharani Sabba, Hairong Li, Jun Yin, Pablo P. Boix, Cesare Soci, Subodh G. Mhaisalkar and Andrew C. Grimsdale
DOI: 10.1039/C4SC00814F

Copper catalyzed Heck-like cyclizations of oxime esters
Adele Faulkner, Nicholas J. Race, James S. Scott and John F. Bower
DOI: 10.1039/C4SC00652F

Enantioselective direct α-alkylation of cyclic ketones by means of photo-organocatalysis
Elena Arceo, Ana Bahamonde, Giulia Bergonzini and Paolo Melchiorre
DOI: 10.1039/C4SC00315B

Oxygen nucleophiles as reaction partners in photoinduced, copper-catalyzed cross-couplings: O-arylations of phenols at room temperature
Yichen Tan, José María Muñoz-Molina, Gregory C. Fu and Jonas C. Peters
DOI: 10.1039/C4SC00368C

Efficient C–H bond activations via O2 cleavage by a dianionic cobalt(II) complex
Andy I. Nguyen, Ryan G. Hadt, Edward I. Solomon and T. Don Tilley
DOI: 10.1039/C4SC00108G

Sunlight photocatalyzed regioselective β-alkylation and acylation of cyclopentanones
Megumi Okada, Takahide Fukuyama, Keiichi Yamada, Ilhyong Ryu, Davide Ravelli and Maurizio Fagnoni
DOI: 10.1039/C4SC01072H

Copper catalyzed direct alkenylation of simple alkanes with styrenes
Yefeng Zhu and Yunyang Wei
DOI: 10.1039/C4SC00093E

Transition metal-catalyzed direct nucleophilic addition of C–H bonds to carbon–heteroatom double bonds
Xi-Sha Zhang, Kang Chen and Zhang-Jie Shi
DOI: 10.1039/C3SC53115E

Evaluating metal–organic frameworks for natural gas storage
Jarad A. Mason, Mike Veenstra and Jeffrey R. Long
DOI: 10.1039/C3SC52633J

Selective radical amination of aldehydic C(sp2)–H bonds with fluoroaryl azides via Co(II)-based metalloradical catalysis: synthesis of N-fluoroaryl amides from aldehydes under neutral and nonoxidative conditions
Li-Mei Jin, Hongjian Lu, Yuan Cui, Christopher L. Lizardi, Thiago N. Arzua, Lukasz Wojtas, Xin Cui and X. Peter Zhang
DOI: 10.1039/C4SC00697F

Catalytic enantioselective synthesis of 2-aryl-chromenes
Bi-Shun Zeng, Xinyi Yu, Paul W. Siu and Karl A. Scheidt
DOI: 10.1039/C4SC00423J

Dialkylbiaryl phosphines in Pd-catalyzed amination: a user’s guide
David S. Surry and Stephen L. Buchwald
DOI: 10.1039/C0SC00331J

Frustrated Lewis pair chemistry of carbon, nitrogen and sulfur oxides
Douglas W. Stephan and Gerhard Erker
DOI: 10.1039/C4SC00395K

Carbon–fluorine bond cleavage in fluoroarenes via a niobium(III) imido complex: from stoichiometric to catalytic hydrodefluorination
Thomas L. Gianetti, Robert G. Bergman and John Arnold
DOI: 10.1039/C4SC00006D
From themed collection Celebrating the 2014 RSC Prize and Award Winners

Rh(III)-catalyzed C–H functionalization/aromatization cascade with 1,3-dienes: a redox-neutral and regioselective access to isoquinolines
Dongbing Zhao, Fabian Lied and Frank Glorius
DOI: 10.1039/C4SC00628C

Iodoarene-catalyzed fluorination and aminofluorination by an Ar-I/HF·pyridine/mCPBA system
Satoru Suzuki, Tomohiro Kamo, Kazunobu Fukushi, Takaaki Hiramatsu, Etsuko Tokunaga, Toshifumi Dohi, Yasuyuki Kita and Norio Shibata
DOI: 10.1039/C3SC53107D

Complete stereodivergence in the synthesis of 2-amino-1,3-diols from allenes
Christopher S. Adams, R. David Grigg and Jennifer M. Schomaker
DOI: 10.1039/C4SC01214C

An ExBox [2]catenane
Michal Juríček, Jonathan C. Barnes, Nathan L. Strutt, Nicolaas A. Vermeulen, Kala C. Ghooray, Edward J. Dale, Paul R. McGonigal, Anthea K. Blackburn, Alyssa-Jennifer Avestro and J. Fraser Stoddart
DOI: 10.1039/C4SC00488D
From themed collection Celebrating the 2014 RSC Prize and Award Winners

Aluminium–ligand cooperation promotes selective dehydrogenation of formic acid to H2 and CO2
T. W. Myers and L. A. Berben
DOI: 10.1039/C4SC01035C

Synthesis, electronic structure and reactivity of bis(imino)pyridine iron carbene complexes: evidence for a carbene radical
Sarah K. Russell, Jordan M. Hoyt, Suzanne C. Bart, Carsten Milsmann, S. Chantal E. Stieber, Scott P. Semproni, Serena DeBeer and Paul J. Chirik
DOI: 10.1039/C3SC52450G

Non-directed allylic C–H acetoxylation in the presence of Lewis basic heterocycles
Hasnain A. Malik, Buck L. H. Taylor, John R. Kerrigan, Jonathan E. Grob, K. N. Houk, J. Du Bois, Lawrence G. Hamann and Andrew W. Patterson
DOI: 10.1039/C3SC53414F

Rethinking the term “pi-stacking”
Chelsea R. Martinez and Brent L. Iverson
DOI: 10.1039/C2SC20045G
From themed collection Physical Chemistry

Stereoselective allylboration of imines and indoles under mild conditions. An in situ E/Z isomerization of imines by allylboroxines
Rauful Alam, Arindam Das, Genping Huang, Lars Eriksson, Fahmi Himo and Kálmán J. Szabó
DOI: 10.1039/C4SC00415A

Cobaltate anion couples terminal dienes with trifluoroacetic anhydride: a direct fluoroacylation of 1,3-dienes
Benjamin L. Kohn and Tomislav Rovis
DOI: 10.1039/C4SC00743C

Phosphorescent nematic hydrogels and chromonic mesophases driven by intra- and intermolecular interactions of bridged dinuclear cyclometalated platinum(II) complexes
Xin-Shan Xiao, Wei Lu and Chi-Ming Che
DOI: 10.1039/C4SC00143E

Chemical Science is the Royal Society of Chemistry’s flagship journal; publishing research articles of exceptional significance and high-impact reviews from across the chemical sciences. The journal’s latest (2013) Impact Factor is 8.6. Research in Chemical Science is not only of the highest quality but also has excellent visibility; this is reflected in our latest citation profile.

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All of the referee-recommended articles below are free to access until 15th October 2014

Understanding nano-impacts: impact times and near-wall hindered diffusion
Enno Kätelhön and Richard G. Compton  
Chem. Sci., 2014, Advance Article
DOI: 10.1039/C4SC02288B, Edge Article

Comprehensive study of carbon dioxide adsorption in the metal–organic frameworks M2(dobdc) (M = Mg, Mn, Fe, Co, Ni, Cu, Zn)
Wendy L. Queen, Matthew R. Hudson, Eric D. Bloch, Jarad A. Mason, Miguel I. Gonzalez, Jason S. Lee, David Gygi, Joshua D. Howe, Kyuho Lee, Tamim A. Darwish, Michael James, Vanessa K. Peterson, Simon J. Teat, Berend Smit, Jeffrey B. Neaton, Jeffrey R. Long and Craig M. Brown  
Chem. Sci., 2014, Advance Article
DOI: 10.1039/C4SC02064B, Edge Article

Bifunctional nanoparticle–SILP catalysts (NPs@SILP) for the selective deoxygenation of biomass substrates
Kylie L. Luska, Jennifer Julis, Eli Stavitski, Dmitri N. Zakharov, Alina Adams and Walter Leitner  
Chem. Sci., 2014, Advance Article
DOI: 10.1039/C4SC02033B, Edge Article

End functional ROMP polymers via degradation of a ruthenium Fischer type carbene
Amit A. Nagarkar and Andreas F. M. Kilbinger  
Chem. Sci., 2014, Advance Article
DOI: 10.1039/C4SC02242D, Edge Article