Chemical Communications Blog

Photoredox sugar synthesis plausible on early Earth

02 Feb 2018

Scientists in the US have carried out experiments confirming that ultraviolet light could have driven the synthesis of simple prebiotically important sugars under conditions found on early Earth.¹

Source: © Royal Society of Chemistry
UV light photooxidises cyanocuprates, producing aqueous electrons, which are key for putting into motion a reaction network capable of producing glycolaldehyde and glyceraldehyde

Back in 2012, Dougal Ritson and John Sutherland,² at the Medical Research Council Laboratory of Molecular Biology in Cambridge, UK, synthesised sugars from cyanocuprates using ultraviolet light – findings that supported the RNA world hypothesis for the origin of life. Now Zoe Todd and Dimitar Sasselov from the Harvard-Smithsonian Centre for Astrophysics, and their colleagues have performed similar experiments, but at lower, and more representative, wavelengths than those previously considered.

Read the full story by Lynn Murphy on Chemistry World.

References

1 Zoe Todd et al, Chem. Commun., 2018, DOI: 10.1039/c7cc07748c (This article is open access.)

2 D Ritson and J Sutherland, Nat. Chem., 2012, 4, 895 (DOI: 10.1038/nchem.1467)

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Hiding Carbon Dioxide in Oxazolidinones

01 Feb 2018

By Zoë Hearne.

Sometimes it feels as though the pinnacle of synthetic achievement is represented by 20 step total syntheses (with 10 contiguous stereocentres and 5 fused rings…). The level of chemical complexity that can be fashioned from simple building blocks is undoubtedly impressive, but amid such feats it is important not to lose sight of the elegance and worth of simple chemistry, especially when it aims to play a part in resolving profound challenges. One such challenge, which will increasingly confront future generations, is how to reduce the load of carbon dioxide in the atmosphere. One solution is to ‘fix’ carbon dioxide by integrating it into chemical building blocks of added complexity in a sustainable way.

The porosity and high surface area of metal organic frameworks (MOFs), a class of three-dimensional coordination networks, proffers them as ideal materials for capture and storage of carbon dioxide. A team of researchers have designed a MOF which consumes carbon dioxide in a different way: by transformation into value-added chemicals. The group have developed a catalytic MOF embedded with lewis-acidic copper centres capable of converting aziridines to oxazolidinones by the addition of carbon dioxide. Oxazolidinones are used as auxiliaries in chiral synthesis, and are structural components of some antibiotics.

The MOF, termed MMPF-10, is a metal-metalloporphyrin framework constructed from a copper-bound porphyrin ring chemically modified to incorporate 8 benzoic acid moieties, generating an octatopic ligand. These carboxylic acids groups form a second complex with copper in situ, termed a ‘paddlewheel’ for its appearance, with the formula [Cu₂(CO₂)₄]. The resulting network contains hexagonal channels measuring 25.6 x 15.6 Å flanked by four of each of the two copper complexes. With 0.625 % of the catalyst at room temperature, 1 bar CO₂pressure, and in a solvent free environment, MMPF-10 catalyses the transformation of 1-methyl-2-phenylaziridine to yield 63% of the product.

metal-metalloporphyrin MOF catalyses catalyzes carbon dioxide fixation aziridines to oxazolidinones

Topology of MMPF-10 showing hexagonal channels in a) and c), and pentagonal cavities in b). Turquoise: copper, red: oxygen, grey: carbon, blue: nitrogen.

This work, a simple reaction to prepare oxazolidinones, shows that carbon dioxide can be fixed in specialised synthetic building blocks in a sustainable way. This is the way the first paragraph ended, ‘in a sustainable way’, because the challenge of developing such a reaction is two-fold: it must use carbon dioxide, and the reaction conditions must be sustainable. There will be no beneficial offset if the reaction uses a lot of energy, requires many resources, or generates larges quantities of waste. In this reaction the researchers have remained mindful of developing a mild, solvent-free reaction with low catalyst loading employing an earth abundant metal, reflecting an earnest aim to develop practical and sustainable chemistry.

To find out more please read:

A metal-metalloporphyrin framework based on an octatopic porphyrin ligand for chemical fixation of CO₂ with aziridines

Xun Wang, Wen-Yang Gao, Zheng Niu, Lukasz Wojtas, Jason A. Perman, Yu-Sheng Chen, Zhong Li, Briana Aguila and Shengqian Ma
Chem. Commun., 2018, Advance Article
DOI: 10.1039/c7cc08844b

About the Author

Zoë Hearne is a PhD candidate in chemistry at McGill University in Montréal, Canada, under the supervision of Professor Chao-Jun Li. She hails from Canberra, Australia, where she completed her undergraduate degree. Her current research focuses on transition metal catalysis to effect novel transformations, and out of the lab she is an enthusiastic chemistry tutor and science communicator.

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Single-Crystalline NiFe-Hydroxide Nanosheets for Catalyzing Oxygen Evolution

29 Jan 2018

By Tianyu Liu.

A group of scientists led by Prof. Shizhang Qiao has synthesized an oxygen evolution reaction (OER) catalyst combining the merit of low cost, excellent catalytic activity and long lifetime. This OER catalyst is composed of single-crystalline NiFe-hydroxide nanoflakes directly grown on nickel foams. The work has been published recently in ChemComm.

OER, the reaction of producing oxygen gas from water, is an indispensable component of electricity-generation devices using sustainable energy (e.g. fuel cells and photoelectrochemical water splitting cells). OER is usually the bottleneck limiting the overall energy conversion efficiency due to its sluggish kinetics and complex reaction pathways. As such, OER catalysts are needed to accelerate the OER reaction rate. Among the various OER catalysts, noble metal oxides stand out owing to their ultrahigh catalytic activity. However, the “shining” performance is dimmed by their high cost and short lifetime. Thus, obtaining alternatives with comparable OER catalytic activity as well as long-term stability is required to advance the utilisation of sustainable energy.

To address this challenge, the authors turned their attention to a low-cost transition metal, nickel. They developed a hydrothermal method using nickel foams to grow highly crystalline and near-vertically aligned NiFe-hydroxide nanosheets as OER catalysts (Figure 1a). The seamless integration between the hydroxide nanosheets and the nickel substrates reduces the contact resistance and facilitates interfacial electron transfer. The near-vertical orientation (Figure 1b) allows water molecules to fully contact the catalysts. Both of the characteristics render excellent OER catalytic activity. Additionally, the high crystallinity (Figure 1c) ensures the catalysts are robust enough to withstand extensive use without degradation in performance.

Figure 1. (a) The schematic illustration of the synthetic procedures of the NiFe-hydroxide [Fe-Ni(OH)2] nanosheets supported on nickel foams (NF). (b) The scanning electron microscopy image shows the near-vertically aligned nanosheets on a piece of nickel foam. (c) The transmission electron microscopy image reveals the crystallinity of the synthesized catalyst.

The NiFe-hydroxide nanosheets outperform most of the state-of-the-art OER catalysts, including those containing noble metal elements. Specifically, the nanosheets exhibit an onset potential of 1.497 V (Figure 2). The onset potential is a measure of the catalytic activity that equals the magnitude of potential required to yield a current density of 10 mA/cm² (when appreciable amount of oxygen gas is evolved). Outstandingly, the onset potential of the NiFe-hydroxide is the smallest among the catalysts selected for comparison.

Figure 2. The polarisation curves of different OER catalysts. The onset potential is marked by the dotted line in the inset.

The catalytic activity is also highly stable, with no loss in performance after at least 100 h of measurement. Interestingly, the onset potential further shifts to a lower value of 1.465 V after 100 h. The authors attributed this observation to a “self-activation” process that involves the formation and accumulation of nickel oxyhydroxide (NiOOH) on the surface of the nanosheets.

The hydrothermal method demonstrated here could be used to synthesize other cost-effective crystalline catalysts to develop catalysts for reactions beyond OER, such as hydrogen evolution and carbon dioxide reduction.

To find out more please read:

Free-Standing Single-Crystalline NiFe-Hydroxide Nanoflake Arrays: A Self-Activated and Robust Electrocatalyst for Oxygen Evolution

Jinlong Liu, Yao Zheng, Zhenyu Wang, Zhouguang Lu, Anthony Vasileff and Shi-Zhang Qiao

Chem. Commun. 2017, DOI: 10.1039/c7cc08843d

About the blogger:

Tianyu Liu obtained his Ph.D. (2017) in Physical Chemistry from University of California, Santa Cruz in United States. He is passionate about scientific communication to introduce cutting-edge research to both the general public and scientists with diverse research expertise. He is a blog writer for Chem. Commun. and Chem. Sci. More information about him can be found at http://liutianyuresearch.weebly.com/.

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Tech red unmasked

24 Jan 2018

By Rebecca Withers.

Tech red, an enigmatic technetium compound that has resisted characterisation for half a century, has been identified using chemical detective-work and computer modelling. The molecule’s unusual chemistry may explain why it has proven so difficult to unmask.¹

Source: © Bradley Childs
Tech red forms a red, oily liquid upon condensation

Nuclear chemists have been running into a volatile red oxide of technetium – Tc, a radioactive metal – since at least the 1960s.² ‘Everybody seems to have accidentally made this a couple of times,’ notes Keith Lawler, a postdoctoral researcher at the University of Nevada Las Vegas (UNLV), US. Although the telltale hue makes tech red easy to spot, it has gone unidentified over the intervening decades. Tech red refuses to form crystals, so can’t studied by crystallographic methods, while technetium’s radioactivity is an inherent barrier to researching its compounds. ‘There are only a handful of laboratories who can work with large amounts of technetium, and even fewer who have access to anything other than simple characterisation techniques,’ explains John McCloy, who investigates radioactive materials at Washington State University, US.

Read the full story by Alexander Whiteside on Chemistry World.

1 K V Lawler et al, Chem Commun., 2018, DOI: 10.1039/c7cc09191e (This article is free to access until 7 March 2018.)

2 C Rulfs, R Pacer and R Hirsch, J. Inorg. Nucl. Chem., 1967, 29, 681 (DOI: 10.1016/0022-1902(67)80323-3 )

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Shoot the Messenger: Circular DNA-Graphene Oxide Material Targets mRNA in Living Cells

19 Jan 2018

By Zoë Hearne.

Schematic of the circular DNA cDNA/GO graphene oxide platform fabrication for intracellular mRNA messenger RNA imaging and gene therapy.

Scheme showing how cDNA/GO enters the cell and interacts with mRNA

Did you know that the combined length of DNA in your body’s cells is a number so large that the only references I could find use cosmic distances as a reference? Try twice the diameter of the solar system, or the distance to the moon and back 1500 times. Despite the complexity and infinite detail encountered when studying science, it is often something so simple as size that gives us pause. How can DNA be both uncomprehendingly huge and tiny at the same time?

The major function of DNA is to encode proteins, a process which begins with the transcription of genes into single-stranded messenger RNA (mRNA) molecules. It is mRNA that is directly translated into the strands of amino acids which fold to form proteins.

A team of researchers at Fuzhou University in China have developed a graphene oxide and circularised single-stranded DNA (cDNA/GO) hybrid material capable of penetrating living cells and binding mRNA. The material’s utility is shown in two practical applications: mRNA imaging and nucleotide therapeutics. The authors chose the mRNA of survivin and c-raf kinase as targets, because the enzymes are involved in carcinogenesis, and the mRNA are overexpressed in cancer cells and can be used as biomarkers.

cDNA was chosen for its increased stability over linear single-stranded DNA, which is rapidly degraded in vivo by exonucleases. For mRNA imaging the material is designed with a fluorescent dye coupled to the cDNA. GO was chosen as a hydrophilic delivery scaffold capable of adsorbing cDNA and quenching the dye. When cDNA/GO was incubated with HeLa cells (a cancer cell strain) a time-dependent increase in fluorescence was observed in the cytoplasm. Fluorescence is restored when cDNA encounters the target and desorbs from the GO to form a duplex with the mRNA.

CLSM images acquired for HeLa cells treated with both survivin and c-raf targeted cDNA/GO for duplexed intracellular mRNA imaging

The mRNA of both survivin and c-raf kinase can be imaged in living cells with cDNA/GO.

The researchers also probed whether the material might serve as a therapeutic agent: if formation of the cDNA-mRNA duplex blocks translation it may reduce the load of c-raf kinase and survivin in the cell and influence cancer cell growth. Accordingly, the researchers found that when the HeLa cells were incubated with cDNA/GO, cell proliferation was inhibited in a dose-dependent manner.

This research contributes a robust design which can be applied to diverse mRNA targets because optimisable properties such as stability, bioavailability and selectivity are largely independent of the sequence of nucleotides.

To find out more please read:

Circular DNA: a stable probe for highly efficient mRNA imaging and gene therapy in living cells

Jingying Li, Jie Zhou, Tong Liu, Shan Chen, Juan Li and Huanghao Yang
Chem. Commun., 2018, Advance Article
DOI: 10.1039/C7CC08906F

About the author

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Tuning the Size of Metal-Organic Framework Crystals by Decoupling Nucleation and Growth Processes

17 Jan 2018

By Tianyu Liu.

A group of scientists from Tsinghua University in China have made a breakthrough in enhancing the controllability of the metal-organic framework (MOF) crystal size.

MOF represents a family of microporous crystals consisting of metal node-organic ligand coordination networks. They have shown potential in versatile applications including hydrogen storage, catalysis and electrochemical energy storage. Since their performance strongly correlates to the crystal size, synthesizing MOF crystals with tunable sizes and high yields is necessary to allow fundamental studies on the size-performance relationship. Unfortunately, the conventional size-controlling methods either require complex operations or exhibit low yields.

Now in ChemComm, Tiefeng Wang and coworkers demonstrate a method that can easily tune the size of MOF crystals. The mechanism is based on decoupling nucleation and growth processes. Unlike traditional strategies that mingle all metal precursors and organic ligands together in a solvent, this newly developed protocol initially mixes only a small portion of metal precursors with organic ligands. The metal precursors quickly coordinate with surrounding ligands to form small MOF clusters (the “nucleation” stage). Due to the limited supply of the metal precursors, the growth of these clusters into large crystals is unfavorable. Subsequently, the remaining metal precursors are introduced into the cluster-containing solution. The clusters then continue to grow into MOF crystals (the “growth” stage). Because the crystals develop directly from the small clusters (i.e. the seeds), the number of the seeds and the total concentration of the added metal precursors control the resulting MOF crystal size (Figure 1).

Figure 1. A schematic illustration of the growth of MOF crystals via a typical conventional method (top) and the reported decoupling method (down).

Using this method, the authors prepared a series of Pt@ZIF-8 MOF crystals (with sizes ranging from 45 nm to 440 nm) and investigated their ability to catalyze the reaction of 1-hexene hydrogenation. The catalytic activity of different sized crystals was quantified, with a linear correlation observed between the size and the activity (Figure 2).

Figure 2. The linear relationship between the Pt@ZIF-8 MOF size (r) and the hydrogenation reaction rate (D). r0 and D0 represent the size and the reaction rate of the smallest MOF (45 nm).

This reported approach is expected to be applicable for synthesizing MOF crystals other than Pt@ZIF-8. The availability of size-tunable MOFs will facilitate mechanistic studies in determining the optimal crystal size for different applications.

To find out more please read:

A General and Facile Strategy for Precisely Controlling the Crystal Size of Monodispersed Metal-Organic Frameworks via Separating the Nucleation and Growth

Xiaocheng Lan, Ning Huang, Jinfu Wang and Tiefeng Wang

Chem. Commun. 2017, DOI: 10.1039/c7cc08244d

About the blogger:

Tianyu Liu obtained his Ph.D. (2017) in Physical Chemistry from University of California, Santa Cruz in United States. He is passionate about scientific communication to introduce cutting-edge research to both the general public and scientists with diverse research expertise. He is an online blog writer for Chem. Commun. and Chem. Sci. More information about him can be found at http://liutianyuresearch.weebly.com/.

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ChemComm Emerging Investigators 2018 – Call for Papers

08 Jan 2018

By Garima Sharma, Deputy Editor.

Profiling the very best research from scientists in the early stages of their independent careers

We were delighted to publish the 2017 ChemComm Emerging Investigators issue last year and we continue to be overwhelmed by the community’s positive response. We are now excited to announce the forthcoming 2018 ChemComm Emerging Investigators issue.

This special issue, now on its eighth year, showcases high quality research being carried out by international researchers in the early stages of their independent careers. This annual issue features principal investigators whose work has the potential to influence future directions in science or result in new and exciting developments.

If you are interested in submitting to this issue please contact the ChemComm Editorial Office in the first instance and please take a look at the excellent research and Feature articles published by your peers in our previous issues in 2011, 2012, 2013, 2014, 2015 and 2016.

Please note that authors must not have featured in a previous ChemComm Emerging Investigators issue. The deadline for submission to this issue is 27 March 2018.

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Molecular box treats chemists to a strained surprise

02 Jan 2018

By Rebecca Withers.

Introducing pillar[4]pyridinium – the first of a new family of macrocycles

Pillar[4]pyridinium
Source: Grzegorz Sobczak Oksana Danylyuk and Volodymyr Sashuk

Scientists in Poland have made the most compact multiply charged macrocycle to date. Pillar[4]pyridinium is a cyclic tetramer consisting of four pyridyl units with methylene bridges between their nitrogens and para carbons. The quadruply charged molecule has a very symmetrical and incredibly strained structure. It represents a new class of cationic macrocycles, the pillar[n]pyridiniums.

Read the full story by Jennifer Newton on Chemistry World.

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ChemComm Prizewinners at the 44th Symposium on Main Group Element Chemistry

21 Dec 2017

By Garima Sharma, Deputy Editor.

The 44^th Symposium on Main Group Element Chemistry took place on the 7^th to 9^th December at the Tokyo Institute of Technology. Over 250 delegates attended the symposium which was chaired by Prof Kei Goto (TITech).

ChemComm was proud to sponsor two prizes, which were chosen out of 60 oral presentations and 108 poster presentations.

The winner of the ChemComm oral presentation was Mr Shogo Morisako (Graduate School of Science, Hiroshima University) who presented on ‘Syntheses and Reactivities of New Multiple Bond Boron Compounds’.

Mr Shogo Morisako (left) being presented his award by Dr Hiromitsu Urakami (right) on behalf of Chemical Communications

The winner of the ChemComm poster presentation was Mr. Tomoyuki Kosai (Graduate School of Science, Tohoku University) who presented on ‘Activation of Dihydrogen Using Disilenes Bearing Amino and Boryl Groups’.

Mr Tomoyuki Kosai (left) being presented his award by Dr Hiromitsu Urakami (right) on behalf of Chemical Communications

Congratulations to both Mr Morisako and Mr Kosai, we wish you both the best for the future!

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Suzuki–Miyaura–hydrogenation targets 3D drugs

21 Dec 2017

By Rebecca Withers.

Scientists in the UK have unveiled a way to make pharmaceutical molecules with increased 3D characteristics. The single pot Suzuki–Miyaura–hydrogenation reaction results in sp²–sp³ linked pharmaceutically relevant molecules.

Source: Royal Society of Chemistry
A single pot Suzuki–Miyaura-hydrogenation can be used to furnish lead and fragment-like products in good to excellent yields

The number of tetrahedral carbon atoms, or how 3D a molecule is, is one factor that determines the success of a molecule in clinical drug trials. Molecules with a high sp³ fraction are in demand, however current methods to make them suffer drawbacks. The Suzuki–Miyaura reaction is common for the cross-coupling of sp²–sp³ systems, but alkyl boron or alkyl halides are prone to β-elimination and other side reactions, producing mixtures of products.

Read the full story by Suzanne Howson on Chemistry World.

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Chemical Communications Blog

Photoredox sugar synthesis plausible on early Earth

References

Hiding Carbon Dioxide in Oxazolidinones

Single-Crystalline NiFe-Hydroxide Nanosheets for Catalyzing Oxygen Evolution

Tech red unmasked

Shoot the Messenger: Circular DNA-Graphene Oxide Material Targets mRNA in Living Cells

Tuning the Size of Metal-Organic Framework Crystals by Decoupling Nucleation and Growth Processes

ChemComm Emerging Investigators 2018 – Call for Papers

Molecular box treats chemists to a strained surprise

ChemComm Prizewinners at the 44th Symposium on Main Group Element Chemistry

Suzuki–Miyaura–hydrogenation targets 3D drugs

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