Archive for the ‘News’ Category

On the Hunt for HOCl

Hypochlorous acid (HOCl) is a weak acid, formed from the reaction of chlorine with water. In addition to its use as a reagent in organic chemistry, it has significant biological relevance. HOCl is generated in biological systems in a reaction between chloride ions and hydrogen peroxide, catalysed by the enzyme myeloperoxidase.

This enzyme is secreted by phagocytes (cells which help protect the body by ‘ingesting’ bacteria) when they are activated during an immune response. Hypochlorite (ClO-), the conjugate base of HOCl, is extremely toxic to bacteria and plays a vital role in assisting the activated phagocytes with killing a wide range of pathogens.1

Excess production of HOCl in a living system can have a detrimental effect, as HOCl can react with many different biological molecules, including DNA, cholesterol and proteins, leading to changes in their biological properties. An example of this is the reaction of hypochlorous acid with unsaturated bonds in lipids, which produces a species called a chlorohydrin. This disrupts the formation of the essential lipid by-layers which form around cells.

Excess hypochlorous acid has been implicated in conditions such as inflammatory diseases, neurodegeneration and cancers.2 In order to fully understand the role of HOCl in these biological processes, accurate detection methods must be developed to monitor the molecule in living cells.

  Luminescent ruthenium complexes 

Several ‘HOCl-recognising’ molecules have been found to be effective sensors of hypochlorous acid. When conjugated with a fluorophore, these probes can successfully ‘recognise’ HOCl by reacting with it, however their application in vivo is still limited due to their excitation wavelengths being in the ultraviolet region of light.3 Sensors with adsorption (or emission) in the visible light range are more desirable for clinical diagnostic applications. 

In one recent paper in Dalton Transactions, Yuan and co-workers combine an excellent HOCl-recognising moiety: 4-amino-3-nitrol phenol) and a ruthenium(II)-2,2-bipyridyl complex, which is well known to exhibit visible light adsorption and emission, into one compound to create a luminescent probe for HOCl.

The resulting complex [Ru(bpy)2(AN-bpy)][PF6]2 is very weakly luminescent but, upon reaction with HOCl in aqueous media, converts to [Ru(bpy)2(HM-bpy)][PF6]2, which has a luminescence signal which is 110-fold stronger.

Impressively, the authors show that when HeLa cells are incubated with [Ru(bpy)2(AN-bpy)][PF6]2 for two hours they remain non-luminescent; when the same cells are subsequently treated with HOCl for thirty minutes, a bright red luminescence is observed, clearly demonstrating the potential for using this ruthenium complex as an in vivo, luminescent detector of hypochlorous acid. 

To find out more, read the article using the link below:

Development of a functional ruthenium(II) complex for probing hypochlorous acid in living cells
Dalton Trans. 2014, DOI:10.1039/C4DT00179F



Liana
Dr C. Liana Allen is currently a post-doctoral research associate in the group of Professor Scott Miller at Yale University, where she works on controlling the enantio- or regioselectivity of reactions using small peptide catalysts. Liana received her Ph.D. in organic chemistry at Bath University with Professor Jonathan Williams, where she worked on developing novel, efficient syntheses of amide bonds.


References  

 1 J. M. Albrich, C. A. McCarthy, J. K. Hurst, Prot. Nat. Acad. Sci., 1981, 78, 210.
2  T. I. Kim, S. Park, Y. Choi, Y. Kim, Chem.-Asian J., 2011, 6, 1358
3 Y. Xiao, R. Zhang, Z. Ye, Z. Dai, H. An, J. Yuan, Anal. Chem., 2012, 84, 10785.

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New MOFs Show Selective Carbon Dioxide Capture Capabilities

Carbon dioxide (CO2) is released into the Earth’s atmosphere in large quantities by fossil fuel and biomass-driven power generation and by natural gas processing plants. While the production of energy via these means is essential, the gaseous CO2 by-product they release into the atmosphere has been implicated in global warming and ocean acidification.1 The capture of waste gaseous CO2 and its subsequent long-term storage is one strategy being used to try to mitigate these geological problems.

Direct capture of CO2 from the air presents significant challenges, one of which is the separation of CO2 from other gases. Currently, a lot of waste carbon dioxide is captured at the emission source – fossil fuel-powered energy plants – by a ‘filter’ that traps the CO2 as it travels up a chimney. This method can prevent up to 90% of a power plant’s carbon emissions from entering the atmosphere, however the process requires a lot of energy and the captured gas still needs to be transported to a suitable storage area. New technologies for selective capture of carbon dioxide from the air are still in their infancy, but could offer more efficient ways to trap CO2 anywhere on the planet, not just at the sources of emission. 
MOF

Figure 1: Double chain MOF

Metal organic frameworks (MOFs), also known as coordination polymers, are compounds containing metal ions which are coordinated to organic molecules to form extensive two- or three-dimensional structures. The uniform and controllable porosity of these materials has already been exploited as potential devices for gas capture and storage.2 In one recent paper in Dalton Transactions, Kim and co-workers synthesise novel MOFs using cobalt and zinc metal ions coordinated to porphyrin-based molecules. The resulting MOFs display an interesting 1D ‘double chain’ arrangement of molecules (Figure 1). These ‘double chains’ pack together tightly, forming hydrogen bonds between the ‘chains’, resulting in a stable solid state structure with defined pores. Gas sorption experiments revealed that these new MOFs both show high uptake of CO2 gas compared with nitrogen (N2), hydrogen (H2) and methane (CH4), (Figure 2), making these types of materials excellent candidates for selective CO2 capture from the air. 

Gas uptake by double chain MOF

Figure 2: Gas uptake by double-chain MOF

Find out more and download the article now:
CO2 selective 1D double chain dipyridyl-porphyrin based porous coordination polymers 
Dalton Trans. 2014, DOI:10.1039/C3DT53287A 

References 

1 IPCC Special Report, ‘Carbon Dioxide Capture and Storage’, IPCC Working Group III, 2005
2 S. L. James, Chem. Soc. Rev., 2003, 32, 276.


Liana Allen Dr C. Liana Allen is currently a post-doctoral research associate in the group of Professor Scott Miller at Yale University, where she works on controlling the enantio- or regioselectivity of reactions using small peptide catalysts. Liana received her Ph.D. in organic chemistry at Bath University with Professor Jonathan Williams, where she worked on developing novel, efficient syntheses of amide bonds.
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Tag-Team Luminescence Enlightens Biomolecular Analysis

How do you combine rare-earth metals, extremely specific energy transfers, and luminescent properties to investigate changes in enzymes? New methods often arise from unique confluences of existing knowledge. In their recent paper, the Natrajan group from the University of Manchester exploit known properties of easily-obtained chemical products to present a clever new biosensory technique .

UCP emission spectra

The unique aspect is the use of upconverting phosphors (UCPs) in combination with enzymes. UCPs are luminescent particles, often based on rare-earth metals, which can be excited by multiple photons absorbed in the near-infra-red region (750-1400 nm wavelengths). Post excitation, they emit a photon of light in the higher-energy visible spectrum, thus the energetic process is known as up-conversion. While enzymes have high specificities and sensitivities to substrates, UCP’s have the advantage of excitation in the near-infra-red region without autofluorescence. In combination, enzymes and UCPs provide several direct advantages over simple biosensory fluorescence measurements.

In the current paper, NaYF4:Yb:Tm was the UCP used to probe the redox properties of the enzyme pentaerythritol tetranitrate reductase (PETNR) and Forster Resonance Energy Transfer (FRET), involving energy transfer between two chromophores, was used to excite the UCP. In this case, transfer of energy from the absorbance band of the flavin mononucleotide core of the PETNR enzyme and the emission band of the UCP, which are very close in wavelength, allow FRET to occur. Since a second emission band in the near-IR region originates from this UCP, this was normalized so that the other band, varying with the enzyme concentration, could be measured against it. When the PETNR underwent a two-electron reduction, it negated its ability to undergo FRET, resulting in the loss of the emission band at 460 nm, rendering the solution colourless. The researchers demonstrated that this new technique can be used with either the full PETNR enzyme or the mononucleotide flavin core alone, indicating that this can be applied to a wider range of systems.

Find out more and download the article now:
Ratiometric detection of enzyme turnover and flavin reduction using rare-earth upconverting phosphors
Dalton Trans., 2014, DOI: 10.1039/C4DT00356J


Ian_Mallow Ian Mallov is currently a Ph.D. student in Professor Doug Stephan’s group at the University of Toronto. His research is focused on synthesizing new Lewis-acidic compounds active in Frustrated Lewis Pair chemistry. He grew up in Truro, Nova Scotia and graduated from Dalhousie University and the University of Ottawa, and worked in chemical analysis in industry for three years before returning to grad school.
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Dalton Transactions Lectures at the University of California, Berkeley 2014

The 2013 Dalton Transactions Lecture awardees delivered their presentations at UC Berkeley last month. Each awardee is provided with an honorarium and a commemorative plaque. 

Trevor Hayton Professor Trevor Hayton (UCSB) gave the annual Dalton Transactions Lecture, which is awarded to an exceptional young inorganic chemist in the Americas each year. Previous recipients are:

2012   Teri Odom (Northwestern University)
2011    Daniel Gamelin (U Washington)
2010    Paul Chirik (Princeton University)
2009    Francois Gabbai (Texas A & M University)
2008    Dan Mindiola (Indiana University)
2007    Geoff Coates (Cornell University)
2006    John Hartwig (University of Illinois at Urbana-Champaign)
2005    Kit Cummins (MIT)

Professor Hayton has rapidly established himself as a leader in synthetic inorganic chemistry, focusing on actinides and bioinorganic systems. His lecture focused on the synthesis and reactivity of actinide complexes with chalcogenide ligands. 

Professor Hayton received his B.Sc. in Chemistry from the University of British Columbia, whereupon he began his Ph.D. research, also at UBC, under the direction of Peter Legzdins. After graduating in 2003, he began a postdoctoral fellowship at Los Alamos National Laboratory before joining the faculty at University of California, Santa Barbara in 2003.

   
Phillip Power The inaugural Dalton Transactions Distinguished Lecture was given on February 7 by Professor Phil Power of UC Davis. Professor Power is a world-renowned expert in main group chemistry. His Dalton Transactions Lecture focused on the preparation and structure of low-coordinate main group compounds and their reactivity towards small molecules such as dihydrogen and ethene. 

Professor Power received his bachelor’s degree in chemistry from the University of Dublin, Ireland, and his doctorate from the University of Sussex; the latter under the supervision of Mike Lappert. He carried out postdoctoral research at Stanford University before joining the faculty at UC Davis in 1980. He was award the Royal Society of Chemistry Mond Medal in 2005 and elected Fellow of the Royal Society in the same year. 

 Congratulations to Professors Hayton and Power for their awards!

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Could cobalt have a role in renewable energy storage?

Posted on behalf of Ian Mallov, web writer for Dalton Transactions

The water oxidation reaction is one of the most fundamental in chemistry and likely to be one of the first students are introduced to. During the reaction, water and energy are combined to give oxygen gas, protons and electrons, with the latter used to reduce the protons and yield hydrogen gas. The storage of hydrogen gas is one proposed method of storing the energy generated from renewable sources as, by burning the hydrogen and regenerating water in the process, you can release and harness the energy as needed.

In order for the water oxidation cycle to result in a net energy gain, a catalyst is needed for the oxidation process, with the majority of current systems incorporating rare or expensive metals. In their recent Dalton Transactions article, Johnsson and co-workers used small, cluster compounds made of cobalt, selenium, oxygen and chlorine to catalyze water oxidation. Two of the compounds, Co4(SeO3)3Cl2 and Co3Se4O10Cl2, were previously unreported but are closely related to the third, known compound Co5Se4O12Cl2. To synthesise the molecules, the authors heated mixtures of CoO, SeO2, and CoCl2 to 550 °C in a furnace for a number of days, with different ratios of the starting materials used to produce the different compounds. Adding each compounds to a solution of phosphate buffer and Ru(bpy)3(PF6)3 led to the evolution of oxygen gas, which, by further 18O labelling experiments, was confirmed to occur due to water oxidation. 

Co_catalyst_activities

Catalytic oxygen evolution by cobalt catalysts

Analysis of a catalyst intended to facilitate sustainable energy storage should spur discussion of the environmental impact of making the catalyst.  The large energy input to heat the materials is a drawback.  But, if synthesized in good yield in solid-state (solventless) reactions, as done here, the reactions would score well on the E-factor scale, a metric measuring waste produced per mass of product that gives a more complete indication of material efficiency than the obsolete atom economy principle. 

Though the catalytic activity proved wanting, the simple compounds and syntheses here present an interesting strategy towards useful water oxidation catalysis. 

Find out more and download the article now:
Cobalt selenium oxohalides: Catalysts for Water Oxidation
Dalton Trans., 2013, DOI: 10.1039/C3DT53452A


Ian_MallowIan Mallov is currently a Ph.D. student in Professor Doug Stephan’s group at the University of Toronto. His research is focused on synthesizing new Lewis-acidic compounds active in Frustrated Lewis Pair chemistry. He grew up in Truro, Nova Scotia and graduated from Dalhousie University and the University of Ottawa, and worked in chemical analysis in industry for three years before returning to grad school.

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Ruthenium fights the resistance

Bacterial resistance to standard types of antibiotics is a growing problem in medical science. The most famous example is MRSA, which stands for Methicillin-resistant Staphylococcus aureus. This name refers to a bacterium which, through the process of natural selection, is now resistant to a class of antibiotics called beta-lactams (which include penicillin and the cephalosporins). MRSA is especially dangerous in environments like hospitals and nursing homes, where patients or residents with weakened immune systems are at greater risk of infection (compared with the general public). The Office for National Statistics reports that between 1993 and 2005, the number of deaths associated with MRSA rose from 51 to 1,652.1

Methods to try and fight this growing threat include increased sanitization of areas where people are most at risk of infection and screening patients for the bacteria upon hospital admission and separating carriers from non-carriers. In the scientific community, development of new compounds which are capable of killing MRSA and other antibiotic resistant bacteria is a highly important, ongoing research area.2

Metal complexes displaying biological activity have been widely reported; in particular complexes containing the metal ruthenium have been shown to display anti-cancer, anti-microbial and DNA binding abilities.3 In this paper, the authors synthesise several new ruthenium complexes and perform tests to assess their anti-microbial activity against MRSA.

Structure of ruthenium complexes synthesized and ‘zone of clearance’ assay results.

Structure of ruthenium complexes synthesized

A ‘zone of clearance’ study pitted two of the new ruthenium complexes against methicillin in a test of how effectively each compound inhibited bacterial growth (see below). The ruthenium complexes were shown to have superior anti-MRSA activity when compared with methicillin, suggesting they could provide prolonged antibacterial activity when used as topical antibiotics.

Structure of ruthenium complexes synthesized and ‘zone of clearance’ assay results.

‘Zone of clearance’ assay results

To read more, download the article now:
“Development of ruthenium(II) complexes as topical antibiotics against methicillin resistant Staphylococcus aureus
W.-Y. Wong et al., Dalton Trans. 2014, DOI:10.1039/C3DT52879K

References:

1 UK Office for National Statistics, www.ons.gov.uk
2 P. A. Ashford, S. P. Bew, Chem. Soc. Rev., 2012, 41, 957
3 C. S. Allardyce, P. J. Dyson, Platinum Metals Rev., 2001, 45, 62


Liana Allen Dr C. Liana Allen is currently a post-doctoral research associate in the group of Professor Scott Miller at Yale University, where she works on controlling the enantio- or regioselectivity of reactions using small peptide catalysts. Liana received her Ph.D. in organic chemistry at Bath University with Professor Jonathan Williams, where she worked on developing novel, efficient syntheses of amide bonds.
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Dalton Transactions: at the heart of the inorganic community

Posted on behalf of Jamie Humphrey, Editor

Our number one priority at Dalton Transactions is to ensure that the journal continues to support our community by providing excellent services for authors and by publishing only the best inorganic chemistry research. We strive to develop and innovate to make sure that the journal continues to serve the international inorganic community. This is very much at the heart of everything we do.

The truly international nature of the journal is represented not only in our authorship (we published articles from 70 countries in 2012), but also through the Editorial Board membership, including our team of Associate Editors – about half of the papers submitted to the journal are handled by this team, with the rest handled by the team of Editors based in Cambridge. Our Associate Editors span the globe, with editorial offices in the USA, UK, Germany, China and Japan. The Royal Society of Chemistry has also been developing its international staff presence in recent years and we now have editorial staff based in Japan, China and the USA, in addition to Royal Society of Chemistry offices in India, Africa and, more recently, Brazil.

In today’s information age, where we can sometimes feel overwhelmed with the amount of information that is available, access to reliable trustworthy knowledge has never been more important. At Dalton Transactions, our fair and impartial peer-review means the content we publish is always of the highest possible quality. Ensuring your research gets the right audience is also key. We have therefore introduced initiatives to lead to greater discoverability for articles published in the journal, and to develop additional measures of an article’s impact.

Dalton Transactions is part of a pilot programme between the Royal Society of Chemistry and Kudos, which aims to provide tools and services to help researchers maximise the usage and impact of their articles. The need for Kudos arises from developments in global academic and research policies that see evolving measures of ‘impact’ used to assess excellence. Kudos aims to provide a service to help researchers and their institutions measure, monitor and maximize the usage of and citations to their articles. The Royal Society of Chemistry also recently introduced a new system for monitoring article-level metrics in Dalton Transactions. The service collates online “mentions” of scholarly articles from social media, newspapers, blogs and other sources into a report that appears online with the article to showcase its uptake, visibility and societal impact. Article-level metrics represents a shift from measuring the impact of a journal to the impact of an article.

Supporting the community is at the heart of Dalton Transactions and is also at the core of the Royal Society of Chemistry, the world’s leading chemistry community. One way in which we supported chemists across the globe is through the funding of the International Year of Chemistry legacy grants. In 2012, over 60 of our member groups received grants each of £1000 to arrange events and activities to promote the chemical sciences. These had an international nature, and ranged from workshops for migrant children in Beijing and a science fair on water chemistry in southern India to supporting chemistry education in tsunami-affected areas in Sri Lanka. Learn more about these grants via www.rsc.org/scienceandtechnology/funding/iyclegacygrants.asp

Dalton Transactions continues to publish research from all areas of inorganic, organometallic and bioinorganic chemistry. Our Themed Issues bring together the best articles in topical research areas or highlight emerging subjects. Table 1 gives full details of the Themed Issues published in 2013.

Table 1 Dalton Transactions Themed Issues published in 2013


Theme Guest Editor(s)  
Coordination Programming: Science of Molecular Superstructures towards Chemical Devices Hiroshi Nishihara (Tsukuba University, Japan) and Hiroki Oshio (University of Tokyo, Japan)  
 
Molecular Precursors for Precision Synthesis of Nanomaterials Christophe Copéret and Maksym Kovalenko, ETH, Switzerland  
 
Vanadium in Inorganic Chemistry Debbie Crans, Colorado State University, USA and Craig McLauchlan, Illinois State University, USA  
 
Advances in Metal-Catalysed Polymerisation and Related Transformations Philip Mountford, University of Oxford, UK  
 
N-Heterocyclic Carbenes Catherine Cazin, St. Andrew’s University, UK  
 
Chemistry and Applications of Metal Complexes Maria Amélia Santos, University of Lisbon, Portugal  
 
Mechanistic Organometallic Chemistry Robert Crabtree, Yale University, USA  
 
Bioinorganic Chemistry Emma Raven, Leicester University, UK  
 
Boranes and Borohydrides Simon Aldridge, University of Oxford, UK  

Themed Issues planned for 2014 include Carboranes (Guest Editors: Professor Guo-Xin Jin, Fudan University, China and Professor Zuowei Xie, The Chinese University of Hong Kong, Hong Kong), Inorganic Chemistry for Renewable Energy Conversion and Storage (Guest Editor, Professor Lars Kloo, KTH, Sweden), Layered Inorganic Solids (Guest Editors: Professor Russell Morris, University of St. Andrews, UK, Dr Jiri Cejka, J. Heyrovsky Institute of Physical Chemistry, Hungary, Dr Petr Nachtigall, Charles University, Czech Republic, Dr Wieslaw Roth, Jagiellonian University of Krakow, Poland), New Talent: Europe (Guest Editors, Professor Dr Matthias Tamm, Technische Universität Braunschweig, Germany and Dr Marc D. Walter, Technische Universität Braunschweig, Germany), Organometallic and Coordination Derivatives of Nanocarbons (Guest Editors, Professor Andrei Khlobystov, University of Nottingham, UK and Professor Andreas Hirsch, University Erlangen-Nuremberg, Germany), New Expeditions in Polar Organometallic Chemistry (Guest Editor, Professor Eva Hevia, University of Strathclyde, UK), Spectroscopy of Inorganic Excited States (Guest Editor, Dr Julia Weinstein, University of Sheffield, UK) and Synergy between Experiment and Theory (Guest Editor, Professor Eric Clot, University of Montpellier, France).

2014 will be a busy year for inorganic chemistry conferences, and I hope that you will look out for me or Deputy Editor Fiona McKenzie – we would love to meet up with you! Two such meetings are the Dalton Discussions, which will take place in the UK. We are proud to publish the presented papers in Dalton Transactions. The titles of the 2014 meetings are ‘Advancing the Chemistry of the f-elements: Dalton Discussion 14’ (28–30 July 2014 Edinburgh, UK) and ‘Metal ions in medical imaging: optical, radiopharmaceutical and MRI contrast: Dalton Discussion 15’ (8–10 September 2014, York, UK). Another important inorganic meeting organised by the Royal Society of Chemistry in 2014 is the 13th ISACS meeting (Challenges in Inorganic and Materials Chemistry (ISACS13)) which will take place in Dublin, Ireland, 1–4 July 2014. To discover which conferences the Editorial Team will be attending in 2014, follow us on twitter (@DaltonTrans and @humphreyj).

We were pleased to support a number of international conferences in 2013 through sponsorship – you may even have attended one of our sponsored lectures. We give support to younger members of the community via poster prizes, and in 2013 we awarded 22 poster prizes, celebrating the achievements of members of our community in the early years of their academic careers. If you are organising a conference in 2014 and you would like us to sponsor a poster prize, please let us know.

With a thriving worldwide network, and a not-for-profit ethos, the Royal Society of Chemistry is the best place to publish work that advances excellence in the chemical sciences. Publish with Dalton Transactions and you’ll be supporting the wider scientific community and future generations of chemists and chemical scientists.

Have a fantastic 2014!

Download the PDF here

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Dalton Transactions now features Altmetrics

We are pleased to announce the inclusion of Altmetrics on Dalton Transactions.

With a constantly changing publishing landscape and changes to the way people use scientific literature, altmetrics is a measure that can monitor the level of conversation and interest in a particular piece of research at the article level. Thus altmetrics provides an additional modern metric for our authors to measure the impact of their work, rather than rely solely on citations and impact factor.

To view the altmetrics on Dalton Transactions articles, use the Metrics tab as pictured below on the article landing page.

Altmetrics on Dalton Transactions

A press release from Altmetrics is available on our website.

What do you think? We are interested to hear your feedback on this new development and how you are utilising these new types of metrics. Please leave your comments below.

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Why Some Silylenes Split Hydrogen and Others Don’t

Posted on behalf of Ian Mallov, web writer for Dalton Transactions

We often invoke the analogy of using building blocks when we talk about constructing large, complex molecules.  Adding small building blocks often allows for finer control in design, and diatomic hydrogen is the most used small building block.

To add hydrogen to other molecules, hydrogen molecules themselves are split into a proton and hydride; these are then transferred to the target molecule.  Recently, main group compounds involving frustrated Lewis pairs have been used in both steps instead of transition metal catalysts.  There are also a few main group molecules where hydrogen is split at a single atomic site.  Silylenes – the silicon analogue of carbenes, and the subject of this paper, with two bonds, a pair of electrons, and an empty p-orbital, are one type of these select few. This paper mentions the argument that non-transition metal catalysts may be “greener,” but a thorough life-cycle analysis of extraction, reaction and disposal would be necessary to indicate this. 

Authors, Kuriakose and Vanka use Density Functional Theory to explore the question of why some silylenes split hydrogen and some don’t.  Specifically, they want to test the hypothesis that whether or not hydrogen is split at the silicon centre depends on if an adjacent atom “interferes,” leading to undesired products.  They create a profile of the energies of reaction (with hydrogen gas) of three distinct types of silylene: a boryl amido silylene (I), a silyl amido silylene (II) and a dithiolate silylene (III).  I and II have activated hydrogen, while III hasn’t been observed to do so. 

 

The free energy profiles for the reaction of silylene, III, with hydrogen  

After optimizing geometry they model the HOMO and LUMO of the silylenes, since donation of electrons from the HOMO and acceptance of electrons into the LUMO are necessary for hydrogen activation.  In the case of I and II, the LUMO is localized on the silicon atom, while in III, it is not. Correspondingly, the reaction pathway of splitting hydrogen is energetically favoured for I and II, and disfavoured for III.  They also examine effects of other features, such as the angle of the two substituents. 

Have a read of the full article now:

New insights into small molecule activation by acyclic silylenes: a computational investigation
Nishamol Kuriakose and Kumar Vanka
Dalton Transactions, DOI: 10.1039/c3dt52817k


Ian Mallov is currently a Ph.D. student in Professor Doug Stephan’s group at the University of Toronto. His research is focused on synthesizing new Lewis-acidic compounds active in Frustrated Lewis Pair chemistry. He grew up in Truro, Nova Scotia and graduated from Dalhousie University and the University of Ottawa, and worked in chemical analysis in industry for three years before returning to grad school.

 

  

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It’s Getting Easier to be Green

Posted on behalf of Liana Allen, web writer for Dalton Transactions

As more information becomes known about the negative impacts that humans are having on the Earth’s environment, increasing focus is being put on ways of decreasing these effects in all aspects of our lives. For the chemical industry, there are already several key areas which have been identified as needing particular attention with respect to decreasing our effect on the environment. In the last decade, this challenge has become so important that it is now recognized as a field in its own right, referred to as ‘Green Chemistry’. Some of the overall themes of green chemistry are: decrease of the amount of waste by-products generated by a reaction (i.e. avoiding poor atom economy reagents), reduction of reagents which pose safety hazards (i.e. explosives and known toxic compounds), and ‘cleaner’ solvent choices (i.e. avoiding chlorinated solvents, or volatile solvents whose vapours pose an environmental problem).1

One of the most important reactions used in chemical industry is formation of carbon-carbon bonds.2 The methodology most commonly used to form such bonds is a group of reactions called palladium-catalysed cross-couplings. One of this set of vital reactions is called the Sonogashira coupling. This reaction is used to couple terminal alkynes with aryl or vinyl halides to form di-substituted alkynes, and requires a copper co-catalyst (in addition to a palladium catalyst), heating conditions, and a solvent such as DMF.

In their recent Dalton Transactions article, Wang and colleagues take significant steps towards applying the principles of green chemistry to the Sonogashira reaction by optimizing new conditions where; (a) a copper co-catalyst is not required, thus increasing the atom efficiency of the reaction, (b) the reaction can be run at room temperature, eradicating the energy cost normally required for heating and (c) the solvent is readily available and environmentally benign water.

To read more, see:

Copper-free Sonogashira Cross-Coupling Reaction Promoted by Palladium complexes of Nitrogen-containing Chelating Ligand in Neat Water at Room Temperature
Hong Zhong, Jinyun Wang, Liuyi Li and Ruiha Wang, Dalton Trans. 2013, DOI:10.1039/C3DT52970C

References
1 Constable, D. J. C. et al., Green Chem., 2007, 9, 411.
2 Carey, J. S. et al., Org. Biomol. Chem., 2006, 4, 2337.

Liana AllenDr C. Liana Allen is currently a post-doctoral research associate in the group of Professor Scott Miller at Yale University, where she works on controlling the enantio- or regioselectivity of reactions using small peptide catalysts. Liana received her Ph.D. in organic chemistry at Bath University with Professor Jonathan Williams, where she worked on developing novel, efficient syntheses of amide bonds.

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