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Archive for the ‘Inorganic’ Category

The first hydroamination reaction with a zincocene complex

20 Jul 2011

Peter Roesky, Siegfried Blechert and co-workers at the Karlsruhe Institute of Technology and the Berlin University of Technology have reported the first use of a dizinc complex as the catalyst in a hydroamination reaction.

Hydroamination is the addition of an N–H bond of an amine to an unsaturated C–C bond to give a molecule that contains nitrogen in one step. This is particularly important because many current amine syntheses are multi-step processes. Zinc complexes are advantageous for hydroamination as they are relatively cheap, air and moisture stable and tolerant to a wide variety of functional groups.

With this in mind Roesky and Blechert decided to test the zincocene complex, Zn₂(η⁵-C₅Me₅)₂, for its hydroamination activity. This complex was discovered in 2004 but it is the first time that it has been used as a catalyst. The team found that the catalyst worked well with good yields and conversions and that it tolerates many functional groups.

Want to find out more? Then download the ChemComm article for free today and leave a comment below.

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Probing cells’ power generators

07 Jun 2011

UK scientists have developed a probe to monitor bicarbonate concentrations in mitochondria – components in living cells that generate chemical energy. Monitoring bicarbonate levels will improve researchers’ understanding of its role in cellular reaction mechanisms.

A challenge when designing cellular probes is ensuring that the probe is not only selective for its target but can also be delivered to the site of interest within the cell. A team of scientists led by David Parker at the University of Durham has made a probe that can overcome this challenge.

Stained HeLa cells The luminescent probe features an azaxanthone moiety, which is linked to a europium complex by an amide bond. The azaxanthone allows the probe’s uptake into cells and localisation within the mitochondria, and the europium complex has an affinity for bicarbonate ions. The ability to probe bicarbonate levels ‘can offer an unprecedented insight into signalling mechanisms’, says Parker.

Read the rest of this story in Chemistry World and download Professor Parker’s ChemComm communication, which is free to access for a limited period.

Also of interest:
Definition of the uptake mechanism and sub-cellular localisation profile of emissive lanthanide complexes as cellular optical probes
Elizabeth J. New, Aileen Congreve and David Parker, Chem. Sci., 2010, 1, 111-118

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New acetylene polymerisation catalyst is best yet

03 Jun 2011

A team of chemists working in the UK and Australia have developed a new, highly active catalyst for acetylene polymerisation.

Polyacetylene is an important material as it has a degree of conjugation that leads to good conductive properties. It has found uses in areas such as synthetic metals and plastic electronics. New routes to make this polymer are constantly sought and, to date, the majority of catalysts for this task have low activities.

This problem has now been solved by two teams at the University of Tasmania and Imperial College London led by David McGuinness and George Britovsek, respectively. They took a bis(imino)pyridine iron catalyst, normally used for ethylene polymerisation, along with methylaluminoxane and successfully produced polyacetylene.

Graphical abstract: High activity acetylene polymerisation with a bis(imino)pyridine iron(ii) catalyst

An activity of 62 500 h^-1 (turn over frequency; TOF) was obtained, which compares excellently with the 100 h^-1TOF obtained when using a standard existing acetylene polymerisation catalyst under the same conditions. This represents the most active acetylene polymerisation reported to date. Curently, the team are studying the effects of ligand modification and chain transfer reagents on the reaction.

Want to find out more? Then download the full ChemComm article for free today.

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To expand or not to expand?

09 May 2011

Two dumbbell-shaped polymorphs possess similar packing arrangements, but one shows anomalously anisotropic thermal expansion while the other does not.

Leonard J. Barbour and his team from the University of Stellenbosch, in South Africa and a co-worker from the Polish Academy of Sciences, have investigated these polymorphs further and discovered that by adjusting the molecular stacking angle by approximately 10° effectively disables the molecules’ ability to undergo thermal expansion.

Fancy expanding your knowledge? Then why not download the ChemComm communication today and read all about the teams research results? This article is free to access until Friday 3rd June.

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Call for communications: Artificial Photosynthesis

06 May 2011

We are delighted to announce a forthcoming web themed issue:

Artificial Photosynthesis

Guest editor: Andrew Benniston (Newcastle University)

Submission deadline: 15th August 2011 EXTENDED TO 30TH SEPTEMBER!!

We are now welcoming submissions for this web theme, which will be a celebration of current achievements and future perspectives in this exciting field of research. Communications covering all aspects of the following areas are encouraged:

new materials and photocatalysts for solar photochemistry
hydrogen production and water splitting
nitrogen and carbon dioxide functionalisation
light harvesting and energy transfer
electron transfer (tunnelling vs hopping)
coupled proton/electron transfer
long-range electron transport
multi-electron redox processes
bioinspired molecular systems
nanostructures for solar energy usage

All manuscripts will undergo strict peer review and should be very important and conceptually significant in accord with the ChemComm mandate.

Publication of the peer-reviewed articles will occur without delay to ensure the timely dissemination of the work. The articles will then be assembled on the ChemComm website as a web-based thematic issue, to permit readers to consult and download individual contributions from the entire series.

Communications for this web theme can be submitted anytime from now until 30th September using our web submission system. Please add the phrase ‘artifical photosynthesis’ in the comments to the editor field.

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New tool for speeding up porous materials discovery

28 Mar 2011

A new tool (Infrasorb-12) for screening porosity has been developed by scientists in Germany. The tool identifies high surface area materials in a very short time with high accuracy. The researchers say that Infrasorb-12 development will speed up the discovery of new porous materials significantly and broaden the wide range of materials suitable for gas storage, selective adsorption, catalysis, and life science applications.

Further information:
High-throughput screening: speeding up porous materials discovery
Philipp Wollmann, Matthias Leistner, Ulrich Stoeck, Ronny Grünker, Kristina Gedrich, Nicole Klein, Oliver Throl, Wulf Grählert, Irena Senkovska, Frieder Dreisbach and Stefan Kaskel, Chem. Commun., 2011, DOI: 10.1039/C1CC10674K

Also of interest:
Modifying MOFs: new chemistry, new materials
Seth M. Cohen, Chem. Sci., 2010, 1, 32-36 (DOI: 10.1039/C0SC00127A)

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Carbon dioxide adsorption in porous phosphine coordination material

28 Mar 2011

US, UK and Korean scientists have made a new porous phosphine coordination material, PCM-11. The material is an unusual 8,4-connected coordination polymer with an open 3-D pore structure, say the researchers.

The team formed the material by reacting Mg(II) with tris(para-carboxylato)triphenylphosphine oxide. The highly ionic nature of the metal–ligand bonding results in excellent thermal stability upon desolvation (>460 ºC), they say. PCM-11 is easily activated for small molecule sorption at low temperature without the requirement for solvent pre-exchange. It adsorbs 47.5 wt% CO₂ at 11.6 bar and 30ºC.

Find out more in the ChemComm communication:
High capacity CO₂ adsorption in a Mg(II)-based phosphine oxide coordination material
Alisha M. Bohnsack, Ilich A. Ibarra, Peter W. Hatfield, Ji Woong Yoon, Young Kyu Hwang, Jong-San Chang and Simon M. Humphrey, Chem. Commun., 2011, DOI: 10.1039/C1CC10754B

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Nanoflowers for protein immobilisation and separation

15 Feb 2011

It is the quest of many a materials scientist to form core-shell nanostructures by self-assembly, in order to generate materials with unique structures and functions. In this area, hierarchical nanoarchitectures assembled from nanoscale units have recently stimulated tremendous interest because these superstructures might avoid aggregation and maintain high specific surface areas. In addition, magnetic materials have received considerable interest, due to their ability to selectively capture target objects from complex mixtures.

Ken Cham-Fai Leung and colleagues – based in Hong Kong and Hefei, China – have reported a facile synthesis of monodispersed microparticles composed of superparamagnetic Fe₃O₄ cores, a SiO₂ shell and a hierarchical g-AlOOH periphery with Au nanoparticles, obtaining nanoflower structures resembling daisies. As proof of principle for their use as selective protein capturing agents, these nanoflowers were applied as absorbents to successfully remove bovine serum albumin from bovine blood.

To find out more download the ChemComm communication, which is free to access until 15th March 2011.

Start a discussion about this research by leaving comments below.

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Proof-of-principle concept for label-free detection of glucose and alpha-glucosidase activity

28 Jan 2011

Glycogen storage disease type II (GSD II), also known as Pompe disease, is a genetic disorder that results in muscle and nerve cell damage caused by deficiency of the lysosomal acid a-glucosidase enzyme. In an effort to achieve a better technique for screening enzyme activity in patients suffering from Pompe disease, Prof. Vivian Yam and colleagues at the Institute of Molecular Functional Materials, University of Hong Kong, have synthesised a two-component platinum (II) complex-polymer ensemble for glucose sensing and a-glucosidase assay.

The system works by strongly binding glucose, resulting in a 46-fold increase in the low energy emission band (800 nm) of the electronic emission spectrum. Additionally, in the presence of a-glucosidase and maltose (which is broken down to glucose by a-glucosidase), the intensity of the 800 nm emission band was found to increase with time. These results provide a “proof-of-principle” concept for label-free detection of glucose and open the way for rapid and sensitive detection of a-glucosidase.

To find out more download the ChemComm communication for free until 25th February 2011.

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Lack of luminescence quenching does not prove DNA intercalation by Ru(II) complexes

21 Jan 2011

The binding of luminescent complexes to DNA is a popular area of research, with applications ranging from molecular switches to photodynamic therapy. It has commonly been reported in the literature that a lack of luminescence quenching by ferrocyanide, [Fe(CN)₆]⁴⁻, can be used as evidence of the intercalation of a complex with DNA.

Claudia Turro and colleagues at Ohio State University have now shown that a Ru(II) complex that binds strongly to DNA electrostatically rather than by intercalation is equally resistant to ³MLCT (metal-to-ligand charge transfer) emission quenching as one known to be a DNA intercalator.

These findings indicate that the absence of emission quenching by [Fe(CN)₆]⁴⁻cannot be used alone as proof of DNA intercalation by a complex. Hence, researchers using this method will need to take extra care when interpreting their results.

To find out more and start a discussion download the communication (for free until 18th Feb 2011) and leave your comments below.

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