Chemical Communications Blog

Liquid crystal relaxation controlled by dopant kinetics

20 Jan 2013

Liquid crystals are an area of intense interest due to their potential use in smart materials such as displays. Cholesteric liquid crystals are of particular interest due to their helical nature and their ability to selectively reflect light over a narrow range of wavelengths. This range can be modified by the inclusion of photo-responsive dopants.

Dopants include overcrowded alkenes which undergo a stable to unstable (cis–trans) transition upon irradiation with UV light. This results in an unwinding and eventual inversion of the cholesteric helix. This is accompanied by a red-shift of the reflection band which then returns close to the original position. However, the handedness of the helix has changed, and therefore the polarization of the light has also changed.

Helix inversion of a cholesteric liquid crystal.

An important parameter with all liquid crystals is their relaxation step which needs to be suitable for the envisioned application. Nathalie Katsonis and her team have studied cholesteric liquid crystals doped with overcrowded alkenes in an effort to find a general paradigm correlating relaxation kinetics with the rate of helix inversion.

In their recent Communication, Katsonis’ group shows that the helix relaxation kinetics are fully determined by the kinetics of the light-sensitive dopants. The relaxation of the dopants from unstable to stable is unperturbed by the liquid crystalline environment.

On the other hand, the presence of the dopants can dramatically accelerate helix inversion. Therefore the inversion can be time-programmed by judicious choice of the dopant. This opens up the great potential of fine tuning cholesteric liquid crystals for smart materials with sophisticated functions.

For more, read this ‘HOT’ Chem Comm article in full:

Time-programmed helix inversion in phototunable liquid crystals

Sarah J. Aßhoff, Supitchaya Iamsaard, Alessandro Bosco, Jeroen J. L. M. Cornelissen, Ben L. Feringa and Nathalie Katsonis

Chem. Commun., 2013, Advance Article

DOI: 10.1039/C2CC37161H

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True racemic crystals: Surprising new insights on preparation and structure

16 Jan 2013

By Ruth E. Gilligan.

Isopropyl 3,3,3-trifluoro-2-hydroxypropanoate (1) is an important compound for the study of self-disproportionation of enantiomers (SDE), in which an enantiomerically enriched mixture can be separated into enantiopure and racemic portions under achiral conditions. This remarkable separation is made possible by the differences in physicochemical properties of enantiopure and racemic substances. Research led by Professor Vadim A. Soloshonok at the University of the Basque Country has now shed light on the unusual properties of racemic crystals of 1.

True racemic crystals were obtained by sublimation of a mixture of (S)- and (R)- crystal conglomerates at ambient temperature and atmospheric pressure. Surprisingly, when these racemic crystals were analysed, the unit cell was not dimeric in nature as previously thought, but rather contained two distinct (S)- and (R)- enantiomers with no heterochiral H-bonding. The preference of 1 for homochiral intermolecular interactions may explain its extraordinary ability for SDE. Indeed, Soloshonok and co-workers showed that achiral chromatography could be used to obtain enantiopure 1 from an original sample with just 75% ee (see above).

For more, read this ‘HOT’ Chem Comm article today:

Unconventional preparation of racemic crystals of isopropyl 3,3,3-trifluoro-2-hydroxypropanoate and their unusual crystallographic structure: the ultimate preference for homochiral intermolecular interactions

José Luis Aceña, Alexander E. Sorochinsky, Toshimasa Katagiri and Vadim A. Soloshonok

Chem. Commun., 2013, 49, 373–375

DOI: 10.1039/c2cc37491a

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A new way to look at cancer cell detection

14 Jan 2013

By Jane Hordern, Deputy Editor.

Cancer cell detection based on the interaction between an anticancer drug and cell membrane components

A novel cancer cell detection method, based on the interaction between daunomycin (DAN – an anticancer drug used in chemotherapy) and cell membrane components, has been developed by scientists in South Korea.

The method uses the electrochemical and fluorescence behaviour of DAN and uses an aptamer probe immobilised on a conducting polymer-gold nanoparticle composite film.

he aptamer sensor probes using electrochemical impedance spectroscopy and fluorescence microscopy. The method differentiates between cancerous and non-cancerous cells at low concentrations (0.01μM).

Read the ‘HOT’ Communication in full:

Cancer cell detection based on the interaction between an anticancer drug and cell membrane components
Pranjal Chandra , Hui-Bog Noh and Yoon-Bo Shim
Chem. Commun., 2013, DOI: 10.1039/C2CC38235K

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Early Alzheimer’s diagnosis compound

20 Dec 2012

By Jane Hordern, Deputy Editor.

Alzheimer’s disease is the most common form of dementia and, as there is no cure, early diagnosis is crucial for treatment to be effective. To this end, UK and US scientists have developed a labelled tracer compound that binds to plaques closely associated with Alzheimer’s disease (AD) so that the plaques can be picked up by a medical imaging technique.

The tracer compound is a [¹⁸F]-labelled barbiturate and is used with the imaging technique positron emission tomography (PET). Although other radiolabelled compounds have been used as PET tracers, using [¹⁸F]-labelled barbiturates for molecular imaging in AD has distinct advantages, such as good blood-brain barrier crossing ability, metabolic stability and easy accessibility.

Tree that looks like a face with some leaves blowing away to represent memory loss in Alzheimer's disease As Alzheimer’s disease advances, symptoms can include confusion, irritability and aggression, and long-term memory loss © Shutterstock

Matteo Zanda at the University of Aberdeen and colleagues, in conjunction with Pfizer in the US, developed several fluorinated barbiturate analogues. The key to developing an effective molecular imaging radiotracer is the ability to distinguish between a healthy individual and someone suffering from a neurological disease, such as AD, they say. Barbiturates have a strong capacity for forming structures with biopolymers and are effective metal ion chelators. As such, the team thought that they would bind to AD-related plaques, which consist of the biopolymer β-amyloid and metal cations, such as Zn(II) and Cu(II).

See the Chemistry World story in full or read the Chem Comm article:

18 F-barbiturates are PET tracers with diagnostic potential in Alzheimer’s disease
Elisa Calamai , Sergio Dall’Angelo , David Koss , Juozas Domarkas , Timothy J. McCarthy , Marco Mingarelli , Gernot Riedel , Lutz F. Schweiger , Andy Welch , Bettina Platt and Matteo Zanda
Chem. Commun., 2013,49, 792-794
DOI: 10.1039/C2CC38443D

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Probing assembly of supramolecular architectures with non-linear optics

05 Dec 2012

By Cally Haynes.

Molecules containing urea and thiourea groups are well known in supramolecular chemistry to self assemble into chains via hydrogen bonding interactions, which can be broken by interaction with ions or polar molecules.

Pritam Mukhopadhyay’s group in New Delhi have found that, with the right functionalization, this can lead to interesting optical properties in solution.

Molecules such as 1a and 1b were found to have non-linear optical (NLO) behaviour in THF solution. On adding a polar molecule such as methanol, or a strongly coordinating anion such as acetate, the NLO behaviour was reduced. This corresponds to the self-assembled urea chains being disrupted by adding a guest that can compete for hydrogen bonding to the urea NH groups.

With this work, the authors have identified an effective new method to probe the assembly and disassembly of supramolecular architectures.

For more information, you can download the full article (free for a limited time) here.

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ChemComm Emerging Investigator Lectureship: Nomination Deadline Friday 7 December

04 Dec 2012

By Jane Hordern, Deputy Editor.

We are delighted to invite nominations for ChemComm Emerging Investigator Lectureship 2013. The lectureship, which is awarded annually, will recognise an emerging scientist in the early stages of their independent academic career.

Deadline for Nominations: 7 December 2012
Nominate now

To qualify
To be eligible for the ChemComm Emerging Investigator Lectureship, the candidate should have completed their PhD on or after 5th September 2004.

The candidate should also have published at least one article in ChemComm during the course of their independent career.

Award details
The recipient of the award will be invited to present a lecture at three different locations over a 12 month period. It is expected that at least one of the locations will be a conference. The recipient will receive a contribution of £1500 towards travel and accommodation costs. S/he will also be presented with a certificate and be asked to contribute a ChemComm Feature Article.

Nominations
Those wishing to make a nomination should send the following details to the ChemComm Editorial Office by 7th December 2012:

Recommendation letter, including the name, contact details and website URL of the nominee.
A one page CV for the nominee, including their date of birth, summary of education and career, list of up to five independent publications, total numbers of publications and patents and other indicators of esteem and evidence of independence.
A copy of the candidate’s best publication to date (as judged by the nominator).
Two supporting letters of recommendation from two independent referees. These should not be someone from the same institution or the candidate’s post doc or PhD supervisor.

The nominator and independent referees are requested to comment on the candidate’s presenting skills.

Please note that self nomination is not permitted.

Selection procedure
The ChemComm Editorial Board will draw up a short-list of candidates based on the information provided by the referees and nominator. Short-listed candidates will be asked to provide a supporting statement justifying why they deserve the award. The recipient of the award will then be selected and endorsed by the ChemComm Editorial Board.

Previous winners

	2012 Professor Hiromitsu Maeda (Ritsumeikan University, Japan) – he’ll be presented with his lecture certificate at ICPOC 21.
	2011 Dr Scott Dalgarno (Heriot-Watt University, Edinburgh, UK) – Find out about his Emerging Investigator Lecture tour in China.

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Nanoconfinement leads to increased catalytic stability

29 Nov 2012

By Katie Renouf, Web Writer.

Steam reforming, where hydrogen gas is produced from hydrocarbon fuels such as natural gas, is an important industrial catalytic process. Nickel is the catalyst of choice due to its low cost and high C-C bond rupture activity, and zirconia (ZrO₂) is widely used as the catalytic support due to its thermal and chemical stability, moderate acidity and surface oxygen mobility. The same supported Ni/ZrO₂ catalyst is a promising candidate for ethanol steam reforming (ESR), but its deactivation caused by sintering and coke deposition remains a problem.

Jinlong Gong and researchers from Tianjin University used a surfactant-assisted method to prepare a nanocomposite Ni@ZrO₂ catalyst made up of nickel nanoparticles distributed evenly throughout a similarly sized zirconia matrix. The new catalyst demonstrated higher activity and selectivity for the conversion of ethanol into CO₂ and H₂. Almost complete conversion of ethanol over a 50 hour period was observed, while the activity of the traditional Ni/ZrO₂ catalyst decreased continually after just six hours.

The even distribution of metal nanoparticles throughout the matrix allows the pore structure of the solid to be maintained while increasing the accessibility of the catalytically active nickel. The larger metal-oxide interface promotes the removal of carbon deposits while the “confinement effect” prevents the nickel metal from sintering. As highlighted in a recent C&EN article, these promising catalytic properties suggest that the synthetic methodology may be useful for the design of metal catalysts for other processes, such as dehydrogenation, that encounter similar problems.

Read this HOT Chem Comm article today (free to access until the 27th December):

A Ni@ZrO₂ nanocomposite for ethanol steam reforming: enhanced stability via a strong metal-oxide interaction
Shuirong Li, Chengxi Zhang, Zhiqi Huang, Gaowei Wu and Jinlong Gong
Chem Commun., 2013, Advance Article
DOI: 10.1039/C2CC37109J

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Spinks Symposium 2013: Regenerative Medicine – registration open

28 Nov 2012

By Jane Hordern, Deputy Editor.

28 January 2013

Chemistry Centre, Burlington House, London

The therapeutic promise of regenerative medicine, as a way to restore aging or damaged tissues and organs, is one of the most exciting areas of medicines research. With the proportion of older people increasing, degenerative and chronic diseases are a major challenge. To move forward, the chemical sciences have a vital role to play in understanding

disease mechanisms
signalling of stem cells
cellular differentiation
new methodologies for surface modification

The 2013 Spinks Symposium will explore the critical issues that underpin developments in regenerative medicine and provide a clear understanding of the challenges involved in translating research outputs into application. Particular emphasis will be put on how medicinal chemistry/chemical biology research might provide a springboard to therapeutic development. Researchers from industry, academia and the wider health sciences sectors will join together for this stimulating workshop, including oral presentations discussion groups, flash presentations and a comprehensive poster session.

How can I get involved?

Abstracts for the poster programme are now invited. Take full advantage of this exceptional opportunity to present your work and submit before Friday 21st December.
Registration is also open and if you would like to benefit from the early bird rates be sure to secure your place before Friday 21st December

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Cooperative Effects Enhance Biphasic Catalysis

28 Nov 2012

By Ruaraidh McIntosh, Science Writer.

Commodity chemicals are often produced using catalysts. Despite the many advantages of using catalysts (such as faster conversion, improved selectivity) a major difficulty is separating them from the product at the end of the reaction. Such is the significance of this problem, heterogeneous catalysts are often chosen ahead of their homogeneous brothers because they are simpler to remove at the end of the reaction, despite the homogeneous catalysts generally having better performance.

Figure 1 Crystal packing diagram of a POM-phosphazene aggregate.

An alternative solution to the separation problem is to utilise a biphasic solvent system. Partitioning the catalyst and product into different phases provides inherent separation and removes the need for expensive procedures like distillations. Ivan Kozhevnikov and Alexander Steiner at the University of Liverpool have collaborated to join their respective areas of expertise together and create catalytically active polyoxometalate (POM)-phosphazene aggregates (Figure 1) which can operate in a biphasic environment. Their communication reports rapid oxidation of test substrates by enhancing the transfer of the catalytically active POM across the two phases. Furthermore, the chemistry is “green” as it utilises relatively environmentally benign conditions.

The components of the aggregates are independently soluble in the different phases; therefore defining how this catalyst operates will be paramount to understanding and developing the system further. For example, reporting the performance of the POM or the phosphazene independently in the biphasic system would provide essential support to the claim that these aesthetically pleasing aggregates are responsible for the observed catalytic activity and remove some of the alternative potential sources.

Read the ‘HOT’ Chem Comm article today (Free to access until the 27th of December):

Novel polyoxometalate–phosphazene aggregates and their use as catalysts for biphasic oxidations with hydrogen peroxide

Michael Craven, Rana Yahya, Elena Kozhevnikova, Ramamoorthy Boomishankar, Craig M. Robertson, Alexander Steiner and Ivan Kozhevnikov
Chem. Commun., 2012, 48, Advance Article
DOI: 10.1039/c2cc36793a

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ChemComm is delighted to present its 100th issue of 2012

22 Nov 2012

By Dr Robert D. Eagling, Editor.

ChemComm is the first chemistry journal to publish 100 issues in a year and the largest international publisher of high quality communications within general chemistry.

2012 has been an exciting year for ChemComm as we faced the challenge of becoming the first chemistry journal to publish 100 issues in a year. This move was made in response to the increasing number of submissions and having published over 3000 articles for the 2^nd year in succession, ChemComm is now recognised as the largest international publisher of high quality communications within general chemistry.

After much hard work and dedication, the 100^th issue of the year has just been published online and I wanted to take this opportunity to thank everyone who has made this possible.

In particular, thanks have to be paid to our Editorial and Advisory Boards for their continued input and support, to our Associate Editors around the world, our Editorial Staff within the RSC and of course our loyal authors, readers and dedicated referees, without which this achievement would simply not have been possible.

Despite moving to 100 issues, we are still maintaining the service and quality that our authors and readers have come to expect. Our times to publication are still around 50 days and our most recent Impact Factor has once again increased to 6.169 (from 5.787 last year). We will continue to be what we always have been; the home of urgent high quality communications from across the chemical sciences.

Thanks again for everything in 2012 and here’s to doing it all again in 2013!

Dr Robert Eagling,

Editor, Chemical Communications

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Chemical Communications Blog

Liquid crystal relaxation controlled by dopant kinetics

True racemic crystals: Surprising new insights on preparation and structure

A new way to look at cancer cell detection

Early Alzheimer’s diagnosis compound

Probing assembly of supramolecular architectures with non-linear optics

ChemComm Emerging Investigator Lectureship: Nomination Deadline Friday 7 December

Nanoconfinement leads to increased catalytic stability

Spinks Symposium 2013: Regenerative Medicine – registration open

Cooperative Effects Enhance Biphasic Catalysis

ChemComm is delighted to present its 100th issue of 2012

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