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Technicolour pKa indicator

12 Jul 2013

Scientists in Japan have shown that a dye can present more than five different colours according to the acidity of the solution it is in and can be used to visualise acid–base equilibria in non-polar solvents. It is extremely unusual for a single dye to demonstrate so many different colours.

Hydrogen bonding, deprotonation and different degrees of protonation all turn the dye, oxoporphyrinogen, a different colour. Hydrogen bonding of an anion to oxoporphyrinogen gives an increasingly blue colour depending on the strength of the interaction. Strongly basic substances cause oxoporphyrinogen to deprotonate and turn a pale brown hue. In the opposing direction, acids of certain strength can doubly protonate the dye. This induces tautomerisation of the dye’s structure, which varies its conjugated electronic form, leading to another significant colour change, in this case to red. Stronger acids quadruply protonate the dye, so all available electronegative atoms are protonated, turning it bright green.

Jonathan Hill, from the National Institute for Materials Science, Ibaraki, who led the work, says there are two main reasons to want to see acid–base equilibria in non-polar solvents…

Read the full article in Chemistry World

Read the original journal article in ChemComm:
Colorimetric visualization of acid–base equilibria in non-polar solvent
Atsuomi Shundo, Shinsuke Ishihara, Jan Labuta, Yosuke Onuma, Hideki Sakai, Masahiko Abe, Katsuhiko Ariga and Jonathan P. Hill
Chem. Commun., 2013, 49, 6870-6872
DOI: 10.1039/C3CC42859A

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Azobenzene switching controls movement of oleate assemblies

08 Jul 2013

The study of controlled motion on the molecular scale is leading to the development of materials in which molecular motions can be used to control a macroscopic effect. In particular, the isomerisation of azobenzene from the stable trans- form to the cis- isomer on irradiation with UV light has been widely used in supramolecular and soft matter chemistry as a simple, controllable molecular switch for this purpose.

In this HOT ChemComm article, scientists from Hokkaido and Kanagawa universities in Japan have investigated the macroscopic motion of some simple oleate assemblies containing azobenzene derivatives.

Simple oleates form a range of supramolecular assemblies under certain pH conditions. The authors found that mixtures of simple oleates with their new azobenzene containing analogues could also form these assemblies, and investigated the effect of irradiating the structures with UV light. They found that vesicles containing azobenzene derivatives could be seen to reversibly expand and contract on irradiation. Additionally, helical multilayer assemblies containing azobenzene derivatives could be forced to reversibly straighten and re-coil using UV light (shown below).

azobenzen oleates azobenzene helices

This Communication describes an intriguing demonstration that designing controllable, switchable molecular components can create highly organised macroscopic motions, and is a great step towards functional supramolecular machinery.

Read this HOT ChemComm article today:

Macroscopic motion of supramolecular assemblies actuated by photoisomerization of azobenzene derivatives
Yoshiyuki Kageyama, Naruho Tanigake, Yuta Kurokome, Sachiko Iwaki, Sadamu Takeda, Kentaro Suzukib and Tadashi Sugawara
Chem. Commun., 2013, Advance Article
DOI: 10.1039/C3CC43488E

Cally Haynes is a guest web-writer for ChemComm. She is currently a post doctoral researcher at the University of Southampton, and her research interests include the supramolecular chemistry of anions. When not in the laboratory, she enjoys travelling and watching football.

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Synthesis of non-toxic HSP90 inhibitors via Suzuki–Miyaura reaction

02 Jul 2013

HSP90 (Heat Shock Protein 90) is a chaperone protein which is involved in the disease pathways of many cancers, and such neurodegenerative illnesses as Alzheimer’s and Parkinson’s disease. The inhibition of HSP90 has gained a great deal of attention since its discovery, and offers the potential to treat many serious illnesses. Much interest has focused on geldanamycin—a benzoquinone ansamycin which is highly effective in the inhibition of HSP90. Unfortunately, geldanamycin suffers from high liver toxicity in addition to poor stability and solubility which greatly limits its therapeutic utility.

Christopher Moody at the University of Nottingham has devoted much research toward the targeting and inhibition of HSP90. His group recently discovered that the 19-position plays a key role in geldanamycin’s toxicity, and that substitution at that position can render the compound non-toxic, through the suppression of conjugate addition reactions which are thought to be responsible for its hepatotoxicity.

While Moody previously utilized the Stille reaction for substitution at this position, the transformation was limited in cases, not scalable, and its industrial application was hampered by undesirable, toxic reagents and waste products. In this Communication, Moody and Kitson overcome these problems by employing the Suzuki–Miyaura reaction to install functionality at the 19-position. Using a modification of the Suzuki–Miyaura reaction previously described by Eli Lilly researchers, Moody was able to obtain functionalised geldanamycins in yields which compare well with or exceed those obtained by the Stille protocol.

Beginning with readily accessible 19-iodogeldanamycin (1), the cross-coupling reaction allows a range of substituents to be installed easily, using an array of widely available boronic acids and esters. Aryl-, vinyl- and allyl-groups could be installed with excellent yields, while the use of alkyl boronic acids and esters afforded moderate results. The electronic supplementary information contains full details of the reaction optimisation.

This method allows non-toxic 19-substituted-geldanamycins to be prepared efficiently and without the disadvantages associated with the previous Stille route. Not only will this benefit the synthesis of geldanamycins within the pharmaceutical industry, but it should also encourage further clinical research of these important compounds.

For more, check out the ChemComm article in full:

An improved route to 19-substituted geldanamycins as novel Hsp90 inhibitors – potential therapeutics in cancer and neurodegeneration
Russell R. A. Kitson and Christopher J. Moody
Chem. Commun., 2013, Advance Article
DOI: 10.1039/C3CC43457E

Ruth E. Gilligan is a guest web-writer for ChemComm. She has recently completed her PhD in the group of Prof. Matthew J. Gaunt at the University of Cambridge, focusing on the development and application of C–H functionalisation methodology.

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Date rape drug sensor

28 Jun 2013

The first fluorescent sensor for known date rape drug gamma-butyrolactone (GBL) has been developed in Singapore. It emits orange fluorescence in alcoholic drinks containing GBL when irradiated with a green laser.

Gamma-butyrolactone (GBL) is a readily available industrial solvent that is often used as a date rape drug. There are several detection kits that can show if a drink has been spiked with drugs like gamma-hydroxybutyric acid (GHB) and ketamine but there are no commercially available sensors to detect GBL.

Now, Young-Tae Chang and his group at the National University of Singapore have developed the first sensor for the detection of GBL. They used a fluorescent dye library…

Read the full article in Chemistry World»

Read the original journal article in ChemComm:
Development of a fluorescent sensor for an illicit date rape drug – GBL
Agrawalla, Pei Sze Fronia Eng, Sung-Chan Lee, Wang Xu and Young-Tae Chang
Chem. Commun., 2013, 49, 6170-6172
DOI: 10.1039/C3CC43153C

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Synthesising gold- and silver-NHC complexes using a weak base

24 Jun 2013

Scientists from the University of Zaragoza in Spain have developed a simple and efficient method of synthesising N-heterocyclic carbene (NHC) gold and silver complexes with the use of an extremely weak base¹.

Gold-NHC complexes are commercially important precursors of active, luminescent species that catalyse many useful reactions, such as cycloisomerisation, rearrangement of allylic acetates, C-H activation, carbene transfer, polymerisation, among others. In addition, they have potentially significant applications in the synthesis of new pharmaceuticals and natural products.

Conventional methods of gold-NHC synthesis– the generation of free NHC and the Ag-carbene transfer route– present several logistic and economic limitations, such as the need for an inert atmosphere and the use of additives. These methods are not always efficient, and typically require complicated working conditions in order to produce even moderate yields.

M. Concepción Gimeno and her team’s novel and elegant one-pot synthetic route involves isolating imidazolium salts using [AuCl(tht)] (tht = tetrahydrothiophene) in the presence of a mild base, such as K₂CO₃, to produce gold-NHC complexes with very high yields (91-94%) over relatively short reaction times (1.5 hours).

c3cc42919a-s2

Similarly, Gimeno et al. found that, using the same mild base protocol, silver-NHC complexes could also be efficiently synthesised using AgNO₃, with vast potential significance in transmetalation.

c3cc42919a-s3

In both routes, the reactions occur under ambient conditions, eliminating the need to work in an argon atmosphere, and using readily-available technical grade solvents.

Interestingly, a mere few days later, Gimeno et al.‘s groundbreaking work was followed closely and independently by a related Communication from Steven Nolan’s group at the University of St Andrews. In addition to testing a similar methodology, Nolan’s team compared small- and larger-scale reactions, and characterised compounds by ¹H and ¹³C{¹H} NMR spectroscopies, as well as by elemental analysis².

To find out more about these fascinating breakthroughs in organometallics, read these HOT ChemComm articles now for free!

1. Simple and efficient synthesis of [MCI(NHC)] (M = Au, Ag) complexes
Renso Visbal, Antonio Laguna and M. Concepción Gimeno
Chem. Commun., 2013, 49
DOI: 10.1039/C3CC42919A, Communication

2. Straightforward synthesis of [Au(NHC)X] (NHC = N-heterocyclic carbene, X = Cl, Br, I) complexes
Alba Collado, Adrián Gómez-Suárez, Anthony R. Martin, Alexandra M. Z. Slawin and Steven P. Nolan
Chem. Commun., 2013, 49
DOI: 10.1039/C3CC43076F, Communication

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Students develop antivenom in high school lab

21 Jun 2013

A US high school teacher and nine of his students have made nanoparticles that can neutralise venom from one of the most dangerous snakes in Africa. These nanoparticles could offer a way to make cheaper and more practical antivenoms.

Traditional antivenoms are made by injecting sublethal toxin doses into an animal to invoke an immune response. Antibodies produced in this immune response are then harvested from the animal’s serum. Such antivenoms are not only expensive but they also required refrigeration – a major limitation considering antivenoms are often required in remote locations.

Now, Steven Sogo and his best students from Laguna Beach High School in California, have synthesised nanoparticles that will selectively bind to toxins in venom from the Mozambique Spitting Cobra. In vitro tests showed that, by binding to the toxins…

Read the full article in Chemistry World»

Read the original journal article in ChemComm:
Molecularly-imprinted nanoparticles that recognize Naja mossambica cytotoxins: binding studies and biological effects
Samantha Piszkiewicz, Evan A. Kirkbride, Nicolai Doreng-Stearns, Blake R. Henderson, Melissa A. Lenker, Erika Tang, Laura H. Kawashiri, Curtis S. Nichols, Sebastian C. Moore and Steven G. Sogo
Chem. Commun., 2013, 49, 5954-5956
DOI: 10.1039/C3CC42394H

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HOT ChemComm articles for June

19 Jun 2013

Engineering robust polar chiral clathrate crystals
Christopher S Frampton, Kamal A. Ketuly, A. Hamid A. Hadi, James H Gall and David D. MacNicol
Chem. Commun., 2013, Accepted Manuscript
DOI: 10.1039/C3CC43012J, Communication

Free to access until 21st July 2013

Lewis acid-catalyzed regioselective synthesis of chiral α-fluoroalkyl amines via asymmetric addition of silyl dienolates to fluorinated sulfinylimines
Feng-Ling Qing, Yingle Liu, Jiawang Liu and Yangen Huang
Chem. Commun., 2013, Accepted Manuscript
DOI: 10.1039/C3CC43741H, Communication

Free to access until 21st July 2013

Ruthenium catalyzed hydroaminoalkylation of isoprene via transfer hydrogenation: byproduct-free prenylation of hydantoins
Daniel C. Schmitt, Jungyong Lee, Anne-Marie R. Dechert-Schmitt, Eiji Yamaguchi and Michael J. Krische
Chem. Commun., 2013,49, 6096-6098
DOI: 10.1039/C3CC43463J, Communication

C3CC43463J

Free to access until 21st July 2013

Click here for more free HOT ChemComm articles for June!

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Corporals can overrule Sergeants in self assembly

11 Jun 2013

Creating chiral layers on a surface is attracting increased attention because of possible application in optical resolution and heterogeneous catalysis. Chiral layers can be achieved by the self assembly of enantiopure molecules on a surface.

Alternatively, achiral molecules can be forced to form chiral surface assemblies by using a chiral building block or by adding a small amount of a chiral auxillary– the “Sergeant-and-Soldiers” effect first described by Mark Green (NYU-Poly) and co-workers in 1989.

In this HOT ChemComm article, Chem Soc Rev Associate Editor David Amabilino from ICMAB-CSIC, Barcelona, ChemComm Associate Editor Steven De Feyter from KU Leuven, and their co-workers have taken this principle a stage further and questioned if the intrinsic chirality of a building block (the “Sergeant”) can be overruled by using a chiral solvent (the “Corporal”).

They found that achiral porphyrin 1 could be forced to form chiral monolayers using (S)-and (R)-2-octanol as a solvent. More impressively, they also found that the chirality of the assembly of chiral porphyrins (S)-2 and (R)-2 could be directed using these solvents. The combination of (R)-2 and (S)-2-octanol gave an enantiopure surface assembly, whereas using (R)-2-octanol resulted in a mixture of 2 different domains of opposite chirality. Molecular dynamics simulations indicated that this could be due to hydrogen bonding between the solvent molecules and the amide groups of the porphyrins. If more than one chiral centre was present (3 and 4), the chirality of the molecule was able to dominate the solvent effect.

This is a fascinating report of how a simple, weak interaction with solvent can overcome the inherent chirality of a stereogenic centre. This work could lead to the preparation of bistable systems in which the chirality could be switched with a simple change of solvent.

Download this HOT ChemComm article today!

‘Sergeants-and-Corporals’ principle in chiral induction at an interface
Iris Destoop, Hong Xu, Cristina Oliveras-González, Elke Ghijsens, David B. Amabilino and Steven De Feyter
Chem. Commun., 2013, Advance Article
DOI: 10.1039/C3CC42584C

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ChemComm Emerging Investigators Issue 2013

04 Jun 2013

We are delighted to announce the publication of the 2013 ChemComm Emerging Investigators issue.

This is the third edition of this themed collection and we have been overwhelmed by the community’s positive response. I encourage you to take a look at the exceptional communications and feature reviews in this issue, as well as our previous issues in 2011 and 2012.

The issue contains over 90 Communications as well as a selection of Feature review articles, take a look at the whole collection today.

We invite you to submit your next communication article to ChemComm.

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Releasing reactive oxygen

29 May 2013

Scientists in Canada have made nanoparticles that release singlet oxygen when a laser beam is shone on them. The nanoparticles could improve the effectiveness of photodynamic therapy.

Under the right conditions, oxygen, light and photosensitiser molecules combine to generate a short-lived poisonous oxygen species called singlet oxygen. This is the basis of photodynamic therapy, a treatment for some cancers. Normally, photodynamic therapy requires oxygen to be present in the target cells; however, tumours often contain much lower oxygen levels than healthy tissues.

Release of singlet oxygen from nanoparticles

Now, Neil Branda and colleagues at Simon Fraser University have developed a system that does not rely on oxygen being present. The team anchored anthracene endoperoxide ligands onto…

Continue reading the full article in Chemistry World »

Read the original journal article in ChemComm:
Photothermal release of singlet oxygen from gold nanoparticles
Amir Mahmoud Asadirad, Zach Erno and Neil R. Branda
Chem. Commun., 2013, 49, 5639-5641
DOI: 10.1039/C3CC42217H

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