Archive for the ‘News’ Category

Chemists reinvent the wheel

Scientists in the US have made a new molecular wheel. The bimetallic cluster, Nb2Au6, consists of a Nb≡Nb tripled bonded unit surrounded by a Au6 ring.

A molecular wheel with a short Nb≡Nb triple bond coordinated by an Au6 ring and reinforced by σ aromaticity

Lai-Sheng Wang and his team at Brown University made the cluster by striking a gold and niobium solid target with an intense laser beam. Theoretical calculations show that there are two π bonds and one σ bond in the Nb2 dimer. The cluster also has five totally delocalised σ bonds – scientists have not reported σ aromaticity in a metal–ligand system before.

Read the full story by Jennifer Newton on Chemistry World.

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Scientists poke holes in zeolite theory

Theorists in the UK have studied the aluminium distribution in a number of catalytically active zeolite species, finding evidence that –Al–O–Al– linkages could exist in some zeolite species after all.1


Source: Royal Society of Chemistry
Löwenstein’s rule of ‘aluminium avoidance’ says that that –Al–O–Al– bonds are forbidden but new research hints that this motif may not be as elusive as is generally believed

Since Löwenstein first published his study on ‘the distribution of aluminium in the tetrahedra of silicates and aluminates’ in 1954,2 scientists had generally accepted that aluminium clusters cannot exist within zeolite structures. Löwenstein’s rule of ‘aluminium avoidance’ states that whenever two tetrahedra are linked by an oxygen bridge, if the centre of one is occupied by an aluminium atom, the other must be occupied by silicon. As such, Löwenstein’s rule prohibits –Al–O–Al– linkages from occurring within zeolites, and dictates that the ratio of Al:Si in zeolites must be 1:1.

Read the full story by Hannah Dunckley on Chemistry World.

1 R E Fletcher, S Ling and B Slater, Chem. Sci., 2017, DOI: 10.1039/c7sc02531a (This article is open access.)
2 W Löwenstein, Am. Mineral., 1954, 39, 92

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Hydrogen bonded system faces strength test

Scientists in Spain have devised a versatile technique that uses DNA to pull apart host–guest complexes so they can measure the overall strength of hydrogen bonds in that system. The method can distinguish forces as low as 0.1–1pN.

Source: © Royal Society of Chemistry
Using a DNA reporter guarantees that the force measurements refer to a single system

Procedures to measure supramolecular interactions in the bulk, under equilibrium conditions, are well established. But nature operates out of equilibrium, so scientists want a technique to measure hydrogen bonds in conditions realistic to living systems.

Read the full story by Jennifer Newton on Chemistry World.

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An absolute acidity scale for solvents

Comprehensive solvent acidity scale could help make acid-catalysed reactions more reliable and reproducible.

Using acids from this table, buffer solutions of a well-defined composition can be prepared spanning an acidity range of over 28 pH units, which is double the pH window of water.

A collaboration between scientists in Estonia and Germany has resulted in a comprehensive solvent acidity scale spanning 28 orders of magnitude, twice as much as the classical pH scale.

Click here to read the full story on Chemistry World written by Lynn Murphy.

 

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Plotting a course to new antibiotics

Researchers in Switzerland and Italy have devised a way to chart protein-based antibiotics according to their chemistry. This map of the chemical space has allowed them to search for new compounds more intelligently and has already led to them finding a new antibiotic for a highly resistant hospital bug.

In the biochemical arms race between bacteria and medicine, novelty is key. New types of molecules, acting in new ways, can kill microbes that are resistant to our existing arsenal. Unfortunately, the world of potential molecules is huge and mostly uncharted. New antibiotics act as landmarks, signposting where other useful compounds might lie. Researchers then start exploring nearby – although in an abstract chemical space, ‘nearby’ can be a tricky concept.

Source: © Royal Society of Chemistry
Chemical space guided the discovery of antimicrobial bridged bicyclic peptides against Pseudomonas aeruginosa and its biofilms

Read the full story by Alexander Whiteside on Chemistry World.

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Polar solvents promote halogen bonds over hydrogen ones

Solvent effects control competition between hydrogen bonding and halogen bonding in supramolecular systems, new research shows. The upshot of the finding is a potential new tool to direct supramolecular self-assembly.

During self-assembly, each molecule breaks its bonding interactions with neighbouring solvent molecules, then forms new interactions. To investigate competition between hydrogen bonding and halogen bonding when co-crystals form, researchers from an ongoing collaboration between the UK Universities of Sheffield, York and Cambridge chose seven solvents of different polarities to study three aromatic molecules known to self-assemble. The molecules’ functional groups included pairs of hydrogen bond and halogen bond donors that compete for a common acceptor group.

Solvent plays a critical role in directing self-assembly

Read the full story by Fiona Tscherny on Chemistry World.

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First +5 praseodymium compound with PrN triple bond made

The first pentavalent praseodymium nitride–oxide that features a rare Pr≡N triple bond is the second ever lanthanide(V) complex to be made.

Lanthanide chemistry is dominated by the +3 oxidation state. There are some common +4 lanthanide complexes such as cerium oxide (CeO2), but +5 compounds have proven elusive. Praseodymium has long been considered as the most promising route to lanthanide(V) chemistry as it has five valence electrons, but the first pentavalent praseodymium complex, the oxide PrO2+, was only synthesised last year.

Source: © Royal Society of Chemistry
Calculations led to these representations of the molecular orbitals of the praseodymium(V) compound, NPrO

Read the full story by Aurora Walshe on Chemistry World.

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15-minute test catches out flu virus

A team in the US has designed a test for detecting influenza viruses in just 15 minutes using a glucose meter – a cheap, handheld instrument that is widely available.

Source: © Royal Society of Chemistry
Proteins sitting on the flu viruses’ surface cleave a carbon–oxygen bond in a modified sialic acid, releasing the sugar galactose

Suri S Iyer and colleagues from Georgia State University have now designed a test to detect influenza viruses A and B in just 15 minutes. The test only requires a nasal swab and a glucose meter – a simple instrument usually used for diabetes control. ‘Influenza virus can be deadly especially in weak or immunocompromised people. This diagnostic can help these people as vaccines for flu are not perfect,’ Iyer explains.

Read the full story by Adrian Robinson on Chemistry World.

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Molecular suit provides basic protection

Scientists have designed a macrocycle that can completely surround a small molecule like a suit and protect it from a strong base. This reversible suiting strategy could find applications as protecting groups in organic synthesis and the design of molecular machines.


Source: © Royal Society of Chemistry
The suit-1-ane: a macrocycle (orange) completely encloses a benzimidazolium cation (blue)

Protecting groups alter the reactivity of organic molecules by shielding functional groups from other reactants. Mechanically interlocked molecules (MIMs) are linked structures that require a covalent bond to be broken to separate them, which could make them useful protecting groups.

Read the full story by Harriet Brewerton on Chemistry World.

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Tamed radicals expand chemical space

A method to functionalise complex molecules with catalytic radicals could expand chemical libraries of the drug and agrochemical industry

Source: © Royal Society of Chemistry Even complex molecules like the anti-cancer drug camptothecin (top left) can be modified using Molander’s radical alkylation

US scientists have developed a visible-light mediated reaction that uses tamed alkyl radicals to functionalise complex molecules. This mild and selective method could allow chemists to explore new corners of chemical space and to discover new drugs and agrochemicals.

Read the full story by Jessica Dwyer on Chemistry World.

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