Posted on 01/28/2013 11:03:17 PM PST by neverdem
A quick experiment at the start of a PhD has resulted in a stable organic compound with four unpaired electrons. The researchers are now investigating this unusual structure for applications in batteries and data storage.
When Jonathan Barnes joined Fraser Stoddarts group at Northwestern University in Evanston, US, the group were working on radical enhanced molecular recognition and trapping pairs of molecules in close contact. The team were using molecules held within a macrocycle and then removing two electrons to create a radical pair. Barnes looked at some of the other projects going on in the lab and wondered if something similar could be done with the groups catenanes interlocked chemical rings. A lot of people said it wasnt possible because logically it doesnt make sense to have this much charge so close together, says Barnes. It was a pie-in-the-sky kind of goal I was reaching for but it turned out actually that it worked, and it worked on the first try.
The ability to switch the catenane between paramagnetic and diamagnetic states makes it a very interesting material for data storage
The key to the stability of the new radical compound is the mechanical bond that links the two macrocycles, forcing the charged species to remain close. And that proximity means that the molecule never oxidises to a fully charged species but stops at the paramagnetic species 7+. That, says Barnes, is because the molecule is trying to minimise the charge in the centre where the two catenanes link. The charged units have no choice but to interact with one another, explains Barnes, so it holds on to that remaining electron to reduce the charge repulsion.
But while the 7+ species is paramagnetic, all the other charged species are diamagnetic, as the electrons spins pair. Using cyclic voltammetry it is possible to quickly switch between the paramagnetic and diamagnetic states by adding and removing electrons. And it is this simple switching that could be the key to a potential application of the material: memory storage.
First off though, Barnes and Stoddart are working with a team in Korea to investigate the use of the material in lithium ion batteries. Batteries, explain Barnes, need materials that accept electrons pretty well and thats what the catenane does.
A Prasanna de Silva of Queens University Belfast, UK, describes the work as a fine paper that will make the career of young Jonathan Barnes. The novelty of Barnes material, he adds, is that the high density of positive charges makes it resist becoming fully charged in air. Since the paramagnetic state can be reversibly converted to several diamagnetic states, says de Silva, confirming Barnes, the current molecular magnets will likely find information storage applications since they are easily switchable, long-lived and metal-free.
J C Barnes et al, Science, 2013, DOI: 10.1126/science.1228429
Wow, a molecular battery!
I can imagine all sorts of uses for that
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Mopping up oil spills with marshmallows (flexible aerogels)
Microbes Survive, and Maybe Thrive, High in the Atmosphere
News in Brief: Gene variant makes flu particularly dangerous
FReepmail me if you want on or off my health and science ping list.
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