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Wednesday, January 13, 2010

Same chemical composition... but different structure

How the heck is the chemical notation for a formula like this thing gonna wind up?!

From the abstract at the Royal Society of Chemistry's website...

Usually, you'd expect two compounds with the same composition, atom-to-atom connectivity and symmetry to be chemically identical too. But scientists investigating metal-organic frameworks have discovered a surprising exception to this rule by identifying two isomers with the same symmetry and bonding but different gas storage properties.

A team led by Shengqian Ma at the Argonne National Laboratory, Illinois, US, investigated a rod-like tetracarboxylate molecule (ebdc) which can bind to a metal atom from any one of four binding points, one at each corner of a rectangle. When it was heated with a copper salt at 75 °C, a crystal phase formed (the alpha-phase) and at 65 °C a phase with different properties (the beta-phase) formed. So far, so normal. But when Ma carried out crystal analysis on these two compounds, he found that they had the same composition, the same atom-to-atom connectivity and the same symmetry. 'This type of symmetry-preserving isomerism has never been observed before in metal-organic frameworks,' says Ma.

In layman's terms, by changing the environment the researchers also changed how the substances bonded to each other. It's not uniform symmetry, as generations of chemistry books have taught.

So right there, before our eyes, a fundamental understanding of science has been drastically altered. And there ain't no telling yet what kind of neat-o applied technologies could eventually be developed from this.