A mechanism to control the shape of molecules could open up new fields of chemistry, with applications from computing to pharmaceuticals. The authors describe it as the first new method for reshaping molecules reported since 1961.
Although some atoms can only be put together in a single way, others have multiple isomers, constructions of the same formula in different shapes. The chemical and biological properties of two isomers can be very different – some drugs are only effective in one isomer, for example, and quality control requires making sure the product is in the correct form.
Nature Chemistry has announced a new way of controlling the formation of certain molecules, including producing molecules that can change isomer in a controlled way. So far the process has been restricted to simple molecules, but the authors regard their work as a proof of principle with important technological potential. The transformation is so new, the paper notes recognized chemistry nomenclature cannot describe it.
Constitutional isomers have atoms or functional groups held together with fundamentally different bonds. Those described in this study, however, are among the classes of stereoisomers, where the bonds are the same but the geometrical positioning, for example the angle between atoms, varies.
First author Peter Canfield, a PhD student at the University of Sydney, told IFLScience that the team confined boron-oxygen-boron molecules inside a porphyrin, a kind of molecular scaffold used to transport molecules. The porphyrin “anchors the boron atoms so they can undergo bending motions, without external mechanisms confounding as would happen in another environment,” Canfield said. The bonds act like a hinge, changing the angles of the boron atoms relative to the oxygen.
The result, Canfield explained, is a switch, which can be easily adjusted between states by temperature. Canfield noted computer memory relies on the existence of switches that can be easily changed from one to zero. An array of molecules switching between isomer states could provide tremendously dense non-volatile memory storage.
Canfield noted porphyrins, which include the hemoglobin that carries oxygen in the blood, and plants' chlorophyll, are ubiquitous in nature, providing a ready stock if we want to create bioactive products.
The discovery was made after the authors considered the diversity of molecular shapes that should be geometrically possible. “When we looked at this, we noticed a fundamental form which had never been made before,” said Professor Jeffrey Reimers of the University of Technology Sydney in a statement.
The researchers then set out to find ways to make this form, eventually confirming spectroscopically that they had not only made it but could keep it stable at room temperature. Other chemicals have been found that temporarily form similar isomers, but shift on a scale of nanoseconds, ruling out practical applications.
