Tallinn researchers create 31 chiral molecular sensor structures

Researchers at Tallinn University of Technology have created 31 mirror image molecular structures that could support the development of next generation chiral sensor materials, ERR reported.

Chirality is important in the development of medicines, food products, fragrances and plant protection products. One mirror image of a molecule may produce the desired effect, while the other may act more weakly or in a completely different way. In extreme cases, one version may be a medicine and the other a poison.

Enzymes, receptors and cellular processes in nature can recognise molecules with the correct chirality. The system works much like a hand fitting into the correct glove.

To distinguish between chiral molecules in the laboratory, the material that recognises them must itself have some form of chirality. Researchers from Tallinn University of Technology’s supramolecular research group found a way to transfer chirality from one molecule to another by combining two very different types of molecules.

The first were porphyrins, molecules related to compounds found in haemoglobin, which carries oxygen in the body, and chlorophyll, which drives photosynthesis in plants. Because porphyrins have exceptionally good optical properties, they act like chemical signal lamps that can show whether a particular substance is present in a solution.

However, porphyrins are completely symmetrical and cannot distinguish between right and left handed substances. The researchers therefore added hemicucurbiturils, pumpkin shaped building blocks that can be produced in two mirror image forms.

Combining the two building blocks produced a complete sensor. The barrel shaped hemicucurbituril captures the correct substance, while the porphyrin gives a visible signal when it does so.

In their experiments, the researchers allowed zinc and magnesium porphyrins to react spontaneously with host molecules while testing different solvents and temperatures. They described a total of 31 new molecular structures. Their final shapes were determined by very small changes to the original chemical recipe.

“The most surprising finding was that, depending on the components used, the molecules organised themselves into very different structures: individual complexes, long chains and even mirror image spirals. This shows how flexible this molecular system really is,” said Marko Sakarašvili, a doctoral student and junior researcher at Tallinn University of Technology and the article’s first author.

The results showed that the behaviour of the molecules can be directed through a relatively simple choice of building blocks. This opens the possibility of creating a library of chiral materials with different properties.