![]() ![]() ![]() ‘This is an exciting prediction that is likely to have wider implications.’ ‘The chirality, and hence the optical rotatory power, can be switched,’ he says. Another possibility is to use these stacks as nuclei for chiral amplification from a fresh feed of achiral molecules.’ĭaan Frenkel, an expert in self-assembled structures at the University of Cambridge, UK, also points out the applications of structures like these with regards to polarised light. ‘Use of an electric field to switch the supramolecular handedness will ensure that a single material can be used for separating both enantiomers, a significant improvement over the present methods. ‘These supramolecular stacks could act as chiral templates for use in enantioseparation,’ says Balasubramanian. The bonds then reform in the direction of the field, reversing the handedness of each helix. Instead, the intermolecular hydrogen bonds break so the amide groups rotate freely. However, in, for example, a liquid crystal, where many of these stacks are lined up together, overall rotation of the stacks is impossible. Sundaram Balasubramanian and his co-workers at the Jawaharlal Nehru Centre for Advanced Scientific Research (JNCASR) have used computer simulations to test the effect of an electric field on these stacks, and were surprised to discover that not only could they control the overall dipole of the structure, but also its chirality, or handedness.Īpplying an external electric field antiparallel to the direction of the macrodipole encourages the molecule to realign itself in the direction of the field. Each BTA molecule can form three hydrogen bonds by using oxygen atoms in the amide groups and the direction of these hydrogen bonds determines the direction of the dipole moment. Application of an electric field in the direction opposite to that of the macrodipole reverses the handedness of the structureĮlectric fields can switch both the net dipole moment and the helical handedness of helical supramolecular structures, according to a theoretical study by scientists in India.īenzene-1,3,5-tricarboxamide (BTA) molecules self-assemble, by hydrogen bonding, into columnar structures with a macrodipole moment along their stacking direction. ![]()
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