SKYFALL · Stimuli-responsive chiral foldamers in solution and light-emitting diodes

Stimuli-responsive chiral foldamers in solution and light-emitting diodes

The SKYFALL project investigated how synthetic molecular systems can be designed to assemble in a controlled way in solution to generate responsive optical behaviour. The work focused on foldamers, artificial molecular chains that are designed to fold into well-defined shapes through weak, reversible interactions, in a way that is comparable to how proteins fold to perform specific functions. A key concept explored in SKYFALL is molecular hybridisation, which, in this context, refers to the reversible association of two foldamer strands through non-covalent interactions. Hybridisation allows individual molecular chains to assemble temporarily, dynamically and responsively to its environment. The foldamers studied in SKYFALL were designed to adopt helical shapes, similar to a spiral staircase. These helices can twist in two possible directions, known as left- or right-handed helicity. Controlling the preferred direction is important because it determines the chiral environment created by the molecule. Chirality is a property that describes objects whose mirror images are not superimposable, like left and right hands, and it is a key feature in many functional molecular systems. One of the core aims of the project was to control the helical direction of the foldamer by introducing chiral side chains, which act as molecular “instructions” to bias the direction of the twist of the helix. By controlling the handedness of the helicity, the project aimed to control the chiral environment experienced by molecular components attached to the foldamer. Importantly, chiral molecular systems can interact differently with different forms of light, a property that is important in applications such as sensing, optoelectronics and advanced display technologies. To probe and understand these effects, light-emitting units (fluorophores) were attached to the foldamers. The chiral environment imposed by the helical structure influences how these fluorophores emit light, providing an easy route to probe the molecular organisation. However, achieving reliable control of chirality in dynamic and responsive molecular systems remains a major scientific challenge. To address this challenge, SKYFALL combined chiral molecular design with supramolecular assembly (hybridisation) and light-responsive elements. Photoswitchable components, which change shape when exposed to specific wavelengths (colours) of light, were incorporated between two foldamer “arms” to enable external control over hybridisation. The project examines how environmental factors, such as solvent, concentration, temperature and light, influence how foldamer strands interact and organise. Through this approach, the project aimed to generate fundamental knowledge that supports the long-term development of responsive chiral materials within the European research landscape of advanced functional materials.

Data: CORDIS, © European Union