Periodic Reporting for period 1 - SKYFALL (Stimuli-responsive chiral foldamers in solution and light-emitting diodes)
Okres sprawozdawczy: 2023-12-04 do 2025-12-03
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.
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.
During the project, a series of chiral foldamer systems were designed, synthesised, and fully characterised in order to understand how molecular structure influences helical handedness and the resulting optical outputs. Fluorescent units were incorporated to enable the detailed optical investigation of the assembled systems.
The hybridisation of the foldamers was studied under different conditions, including changes in solvent, concentration and temperature. Assemblies formed from two identical foldamer strands (homoduplexes) and two distinct foldamer strands (heteroduplexes) were identified. These studies provided quantitative insight into how strongly foldamers associate with one another and how hybridisation influences the optical signals produced.
The project also assessed the suitability of these systems for solid-state applications. This analysis revealed intrinsic limitations related to aggregation and the consequent loss of light emission at high concentrations, leading to further investigations into these effects.
A second major achievement was the demonstration of light-controlled hybridisation. A photoswitchable azobenzene unit was integrated between two foldamer strands, as if they were arms attached to a central body. Upon light irradiation, the body changes shape, bringing the two foldamer arms into close proximity, allowing for supramolecular assembly to occur. This work provided evidence that foldamer hybridisation can be externally controlled using a non-invasive stimulus.
The hybridisation of the foldamers was studied under different conditions, including changes in solvent, concentration and temperature. Assemblies formed from two identical foldamer strands (homoduplexes) and two distinct foldamer strands (heteroduplexes) were identified. These studies provided quantitative insight into how strongly foldamers associate with one another and how hybridisation influences the optical signals produced.
The project also assessed the suitability of these systems for solid-state applications. This analysis revealed intrinsic limitations related to aggregation and the consequent loss of light emission at high concentrations, leading to further investigations into these effects.
A second major achievement was the demonstration of light-controlled hybridisation. A photoswitchable azobenzene unit was integrated between two foldamer strands, as if they were arms attached to a central body. Upon light irradiation, the body changes shape, bringing the two foldamer arms into close proximity, allowing for supramolecular assembly to occur. This work provided evidence that foldamer hybridisation can be externally controlled using a non-invasive stimulus.
SKYFALL delivered new fundamental insights into the relationships between foldamer structure, supramolecular hybridisation and chiral optical behaviour. In contrast to previous studies that relied on mainly external or terminal chiral induction groups, this project demonstrated the use of chiral side chains embedded directly within the foldamer backbone to control helicity.
The project further expands the state of the art by showing that light-responsive elements can be used to actively control foldamer assembly, enabling reversible and dynamic modulation of molecular organisation. Additionally, the observation of higher order (using more than two foldamer chains) supramolecular organisation mediated by foldamer hybridisation highlights how relatively simple molecular building blocks can generate complex and responsive architectures through non-covalent interactions.
These results provide a foundation for future research on stimuli-responsive supramolecular materials. Further progress towards applications will require improved control over aggregation and optimisation of light-emitting properties at high concentrations. The knowledge generated by SKYFALL directly informs these next research steps and supports the development of new collaborative research projects within Europe.
The project further expands the state of the art by showing that light-responsive elements can be used to actively control foldamer assembly, enabling reversible and dynamic modulation of molecular organisation. Additionally, the observation of higher order (using more than two foldamer chains) supramolecular organisation mediated by foldamer hybridisation highlights how relatively simple molecular building blocks can generate complex and responsive architectures through non-covalent interactions.
These results provide a foundation for future research on stimuli-responsive supramolecular materials. Further progress towards applications will require improved control over aggregation and optimisation of light-emitting properties at high concentrations. The knowledge generated by SKYFALL directly informs these next research steps and supports the development of new collaborative research projects within Europe.