Periodic Reporting for period 4 - LEAPS (Light effected autonomous molecular pumps: Towards active transporters and actuating materials)
Okres sprawozdawczy: 2021-04-01 do 2023-03-31
Movement is a central attribute of life and a key feature in many technological processes. While artificial motion is typically provided by macroscopic engines powered by internal combustion or electrical energy, movement in living organisms is produced by machines and motors of molecular size that exploit the energy of chemical fuels at ambient temperature to generate forces and ultimately execute functions.
In the past two decades, the progress in several areas of chemistry, together with an improved understanding of biomolecular machines, has led to the development of a large variety of wholly synthetic molecular machines. Although these systems have the potential to bring about radical innovations in several areas of technology and medicine, a significant research effort still needs to be done to make molecular devices that can effectively and continuously convert energy from a source into directed motion, and use such motion to carry out a useful task.
The goal of the LEAPS project is to make new prototypes of molecular motors powered by light energy, and to use them to perform functions that include controlled transport of molecules at the nanometer scale, and mechanical actuation at the macroscopic scale. These systems are rationally designed on the evolution of previously reported working prototypes, and are based on synthetically affordable compounds.
The demonstration of such functionalities would be a landmark accomplishment in chemistry and nanoscience, and open up stimulating scenarios in nanotechnology, materials science, and nanomedicine. On the one hand, the development of artificial nanomotors that can use light energy to displace molecules can lead to radically new routes for solar energy conversion and medical phototherapies. On the other hand, devising novel photosensitive materials capable of macroscopic mechanical actuation has evident technological significance in fields such as robotics and prosthetics. Reaching these goals will constitute significant steps forward towards the real-world exploitation of chemical systems that, until just a few years ago, were considered no more than laboratory curiosities.
In the past two decades, the progress in several areas of chemistry, together with an improved understanding of biomolecular machines, has led to the development of a large variety of wholly synthetic molecular machines. Although these systems have the potential to bring about radical innovations in several areas of technology and medicine, a significant research effort still needs to be done to make molecular devices that can effectively and continuously convert energy from a source into directed motion, and use such motion to carry out a useful task.
The goal of the LEAPS project is to make new prototypes of molecular motors powered by light energy, and to use them to perform functions that include controlled transport of molecules at the nanometer scale, and mechanical actuation at the macroscopic scale. These systems are rationally designed on the evolution of previously reported working prototypes, and are based on synthetically affordable compounds.
The demonstration of such functionalities would be a landmark accomplishment in chemistry and nanoscience, and open up stimulating scenarios in nanotechnology, materials science, and nanomedicine. On the one hand, the development of artificial nanomotors that can use light energy to displace molecules can lead to radically new routes for solar energy conversion and medical phototherapies. On the other hand, devising novel photosensitive materials capable of macroscopic mechanical actuation has evident technological significance in fields such as robotics and prosthetics. Reaching these goals will constitute significant steps forward towards the real-world exploitation of chemical systems that, until just a few years ago, were considered no more than laboratory curiosities.
The main idea of the LEAPS project is to combine a photochromic reaction (a chemical transformation induced by light) with a self-assembling rotaxane architecture – consisting of a molecular axle threaded into a molecular ring - to achieve the light-powered unidirectional translation of the ring relatively to the axle. The compounds are designed following a minimalistic approach, that is, to incorporate all the functional elements necessary for the motor operation while keeping the structural complexity (and hence the synthetic and characterization effort) to a minimum. In the course of the project we designed and synthesized new molecular axles that form the basis for second generation light-driven molecular pumps, and use them to develop molecular machines capable of transforming light energy into continuous unidirectional rotary motion, or storing light energy in the form of unstable supramolecular intermediates. Significant spin-offs of this research occurred in the areas of: photochromic materials; synthetic, structural and dynamic aspects of mechanically interlocked molecules; molecular photoswitches; nanostructured luminescent materials. These results were published in top-tier scientific journals.
The LEAPS team has published 33 peer-reviewed articles, and a popular science book on molecular machines was realized. All these publications, including the book, are openly accessible. The project results have been presented by the research team members in more than 120 lectures and poster presentations in national/international conferences, workshops, schools and public events. Renowned experts in the field were invited to give seminars in our institute, and an international scientific workshop on “Light-activated nanostructures” (free registration) was organized in 2017, with a follow up in 2022. The "Molecular Machines Days" - a series of public events with the participation of the three Nobel Laureates in Chemistry 2016 – took place in Bologna in November 2018, and the final conference of the action was held in Ploen, Germany, at the end of 2022. See https://site.unibo.it/leaps/en for details.
Another significant achievement of the project is its contribution to the setup of a joint research laboratory between the University of Bologna and the National Research Council of Italy. This lab, called Center for Light Activated Nanostructures (CLAN), aims at becoming a center of excellence for research in photochemical nanosciences in Europe. Visit https://centri.unibo.it/clan/en.
The LEAPS team has published 33 peer-reviewed articles, and a popular science book on molecular machines was realized. All these publications, including the book, are openly accessible. The project results have been presented by the research team members in more than 120 lectures and poster presentations in national/international conferences, workshops, schools and public events. Renowned experts in the field were invited to give seminars in our institute, and an international scientific workshop on “Light-activated nanostructures” (free registration) was organized in 2017, with a follow up in 2022. The "Molecular Machines Days" - a series of public events with the participation of the three Nobel Laureates in Chemistry 2016 – took place in Bologna in November 2018, and the final conference of the action was held in Ploen, Germany, at the end of 2022. See https://site.unibo.it/leaps/en for details.
Another significant achievement of the project is its contribution to the setup of a joint research laboratory between the University of Bologna and the National Research Council of Italy. This lab, called Center for Light Activated Nanostructures (CLAN), aims at becoming a center of excellence for research in photochemical nanosciences in Europe. Visit https://centri.unibo.it/clan/en.
Unlike the molecular axle of the first generation of pumps (Nat. Nano. 2015), the axles developed in the first period of the LEAPS project can be functionalized while maintaining their photoinduced pumping functionality (Angew. Chem. 2019, 2020; Chem. Eur. J. 2021; JACS 2021). Building on these results, the construction of autonomous light driven rotary motors based on catenanes was achieved. Moreover, it was shown that macrocyclic rings can be transferred and stored in a molecular reservoir under light irradiation to yield a non-equilibrium structure. This result is highly significant because it unveils a new and unconventional route to convert the energy of light (potentially, sunlight) into chemical energy and store it as such in a nanoscale device (publication in preparation).
A key scientific result of the project is a detailed investigation of the mechanism by which the molecular pumps utilize the energy of light to move directionally in a dissipative non-equilibrium regime. The efficiency of the system was measured, and guidelines to optimize the performance in terms of energy conversion and storage were identified (Nat. Nano. 2022). These experiments represent an important step forward towards understanding the non-equilibrium operation of dynamic molecular-based systems that are at the base of life. The new molecular pumps were modified for incorporation in membranes and in polymers. In the latter case, in particular, polymer gels with photoswitchable properties - and in particular the ability to convert and store light energy into potential energy of the material – were prepared and investigated.
Another remarkable result of the project is the demonstration that the ring shuttling motion in rotaxanes can lead to new and potentially useful functions, such as the transfer of chemical information between two distant sites (PNAS 2018), the control of mechanical chirality and chiral anion recognition (JACS 2019), frustrated ring-axle systems (JACS 2021), coupled rotary-translational motion (Chem 2021), and autonomous shuttling based on photocatalytic mechanisms (JACS 2022). Possibilities emerge not only for the rational design of species with tailor-made functional and structural properties, but also for the development of model systems to understand some of Nature’s most effective regulatory mechanisms, namely, allostery, proton-coupled electron transfer and enantioselective molecular recognition.
Significant progress on photoswitchable molecules and materials (Angew. Chem. 2018, JACS 2018, 2020) and on rotaxane chemistry (EJOC 2019, Chem. Sci. 2021) was also reported, and review/perspective articles on influential journals were published (AOP 2019, Chem. Rev. 2020, ACS Energy&Fuels 2021, JACS Au 2023).
A key scientific result of the project is a detailed investigation of the mechanism by which the molecular pumps utilize the energy of light to move directionally in a dissipative non-equilibrium regime. The efficiency of the system was measured, and guidelines to optimize the performance in terms of energy conversion and storage were identified (Nat. Nano. 2022). These experiments represent an important step forward towards understanding the non-equilibrium operation of dynamic molecular-based systems that are at the base of life. The new molecular pumps were modified for incorporation in membranes and in polymers. In the latter case, in particular, polymer gels with photoswitchable properties - and in particular the ability to convert and store light energy into potential energy of the material – were prepared and investigated.
Another remarkable result of the project is the demonstration that the ring shuttling motion in rotaxanes can lead to new and potentially useful functions, such as the transfer of chemical information between two distant sites (PNAS 2018), the control of mechanical chirality and chiral anion recognition (JACS 2019), frustrated ring-axle systems (JACS 2021), coupled rotary-translational motion (Chem 2021), and autonomous shuttling based on photocatalytic mechanisms (JACS 2022). Possibilities emerge not only for the rational design of species with tailor-made functional and structural properties, but also for the development of model systems to understand some of Nature’s most effective regulatory mechanisms, namely, allostery, proton-coupled electron transfer and enantioselective molecular recognition.
Significant progress on photoswitchable molecules and materials (Angew. Chem. 2018, JACS 2018, 2020) and on rotaxane chemistry (EJOC 2019, Chem. Sci. 2021) was also reported, and review/perspective articles on influential journals were published (AOP 2019, Chem. Rev. 2020, ACS Energy&Fuels 2021, JACS Au 2023).