Dissipative systems driven by activated carboxylic acids

This thesis presents the results of my PhD research, which focused on the employment of Activated Carboxylic Acids (ACAs) as chemical fuels to drive the operation of a series of dissipative systems. This thesis falls within the field of Systems Chemistry, which aims to design complex artificial (de novo) systems of interacting and interconverting molecules and to study the emergent properties deriving from them. In Chapter 1 a general introduction to the field is given, with a particular focus on natural systems and how they managed to inspire the design of artificial life-like ones. The key concepts at the base of the operation of natural systems are discussed, as well as some of the strategies employed so far to design systems that dissipate energy to provide a certain output. Based on their exploited functionality, such systems have been divided into motors, pumps, and self-assemblable molecules. A series of examples for each category is illustrated, drawing the attention on the energy source that drive their operation. Finally, ACA-driven artificial systems are discussed with an initial focus on the state of the art of the ACAs topic. Among all the examples, some artificial life-like systems are highlighted both for the motor and pump, and self-assembly category pointing out their operational mechanisms. The following Chapters focus on the research I carried out during my PhD. The main goal has been to broaden the applicability of the ACAs both in organic solvents and in water. Chapter 2, carried out in collaboration with Prof. Gianfranco Ercolani, shows the design of two biphenyl amines and how an ACA, namely 2-cyano-2-phenylpropanoic acid, can be used to temporally control the conformational freedom around the CC bond connecting the two aromatic rings. In Chapter 3 is described the first example in which two orthogonal fuels of different nature, i.e. an ACA and light, have been used to drive the translocation of a metal cation between different supramolecular receptors. Interestingly, the combination of the two stimuli guarantees a finer time-control of the translocation process. Chapter 4 and 5 deal with the use of ACAs to control over time the population of a dynamic library of imines. Firstly, the focus has been placed on the temporal control of the composition of the library in the dissipative state. Then, in collaboration with Prof. Gianfranco Ercolani, the attention was shifted on how the dynamic library can store the energy deriving from the fuel-to-waste conversion and how the energy storage can be modulated by changing solvent. Finally, Chapter 6 illustrates the results obtained during my six-months stay in Munich hosted by the Boekhoven’s group. In this chapter an ACA, namely nitroacetic acid, has been employed to control the lifetime of coacervate-based droplets in water, providing a robust platform for examining early protocell-like systems.