CHIRAL ELECTROCHEMISTRY IN IONIC LIQUIDS

This thesis has been initially conceived as a study of molecular electrochemistry and electrocatalysis in ionic liquids, emerging media for safe and environmentally friendly chemical and electrochemical processes, particularly focusing on the combined effects of the ionic liquid molecular structure and the nature of the electrode surface, and considering two model processes: • the electroreductive cleavage of the carbon-halogen bond in organic halides, of high interest in the synthetic, analytical and environmental fields; • the electrooxidative coupling of thiophene-based monomers, resulting in electrodeposition of conducting films for applications in photovoltaic, optoelectronic and sensor devices. Both processes are thus of great applicative interest and, at the same time, two convenient model cases for electron transfer studies in ionic liquids, one reductive (via radical anion) and one oxidative (via radical cation), on which the cation and the anion of the ionic liquid should be more determining, respectively. However, the 3-year research results actually went well beyond these initial targets, with the discovery of the outstanding properties of inherently chiral electroactive thiophene-based oligomers, on which we then concentrated most of our efforts. In particular: • electrooligomerization in ionic liquids of "inherently chiral" thiophene-based monomers developed by Professor Sannicolò's partner group afforded the preparation of enantiopure chiral electrodes of new concept and unprecedented enantiodiscrimination ability, resulting for the first time in a neat separation of voltammetry peaks for the enantiomers of a series of different chiral probes, also of pharmaceutical interest, in different media and operating conditions; • such inherently chiral electroactive oligomers turned out to be mostly cyclic, idealizing chiral conducting polymers without ends, and displaying a pool of extraordinary properties, both as racemates (promising performance in organic solar cells, photoactivity, electrochromism, possibility to complex other semiconductors, outstanding oligomerization ability...) and as enantiopure antipodes (chirality tunable with electric potential, unprecedented enantiodiscrimination ability as electrodes, circularly polarized luminescence, possibility of preparation as self-supported membranes...). Such properties prompted a patent application for the new molecule class. Furthermore, having verified the general validity and effectiveness of the inherent chirality concept, and considering our concern for ionic liquid media, we have started, again in cooperation with Professor Sannicolò's group, a further research line, aimed to the implementation of inherent chirality in new-concept ionic liquids, with the target of obtaining new, attractive media for chemical and electrochemical processes, possibly of cheap and simple synthesis, affording safe, mild and environmentally friendly operating conditions, intrinsic to the ionic liquid class, combined with powerful chirality manifestations. Three approaches, all based on the implementation of inherent chirality in the ionic liquid cation, are being developed and compared. As a valuable ancillary research product, a very simple "Egg of Columbus" protocol has been developed, providing an effective solution to the important issue of halide impurity removal from ionic liquid media. Most of the present research has been supported by Fondazione Cariplo (Grants No. 2011-0417 and No. 2011-1851)