Préparation de réseaux organiques covalents monocristallins par polymérisation de composés polynitroso aromatiques

Modular construction is an emerging strategy that allows the preparation of materials ordered at the atomic scale. It consists of the programmed assembly of molecular subunits that interact via properly selected reactive sites. The application of this strategy has already produced materials with remarkable properties: in particular, covalent organic networks in which carbon and other light atoms are linked by covalent bonds. Although materials assembled by non-covalent interactions can be prepared in the form of macroscopic single crystals in this manner, this was not possible in the case of covalent organic networks. To fill this gap, we chose to study reversible polymerization reactions taking place by an addition mechanism. Indeed, the initial hypothesis of this thesis assumes that such a process emulates the classic phenomenon of crystallization – governed by non-covalent interactions – and thus favors the formation of single crystals of large dimensions. To test the validity of this hypothesis, we opted to study the polymerization of polynitroso compounds since the dimerization of nitrosoarenes is reversible and proceeds by addition.  We began by thoroughly reviewing the literature on the dimerization of nitrosoarenes. Drawing on this mass of data, we then designed a series of polynitroso compounds with the potential to form organic two- and three-dimensional covalent organic networks. The thermodynamic parameters associated with their polymerization were estimated through the study of model mononitroso compounds. Afterward, we synthesized the various polynitroso compounds targeted by our study. To achieve this, we had to develop a new methodology for the synthesis of poly (N-arylhydroxylamines), the direct precursors to polynitroso compounds. With these compounds in hand, we then studied the polymerization of polynitroso compounds. Despite practical difficulties arising from the spontaneous polymerization of such compounds, we were able to identify favorable conditions for the generation of highly crystalline covalent organic networks. Thus, several new three-dimensional covalent networks were produced as single crystals of sizes ranging between 30 µm and 500 µm, confirming the validity of our hypothesis. It was therefore possible to solve the structure of these crystals by single-crystal X-ray diffraction, which had never been possible in the past for this kind of material. These crystals are remarkably uniform in sizes and their individual constituent polymer show extremely high molecular weights (1014-1017 g/mol). However, the polymerization of the majority of polynitroso compounds studied leads instead to amorphous solids or crystalline solids consisting of the monomeric form of these compounds. Other model nitroso compounds were prepared in an attempt to explain this behavior, and hypotheses were based on the study of their behavior. Lastly, the structure of several polynitroso compounds that crystallized as monomers were analyzed in detail by X-ray diffraction.  Our strategy, which uses monomers having the ability to polymerize spontaneously by reversible addition, seems promising for the preparation of novel monocrystalline covalent organic networks from polynitroso compounds or other monomers of similar nature. In addition, the results presented in this thesis illustrate how predictably ordered networks, both covalent and non-covalent, can be built using a single modular strategy.

Keyphrases: covalent organic networks, polynitroso compounds, polymerization, dimerization, modular construction, single crystal, crystallography