The major objective of this project is sensitivity enhancement in magnetic resonance and more especially in MRI (Magnetic Resonance Imaging). The use of parahydrogen constitutes a promising method. This is because a hydrogenation reaction carried out with para-enriched gaseous hydrogen (di-hydrogen possesses two spin isomers: ortho and para) leads to a product, the resonances (those arising from hydrogenation) of which are enhanced by several orders of magnitude (greater is the enrichment, greater is the enhancement). In fact, these resonances show up generally in the form of antiphase doublets and are not directly usable for the sensitivity increase of NMR (Nuclear Magnetic Resonance) and MRI experiments. We are the only French group working on this subject and we have shown recently that, under particular experimental conditions, it was possible to obtain a net polarization leading to in-phase resonances. In this case, the term “hyperpolarization” becomes meaningful. The original part of the present project rests on this new approach which will have to be assessed by numerous NMR spectroscopy experiments. In particular, transfer of this hyperpolarization toward molecules dedicated to specific applications will be envisioned by means of intermolecular nuclear Overhauser effect. This methodology will rest on new substrates prone to be hydrogenated (initiators) and to appropriate targets (dedicated molecules). Both types of molecules will be synthesized and thoroughly tested. A parahydrogen enrichment unit (for an enrichment of about 100%) will be constructed. In a more prospective way, we shall try to devise vessels in which the para-ortho conversion is slowed down. Besides MRI of materials and in vivo MRI, applications will concern i) the sensitivity improvement of NMR in weak magnetic fields and, more tentatively, of nitrogen-14 Nuclear Quadrupole Resonance (NQR; magnetic resonance in zero magnetic field for indentifying nitrogen containing molecules), ii) the depolarization as a function of the NMR magnetic field value (relaxometry).

Ce projet a pour but de renforcer le domaine prioritaire des Nanosciences-Nanotechnologies dans les collaborations scientifiques entre les Universités Louis Pasteur de Strasbourg et Henri Poincaré de Nancy. A ce titre, il vise à la complémentarité des approches de type bottom-up et de type top-down avec pour point de rencontre l’échelle du nanomètre. Différents domaines de la physique et de la chimie, ainsi que leur inter-connexion, sont alors concernés avec des longueurs caractéristiques de 500nm pour la plasmonique, 100nm pour le nanomagnétisme et de 10nm à 1nm pour les nanotubes de carbone et les matériaux moléculaires.

The use of organometallic or –semimetallic 'ate complexes in organic synthesis has developed unequally. If borates, aluminates, zincates or cuprates already play an important role, other 'ate complexes have met a more recent (e.g. magnesiates or manganates, for example) or even nonexistent (e.g. calciates) development. With two metals and several ligands organized around the central metal, the 'ate complex has a typical and adjustable reactivity. So, depending on its nature, the 'ate complex behaves in different ways towards a substrate: the central metal of the 'ate complex can react either by electron transfer, or as a nucleophile, or even by transferring one of its ligands. Because of the expertise of the project partners in the field of bimetallic bases, the latter has particularly drawn their attention since the 'ate complex can play the role of a base by giving a ligand. The synthesis of functionalized aromatics, and in particular heterocycles, is an important challenge due to the numerous applications of such structures. Although there has been clear progress in the use of classical bases to deprotonate such substrates, many problems remain and justify the development of new tools proceeding at room temperature, tolerating the presence of functional groups, allowing different regioselectivities, and giving adjustable reactivities to the deprotonated rings. Our aim is therefore to develop activated 'ate compounds by varying the central metal and adding adequate metal ligands to promote chemo- and regioselective deprotonation of aromatics and heteroaromatics, notably those for which classical bases are not much suitable, and to study the subsequent functionalization. A better understanding of the behaviour of 'ate compounds will be obtained with the help of advanced NMR experiments (collaboration with G. Hilmersson, Sweden), XRay analyses (A. Wheatley, UK) and theoretical calculations (collaboration with M. Uchiyama, Japan). This will be particularly useful to study the behaviour of mixed 'ate complexes that will be used in asymmetric synthesis. In addition to the potential use for the access to targets of biological interest, the development of these methods will allow the synthesis of building blocks for various applications such as material science ans supramolecular chemistry.