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Home >  Teams    > Structure and Reactivity Team for Paramagnetic Species (SREP)
Resp. Olivier Ouari

Detailed description of the SREP team

by webmestre - published on , updated on

Scientific positioning

The SREP team is working on the development of new mainly covalent radical structures in order to understand and take advantage of their unique physicochemical properties. The main field of research is based on the synthesis of free radicals (mono- and polyradical) of nitroxide type but also diamagnetic traps of nitrone type producing diagnostic radical adducts of the presence of free radicals with very short life.
The presence of one or more single electron (s) is at the origin of the paramagnetic nature of these molecules which are studied by Electron Paramagnetic Resonance (EPR). Previously, the particular properties of the unpaired electron of the aminoxyl (nitroxide) function have led to many applications in a wide range of research areas. We believe that by fine tuning the molecular and supramolecular structures of these radicals, some current limitations can be overcome and new functions will be available.
The ultimate purpose of our research is to discover new structures and functions mainly based on nitroxides and to implement them to access new devices in which the magnetic nature of the free radical can be controlled for advanced applications such as in (i) spin trapping, (ii) paramagnetic sounding, (iii) spin labeling or (iv) Nuclear Dynamic Polarization (NDP).
 
Nitroxides and dinitroxides in nuclear dynamic polarization (NDP) for NMR

Since 2005, our team is involved in several projects focused on research in PDN. The aim of these projects is to explore new high resolution NMR methods using the Dynamic Nuclear Polarization (DNP) effect which has been shown to improve the detection sensitivity of Nuclear Magnetic Resonance by several orders of magnitude (NMR).
Our work is mainly devoted to the design and synthesis of new polarization agents that are tested in solid state and liquid NMR. Very promising results were obtained with biradical bTbK (based on two nitroxides of TEMPO type nitroxides) in HR-MAS DNP ssRMN. More recently, the development of TEKPol and AMUPol have further expanded the scope of PDN applications. In this context, we are interested at the synthesis and in RPE studies of mono-and polynitroxides.

Radical traps and spin trapping

For more than 25 years our team has been interested in spin trapping and has helped to discover some of the most successful families of radical traps. A better knowledge of the process of trapping and the improvement of the spin traps was thus able to see the day. Special attention has been devoted to improving (i) the lifetime of adducts from entrapment of the superoxide anion radical, (ii) the kinetics of entrapment of the superoxide radical; and (iii) the biodistribution of spin traps in biological systems.
Recently, a new approach has been developed for the protection of spin adducts against bioreductors by selective encapsulation in cyclodextrin-type macrocycles. We are also working on a better understanding of the degradation mechanisms of spin adducts and diversify our trap families by studying new hydroethidine type(HE) fluorescent probes.

Stable radical interface/supramolecular chemistry

Our efforts have also focused for some time on the synthesis of new architectures including nitroxides using the tools of macrocyclic chemistry and supramolecular chemistry. For example in the solid phase, new nitroxide crystals having a porous nature have been developed capable of encapsulating various products such as other radicals or even fullerenes. At the same time, we are studying the subtle relationships existing in the liquid phase between certain free radicals and various macrocycles of the cyclodextrin, cucurbituril, resorcinarene type or self-assembling systems such as certain low molecular weight peptides.