New stablilized Radicals for new applications – NewRaP
Design and synthesis of new organo-silylated molecules as precursors of sulfur-centered radicals: the main difficulty to overcome concerns the stability of the radical precursor functions during the synthesis of the materials (direct synthesis route).
Design, synthesis and characterization of novel organic-inorganic hybrid materials incorporating radical precursors: it is necessary to adjust the protocols for the material synthesis for each precursor in order to obtain structured materials of controlled pore sizes.
Study of the behavior of radical species within nanostructured hybrid materials by EPR: the difficulty is to set up appropriate conditions for EPR analysis.
Study of factors influencing the lifetime of radicals in a confined space, modulation of the latter.
Relationship radical nature / magnetic properties : the discovery of «organic magnets« opened the way to new applications. The aim here is to study the magnetic properties of nanoconfined stabilized radicals.
In order to develop knowledge of the magnetic properties of radicals functionalized materials, we first prepared materials containing stable and known radical. Different silicas were synthesized by varying several factors (silica source, nature and quantity of radicals) to eliminate all potential sources of magnetic contamination. The SQUID magnetometer measurements are in progress.
The first results of RPE at low T show a significant effect on the nature of the spacer between the silica and the radical on dipolar interactions of radicals.
EPR measurements showed a significant increase in half-life times of arylsulfanyl radicals compared to those known in solution. A dynamic molecular modeling study highlights the importance of the structure of the monolayer on the silica surface.
Extension to radicals of a different type
1. Vibert, F.; Marque, S. R. A.; Bloch, E.; Queyroy, S.; Bertrand, M. P.; Gastaldi, S.; Besson, E. Chem. Sci. 2014, 5 (12), 4716.
2. Vibert, F.; Marque, S. R. A.; Bloch, E.; Queyroy, S.; Bertrand, M. P.; Gastaldi, S. ; Besson, E. J. Phys. Chem. C 2015, 119(10), 5434.
This research project aims to develop a new family of organic magnets based on "unusual stable radicals". To reach this goal, the effect of nanoconfinement will be used to stabilize radicals and to increase their lifetime. The behavior of a radical in a confined space has been little investigated. Structured mesoporous silicas will be taken as model. Indeed, these materials have a high thermal and chemical stability and are easily functionalized.
Different precursors of sulfanyl radical will be synthesized like aliphatic or aromatic thiols, and allylic or benzylic thioethers/sulfones or diazenes. They will incorporate a trialkoxysilane group, in order to anchor them to mesoporous materials, and a radical precursor, stable throughout the material synthesis conditions. Ordered silicas will be prepared by the sol-gel process in the presence of structure-directing agents according to two different pathways: grafting or direct synthesis. Different morphologies and pore diameters will be considered. Nanostructured polysilylsesquioxanes will be prepared by self-assembly during sol-gel process.
Radical lifetime studies will be carried out on these model materials by EPR spectroscopy. First different radical traps will be used in order to validate the radical generation method and to identify unambiguously the radicals generated along the process. Then, EPR studies will be performed on the best mesoporous silicas without any radical trap for a direct observation of S-centered radicals. The silica structure will be optimized in order to increase the radical lifetime.
The magnetic properties of these various radical functionalized mesoporous silicas will be studied in collaboration with the Charles Gerhardt Institute in Montpellier.
Project coordination
Eric BESSON (Institut de Chimie Radicalaire) – eric.besson@univ-amu.fr
The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.
Partner
ICR/CNRS DR12 UMR7273 Institut de Chimie Radicalaire
Help of the ANR 204,260 euros
Beginning and duration of the scientific project:
December 2012
- 48 Months
