Modulating lifetimes and relaxation times of phenoxyl radicals through their incorporation into different hybrid nanostructures
Résumé
The development of new open shell systems is essential for advances in spin science. In this work, we report the synthesis and characterization of three nanostructured materials, namely SBA-15 silicas, periodic mesoporous organosilica (PMOs) and lamellar polysilsesquioxanes, all functionalized with the same diazene-based precursor of phenoxyl radicals. The impact of the nature of the material, i.e. loading in radical precursor and structure, on half-lifetimes (t1/2) and relaxation times of phenoxyl radical was investigated. Although phenoxyl radicals are transient in solution, their t1/2 range from hours to years at room temperature (RT) when they are embedded in nanostructured materials. The above mentioned functionnalized materials were used to generate the corresponding phenoxyl radicals and measured their relaxation times ( and Tm) from 50 K to RT. The results were rationalized in terms of limited mobility of the radical thanks to supramolecular interactions and structure rigidity. All these data show that it is possible to design functionalized nanostructured material with radicals possessing specific electronic relaxation properties which can be of interest in fields like DNP, organic magnetism or spin qubit.