6533b827fe1ef96bd12870d9

RESEARCH PRODUCT

Isolation of the CH3˙ rotor in a thermally stable inert matrix: first characterization of the gradual transition from classical to quantum behaviour at low temperatures

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International audience; Matrix isolation is a method which plays a key role in isolating and characterizing highly reactive molecularradicals. However, the isolation matrices, usually composed of noble gases or small diamagnetic molecules,are stable only at very low temperatures, as they begin to desegregate even above a few tens of Kelvin.Here we report on the successful isolation of CH3 radicals in the cages of a nearly inert clathrate–SiO2matrix. This host is found to exhibit a comparable inertness with respect to that of most conventionalnoble gas matrices but it is characterized by a peculiar thermal stability. The latter property is related to thecovalent nature of the host material and gives the opportunity to study the confined radicals from a fewdegrees of Kelvin up to at least room temperature. Thanks to this advantage we were able to explore withcontinuity for the first time the CH3 rotor properties by electron paramagnetic resonance spectroscopy,starting from the quantum rotations which are observable only at the lowest temperatures (T E 4 K), goingthrough the gradual transition to the classical motion (4 K o T o 30 K), and ending with the properties ofthe fully classical rotor (T 4 30 K). The method of isolation presented here is found to be very effectiveand promising, as it is expected to be applicable to a large variety of different molecular radicals.