High-pressure photochemistry of furane crystal

The role of light absorption in triggering the high-pressure reaction of solid furane is investigated. When the sample is irradiated with the 458.0-nm line of an Ar+ ion laser the reaction is found to occur just above 3 GPa, well below the pressure value (10 GPa) where it takes place without irradiation. The pressure threshold of the transformation increases as the excitation line is shifted to the red. The analysis of the pressure evolution of the UV-VIS absorption spectrum allows us to identify the injection mechanism as a two-photon absorption process to the lowest excited states of furane. The aromatic ring opening shows, in this case, additional reaction paths with respect to the purely pressure induced reaction, as attested by the presence of CO2 and by the larger amount of carbonyl groups found in the recovered product. These results suggest the ring opening mechanism to be mainly controlled by the relative molecular orientation both in the disordered phase IV and in the ordered phase III. (C) 2003 American Institute of Physics.