Structure and dynamics of radicalized hydrocarbon derivatives included in, perhydrotriphenylene single crystals

The radical obtained by gamma-irradiation of the nonadecan-10-one/perhydrotriphenylene (10-NDO/PHTP) inclusion compound has been studied by EPR spectroscopy. The radical is formed by removal of one of the protons in the alpha position to the carbonyl group and the unpaired electron spin is coupled to the alpha proton and to two equivalent beta protons. The hyperfine (hf) coupling constants vary slowly on lowering the temperature until an abrupt change occurs at T = 150 K. The radical reorients quickly on the PR timescale inside the PHTP channels. The reorientational correlation time tau(r) is obtained from the,linewidth values and it is found to be shorter than the tau(r) value measured previously for the same radical included in urea. The EPR spectrum changes in the timescale of weeks and after two months displays the presence of an additional hf coupling with a pair of equivalent protons, the other spectral parameters being unchanged with respect to those of the freshly irradiated radical. This modification is probably due to a folding of the radicalized guest molecule inside the host channel.