Dynamics of discotic methoxy triphenylene molecules from quasielastic neutron scattering and molecular dynamics simulations

Quasielastic neutron scattering measurements on hexakismethoxytriphenylene (HMT) shows molecular motion at timescales of 0.1 and 7.3 ps at 370 K. Deuteration of the methoxy tails, suppresses the signal for the slower motion, whilst the signal from the more rapid motion of the triphenylene cores persists. A molecular dynamics simulation on an isolated model of 4 HMT molecules reveals the slower methoxy motion to be a torsion of the whole methyl group around the core to oxygen bond. The faster motion is due to lateral sliding of the cores with respect to each other. A harmonic core-motion arising from tilting of the disks in the simulation may correspond to a strongly damped motion seen in the experimental data. (C) 2003 Elsevier Science B.V. All rights reserved.