The freezing behavior and the cluster formation in the liquid and supercooled-liquid state of monodeuterated 2-cyclooctylamino-5-nitropyridine have been studied by deuteron magnetic resonance and relaxation. The results show that the molecular dynamics is both polydispersive and non-Arrhenius-like. The data can be described by a correlation function of the stretched-exponential type and a Vogel-Fulcher-type temperature dependence of the mean correlation times. The existence of polydispersivity already in the liquid state may be interpreted in terms of molecular clusters of different sizes. The mean size of these clusters and their temperature dependence have been estimated by a combination of deuteron NMR and proton self-diffusion data. Nonlinear-optical data further suggest that molecular chains in the clusters are arranged in an antiparallel manner.

• Received 12 November 1991

DOI:https://doi.org/10.1103/PhysRevB.45.7697