Electronic coupling responsible for energy transfer in columnar liquid crystals
Electronic coupling is the driving force for energy transfer in molecular materials and consists of several components. We determine the strength of dipolarrmultipolar coupling and coupling due to orbital overlap for excitation transport in triphenylene columnar liquid crystals. We use time-resolved fluorescence spectroscopy and computer simulations. The fit of the experimental and simulated fluorescence decays reveals that the transfer process is dominated by short range interactions .multipolar and orbital overlap but the contribution of long range dipolar interactions cannot be neglected. q 1999 Elsevier Science B.V. All rights reserved.
Photophysical Properties of Discotic Dibenzopyrenes
Abstract The photophysical properties of three discogenic dibenzopyrenes substituted by eight pentyloxy (O5DPB), heptyloxy (O7DBPP) or decyloxy (O10DBP) side chains are studied in solution and thin films. It is shown that the absorption and fluorescence spectra of the columnar mesophases are clearly distinguishable from those of the corresponding crystalline phases, allowing the study of phase transitions. Thus, it is found that the shorter the lateral chain length, the slower the crystallisation process. For O5DBP, the supercooled mesophase is stable over a period of at least one year; it crystallises after cooling below the glassy transition. Such a behaviour gives rise to temperature con…