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14 October 1998 Charge transfer reactions in nematic liquid crystals
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Ultrafast transient absorption studies of intramolecular photoinduced charge separation and thermal charge recombination were carried out on a molecule consisting of a 4-(N-pyrrolidino)naphthalene-1,8-imide donor (PNI) covalently attached to a pyromellitimide acceptor (PI) dissolved in the liquid crystal 4'-(n-pentyl)-4- cyanobiphenyl (5CB). The temperature dependencies of the charge separation and recombination rates were obtained at temperatures above the nematic-isotropic phase transition of 5CB, where ordered microdomains exist and scattering of visible light by these domains is absent. We show that excited state charge separation is non-adiabatic, and obtain the unexpected result that charge separation is dominated by molecular reorientation of 5CB perpendicular to the director within the liquid crystal microdomains relative to the orientation of PNI+-PI-. We also report the result of time resolved electron paramagnetic resonance studies of photoinduced charge separation in a series of supramolecular compounds dissolved in oriented liquid crystal solvents. These studies permit the determination of the radical pair energy levels as the solvent reorganization energy increase from the low temperature crystalline phase, through the soft glass phase, to the nematic phase of the liquid crystal.
© (1998) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Gary P. Wiederrecht, Michael R. Wasielewski, Tamar Galili, and Haim Levanon "Charge transfer reactions in nematic liquid crystals", Proc. SPIE 3475, Liquid Crystals II, (14 October 1998);

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