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Proceedings Paper

Charge transfer reactions in nematic liquid crystals
Author(s): Gary P. Wiederrecht; Michael R. Wasielewski; Tamar Galili; Haim Levanon
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Paper Abstract

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.

Paper Details

Date Published: 14 October 1998
PDF: 10 pages
Proc. SPIE 3475, Liquid Crystals II, (14 October 1998); doi: 10.1117/12.326896
Show Author Affiliations
Gary P. Wiederrecht, Argonne National Lab. (United States)
Michael R. Wasielewski, Argonne National Lab. and Northwest Univ. (United States)
Tamar Galili, Hebrew Univ. of Jerusalem (Israel)
Haim Levanon, Hebrew Univ. of Jerusalem (Israel)

Published in SPIE Proceedings Vol. 3475:
Liquid Crystals II
Iam-Choon Khoo, Editor(s)

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