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Polarization of Charge-Transfer Bands and Rectification in Hexadecylquinolinium 7,7,8-Tricyanoquinodimethanide and Its Tetrafluoro Analog

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journal contribution
posted on 10.08.2006, 00:00 authored by Andrei Honciuc, Akihiro Otsuka, Yu-Hsiang Wang, Samuel K. McElwee, Stephen A. Woski, Gunzi Saito, Robert M. Metzger
A Langmuir−Blodgett (LB) multilayer film of the unimolecular rectifier hexadecyl-γ-quinolinium-7,7,8-tricyanoquinodimethanide (C16H33γQ-3CNQ) has two distinct polarized charge-transfer bands, one at lower film pressures (28 mN m-1) with a peak at 530 nm, due to an intramolecular charge transfer or intervalence transfer (IVT); past the collapse point (32 to 35 mN m-1), this band disappears, and a new intermolecular charge-transfer band appears with peak at 570 nm. An LB multilayer film of the tetrafluoro analogue, hexadecyl-γ-quinolinium-2,3,5,6-tetrafluoro-7,7,8-tricyanoquinodimethanide (C16H33γQ-3CNQF4) shows, for all film pressures, only one IVT band with a peak at 504 nm; when sandwiched between gold electrodes, (C16H33γQ-3CNQF4 is also an LB monolayer electrical rectifier.

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