A Langmuir-Blodgett (LB) multilayer film of the unimolecular rectifier hexadecyl-γ-quinolinium-7,7,8-tricyanoquinodimethanide (C 16H33γQ-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, hexadecylγ- quinolinium-2,3,5,6-tetrafluoro-7,7,8-tricyanoquinodimethanide (C 16H33γQ-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. © 2006 American Chemical Society.
