Fine tuning of the photochromic absorption band of heteromolecular Langmuir–Blodgett films of zwitterionic donor-π-acceptor molecules

Abstract

Mixed Langmuir-Blodgett films of Z-p-( 1 -hexadecyl-4-pyridinium)-a-cyano-4-styryldicyanomethanide (C16H33-P3CNQ) and Z-p-( 1-hexadecyl-4-quinolinium)-a-cyano-4-styryldicyanomethanide (C16H33-Q3CNQ) exhibit a single charge-transfer band that may be tuned within the range 495 to 565 nm; the films are photochromic and exhi bit second-harmonic generation.

Comparison of the structure property relationships in LB films of zwitterionic TCNQ adducts

“…There have been a number of syntheses of the c-bridged adducts reported in the literature. [2][3][4][5][6][7][8] However, for the a-bridged systems, the only successful method found by us was prolonged reaction of the appropriate N-alkylquinaldinium halide with LiTCNQ. This original method of using LiTCNQ with the quaternary salts (historically used to synthesise CH 3 (2) P3CNQ) 1 was evaluated and found to provide a relatively simple and reproducible method.…”

“…Their subsequent characterisation and Langmuir-Blodgett (LB) film fabrication have been widely reported. [2][3][4][5][6][7][8][9][10] The highly polarisable nature of these zwitterions coupled with their LB film forming properties suggest possible applications, including molecular rectification, photochromism, non-linear optics and in particular, second harmonic generation.…”

“…These films also exhibit a much greater second order susceptibility, x ð2Þ zzz 5 180 pm V 21 in 200+ layer films of C 16 H 33 (4)Q3CNQ. 5 The molecular alignment in films *norman.bell6@btopenworld.com.…”

Rectification by a Single Molecule of Hexadecylquinolinium Tricyanoquinodimethanide

“…1 is not only a multilayer rectifier, but also a monolayer rectifier, 36 by an improvement of Sambles and co-workers' original technique, 28,29 and in accord with a plausible modification of the Aviram-Ratner Ansatz. 1 The dilemma due to the previous use 28,29 of two metal electrodes with different work functions (Mg and Al) has been eliminated. 36 Although asymmetric STS currents through single halogen adatoms on a STM tip have been seen, 50 it may be claimed that 1 is the "world's smallest electronic device.…”

Molecular and nanoscale materials and devices in electronics

“…In 1985, Fujihira et al [53] measured light-induced currents through LB monolayers from molecules functionalized with donor and acceptor moieties. Since about 1990, Ashwell et al [54,55] reported on rectifying properties of LB film from the zwitterioic molecule C 16 H 33 -gQ3CNQ. The chemical structure of this molecule is shown in Fig.…”