Tan, Osbert and Clark, S.J. and Szablewski, Marek and Cross, G.H. (2010) 'Understanding the optical spectroscopy of amphiphilic molecular rectifiers : a density functional approach.', Journal of chemical physics., 133 (24). p. 244702.
We present results of first principles density functional theory calculations of the electronic and atomic structural properties of model Z-type Langmuir–Blodgett (LB) layers comprising amphiphilic quinolinium tricyanoquinodimethanide (Q3CNQ) chromophores. We find that the chromophore electronic ground state is not as clearly “zwitterionic” as required by models to explain electrical rectification purportedly seen in such systems. The computed visible region transitions are not what have been assumed to be the intervalence charge transfer bands seen in the visible region of molecules in Z-type LB films. Our own LB deposition and spectroscopic studies suggest that almost all visible region features previously seen may be ascribed to aggregates. The calculated lowest energy electronic excitation between HOMO and LUMO levels, which is located in the near infrared region, has a transition moment aligned approximately 9° off the molecular long axis, and has a normalized oscillator strength of 1 order of magnitude higher than those of the visible region transitions. This most dominant feature has been neglected from discussions of Langmuir–Blodgett layer rectification but our own deposition studies show no sign of this feature, indicating that the structure of the modeled system differs from that of typical experimental structures. The model indicates that such idealized LB layer structures cannot confidently be invoked to explain their experimental optical or electrical properties.
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|Publisher Web site:||http://dx.doi.org/10.1063/1.3516177|
|Publisher statement:||© 2010 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in Tan, Osbert and Clark, S.J. and Szablewski, M. and Cross, G.H. (2010) 'Understanding the optical spectroscopy of amphiphilic molecular rectifiers : a density functional approach.', Journal of chemical physics., 133 (24). p. 244702 and may be found at http://dx.doi.org/10.1063/1.3516177|
|Record Created:||03 Aug 2011 11:20|
|Last Modified:||26 Mar 2013 16:11|
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