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Effects of Disorder-Induced Symmetry Breaking on the Electroabsorption Properties of a Model Dendrimer
journal contribution
posted on 2004-10-28, 00:00 authored by L. Angela Liu, Linda A. Peteanu, David J. YaronDisorder-induced symmetry breaking is studied in a model dendrimer that consists of three arms arranged
with C3 symmetry. Electroabsorption spectroscopy measurements in the accompanying paper (Bangal, P. R.;
Lam, D. M. K.; Peteanu, L. A.; Van der Auweraer, M. J. Phys. Chem. B 2004, 108, 16834) show that the
dipole moment change of the dendrimer is similar to that of the monomer, suggesting a completely symmetry-broken dendrimer with the excitation localized on one arm of the structure. In this work, we model the symmetry
breaking of the dendrimer as a function of its structural disorder. Several collections of disordered dendrimers
are created. The excited states of the dendrimer and of the three arms that make up the dendrimer are calculated
using the intermediate neglect of differential overlap/singles configuration interaction (INDO/SCI) approach.
These data are used to verify and parametrize exciton models that relate the properties of the dendrimer to
those of the arms. A binning-and-averaging procedure is introduced so that the calculated electroabsorption
properties of the dendrimer can be studied as functions of the energetic disorder in the structure. The excellent
agreement between the INDO/SCI method and the exciton models validates the latter models for symmetry-broken structures and demonstrates that diagonal disorder is the dominant form of disorder in the dendrimer.
A thorough derivation of the electroabsorption spectrum for C3-symmetric molecules indicates that the dipole
moment change ratio between the dendrimer and the arm is a sensitive measure of disorder and symmetry
breaking. This ratio is 1/
in the absence of disorder, 1/2 at intermediate disorder, and 1 at large disorder.
These results indicate that the experimental dendrimer sample is symmetry-broken.
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latter modelselectroabsorption propertieselectroabsorption spectrumElectroabsorption PropertiesdisorderSeveral collectionsexciton models validatesparametrize exciton modelsmodel dendrimermoment changemoment change ratiob 2004dendrimer sampleC 3Electroabsorption spectroscopy measurementsC 3 symmetryINDO
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