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Optical excitations in star-shaped fluorene molecules

, : Optical excitations in star-shaped fluorene molecules. Journal of Physical Chemistry. A 115(14): 2913-2919

A detailed study of the low-energy optical transitions in two families of star-shaped molecules is presented. Both families have 3-fold rotational symmetry with oligofluorene arms attached to a central core. In one family, the core of the molecule is a rigid meta-linked truxene, while the other is a meta-linked benzene moiety. The low-energy transitions were studied both experimentally and using time-dependent density functional theory (TD-DFT). The optical transitions of these new star-shaped molecules were compared with corresponding linear oligofluorenes. Both families of star-shaped molecules showed higher absorption and fluorescence dipoles and photoluminescence quantum yields than straight chain oligofluorenes. TD-DFT calculations show that absorption takes place across the entire molecule, and after excited state relaxation, the emission results from a single arm. In both theory and experiment the transition dipole moments show an approximate n(0.5) dependence on the number of fluorene units in each arm.


PMID: 21428384

DOI: 10.1021/jp1109042

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