Optical excitations in star-shaped fluorene molecules

J Phys Chem A. 2011 Apr 14;115(14):2913-9. doi: 10.1021/jp1109042. Epub 2011 Mar 23.

Abstract

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Fluorenes / chemistry*
  • Luminescence
  • Models, Molecular
  • Molecular Structure
  • Quantum Theory

Substances

  • Fluorenes