Symmetry
Lowering in Triindoles: Impact on the Electronic and Photophysical
Properties
- Publication date
- Publisher
Abstract
The electronic and photophysical
properties of 6,11-dihydro-5<i>H</i>-diindolo[2,3-<i>a</i>:2′,3′-<i>c</i>]carbazole, an asymmetric
cyclic dehydrotrimer of indole, have been explored and compared to
its symmetric analogue, 10,15-dihydro-5<i>H</i>-diindolo[3,2-<i>a</i>:3′,2′-<i>c</i>]carbazole (triindole),
a well-known high hole mobility semiconductor. To this purpose, we
use a joint experimental and theoretical approach that combines absorption
and emission spectroscopies, cyclic voltammetry, and spectroelectrochemistry
with DFT calculations. Lowering the symmetry of the triindole platform
causes a red-shift of the absorption edge and emission maxima and
improved the fluorescence quantum yield. Cyclic voltammetry and spectroelectrochemistry
reveal the reversible nature of the two observable oxidation processes
in the alkylated asymmetric triindoles together with an increase in
the stabillity of their oxidized species. On the other hand, the insertion
of alkyl groups on the nitrogen atoms results in a further fluorescence
enhancement although larger reorganization energies are found. DFT
and time-dependent (TD-DFT) calculations successfully support the
experimental data and aid in the understanding of the tuning of the
physicochemical properties of the triindole platform upon symmetry
lowering toward their incorporation in electronic devices