Single Heteroatom Fine-Tuning of the Emissive Properties in Organoboron Complexes with 7‑(Azaheteroaryl)indole Systems

The application of organoboron compounds
as light-absorbing or
light-emitting species in areas as relevant as organic electronics
or biomedicine has motivated the search for new materials which contribute
to the progress of those applications. This article reports the synthesis
of four-coordinate boron complexes based on the unexplored 7-(azaheteroaryl)­indole
ligands. An easy synthetic approach has enabled the fine-tuning of
the electronic structure of the organoboron species by modifying a
heteroaromatic component in the conjugated system. Furthermore, a
comprehensive characterization by X-ray diffraction, absorption and
emission spectroscopy, both in solution and in the solid state, cyclic
voltammetry, and computational methods has evidenced the utility of
this simple strategy. Large Stokes shifts have been achieved in solid
thin-films which show a range of emitted light from blue to orange.
The synthesized compounds have been used as biocompatible fluorophores
in cell bioimaging.