Abstract
This short review demonstrates how MO-theoretical considerations can support the tailor-made
design of new dye scaffolds, specifically the recently introduced BOIMPY class of
fluorophores. Starting with historical and structural foundations, the influence of
canonical streptocyanines on the electronic features of diarylmethenes and rhodamines
is examined and the BODIPY scaffold is introduced as the primary structural inspiration
for our work. The attachment of five-membered ring heterocycles at the meso position of the BODIPY core enables a relaxation into a co-planar and twofold chelating
triarylmethene system. After introduction of two electron-withdrawing BF2 units, efficient rigidity is achieved since hindered rotation prevents non-radiative
dissipation of energy via excited state relaxation. Hence, a lowered LUMO level allows
the combination of a large red shift with high quantum efficiencies. The synthetic
approach to BOIMPYs is straightforward and analogous to BODIPY syntheses starting
from benzimidazole or tetrazole carbaldehydes. Cyclic voltammetric measurements prove
that BOIMPYs are able to easily accept two electrons and might act as efficient photoredox
catalysts.
Key words fluorophores - dyes - BODIPY - BOIMPY - MO considerations
