Translate 
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.
Highlights
Introduction and General ConsiderationsFluorescent dyes have become indispensable in todays biological, biophysical, and medical research
Since an analysis of the frontier orbitals of a BODIPY reveals that the BF2 unit has practically no coefficients in either the HOMO or the LUMO, we considered the following design for more red-shifted BODIPY derivatives (Figure 5): in a thought experiment, we first removed the BF2 unit from a meso imidazole-substituted BODIPY of type 1
Like many other important dyes and fluorophores, pyrrolederived BODIPYs can be traced back to the structural motif of canonical cyanines, which Walter König first investigated over 100 years ago
Summary
Fluorescent dyes have become indispensable in todays biological, biophysical, and medical research. The CDD plots underscore that both meso-units, benzimidazole, and tetrazole, play only a minor role in the charge redistribution process upon S1 ← S0 excitation This is an intriguing fact since the introduction of these coordinating bridging units introduces a pseudo threefold rotational axis perpendicular to the molecular plane allowing (Aza-)BOIMPYs to be considered as fusion structures of two BODIPY analogs with a common hemisphere (benzimidazole or tetrazole). Density functional theory and second-order coupled cluster approaches to elucidate the excited state behavior Their studies confirmed the intrinsic push–pull quality of the BOIMPY motif and could verify the absence of a charge transfer process, an exclusion which is usually mandatory for a dominant radiative decay and a strong fluorescence. The studies suggested further structural modifications, mainly with acetylene units at the pyrrole moieties, for which excitation energies far in the near-infrared (NIR) region were computationally predicted Five years after their introduction, BOIMPYs attracted the interest of the biophysical community. An optical penetration up to 8 mm was demonstrated allowing the visualization of tumor xenografts and deepseated abdominal metastatic tumors with excellent photostability
Sign-in/Register to view highlights & summary 
Paper version not known (
Free)
Published Version
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
