The BODIPY scaffold as a core chromophore for extended, oligomeric, and helically chiral π-systems

• Applicant: Professor Dr. Daniel B. Werz
• Subject Area: Organic Molecular Chemistry - Synthesis and Characterisation
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 512131428

In this project, novel fluorophores based on the BODIPY motif will be synthesized and investigated. Previous work by the group has shown that simple oxidation reactions can be used to construct oligomeric dyes with improved properties. Bridging ethano units or benzannulations were used.In a first work package, BODIPYs substituted by α-amino groups are to be used in order to obtain BODIPYs substituted with α-chlorine by means of the Buchwald-Hartwig reaction via nitrogen-bridged BODIPY dimers. These are said to undergo ring closure at the β-position under oxidative conditions to form the bridging pyrrole system. The strategy developed in this way is to be expanded in order to arrive at analogous oligomeric systems. Unsymmetrical BODIPY monomers, which carry a chlorine substituent on the one hand and an amino substituent on the other hand, are to be used here. The formation of linear as well as cyclic systems is conceivable, which should then be oxidized to fully conjugated π systems. As an alternative to direct oxidation, there is also the possibility of stiffening the system by reaction with aldehydes in the β-position, so that after further oxidation BODIPYs linked via annulated pyridine systems should be obtainable. The photophysical and structural properties of these compounds will be studied in detail.The second work package deals with the construction and photophysical investigation of helical π-systems based on several BODIPY subunits. A separation into enantiomers or an enantioselective construction of such helical-chiral compounds should make it possible to emit circularly polarized light (cpL) with comparatively high glum values. The synthetic idea is based on first generating β-linked BODIPY oligomers with a bridging methylene unit. Subsequently, an oxidation should take place via the remaining free β'-position, which generates a bridging five-membered ring with the formation of a C C bond. This special geometric arrangement should provide configurationally stable helical molecules from as little as four subunits. A strategy that transfers central chirality at the boron center into helical chirality should help to generate P- or M-helical chiral species in a targeted manner. In addition, it is to be investigated whether desymmetrization of the helix, e.g. by attaching a terminal electron donor, increases the cpL efficiency via charge transfer or FRET effects.

• DFG Programme: Research Grants
• Co-Investigator: Professor Dr. Christoph Bannwarth