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C*-BODIPYs: Exploring a new strategy to transfer chirality towards BODIPY chiroptics.
1 , 1 , 1 , 1 , 2 , 3 , 3 , 2 , * 1 , 1
1  Dpto. Química Orgánica I. Facultad de Ciencias Químicas. Universidad Complutense de Madrid. Ciudad Universitaria s/n, 28040 Madrid, Spain
2  Departamento de Química Física, Universidad del País Vasco UPV/EHU, Aptdo. 644, 48080 Bilbao, Spain.
3  Department of Chemistry, San José State University, One Washington Square, San Jose, CA 95192-0101, USA.


The development of new chiral chromophoric systems able to emit circularly polarized light (aka circularly polarized luminescence or CPL) has attracted a great deal of attention due to their application in the improvement and potential development of multiple photonic technologies such as 3D optical displays, biological probes, CPL lasers or light-emission systems for asymmetric photosynthesis. Among all the chromophoric systems enabling CPL, simple organic molecules (SOMs) have the advantage of showing high and easily tunable absorption and fluorescence, together with easy manipulation for manufacturing processes. Particularly, BODIPYs (boron dipyrromethenes) are outstanding chromophores owing to their excellent and tunable photophysical properties. Unfortunately, SOMs usually possess weak CPL activities, compared to other systems such as lanthanides or supramolecular aggregates.

The achievement of chirality in SOMs towards CPL emission is not an easy task. In many cases, the chiral perturbation of the chromophore comes together with a distortion of the structure, leading to a decrease in the fluorescence (for example, it has been observed for helicenes). In this sense, the boron atom in BODIPYs offers a privileged position for the chiral perturbation of the chromophore without altering its photophysical signature, as reported by us for O-BODIPYs having atropoisomeric BINOL attached to the boron.

We report in this communication an unexplored strategy to transfer chirality to the BODIPY chromophore, based on attaching chiral carbons directly to the boron atom, that is, C*-BODIPYs. The starting hypothesis is that the closer proximity of the chiral center to the BODIPY core will achieve a more efficient chiral perturbation over the chromophore.

Keywords: BODIPY; CPL