Insight into the influence of the chiral molecular symmetry on the chiroptics of fluorescent BINOL-based boron chelates

Among all the technological applications based on photonics, those based on chiroptical phenomena (particularly, circularly polarized luminescence, CPL) have special relevance, mainly owing to the higher resolution of the circularly polarized over the linearly polarized or the unpolarized light. However, the design of emitters efficiently enabling CPL is not an easy task because it is necessary to combine, in the same structure, a high fluorescence quantum yield and a high level of circular polarization in the emission. Among all the possible chemical systems that show circularly polarized luminescence, the CPL-SOMs (simple organic molecules enabling CPL) have gained exponential interest in the last years. The reason for the growing interest in these emitters lies in their potential for the development of specific CPL materials due to properties associated with their organic nature (low molecular weight, organic-solvent solubility) and their high capacity of absorbing and emitting light, which, in addition, can be adjusted by workable chemical modifications of the chromophore. However, although organic chromophores usually show bright fluorescence, their levels of circular polarization are still very small in all cases. In this regard, there is a need for systematic studies directed towards a deeper knowledge on the structural factors ruling the chiroptical behavior of CPL-SOMs. In this communication, we study and discuss the influence of the chiral symmetry point group (C₁, C₂ and D₃) on the chiroptical behavior of simple fluorescent boron chelates (BODIPY and related BOPHY analogs) to shed light on the chiroptical behavior of BODIPY-based and BODIPY-like CPL-SOMs.