# Dual Circularly Polarized Luminescence from Chiral Boron‐Embedded Polycyclic Aromatic Hydrocarbons

## TL;DR

Scientists created chiral boron-based molecules that emit dual circularly polarized light, with properties that change based on their environment.

## Contribution

A new strategy for generating responsive chiroptical functions using dynamic coordination in chiral boron-PAHs is established.

## Key findings

- Anthracene-fused boracyclic derivatives display dual CPL due to excited-state dissociation of the P═O⋯B bond.
- Bond cleavage converts point chirality into C−B axial chirality in these compounds.
- Solvent properties influence CPL behavior, with some derivatives showing high quantum yields and red-shifted emission.

## Abstract

Reversible coordination bonds between boron and heteroatoms endow boron‐based π‐conjugated frameworks with dynamic functionality, as interconversion between tri‐ and tetracoordinate boron centers induces pronounced changes in both molecular geometry and electronic structure. In this study, we synthesized a series of chiral boron‐embedded polycyclic aromatic hydrocarbons featuring an asymmetric boron center intramolecularly coordinated by a proximal P═O moiety. The resulting tetracoordinate enantiomers exhibit high configurational stability, enabling optical resolution by chiral HPLC. Notably, among the compounds, anthracene‐fused boracyclic derivatives display dual circularly polarized luminescence (CPL) arising from excited‐state dissociation of the intramolecular P═O⋯B bond, a process whose extent varies depending on the degree of π‐extension. In these systems, bond‐cleavage converts point chirality in the tetracoordinate state into C−B axial chirality in the tricoordinate state. Taking advantage of the intrinsically superior photophysical properties of tricoordinate boranes, one derivative exhibited CPL with a high quantum yield, while another displayed red‐shifted CPL extending to the deep‐red region. Furthermore, the dynamic P═O⋯B coordination is highly sensitive to hydrogen‐bonding ability and polarity of solvent, thereby giving rise to solvent‐dependent dual CPL behavior. These findings establish a new strategy for exploiting reversible coordination in chiral boron‐PAHs to access responsive chiroptical functionalities.

Boron‐embedded polycyclic aromatic hydrocarbons featuring an asymmetric boron center coordinated by a proximal P═O group were synthesized. Anthracene‐fused boracyclic derivatives show dual circularly polarized luminescence (CPL) arising from excited‐state P═O⋯B dissociation, which converts point chirality into C−B axial chirality. Their dual emission behavior responds to solvent hydrogen‐bonding ability and polarity, and some derivatives exhibit high quantum yields and red‐shifted CPL.