Engineering [7]helicene via peripheral boron-nitrogen Lewis pair fusion: from synthesis to cellular imaging

The judicious incorporation of main group elements such as boron-nitrogen Lewis pair motifs into π-conjugated frameworks has emerged as a powerful strategy for developing novel functional hybrid materials with significant potential for application in biological and materials chemistry. Herein, we report the concise synthesis and comprehensive photophysical characterization of a boron-nitrogen fused [7]helicene, which shows emission in the yellow-green region, prolonged fluorescence lifetimes, and redox activity. Single-crystal X-ray diffraction studies confirm the coexistence of P- and M-helical enantiomers, which adopt an ordered heterochiral packing arrangement in the solid state. Furthermore, the helical boron-nitrogen adduct was investigated in cell imaging studies, where it exhibits enhanced intracellular photostability, lower cytotoxicity, and effective staining of cytoplasmic compartments. Additionally, to gain insight into its electronic structure and frontier molecular orbital energetics, density functional theory (DFT) calculations were performed.