255. Green-Tuning of (Chir)Optical Properties for Axially-Chiral Boramidines
     Nidal Saleh, Lorenzo Arrico, Francesco Zinna, Jérôme Lacour
     Helv. Chim. Acta 2025, e202500059

The integration of boron into π-conjugated systems is a reliable approach to enhance photophysical properties. In this context, boramidines have emerged as a promising class of fluorophores. Herein, the design, synthesis, and chiroptical properties of novel axially chiral isoquinoline-derived boramidines are reported. Thanks to metal-catalyzed cross-coupling allied with atroposelective C-H arylation strategies or chiral stationary phase HPLC resolution, enantioenriched boramidines 1 and 2 are afforded (ee 90-99%). Comparing with more classical boramidines, investigations reveal (i) bathochromic absorption shifts in the UV-Vis region (>50 nm) and (ii) emission maxima now in the green and cyan domains, along with fluorescence quantum yields reaching 70% in N₂-saturated environments. Chiroptical measurements demonstrate well-defined electronic circular dichroism (ECD) spectra and circularly polarized luminescence (CPL) signals with |g_lum| values up to 2·10⁻³

DOI : 10.1002/hlca.202500059 

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