Highly Emissive Double π-Helical Molecular Carbons via Nitrogen Integration

Improving the emission efficiency of chiral π-systems is of significance for their practical applications in materials science. Herein, we report a family of highly emissive double π-helical molecular carbons featuring a cyclooctatetraphenylene (COTt) or cyclooctahexaphenylene (COTh) core. In contrast to previously reported non-emissive tetrabenzo-COTt derivatives, the introduction of nitrogen via diarylamine/carbazole fusion leads to fluorescence quantum yields as high as 98%. The high configurational stability of these double π-helices enabled successful chiral resolution of their enantiomers using high-performance liquid chromatography. Notably, structural evolution from the COTt to the COTh core results in an approximately three-fold increase in the luminescence dissymmetry factor (g_lum), while the circularly polarized luminescence (CPL) brightness reached 110 M^-1 cm^-1, among the highest values reported for cyclooctatetraene (COT)-based chiral molecular carbons. Theoretical calculations further support these results, revealing large electric transition dipole moments (|μ|) and perfect parallel/antiparallel alignment between the μ and magnetic transition dipole moments (m). Our work provides valuable insight into the molecular design of high luminescent chiral emitters.