Synthesis of it-Conjugated Chiral Organoborane Macrocycles with Blue to Near-Infrared Emissions and the Diradical Character of Cations

Highly emissive pi-conjugated macrocycles with tunable circularly polarized luminescence (CPL) have sparked theoretical and synthetic interests in recent years. Herein, we report a synthetic approach to obtain new chiral organoborane macrocycles (CMC1, CMC2, and CMC3) that are built on the structurally chiral [5]helicenes and highly luminescent triarylborane/ amine moieties embedded into the cyclic systems. These rarely accessible B/N-doped main-group chiral macrocycles show a unique topology dependence of the optoelectronic and chiroptical properties. CMC1 and CMC2 show a higher luminescence dissymmetry factor (glum) together with an enhanced CPL brightness (B-CPL) as compared with CMC3. Electronic effects were also tuned and resulted in bathochromic shifts of their emission and CPL responses from blue for CMC1 to the near-infrared (NIR) region for CMC3. Furthermore, chemical oxidations of the N donor sites in CMC1 gave rise to a highly stable radical cation (CMC1(center dot+)SbF(6)(-)) and diradical dication species (CMC1(2 center dot 2)+2SbF(6)(-)) that serve as a rare example of a positively charged open-shell chiral macrocycle.