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

Highly emissive π-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 ( g lum ) 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 ·+ SbF 6 - ) and diradical dication species ( CMC1 2·2+ 2SbF 6 - ) that serve as a rare example of a positively charged open-shell chiral macrocycle.