Bis-4-aza[6]helicene: A Bis-helicenic 2,2'-Bipyridine with Chemically Triggered Chiroptical Switching Activity.

A novel enantiopure bis-helicenic 2,2'-bipyridine system was prepared using a Negishi coupling. Thanks to the bipyridine unit, the coordination with ZnII and protonation processes were studied, revealing efficient tuning of photophysical (UV/visible and emission) and chiroptical properties (electronic circular dichroism and circularly polarized emission) of the system. The coordination/decoordination and protonation/deprotonation processes appeared reversible, thus constituting novel chiroptical switches.