Enantiopure cycloiridiated complexes bearing a pentahelicenic N-heterocyclic carbene and displaying long-lived circularly-polarized phosphorescence

A fused pi-helical N-heterocyclic (NHC) system has been prepared and examined through its diastereoisomerically pure cycloiridiated complexes. The latter display light-green phosphorescence with i) unusually long lifetimes and ii) circular polarization that depends on both the helical-NHC P/M and the iridium delta/lambda stereochemistry. These unprecedented features are attributed to extended pi-conjugation within helical carbenic ligand and efficient helicene-NHC-Ir interaction.