Long-lived circularly-polarized phosphorescence in helicene-NHC-rhenium(I) complexes: the influence of helicene, halogen and stereochemistry on emission properties.

First enantiopure, chiral‐at‐rhenium complexes of the form fac ‐ReX(CO) 3 (:C^N) have been prepared, where:C^N is a helicene N‐heterocyclic carbene ligand and X = Cl or I. They have shown strong changes in the emission characteristics, notably strongly enhanced phosphorescence lifetimes (reaching 0.7 ms) and increased CPL activity, as compared to their parent chiral models lacking the helicene unit. Identity of the halogen along with its position within the dissymmetric stereochemical environment strongly affect the photophysics of the proposed complexes, particularly the phosphorescence quantum yield and lifetime. All these results give fresh insight into fine tuning of photophysical and chiroptical properties of Re‐NHC systems.