Triskelion-shaped iridium-helicene NHC complex

Abstract

Enantiopure tris-helicenic chiral-at-iridium complexes have been prepared, constituting the first examples of organometallic metal-tris-helicenes. They have the mer- or fac-Ir(C^C:)₃ form, where (C^C:) is an N-heterocyclic carbene ligand N-substituted with a hexahelicene. Their triskelion geometry and stereochemistry have been thoroughly studied and assigned by NMR in combination with quantum-chemical modelling and by comparison with the X-ray structure of analogues. Thanks to their Ir(III)-based multihelicenic architecture, the complexes display strong electronic circular dichroism and optical rotation along with long-lived yellow phosphorescence, involving circularly polarized emission with g_lum factors around 10⁻³.