Ligand Exchange Triggered Photosensitizers – Bodipy‐Tagged NHC‐Metal Complexes for Conversion of ³O₂ to ¹O₂

A new imidazolium salt 3⋅HI with 8‐Bodipy as one N‐aryl substituent was synthesized from 8‐chloro‐Bodipy and imidazole followed by alkylation with iPrI. NHC‐metal complexes [CuCl(3)], [AuCl(3)], [Pd(allyl)Cl(3)] and [MCl(cod)(3)] and [MCl(CO)₂(3)] (M=Rh, Ir) were synthesized and the X‐ray crystal structure of [IrCl(CO)₂(3)] determined. The donation of NHC 3 was determined via IR (ν(CO) and cyclic voltammetry (Ir(I/II) redox potential). The photosensitizing properties of the complexes for the generation of ¹O₂ were quantified observing singlet oxygen quantum yield of up to Φs.o.=0.63. [IrCl(cod)(3)] displays poor Φs.o.=0.09, but, following a simple ligand exchange reaction of cod by two CO [IrCl(CO)₂(3)], a pronounced increase to Φs.o.=0.63 is observed.