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

Abstract

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.