We report the synthesis, characterization, and biological activity of Ir I complexes with triazole-(NNHC) and thiazole-based (NSHC) N-heterocyclic carbene ligands. Starting from the dimeric [Ir(COD)Cl] 2 , we obtained complexes of composition Ir(COD)(NNHC)Cl (4a), Ir(COD)(NNHC)X (4b: X = Cl; 4bBr: X = Br), [Ir(COD)(NNHC)(NHC)]I (5a), [Ir(COD)(NSHC) 2 ]Cl (6a), and [Ir(COD)(NSHC)(NNHC)]Cl (6b) by adaptation of established synthetic methods for metal-NHC complexes. Their interactions with model proteins cytochrome c and lysozyme, as well as with the oligonucleotide hexamer (CG) 3 (ODN1), were studied. 2461 Scheme 1. (a) 0.5 equiv. Ag 2 O, 0.5 equiv.[Ir(COD)Cl] 2 , CH 2 Cl 2 , room temp. overnight, (b) 3 equiv. KBr, acetonitrile, r.t. overnight, (c) 1/3a respectively,1 equiv. K 2 CO 3 , CH 2 Cl 2 , r.t., 2-5 d, (d) NaBF 4 , acetonitrile, r.t., (e) 3a, KOtBu, r.t., overnight.