Cationic iridium(iii) complexes bearing a bis(triazole) ancillary ligand

Abstract

Three new heteroleptic cationic iridium complexes of the form [Ir(C^N)(btl)]⁺, where btl = 1,1′-benzyl-4,4′-bi-1H-1,2,3-triazolyl and C^N = 2-phenylpyridine (ppyH) (1), 1-benzyl-4-phenyl-1H-1,2,3-triazole (phtl) (2) or 1-benzyl-4-(2,4-difluorophenyl)-1H-1,2,3-triazole (dFphtl) (3), were synthesized and isolated as their hexafluorophosphate (PF₆⁻) salts and fully characterized. The single crystal structure of 3 has been solved. Along the series from 1–3 the absorption spectra shift hypsochromically while the electrochemical gap increases from 3.25 to 3.54 to 3.88 V. Acetonitrile solutions of 1 and 2 are poorly luminescent, sky-blue emitters with predominant ligand-centered and charge transfer character, respectively. Theoretical calculations support these assignments. Complex 3 is not photostable and decomposes to solvento-based structures of the form [Ir(dFphtl)₂(ACN)_n]⁺ (n = 1, 2) through a dissociation and degradation of the btl ligand.