The Effect of Aryl Substitution on the Properties of a Series of Highly Absorptive Cationic Iridium(III) Complexes Bearing Ancillary Bis(arylimino)acenaphthene Ligands

A family of cationic heteroleptic iridium(III) complexes of the form [Ir(ppy) 2 (Ar‐BIAN)]PF 6 (ppyH = 2‐phenylpyridine) in which Ar‐BIAN [bis(arylimino)acenaphthene] acts as an ancillary ligand were synthesized and characterized. Their ground‐state electronic structures were probed by UV/Vis spectroscopy and cyclic voltammetry. The X‐ray structure of [Ir(ppy) 2 (4‐MeO 2 CPh‐BIAN)]PF 6 was solved. The first and second reduction wave potentials are strongly influenced by the substituent on the Ar‐BIAN ligand and follow a Hammett relationship. The absorption spectra for complexes incorporating an electron‐donating Ar‐BIAN ligand are noticeably redshifted, and absorption tails off past 800 nm. Notably, the absorption spectrum for [Ir(ppy) 2 (4‐NMe 2 Ph‐BIAN)]PF 6 shows an intense band centered at 576 nm, and it was assigned computationally to a mixed metal‐to‐ligand charge‐transfer/ligand‐to‐ligand charge‐transfer state.