Emissive bis-tridentate Ir(III) metal complexes : Tactics, photophysics and applications

This review is an update on current advances in metal complexes with d⁶-electronic configuration and bearing two tridentate chelates. We first elaborate the basic properties of the famous cationic complexes [Ru(tpy)₂]²⁺ and [Ir(tpy)₂]³⁺, where tpy represents 2,2′:6′,2″-terpyridine. The emphasis is then switched to various charge-neutral, bis-tridentate Ir(III) complexes, with emission spanning the whole visible region from blue, green to red. These Ir(III) metal complexes are capable of exhibiting high luminescence efficiency, reduced radiative lifetime, and adequate volatility and stability, similar to those of their traditional tris-bidentate Ir(III) counterparts, destined to be viable OLED phosphors.