A new class of charge-neutral, bis-tridentate Ir(III) metal complexes is designed, synthesized and applied as emitters in the fabrication of organic light emitting diodes. Their basic properties are discussed vs. their tris-bidentate counterparts. Display omitted •Relationship of the terpyridine complexes Ru(tpy)22+ and Ir(tpy)23+ are reviewed.•Dianionic chelates are constructed using pyrazole, pyridine and phenyl fragments.•N^C^N, C^N^C and C^C^C type ancillaries are employed to obtain monoanionic chelates.•Properties of the charge-neutral bis-tridentate Ir(III) complexes are discussed.•Bis-tridentate Ir(III) metal complexes are useful emitters for OLEDs. 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)22+ and Ir(tpy)23+, 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.