Abstract The reaction of iridium terpyridyl trichloride, [Ir(tpy)Cl 3 ], with the following ligands has been investigated: 6′-phenyl-2,2′-bipyridine (HL 1 ), its 4′-tolyl-derivative (HL 2 ), and an annelated version of the latter incorporating an ethylene bridge between C5′ and the pendent phenyl ring (HL 3 ). Although all three are potentially C^N^N-coordinating ligands, none are found to bind in this way in the products isolated. Ligand HL 1 binds through its two nitrogen atoms only, leading to a dicationic complex [Ir(tpy)(HL 1 - N , N )Cl] 2+ , 1 , with an ‘N 5 Cl’ coordination sphere. In contrast, the presence of the 4′-tolyl group in HL 2 and HL 3 favours cyclometallation of the central pyridine ring through position C3′, leading to N^C-binding and to the monocationic complexes [Ir(tpy)(L 2 - C 3 ′, N )Cl] + , 2 , and [Ir(tpy)(L 3 - C 3 ′, N )Cl] + , 3 . The cyclometallated complexes 2 and 3 are intensely luminescent in solution at room temperature ( λ max = 541 and 562 nm; τ = 3.2 and 2.4 μs, respectively; ϕ = 0.16 for both, in degassed CH 3 CN at 295 K), probably arising from a state of primarily 3 MLCT character. In contrast, the N 5 -coordinated complex 1 is only weakly emissive under the same conditions. To cite this article: A.J.S. Bexon, J.A.G. Williams, C. R. Chimie 8 (2005) .