Small quantities of Cl- ions result in dramatic reductions in the performance of ionic transition metal complexes in light-emitting electrochemical cells. Strong ion-pairing between aromatic protons and chloride has been established in both the solid state and solution. X-ray structural determination of 2{[Ir(ppy)(2)(bpy)][Cl]}center dot 2CH(2)Cl(2)center dot[H3O]center dot Cl reveals the unusual nature of an impurity encountered in the preparation of [Ir(ppy)(2)(bpy)][PF6].
