Synthesis, luminescence, and excited-state complexes of the tris(1,10-phenanthroline)- and bis(terpyridine)iridium(III) cations

The authors report the synthesis and luminescence properties of Ir(phen){sub 3}{sup 3+} and Ir(terp){sub 2}{sup 3+} (phen = 1,10-phenanthroline and terp = 2,6-bis(2-pyridyl)pyridine). Their emissions are assigned to predominantly {pi}-{pi}* phosphorescences. A novel excited-state complex is proposed to form between Ir(phen){sub 3}{sup 3+} and Ir(terp){sub 2}{sup 3+} and HgCl{sub 2}. Although HgCl{sub 2} is normally a quencher, it can greatly enhance the lifetimes and luminescence efficiencies of the Ir(phen){sub 3}{sup 3+} and Ir(terp){sub 2}{sup 3+} - up to an order of magnitude. The changes arise from alteration of the radiative and nonradiative rate constants in the excited-state complex. The effect of temperature, solvent, oxygen, and inert ions on the interactions of HgCl{sub 2} with the excited complexes is explored. A simple associative model accurately reproduces all lifetime and intensity changes. A rationale based on the well-known affinity of HgCl{sub 2} for aromatic molecules is proposed.