Design, Synthesis and Ring-Opening Properties of a New Bipyridine Fused Rhodamine-Like Chelating Ligand and the Related Transition Metal Complexes†

Main observation and conclusion A new bipyridine fused rhodamine-like chelating ligand and the corresponding transition metal complexes of platinum(II) and iridium(III) have been designed, synthesized and structurally characterized by X-ray crystallography. Their photophysical properties and acid- or metal ion-promoted spirocarbon ring-opening properties have been investigated. The platinum(II) and iridium(III) complexes show a drastic color change in solution with Hg2+ ions and emergency of an absorption band at around 450-600 nm, assignable to the absorption band of the ring-opened rhodamine-like ligand. The platinum(II) complex was suggested to undergo dissociation with Hg2+ ion, based on the corresponding absorption titration study. Emission titration studies of iridium(III) complexes were found to suffer from the quenching process, probably due to the presence of a lower-lying non-emissive excited state from the ring-opened form of ligand.

Automated summary

A new bipyridine fused rhodamine-like chelating ligand and its corresponding transition metal complexes of platinum(II) and iridium(III) were designed, synthesized, and structurally characterized. These complexes exhibit unique photophysical properties and undergo spirocarbon ring-opening properties in the presence of acid or metal ions. The platinum(II) complex shows dissociation with Hg2+ ions, while the emission titration studies of iridium(III) complexes are affected by the quenching process from the ring-opened form of ligand's lower-lying non-emissive excited state.