Dyads Containing Iridium(III) Bis-terpyridine as Photoactive Center: Synthesis and Electron Transfer Study

A series of Ir(III)-D dyads based on an iridium(III) bis-terpyridine complex as a photoactive center and tertiary amines as donor groups, as well as their individual components, have been designed to generate photoinduced charge separation. Depending on the donor group, a modular approach or a "chemistry-on-the-complex" approach has been used to prepare three different Ir(III)-D dyads. A detailed photophysical study has been performed on one Ir(III)-D dyad in which a triarylamine is linked to the iridium bis-terpyridine complex with an amido-phenyl group used as a spacer. In acetonitrile at room temperature, steady-state and time-resolved methods gave evidence of a photoinduced charge-separated state Ir^--D⁺ with a lifetime of 70 ps. This relatively short lifetime could be due to the close proximity between the negative charge, likely localized in the bridging terpyridine, and the oxidized donor group.