The synthesis and photophysical properties of a new luminescent Ir(III) diimine complex covalently attached to one 4-piperidinyl-1,8-naphthalimide (PNI) chromophore, [Ir(ppy)2(phen-PNI)](PF6)2, is presented. This compound represents a new class of visible light-harvesting Ir(III) chromophores that exhibit greatly enhanced room temperature metal-to-ligand charge transfer (MLCT) emission lifetimes as a result of intervening ligand centered (LC) triplet states present on the pendant naphthalimide chromophore. In the Ir(III) complex, the intense singlet fluorescence of the pendant PNI chromophore is nearly quantitatively quenched and was found to sensitize the MLCT-based photoluminescence. The title chromophore represents an interesting example of “ping-pong” energy transfer wherein photon excitation first migrates away from the initially prepared 1LC* excited state and then ultimately returns to this moiety as a long-lived excited triplet which disposes of its energy by equilibrating with the photoluminescent Ir(III) MLCT excited state.

Bidirectional “ping-pong” energy transfer in a Ir(III) charge transfer complex

249th National Meeting (2015)

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