The electronic structure and photophysical properties of a luminescent Ir(III) diimine complex covalently attached to one 4-piperidinyl-1,8-naphthalimide (PNI) chromophore, [Ir(ppy)<sub>2</sub>(phen-PNI)](PF<sub>6</sub>), is presented. This compound represents a new class of visible light-harvesting Ir(III) chromophores that exhibit greatly enhanced room temperature emission lifetimes as a result of intervening ligand centered (LC) triplet states present on the pendant naphthalimide chromophore. In this Ir(III) bichromophore system, the intense singlet fluorescence of the pendant PNI chromophore is nearly quantitatively quenched and was found to sensitize the Ir(III) charge transfer excited state. The excited state ultimately returns to the PNI chromophore as a long-lived excited triplet which disposes of its energy by equilibrating with the photoluminescent Ir(III) charge transfer excited state. Evidence of the excited state equilibrium is provided via emission spectroscopy, transient absorption spectroscopy, and time-dependent density functional theory calculations.

Tracking the excited state equilibrium in an Ir(III) bichromophore system: A combined time resolved spectroscopy and computational study

251st National Meeting (2016)

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