Light, Redox, and Ligand Noninnocence Cooperate in Naphthalene Diimide-Functionalized N-Heterocyclic Carbene Iridium Complexes.

In this study, we describe the synthesis and reactivity of naphthalene diimide (NDI)-functionalized N-heterocyclic carbene (NHC) iridium complexes that display uncommon multi-stimuli-responsive behavior combining redox activity, photochemical responsiveness, and photocatalytic reactivity within a single molecular platform. Structural and spectroscopic studies reveal the presence of an unusually strong intramolecular Ir-Cl(lp)···π interaction involving the NDI unit, whose energetic parameters were determined experimentally by variable-temperature NMR analysis. Treatment of the parent NDI-NHC complex with basic anions promotes an unexpected solvolytic transformation leading to a rare chelating NHC-iminolate napthalene-monoimide (NMI) complex, illustrating the noninnocent reactivity of the diimide-functionalized ligand scaffold. Both complexes undergo efficient visible-light-induced reduction in the presence of triethylamine, generating stable radical-anion species through photoinduced electron transfer processes. The resulting photoreduced species operate as photocatalysts for the hydrodehalogenation of aryl halides through consecutive photoinduced electron transfer (conPET) pathways and enable photochemical C─C bond formation reactions.