Dye-Sensitization Enables Visible-Light-Driven N–N Bond Cleavage in a Dinuclear Rhenium Dinitrogen Complex

Conversion of μ-N2 complexes into nitrogenous compounds is one of the most important and challenging chemical transformations in N2 fixation. Although photochemical N2 splitting has been demonstrated, existing approaches predominantly rely on high-energy ultraviolet light that generally affords low efficiency and poor selectivity. Herein, we establish a visible-light-driven molecular photosensitization strategy that enables efficient and selective N–N bond cleavage in a dinuclear rhenium dinitrogen complex. Blue light excitation of the organic photosensitizer 4DPAIPN (2,4,5,6-tetrakis(diphenylamino)isophthalonitrile) is shown to initiate N–N scission to afford the corresponding rhenium nitride in 96% yield. Kinetic analysis of nanosecond transient absorption data through the Balzani-Scandola model indicates energy transfer from the photosensitizer to an acceptor state that lies approximately 2.31 eV above the ground state of the μ-N2-bridged dirhenium complex. This photosensitization strategy decouples light harvesting from N–N bond activation, eliminates the need for UV light, and shows broad applicability across different visible-light absorbing photosensitizers, including transition metal complexes and organic chromophores with long-lived, high-energy triplet excited-states. These findings establish dye-sensitization as a powerful strategy for visible-light-driven N–N bond cleavage for mechanistic study and the future realization of a photochemical pathway for nitrogen fixation.