Accessing the Triplet Excited State in Perylenediimides

Here, we present a strategy designed to permit access to the PDI triplet manifold that preserves the desirable colorfastness and visible light-absorption properties associated with these dyes. To this end, three new Pt(II) complexes each bearing two PDI moieties tethered to the metal center via acetylide linkages emanating from one of the PDI bay positions have been synthesized, structurally characterized, and thoroughly examined by nanosecond laser flash photolysis. Upon ligation, the bright singlet-state fluorescence of the PDI chromophore is quantitatively quenched, and no long wavelength photoluminescence is observed from the Pt(II)-PDI complexes in deaerated solutions. In each of the Pt-PDI chromophores, quantitatively similar transient absorption difference spectra were obtained; the only distinguishing characteristic is in their single-exponential lifetimes (tau = 246 ns, 1.0 micros, and 710 ns). Triplet-state sensitization experiments of "free" PDI-CCH using thioxanthone confirmed the PDI triplet state assignments in each of the Pt-PDI structures.