Synthesis and characterization of alternative donor–acceptor arranged poly(arylene ethynylene)s derived from 1,4-diketo-3,6-diphenylpyrrolo[3,4-c]pyrrole (DPP)

Triplet state formation in homo- and heterometallic diketopyrrolopyrrole chromophores

The synthesis, structural characterization, and excited-state dynamics of series of diketopyrrolopyrrole (DPP) bridged homodinuclear Ir(III) and heterodinuclear Ir(III)/Pt(II) complexes is described. Steady-state and time-resolved photoluminescence along with transient absorption measurements were used to probe the nature of the emissive and long-lived excited states. Upon excitation into the (1)DPP ligand-localized excited state in the presence of coordinated Ir(III) or Pt(II) metal centers, the intersystem crossing is enhanced, leading to a quenching of the (1)DPP fluorescence and the formation of the long-lived (τ ≈ 30-40 μs) (3)DPP excited state in all instances.

Metal coordination induced π-extension and triplet state production in diketopyrrolopyrrole chromophores

Triplet state photophysics has been generated in two distinct diketopyrrolopyrrole (DPP) chromophores terminated with either phenyl (1) or thienyl (2) spacers, when sandwiched between two Ir(III) complexes using bipyridyl linkers. Upon coordination of the bpy-DPP-bpy subunit resulting in its planarization, the π-conjugation in the DPP chromophore formally extends and was manifested as a substantial red shift in the absorption and fluorescence profiles of 1 and 2. Low energy excitation of these dinuclear metal complexes produced strongly quenched singlet fluorescence, generated quite intense long-lived (τ ∼ 3 μs) absorption transients in the red, sensitized (1)O(2) photoluminescence centered at 1270 nm in aerated solutions, and yielded low temperature near-IR phosphorescence in 1 centered at 950 nm.