Metal Coordination Induced π-Extension and Triplet State Production in Diketopyrrolopyrrole Chromophores

Abstract

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.

Diketopyrrolopyrroles: Synthesis, Reactivity, and Optical Properties

“…2015, 3, 280-320 www.MaterialsViews.com www.advopticalmat.de through bipyridyl groups ( Scheme 61 ). [ 110 ] Such DPP chromophore extension caused substantial red shifts in the absorption and fl uorescence spectra of these two dyes. Due to the presence of heavy iridium atoms, the fl uorescence of the products was strongly quenched.…”

Protonation‐Dependent Luminescence of an Iridium(III) Bibenzimidazole Chromophore

“…An intense band in the UV region was ascribed to spin-allowed 1 π-π* transitions localized on both coordinated aromatic ligands through reference to the previously well-established photophysical properties of iridium(III) diamine complexes. [15,[33][34][35][36][37][38][39][40][41] The nature of the absorption bands between λ=300 and 450 nm is best described as a mixture of spin-allowed charge-transfer ( 1 CT) transitions that contain contributions from both dπ Ǟ π* tmBBI metalto-ligand charge-transfer ( 1 MLCT) and π ppy Ǟ π* tmBBI ligand-to-ligand charge-transfer ( 1 LLCT) transitions. However, on the basis of investigations on the related complex [(ppy) 2 Ir(bpy)] + (bpy = 2,2Ј-bipyridine; R6), the major contribution to the absorption band at λ = 380 nm should be a mixed dπ Ǟ π* ppy 1 MLCT and a ligand-centered π Ǟ π* (LC) transition of the ppy ligand.…”

Accessing the Long-Lived Triplet Excited States in Transition-Metal Complexes: Molecular Design Rationales and Applications

“…Diketopyrrolopyrrole (DPP) has been widely used in fluorescent molecular probes and photovoltaics, but its application in triplet‐state studies is rare. Binuclear Ir(III) complexes 58 and 59 with DPP ligands were prepared (Figure ) . A triplet state localized on the DPP moiety was observed for both complexes, with triplet‐state lifetimes of ca.…”