Role of Macromolecular Structure in the Ultrafast Energy and Electron Transfer Dynamics of a Light-Harvesting Polymer

Ultrafast energy and electron transfer (EnT and ET, respectively) are characterized in a light-harvesting assembly based on a π-conjugated polymer (poly­(fluorene)) functionalized with broadly absorbing pendant organic isoindigo (iI) chromophores using a combination of femtosecond transient absorption spectroscopy and large-scale computer simulation. Photoexcitation of the π-conjugated polymer leads to near-unity quenching of the excitation through a combination of EnT and ET to the iI pendants. The excited pendants formed by EnT rapidly relax within 30 ps, whereas recombination of the charge-separated state formed following ET occurs within 1200 ps. A computer model of the excited-state processes is developed by combining all-atom molecular dynamics simulations, which provides a molecular-level view of the assembly structure, with a kinetic model that accounts for the multiple excited-state quenching pathways. Direct comparison of the simulations with experimental data reveals that the underlying structure has a dramatic effect on the partitioning between EnT and ET in the polymer assembly, where the distance and orientation of the pendants in relation to the backbone serve to direct the dominant quenching pathway

<i>N</i>‑Alkyldinaphthocarbazoles, Azaheptacenes, for Solution-Processed Organic Field-Effect Transistors

Substituted <i>N</i>-alkyldinaphthocarbazoles were synthesized using a key double Diels–Alder reaction. The angular nature of the dinaphthocarbazole system allows for increased stability of the conjugated system relative to linear analogues. The <i>N</i>-alkyldinaphthocarbazoles were characterized by UV–vis absorption and fluorescence spectroscopy as well as cyclic voltammetry. X-ray structure analysis based on synchrotron X-ray powder diffraction revealed that the <i>N</i>-dodecyl-substituted compound was oriented in an intimate herringbone packing motif, which allowed for p-type mobilities of 0.055 cm² V^–1 s^–1 from solution-processed organic field-effect transistors

<i>N</i>‑Alkyldinaphthocarbazoles, Azaheptacenes, for Solution-Processed Organic Field-Effect Transistors

Substituted <i>N</i>-alkyldinaphthocarbazoles were synthesized using a key double Diels–Alder reaction. The angular nature of the dinaphthocarbazole system allows for increased stability of the conjugated system relative to linear analogues. The <i>N</i>-alkyldinaphthocarbazoles were characterized by UV–vis absorption and fluorescence spectroscopy as well as cyclic voltammetry. X-ray structure analysis based on synchrotron X-ray powder diffraction revealed that the <i>N</i>-dodecyl-substituted compound was oriented in an intimate herringbone packing motif, which allowed for p-type mobilities of 0.055 cm² V^–1 s^–1 from solution-processed organic field-effect transistors

Efficient Light-Driven Oxidation of Alcohols Using an Organic Chromophore–Catalyst Assembly Anchored to TiO₂

The ligand 5-PO₃H₂-2,2′:5′,2″-terthiophene-5-trpy, <b>T3</b> (trpy = 2,2′:6′,2″-terpyridine), was prepared and studied in aqueous solutions along with its metal complex assembly [Ru­(<b>T3</b>)­(bpy)­(OH₂)]²⁺ (<b>T3</b>-Ru-OH₂, bpy = 2,2′-bipyridine). <b>T3</b> contains a phosphonic acid group for anchoring to a TiO₂ photoanode under aqueous conditions, a terthiophene fragment for light absorption and electron injection into TiO₂, and a terminal trpy ligand for the construction of assemblies comprising a molecular oxidation catalyst. At a TiO₂ photoanode, <b>T3</b> displays efficient injection at pH 4.35 as evidenced by the high photocurrents (∼350 uA/cm²) arising from hydroquinone oxidation. Addition of [Ru­(bpy)­(OTf)]­[OTf]₂ (bpy = 2,2′-bipyridine, OTf^– = triflate) to <b>T3</b> at the free trpy ligand forms the molecular assembly, <b>T3</b>-Ru-OH₂, with the oxidative catalyst fragment: [Ru­(trpy)­(bpy)­(OH₂)]²⁺. The new assembly, <b>T3</b>-Ru-OH₂, was used to perform efficient light-driven oxidation of phenol (230 μA/cm²) and benzyl alcohol (25 μA/cm²) in a dye-sensitized photoelectrosynthesis cell

Decacyclene Trianhydride at Functional Interfaces: An Ideal Electron Acceptor Material for Organic Electronics

We report the interface energetics of decacyclene trianhydride (DTA) monolayers on top of two distinct model surfaces, namely, Au(111) and Ag(111). On the latter, combined valence band photoemission and X-ray absorption measurements that access the occupied and unoccupied molecular orbitals, respectively, reveal that electron transfer from substrate to surface sets in. Density functional theory calculations confirm our experimental findings and provide an understanding not only of the photoemission and X-ray absorption spectral features of this promising organic semiconductor but also of the fingerprints associated with the interface charge transfer