Poly[(arylene ethynylene)-alt-(arylene vinylene)]s Based on Anthanthrone and Its Derivatives: Synthesis and Photophysical, Electrochemical, Electroluminescent, and Photovoltaic Properties

Anthanthrone and its derivatives are large polycyclic aromatic compounds (PACs) that pose a number of challenges for incorporation into the structure of soluble conjugated polymers. For the first time, this group of PACs was employed as the building blocks for the synthesis of copolymers (P1-P5) based on poly[(arylene ethynylene)-alt-(arylene vinylene)]s backbone (-Ph-C≡C-Anth-C≡C-Ph-CH=CH-Ph-CH=CH-) _n . During the synthesis of P1-P5, different alkyloxy side chains were incorporated in order to tune the properties of the polymers. Of the copolymer series only P1 (containing anthanthrone and branched 2-ethylhexyloxy side chains on phenylenes), P2 and P3 (for which the anthanthrones containing carbonyl groups were converted to anthanthrene containing alkyloxy substituents) were soluble. The photophysical, electrochemical, electroluminescent and photovoltaic properties of P1-P3 are reported, compared and discussed with respect to the effects of side chains.

Revelation of Interfacial Energetics in Organic Multiheterojunctions

Efficient charge generation via exciton dissociation in organic bulk heterojunctions necessitates donor-acceptor interfaces, e.g., between a conjugated polymer and a fullerene derivative. Furthermore, aggregation and corresponding structural order of polymer and fullerene domains result in energetic relaxations of molecular energy levels toward smaller energy gaps as compared to the situation for amorphous phases existing in homogeneously intermixed polymer:fullerene blends. Here it is shown that these molecular energy level shifts are reflected in interfacial charge transfer (CT) transitions and depending on the existence of disordered or ordered interfacial domains. It can be done so by systematically controlling the order at the donor-acceptor interface via ternary blending of semicrystalline and amorphous model polymers with a fullerene acceptor. These variations in interfacial domain order are probed with luminescence spectroscopy, yielding various transition energies due to activation of different recombination channels at the interface. Finally, it is shown that via this analysis the energy landscape at the organic heterojunction interface can be obtained.

Synthesis and Photophysical and Electroluminescent Properties of Poly(1,4-phenylene-ethynylene)-alt-poly(1,4-phenylene-vinylene)s with Various Dissymmetric Substitution of Alkoxy Side Chains

The synthesis and characterization of a set of conjugated polymers, poly(1,4-phenylene–ethynylene)-alt-poly(1,4-phenylene–vinylene)s (PPE–PPVs), with a dissymmetrical configuration (partial or total) of alkoxy side chains is reported. Five new polymers bearing octyloxy and/or octadecyloxy side chains at the phenylene–ethynylene and phenylene–vinylene segments, respectively, were obtained. Two symmetrical substituted polymers were used for comparison. Polymers with weight-average molecular weight, M_w, up to 430 000 g/mol and degree of polymerization between 17 and 322 were obtained by a Horner–Wadsworth–Emmons olefination polycondensation reaction of the respective luminophoric dialdehydes and bisphosphonates. As expected, identical conjugated backbones in all polymers results in very similar photophysical response in dilute solution, with high fluorescence quantum yields between 50% and 80%. In contrast, the thin film properties are dependent on the combinatorial effects of side chain configuration, molecular weight, and film thickness parameters, which are the basis of the resulting comparison and discussion.

Rhodium-coordinated poly(arylene-ethynylene)-alt-poly(arylene-vinylene) copolymer acting as photocatalyst for visible-light-powered NAD⁺/NADH reduction

A 2,2'-bipyridyl-containing poly(arylene-ethynylene)-alt-poly(arylene-vinylene) polymer, acting as a light-harvesting ligand system, was synthesized and coupled to an organometallic rhodium complex designed for photocatalytic NAD(+)/NADH reduction. The material, which absorbs over a wide spectral range, was characterized by using various analytical techniques, confirming its chemical structure and properties. The dielectric function of the material was determined from spectroscopic ellipsometry measurements. Photocatalytic reduction of nucleotide redox cofactors under visible light irradiation (390-650 nm) was performed and is discussed in detail. The new metal-containing polymer can be used to cover large surface areas (e.g. glass beads) and, due to this immobilization step, can be easily separated from the reaction solution after photolysis. Because of its high stability, the polymer-based catalyst system can be repeatedly used under different reaction conditions for (photo)chemical reduction of NAD(+). With this concept, enzymatic, photo-biocatalytic systems for solar energy conversion can be facilitated, and the precious metal catalyst can be recycled.