No abstract

Despite advances in photochemical atom transfer radical polymerization (photoATRP), these systems often rely on the use of UV light for the activation/generation of the copper-based catalytic species. To circumvent the problems associated with the UV light, we developed a dual photoredox catalytic system to mediate photoinduced ATRP under red-light irradiation. The catalytic system is comprised of a Cu catalyst to control the polymerization via ATRP equilibrium and a photocatalyst, such as zinc(II) tetraphenylporphine or zinc(II) phthalocyanine, to generate the activator Cu I species under red-light irradiation. In addition, this system showed oxygen tolerance due to the consumption of oxygen in the photoredox reactions, yielding well-controlled polymerizations without the need for deoxygenation processes.

In the title compound, C5N6, all the atoms are approximately coplanar. In the crystal, mol­ecules are packed with short contact distances of 2.885 (2) (between the diazo N atom connected to the ring and a cyano N atom on a neighboring mol­ecule) and 3.012 (2) Å (between the terminal diazo N atom and an N atom of a neighboring imidazole ring).

Poly­(3-hexylthiophene) (P3HT) is a well-studied benchmark system for semiconducting polymers used in optoelectronic devices. In these materials, aggregation can improve charge transport efficiency or enhance emission yields depending on the interchain packing. This may be inferred from the absorption and emission spectra when analyzed using exciton coupling models such as the well-known H- and J-coupling model of Kasha. The more recently developed weakly coupled H-aggregate (WCH) model quantifies the degree of disorder via the ratio of the electronic origin intensity to that of the first vibronic band. Here, the underlying assumptions of this approach are tested experimentally for P3HT aggregates formed by solvent poisoning using bulk and single-molecule-based spectroscopic techniques. Specifically, we show that the contribution of residual monomeric chains to the aggregate spectrum must be accounted for to properly assign the spectra as H- or J-type. A modification of the WCH model is introduced to account for multiple emissive species.

A new efficient three-step process to annulate polycyclic aromatic hydrocarbons (PAHs) has been developed, providing access to PAHs with saturated rings that under current chemical methods would be difficult to produce in an efficient manner. This method relies on a palladium-catalyzed cross-coupling reaction of various brominated PAHs with cyclohexanone to yield α-arylated ketones, which are converted to regiospecific vinyl triflates and cyclized by a palladium-catalyzed intramolecular arene-vinyl triflate coupling to produce PAHs with incorporated saturated rings or "tetrahydroindeno-annulated" PAHs.