Driving Force Dependence of Electron Transfer from Electronically Excited [Ir(COD)(µ-Me2pz)]2 to Photo-Acid Generators.

We report the rates of electron transfer (ET) reactions of electronically excited [Ir(COD)(µ-Me2pz)]2 with onium salt photoacid generators (PAGs). The reduction potentials of the PAGs span a large electrochemical window that allows determination of the driving force dependence of the ET reactions. Rate constants of ET from electronically excited [Ir(COD)(µ-Me2pz)]2 to onium PAGs are determined by the reaction driving force until the diffusion limit in acetonitrile is reached.

Directing self-assembly of nanoscopic cylindrical diblock brush terpolymers into films with desired spatial orientations: expansion of chemical composition scope.

Diblock brush terpolymers (DBTs) with different fluorinated methacrylate-based block segments are synthesized through sequential ring-opening metathesis polymerizations and are used to prepare polymer thin films with predictable film thicknesses. These DBTs exhibit preferable substrate vertical alignments within the films, induced by the relatively lower surface energy of the fluorinated structural components, together with the overall cylindrical morphology of the brush architecture.

Generation of powerful tungsten reductants by visible light excitation.

The homoleptic arylisocyanide tungsten complexes, W(CNXy)6 and W(CNIph)6 (Xy = 2,6-dimethylphenyl, Iph = 2,6-diisopropylphenyl), display intense metal to ligand charge transfer (MLCT) absorptions in the visible region (400-550 nm). MLCT emission (λ(max) ≈ 580 nm) in tetrahydrofuran (THF) solution at rt is observed for W(CNXy)6 and W(CNIph)6 with lifetimes of 17 and 73 ns, respectively. Diffusion-controlled energy transfer from electronically excited W(CNIph)6 (*W) to the lowest energy triplet excited state of anthracene (anth) is the dominant quenching pathway in THF solution. Introduction of tetrabutylammonium hexafluorophosphate, [Bu(n)4N][PF6], to the THF solution promotes formation of electron transfer (ET) quenching products, [W(CNIph)6](+) and [anth](•-). ET from *W to benzophenone and cobalticenium also is observed in [Bu(n)4N][PF6]/THF solutions. The estimated reduction potential for the [W(CNIph)6](+)/*W couple is -2.8 V vs Cp2Fe(+/0), establishing W(CNIph)6 as one of the most powerful photoreductants that has been generated with visible light.

Nanoscopic cylindrical dual concentric and lengthwise block brush terpolymers as covalent preassembled high-resolution and high-sensitivity negative-tone photoresist materials.

We describe a high-resolution, high-sensitivity negative-tone photoresist technique that relies on bottom-up preassembly of differential polymer components within cylindrical polymer brush architectures that are designed to align vertically on a substrate and allow for top-down single-molecule line-width imaging. By applying cylindrical diblock brush terpolymers (DBTs) with a high degree of control over the synthetic chemistry, we achieved large areas of vertical alignment of the polymers within thin films without the need for supramolecular assembly processes, as required for linear block copolymer lithography. The specially designed chemical compositions and tuned concentric and lengthwise dimensions of the DBTs enabled high-sensitivity electron-beam lithography of patterns with widths of only a few DBTs (sub-30 nm line-width resolution). The high sensitivity of the brush polymer resists further facilitated the generation of latent images without postexposure baking, providing a practical approach for controlling acid reaction/diffusion processes in photolithography.