The Sonogashira Coupling on Palladium Milling Balls—A new Reaction Pathway in Mechanochemistry

Utilizing direct mechanocatalytical conditions, the Sonogashira coupling was successfully performed on the surface of milling tools by using pure Pd and Pd coated steel balls. The optimization of co-catalyst forming additives led to a protocol, which generates quantitative yields under aerobic conditions for various substrates within as little as 90 minutes. Using state-of-the-art spectroscopic, diffractive, as well as in situ methods lead to the identification of a previously unknown and highly reactive complex of the co-catalyst copper. This new complex differs substantially from the known complexes in liquid phase Sonogashira couplings, proving that reaction pathways in mechanochemistry may differ from those in established synthetic procedures.     

Opportunities and Limitations of Nanoagrochemicals

Nanoagrochemicals conceived based on safe-by-design principles could provide, besides yield increases, real benefits for the environment due to lower losses of agrochemicals to wind drift and rainwater run-off, and lower toxicity to non-target organisms. As an emerging new technology rather than ‘just another’ active ingredient, nanoagrochemicals should be evaluated and compared to conventional products using multiple criteria, including the production costs, efficiency, mode of action, degradability, and (lack of) effects on non-target organisms. Current studies on nanopesticides suggest, on average, ca. 31 % more efficiency and ca. 43 % less toxicity on non-target organisms. Observations of a 5–10-fold increase in efficiency in laboratory studies need validation in the field. The most significant challenges for nanoagrochemicals today are to produce them at competitive costs and overcome the regulatory obstacles to register products containing nanomaterials.     

Tris-benzo[cd]indole Cyanine Enables the NIR-photosensitized Radical and Thiol-ene Polymerizations at 940 nm

A near-infrared-absorbing heptamethine ( HM⁺ ) incorporating three bulky benzo[cd]indole heterocycles was designed to efficiently prevent self-aggregation of the dye, which results in a strong enhancement of its photoinitiating reactivity as compared to a parent bis-benzo[cd]indole heptamethine ( HMCl⁺ ) used as a reference system. In this context, we highlight an efficient free-radical NIR-polymerization up to a 100 % acrylates C=C bonds conversion even under air conditions. Such an important initiating performance was obtained by incorporating our NIR-sensitizer into a three-component system leading to its self-regeneration. This original photoredox cycle was thoroughly investigated through the identification of each intermediary species using EPR spectroscopy.