The first copper-catalyzed ring-opening electrophilic trifluoromethylation and trifluoromethylthiolation of cyclopropanols to form Csp3-CF3 and Csp3-SCF3 bonds have been realized. These transformations are efficient for the synthesis of β-CF3 and β-SCF3 substituted carbonyl compounds that are otherwise challenging to access. The reaction conditions are mild and tolerate a wide range of functional groups. Application to a concise synthesis of LY2409021, a glucagon receptor antagonist that is used in clinical trial for type 2 diabetes mellitus, is reported as well.
Nanolithographic printing by direct laser writing (DLW) photopolymerization has attracted increased attention in recent years, as the speed of this printing has increased, while the feature sizes that have been realized have decreased well into the nanoscale regime. Specifically, isopropyl thioxanthone (ITX) has been utilized as one of the common photoinitiators in DLW polymerization processes because of its high-efficiency photoinitiating abilities and its ability to have its initiation properties inhibited through the application of a second wavelength of light. However, improved photoinitiating materials that are built from this successful archetype are required, by both academic and industrial circles, if advanced highthroughput nanomanufacturing techniques are to be implemented. Here, nextgeneration thioxanthone-based photoinitiators with tailored optical and charge transfer properties were computationally designed and subsequently synthesized. Particularly, branches with specifically modulated electron donor and electron acceptor qualities, relative to the ITX core, were coupled to the initial thioxanthone substrate. After having their molecular and optical properties characterized in full, it was evident that these initiators possessed a clear advancement in terms of photopolymerization initiation relative to ITX. As such, a champion photoinitiator chemistry was brought forward to demonstrate enhanced two-photon polymerization DLW such that superresolution properties were exhibited. In this way, we introduce a clear means by which to systematically design future photoinitiators for enhanced two-photon polymerization DLW nanoprinting processes.
We document the design, synthesis, and characterization of the first low glass transition temperature, n-type (i.e., preferentially-reduced) radical polymer.
Incorporating temperature- and air-stable organic radical
species
into molecular designs is a potentially advantageous means of controlling
the properties of electronic materials. However, we still lack a complete
understanding of the structure–property relationships of organic
radical species at the molecular level. In this work, the charge transport
properties of (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO)
radical-containing nonconjugated molecules are studied using single-molecule
charge transport experiments and molecular modeling. Importantly,
the TEMPO pendant groups promote temperature-independent molecular
charge transport in the tunneling region relative to the quenched
and closed-shell phenyl pendant groups. Results from molecular modeling
show that the TEMPO radicals interact with the gold metal electrodes
near the interface to facilitate a high-conductance conformation.
Overall, the large enhancement of charge transport by incorporation
of open-shell species into a single nonconjugated molecular component
opens exciting avenues for implementing molecular engineering in the
development of next-generation electronic devices based on novel nonconjugated
radical materials.
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