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Selenium incorporation is a widely used strategy for achieving high mobility semiconductors for a variety of organic optoelectronic devices, but it has received less attention in organic electrochemical transistors (OECTs). Herein, we developed two polythiophene derivatives (Pg2T-S and Pg2T-SVS) containing different selenophene loadings, as well as a selenophene-free polythiophene (Pg2T-T) as the control. The effects of selenium substitution/incorporation on the optical, electrical, electrochemical, and OECT performance of polythiophene-based organic mixed ionic–electronic conductors are systematically investigated. We discovered that introduction of selenium increases quinoidal character and crystallinity, which is beneficial for charge transport but makes ion penetration more challenging. In contrast, increasing selenium content increases the dipole moment and ion–polymer interaction, which is helpful for ion doping and volumetric capacitance but detrimental to charge transport. Therefore, appropriate selenium content should be evaluated to balance the trade-off between charge transfer and volumetric capacitance. As a result, Pg2T-S with moderate selenium loading achieves a high μC* of 332.7 F cm−1 V−1 s−1 with increased μ of 1.31 cm2 V−1 s−1 and maintains the C* value of 254 F cm−3. It also has a quick τon/τoff of 10.76 ms/5.90 ms and outstanding operational stability. Further introducing selenium boosts the dipole moment and ion–polymer interaction and therefore increased C*, but suppressed μ, resulting in inefficient μC*. We indicated that systematic balancing of the effects of selenium incorporation is necessary for the development of mixed ionic–electronic conductors for high-performance OECTs. [ABSTRACT FROM AUTHOR]

Reductive elimination is a key step in Ni-catalysed cross-couplings, which is often considered to result in new covalent bonds. Due to the weak oxidizing ability of Ni(II) species, reductive eliminations from Ni(II) centers are challenging. A thorough mechanistic understanding of this process could inspire the rational design of Ni-catalysed coupling reactions. In this article, we give an overview of recent advances in the mechanistic study of reductive elimination from Ni(II) species achieved by our group. Three possible models for reductive elimination from Ni(II) species were investigated and discussed, including direct reductive elimination, electron density-controlled reductive elimination, and oxidation-induced reductive elimination. Notably, the direct reductive elimination from Ni(II) species often requires a high activation energy in some cases. In contrast, the electron density-controlled and oxidation-induced reductive elimination pathways can significantly enhance the driving force for reductive elimination, accelerating the formation of new covalent bonds. The intricate reaction mechanisms for each of these pathways are thoroughly discussed and systematically summarized in this paper. These computational studies showcase the characteristics of three models for reductive elimination from Ni(II) species, and we hope that it will spur the development of mechanistic studies of cross-coupling reactions.

A tandem palladium-catalyzed Sonogashira coupling, propargyl-allenyl isomerization, and [2+2] cycloaddition sequence between electron-deficient haloarenes and 1,8-diynylic ethers is developed. The reaction shows good functional tolerance and proceeds under mild conditions to provide a new profile of benzooxepane-fused cyclobutene derivatives in moderate to high yields with high selectivity. The reaction mechanism is validated both by experimental studies and DFT calculations.

Multivalent ligands hold promise for enhancing avidity and selectivity to simultaneously target multimeric proteins, as well as potentially modulating receptor signaling in pharmaceutical applications. Essential for these manipulations are nanosized scaffolds that precisely control ligand display patterns, which can be achieved by using polyproline oligo-helix macrocyclic nanoscaffolds via selective binding to protein oligomers and cell surface receptors. This work focuses on synthesis and structural characterization of different-sized polyproline tri-helix macrocyclic (PP3M) scaffolds. Through combined analysis of circular dichroism (CD), small- and wide-angle X-ray scattering (SWAXS), electron spin resonance (ESR) spectroscopy, and molecular modeling, a non-coplanar tri-helix loop structure with partially crossover helix ends is elucidated. This structural model aligns well with scanning tunneling microscopy (STM) imaging. The present work enhances the precision of nanoscale organic synthesis, offering prospects for controlled ligand positioning on scaffolds. This advancement paves the way for further applications in nanomedicine through selective protein interaction, manipulation of cell surface receptor functions, and developments of more complex polyproline-based nanostructures., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)