Exploring the Strain Effect in Single Particle Electrochemistry using Pd Nanocrystals

Tuning the surface strain of heterogeneous catalysts is recognized as a powerful strategy for tailoring their catalytic activity. However, a clear understanding of the strain effect in electrocatalysis at single-particle resolution is still lacking. Here, we explore the electrochemical hydrogen evolution reaction (HER) of single Pd octahedra and icosahedra with the same surface bounded {111} crystal facet and similar sizes using scanning electrochemical cell microscopy (SECCM). It is revealed that tensilely strained Pd icosahedra display significantly superior HER electrocatalytic activity. The estimated turnover frequency at −0.87 V vs RHE on Pd icosahedra is about two times higher than that on Pd octahedra. Our single-particle electrochemistry study using SECCM at Pd nanocrystals unambiguously highlights the importance of tensile strain on electrocatalytic activity and may offer new strategy for understanding the fundamental relationship between surface strain and reactivity.     

Photocatalytic C−C Cleavage of Methylenecyclobutanes for γ,δ-Unsaturated Aldehydes by Strain Release

Radical additions onto olefins have surfaced as an increasingly powerful strategy for the synthesis of difunctionalized scaffolds. However, despite of major advances, known approaches continue to be largely limited to two manifolds, namely 1,2-difunctionalization of alkenes and remote difunctionalization via hydrogen atom transfer (HAT). Herein, we describe a mechanistically distinct approach by photoinduced carbon-carbon (C−C) activation/ring-opening to access γ,δ-unsaturated aldehydes from methylenecyclobutanols and sulfonyl chlorides by strain release. Remarkably, the sulfonyl motif on the products was easily removed by another photocatalytic process, which enabled the concise assembly of the natural product alatanone A. The synthetic utility of our approach was reflected by versatile functional group tolerance, ample substrate scope, and scalability. The photocatalysis represents a conceptually distinct alternative to existing approaches for remote 1,4-diversifications, with a double bond remaining in the thus obtained products.     

Tensile property of cord reinforced rubber composites laminate double lap jointEI北大核心CSCD

According to the structural connection form of cord reinforced rubber composite，structural test samples with different lapping process parameters were designed and prepared. The dynamic and static tensile properties were studied by using two-dimensional digital image technology. The test results were as follows：The stiffness and tensile strength of double lap composites joints increased as the strain rate increasing，while the elongation at break unchanged. Compared with the no-lap samples，the tensile strength of the double lap composites sample was reduced by nearly 50%，and with the increase of the lap width，the elongation at break gradually decreased. The samples with lap width of 65 mm decreased by 24% compared with the no-lap ones. Compared with the elastic modulus of stage II，the elastic modulus of stage III increased significantly，that of the no-lap samples increased by 3 times，that of the lap samples were doubled，and the amplification of elastic modulus decreased with the increase of strain rate. © 2023, Youke Publishing Co.,Ltd. All rights reserved.     

Cation-Promoted Strain-Release-Driven Access to Functionalized Azetidines from Azabicyclo[1.1.0]butanes

Access to 1,3-functionalized azetidines through a diversity-oriented approach is highly sought-after for finding new applications in drug-discovery. To this goal, strain-release-driven functionalization of azabicyclo[1.1.0]-butane (ABB) has generated significant interest. Through appropriate N-activation, C3-substituted ABBs are shown to render tandem N/C3-fucntionalization/rearrangement, furnishing azetidines; although, modalities of such N-activation vis-à-vis N-functionalization remain limited to selected electrophiles. This work showcases a versatile cation-driven activation strategy of ABBs. And capitalizes on the use of Csp³ precursors amenable to forming reactive (aza)oxyallyl cations in situ. Herein, N-activation leads to formation of a congested C−N bond, and effective C3 activation. The concept was extended to formal [3+2] annulations involving (aza)oxyallyl cations and ABBs, leading to bridged bicyclic azetidines. Besides the fundamental appeal of this new activation paradigm, operational simplicity and remarkable diversity should engender its prompt use in synthetic and medicinal chemistry.