Activation of the Vinylic C−Cl Bond by Complexation of Fe(CO)₃: Palladium-Catalyzed Coupling Reactions of (η⁴-Chlorodiene)tricarbonyliron Complexes^†

The reactions of 1-chloro- or 2-chloro-substituted (η4-1,3-cyclohexadiene)Fe(CO)3 complexes with terminal alkynes under the catalysis of PdCl2(PPh3)2/CuI at 45−60 °C led to the formation of the corresponding Sonogashira coupling products in 64−97% yields. The complexes also underwent smoothly the intermolecular Heck reactions with activated alkenes under the catalysis of Pd(OAc)2/PPh3 at 60 °C to afford the expected coupling products in 39−83% yields. On the other hand, the corresponding uncomplexed molecule 2-chloro-1,3-cyclohexadiene remained inert under the same reaction conditions. These results clearly demonstrated the strong activation effect of Fe(CO)3 on the oxidative cleavage of the vinylic C−Cl bond

Activation of the Vinylic C−Cl Bond by Complexation of Fe(CO)₃: Palladium-Catalyzed Coupling Reactions of (η⁴-Chlorodiene)tricarbonyliron Complexes^†

The reactions of 1-chloro- or 2-chloro-substituted (η4-1,3-cyclohexadiene)Fe(CO)3 complexes with terminal alkynes under the catalysis of PdCl2(PPh3)2/CuI at 45−60 °C led to the formation of the corresponding Sonogashira coupling products in 64−97% yields. The complexes also underwent smoothly the intermolecular Heck reactions with activated alkenes under the catalysis of Pd(OAc)2/PPh3 at 60 °C to afford the expected coupling products in 39−83% yields. On the other hand, the corresponding uncomplexed molecule 2-chloro-1,3-cyclohexadiene remained inert under the same reaction conditions. These results clearly demonstrated the strong activation effect of Fe(CO)3 on the oxidative cleavage of the vinylic C−Cl bond

Activation of the Vinylic C−Cl Bond by Complexation of Fe(CO)₃: Palladium-Catalyzed Coupling Reactions of (η⁴-Chlorodiene)tricarbonyliron Complexes^†

The reactions of 1-chloro- or 2-chloro-substituted (η4-1,3-cyclohexadiene)Fe(CO)3 complexes with terminal alkynes under the catalysis of PdCl2(PPh3)2/CuI at 45−60 °C led to the formation of the corresponding Sonogashira coupling products in 64−97% yields. The complexes also underwent smoothly the intermolecular Heck reactions with activated alkenes under the catalysis of Pd(OAc)2/PPh3 at 60 °C to afford the expected coupling products in 39−83% yields. On the other hand, the corresponding uncomplexed molecule 2-chloro-1,3-cyclohexadiene remained inert under the same reaction conditions. These results clearly demonstrated the strong activation effect of Fe(CO)3 on the oxidative cleavage of the vinylic C−Cl bond

Control of the Regioselectivity of Sulfonamidyl Radical Cyclization by Vinylic Halogen Substitution

The radical cyclization reactions of unsaturated sulfonamides were investigated. The photolysis of N-(4-halo-4-pentenyl)sulfonamides (X = I, Br, or Cl) with (diacetoxyiodo)benzene (DIB) and iodine at room temperature afforded exclusively the corresponding piperidines in 73−98% yield via 6-endo radical cyclization. On the other hand, the reactions of N-(5-halo-4-pentenyl)sulfonamides with DIB/I2 led to the only formation of the pyrrolidine products in 84−99% yield via 5-exo radical cyclization. The vinylic halogen substitution not only successfully inhibits the competing ionic iodocyclization process to allow the radical cyclization to proceed smoothly but also shows a remarkable effect in controlling the regioselectivity of cyclization

Visualization 2: Graphics processing unit–assisted real-time three-dimensional measurement using speckle-embedded fringe

Measurement result of a static box and a moving hand Originally published in Applied Optics on 01 August 2015 (ao-54-22-6865

Staged Self-Assembly of Colloidal Metastructures

We demonstrate sequential assembly of chemically patchy colloids such that their valence differs from stage to stage to produce hierarchical structures. For proof of concept, we employ ACB triblock spheres suspended in water, with the C middle band electrostatically repulsive. In the first assembly stage, only A–A hydrophobic attraction contributes, and discrete clusters form. They can be stored, but subsequently activated to allow B–B attractions, leading to higher-order assembly of clusters with one another. The growth dynamics, observed at a single particle level by fluorescence optical microscopy, obey the kinetics of stepwise polymerization, forming chains, pores, and networks. Between linked clusters, we identify three possible bond geometries, linear, triangular, and square, by an argument that is generalizable to other patchy colloid systems. This staged assembly strategy offers a promising route to fabricate colloidal assemblies bearing multiple levels of structural and functional complexity

Electronic Structure of Twisted Bilayers of Graphene/MoS₂ and MoS₂/MoS₂

Vertically stacked two-dimensional multilayer structures have become a promising prototype for functionalized nanodevices due to their wide range of tunable properties. In this paper we performed first-principles calculations to study the electronic structure of nontwisted and twisted bilayers of hybrid graphene/MoS₂ (Gr/MoS₂) and MoS₂/MoS₂. Both twisted bilayers of Gr/MoS₂ and MoS₂/MoS₂ show significant differences in band structures from the nontwisted ones with the appearance of the crossover between direct and indirect band gap and gap variation. More interestingly, the band structures of twisted Gr/MoS₂ with different rotation angles are very different from each other, while those of MoS₂/MoS₂ are very similar. The variation of band structure with rotation angle in Gr/MoS₂ is, indeed, originated from the misorientation-induced lattice strain and the sensitive band-strain dependence of MoS₂

Visualization 1: Graphics processing unit–assisted real-time three-dimensional measurement using speckle-embedded fringe

Measurement result of a shaking paper Originally published in Applied Optics on 01 August 2015 (ao-54-22-6865

Visualization 1: Adaptive step-size strategy for noise-robust Fourier ptychographic microscopy

The evolution of the amplitude reconstructions of an USAF resolution target with an adaptive step-size. Originally published in Optics Express on 05 September 2016 (oe-24-18-20724

Staged Self-Assembly of Colloidal Metastructures

We demonstrate sequential assembly of chemically patchy colloids such that their valence differs from stage to stage to produce hierarchical structures. For proof of concept, we employ ACB triblock spheres suspended in water, with the C middle band electrostatically repulsive. In the first assembly stage, only A–A hydrophobic attraction contributes, and discrete clusters form. They can be stored, but subsequently activated to allow B–B attractions, leading to higher-order assembly of clusters with one another. The growth dynamics, observed at a single particle level by fluorescence optical microscopy, obey the kinetics of stepwise polymerization, forming chains, pores, and networks. Between linked clusters, we identify three possible bond geometries, linear, triangular, and square, by an argument that is generalizable to other patchy colloid systems. This staged assembly strategy offers a promising route to fabricate colloidal assemblies bearing multiple levels of structural and functional complexity