Zhengong Meng

Effect of butterfly-shaped sulfur-bridged ligand and counter anions on the catalytic activity and diastereoselectivity of organobismuth complexes

In the direct Mannich reaction and synthesis of α,β-unsaturated ketones, the use of organobismuth complexes as catalysts leads to high diastereoselectivity and products of single trans conformation. In this paper, we illustrate the relationship between structure and catalytic activity as well as diastereoselectivity of organobismuth complexes having a 5,6,7,12-tetrahydrodibenz [c,f][1,5]thiobismocine framework as well as bearing a butterfly-shaped sulfur-bridged ligand and tunable anions. With the exposed bismuth center acting as a Lewis acid site and the uncoordinated lone pair electrons of sulfur as a Lewis base site, the cationic organobismuth complexes work as bifunctional Lewis acid/base catalysts. Due to the steric influence of the butterfly-shaped structure and synergistic effect of Lewis acid and Lewis base centers, the complexes can direct substrate attack in organic synthesis. By adjusting the electron-withdrawing ability of the counter anions, the S-Bi bond strength can be regulated, leading to a significant change in Lewis acidity and Lewis basicity as well as catalytic activity. Through synergistic modulation of the above effects, one can control the diastereoselectivity of the organobismuth complexes for the generation of a single diastereoisomer.

Facile separation catalyst system: direct diastereoselective synthesis of (E)-α,β-unsaturated ketones catalyzed by an air-stable Lewis acidic/basic bifunctional organobismuth complex in ionic liquids

The catalyst system that comprises an air-stable bifunctional Lewis acidic/basic organobismuth complex and [Bmim]BF4 is highly efficient in the cross-condensation of aldehydes with ketones. Through switching the reaction from homogeneous to heterogeneous, the system shows facile separation ability and facile reusability.

Nanopatterned L10-FePt nanoparticles from single-source metallopolymer precursors for potential application in ferromagnetic bit-patterned media magnetic recording

Bit-patterned media (BPM) with a precise stoichiometry ratio of Fe and Pt atoms are promising for future high areal density magnetic recording. Here, we report a new FePt-containing metallopolymer P as the single-source precursor for the synthesis of magnetic metal alloy nanoparticles. This polymer was synthesized from a random copolymer poly(styrene-4-ethynylstyrene) PES-PS and the bimetallic precursor TPy-FePt ([Pt(4′-ferrocenyl-(N^N^N))Cl]Cl) by the CuI-catalyzed dehydrohalogenation. After pyrolysis of P, the stoichiometry of Fe and Pt atoms in the synthesized nanoparticles is nearly close to 1 : 1, which is more precise than that by using TPy-FePt as the precursor. Also, polymer P is more suitable for patterning by high-throughput nanoimprint lithography (NIL) compared to TPy-FePt. Ferromagnetic nanolines, potentially useful for fabricating bit-patterned magnetic recording media, were successfully obtained from P and fully characterized.

Additive and Photochemical Manufacturing of Copper

In recent years, 3D printing technologies have been extensively developed, enabling rapid prototyping from a conceptual design to an actual product. However, additive manufacturing of metals in the existing technologies is still cost-intensive and time-consuming. Herein a novel platform for low-cost additive manufacturing is introduced by simultaneously combining the laser-induced forward transfer (LIFT) method with photochemical reaction. Using acrylonitrile butadiene styrene (ABS) polymer as the sacrificial layer, sufficient ejection momentum can be generated in the LIFT method. A low-cost continuous wave (CW) laser diode at 405 nm was utilized and proved to be able to transfer the photochemically synthesized copper onto the target substrate. The wavelength-dependent photochemical behaviour in the LIFT method was verified and characterized by both theoretical and experimental studies compared to 1064 nm fiber laser. The conductivity of the synthesized copper patterns could be enhanced using post electroless plating while retaining the designed pattern shapes. Prototypes of electronic circuits were accordingly built and demonstrated for powering up LEDs. Apart from pristine PDMS materials with low surface energies, the proposed method can simultaneously perform laser-induced forward transfer and photochemical synthesis of metals, starting from their metal oxide forms, onto various target substrates such as polyimide, glass and thermoplastics.

Photochemical Copper Coating on 3D Printed Thermoplastics

3D printing using thermoplastics has become very popular in recent years, however, it is challenging to provide a metal coating on 3D objects without using specialized and expensive tools. Herein, a novel acrylic paint containing malachite for coating on 3D printed objects is introduced, which can be transformed to copper via one-step laser treatment. The malachite containing pigment can be used as a commercial acrylic paint, which can be brushed onto 3D printed objects. The material properties and photochemical transformation processes have been comprehensively studied. The underlying physics of the photochemical synthesis of copper was characterized using density functional theory calculations. After laser treatment, the surface coating of the 3D printed objects was transformed to copper, which was experimentally characterized by XRD. 3D printed prototypes, including model of the Statue of Liberty covered with a copper surface coating and a robotic hand with copper interconnections, are demonstrated using this painting method. This composite material can provide a novel solution for coating metals on 3D printed objects. The photochemical reduction analysis indicates that the copper rust in malachite form can be remotely and photo-chemically reduced to pure copper with sufficient photon energy.

Additive Manufacturing of Cobalt-Based Organic Ferromagnetic Materials

Clogging problems from the aggregation of dispersed solutes have hindered the successful application of inkjet printing for patterning ferromagnetic materials. Native ferromagnetic ink with complete solubility and proper surface tension for inkjet printing has been lacking. Here, we report a metal-organic molecule with absolute solubility in dimethylformamide (DMF) solvent, which can be successfully patterned using state-of-art inkjet printing technologies. The jetting parameters for this ferromagnetic ink were systemically optimized and a series of patterns were successfully made on a variety of substrates. These patterned ferromagnetic 2.5-dimensional structures showed ferromagnetic properties as experimentally verified.

Complex assembly from planar and twisted π-conjugated molecules towards alloy helices and core-shell structures

Integrating together two dissimilar π-conjugated molecules into controlled complex topological configurations remains a largely unsolved problem owing to the diversity of organic species and their respective different assembly features. Here, we find that two structurally similar organic semiconductors, 9,10-bis(phenylethynyl)anthracene (BA) and 5,12-bis(phenylethynyl)naphthacene (BN), co-assemble into two-component helices by control of the growth kinetics as well as the molar ratio of BA/BN. The helical superstructures made of planar and twisted bis(phenylethynyl) derivatives can be regarded as (BA)x(BN)1−x alloys, which are formed due to compatible structural relationship between BA and BN. Moreover, epitaxial growth of (BA)x(BN)1−x alloy layer on the surface of BA tube to form BA@(BA)x(BN)1−x core-shell structure is also achieved via a solute exchange process. The precise control over composition and morphology towards organic alloy helices and core-shell microstructures opens a door for understanding the complex co-assembly features of two or more different material partners with similar structures.Manipulating the assembly of π-conjugated organic molecules into alloys to control composition and shape remains a largely unsolved problem. Here the authors show the co-assembly of two structurally similar organic semiconductors into two-component helices by control of their growth kinetics as well as the molar ratio of the building blocks.

Patterning of L1(0) FePt nanoparticles with ultra-high coercivity for bit-patterned media

L10-ordered FePt nanoparticles (NPs) with ultra-high coercivity were directly prepared from a new metallopolyyne using a one-step pyrolysis method. The chemical ordering, morphology and magnetic properties of the as-synthesized FePt NPs have been studied. Magnetic measurements show the coercivity of these FePt NPs is as high as 3.6 T. Comparison of NPs synthesized under the Ar and Ar/H2 atmospheres shows that the presence of H2 in the annealing environment influences the nucleation and promotes the growth of L10-FePt NPs. Application of this metallopolymer for bit-patterned media was also demonstrated using nanoimprint lithography.