Rhodium(II)-Catalyzed N–H Insertions of Carbenes under Mechanochemical Conditions

Under mechanochemical conditions in a mixer mill, Rh2(OAc)4 catalyzes the reaction between aryldiazoesters and anilines to give α-amino esters. The process proceeds under mild conditions and is insensitive to air. It is solvent-free and scalable. A broad substrate scope, short reaction times, operational simplicity, and good functional group tolerance are additional salient features of this protocol

Tuning Electromagnetic Interference Shielding Performance through Controlled Alignment of Ni Nanowires in Soft PDMS Composites

Efficient dispersion of nanostructured fillers in thermoplastic polymers and elastomers remains an open challenge, and unless it is addressed, the potential utilization of conducting and magnetic fillers influencing the electronic properties of soft nanocomposites could not be properly assessed. Herein, we present a unique approach to address this challenge by constructing a microstructural fence using aligned magnetic networks of Ni nanowires in the direction of the applied external magnetic field, followed by flow-induced secondary in-planar alignment of multiwalled carbon nanotubes during the curing of the soft poly­(dimethylsiloxane) (PDMS) elastomer. This mutually perpendicular arrangement offers unique magnetoconducting features to the soft elastomer matrix with moderately high conductivity, which is the key to superior electromagnetic shielding performance. The unique conformation of mutually perpendicular positions of both nanofillers in the bulk PDMS composites results in enhanced electromagnetic interference shielding performance (−28 dB) primarily through an absorption (80%) mechanism, driven primarily by the maximized interaction with incident electromagnetic waves inside the soft elastomer. Fundamental insights into the governing viscoelastic responses of these elastomer composites were gained through oscillatory rheological studies that investigate interparticle attraction within a quasi-solid network

Tuning the Shape Anisotropy and Electromagnetic Screening Ability of Ultrahigh Magnetic Polymer and Surfactant-Capped FeCo Nanorods and Nanocubes in Soft Conducting Composites

Herein, we demonstrate that very high electromagnetic (EM) shielding efficiency can be achieved by dispersing nanoengineered FeCo anisometric nanostructures in a poly­(vinylidene difluoride) matrix in the presence of conductive nanofillers (multiwall carbon nanotubes, MWCNTs). The FeCo nanorods (∼800 nm) and nanocubes (∼100 nm) were fabricated by a facile surfactant and polymer-assisted one-pot borohydride reduction method. The growth mechanism depicted a two-directional growth for cubes, whereas for nanorods, a unidirectional growth pattern across the (110) plane was evident. A total shielding effectiveness (SE_T) of −44 dB at 18 GHz was achieved for a particular combination of FeCo nanorods and MWCNT, and for nanocube-based composites, it was found to be −39 dB at 18 GHz. It was observed from zero field cooled-field cooled curves that the samples displayed room temperature ferromagnetism. An excellent correlation between high aspect ratio FeCo nanorod and superior EM absorption (89%) was explored, pertaining to the fact that nanorods possessed higher magnetic saturation (177.1 emu/g) and coercivity (550 Oe) in contrast to the nanocubes with similar composition. Furthermore, theoretical insight into the mechanism revealed a high degree of interface scattering between conductive MWCNT and magnetic loss components, giving rise to an excellent synergy between magnetic and dielectric parts

Wool-Ball-Type Core-Dual-Shell FeCo@SiO₂@MWCNTs Microcubes for Screening Electromagnetic Interference

Engineered nanostructure-reinforced lightweight polymer composites with superior electromagnetic (EM) shielding effectiveness (SE_T) are widely employed in high-end applications such as aerospace and microelectronic devices. Recently, carbon nanotube-based three-dimensional nanostructures have shown enormous potential due to unmatched processability, mechanical, and electronic properties. In this study, we present for the first time, highly permeable FeCo-based core-double shell <i>wool-ball</i>-type microcubes chemically enclosed by dielectric silica and conducting multiwalled carbon nanotubes (MWCNTs) sequentially; the resulting reinforced nanocomposites with low filler loading produced superior SE_T of −35 dB at 18 GHz for a specimen of 3 mm thickness. The excellent dispersion of microstructures in the soft matrix owing to the encapsulation of hard FeCo magnets by MWCNTs ensures low density and excellent flexibility for high-precision applications. The nanoengineered core-dual shell strategy for fabricating magnetic-dielectric-conducting microcubes ensures strong magnetic loss, coupled with dielectric and conduction loss, respectively, from SiO₂ and MWCNT shells. This approach, being unique in terms of nanofabrication and subsequent formulation of lightweight flexible composites, demonstrates a highly efficient way toward designing advanced nanocomposites for cutting-edge shielding application

Stabilizing the [RSn(μ₂‑O)SnR] Motif through Intramolecular N→Sn Coordination. Synthesis and Characterization of [(RSn)₂(μ₂‑O)(μ₂‑FcCOO)₂(η-FcCOO)₂]·THF and {(RSn)₂(μ₂‑O)[(<i>t-</i>BuO)₂PO₂]₂Cl₂}·THF·2H₂O (R = 2‑(Phenylazo)phenyl)

The reactions of RSnCl₃ (<b>1</b>; R = 2-(phenylazo)­phenyl) with FcCOOH or di-<i>tert</i>-butyl phosphate in refluxing THF afforded the monoorganodistannoxanes [(RSn)₂(μ₂-O)­(μ₂-FcCOO)₂(η-FcCOO)₂]·THF (<b>2</b>) and {(RSn)₂(μ₂-O)­[(<i>t-</i>BuO)₂PO₂]₂Cl₂}·THF·2H₂O (<b>3</b>). The molecular structure of <b>2</b> contains seven-coordinate tin centers in a distorted-pentagonal-bipyramidal geometry, while <b>3</b> contains six-coordinate tin centers in a distorted-octahedral geometry. In the dinuclear compounds <b>2</b> and <b>3</b> the two tin centers are bridged by a μ₂-O unit, affording a rare Sn–O–Sn motif among monoorganostannoxanes. In addition, each tin is also intramolecularly coordinated to the nitrogen atom of the 2-phenylazophenyl substituent (N→Sn). Further, in <b>2</b>, the two tin centers are bridged by two isobidentate ferrocenecarboxylate ligands; each tin center also is bound to a chelating ferrocenecarboxylate ligand. On the other hand, in <b>3</b>, while the two tin centers are bridged by two isobidentate di-<i>tert</i>-butyl phosphate ligands, each tin center also has a terminal chloride ligand

Stabilizing the [RSn(μ₂‑O)SnR] Motif through Intramolecular N→Sn Coordination. Synthesis and Characterization of [(RSn)₂(μ₂‑O)(μ₂‑FcCOO)₂(η-FcCOO)₂]·THF and {(RSn)₂(μ₂‑O)[(<i>t-</i>BuO)₂PO₂]₂Cl₂}·THF·2H₂O (R = 2‑(Phenylazo)phenyl)

The reactions of RSnCl₃ (<b>1</b>; R = 2-(phenylazo)­phenyl) with FcCOOH or di-<i>tert</i>-butyl phosphate in refluxing THF afforded the monoorganodistannoxanes [(RSn)₂(μ₂-O)­(μ₂-FcCOO)₂(η-FcCOO)₂]·THF (<b>2</b>) and {(RSn)₂(μ₂-O)­[(<i>t-</i>BuO)₂PO₂]₂Cl₂}·THF·2H₂O (<b>3</b>). The molecular structure of <b>2</b> contains seven-coordinate tin centers in a distorted-pentagonal-bipyramidal geometry, while <b>3</b> contains six-coordinate tin centers in a distorted-octahedral geometry. In the dinuclear compounds <b>2</b> and <b>3</b> the two tin centers are bridged by a μ₂-O unit, affording a rare Sn–O–Sn motif among monoorganostannoxanes. In addition, each tin is also intramolecularly coordinated to the nitrogen atom of the 2-phenylazophenyl substituent (N→Sn). Further, in <b>2</b>, the two tin centers are bridged by two isobidentate ferrocenecarboxylate ligands; each tin center also is bound to a chelating ferrocenecarboxylate ligand. On the other hand, in <b>3</b>, while the two tin centers are bridged by two isobidentate di-<i>tert</i>-butyl phosphate ligands, each tin center also has a terminal chloride ligand

Absorption-Dominated Electromagnetic Wave Suppressor Derived from Ferrite-Doped Cross-Linked Graphene Framework and Conducting Carbon

To minimize electromagnetic (EM) pollution, two key parameters, namely, intrinsic wave impedance matching and intense absorption of incoming EM radiation, must satisfy the utmost requirements. To target these requirements, soft conducting composites consisting of binary blends of polycarbonate (PC) and poly­(vinylidene fluoride) (PVDF) were designed with doped multiwalled carbon nanotubes (MWCNTs) and a three-dimensional cross-linked graphene oxide (GO) framework doped with ferrite nanoparticles. The doping of α-MnO₂ onto the MWCNTs ensured intrinsic wave impedance matching in addition to providing conducting pathways, and the ferrite-doped cross-linked GO facilitated the enhanced attenuation of the incoming EM radiation. This unique combination of magnetodielectric coupling led to a very high electromagnetic shielding efficiency (SE) of −37 dB at 18 GHz, dominated by absorption-driven shielding. The promising results from the composites further motivated us to rationally stack individual composites into a multilayer architecture following an absorption–multiple reflection–absorption pathway. This resulted in an impressive SE of −57 dB for a thin shield of 0.9-mm thickness. Such a high SE indicates >99.999% attenuation of the incoming EM radiation, which, together with the improvement in structural properties, validates the potential of these materials in terms of applications in cost-effective and tunable solutions