Tunable THz wave absorption by graphene-assisted plasmonic metasurfaces based on metallic split ring resonators

Journal of Nanoparticle Research - La(Ni0.75W0.25)O3 perovskite oxide was prepared via the sol–gel Pechini route. The pure crystalline phase was verified via X-ray diffraction measurements...     

Photocatalytic Difunctionalization of Vinyl Ureas by Radical Addition Polar Truce–Smiles Rearrangement Cascades

We report tandem alkyl-arylations and phosphonyl-arylations of vinyl ureas by way of a photocatalytic radical-polar crossover mechanism. Addition of photoredox-generated radicals to the alkene forms a new C−C or C−P bond and generates a product radical adjacent to the urea function. Reductive termination of the photocatalytic cycle generates an anion that undergoes a polar Truce–Smiles rearrangement, forming a C−C bond. The reaction is successful with a range of α-fluorinated alkyl sodium sulfinate salts and diarylphosphine oxides as radical precursors, and the conformationally accelerated Truce–Smiles rearrangement is not restricted by the electronic nature of the migrating aromatic ring. Formally the reaction constitutes an α,β-difuctionalisation of a carbon–carbon double bond, and proceeds under mild conditions with visible light and a readily available organic photocatalyst. The products are α,α-diaryl alkylureas typically functionalized with F or P substituents that may be readily converted into α,α-diaryl alkylamines.     

Dynamics of Miniature and High-Compliance Structures: Experimental Characterization and Modeling

Experimental Mechanics - The dynamic behavior of miniature and high-compliance structures is critical for their performance. However, their low stiffness and inertia bring significant challenges to...     

Introducing a Hydrogen‐Bond Donor into a Weakly Nucleophilic Brønsted Base: Alkali Metal Hexamethyldisilazides (MHMDS,M=Li,Na, K,Rb and Cs) with Ammonia

Alkali metal 1,1,1,3,3,3‐hexamethyldisilazide (MHMDSs) are one of the most utilised weakly nucleophilic Brønsted bases in synthetic chemistry and especially in natural product synthesis. Like lithium organics, they aggregate depending on the employed donor solvents. Thus, they show different reactivity and selectivity as a function of their aggregation and solvation state. To date, monomeric LiHMDS with monodentate donor bases was only characterised in solution. Since the first preparation of LiHMDS in 1959 by Wannagat and Niederprüm, all efforts to crystallise monomeric LiHMDS in the absence of chelating ligands failed. Herein, we present ammonia adducts of LiHMDS, NaHMDS, KHMDS, RbHMDS and CsHMDS with unprecedented aggregation motifs: 1) The hitherto missing monomeric key compound in the LiHMDS aggregation architectures. Monomeric crystal structures of trisolvated LiHMDS ( 1 ) and NaHMDS ( 2 ), showing unique intermolecular hydrogen bonds, 2) the unprecedented tetrasolvated KHMDS ( 3 ) and RbHMDS ( 4 ) dimers and 3) the disolvated CsHMDS ( 5 ) dimer with very close intermolecular Si?CH₃???Cs s‐block “agostic” interactions have been prepared and characterised by single‐crystal X‐ray structure analysis.     

On the relation between basis set convergence and electron correlation: a critical test for modern ab initio quantum chemistry on a ��mindless�� data set

The correlation of the only two error sources in the solution of the electronic Schrödinger equation is addressed: the basis set convergence (incompleteness) error (BSIE) and the electron correlation effect. The electron correlation effect and basis set incompleteness error are found to be correlated for all of the molecules in Grimme??s ??mindless?? data set (MB08-165). One can use an extrapolation to the HF or MP2 complete basis set (CBS) limit to see with which type of quantum chemical problem (??simple?? and ??hard??) the researcher is dealing. The origin of the slow convergence of the partial wave expansion can be the Kato cusp condition for electron?Celectron coalescence. Such an extrapolation is possible for many large molecular systems and would give the researcher an idea about the expected electron correlation level that would lead to the desired theoretical accuracy. In other words, it is possible to use not only the CBS energy value itself but the speed with which it is reached to get extra information about the molecular system under study.     

Structure of Supramers Formed by the Amphiphile Biotin-CMG-DOPE

The synthetic function-spacer-lipid (FSL) amphiphile biotin-CMG-DOPE is widely used for delicate ligation of living cells with biotin residues under physiological conditions. Since this molecule has an “apolar-polar-hydrophobic” gemini structure, the supramolecular organization is expected to differ significantly from the classical micelle. Its organization is investigated with experimental methods and molecular dynamics simulations (MDS). Although the linear length of a single biotin-CMG-DOPE molecule is 9.5 nm, the size of the dominant supramer globule is only 14.6 nm. Investigations found that while the DOPE tails form a hydrophobic core, the polar CMG spacer folds back upon itself and predominantly places the biotin reside inside the globule or planar layer. MDS demonstrates that <10 % of biotin residues on the highly water dispersible globules and only 1 % of biotin residues in layer coatings are in an linear conformation and exposing biotin into the aqueous medium. This explains why in biotin-CMG-DOPE apolar biotin residues both in water dispersible globules and coatings on solid surfaces are still capable of interacting with streptavidin.     

From a 2,1-Benzazaarsole to Elusive 1-Arsanaphthalenes in One Step

The 2,1-benzazaarsole ( 1 ) showed a diene-like reactivity towards selected alkynes RC≡CR (R=CO₂Me, C₅F₄N) thus forming 1-arsa-1,4-dihydro-iminonaphthalenes 2 a and 3 a as hardly isolable intermediates, that underwent facile CH→NH proton migration leading to before elusive substituted 1-arsanaphthalenes 2 b and 3 b that could be completely structurally characterized.