The Design of a Novel 2-42 GHz MEMS True-Time Delay Network for Wideband Phased Array Systems.

This article presents the design method of a compact MEMS switched-line true-time delay line (TTDL) network over a wide frequency range extending from 2 to 42 GHz using TTDL units. The TTDL units, namely the cascading radio frequency micro-electromechanical system (RF MEMS) switches and GCPW, were employed in the proposed TTDL network to improve the delay-bandwidth product (DBW) while maintaining its compact size and low delay variation (DV). For comparison, a theoretical analysis of the RF MEMS switch was performed while observing the switch performance with various top electrodes. The MEMS TTDL network has a compact size of 5 mm × 5 mm, with a maximum delay of 200 ps and a minimum of 30 ps. The maximum insertion loss of 9 states is 10 dB, and the in/out return loss is better than 20 dB across 2-42 GHz. The group delay variations are within ±2.5% for all the delay states over the operating frequency range. To the best of our knowledge, the proposed TTDL network obtains the most control bits among the TTDL networks offered to date.

Fluorohydroxylation and Hydration Reactions of para-Quinone Methides Promoted by Selectfluor.

Selectfluor-promoted vicinal fluorohydroxylation and hydration reaction of para-quinone methides (p-QMs) were described, affording vicinal fluorohydrins and ketone/ether products in high yields. The hydration products were highly controlled by the electronic properties of substituents in the aromatic ring, and simultaneously, the amount of Selectfluor was completely different during the synthesis of ketone/ether products. This reaction also represents the first fluorohydroxylation of p-QMs, and the wide range of p-QMs makes the vicinal fluorohydroxylation of great significance.

Successive syntheses and magnetic properties of homodinuclear lanthanide macrocyclic complexes.

A series of homodinuclear ß-diketone lanthanide(III) complexes, formulated as [(acac)4Ln2(L1)] (Ln3+ = Dy3+ (1), Tb3+ (2), and Gd3+ (3), respectively) were first synthesized based on a closed-macrocyclic ligand (H2L1) derived from the [2 + 2] cyclocondensation of 4-tert-butyl-2,6-diformylphenol and o-phenylenediamine in the presence of lanthanide acetylacetonates. Subsequently, by using the above compounds as building blocks to assemble directly with another Schiff base ligand, N,N'-bis(5-chlorosalicylidene)-o-phenylenediamine (H2L2), three new homodinuclear sandwich-type lanthanide complexes with the general formula [Ln2(L1)(L2)2] (Ln3+ = Dy3+ (4), Tb3+ (5), and Gd3+ (6), respectively) were further designed and prepared. Single-crystal X-ray analyses show that the central Ln3+ ion adopts a distorted square antiprism conformation with D4d local symmetry. Magnetic studies reveal ferromagnetic interaction between Dy3+ and Tb3+ centres and zero-field slow relaxation of magnetization for Dy complexes 1 and 4. The corresponding magneto-structural correlations of SMMs 1 and 4 were further discussed by theoretical calculations and with experimental outcomes.

Copper-Catalyzed Annulation Reaction of Alkenes and N-Alkyl(aryl)-1-(methylthio)-2-nitroethenamine: an Approach for the Synthesis of Isoxazole Derivatives.

A copper-catalyzed annulation reaction to access a variety of isoxazoles from alkenes and oxazete in situ generated from N-alkyl(aryl)-1-(methylthio)-2-nitroethenamine was reported. A plausible mechanism underlying the formation of the product was proposed, which represented a new approach for the construction of isoxazolines. This reaction was capable of tolerating alkenes bearing various substituents, which showed a relatively broad substrate scope with good functional group compatibility.

Controllable syntheses and magnetic properties of novel homoleptic triple-decker lanthanide complexes.

Four novel homoleptic triple-decker lanthanide complexes, [Ln2(L)(Cl-salphen)2]·0.5ClCH2CH2Cl (Ln3+ = Gd3+ (1), Ho3+ (2), Tb3+ (3), and Dy3+ (4)), have been designed and synthesized based on a Schiff base ligand N,N'-bis(5-chlorosalicylidene)-o-phenylenediamine (Cl-salphenH2) and the building blocks [(acac)4Ln2(L)]; these complexes were derived from a closed-macrocyclic ligand (H2L) obtained by the [2 + 2] template condensation of 2,6-diformyl-4-methylphenol and 1,3-diaminopropane in the presence of lanthanide acetylacetonates. Single-crystal X-ray analyses show that central Ln3+ ions adopt distorted square antiprism conformations with D4d symmetry. Theoretical analysis and magnetic measurements reveal that Dy complex 4 behaves as a typical SMM with the characteristics of slow magnetic relaxation behavior and intermetallic ferromagnetic interaction.

Syntheses, structures, and magnetic properties of homodinuclear lanthanide complexes based on dinucleating Schiff base ligands.

The first two families of homodinuclear lanthanide(III) complexes, formulated as [(L(OEt))2Ln2(L1)] and [(LOEt)2Ln2(L2)] (Ln(3+) = Dy(3+), Tb(3+), Ho(3+), Gd(3+), and Y(3+); L1(4-) = 2,2',2'',2'''-[1,2,4,5-benzenetetrayltetrakis(nitrilomethylidyne)]tetrakisphenolate; L2(4-) = 2,2',2'',2'''-[[1,1'-biphenyl]-3,3',4,4'-tetrayltetrakis(nitrilomethylidyne)]tetrakis(4-chlorophenolate); L(OEt)(-) = (η(5)-cyclopentadienyl)tris(diethylphosphito-p)cobaltate(III)), were successfully synthesized based on Kläui's tripodal building block NaL(OEt) and two dinucleating Schiff base ligands, H(4)L1 and H(4)L2, respectively. Single-crystal X-ray analyses show that these lanthanide complexes have two seven-coordinated metal binding sites, linked to each other with a phenyl or biphenyl bridge. Variable temperature dc magnetic measurements reveal the weakly antiferromagnetic coupling between paramagnetic lanthanide ions, while ac magnetic data exhibit the field-induced relaxation of magnetization for the corresponding Dy2 complexes 1 and 6. A further magnetic dilution study for 1 suggests that the slow magnetic relaxation originates from the single-ion magnetic behaviour of Dy(3+) ions.

3,5-Dibromo-4-oxo-2,2,6,6-tetra-methyl-piperidin-1-yl oxide.

In the title compound, C(9)H(14)Br(2)NO(2), the substituted ring exhibits a chair conformation. A crystallographic mirror plane, passing through the N atom, the O atoms and the C atom in the 4-position, bis-ects the mol-ecule.