Iodine-catalyzed cycloalkenylation of dihydroquinolines and arylamines through a reaction with cyclic ketones under neat conditions

An iodine-catalyzed direct cycloalkenylation of dihydroquinolines and arylamines has been developed. This method consists of a Friedel–Crafts reaction between dihydroquinolines (or arylamines) and cyclic ketones in which the double bond is selectively generated throughout the course of the reaction resulting in a direct cycloalkenylation, under neat conditions.     

Surface and structural analysis of epitaxial La1−xSrx (Mn1−yCoy)zO3 films

In the present study were studied the ferromagnetic La_1−xSr_x (Mn_1−yCo_y)_zO₃ (LSMCO) films with Co content y = 0 to 0.18, grown on LaAlO₃ substrates by advantageous pulsed-injection metalorganic chemical vapor deposition technique. The LSMCO films exhibit negative colossal magnetoresistance effect; therefore, they are interesting as potential material for the applications in magnetic field sensing. The changes of lattice volume in the investigated LSMCO films were monitored by X-ray diffraction measurements revealing a transition from tensile to compressive strain with increase of Co content. Additionally, from the atomic force microscopy images, the surface smoothening with increase of y was determined. Despite the reduction of the out-of-plane lattice parameter of LSMCO, the increase of lattice volume in the whole Co-doping range was observed. The X-ray photoelectron spectroscopy combined with Ar⁺ ion sputtering was used for the investigation of chemical composition of the LSMCO films and demonstrated the change and redistribution of oxidation states of Mn and Co on the surface and in the volume of the films. Regardless of the structural changes and charge distribution of Co and Mn cations, epitaxial LSMCO exhibits ferromagnetic properties and magnetoresistance values increases with augmenting Co content in the range of y = 0 to 0.18.     

Synthesis, Characterization and Thermal Studies of Some Iron(III) Complexes of o-Vanillin Oxime

Iron(III) complexes of o-vanillin oxime have been synthesized and characterized by different physicochemical techniques. The complexes containing thiocyanate, iodide and sulphate ionshave been subjected to non-isothermal decomposition studies in N₂ using TGand DTG techniques. The kinetic parameters for both stages of decomposition of these complexes were evaluated by weighted least-squares method using the general approach as well as the Coats–Redfern and Horowitz–Metzger equations. The results indicate that the values of kinetic parameters obtained by these three different approaches agree well. This revised version was published online in July 2006 with corrections to the Cover Date.     

Discrete Molecular Copper(II) Complex for Efficient Piezoelectric Energy Harvesting Above Room-Temperature

Developing robust, wearable, and biocompatible energy harvesting devices with bulk oxides (ceramics and perovskites) is extremely hard to achieve due to their zero mechanical flexibility, heavy metal toxicity, and tunability of properties. Alternatively, discrete inorganic complexes can be an excellent choice to overcome the above-stated issues, thanks to appropriate molecular engineering. Herein, we report an above-room-temperature ferroelectric discrete molecular complex [Cu(L-phe)(bpy)(H₂O)]PF₆⋅H₂O ( 1 ) which is suitable for piezoelectric energy harvesting due to its large values of piezoelectric co-efficient (d₃₃=10 pm V⁻¹) and spontaneous polarization (P_s=1.3 μC cm⁻²). Among the devices prepared with the composite films of polyvinyl alcohol (PVA) and various weight % composition of 1 , the 10 Wt % composite shows the highest output voltage of 8 V, a power density of 0.85 μW cm⁻², and output current of 5 μA, which is highest for any discrete inorganic complex reported to date.     

Electronic absorption and vibrational spectra and nonlinear optical properties of L-valinium succinate

FT-Raman and FTIR techniques have been applied to investigate the potential nonlinear optical material l-valinium succinate. A detailed interpretation of the vibrational spectra was carried out with the aid of potential energy distribution analysis. Density functional theory is applied to explore the nonlinear optical properties of the molecule. Good consistency is found between the calculated results and the experimental data for IR and Raman spectra. The natural bond orbital analysis confirms the occurrence of strong intramolecular N-H?O hydrogen bonding.     

Enantioselective Total Synthesis of Andrographolide and 14-Hydroxy-Colladonin: Carbonyl Reductive Coupling and trans-Decalin Formation by Hydrogen Transfer

An enantioselective total synthesis of the labdane diterpene andrographolide, the bitter principle of the herb Andrographis paniculata (known as “King of Bitters”), was accomplished in 14 steps (LLS). Key transformations include iridium-catalyzed carbonyl reductive coupling to form the quaternary C4 stereocenter, diastereoselective alkene reduction to establish the trans-decalin ring, and carbonylative lactonization to install the α-alkylidene-β-hydroxy-γ-butyrolactone.     

Novel electric field effects on Landau levels in graphene

A new effect in graphene in the presence of crossed uniform electric and magnetic fields is predicted. Landau levels are shown to be modified in an unexpected fashion by the electric field, leading to a collapse of the spectrum, when the value of electric to magnetic field ratio exceeds a certain critical value. Our theoretical results, strikingly different from the standard 2D electron gas, are explained using a "Lorentz boost," and as an "instability of a relativistic quantum field vacuum." It is a remarkable case of emergent relativistic type phenomena in nonrelativistic graphene. We also discuss few possible experimental consequence.     

Linear Chains of Magnetic Ions Stacked with Variable Distance: Ferromagnetic Ordering with a Curie Temperature above 20 K

We have studied the magnetic properties of the SURMOF‐2 series of metal–organic frameworks (MOFs). Contrary to bulk MOF‐2 crystals, where Cu²⁺ ions form paddlewheels and are antiferromagnetically coupled, in this case the Cu²⁺ ions are connected via carboxylate groups in a zipper‐like fashion. This unusual coupling of the spin ions within the resulting one‐dimensional chains is found to stabilize a low‐temperature, ferromagnetic (FM) phase. In contrast to other ordered 1D systems, no strong magnetic fields are needed to induce the ferromagnetism. The magnetic coupling constants describing the interaction between the individual metal ions have been determined in SQUID experiments. They are fully consistent with the results of ab initio DFT electronic structure calculations. The theoretical results allow the unusual magnetic behavior of this exotic, yet easy‐to‐fabricate, material to be described in a detailed fashion.