Strong Equatorial Crystal Field Enhances the Axial Anisotropy and Energy Barrier for Spin Reversal Process in Yb2 Single Molecule Magnets

The importance of equatorial crystal fields on magnetic anisotropy of ytterbium single molecule magnets (SMMs) is observed for the first time. Herein, we report three similar dinuclear ytterbium complexes with the formula [Yb₂(3-OMe-L)₂(DMF)₂(NO₃)₂]⋅DMF ( 1 ), [Yb₂(3-H-L)₂(DMF)₂(NO₃)₂]⋅DMF⋅H₂O ( 2 ), and [Yb₂(3-NO₃-L)₂(DMF)₂(NO₃)₂] ( 3 ), [where 3-X-H₂L=N′-(2-hydroxy-3-X-benzylidene)picolinohydrazide, X=OMe ( 1 ), H ( 2 ) NO₂ ( 3 )]. Detailed magnetic measurements reveal the presence of weak antiferromagnetic interactions between the Yb centers and a field-induced slow relaxation of magnetization in all complexes. A higher energy barrier for spin reversal was observed for complex 1 (U_eff=50 K) and it decreases in the order of 2 (47 K) to 3 (40 K). Notably, complex 1 shows a remarkable energy barrier within the frequency range of 1–850 Hz reported for Yb-based SMMs. Further, ab initio calculations show a higher axial anisotropy and lower quantum tunneling of magnetization (QTM) in the ground state for 1 compared to 2 and 3 . It was also observed that the presence of a strong crystal field in the equatorial plane (when the ∡ O1−Yb−O3 bond angle is close to 90°) enhances the axial anisotropy and improves the SMM behavior in the studied complexes. Both the experimental and theoretical analysis of relaxation dynamics discloses that Raman and QTM play major role on slow relaxation process for all complexes. To provide more insight into the exchange interactions, broken-symmetry DFT calculations were performed.     

TEMPO-Mediated Selective Synthesis of Isoxazolines, 5-Hydroxy-2-isoxazolines,and Isoxazoles via Aliphatic δ-C(sp3)-H Bond Oxidation of Oximes

Selective synthesis of three different bioactive heterocycles; isoxazolines, 5-hydroxy-2-isoxazolines and isoxazoles from the same starting material using TEMPO (2,2,6,6-Tetramethylpiperidin-1-oxyl) as a radical initiator is reported. Selectivity was achieved using different oxidants with TEMPO. The reaction goes through a 1,5-HAT (hydrogen atom transfer) process resulting in products with good yields. This strategy offers a straightforward route to three different heterocycles from oximes via radical-mediated C(sp³)-H oxidation.     

Triton X-100 functionalized Cu(II) dihydrazone based complex immobilized on Fe3O4@dopa: A highly efficient catalyst for oxidation of alcohols,alkanes, and sulfides and epoxidation of alkenes

Here, we have presented a protocol for green synthesis, characterization, and catalytic application of TX100/Fe₃O₄@dopa@CuL ( FDCTX ) magnetically separable nanoparticles. Fe₃O₄@dopa@CuL ( FDC ) was synthesized using a four-step procedure: (i) synthesis of a dihydrazone derivative, (ii) reaction of the dihydrazone derivative with copper perchlorate salt to generate a copper complex of the dihydrazone derivative, (iii) immobilization of the complex onto Fe₃O₄@dopa to generate FDC , and (iv) coating of FDC with surfactant Triton X-100. The as-synthesized homogeneous complex was well characterized using UV–Vis., Fourier-transform infrared (FT-IR), electrospray ionization–mass spectrometry, and single-crystalX-ray techniques. Single-crystalX-ray analysis revealed the tetranuclear framework of the complex. The heterogeneous nanoparticles ( FDCTX ) were characterized using FT-IR, powder X-ray diffraction, scanning electron microscopy, transmission electron microscopy, energy-dispersiveX-ray spectroscopy, magnetic hysteresis, and dynamic light scattering techniques. Finally, both the homogeneous and heterogeneous catalysts were utilized for efficient oxidation of alcohols, alkanes, and sulfides and epoxidation of alkenes. A most probable mechanism for the oxidation reaction is proposed at the end of the article.     

Topology-Controlled AIEE of Iminocoumarin Luminophores

Aggregation-induced emission enhancement (AIEE) is an unusual phenomenon where luminophores show a higher photoluminescence efficiency in the aggregated and solid state. We report the design and synthesis of a series of luminophores 1 – 4 with imine functionality at 6 position of coumarin and studied their AIE propensities on self-assembly. The effect of the topology of the phenolic hydroxyl group on the emission behaviour of the luminophores has been investigated. The imines show significant solvatochromism with high emission in non-polar solvents, whereas the emission gets quenched in the polar solvent. The fluorescence in the toluene-hexane mixture arises due to the aggregation of fluorophores and falls under the category of AIEE. Not only the solution state emission of the isomeric iminocoumarin luminophores is notably varied, but also their solid-state emission found to be significantly different from each other. Moreover, the iminocoumarin 1 selectively recognizes Fe(III) over Fe(II) with a prominent color change. In situ oxidation of Fe(II) with H₂O₂ exhibits the same effect like Fe(III) and developed a chemical combinational logic gate.     

Selenium Biofortification: Roles,Mechanisms, Responses and Prospects

The trace element selenium (Se) is a crucial element for many living organisms, including soil microorganisms, plants and animals, including humans. Generally, in Nature Se is taken up in the living cells of microorganisms, plants, animals and humans in several inorganic forms such as selenate, selenite, elemental Se and selenide. These forms are converted to organic forms by biological process, mostly as the two selenoamino acids selenocysteine (SeCys) and selenomethionine (SeMet). The biological systems of plants, animals and humans can fix these amino acids into Se-containing proteins by a modest replacement of methionine with SeMet. While the form SeCys is usually present in the active site of enzymes, which is essential for catalytic activity. Within human cells, organic forms of Se are significant for the accurate functioning of the immune and reproductive systems, the thyroid and the brain, and to enzyme activity within cells. Humans ingest Se through plant and animal foods rich in the element. The concentration of Se in foodstuffs depends on the presence of available forms of Se in soils and its uptake and accumulation by plants and herbivorous animals. Therefore, improving the availability of Se to plants is, therefore, a potential pathway to overcoming human Se deficiencies. Among these prospective pathways, the Se-biofortification of plants has already been established as a pioneering approach for producing Se-enriched agricultural products. To achieve this desirable aim of Se-biofortification, molecular breeding and genetic engineering in combination with novel agronomic and edaphic management approaches should be combined. This current review summarizes the roles, responses, prospects and mechanisms of Se in human nutrition. It also elaborates how biofortification is a plausible approach to resolving Se-deficiency in humans and other animals.     

On the gate capacitance of mos structures in N-Channel inversion layers on ternary chalcopyrite semiconductors

An attempt is made to investigate the gate capacitance of MOS structures in n-channel inversion layers on ternary chalcopyrite semiconductors at low temperatures, taking n-channel inversion layers on CdGeAs₂ as examples, under both the weak and strong electric field limits, respectively. We have formulated the gate capacitance on the basis of newly derived 2D electron energy spectra for both the limits by considering the various anisotropies of the band parameters within the framework ofk·p formalism. It has been observed that, the gate capacitance increases with increasing surface electric field in an oscillatory manner and the theoretical results are in good agreement with the experimental observations as reported elsewhere. In addition, the corresponding well-known results for n-channel inversion layers on isotropic parabolic semiconductors are also obtained from the generalized expressions derived under certain limiting conditions.     

Theoretical analysis of the gate capacitance inn-channel inversion layers on ternary chalcopyrite semiconductors in the presence of a quantizing magnetic field

An attempt is made to study theoretically, the dependence of the gate capacitance inn-channel inversion larges on ternary chalcopyrite semiconductors on a quantizing magnetic field, takingn-channel inversion layers on CdGeAs₂ as an example. It is found, on the basis of a newly derived electron energy spectrum of the above class of semiconductors, that the gate capacitance exhibits spiky oscillations with changing magnetic field and the oscillatory behaviour is in qualitative agreement with the experimental observation reported in the literature for the MOS structure of Hg_1–x Cd _x Te.     

Effect of isothermal treatments on the magnetic behavior of nanocrystalline Cu–Ni–Fe alloy prepared by mechanical alloying

The present study concerns magnetic behavior of nanocrystalline Cu–Ni, Cu–Fe and Cu–Ni–Fe alloys prepared by mechanical alloying. It has been found that the magnetic properties e.g. H_c, M_r and M_s of the nanocrystalline alloys were significantly influenced by the changes in microstructural constituents, grain size and evolution of phases. Microstructural changes in the alloys have been effected by carrying out isothermal treatments on the mechanically alloyed products in the temperature range of 450–650 °C. Phase evolution in the samples after the isothermal treatments were identified and characterized by X-ray diffraction (XRD) and differential scanning calorimetric (DSC) techniques and the results were correlated with the magnetic properties of the alloys.     

Effect of magnetic quantization on the Einstein relation in Kane-type semiconductors

An attempt is made to formulate the Einstein relation for the diffusivity-mobility ratio of the carriers in degenerate semiconductors having Kane-type energy bands in the presence of a quantizing magnetic field, taking degenerate n-InAs as an example. It is found on the basis of the three-band Kane model, which is the most valid model for n-InAs, that the same ratio oscillates with changing magnetic field only under degenerate conditions and remains unaffected otherwise. The corresponding results for parabolic semiconductors are also obtained from the expressions derived.     

Development of a new fluorescence ratiometric switch for endogenous hypochlorite detection in monocytes of diabetic subjects by dye release method

Increased oxidative stress in metabolic complications like type 2 diabetes, dyslipidemia and cardiovascular disorders exerts potential health hazards in many facets. Enhanced production of reactive oxygen species (ROS) due to increased oxidative stress promotes the damage of many biologically important macromolecules. Hypochlorous acid (HOCl), a microbicidal agent is also known to be an important ROS sub-species. An enhanced generation of endogenous HOCl due to diseased condition therefore can be detrimental to health. In present work, a new quinoline-diaminomaleonitrile based probe (HQMN) has been designed for the selective detection of hypochlorite. The probe in hand shows a selective ratiometric emission change towards OCl^?. The probe behaves as a highly selective and sensitive tool for the detection of OCl^? over other analytes with a fast response time (within 100 s). Bioimaging study revealed that HQMN can detect endogenous OCl^? in human monocytes and an increase in endogenous HOCl concentration has been witnessed in diabetic condition compared to healthy control. Thus HQMN can be used as an excellent fluorescent probe for dynamic tracking of hypochorite in living biological cells especially to identify diabetic conditions.