Appearance of an inhomogeneous superconducting state in La0.67Sr0.33MnO3-YBa2Cu3O7-La0.67Sr0.33MnO3 trilayers

An experimental study of proximity effect in La_0.67Sr_0.33MnO₃-YBa₂CU₃O₇-La_0.67Sr_0.33MnO₃ trilayers is reported. Transport measurements on these samples show clear oscillations in critical current (I _c) as the thickness of La_0.67Sr_0.33MnO₃ layers (d _F) is scanned from ∼50 ? to ∼ 1100 ?. In the light of existing theories of ferromagnet-superconductor (FM-SC) heterostructures, this observation suggests a long range proximity effect in the manganite, modulated by its weak exchange energy (∼2 meV). The observed modulation of the magnetic coupling between the ferromagnetic LSMO layers as a function of d _F, also suggests an oscillatory behavior of the SC order parameter near the FM-SC interface.      

Substituent effects in the reaction between benzaldehydes and polyacrylonitrile radicals

The effects of substituents on the reaction of benzaldehydes with polyacrylonitrile radicals have been studied in terms of the multiparameter equations based on Swain and Lupton's Field and Resonance (F and R) components with the unique positional weighting factors f and r developed by Williams and Norrington. From the nature of the reaction constants, a polar transition state has been postulated.     

Synthesis, structure, magnetism and nuclease activity of tetranuclear copper(II) phosphonates containing ancillary 2,2'-bipyridine or 1,10-phenanthroline ligands

The reaction of cyclohexylphosphonic acid (C(6)H(11)PO(3)H(2)), anhydrous CuCl(2) and 2,2'-bipyridine (bpy) in the presence of triethylamine followed by a metathesis reaction with KNO(3) afforded [Cu(4)(mu-Cl)(2)(mu(3)-C(6)H(11)PO(3))(2)(bpy)(4)](NO(3))(2) (1). In an analogous reaction involving Cu(OAc)(2).H(2)O, the complex [Cu(4)(mu-CH(3)COO)(2)(mu(3)-C(6)H(11)PO(3))(2)(2,2'-bpy)(4)](CH(3)COO)(2) (2) has been isolated. The three-component reaction involving Cu(NO(3))(2).3H(2)O, cyclohexylphosphonic acid and 2,2'-bipyridine in the presence of triethylamine afforded the tetranuclear assembly [Cu(4)(mu-OH)(mu(3)-C(6)H(11)PO(3))(2)(2,2'-bpy)(4) (H(2)O)(2)](NO(3))(3) (3). Replacing 2,2'-bipyridine with 1,10-phenanthroline (phen) in the above reaction resulted in [Cu(4)(mu-OH)(mu(3)-C(6)H(11)PO(3))(2)(phen)(4)(H(2)O)(2)](NO(3))(3) (4). In all the copper(II) phosphonates (1-4) the two phosphonate ions bridge the four copper(II) ions in a capping coordination action. Each phosphonate ion bridges four copper(II) ions in a mu(4), eta(3) coordination mode or 4.211 of the Harris notation. Variable-temperature magnetic studies on reveal that all four complexes exhibit moderately strong intramolecular antiferromagnetic coupling. The DNA cleavage activity of complexes 1-4 is also described. Compounds 1 and 3 were able to completely convert the supercoiled pBR322 DNA form I to nick form II without any co-oxidant. In contrast, 50% conversion occurred with and 40% with 4. In the presence of magnesium monoperoxyphthalate all four compounds achieved rapid conversion of form I to form II.     

Regioselective synthesis of 1-hydroxycarbazoles via anionic [4+2] cycloaddition of furoindolones: a short synthesis of murrayafoline-A

Suitably N-protected furoindolones react regioselectively with a variety of Michael acceptors in the presence of LDA to give 1-hydroxycarbazoles in a single-pot process and in good yields. The methodology has been applied to the synthesis of murrayafoline-A.     

Synthesis and antitubercular activity evaluation of 4-furano-coumarins and 3-furano-chromones

The synthesis of novel 4-furano-coumarins and 3-furano-chromones has been achieved using silver-mediated oxidative C–H/C–H functionalization of 4-ethynylcoumarin/3-ethynylchromone with ethyl acetoacetate in 80%–90% and 82%–90% yields, respectively. The structure of the synthesized compounds was established on the basis of their spectral data analysis and the structure of one of the 4-furano-coumarins has been further confirmed on the basis of its X-ray crystallographic study. All eight synthesized 4-furano-coumarins and 3-furano-chromones exhibited moderate antitubercular activity against sensitive reference strain H37Rv of Mycobacterium tuberculosis.     

Optimized DNA hybridization detection on nanocolloidal particles by dielectrophoresis

Oligonucleotides of varying surface coverage are functionalized onto the surface of 100 nm silica particles and the corresponding hybridization reaction with target ssDNA is studied using dielectrophoresis (DEP). The measured DEP cross‐over frequency (cof) is found to be sensitive to the oligonucleotide surface conformation. Zeta potential and particle size measurements suggest that at low oligo surface concentrations, non‐specific binding of oligo to the particle surface prevents efficient hybridization. At high surface coverage, steric hindrance due to the fully stretched, tightly packed oligo conformation prevents diffusion of DNA molecules to the particle surface. The optimum surface coverage exists at intermediate coverage where the particle is found to be the least electrically conductive, and hence exhibits the lowest measured cof. A simple DEP cof measurement hence allows one to determine the optimal oligo surface coverage for increased hybridization efficiency and detection sensitivity.     

6-Membered pseudocyclic IBX acids: syntheses, X-ray structural characterizations, and oxidation reactivities in common organic solvents

We designed and synthesized λ(5)-cyclic periodinanes 1 and 2, which are homologous to IBX (1-hydroxy-1-oxo-1H-1λ(5)-benzo[d][1,2]iodoxol-3-one) by one carbon, to thwart close packing of molecules in the crystal lattice to permit solubility in common organic solvents and to facilitate oxidations with enhanced reactivity. The X-ray crystal structures revealed that both 1 and 2 exist in the solid state as pseudocyclic (PC) acids, i.e., 1PC and 2PC, and that the molecules in the lattice are less weakly associated as compared to those in the parent IBX due to the twisting introduced via the sp(3) benzylic carbon. Both 1PC and 2PC are found to dissolve in palpable amounts in DCM and acetonitrile to allow oxidation of a variety of alcohols and sulfides to carbonyl compounds and sulfoxides in a facile manner. The subtle differences in the sterics due to methyl and ethyl substituents in 1PC and 2PC are found to manifest in contrasting reactivities in that the oxidations of alcohols occur faster with 2PC, while those of sulfides to sulfoxides occur more rapidly with 1PC.     

Rational assembly of soluble copper(II) phosphonates: synthesis, structure and magnetism of molecular tetranuclear copper(II) phosphonates

The reactions of the dinuclear copper complexes [Cu(2)(L)(OAc)] [H(3)L = N,N'-(2-hydroxypropane-1,3-diyl)bis(salicylaldimine) or [Cu(2)(L')(OAc)] (H(3)L' = N,N'-(2-hydroxypropane-1,3-diyl)bis(4,5-dimethylsalicylaldimine)] with various phosphonic acids, RPO(3)H(2) (R = t-Bu, Ph, c-C(5)H(9), c-C(6)H(11) or 2,4,6-i-Pr(3)-C(6)H(2)), leads to the replacement of the acetate bridge affording tetranuclear copper(II) phosphonates, [Cu(4)(L)(2)(t-BuPO(3))](CH(3)OH)(2)(C(6)H(6)) (1), [Cu(4)(L)(2)(PhPO(3))(H(2)O)(2)(NMe(2)CHO)](H(2)O)(2) (2), [Cu(4)(L')(2)(C(5)H(9)PO(3))](CH(3)OH)(2) (3), [Cu(4)(L')(2)(C(6)H(11)PO(3)](MeOH)(4)(H(2)O)(2) (4) and [Cu(4)(L')(2)(C(30)H(46)P(2)O(5))](PhCH(3)) (5). The molecular structures of 1-4 reveal that a [RPO(3)](2-) ligand is involved in holding the four copper atoms together by a 4.211 coordination mode. In 5, an in situ formed [(RPO(2))(2)O](4-) ligand bridges two pairs of the dinuclear subunits. Magnetic studies on these complexes reveal that the phosphonate ligand is an effective conduit for magnetic interaction among the four copper centers present; a predominantly antiferromagnetic interaction is observed at low temperatures.     

Nanomaterials for targeted detection and photothermal killing of bacteria

Despite the modern treatment processes, contamination of food, water and medical equipment by pathogenic bacteria is very common in this world. Since the last two decades, one of the most important and complex problems our society has been facing is that several human pathogens became resistant to most of the clinically approved antibiotics. Recent advancement in nanoscience and nanotechnology has expanded our ability to design and construct nanomaterials with targeting, therapeutic, and diagnostic functions. These multifunctional materials have attracted our attention to be used as the promising tool for selective bacteria sensing and therapy without the current drugs. This tutorial review provides the basic concepts and critical properties of the different nanostructures that are useful for the pathogen detection and photothermal applications. In addition, bio-conjugated nanomaterial based strategies have been discussed with the aim to provide readers an overview of exciting opportunities and challenges in this field.     

Highly enantioselective mukaiyama aldol reactions catalyzed by a chiral oxazaborolidinium ion: total synthesis of (-)-inthomycin C

A cationic oxazaborolidinium-catalyzed asymmetric Mukaiyama aldol reaction of (1-methoxy-2-methyl-propenyloxy)-trimethylsilane with various aldehydes including α,β-disubstituted acroleins has been developed in high yields and enantioselectivities. The synthetic utility of this methodology was demonstrated in the first short synthesis of naturally occurring inthomycin C in high enantiopurity.