One‐Pot Green Synthesis of Thiazolo[3,2‐a]pyridine Derivatives via Tandem Cyclization in Aqueous Media

Facile, three‐component domino reactions of readily available thioglycolic acid/ethyl thioglycolate, aromatic aldehydes, and malononitrile/ethyl cyanoacetate in aqueous potassium carbonate at room temperature afforded thiazolo[3,2‐a]pyridine derivatives chemoselectively in good to excellent yield. All the formed 4H‐chromenes were characterized by spectral and X‐ray methods.     

Effect of terminal N-substitution in 2-oxo-1,2-dihydroquinoline-3-carbaldehyde thiosemicarbazones on the mode of coordination, structure, interaction with protein, radical scavenging and cytotoxic activity of copper(II) complexes

Four 2-oxo-1,2-dihydroquinoline-3-carbaldehyde N-substituted thiosemicarbazone ligands (H(2)-OQtsc-R, where R = H, Me, Et or Ph) and their corresponding new copper(II) complexes [CuCl(2)(H(2)-OQtsc-H)]·2H(2)O (1), [CuCl(2)(H(2)-OQtsc-Me)]·2H(2)O (2), [CuCl(2)(H(2)-OQtsc-Et)(CH(3)OH)]Cl (3) and [CuCl(H-OQtsc-Ph)]·CH(3)OH (4) have been synthesized in order to correlate the effect of terminal N-substitution on coordination behaviour, structure and biological activity. Single crystal X-ray diffraction studies revealed that the complexes 1, 2 and 3 have square pyramidal geometry around the central metal ion. In the complexes 1 and 2, the copper ion is coordinated by the ligand with ONS donor atoms, one chloride ion in apical position and the other chloride in the basal plane. Complex 3 consists of [CuCl(2)(H(2)-OQtsc-Et)(CH(3)OH)](+) cation and a chloride as counter ion. The copper ion is coordinated by the ligand with ONS donor atoms and by one chloride ion in the basal plane. One methanol molecule is bonded through its neutral oxygen in the apical position. Complex 4 is square planar with the ligand coordinating through uni-negative tridentate ONS(-) and by one chloride ion in the basal plane. The binding of complexes with lysozyme protein was carried out by fluorescence spectroscopy. Investigations of antioxidation properties showed that all the copper(II) complexes have strong radical scavenging properties. The cytotoxicity of the complexes 3 and 4 against NIH 3T3 and HeLa cell lines showed that synergy between the metal and ligands results in a significant enhancement in the cell death with IC(50) of ~10-40 μM. A size dependence of substitution at terminal N in the thiosemicarbazones on the biological activities of the complexes has been observed.     

Structures and Dynamics of Secondary and Tertiary Alkylphosphine Oxides Adsorbed on Silica

The three secondary phosphine oxides [CH₂=CH(CH₂)₄]₂HPO ( 1 ), [CH₂=CH(CH₂)₅]₂HPO ( 2 ), and [CH₂=CH(CH₂)₆]₂HPO ( 3 ), and two diphosphine dioxides, {[CH₂=CH(CH₂)₆]₂PO(CH₂)₇}₂ ( 4 ) and {[CH₂=CH(CH₂)₆]₂PO(CH₂)₄}₂ ( 5 ), incorporating long methylene chains, are described. The single crystal X‐ray structures of 1 , 2 , and 5 have been determined. The phosphine oxides 3 , 4 , and 5 have been adsorbed on silica in submonolayer quantities to give 3 a – 5 a . The ¹H, ¹³C, and ³¹P solid‐state NMR spectra of polycrystalline 3 – 5 have been analyzed and compared with those of 3 a – 5 a . The changes of the solid‐state NMR characteristics upon adsorption and the surface mobilities of the phosphine oxides are discussed.     

Preparation of chitosan–polyethylene glycol coated cotton membranes for wound dressings: preparation and characterization

Cotton fabric was coated with chitosan (CS) and polyethylene glycol (PEG) followed by freeze‐drying. The influence of PEG on the physical characteristics and the surface morphology was investigated. The scanning electron microscopy of the coated fabric revealed a porous structure. The porosity of the material was 54–70% and the pore size was in the range of 75–120µm. The increase in the PEG content in the blend composition led to an enhanced destabilization of pores, leading to an increase in the pore size with elongated morphology. There seems to be phase separation between the two components which is an important factor for the observed behavior of the porous structure. The Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC) showed that the CS and PEG have limited interaction. DSC suggested that addition of PEG to CS does not interfere with the crystallization behavior due to limited interaction with CS. The thermogravimetric analysis (TGA) showed that the membranes are thermally stable and PEG enhances the thermal stability of the CS coated membranes. The air and water permeability of the membranes tended to decrease with the increase in the PEG content. Copyright © 2008 John Wiley & Sons, Ltd.     

Oxo-, hydroxo-, and peroxo-bridged Fe(III) phosphonate cages

A series of five Fe(III) phosphonate clusters with four different topologies is reported. The choice of coligand carboxylate plays an important role in directing the structure of the molecule. [Fe9(O)4(O2CCMe3)13(C10P)3] (1) and [Fe9(O)2(OH)(CO2Ph)10(C10P)6(H2O)2](CH3CN)7 (2; camphyl phosphonic acid, C10H17PO3H2 = C10PH2) represent two unprecedented nonanuclear Fe(III) cages having Fe9O4 and Fe9(O)2(OH) core structures, respectively. Whereas [Fe6O2(O)2(O2CCMe3)8(C10P)2 (H2O)2](CH3CN)4 (3) is a peroxo-bridged hexameric compound with an Fe6(O)2(O2) core. [Fe4(O)(O2CCMe3)4(C10P)3(Py)4](CH3CN)3 (4) and [Fe4(O)(O2CPh)4(C10P)3(Py)4](Py)3(CH3CN)2 (5; Py = pyridine) represents two tetranuclear clusters with the same Fe4O core structure.     

Syntheses,homeomorphic and configurational isomerizations,and structures of macrocyclic aliphatic dibridgehead diphosphines; molecules that turn themselves inside out

The diphosphine complexes cis- or trans- PtCl₂(P((CH₂)_n)₃P ) (n = b/12, c/14, d/16, e/18) are demetalated by MC X nucleophiles to give the title compounds (P((CH₂)_n)₃)P (3b–e, 91–71%). These “empty cages” react with PdCl₂ or PtCl₂ sources to afford trans- MCl₂(P((CH₂)_n)₃P ). Low temperature ³¹P NMR spectra of 3b and c show two rapidly equilibrating species (3b, 86 : 14; 3c, 97 : 3), assigned based upon computational data to in,in (major) and out,out isomers. These interconvert by homeomorphic isomerizations, akin to turning articles of clothing inside out (3b/c: ΔH^‡ 7.3/8.2 kcal mol⁻¹, ΔS^‡ −19.4/−11.8 eu, minor to major). At 150 °C, 3b, c, e epimerize to (60–51) : (40–49) mixtures of (in,in/out,out) : in,out isomers, which are separated via the bis(borane) adducts 3b, c, e·2BH₃. The configurational stabilities of in,out-3b, c, e preclude phosphorus inversion in the interconversion of in,in and out,out isomers. Low temperature ³¹P NMR spectra of in,out-3b, c reveal degenerate in,out/out,in homeomorphic isomerizations (ΔG^‡_Tc 12.1, 8.5 kcal mol⁻¹). When (in,in/out,out)-3b, c, e are crystallized, out,out isomers are obtained, despite the preference for in,in isomers in solution. The lattice structures are analyzed, and the D₃ symmetry of out,out-3c enables a particularly favorable packing motif. Similarly, (in,in/out,out)-3c, e·2BH₃ crystallize in out,out conformations, the former with a cycloalkane solvent guest inside.

It’s not a magic trick. Molecules can turn themselves inside out, just like articles of clothing or other familiar household objects. This behavior is demonstrated for the title compounds through a combination of synthesis, rate, and NMR studies.     

Structure and Magnetization Dynamics of Dy−Fe and Dy−Ru Bonded Complexes

We present an investigation of isostructural complexes that feature unsupported direct bonds between a formally trivalent lanthanide ion (Dy³⁺) and either a first‐row (Fe) or a second‐row (Ru) transition metal (TM) ion. The sterically rigid, yet not too bulky ligand PyCp₂^2? (PyCp₂^2?=[2,6‐(CH₂C₅H₃)₂C₅H₃N]^2?) facilitates the isolation and characterization of PyCp₂Dy?FeCp(CO)₂ ( 1 ; d(Dy–Fe)=2.884(2) Å) and PyCp₂Dy?RuCp(CO)₂ ( 2 ; d(Dy–Ru)=2.9508(5) Å). Computational and spectroscopic studies suggest strong TM→Dy bonding interactions. Both complexes exhibit field‐induced slow magnetic relaxation with effectively identical energy barriers to magnetization reversal. However, in going from Dy?Fe to Dy?Ru bonding, we observed faster magnetic relaxation at a given temperature and larger direct and Raman coefficients, which could be due to differences in the bonding and/or spin–phonon coupling contributions to magnetic relaxation.     

Synthesis of benzosuberone-tethered spirooxindoles: 1-3-dipolar cycloaddition of azomethine ylides and arylidene benzosuberones

Molecular Diversity - Expedient synthesis of benzosuberone-tethered spirooxindoles was accomplished by a three-component 1,3-dipolar cycloaddition reaction between azomethine ylide (generated in...     

Nanocomposite interface coupled with thickness optimization promoting water dissociation in heterogeneous bipolar membrane

Bipolar membranes (BPMs) are multilayered composite film containing an interface layer sandwiched between cation exchange layer (CEL) and anion exchange layer (AEL), and are capable of dissociating water molecules under reverse bias potential. Woven fabric supported heterogeneous bipolar membranes (HBMs) were synthesized adopting layer-by-layer solvent casting technique. Nanocomposite layer based on sulfonated polyether ether ketone (SPEEK) and GO (graphene oxide) were applied at the interface of CEL/AEL made of cation/anion exchange resins and poly (vinyl chloride) as binder to advance water dissociation in HBMs. Thickness of monopolar layers were initially optimized without any interfacial layer. Introduction of SPEEK interface substantially lowered onset water dissociation potential, U_diss (~1.87 V) relative to the HBM without interface (~3.27 V), which got further reduced (~1.80 V) by nanocomposite (GO + SPEEK) interface. U_diss recorded with SPEEK + GO as interface was much lower than some of the recently reported homogeneous BPM. The NaOH production from NaCl (1.0 mol?L^?1) solution in a bipolar membrane electrodialysis set up containing synthesized HBM with nanocomposite interface (SPEEK + GO) was double than that of NaOH concentration obtained with HBM having no interface, where the current density was fixed at 50.0 mA·cm^?2. Careful optimization of monopolar/interface layer thickness and composition of nanocomposite interface results in developing cost effective HBMs facilitating water dissociation at lower potential.