Microwave assisted synthesis of novel imidazo [2,1-b]thiazole derivative attached to quinoxalinones

3-(6-Phenylimidazo[2,1-b]thiazol-5-yl)quinoxalin-2(1H)-ones (qunoxalinone) (6a-q) have been synthesized by the reaction of ethyl 2-oxo-2-(6-phenylimidazo[2,1-b]thiazol-5-yl)acetates (4a-e) with suitably substituted o-phenylenediamines (5a-f) under microwave heating. The ethyl 2-oxo-2-(6-phenylimidazo[2,1-b]thiazol-5-yl)acetates (4a-e) were prepared by the reaction of 6-phenylimidazo[2,1-b]thiazoles (3a-e) with ethyl chlorooxoacetate in refluxing 1,4-dioxane whereas the thiazoles (3a-e) were synthesized by the reaction of 2-bromo-1-phenylethanones (2a-e) with thiazol-2-amine in refluxing acetone.     

An FIO calculus for marine seismic imaging, II: Sobolev estimates

We establish sharp L ²-Sobolev estimates for classes of pseudodifferential operators with singular symbols [Guillemin and Uhlmann (Duke Math J 48:251–267, 1981), Melrose and Uhlmann (Commun Pure Appl Math 32:483–519, 1979)] whose non-pseudodifferential (Fourier integral operator) parts exhibit two-sided fold singularities. The operators considered include both singular integral operators along curves in \mathbb R²{\mathbb R^2} with simple inflection points and normal operators arising in linearized seismic imaging in the presence of fold caustics [Felea (Comm PDE 30:1717–1740, 2005), Felea and Greenleaf (Comm PDE 33:45–77, 2008), Nolan (SIAM J Appl Math 61:659–672, 2000)].     

Synthesis, characterization, and electrocatalytic activity of PtPb nanoparticles prepared by two synthetic approaches

Intermetallic PtPb nanoparticles have been synthesized by two solution-phase reduction methods. In the first (PtPb-B), Pt and Pb salts were reduced by sodium borohydride in methanol at room temperature. In the second (PtPb-N), metal-organic Pt and Pb precursors were reduced by sodium naphthalide in diglyme at 135 degrees C. Both methods produced small agglomerated nanoparticles of the ordered intermetallic PtPb (mean crystal domain size <15 nm) which were characterized by pXRD, SEM, UHV-STEM, BET, EDX, and electron diffraction. The electrocatalytic activity of PtPb nanoparticles produced by both methods toward formic acid and methanol oxidation was investigated and compared to Pt and PtRu. Both PtPb-B and PtPb-N nanoparticles exhibited enhanced electrocatalytic activity compared to commercially available Pt black and PtRu nanoparticles. For formic acid oxidation, the PtPb nanoparticles exhibited considerably lower onset potentials and higher current densities than Pt or PtRu. For methanol oxidation, the PtPb nanoparticles had onset potentials slightly positive of PtRu but exhibited higher current densities at potentials about 100 mV positive of onset. The general applicability of these methods for the synthesis of nanoparticles of ordered intermetallic phases is discussed.     

Rapid self-assembly of core-shell organosilicon microcapsules within a microfluidic device

The preparation of hierarchically structured organosilicon microcapsules from commercially available starting materials is described. Using a microfluidic device, an emulsion of dichlorodiphenylsilane is formed in a continuous phase of aqueous glycerol. The silane droplets undergo hydrolysis, condensation, and crystallization within minutes to form self-assembled, core-shell microcapsules. The microparticles have been characterized with light and electron microscopy, nuclear magnetic resonance spectroscopy (NMR), diffusion-ordered NMR spectroscopy (DOSY), Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and powder X-ray diffraction (XRD). The characterization data show that the microcapsule walls consist of amorphous, oligomeric poly(diphenylsiloxane) surrounded by a spiny layer of crystalline diphenylsilanediol. Glycerol is occluded within the wall material but is not covalently bound to the silicon components. Glycerol is a crucial element for producing low-dispersity microcapsules with well-ordered surface spines, as the use of methyl cellulose as viscomodifier yields amorphous surfaces.     

Separation and determination of some metal ions on new chelating resins containing N, N donor sets

Two new stable chelating resins have been synthesized incorporating the imidazolylazobenzene and 1,4-bis(imidazolylazo)benzene as functional group into Merrifield polymer through CN covalent bond and characterized by elemental analyses, IR and thermal study. A comparison of sorption capacity of newly formed resins towards the cations Ag(I), Cu(II), Zn(II), Cd(II), Hg(II) and Pb(II) as a function of pH has been studied. Kinetic studies show the time for the completeness of metal ion saturation with the resin phase. Cd(II) in trace quantities has been successfully separated and determined in different biological samples and Zn(II) in medicinal samples. It is also found that Cd(II) can be removed from water at usual pH of natural water. Both the resins can be employed for water purification as the resins reveal sorption ability towards toxic metal ions and exhibit no affinity to alkali or alkaline earth metal ions.     

1-(2′-Pyridylazo)-2-naphtholate (PAN) complexes of rhodium(III): Synthesis,structure and spectral studies

The ligating properties 1-(2′-pyridylazo)-2-naphthol (HPAN) toward Rh(III) have been examined. The reaction of RhCl₃·3H₂O with HPAN in presence of excess PPh₃ afforded trans-[Rh(PAN)Cl(PPh₃)₂]PF₆ (3PF₆). Intermediate cis-[Rh(PAN)Cl₂(PPh₃)] (4) has also been isolated. Solid state structures were authenticated by X-ray analyses revealing that monoanionic PAN is coordinated to rhodium in meridional fashion. Both the compounds were spectroscopically characterized in both solution and solid states, which include IR, NMR (¹H and ³¹P), and optical spectra. The diamagnetic complexes show multiple CT transitions in the visible region. Low-energy transitions (λ ≈ 550–650 nm) occurred in the absorption spectra are predominantly ligand centered in nature. The rhodium(III)–PAN compounds are red emissive (λ_em ≈ 650 nm) at room temperature and the nature of the emission level is probably an ILCT level. Complexes are electro-active in acetonitrile and display irreversible oxidative and reductive waves and these responses are ascribed to be PAN ligand centered in character.     

Chemodosimetric Mechanistic Insight through Trapping Intermediate for Selective Detection of Picric Acid in Aqueous Medium by a Dinuclear CdII Complex

A fluorescent dinuclear cadmium(II) based discrete metal complex of composition [Cd^II₂L(μ-Cl)Cl₂]( 1 ) is used {HL=2,6-bis[2-(methylamino)ethyliminomethyl]-4-Ethylphenol} for the specific recognition of 2,4,6-trinitrophenol (picric acid; PA) via fluorescence quenching phenomenon among various nitroaromatic compounds through a chemodosimetric approach. It has been established that 1 is a chemodosimeter in pure water. We have successfully been able to isolate three compounds: chemodosimeter 1 ; an intermediate complex 2 of composition [Cd^II(LH₂)Cl₂](Picrate) and final association complex 3 of composition [NH₃(CH₂CH₂)NH₂CH₃](Picrate)₂. Compounds have been characterised by CHN elemental analyses, single crystal X-ray crystallography, PXRD, NMR and FTIR. Selective interaction of 1 with PA was evaluated by fluorescence, UV-Vis and life time measurements. Fluorescence quenching of 1 occurs definitely due to the formation of compound 3 via intermediate 2 involving partial decomplexation, hydrolysis and proton transfer phenomena in solution during the course of sensing. The quenching constant (K_sv), association constant (K_a) and detection limit (LOD) of the complex 1 for picric acid are ∼1.55×10⁵ M⁻¹, ∼1.8×10¹⁰ M⁻² and ∼0.47 μM (0.108 ppm), respectively. Mechanism of sensing is proposed and the very rare case of isolation and characterization of intermediate in picric acid sensing is discussed.