A facile,catalyst-free synthesis of new polycyclic pyrrolo[1,2-b]pyrazolone derivatives

A convenient and efficient procedure has been developed for the synthesis of a new ring system, pyrrolo[1,2-b]pyrazolone, via two-component coupling reaction followed by base mediated intramolecular cyclization. Single-pot synthesis replacing the two step process has also been successfully carried out. A series of polycyclic pyrrolo[1,2-b]pyrazolone derivatives have been obtained by employing the procedure along with some fused pyrrol-1-ylamine system. The products were formed very rapidly in catalyst free condition in a good yield (up to 75%) and also it had tolerance to a wide scope of substrates.     

Importance of steric effect and evaluation of quantitative structure reactivity relationship (QSRR) in the quaternization reaction of benzothiazoles and phenacyl bromide

The kinetics of reaction of substituted 2-aminobenzothiazoles and phenacyl bromide have been followed conductometrically and in some cases, argentometrically. Both the methods produced almost the same rate constants. Substituents at position 5 of the benzothiazole nucleus behave like para substituents of the benzene ring. A correlation with Hammett σ_p substituent constants has been obtained with a rho value of ?1.04. The rate data of quaternization reaction of 4, 5, and 6 substituted 2-aminobenzothiazoles with phenacyl bromide have been correlated with F_k, R_k, and V_w values by multiple regression analysis with the equation suggested by Williams and Norrington and modified by us. The values are found to correlate well with the equation, log k = ?4.4979 ? 0.4815f_jF_k + 0.5933r_jR_k ? 0.0277V_w.     

Synthesis,characterization, thermal properties,and antimicrobial activity of 4‐chloro‐3‐methyl phenyl methacrylate/8‐quinolinyl methacrylate copolymers

4‐Chloro‐3‐methyl phenyl methacrylate (CMPM) and 8‐quinolinyl methacrylate (8‐QMA) were synthesized through the reaction of 4‐chloro‐3‐methyl phenol and 8‐hydroxy quinoline, respectively, with methacryloyl chloride. The homopolymers and copolymers were prepared by free‐radical polymerization with azobisisobutyronitrile as the initiator at 70 °C. Copolymers of CMPM and 8‐QMA of different compositions were prepared. The monomers were characterized with IR spectroscopy and ¹H NMR techniques. The copolymers were characterized with IR spectroscopy. UV spectroscopy was used to obtain the compositions of the copolymers. The monomer reactivity ratios were calculated with the Fineman–Ross method. The molecular weights and polydispersity values of the copolymers were determined with gel permeation chromatography. The thermal stability of the polymers was evaluated with thermogravimetric analysis under a nitrogen atmosphere. The homopolymers and copolymers were tested for their antimicrobial activity againstbacteria, fungi, and yeast. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 157–167, 2005     

Chemical Approach Towards Broadband Spintronics on Nanoscale Pyrene Films

The injection of pure spin current into the non-magnetic layer plays a crucial role in transmitting, processing, and storing data information in the realm of spintronics. To understand broadband molecular spintronics, pyrene oligomer film (≈20 nm thickness) was prepared using an electrochemical method forming indium tin oxide (ITO) electrode/pyrene covalent interfaces. Permalloy (Ni₈₀Fe₂₀) films with different nanoscale thicknesses were used as top contact over ITO/pyrene layers to estimate the spin pumping efficiency across the interfaces using broadband ferromagnetic resonance spectra. The spintronic devices are composed of permalloy/pyrene/ITO orthogonal configuration, showing remarkable spin pumping from permalloy to pyrene film. The large spin pumping is evident from the linewidth broadening of 5.4 mT at 9 GHz, which is direct proof of spin angular momentum transfer across the interface. A striking observation is made with the high spin-mixing conductance of ≈1.02×10¹⁸ m⁻², a value comparable to the conventional heavy metals. Large spin angular moment transfer was observed at the permalloy-pyrene interfaces, especially at the lower thickness of permalloy, indicating a strong spinterface effect. Pure spin current injection from ferromagnetic into electrochemically grown pyrene films ensures efficient broadband spin transport, which opens a new area in molecular broadband spintronics.     

Discrepancy between subcritical and fast rupture roughness: a cumulant analysis

Rough crack fronts in a sheet of paper, obtained during a creep experiment, do not follow true scaling laws. Local roughness exponents are estimated using the first order cumulant, a quantity recently introduced in the turbulence literature [J. Delour, J. F. Muzy, and A. Arneodo, Eur. Phys. J. B 23, 243 (2001)10.1007/s100510170074]. Using a large data set (102 fronts), we find a significant difference in local roughness between the slow (subcritical) and the fast growth regime.     

Selectivity in Garratt-Braverman cyclization: an experimental and computational study

Bispropargyl sulfones equipped with aromatic rings of dissimilar nature were synthesized. Under basic conditions, these sulfones isomerized to the bisallenic sulfones, creating a competitive scenario between two alternate Garratt-Braverman (GB) cyclization pathways. The observed product distribution ruled out the involvement of any ionic intermediate and supported the diradical mechanism with greater involvement of the electron-rich aromatic ring via the more nucleophilic radical. DFT-based calculations supported the diradical mechanism along with the observed selectivity.     

Fine-scale functional connectivity in somatosensory cortex revealed by high-resolution fMRI

High-resolution functional magnetic resonance imaging (fMRI) at high field (9.4 T) has been used to measure functional connectivity between subregions within the primary somatosensory (SI) cortex of the squirrel monkey brain. The hand-face region within the SI cortex of the squirrel monkey has been previously well mapped with functional imaging and electrophysiological and anatomical methods, and the orderly topographic map of the hand region is characterized by a lateral to medial representation of individual digits in four subregions of areas 3a, 3b, 1 and 2. With submillimeter resolution, we are able to detect not only the separate islands of activation corresponding to vibrotactile stimulations of single digits but also, in subsequent acquisitions, the degree of correlation between voxels within the SI cortex in the resting state. The results suggest that connectivity patterns are very similar to stimulus-driven distributions of activity and that connectivity varies on the scale of millimeters within the same primary region. Connectivity strength is not a reflection of global larger-scale changes in blood flow and is not directly dependent on distance between regions. Preliminary electrophysiological recordings agree well with the fMRI data. In human studies at 7 T, high-resolution fMRI may also be used to identify the same subregions and assess responses to sensory as well as painful stimuli, and to measure connectivity dynamically before and after such stimulations.     

Structure and gas sorption behavior of a new three dimensional porous magnesium formate

A new three-dimensional magnesium formate polymorph, namely, γ-[Mg(3)(O(2)CH)(6)] has been synthesized via in situ formate anion generation method. γ-Mg-formate crystallizes in space group Pbcn, and structural determination by X-ray single crystal diffraction reveals a three-dimensional network of Mg(2+) linked by formate anions. All formate anions possess similar binding mode to the metal center with one oxygen of a particular formate anion binds to one metal center (μ(1) oxygen) and other oxygen binds to two metal centers (μ(2) oxygen). N(2) adsorption studies indicate that the framework displays permanent porosity. The specific surface area of γ-Mg-formate (BET, 120 m(2) gm(-1)) is lower than the α- polymorph (BET, 150 m(2) gm(-1)). However, the initial hydrogen uptake of γ-Mg-formate reached almost 1.0 wt % when the adsorbate pressure approached 760 Torr at 77 K. This is higher than the hydrogen uptake of α-Mg-formate (0.6 wt %). γ-Mg-formate, shows a moderate affinity and capacity for CO(2) (3.4 ? kinetic diameter) at 298 K. The CO(2) uptake at 760 Torr is 2.01 mmol gm(-1) (47.0 cc gm(-1)). Although this CO(2) uptake is somewhat modest, it compares well with the CO(2) uptake of several Mg-MOFs and ZIFs reported in the literature.     

Ultrafast Raman loss spectroscopy (URLS): instrumentation and principle

In this paper, we report on the concept and the design principle of ultrafast Raman loss spectroscopy (URLS) as a structure‐elucidating tool. URLS is an analogue of stimulated Raman scattering (SRS) but more sensitive than SRS with better signal‐to‐noise ratio. It involves the interaction of two laser sources, namely, a picosecond (ps) Raman pump pulse and a white‐light (WL) continuum, with a sample, leading to the generation of loss signals on the higher energy (blue) side with respect to the wavelength of the Raman pump unlike the gain signal observed on the lower energy (red) side in SRS. These loss signals are at least 1.5 times more intense than the SRS signals. An experimental study providing an insight into the origin of this extra intensity in URLS as compared to SRS is reported. Furthermore, the very requirement of the experimental protocol for the signal detection to be on the higher energy side by design eliminates the interference from fluorescence, which appears on the red side. Unlike CARS, URLS signals are not precluded by the non‐resonant background and, being a self‐phase‐matched process, URLS is experimentally easier. Copyright © 2011 John Wiley & Sons, Ltd.