Molecular self-assembly of cadmium-triazolate complexes via hydrogen bonding: Synthesis, structures and photoluminescent properties

Two new cadmium coordination polymers namely Cd(HAmTrz-COO)(4)(NH4+)(2)] 1; and Cd(HAmTrz)(2)I-2](n) 2; (HAmTrz-COOH = 3-amino-1,2,4-triazole-5-carboxylic acid), have been prepared based on HAmTrz-COOH as ligand. The crystal structures of 1 and 2 have been determined by single-crystal X-ray diffraction technique. In coordination-complex 1 four triazole ligands coordinate via N1 nitrogen leading to a tetrahedral geometry around cadmium ion, while in 2 the ligand prefers to coordinate to the metal in a bidentate bridging mode. The structures of both the coordination polymers can be envisaged as 3D hydrogen bonded networks. Thermogravimetric analysis shows that 2 is more stable than 1 owing to different coordination numbers of cadmium atoms. Photoluminescence properties of both the compounds have been investigated in the solid state. (C) 2011 Elsevier B.V. All rights reserved.

SEC-MALDI-TOF mass spectral characterization of a hyperbranched polyether prepared via melt transetherification

An AB(2) monomer, 1-(2-hydroxyethoxy)-3,5-bis-(methoxymethyl)-2,4,6-trimethylbenzene, was synthesized from mesitol and melt-polycondensed in the presence of an acid catalyst via a transetherification process at 145-150 degreesC to yield a soluble, moderately high molecular weight hyperbranched polyether. The degree of branching in the polymer was calculated to be 0.78 by a comparison of its NMR spectrum with that of an appropriately designed model compound. The weight-average molecular weight of the hyperbranched polymer was determined to be 64,600 (weight-average molecular weight/number-average molecular weight = 5.2) by size exclusion chromatography (SEC) in CHCl3, with polystyrene standards. The origin of the broad molecular weight distribution, which could either be intrinsic to such hyperbranched structures or be due to structural heterogeneity, was further probed by the fractionation of the samples by SEC and by the subjection of each fraction to matrix-assisted laser desorption/ionization time-of-flight mass spectral analysis. The mass spectral analysis suggested the presence of two primary types of species: one corresponding to the simple branched structure and the other to macrocyclics. Interestingly, from the relative intensities of the two peaks, it was apparent that cyclization became favorable at higher conversions in the melt transetherification process. (C) 2002 Wiley Periodicals, Inc.

Microwave ECR Plasma Assisted MOCVD of Y(2)O(3) Thin Films Using Y(tod)(3) Precursor and Their Characterization

Yttrium oxide (Y(2)O(3)) thin films were deposited by microwave electron cyclotron resonance (ECR) plasma assisted metal organic chemical vapour deposition (MOCVD) process using indigenously developed metal organic precursors Yttrium 2,7,7-trimethyl-3,5-octanedionates, commonly known as Y(tod)(3) which were synthesized by an ultrasound method. A series of thin films were deposited by varying the oxygen flow rate from 1-9 sccm, keeping all other parameters constant. The deposited coatings were characterized by X-ray photoelectron spectroscopy, glancing angle X-ray diffraction and infrared spectroscopy. Thickness and roughness for the films were measured by stylus profilometry. Optical properties of the coatings were studied by the spectroscopic ellipsometry. Hardness and elastic modulus of the films were measured by nanoindentation technique. Being that microwave ECR CVD process is operating-pressure-sensitive, optimum oxygen activity is very essential for a fixed flow rate of precursor, in order to get a single phase cubic yttrium oxide in the films. To the best of our knowledge, this is the first effort that describes the use of Y(tod)(3) precursor for deposition of Y(2)O(3) films using plasma assisted CVD process.

The effect of particle size on performance of cathode materials of Li-ion batteries

Beginning with the ‘frog-leg experiment’ by Galvani (1786), followed by the demonstrations of Volta pile by Volta (1792) and lead-acid accumulator by Plante´ (1859), several battery chemistries have been developed and realized commercially. The development of lithium-ion rechargeable battery in the early 1990s is a breakthrough in the science and technology of batteries. Owing to its high energy density and high operating voltage, the Li-ion battery has become the battery of choice for various portable applications such as note-book computers, cellular telephones, camcorders, etc. Huge efforts are underway in succeeding the development of large size batteries for electric vehicle applications. The origin of lithium-ion battery lies in the discovery that Li+-ions can reversibly be intercalated into/de-intercalated from the Van der Walls gap between graphene sheets of carbon materials at a potential close to the Li/Li+ electrode. By employing carbon as the negative electrode material in rechargeable lithium-ion batteries, the problems associated with metallic lithium in rechargeable lithium batteries have been mitigated. Complimentary investigations on intercalation compounds based on transition metals have resulted in establishing LiCoO2 as the promising cathode material. By employing carbon and LiCoO2, respectively, as the negative and positive electrodes in a non-aqueous lithium-salt electrolyte,a Li-ion cell with a voltage value of about 3.5 V has resulted.Subsequent to commercialization of Li-ion batteries, a number of research activities concerning various aspects of the battery components began in several laboratories across the globe. Regarding the positive electrode materials, research priorities have been to develop different kinds of active materials concerning various aspects such as safety, high capacity, low cost, high stability with long cycle-life, environmental compatibility,understanding relationships between crystallographic and electrochemical properties. The present review discusses the published literature on different positive electrode materials of Li-ion batteries, with a focus on the effect of particle size on electrochemical performance.

Aza-heterocyclic ligand assisted assembly of new cobalt MOFs with pcu and graphite related structures

A hydrothermal reaction of a mixture of cobalt salt, 5-nitro isophthalic acid and triazole (compound I), 3-aminotriazole (3-AT) (compound II) and 3,5-diaminotriazole (compound III) at 220 degrees C for a day resulted in the isolation of three different, but related, compounds containing cobalt clusters. The three-dimensional compounds have Co-5 (compound-I) and Co-4 (compound-II and compound-III) clusters connected through the carboxylate and triazolate forming structures with pcu net (compound-I and compound-II) and a graphite-related net (compound-III). The water molecules (coordinated and lattice) can be readily re-adsorbed by the structure of compound-I, whereas the removal of the water molecule leads to a collapse of the structures of compound-II and compound-III. The TGA studies suggest the possibility of an intermediate structure for compound-1, which was investigated using in situ single crystal to single crystal (SCSC) transformations. The identification of an intermediate structure during the dehydration/hydration cycle in compound-I is important and provides important pointers about the dynamics of the water molecules in these compounds. Compound-I was also investigated in detail using a variety of spectroscopic techniques such as IR, UV-Vis spectroscopy etc. Magnetic studies on the synthesized compounds indicate anti-ferromagnetic behavior.

Functional characterization of UvrD helicases from Haemophilus influenzae and Helicobacter pylori

Haemophilus influenzae and Helicobacter pylori are major bacterial pathogens that face high levels of genotoxic stress within their host. UvrD, a ubiquitous bacterial helicase that plays important roles in multiple DNA metabolic pathways, is essential for genome stability and might, therefore, be crucial in bacterial physiology and pathogenesis. In this study, the functional characterization of UvrD helicase from Haemophilus influenzae and Helicobacter pylori is reported. UvrD from Haemophilus influenzae (HiUvrD) and Helicobacter pylori (HpUvrD) exhibit strong single-stranded DNA-specific ATPase and 3'5' helicase activities. Mutation of highly conserved arginine (R288) in HiUvrD and glutamate (E206) in HpUvrD abrogated their activities. Both the proteins were able to bind and unwind a variety of DNA structures including duplexes with strand discontinuities and branches, three- and four-way junctions that underpin their role in DNA replication, repair and recombination. HiUvrD required a minimum of 12 nucleotides, whereas HpUvrD preferred 20 or more nucleotides of 3'-single-stranded DNA tail for efficient unwinding of duplex DNA. Interestingly, HpUvrD was able to hydrolyze and utilize GTP for its helicase activity although not as effectively as ATP, which has not been reported to date for UvrD characterized from other organisms. HiUvrD and HpUvrD were found to exist predominantly as monomers in solution together with multimeric forms. Noticeably, deletion of distal C-terminal 48 amino acid residues disrupted the oligomerization of HiUvrD, whereas deletion of 63 amino acids from C-terminus of HpUvrD had no effect on its oligomerization. This study presents the characteristic features and comparative analysis of Haemophilus influenzae and Helicobacter pylori UvrD, and constitutes the basis for understanding the role of UvrD in the biology and virulence of these pathogens.

Synthesis, characterization and pharmacological study of 4,5-dihydropyrazolines carrying pyrimidine moiety

A series of 5-bromo-2-(3,5-diaryl-4,5-dihydro-1H-Pyrazol-1-yl)pyrimidine were prepared under conventional heating as well as microwave reaction condition. The newly synthesized compounds were characterized on the basis of elemental, spectral and single crystal X-ray studies. These new compounds were screened for their antioxidant, anti-inflammatory and analgesic activities. Some of these compounds exhibited potent biological activities compared to the standard drug. (C) 2012 Elsevier Masson SAS. All rights reserved.

Self-Assembly of an Octanuclear Platinum(II) Tetragonal Prism from a New Pt-4(II) Organometallic Star-Shaped Acceptor and Its Nitroaromatic Sensing Study

2 + 4] self-assembly of a pyrene-functionalized Pt-8(II) tetragonal prism (2) is achieved using a newly designed star-shaped organometallic acceptor (1) in combination with an amide-based ``clip'' donor (L). The propensity of this prism (2) as a selective sensor for nitroaromatics (2,4-dinitrotoluene, 1,3,5-trinitrotoluene, and picric acid), which are the chemical constituents of many commercial explosives, has been examined.

Bismuth carboxylates with Brucite- and Fluorite-related structures: synthesis structure and properties

Three new compounds of bismuth, C4N2H10]center dotBi(C7H4NO4)(C7H3NO4)]center dot H2O, I, Bi(C5H3N2O4) (C5H2N2O4)], II, and Bi(mu(2)-OH)(C7H3NO4)], III, have been prepared by the reaction between bismuth nitrate and heterocyclic aromatic dicarboxylic acids, 2,6-pyridinedicarboxylic acid, 4,5-imidazoledicarboxylic acid, and 3,4-pyridinedicarboxylic acid, respectively, under hydrothermal conditions. The structures of all the compounds have linkages between Bi2O2 and the corresponding dicarboxylate forming a simple molecular unit in I, a bilayer arrangement in II, and a three-dimensional extended structure in III. The topological arrangement of the nodal building units in the structures indicates that a brucite-related layer (II) and fluorite-related arrangement (III) can be realized in these structures. By utilizing the secondary interactions, one can correlate the structure of III to a Kagome-related one. The observation of such classical inorganic related structures in the bismuth carboxylates is noteworthy. Lewis acid catalytic studies on the formation of ketal suggest the possible participatory role of the lone pair of electrons. All the compounds are characterized employing elemental analysis, IR, UV-vis, and thermal studies.

Phase transformation, improved ferroelectric and magnetic properties of (1-x) BiFeO3-xPb(Zr0.52Ti0.48)O-3 solid solutions

The authors prepared (1 - x) BiFeO3 - (x)Pb(Zr0.52Ti0.48)O-3 for x <= 0.30 by sol-gel method and investigated the material's structures, magnetic and electrical properties. Detailed Rietveld analysis of X-ray diffraction data revealed that the system retains distorted rhombohedral R3c structure for x <= 0.10 but transforms to monoclinic (Cc) structure for x > 0.10. Disappearance of some Raman modes corresponding to A1 modes and the decrease in the intensities of the remaining A1 modes with increasing x in the Raman spectra, which is a clear indication of structural modification and symmetry changes brought about by PZT doping. Enhanced magnetization with PZT doping content may be attributed to the gradual change and destruction in the spin cycloid structure of BiFeO3. The leakage current density at 3.5 kV/cm was reduced by approximately three orders of magnitude by doping PZT (x = 0.30), compared with BFO ceramics. (C) 2014 AIP Publishing LLC.

Synthesis and antioxidant activity study of pyrazoline carrying an arylfuran/arylthiophene moiety

A novel series of N-acetyl-3-aryl-5-(5-(p/o-nitrophenyl)-2-furyl//thienyl)-substituted pyrazolines (3a-o) were synthesized by the reaction of 1-aryl-3-(5-(p/o-nitrophenyl)-2-furyl/thienyl)-2-propene-1-ones with hydrazine hydrate in acetic acid medium. The structures of the newly synthesized compounds were established by IR, H-1-NMR, mass spectra and a single-crystal X-ray study. The antioxidant activities of the synthesized compounds were determined using the DPPH scavenging assay. The compounds 3a, 3f, 3h and 3o showed moderate activity.

Effect of radio frequency power and thickness on the electrochemical properties of Li2-x MnO3-y thin films

In the present work, Li2-x MnO3-y (LMO) thin films have been deposited by radio frequency (RF) reactive magnetron sputtering using acid-treated Li2MnO3 powder target. Systematic investigations have been carried out to study the effect of RF power on the physicochemical properties of LMO thin films deposited on platinized silicon substrates. X-ray diffraction, electron microscopy, surface chemical analysis and electrochemical studies were carried out for the LMO films after post deposition annealing treatment at 500 A degrees C for 1 h in air ambience. Galvanostatic charge discharge studies carried out using the LMO thin film electrodes, delivered a highest discharge capacity of 139 mu Ah mu m(-1) cm(-2) in the potential window 2.0-3.5 V vs. Li/Li+ at 100 W RF power and lowest discharge capacity of 80 mu Ah mu m(-1) cm(-2) at 75 W RF power. Thereafter, the physicochemical properties of LMO films deposited using optimized RF power 100 W on stainless steel substrates has been studied in the thickness range of 70 to 300 nm as a case study. From the galvanostatic charge discharge experiments, a stable discharge capacity of 68 mu Ah mu m(-1) cm(-2) was achieved in the potential window 2.0-4.2 V vs. Li/Li+ tested up to 30 cycles. As the thickness increased, the specific discharge capacity started reducing with higher magnitude of capacity fading.

Copolyesters from Soybean Oil for Use as Resorbable Biomaterials

A family of soybean oil (SO) based biodegradable cross-linked copolyesters sourced from renewable resources was developed for use as resorbable biomaterials. The polyesters were prepared by a melt condensation of epoxidized soybean oil polyol and sebacic acid with citric acid (CA) as a cross-linker. D-Mannitol (M) was added as an additional reactant to improve mechanical properties. Differential scanning calorimetry revealed that the polyester synthesized using only CA as the cross-linker was semicrystalline and elastomeric at physiological temperature. The polymers were hydrophobic in nature. The water wettability, elongation at break and the degradation rate of the polyesters decreased with increase in M content or curing time. Modeling of release kinetics of dyes showed a diffusion controlled mechanism underlies the observed sustained release from these polymers. The polyesters supported attachment and proliferation of human stem cells and were thus cytocompatible. Porous scaffolds induced osteogenic differentiation of the stern cells suggesting that these polymers are well suited for bone tissue engineering. Thus, this family of polyesters offers a low cost and green alternative as biocompatible, bioresobable polymers for potential use as resorbable biomaterials for tissue engineering and controlled release.