EPR and optical study of Mn2+ doped ammonium tartrate single crystals

EPR study of Mn2+ doped ammonium tartrate single crystals is carried out at room temperature. The spin Hamiltonian parameters are: gx=1.9225+/-0.0002, gy=1.9554+/-0.0002, gz=2.1258+/-0.0002, A=(78+/-2) x 10(-4) cm(-1), B=(75+/-2) x 10(-4) cm(-1), D=(191+/-2) x 10(-4) cm(-1), E=(61+/-2) x 10(-4) cm(-1) and a=(22+/-1) x 10(-4) cm(-1) for site I and gx=1.9235+/-0.0002, gy=1.9574+/-0.0002, gz=2.0664+/-0.0002, A=(78+/-2) x 10(-4) cm(-1), B=(75+/-2) x 10(-4) cm(-1), D=(180+/-2) x 10(-4) cm(-1), E=(57+/-2) x 10(-4) cm(-1) and a=(22+/-1) x 10(-4) cm(-1) for site II, respectively. The observed optical bands are fitted with inter-electronic repulsion parameters (B and C), crystal field parameter (Dq) and Trees correction (alpha) and the values found are B=752, C=2438, Dq=765 and alpha=76 cm(-1). The data obtained are further used to discuss the surrounding crystal field and the nature of metal-ligand bonding in the crystal.     

A Simple and Efficient Approach for Estimating Recovery of a Preparative Reversed Phase HPLC Purification

The widely applied reversed phase high-performance liquid chromatography (RP-HPLC) is an indispensable purification technique in drug discovery. During drug discovery, recovery was usually calculated based on the weight of the purified product after drying over the weight of the crude material multiplied by the assumed purity from HPLC/UV area percent of the product. Such a purity assumption can be off significantly when the crude material contains water, solvents, other UV-inactive impurities and inorganic salts. In this paper, we report a simple and efficient way to estimate recovery of preparative HPLC purification process. It is based on the ratio of the HPLC/UV peak area measured for the product in the crude solution and that in the final collected fraction with both accounted for their volumes. This approach eliminates not only the need for drying of the collected fraction to calculate recovery but also the inaccuracy associated with the true content in the crude sample using the traditional method. A systematic study was conducted to verify this method using caffeine mixed with various UV-active and -inactive impurities. The calculated recoveries using this approach were found to be consistent within 4% with the true recoveries based on dry weight estimation. The approach has been successfully applied for our in-house purifications. Furthermore, the approach was extended to library purifications, where in many cases heart-cutting the desired peaks is used to meet the purity requirements.

     

Gelatin/poly(aniline) composite films: Synthesis and characterization

In this work, glyoxal (Glox) - crosslinked gelatin (Gel) films have been loaded with aniline molecules, followed by their in-situ oxidative polymerization to yield Gel/poly(Ani) composite films. The films, so prepared, have been characterized by FTIR, XRD, TGA and AFM analysis. The water absorption of these films has been studied in the physiological fluid of pH 7.4 at 37°C.The dynamic water uptake data has been interpreted by various kinetic models such as power function model and Schott kinetic model. The various diffusion coefficients have also been evaluated.     

Synthesis, spectral and structural characterisation of ditelluroxanes: μ-oxo-bis[nitrato-; 2,4,6-trinitrophenolato-dialkyl tellurium (IV)]

The synthesis of ditelluroxanes: μ-oxo-bis[nitrato dimethyl tellurium (IV)] [(CH₃)₂TeNO₃]₂O (1), μ-oxo-bis[(2,4,6-trinitro)phenolato dimethyl tellurium (IV)] [(CH₃)₂TeOC₆H₂(NO₂)₃]₂O (2) and μ-oxo-bis[1-(2,4,6-trinitro)phenolato-1,1,2,3,4,5-hexahydrotellurophene] [C₄H₈TeOC₆H₂(NO₂)₃]₂O (3) was achieved. 1 was synthesised by the reaction of (CH₃)₂TeI₂ with fuming HNO₃ while 2 and 3 were synthesised by the reactions of R₂Te(OH)₂ [R₂ = (CH₃)₂, (C₄H₈)] (in situ) with 2,4,6-trinitrophenol [ 2,4,6-(NO₂)₃C₆H₂OH] (picric acid). 1-3 have been investigated through UV/Vis; FT-IR, (¹H, ¹³C) NMR spectroscopy and single crystal X-ray diffraction studies. In 1-3 the immediate coordination geometry about the central tellurium atom can be described as pseudo trigonal bipyramidal and the stereochemically active electron lone pair occupying equatorial position. The supramolecular self-organisations of these tetraorgano ditelluroxanes (1-3) are explained through cooperative participation of Te?O secondary bonds, C-H?O hydrogen bonds and π-stacking of the organic substituents.     

Sorption studies of radionuclides on argillaceous clays of Cuddapah System

Worldwide argillaceous clays are being studied as promising host rock for nuclear high level waste disposal. Cuddapah argillite is under evaluation for Indian clay rock based repository. Herein characterization of this clay and evaluation for its sorption characteristics towards Cs(I) and Eu(III) has been studied. Surface complexation modeling of Cs(I) sorption on argillaceous clay revealed that Cs(I) is sorbed on high as well as low affinity ion exchange sites. In modeling of Eu(III) sorption data, surface complexes of Eu(III) and europium carbonate species, along with ion exchange reaction, reproduced the sorption profile with ankerite dissolution influencing distribution of various surface complexes.     

Bulk heterojunction solar cells made from carbazole copolymer and fullerene derivative with an inserted layer of discotic material with improved efficiency

Bulk heterojunction photovoltaic cells based on composites of copolymer poly [N-90-hepta-decanyl-2,7-carbazole-alt-5,5-(40,70-di-2-thienyl-20,10,30-benzothiadiazole)] and the fullerene derivative [6,6]-phenyl C71-butyric acid methyl ester with an inserted layer of discotic liquid crystalline material (2, 3, 6, 7, 10, 11-hexabutyloxytriphenylene) between the interface of active layer and hole transporting layer has been reported. Different hole transporting layers deposited on indium tin oxide substrates such as poly (3,4-ethylenedioxythiophene)-poly (styrenesulphonate) or molybdenum trioxide has been used in these devices. All the devices with inserted discotic liquid crystal layer showed better performance than the reference cells. Power conversion efficiency of 5.14% was achieved for these photovoltaic solar cells containing self-organised discotic liquid crystal layer of 30 nm thickness under one sun condition which is substantial jump as compared to earlier reports. The mobility of holes in the discotic liquid crystal inserted devices was found to be of the order of 10^–6 cm² V^–1 s^–1 due to which high values of current density was achieved. The influence of varying the thickness of liquid crystal layer and annealing on the photovoltaic parameters of these devices was also studied.     

Superparamagnetic Nanocomposites of Poly(vinyl alcohol-graft-acrylonitrile) as Carrier for Magnetically Assisted Release of Ciprofloxacin

In the present study also a superparamagnetic nanocomposite of Poly (vinyl- alcohol-g-acrylonitrile) has been designed by homogeneous impregnation of iron oxide nanoparticles into the graft polymer matrix. The so prepared nanocomposite was characterized by FT-IR, TEM and XRD techniques and studied for water sorption behavior and magnetization properties. The superparamagnetic nanocomposite was loaded with an antibiotic drug, ciprofloxacin (CFx), and its release behavior was investigated under varying experimental conditions such as chemical composition of the matrix, pH of the release media, applied magnetic field and percent loading of the drug. The drug transport mechanism was also analyzed using Ficks power law. The drug loaded magnetic nanocomposite was also studied for antibacterial and in-vitro blood compatible properties.     

Skeletal diverse synthesis of N-fused polycyclic heterocycles via the sequence of Ugi-type MCR and CuI-catalyzed coupling/tandem Pictet-Spengler reaction

Several diversity-oriented syntheses of N-fused polycyclic heterocycles have been demonstrated but most of them are based on point diversity within the same library and usually involve time-consuming sequential multistep syntheses, which also suffer from low yields and/or poor precursor scopes. We have developed a new strategy for the syntheses of skeletal diverse N-fused polycyclic compounds via an Ugi-type MCR followed by a CuI-catalyzed coupling reaction or tandem Pictet-Spengler reaction. This two-step sequence provides eight distinct skeleton of fused {6-5-5-6}, {5-5-5-6}, {6-5-6-6}, and {5-5-6-6} ring systems that have applications in medicinal chemistry and chemical genetics too.     

Sequential approach to the synthesis of 'U and Z' shaped polycyclic heteroarenes

The synthesis of three new classes of heteroarenes, built through the sequential fusion of naphthalene, benzo/naphtho[b]oxepine and thiochromene rings with pyran and pyrimidine ring systems to give 'U and Z' shaped structural frameworks is reported. The methodology is based on the synthesis of pyran fused intermediates, 1-methylthio-3-oxo-5,6-dihydro-3H-benzo[f]chromene-2-carbonitrile (3), 4-methylthio-2-oxo-5,6-dihydro-2H-benzo/naphtho[b]pyrano[2,3-d]oxepine-3-carbonitriles (10, 20) and 4-methylthio-2-oxo-2,5-dihydrothiochromeno[4,3-b]pyran-3-carbonitriles (15) from the reaction of 2-tetralone, benzo/naphtho[b]oxepin-5-ones and thiochromen-4-ones with methyl 2-cyano-3,3-dimethylthioacrylate respectively. Further condensation of intermediates 3, 10, 20 and 15 with amidines led to the formation of tetracyclic 'U' shaped 4-amino-2-aryl-7,8-dihydro-5-oxo-5H-naphtho[2,1-b]pyrimido[4,5-d]pyrans (8) and 'Z' shaped 4-amino-2-aryl-5-oxo-12,13-dihydro-5H-benzo/naphtho[b]oxepino[5,4-b]pyrimido[4,5-d]pyrans (12, 22) and 4-amino-2-aryl-5-oxo-5,12-dihydrothiochromeno[4,3-b]pyrimido[4,5-d]pyrans (17). Compound 12f forms a chain of dimers through N-HO interactions as indicated by the X-ray structure analysis, and the quantum chemical calculations performed at the MP2 level indicate that this interaction energy is 10 kJ mol(-1).