Magnetic, electronic and electrochemical studies of mono and binuclear Cu(II) complexes using novel macrocyclic ligands

A series of new mono and binuclear copper (II) complexes [Cul]X(2)and [Cu(2)lX(2)] where 1 = L(1), L(2) and L(3) are the macrocyclic ligands. In mononuclear complexes the geometry of Cu(II) ion is distorted squareplanar and in binuclear complexes the geometry of Cu(II) is tetragonal. The synthesized complexes were characterized by spectroscopic (IR,UV-vis and ESR) techniques. Electrochemical studies of the complexes reveals that all the mononuclear Cu(II) complexes show a single quasireversible one-electron transfer reduction wave (E(pc) = -0.76 to -0.84V) and the binuclear complexes show two quasireversible one electron transfer reduction waves (E(pc)(1) = -0.86 to -1.01V, E(pc)(2) = -1.11 to -1.43V) in cathodic region. The ESR spectra of mononuclear complexes show four lines with nuclear hyperfine splittings with the observed g(11) values in the ranges 2.20-2.28, g( perpendicular) = 2.01-2.06 and A(11) = 125-273. The binuclear complexes show a broad ESR spectra with g = 2.10-2.11. The room temperature magnetic moment values for the mononuclear complexes are in the range [mu(eff) = 1.70-1.72BM] and for the binuclear complexes the range is [mu(eff) = 1.46-1.59BM].     

Syntheses in enantiopure form of four diastereoisomeric naphthopyranquinones derived from aphid insect pigments

The first syntheses are described of the four enantiopure naphthopyranquinones (1R,3R,4S)- and (1R,3R,4R)-3,4-dihydro-4,7,9-trihydroxy-1,3-dimethylnaphtho[2,3-c]pyranquinone (quinone A 1 and quinone A' 2) and their two C-3 epimers, the (1R,3S,4S)- and (1R,3S,4R)-diastereoisomers 5 and 6, using enantiopure lactate as the source of asymmetry. Key factors in these syntheses are the maintenance of stereochemical integrity throughout the sequences and intramolecular diastereoselective cyclisations of the titanium phenolates of phenolic lactaldehydes. For these cyclisations the differing degree of diastereoselectivity is explained as are the stereochemistries of the product 2-benzopyran-4,5-diols.     

Structural,electronic and transport properties of X<Subscript>3</Subscript>SnC (X=Cr/Mn/Cu) electrodes—first principle approach

The density functional theory is approached for the comparative study of electronic, transport and magnetic properties of SnC electrode and X₃SnC (X?=?Cu/Mn/Cr) electrodes. The cohesive energy analysis exhibits the highest stability of SnC which reduces gradually by dispersing of elements Cr/Mn/Cu, bulk modulus shows highest compressibility of Cu₃SnC electrode. Enthalpy of SnC reveals its strongest forming ability and alloying nature. The energy band diagrams exhibit the semiconducting nature of SnC electrode and conducting nature of Cu₃SnC/Mn₃SnC/Cr₃SnC electrodes. The spin-up and spin-down density of states explains the magnetic nature of Mn₃SnC and Cr₃SnC electrodes. The ionicity factor reveals the purely covalent and partially ionic nature of inter atomic bonds of Sn-X/C-X. The current voltage characteristics also reveal the semiconducting nature of SnC, purely metallic nature of Cu₃SnC electrode, and the negative resistance features of Mn₃SnC and Cr₃SnC electrodes. Transmission curves also support the current voltage characteristics.     

Determination of sulfite with emphasis on biosensing methods: a review

Sulfite is used as a preservative in a variety of food and pharmaceutical industries to inhibit enzymatic and nonenzymatic browning and in brewing industries as an antibacterial and antioxidizing agent. Convenient and reproducible analytical methods employing sulfite oxidase are an attractive alternative to conventional detection methods. Sulfite biosensors are based on measurement of either O₂ or electrons generated from splitting of H₂O₂ or heat released during oxidation of sulfite by immobilized sulfite oxidase. Sulfite biosensors can be grouped into 12 classes. They work optimally within 2 to 900 s, between pH 6.5 and 9.0, 25 and 40 °C, and in the range from 0 to 50,000 μM, with detection limit between 0.2 and 200 μM. Sulfite biosensors measure sulfite in food, beverages, and water and can be reused 100–300 times over a period of 1–240 days. The review presents the principles, merits, and demerits of various analytical methods for determination of sulfite, with special emphasis on sulfite biosensors.     

Enzymatic Degradation of Monocrotophos by Extracellular Fungal OP Hydrolases

The present study explores the potential of extracellular fungal organophosphate (OP) hydrolase for the degradation of monocrotophos. Extracellular OP hydrolases were isolated and purified from five different fungal isolates viz. Aspergillus niger (M1), Aspergillus flavus (M2), Penicillium aculeatum (M3), Fusarium pallidoroseum (M4), and Macrophomina sp. (M5) by AmSO₄ precipitation, dialysis, and G-100 chromatography. M3 showed highest percentage yield of 68.81 followed by 55.41 % for M1. Each of the purified enzyme fraction constituted of two different subunits of 33- and 67-kDa molecular weight. Optimum enzyme fraction (150 μg ml^?1) rapidly degraded monocrotophos within 120 h in phosphorus-free liquid culture medium (CZM) with K _deg of 0.0368, 0.0138, 0.048, 0.016, 0.0138, and 0.048 day^?1 and half-life of 0.79, 2.11, 0.6, 1.8, and 2.11 days for M1, M2, M3, M4, and M5, respectively. The results were further confirmed by high performance thin layer chromatography and Fourier transform infrared which indicate the disappearance of monocrotophos by hydrolytic cleavage of vinyl phosphate bond. The overall order of enzymatic degradation was found to be P. aculeatum > A. niger > F. pallidoroseum > A. flavus = Macrophomina sp. Hence, the study concludes that extracellular OP hydrolases efficiently degraded monocrotophos and could be used as a potential candidate for the detoxification of this neurotoxin pesticide.     

Reversed-phase high-performance liquid chromatographic, gel electrophoretic and size exclusion chromatographic studies of subunit structure of arachin and its molecular species

Arachin and its molecular species (arachin I and arachin II) were separated and isolated. The number and kind of subunits of arachin, arachin I and arachin II were determined. Studies were carried out under different experimental conditions using slab gel electrophoresis, size-exclusion chromatography and reversed-phase high-performance liquid chromatography. Gel electrophoresis was done under varying concentrations of resolving gel. Tube gel as well as slab gel electrophoresis were used and continuous as well as discontinuous buffer systems were used for both types of electrophoresis. In addition, the subunits were separated by reversed-phase HPLC using a gradient program. Arachin and arachin II were found to have 12 subunits each while arachin I showed six subunits. The subunits of arachin I were allowed to reconstitute by removing SDS. Eight combinations were tried for studying the reconstitution pattern. Molecular weight and weight ratio in each case were also determined.     

Synthesis,X-ray structure determination and analysis of packing interactions in 9-(1,2-propenyl)-6-carboethoxy-2-methyl-2,3-dihydrofuro[2,3-h]-benzopyran-5H-one

Claisen rearrangement of ethyl-2,4-diallyloxy--carbethoxycinnamate (1) in refluxing DMA afforded ethyl-9-allyl-2-methyl-2,3-dihydrofuro(2,3-h)benzopyran-5H-one-6-carboxylate (2) in a single step. Dehydrogenation with Pd/C (10%) in DPE furnished an unexpected isomeric compound, 9-(1,2-propenyl)-6-carbethoxy-2-methyl-2,3-dihydrofuro[2,3-h]-benzopyran-5H-one (3). This compound, C₁₈H₁₈O₅, crystallizes in the monoclinic space group P2₁/n with unit cell parameters, a = 7.346(1), b = 16.482(3), c = 12.653(2),Å, and = 92.71(1)°. The structure has been solved by direct methods and refined to R = 0.056 for 1719 observed reflections. The coumarin nucleus is planar. The five-membered ring is in envelope-conformation. The crystal structure is stabilized by intra- and intermolecular CHO hydrogen bonds.     

Thermophysical and sonochemical behaviour of binary mixtures of decan-1-ol with halohydrocarbons at (T = 293.15 and 313.15) K

Densities and ultrasonic velocities of binary mixtures of decan-1-ol with 1,2-dichloroethane, 1,2-dibromoethane, and 1,1,2,2-tetrachloroethene have been measured over the entire range of composition at T = (293.15 and 313.15) K and at atmospheric pressure. From these results, the excess molar volumes, molar free volumes, excess molar isentropic compressibilities, limiting excess partial molar volumes, and isentropic compressibilities, intermolecular free lengths, and available volumes by three methods, thermal expansion coefficients, parameters related to space-filling ability, intermolecular free lengths, and molecular radii have been calculated. The experimental ultrasonic velocities have been analyzed in terms of the ideal mixture relations of Nomoto and Van Dael, Jacobson’s free length, Schaaff’s collision factor, Flory’s statistical, and Prigogine–Flory–Patterson theories and thermoacoustical parameters.