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1.
The binary molybdate Li2Zn2(MoO4)3 of a new crystal type was characterized by EPR, optical spectroscopy, and X-ray diffraction methods. The crystals have the Pnma symmetry group and the lattice parameters a = 5.1139(5) Å, b = 10.4926(13) Å, c = 17.6445(22) Å; Z = 4. The crystals possess scintillation properties; emission is caused by the presence of impurity levels in the forbidden band. The EPR studies of the nature of the impurity centers responsible for the scintillation characteristics of the crystal showed that the centers were Cu2+ ions substituted for zinc ions in the oxygen octahedra. The directions of the main values of the g and tensors (g zz , A zz ) correspond to the direction of O-Cu-O of the oxygen octahedron distorted along the Z axis. The EPR spectra of the copper ions are described by the spin Hamiltonian with the parameters g = 2.38, g = 2.06; A = 116 G, A = 0 G.  相似文献   

2.
Comprehensive investigations have been performed by EPR and optical spectroscopy for Bi3GeO4 crystals doped with chromium ions. It is demonstrated that the known optical absorption spectrum for chromium ions, specifically, the triplet in the region 600–900 nm has an analog in the EPR spectra — the center with electron spin S = 1. The spectrum is described by the spin-Hamiltonian with the parameters D = 550 G, E = 10 G, g xx = g yy = 1.915, g zz = 1.932. The EPR spectrum is dictated by Cr4+ incorporation at the germanium sites. Luminescence observed in the region 1.2–1.7 μm is also caused by transitions of Cr4+ with tetrahedral surroundings to germanium sites. Original Russian Text Copyright ? 2005 N. V. Chernei, V. A. Nadolinnyi, N. V. Ivannikova, V. A. Gusev, I. N. Kupriyanov, V. N. Shlegel, and Ya. V. Vasiliev __________ Translated from Zhurnal Strukturnoi Khimii, Vol. 46, No. 3, pp. 444–450, May–June, 2005.  相似文献   

3.
The binuclear copper(II) complexes with acyldihydrazones formed by 1,4-cyclohexanedicarboxylic acid and salicylaldehyde or 2-hydroxyacetophenone were synthesized and studied. The structure of the complex with 1,4-cyclohexanedicarboxylic acid bis(salicylidene)hydrazone (H4L1) [Cu2L1(Py)2] was studied by X-ray diffraction. The crystals are triclinic: a = 8.1852(4) Å, b = 8.5157(5) Å, c = 11.6553(7) Å, α = 80.678(3)°, β = 70.041(4)°, γ = 74.803(3)°. Space group \(P\bar 1\), Z = 1. The number of symmetrically independent reflections with I > 2(σ(I)) is 2245, R = 0.0395; R w = 0.0917. The complex contains two equivalent copper atoms located at a 10.772 Å distance from each other. The coordination polyhedra have a square geometry and are involved in the intermolecular π/π-stacking. The EPR spectra of solutions of the binuclear complexes show an isotropic signal of seven HFS lines (g = 2.113–2.118, A Cu ≈ 38 G), indicating interaction between the unpaired electrons and the two equivalent copper nuclei. The possible exchange interaction channels were analyzed.  相似文献   

4.
9-Diazofluoren adds in Et2O at 20°C to methyltetrolate in keeping with Auwers rule and nonregioselectively adds to methyl-3-phenylpropiolate with the formation of spirocyclic 3H-pyrazoles. The methyltetrolate adduct at boiling in toluene converts into methyl 3a-methyl-3aH-dibenzo[e,g]indazole-3-carboxylate, at 190°C in benzene, into methyl 3-methyl-2H-dibenzo[e,g]indazole-2-carboxylate, and at 160°C in methanol, into 3-methyl-2H-dibenzo[e,g]indazole. Auwers adduct of methyl 3-phenylpropiolate at boiling in benzene gives cyclopropene derivative and at boiling in methanol isomerizes into methyl 3a-phenyl-3aHdibenzo[e,g]indazole-3-carboxylate. Anti-Auwers adduct at boiling in benzene isomerizes into methyl 2-phenylpyrazolo[1,5-f]phenanthridine-3-carboxylate.  相似文献   

5.
From three cell-associated β-xylosidases produced by Aureobasidium pullulans CBS 135684, the principal enzyme was enriched to apparent homogeneity and found to be active at high temperatures (60–70 °C) over a pH range of 5–9 with a specific activity of 163.3 units (U) mg?1. The enzyme was thermostable, retaining over 80% of its initial activity after a 12-h incubation at 60 °C, with half-lives of 38, 22, and 10 h at 60, 65, and 70 °C, respectively. Moreover, it was tolerant to xylose inhibition with a K i value of 18 mM. The K m and V max values against p-nitrophenyl-β-d-xylopyranoside were 5.57 ± 0.27 mM and 137.0 ± 4.8 μmol min?1 mg?1 protein, respectively. When combining this β-xylosidase with xylanase from the same A. pullulans strain, the rate of black liquor xylan hydrolysis was significantly improved by up to 1.6-fold. The maximum xylose yield (0.812 ± 0.015 g g?1 dry weight) was obtained from a reaction mixture containing 10% (w/v) black liquor xylan, 6 U g?1 β-xylosidase and 16 U g?1 xylanase after incubation for 4 h at 70 °C and pH 6.0.  相似文献   

6.
The structure of the mebicar molecule has been studied by gas-phase electron-diffractometry using quantum chemical calculations. An eclipsed conformation along the C-C bond (torsion angle ?(H-C-C-H) = 10°) and flattened semi-chair conformations of cyclic fragments have been found. The bond lengths (r g ) and angles (∠α) show the following average values: r(C-C) 1.576(3) Å, r(C-N) 1.460(3) Å, r(C(O)-N) 1.390(4) Å, r(C=O) 1.211(5) Å, r(C-H) 1.090(5) Å, ∠CCN 103.0(5)°, ∠CNC(O) 112.2(1)°, ∠CNC 122.4(1)°. The dihedral angle between the cyclic fragments is 116.6°.  相似文献   

7.
A complex [Zn(C8H7O3)2(H2O)2] (C8H8O3 is vanillin) has been synthesized and characterized by IR, elemental analysis, and X-ray diffraction single-crystal analysis. The crystals are monoclinic, space group C2/c, a = 22.236(8) Å, b = 10.594(2) Å, c = 7.8190(16) Å, α = 89.90(3)°, β = 106.87(4)°, γ = 89.99(3)°, V = 1762.6(8) Å3, Z = 4, F(000) = 832, S = 1.079, ρ c = 1.521g cm?3, R = 0.0221, R w = 0.0604, μ = 1.433 mm?1. The Zn2+ ion is six-coordinated with a distorted octahedron geometry. The complex forms a three-dimensional network through intermolecular hydrogen bonds. The thermal decomposition kinetics of the complex for the second stage was studied under non-isothermal conditions by the TG and DTG methods. The kinetic equation can be expressed as dα/dt = Ae?E/RT 2(1 ? α)[1 ? ln(1 ? α)]1/2. The kinetic parameters (E, A), activation entropy ΔS , and activation free-energy ΔG were also gained.  相似文献   

8.
The molecular structure of 2-chlorobenzenesulfonyl chloride was studied by electron diffraction and quantum-chemical (2/6-31G**, B3LYP/6-311++G**) methods at 337(3) K. Only one (C 1) conformer was found in the gas phase. The following structural parameters were obtained: r h1(C-H)av = 1.105(6) Å, r h1(C-C)av = 1.398(3) Å, r h1(C-S) = 1.783(11) Å, r h1(S=O)av = 1.427(3) Å, r h1(S-Cl) = 2.048(4) Å, r h1(C-Cl) = 1.731(9) Å, ∠(C-S=O1) = 109.9(8) °, ∠(C-S=O2) = 106.9(8) °, ∠(Cl1-S-O1) = 107.3(4) °, ∠(Cl1-S-O2) = 106.4(4) ∠, ∠C-S-Cl = 102.1(6) °, ∠O=S=O = 122.3(11) °. The C2-C1-S-Cl1 torsion angle that defines the position of the S-Cl bond relative to the plane of the benzene ring was 69.7(8) °. The B3LYP/6-311++G** calculated barriers of internal rotation of the sulfonyl chloride group were V 01 = 9.7 kcal/mol and V 02 = 3.6 kcal/mol.  相似文献   

9.
The products of 4′,5′-dibromobenzo-15-crown-5 (I) cyanation by the Rosenmund-Braun reaction are studied by the 1H NMR and IR spectroscopy methods. X-ray diffraction analysis of two isolated products, i.e., di(4′,5′-dicyanobenzo-15-crown-5) 1.6 hydrate {(CN)2B15C5}2 · 1.6H2O (IIa) and 4′,5′-dicyanobenzo-15-crown-5,4′-cyano-5′-cyano(bromo)benzo-15-crown-5 dihydrate (CN)3.85Br0.15(B15C5)2 · 2H2O (III) is performed. Crystals IIa are monoclinic, a = 15.882(2) Å, b = 11.412(2) Å, c = 18.484(3) Å, β = 100.717(3)°, V = 3291.7(9) Å3, Z = 4, space group P21/c, R = 0.0746 for 4775 reflections with I > 2σ(I). Crystals III are monoclinic, a = 15.956(3) Å, b = 11.425(2) Å, c = 18.865(4) Å, β = 99.32(3)°, V = 3394(1) Å3, Z = 4, space group P21/c, R = 0.0692 for 2070 reflections with I > 2σ(I). Compounds IIa and III have similar structures with two crystallographically independent molecules in each (A and B in IIa; C and D in III). Four of the five O atoms of a macrocycle in molecules A and C form hydrogen bonds with the water molecules. The latter molecules lie above and below the cycle plane at a distance of ~2 Å from this plane. The A and C molecules have identical conformations (TTG TTG TTG TTG TTC) that differ from those of molecules B (TTG TGG STT SSG TTC) and D (TTC TSG STT SSG TTC).  相似文献   

10.
Four new low melting salts, “Ionic Liquids” consisting of the [CrIII(NCS)4(Phen)]? complex monoanion and imidazolium based cations A, with A = 1-ethyl-3-methylimidazolium (EMIm), 1-butyl-3-methylimidazolium (BMIm), 1,3-dimethyl-2,4,5-triphenylimidazolium (DML), and 1,2,3,4,5-pentamethyl-imidazolium (PMIm), were investigated. Single-crystal X-ray investigations established the structures of the four compounds. (EMIm)[Cr(NCS)4(Phen)] (I): triclinic, \(P\bar 1\), a = 8.1382(6), b = 10.4760(8), c = 16.003(1) Å, α = 90.330(4)°, β = 94.759(4)°, γ = 107.305(4)°, Z = 2, R 1(F)/wR 2(F 2) = 0.0650/0.1770; (BMIm)[Cr(NCS)4(Phen)] (II): triclinic, \(P\bar 1\), a = 8.5545(4), b = 9.8620(4), c = 16.6762(6) Å, α = 92.503(2)°, β = 97.517(2)°, γ = 91.249(2)°, Z = 2, R 1(F)/wR 2(F 2) = 0.0393/0.0848; (DML)[Cr(NCS)4(Phen)] · C3H6O (III): triclinic, \(P\bar 1\), a = 11.0475(9), b = 13.589(1), c = 14.582(1) Å, α = 83.013(4)°, β = 87.116(4)°, γ = 70.333(5)°, Z = 2, R 1(F)/wR 2(F 2) = 0.0407/0.1023; (PMIm)[Cr(NCS)4(Phen)] · C3H6O (IV): orthorhombic, Pbca, a = 17.379(1), b = 16.514(1), c = 22.304(1) Å, Z = 8, R 1(F)/wR 2(F 2) = 0.0460/0.1107 (in addition III and IV contain co-crystallized acetone molecules). Each compound was characterized by elemental analysis, NMR, IR, und UV-Vis spectroscopy. Magnetic properties were derived from NMR investigations (EVANS method). All four compounds are paramagnetic with effective magnetic moments of spin-only CrIII. Melting points were obtained from DSC measurements. All melting points are higher than required for “Ionic Liquids”, but nevertheless “low” for molten salts.  相似文献   

11.
Properties of beta-glucosidase produced by Aspergillus niger URM 6642 recently isolated from the Atlantic rainforest biome and its potential tolerance to saccharification of lignocellulosic biomass products and fermentation inhibitors was evaluated. The fungus was cultivated under solid state culture conditions at 37°C with different agro-industrial wastes. High levels of beta-glucosidase (3778.9 U g?1)from A. niger were obtained with rice meal as substrate under solid state culture conditions after ten days. Optimum pH for this particular beta-glucosidase activity was 4.0 although it was stable in the range of 4.0 to 7.0. The half-life (T½) of beta-glucosidase at 55°C is 3 h. However, at the optimum temperature of the enzyme, 65°C, T½ is 20 min. The enzyme showed tolerance to various compounds such as glucose, xylose, 5-hydroxymethyl furfural, furfural, coumarin, ethanol and acetic acid. Therefore, beta-glucosidase from the novel A. niger species may be of potential use in the saccharification of lignocellulosic biomass, as well as an additional enzyme supplement in cellulase cocktails used to increase the yield of fermentable sugars.  相似文献   

12.
A combined electron diffraction and quantum-chemical (MP2/6-31G**) study of the molecular structure of 2-methylbenzenesulfochloride at 336(5) K was carried out. It was found that the gas phase contained only one conformer, C 1. The following structural parameters were obtained: r h1(C-H)av = 1.095(8) Å, r h1(C-C)Ph = 1.402(4) Å, r h1(CPh-Cmeth) = 1.507(13) Å, r h1(CPh-S) = 1.763(6) Å, r h1(S=O) = 1.418(4) Å, r h1(S-Cl) = 2.048(5) Å, ∠(H-C-H)meth/av = 107.3(96)°, ∠(Cl-S-O)av = 106.4(3)°, ∠CPh-S-Cl = 100.8(9), ∠O=S=O = 120.8(10)°. The CC-CS-S-Cl torsion angle that defines the position of the S-Cl bond relative to the plane of the benzene ring is 75.6(20)°. The B3LYP/6-311+G** calculated barriers of internal rotation of the methyl and sulfochloride groups are 1.2 kcal/mol and V 01 = 10.2 (V 02 = 4.1) kcal/mol, respectively.  相似文献   

13.
A new compound, (dibenzo-18-crown-6)ammonium bromide tetrahydrofuran solvate [NH4(Db18C6)]+ · Br? · THF (I), is synthesized and studied by X-ray diffraction analysis. The crystals of compound I are triclinic: a = 8.848 Å, b = 9.696 Å, c = 16.023 Å, α = 73.75°, β = 86.93°, γ = 78.06°, Z = 2, space group P \(\bar 1\). The structure of compound I is solved by a direct method and refined by full-matrix least squares in the anisotropic approximation to R = 0.095 by 5624 independent reflections (CAD-4 automated diffractometer, γMoK α). The Db18C6 molecule in structure I has a butterfly conformation with approximate symmetry C 2v . The NH 4 + cation where three disordered H atoms form hydrogen bonds with all six O atoms of the Db18C6 molecule is situated in the center of the cavity of the eighteen-membered macrocycle of the Db18C6 molecule. One ordered H atom of the NH 4 + cation forms a strong hydrogen bond with the Br? anion.  相似文献   

14.
The hydroquinone-dimethyl sulfoxide-toluene system was investigated by thermal and X-ray diffraction analyses. The crystal structure of the 1:1 complex of hydroquinone with dimethyl sulfoxide was determined. Crystal data: C8H12O3S, M = 188.24, triclinic system, space group P1¯, unit cell parameters: a = 7.4202(2) Å, b = 8.4046(3) Å, c = 8.7340(3) Å; α = 100.830(1)°, β = 99.794(1)°, γ = 114.129(1)°; V = 469.35(4) Å3, Z = 2, d calc = 1.332 g/cm3, R1 = 0.028, T = 100 K. The molecules are linked in a supramolecular assembly via D-H...A hydrogen bonds (D = O, C; A = O, π).  相似文献   

15.
The crystal structures of catechol (o-dihydroxybenzene) and its 2:1 complex with dimethylsulfoxide are determined at T = 150 K. Crystal data: C14H18O5S, M = 298.37, triclinic, space group P \(\bar 1\), unit cell parameters: a = 7.7285(13) Å, b = 9.9924(17) Å, c = 10.3188(18) Å, α = 89.963(4)°, β = 89.968(4)°, γ = 69.076(5)°, V = 744.3(2)Å3, Z = 2, D x = 1.331 g/cm3, R1 = 0.048; C6H6O2, M = 110.11, monoclinic, space group P21/n, a = 9.8206(6)Å, b = 5.5903(3)Å, c = 10.4439(6)Å, β = 114.952(2)°; V = 519.85(5) Å3, Z = 4, D x = 1.407 g/cm3, R1 = 0.0289. In the 2:1 complex the molecules are joined in a supramolecular ensemble by D-H...A hydrogen bonds (D = O, C; A = O, π); in catechol they are bonded only by O-H...O. The state diagram of the catechol-dimethylsulfoxide system is examined by DTA.  相似文献   

16.
The thermal transformations of disubstituted cesium orthophosphate crystal hydrate under heating in air up to 400°C have been studied. The dehydration process occurs in two stages with the loss of 0.6 water molecules at 60?100°C and 1.4 water molecules at 100?160°C. Anhydrous Cs2HPO4 is stable up to 300°C and is completely converted into cesium pyrophosphate Cs4P2O7 at 330°C. The structure of Cs2HPO4 · 2H2O has been determined. The compound crystallizes in monoclinic space group P21/c and has the unit cell parameters a = 7.4761(5) Å, b = 14.2125(8) Å, c = 7.9603(6) Å, β = 116.914(5)°, V = 754.20(9) Å3, and Z = 4 at?123°C. An earlier unknown polymorph of Cs4P2O7 has been found. According to X-ray powder diffraction data, hexagonal space group Р63 has been proposed for the formed pyrophosphate.  相似文献   

17.
A copper(II) complex with salicylaldehyde N-(2-salicylideneiminoglutaryl)hydrazone (H4L) of the formula [Cu2L · 2Py]2 · 8H2O (I) was obtained and characterized by X-ray diffraction. The crystals are monoclinic, space group P21, a = 13.0663 Å, b = 16.5553 Å, c = 17.7650 Å, β = 97.9420°; Z = 4. The complex is tetranuclear with a “dimer-of-dimers” structure in which the copper cations of two binuclear subunits are linked by phenoxy bridges. The EPR spectra of solutions of complex I show a superposition of two signals of four HFS lines (g 1 = 2.111, a 1 = 56.8 × 10?4 cm?1 and g 2 = 2.183, a 2 = 71.0 × 10?4 cm?1).  相似文献   

18.
Equilibrium geometric parameters, normal mode frequencies and intensities in IR spectra, atomization enthalpy, and relative energies of low-lying electronic states of scandium fluoride molecules (ScF, ScF2, and ScF3) are calculated by the coupled-cluster method (CCSD(T)) in triple-, quadruple, and quintuple-zeta basis sets with the subsequent extrapolation of the calculation results to the complete basis set limit. The ScF molecule is also studied by the CCSDT technique. The error in the approximate calculation of triple excitations in the CCSD(T) method does not exceed 0.002 Å for the equilibrium internuclear distance R e, 4 cm?1 for the vibrational frequency, and 0.2 kcal/mol for the dissociation energy of the molecule. In the ground electronic state \(\tilde X^2 \) A 1(C 2ν ) of ScF2 molecules, R e(Sc-F) = 1.827 Å and αe(F-Sc-F) = 124.2°; the energy barrier to bending (linearization) h = E min(D g8h ) ? E min(C) = 1652 cm?1. The relative energies of Ã2Δ g and \(\tilde B^2 \)Π g electronic states are 3522 cm?1 and 14633 cm?1 respectively. The bond distance in the ScF3 molecule (\(\tilde X^1 \) A1, D 3h ) is refined: R e(Sc-F) = 1.842 Å. The atomization enthalpies Δat H 298 0 of ScF k molecules are 139.9 kcal/mol, 289.0 kcal/mol, and 444.8 kcal/mol for k = 1, 2, 3 respectively.  相似文献   

19.
Lignin polymers in bamboo (Phyllostachys pubescens) were decomposed into polyphenols at high temperatures and oxidized for the introduction of quinone groups from peroxidase extracted from bamboo shoots and catalysis of UV. According to the results of FT-IR spectra analysis, neutral proteases (NPs) can be immobilized on the oxidized lignin by covalent bonding formed by amine group and quinone group. The optimum condition for the immobilization of NPs on the bamboo bar was obtained at pH 7.0, 40 °C, and duration of 4 h; the amount of immobilized enzyme was up to 5 mg g?1 bamboo bar. The optimal pH for both free NP (FNP) and INP was approximately 7.0, and the maximum activity of INP was determined at 60 °C, whereas FNP presented maximum activity at 50 °C. The Km values of INP and FNP were determined as 0.773 and 0.843 mg ml?1, respectively; INP showed a lower Km value and Vmax, than FNP, which demonstrated that INP presented higher affinity to substrate. Compared to FNP, INP showed broader thermal and storage stability under the same trial condition. With respect to cost, INP presented considerable recycling efficiency for up to six consecutive cycles.  相似文献   

20.
The structure and EPR spectra of copper(II) complexes with bis(salicylidene)hydrozones of N-benzoyl-L-aspartic and N-benzoyl-L-glutamic acids have been described. The compounds have been studied by chemical and thermal analyses, IR spectroscopy, and EPR spectroscopy. The molecular and crystal structure of the copper(II) complex with bis(salicylidene)hydrozone of N-benzoyl-L-aspartic acid (H4L) of composition [Cu2L · 2Py] · 2CH3OH · H2O has been determined by X-ray single-crystal diffraction. The crystals are monoclinic: a = 10.3316(7) Å, b = 16.7552(9) Å,c = 11.0137(6) Å, β = 105.758(3)°, space group P21, Z = 2. The complex has a polymeric structure composed of alternating copper-containing binuclear fragments bound to each other either via phenoxy bridges or via an aliphatic spacer (the Cu…Cu distances are 3.471 Å and 8.939 Å, respectively). The EPR spectra of the solutions of the complexes under study shows an isotropic signal comprising seven HFS lines due to two equivalent copper nuclei with the spin Hamiltonian parameters g = 2.115–2.122 and a Cu = (36.1–36.9) × 10?4 cm?1, which indicates the reaization of weak exchange coupling of the paramagnetic centers.  相似文献   

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