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1.
Quantum-chemical calculations of the geometry and energies of nine possible isomers of 12-vertex cobaltacarborane CpCoC2B9H11 (1) were carried out by the DFT method (PBEPBE/DGDZVP/DGA1). Thermodynamic stability of the isomers increases with increasing distance between the carbon atoms in the cage and is virtually independent of the position of the CpCo vertex. The relative stabilities of the 1,2,3-(17.57 kcal mol−1), 1,2,4-(3.72 kcal mol−1), and 1,2,9-isomers of 1 (0 kcal mol−1) are similar to the corresponding values for the ortho (17.61 kcal mol−1), meta (3.21 kcal mol−1), and para isomers (0 kcal mol−1) of carborane C2B10H12. The results of the present study confirm a close similarity of the CpCo and BH fragments in metallacarborane chemistry. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1557–1559, July, 2005.  相似文献   

2.
The neutral dinuclear iron nitrosyl complex [Fe2(SC3H5N2)2(NO)4] (1) of the “g = 2.03” family with a ligand analogous to natural mercaptohistidine was synthesized by the metathesis reaction of the thiosulfate ligands in the [Fe2(S2O3)2(NO)4]2− anion with imidazolidine-2-thiolate ligands. The electrochemical determination of nitrogen oxide in solution showed that compound 1 has a lower NO-donor ability compared to the iron complexes with 1-methylimidazole-2-thiol and imidazole-2-thiol synthesized earlier. Study of the magnetic properties of polycrystals of 1 demonstrated that the effective magnetic moment at room temperature is ca. 2.45 μB and corresponds to a molecule containing a pair of the noninteracting spins S = 1/2. This is evidence that each iron coordination unit in complex 1 contains one unpaired electron, and the iron atom is in the low-spin state. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 28–34, January, 2007.  相似文献   

3.
Two new heteropolyoxovanadoborates (H2dap)2H6{(VO)12O6[B3O6(OH)]6(H2O)}·13H2O (1, dap = 1,2-diaminopropane) and {[Zn(dien)]2[Zn(dien)(H2O)]4(VO)12O6[B3O6(OH)]6(H2O)}2·15H2O (2, dien = diethylenetriamine) have been hydrothermally synthesized and structurally characterized. Both 1 and 2 contain {(VO)12O6[B3O6(OH)]6(H2O)} cluster (denoted on V12B18), which is constructed by a puckered B18O36(OH)6 ring sandwiched between two triangles of six alternating cis and trans edge-sharing vanadium atoms, and a central water molecule. 1 consists of discrete [V12B18]10− cluster anions with H2dap2+ as counterions, while 2 consists of discrete neutral {[Zn(dien)]2[Zn(dien)(H2O)]4[V12B18]} clusters, which are built from two types of zinc(II) complex fragments connecting with V12B18 cluster through two Zn-(μ 3-O)-B bonds. Interestingly, 2 is the only example of the V12B18 cluster decorated by two types of zinc(II) complex fragments.  相似文献   

4.
Fullerenyl radicals (FR) RC60 · and chemiluminescence (CL) are generated in the presence of O2 in C60—R3Al (R = Et, Bui) solutions in toluene (T = 298 K). The FR are formed due to the addition of the R· radical, which is an intermediate of R3Al autooxidation, to C60. Mass spectroscopy and HPLC were used to identify EtnC60Hm (n, m = 1–6), EtpC60 (p = 2–6), and dimer EtC60C60Et as stable products of FR transformations. As found by ESR, the EtC60 · radical (g = 2.0037) is also generated by photolysis of solutions obtained after interaction in the (C60— R3Al)—O2 system. In the presence of dioxygen, the FR is not oxidized but yields complexes with O2, which appear as broadening of the ESR signals. Chemiluminescence arising in the (C60—R3Al)—O2 system is much brighter (I max = 1.86·108 photon s−1 mL−1) than the known background CL (I max = 6.0·106 photon s−1 mL−1) for the autooxidation of R3Al and is localized in a longer-wavelength spectral region (λmax = 617 and 664 nm). This CL is generated as a result of energy transfer from the primary emitter 3CH3CHO* to the products of FR transformation: RnC60Hm, RpC60, and EtC60C60Et. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 205–213, February, 2007.  相似文献   

5.
The rate constants of the reactions of the chlorine atom with C3F7I (k 1) and CF3I (k 2) have been measured using the resonance fluorescence of chlorine atoms in a flow reactor at 295 K: k 1 = (5.2 ± 0.3) × 10−12 cm3 molecule−1 s−1 and k 2 = (7.4 ± 0.6) × 10−13 cm3 molecule−1 s−1. No iodine atoms have been detected in the reaction products.  相似文献   

6.
Summary. The acylation at the 5′-OH group of the ribose-unit of vitamin B12 (cyanocobalamin) or of aquocobalamin with two conventional reagents gave mono-acylated B12-derivatives with good to very high selectivity. The site of the modification was deduced from spectral data of the products and was further supported by the crystal structure data of three such modified B12-derivatives. These three B12-derivatives were found to crystallize in the space group P212121, irrespective of the nature of the appendage. Acylation at 5′-OH has been used to protect (or block) this group in the context of functionalization of 2′-OH or elsewhere in the B12-molecule. Attachment of the bifunctional succinyl-unit has allowed the preparation of further modified derivatives of vitamin B12 and binding of B12-derivatives to biological carriers and other macromolecules. In aqueous solution, 5′-acylcobalamins turned out to be rather susceptible to hydrolytic loss of the acyl-functionality. Bernhard Kr?utler: In memoriam Prof. Karl Schl?gl  相似文献   

7.
The visible light irradiation of the [(η5-C6H7)Fe(η-C6H6)]+ cation (1) in acetonitrile resulted in the substitution of the benzene ligand to form the labile acetonitrile species [(η5-C6H7)Fe(MeCN)3]+ (2). The reaction of 1 with ButNC in MeCN produced the stable isonitrile complex [(η5-C6H7)Fe(ButNC)3]+ (3). The photochemical reaction of cation 1 with pentaphosphaferrocene Cp*Fe(η-cyclo-P5) afforded the triple-decker cation with the bridging pentaphospholyl ligand, [(η5-C6H7)Fe(μ-η:η-cyclo-P5)FeCp*]+ (4). The latter complex was also synthesized by the reaction of cation 2 with Cp*Fe(η-cyclo-P5). The structure of the complex [3]PF6 was established by X-ray diffraction. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2088–2091, November, 2007.  相似文献   

8.
New double mercury silver phosphide iodide Hg12Ag41P88I41 (1) was synthesized and its crystal structure was established. Compound 1 crystallizes in the cubic system. The characteristic feature of the crystal structure 1 is the presence of the anionic cage clusters P11 3−, which have been previously found in alkali metal compounds only. The well-ordered P11 3− clusters form a system of polyhedra, which encapsulate various disordered α-AgI-type fragments. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1882–1886, October, 2007.  相似文献   

9.
A highly sensitive high-performance liquid chromatographic method with fluorescence detection has been developed for determination of vitamin B1. Vitamin B1 was converted into a fluorescent compound by treatment with hydrogen peroxide–horseradish peroxidase and the derivative was subsequently analyzed by HPLC on a Waters Spherisorb ODS2 column (250 mm×4.6 mm ID, 5 μm) with 40:60 methanol–pH 8.5 acetate buffer solution as mobile phase and fluorescence detection at 440 nm (with excitation at 375 nm). The calibration graph was linear from 5.00×10−10 mol L−1 to 5.00×10−7 mol L−1 for vitamin B1 with a correlation coefficient of 0.9991 (n=9). The detection limit was 1.0×10−10 mol L−1. The method was successfully used for determination of vitamin B1 at pg mL−1 levels in microalgal fermentation media and seawater after solid-phase extraction. Recovery was from 89 to 110% and the relative standard deviation was in the range 1.1 to 4.3%.  相似文献   

10.
We have established and analyzed the sequences of phase transitions in synthesis of layered compounds in the AnBn–1O3n family ( \textA3\textII\textLnB3\textV\textO12 {\text{A}}_3^{\text{II}}{\text{LnB}}_3^{\text{V}}{{\text{O}}_{{12}}} (AII = Ba, Sr, Ln = La, Nd, BV = Nb, Ta) and La4Ti3O12 with n = 4) from coprecipitated hydroxocarbonate and hydroxide systems, including steps involving the formation, solid-phase reaction, or structural rearrangement of intermediates.  相似文献   

11.
A comparative analysis of the laser desorption/ionization of vitamin B12 by matrix-assisted laser desorption/ionization (MALDI) and desorption/ionization on porous silicon (DIOS) was carried out. The mass spectra obtained were interpreted and the pathways for ion formation and decomposition were established. The MALDI fragmentation of the positive vitamin B12 ions is more extensive than the DIOS fragmentation. The most extensive fragmentation was found using the MALDI method for negative vitamin B12 ions, which are lacking when using the DIOS method. __________ Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 43, No. 4, pp. 251–256, July–August, 2007.  相似文献   

12.
Heteropoly acid (HPA) H8(PW11TiO39)2xH2O (I) is synthesized by three different ways and studied by chemical analysis, potentiometric titration, mass-spectrometry, IR, 31P, 183W, and 17O NMR spectroscopy, thermogravimetry, and transmission electron microscopy. Anion I consists of two subparticles of the Keggin structure bridged by Ti-O-Ti. The dimeric anion exists in HPA aqueous solutions at [I] > 0.02 M. At pH > 0.6 it splits to a [PW11TiO40]5− monomer stable up to pH ∼ 6. When heated (150–400)°C, I splits into H3PW12O40 and, apparently, H3PW10Ti2O38 without phase separation. Thermolysis products are soluble and when dissolved in water turn again into I. Complete decomposition of I to oxides occurs at ∼450°C.  相似文献   

13.
Energy differences, ΔX s−t (X = E, H, and G) (ΔX s−t = X(singlet) − X(triplet)) between singlet (s) and triplet (t) states of C12H8M were calculated at B3LYP/6-311+G*. The DFT calculations indicated that the ΔG s−t between singlet (s) and triplet (t) states of C12H8M were increased from M = C to M = Pb. The ΔG s−t of C12H8M was compared with its analogue C4H4M through replacement of heavy atoms from M = C to M = Pb. Configurations of the electrons in orbitals (σ2 or π2) for the singlet state of C12H8M were discussed.  相似文献   

14.
The preparation and study of electrochemical properties of a graphite screen-printed electrode (SPE) modified with the GO/Fe3O4@SiO2 (GO is graphene oxide) nanocomposites are described. The morphologies of the GO/Fe3O4@SiO2 nanocomposites were examined by scanning electron microscopy. The electrochemical oxidation of vitamin B6 (pyridoxine) on SPE modified with the GO/Fe3O4@SiO2 nanocomposite was investigated by cyclic voltammetry, differential pulse voltammetry, and chronoamperometry. Under optimum conditions (pH 7.0), the vitamin B6 oxidation at the surface of the modified SPE occurs at a potential about 190 mV less positive than that at the unmodified SPE. A linear voltammetric response for vitamin B6 was obtained in the concentration range 1.0?10 6—9.0?10 4 mol L–1 with a detection limit of 5.2?10 7 mol L–1 using differential pulse voltammetry. The developed sensor was also successfully applied for determination of trace level of vitamin B6 in both the standard vitamin B6 sample and biological samples (urine).  相似文献   

15.
A fluorimetric method for the determination of vitamin B12 has been developed. The fluorescence emission was measured at λexem275/305 nm in phosphate buffer solution (pH 7.0), and the experimental variables and possible interference were studied. The linear calibration range was 1.000 ng/mL to 100.0 ng/mL with a correlation coefficient of 0.9994 and a detection limit of 0.1 ng/mL. The method is rapid, simple and highly sensitive. It was used to determine vitamin B12 in pharmaceutical preparations. The recovery was 96%–98% and the relative standard deviation was in the range of 1.8%–2.7%. The results agreed with those obtained by spectrophotometry. Received: 17 July 2000 / Revised: 4 September 2000 / Accepted: 7 September 2000  相似文献   

16.
One new metal – organic coordination framework formulated as [{Cu(4,4′-bipy)(CH3COO)2}·3H2O]n (1) (where 4,4′-bipy=4,4′-bipyridine) has been hydrothermally synthesised and characterised by elemental analysis, IR and electronic spectroscopy, variable temperature magnetic moment measurement and single crystal X-ray diffraction study. Single crystal X-ray analysis reveals that 1 is one dimensional polymeric compound in which acetate ligand shows both mono- and bidentate bonding mode, and 4,4′-bipy acts as bridging ligand which supports the formation of infinite chains. The global feature of the χ M T vs. T curve in 1 is characteristic of moderate antiferromagnetic interaction and the best fit parameters from 300 down to 2 K are found as J = −78.7 cm−1.  相似文献   

17.
Making use of a set of quantum chemistry methods, the harmonic potential surfaces of the ground state (S0(1 A g)) and the first (S1(1 B 3u)) excited state of pyrazine are investigated, and the electronic structures of the two states are characterized. In the present study, the conventional quantum mechanical method, taking account of the Born-Oppenheimer adiabatic approximation, is adopted to simulate the absorption spectrum of S1(1 B 3u) state of pyrazine. The assignment of main vibronic transitions is made for S1(1 B 3u) state. It is found that the spectral profile is mainly described by the Franck-Condon progression of totally symmetric mode ν6a. For the five totally symmetric modes, the present calculations show that the frequency differences between the ground and the S1(1 B 3u) state are small. Therefore the displaced harmonic oscillator approximation along with Franck-Condon transition is used to simulate S1(1 B 3u) absorption spectra. The distortion effect due to the so-called quadratic coupling is demonstrated to be unimportant for the absorption spectrum, except the coupling mode ν10a. The calculated S1(1 B 3u) absorption spectrum is in reasonable agreement with the experimental spectra. Supported by Taiwan National Science Council (Grant Nos. NSC 96-2113-M-009-021 and NSC 96-2811-M-009-023)  相似文献   

18.
The photoluminescence properties of xZnO–(100−x)SiO2 (x = 0, 5, 10, 20) containing 1% Eu2O3 prepared by a sol–gel method were systematically investigated. The results indicated that the relative proportion of f–f transitions to charge transfer (CT) absorption decreased with the increase of ZnO concentration. The intensity of 5D07FJ transitions of Eu3+ ions was enhanced with the increase of ZnO content due to local structure changes and decreased quantities of Eu3+ ions clusters. The results of fluorescence line narrow (FLN) spectra indicated that Eu3+ ions occupied one site in SiO2 glass and two sites in ZnO–SiO2 glasses. The second-order crystal field parameters were calculated. B20 and B22 for site 1 increased with excitation energy, while ones hardly changed for site 2.  相似文献   

19.
The ortho-metalated complex [Pd(x){κ 2 (C,N)-[C6H4CH2NRR′ (Y)}] (2a4a and 2b3b) was prepared by refluxing in benzene equimolecular amounts of Pd(OAc)2 and secondary benzylamine [a, EtNHCH2Ph; b, t-BuNHCH2Ph followed by addition of excess NaCl. The reaction of the complexes [Pd(x){κ 2 (C,N)-[C6H4CH2NRR′ (Y)}] (2a4a and 2b3b) with a stoichiometric amount of Ph3P=C(H)COC6H4-4-Z (Z = Br, Ph) (ZBPPY) (1:1 molar ratio), in THF at low temperature, gives the cationic derivatives [Pd(OC(Z-4-C6H4C=CHPPh3){κ 2 (C,N)-[C6H4CH2NRR′(Y)}] (5a9a, 4b6b, and 4b′6b′), in which the ylide ligand is O-coordinated to the Pd(II) center and trans to the ortho-metalated C(6)H(4) group, in an “end-on carbonyl”. Ortho-metallation, ylide O-coordination, and C-coordination in complexes (5a9a, 4b6b, and 4b′6b′) were characterized by elemental analysis as well as various spectroscopic techniques.  相似文献   

20.
A flow-through optosensor has been prepared for the sensitive and selective determination of pyridoxine (vitamin B6) in aqueous solutions. The sensor was developed in conjunction with a monochannel flow-injection analysis system with fluorimetric detection using Sephadex SP-C25 resin as an active sorbent substrate. This method of determination is carried out without any derivatization. The wavelengths of excitation and emission were 295 and 385 nm, respectively. When a HCl (10–3 mol L–1) / NaCl (3 × 10–2 mol L–1) solution is used as carrier solution, the sensor responds linearly in the measuring range of 5–200, 10–400 and 50–1800 ng mL–1 with detection limits of 0.33, 0.67, and 5.70 ng mL–1 for 2000, 1000 and 200 μL of sample volume, respectively. The relative standard deviation for ten independent determinations is less than 0.75% for 0.2 and 1.0 mL of sample volumes used, and 1.31% for 2.0 mL of sample volume used. The method was satisfactorily applied to the determination of vitamin B6 in pharmaceutical preparations. Received: 4 June 1998 / Revised: 16 July 1998 / Accepted: 6 August 1998  相似文献   

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