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1.
A sensitive spectrophotometric method for the determination of copper(II) based on a ternary complex with chromal blue G, a triphenylmethane reagent in the presence of cetyltrimethylammonium chloride, is described. The sensitivity of color reaction between copper and chromal blue G has been greatly increased by the sensitizing action of cetyltrimethylammonium chloride, a cationic surfactant. The color development of the ternary complex can be utilized in the highly sensitive spectrophotometric determination of copper. The molar absorptivity of the binary complex between copper and chromal blue G ε630nm = 9.56 × 103liters · mol−1 · cm−1 is enchanced on ternary complex formation to ε542 nm = 4.78 × 104liters · mol−1 · cm−1. The ternary complex gave a maximal absorbance at 542 nm in the pH range 9.8–11. Beer's law is obeyed up to at least 1.2 ppm of copper. The maximal absorbance of the ternary complex was found to develop within 5 min and then it remains constant for several hours. The formation constant of the ternary complex is calculated to be 8.6 × 1010 under these conditions.  相似文献   

2.
The kinetics of the reaction of the CH3CHBr, CHBr2 or CDBr2 radicals, R, with HBr have been investigated in a temperature-controlled tubular reactor coupled to a photoionization mass spectrometer. The CH3CHBr (or CHBr2 or CDBr2) radical was produced homogeneously in the reactor by a pulsed 248 nm exciplex laser photolysis of CH3CHBr2 (or CHBr3 or CDBr3). The decay of R was monitored as a function of HBr concentration under pseudo-first-order conditions to determine the rate constants as a function of temperature. The reactions were studied separately from 253 to 344 K (CH3CHBr + HBr) and from 288 to 477 K (CHBr2 + HBr) and in these temperature ranges the rate constants determined were fitted to an Arrhenius expression (error limits stated are 1σ + Student’s t values, units in cm3 molecule−1 s−1, no error limits for the third reaction): k(CH3CHBr + HBr) = (1.7 ± 1.2) × 10−13 exp[+ (5.1 ± 1.9) kJ mol−1/RT], k(CHBr2 + HBr) = (2.5 ± 1.2) × 10−13 exp[−(4.04 ± 1.14) kJ mol−1/RT] and k(CDBr2 + HBr) = 1.6 × 10−13 exp(−2.1 kJ mol−1/RT). The energy barriers of the reverse reactions were taken from the literature. The enthalpy of formation values of the CH3CHBr and CHBr2 radicals and an experimental entropy value at 298 K for the CH3CHBr radical were obtained using a second-law method. The result for the entropy value for the CH3CHBr radical is 305 ± 9 J K−1 mol−1. The results for the enthalpy of formation values at 298 K are (in kJ mol−1): 133.4 ± 3.4 (CH3CHBr) and 199.1 ± 2.7 (CHBr2), and for α-C–H bond dissociation energies of analogous compounds are (in kJ mol−1): 415.0 ± 2.7 (CH3CH2Br) and 412.6 ± 2.7 (CH2Br2), respectively.  相似文献   

3.
The photochemical, photophysical and photobiological studies of a mixture containing cis-[Ru(H-dcbpy)2(Cl)(NO)] (H2-dcbpy = 4,4′-dicarboxy-2,2′-bipyridine) and Na4[Tb(TsPc)(acac)] (TsPc = tetrasulfonated phthalocyanines; acac = acetylacetone), a system capable of improving photodynamic therapy (PDT), were accomplished. cis-[Ru(H-dcbpy)2(Cl)(NO)] was obtained from cis-[Ru(H2-dcbpy)2Cl2]·2H2O, whereas Na4[Tb(TsPc)(acac)] was obtained by reacting phthalocyanine with terbium acetylacetonate. The UV–Vis spectrum of cis-[Ru(H-dcbpy)2(Cl)(NO)] displays a band in the region of 305 nm (λmax in 0.1 mol L−1 HCl)(π–π*) and a shoulder at 323 nm (MLCT), while the UV–Vis spectrum of Na4[Tb(TsPc)(acac)] presents the typical phthalocyanine bands at 342 nm (Soret λmax in H2O) and 642, 682 (Q bands). The cis-[Ru(H-dcbpy)2(Cl)(NO)] FTIR spectrum displays a band at 1932 cm−1 (Ru–NO+). The cyclic voltammogram of the cis-[Ru(H-dcbpy)2(Cl)(NO)] complex in aqueous solution presented peaks at E = 0.10 V (NO+/0) and E = −0.50 V (NO0/−) versus Ag/AgCl. The NO concentration and 1O2 quantum yield for light irradiation in the λ > 550 nm region were measured as [NO] = 1.21 ± 0.14 μmol L−1 and øOS = 0.41, respectively. The amount of released NO seems to be dependent on oxygen concentration, once the NO concentration measured in aerated condition was 1.51 ± 0.11 μmol L−1 The photochemical pathway of the cis-[Ru(H-dcbpy)2(Cl)(NO)]/Na4[Tb(TsPc)(acac)] mixture could be attributed to a photoinduced electron transfer process. The cytotoxic assays of cis-[Ru(H-dcbpy-)2(Cl)(NO)] and of the mixture carried out with B16F10 cells show a decrease in cell viability to 80% in the dark and to 20% under light irradiation. Our results document that the simultaneous production of NO and 1O2 could improve PDT and be useful in cancer treatment.  相似文献   

4.
EPR studies are carried out on Cr3+ ions doped in d-gluconic acid monohydrate (C6H12O7·H2O) single crystals at 77 K. From the observed EPR spectra, the spin Hamiltonian parameters g, |D| and |E| are measured to be 1.9919, 349 (×10−4) cm−1 and 113 (×10−4) cm−1, respectively. The optical absorption of the crystal is also studied at room temperature. From the observed band positions, the cubic crystal field splitting parameter Dq (2052 cm−1) and the Racah interelectronic repulsion parameter B (653 cm−1) are evaluated. From the correlation of EPR and optical data the nature of bonding of Cr3+ ion with its ligands is discussed.  相似文献   

5.
The spectrofluorometric study was made of the complex 1,4-diaminoanthraquinone-Ca in aqueous sulfuric mediums [λmax,ex = 410 nm; λmax,em = 580 nm; 50% H2O; stable for at least 4 hr; range temperature OPTIMUM = 20–35 °C; [R]optimum = 2 × 10−4M; stoichiometry 2:1 (fluorescent complex) and 1:1 (no fluorescent complex)]. A new method for the spectrofluorometric determination of Ca traces is proposed for concentrations between 150 and 400 ppb. The relative error and the interferences of the method have been investigated.  相似文献   

6.
The α-tocopheroxyl radical was generated voltammetrically by one-electron oxidation of the α-tocopherol anion (r1/2=−0.73 V versus Ag|Ag+) that was prepared by reacting α-tocopherol with Et4NOH in acetonitrile (with Bu4NPF6 as the supporting electrolyte). Cyclic voltammograms recorded at variable scan rates (0.05–10 V s−1), temperatures (−20 to 20°C) and concentrations (0.5–10 mM) were modelled using digital simulation techniques to determine the rate of bimolecular self-reaction of α-tocopheroxyl radicals. The k values were calculated to be 3×103 l mol−1 s−1 at 20°C, 2×103 l mol−1 s−1 at 0°C and 1.2×103 l mol−1 s−1 at −20°C. In situ electrochemical-EPR experiments performed at a channel electrode confirmed the existence of the α-tocopheroxyl radical.  相似文献   

7.
The coordination of nitric oxide (NO) to cobalt(II) phthalocyanine (CoPc) in dimethyl sulphoxide (DMSO) has been studied. CoPc coordinates with NO in a 1:1 ratio, forming a CoPc(NO) species. The IR band observed at 1680 cm−1 is assigned to the coordinated NO. In the presence of excess NO, pseudo first order kinetics were followed. The observed rate constant, kf, was determined to be 15.0±0.3 dm−3 mol−1 s−1 and the equilibrium constant was K=5.4±0.4×104dm3 mol−1. Solution or adsorbed CoPc catalyses the reduction of NO. The products of reduction include NH3 and NH2OH.  相似文献   

8.
The production and reactions of vinyl radicals and hydrogen atoms from the photolysis of vinyl iodide (C2H3I) at 193 nm have been examined employing laser photolysis coupled to kinetic-absorption spectroscopic and gas chromatographic product analysis techniques. The time history of vinyl radicals in the presence of hydrogen atoms was monitored using the 1,3-butadiene (the vinyl radical combination product) absorption at 210 nm. By employing kinetic modeling procedures a rate constant of 1.8 × 10?10 cm2 molecule?1 s?1 for the reaction C2H3 + H has been determined at 298 K and 27 KPa (200 torr) pressure. A detailed error analysis for determination of the C2H3 + H reaction rate constant, the initial C2H3 and H concentrations are performed. A combined uncertainty of ±0.43 × 10?10 cm2 molecule?1 s?1 for the above measured rate constant has been evaluated by combining the contribution of the random errors and the systematic errors (biases) due to uncertainties of each known parameter used in the modeling. © 1995 John Wiley & Sons, Inc.  相似文献   

9.
The C5–C10 cyclolakyl radicals have a weak light absorption in the 240–300 nm wavelength range that is due to Rydberg transition to the 3s orbital. The extinction coefficients at 250 nm are in the range of 350–900 mol–1 dm3 cm–1. At this wavelength for the C6–C10 radicals a local maximum appears. The radical decay obeys second order kinetics. The kinetic characteristics of the cyclic and linear radicals are generally similar, indicating that the rings are flexible and can easily overcome steric constraints in the termination process. Both the light absorption and decay characteristics of the cyclopentyl radical are somewhat different from those of the other radicals that are attributed to the special co-planar arrangement.  相似文献   

10.
Layered crystalline zirconium phenylphosphonate, Zr(O3PC6H5)2, changed its interlamellar distance of 1481 pm after intercalation of n-alkylmonoamines, CH3---(CH2)n---NH2 (n=0–6). The infrared spectra of the precursor host and the corresponding intercalated compounds presented vibrations associated with PO3 groups in the 1163–1039 cm−1 range and additional bands related to C---H stretching bands in the 2950–2850 cm−1 interval were observed after amine insertion. The thermogravimetric curves showed a mass loss assigned to the phenyl group; however, the amine intercalated fraction was not quantitatively determined. A peak in the 31P NMR spectrum centered at −6 ppm for the host was observed. The surface area was 42.0±0.2 m2 g−1 and the scanning electron micrograph gave images consistent with lamellar structural features. The layered compound was calorimetrically titrated with amine in ethanol, requiring three independent operations: (i) titration of matrix with amine, (ii) matrix salvation, and (iii) dilution of the amine solution. From those thermal effects the variation in enthalpy was calculated as: −41±1.00,−33.28±0.50,−34.40±0.80,−10.40±0.40,−12.40±0.42,−16.10±0.08 and −7.0±0.04 kJ mol−1, for n=0–6, respectively. The exothermic enthalpic values reflected a favorable energetic process of amine–host intercalation in ethanol. The negative Gibbs free energy results supported the spontaneity of all these intercalation reactions. The positive favorable entropic values, as carbon chain size increased, are in agreement with the free solvent molecules in the medium, as the amines are progressively bonded to the crystalline lamellar inorganic matrix at the solid/liquid interface.  相似文献   

11.
To evaluate the contribution of local pulsed heating of light-absorbing microregions to biochemical activity, irradiation of Escherichia coli was carried out using femtosecond laser pulses (λ = 620 nm, τp=3 × 10−13 s, fp = 0.5 Hz, Ep = 1.1 × 10−3J cm−2, Iav = 5.5 × 10−4 W cm−2, Ip = 109 W cm−2) and continuous wave (CW) laser radiation (λ = 632.8 nm, I = 1.3 W cm−2). The irradiation dose required to produce a similar biological effect (a 160%–190% increase in the clonogenic activity of the irradiated cells compared with the non-irradiated controls) is a factor of about 103 lower for pulsed radiation than for CW radiation (3.3 × 10−1 and 7.8 × 102 J cm−2 respectively). The minimum size of the microregions transiently heated on irradiation with femtosecond laser pulses is estimated to be about 10 Å, which corresponds to the size of the chromophores of hypothetical primary photoacceptors—respiratory chain components.  相似文献   

12.
New 3,4:9,10-dibenzo-2,11-dihydroxy-1,12-bispiperazine-5,8-dioxododecane complexes [C24H36N4O6Cu] (1), [C24H32N4O4Zn] (2) have been synthesized and characterized by elemental analysis, IR, NMR, Mass, EPR, UV–vis spectroscopy and molar conductance measurements. The complexes are non-ionic in nature and possess octahedral geometry around Cu2+, Zn2+ central metal ions. The binding studies of 1 and 2 with calf thymus DNA (CT-DNA) were investigated by UV–vis, fluorescence, cyclic voltammetery and viscosity measurements. The calculated binding constant Kb for 1 and 2 obtained from UV–vis absorption studies was 7.6 × 103 M−1, 80.8 × 104 M−1, respectively. The intrinsic binding constants were also estimated to be 7.0 × 104 M−1 and 7.53 × 105 M−1 for 1 and 2, respectively by using emission titrations. These experimental results suggest that complexes are groove binders and interact to CT-DNA with different affinities. Both the complexes in presence and absence of CT-DNA show quasireversible wave corresponding to CuII/CuI and ZnII/ZnI redox couple. The changes in E1/2, ΔE, Ipa/Ipc ascertain the interaction of 1 and 2 with CT-DNA. Further, decrease in viscosity of CT-DNA with increasing concentration of complexes was observed. In vitro, antimicrobial activity against fungi A. brassicicola, A. niger and bacteria E. coli, P. aeruginosa of complexes were carried out, which indicate that complex 2 is more active against both fungal and bacterial strains as shown by % inhibition data.  相似文献   

13.
The action spectrum of tetracene photooxygenation was measured in air-saturated carbon tetrachloride in the wavelength range of 1220–1290 nm using a wavelength-tunable forsterite laser. The data show that the photoreaction occurs due to laser excitation of the transition in oxygen molecules. The molar absorption coefficient (1273) and the cross section of light absorption (σ1273) corresponding to the spectral maximum of this transition were calculated from the observed photoreaction rates. The obtained values ε1273 = 0.003 M−1 cm−1 and σ1273 = 10−23 cm2 (±20%) reasonably correlate with those extrapolated from the high-pressure oxygen absorption spectra.  相似文献   

14.
Ionophoric, extraction, acidic and hydrophobic properties of 3-(4-tolylazo)phenylboronic acid (TAPBA) were studied. Determined Kd value equals to 36±2, pKa equals to 8.6±0.5. TAPBA extracts dobutamine from water into chloroform and transports it across a bulk chloroform membrane. The recovery is 83% (pH=7.5), the transport rate – (6.5±0.5)×10−7 mol/h. 1H and 13C NMR data confirm the formation of an 1:1 complex between arylboronic acid and catecholamine. TAPBA was used as electrode-active component of plasticized membrane electrodes with cationic and anionic responses to catecholamines and phenolic acids, respectively. For the diethyl sebacate-plasticized membrane, a slope of electrode function to dobutamine is 56±2 mV/decade; the detection limit is 1.3×10−5 mol/l; the linear range – 5×10−5–1×10−2 mol/l; the working pH-range – 4.8–7.6; the response time – 5–10 s. ISE gives incomplete cationic function to less lipophilic catecholamines. The membrane with cationic additive shows an anionic response to caffeic acid in wide pH range.  相似文献   

15.
5-Aminotetrazole trinitrophloroglucinolate ((ATZ)TNPG) was prepared and characterized by elemental analysis and FT-IR spectroscopy. The crystal structure was determined by X-ray diffraction analysis and it belonged to orthorhombic system and Pbca space group with a=0.6624(2) nm, b=1.7933(4) nm, c=2.3117(5) nm, V=2.7458(9) nm3, Z=4, and Dc=1.849 g·cm−3. The molecular formula was confirmed to be (ATZ)TNPG·2H2O. 5-Aminotetrazole cation (ATZ+) and trinitrophloroglucinol anion (TNPG) were linked into 2-D layers along b-axis and c-axis by hydrogen bonds. Then the layers were linked along a-axis by hydrogen bonds between the water molecules belonging to different layers. The thermal decomposition mechanism of the compound was studied by differential scanning calorimetry (DSC), thermogravimetry-thermogravimetric analysis (TG-DTG), and Fourier transform-infrared (FT-IR) spectroscopy techniques. Under nitrogen atmosphere with a heating rate of 10 °C·min−1, the compound experienced one endothermic process with peak temperature of 76 °C and one exothermal process with peak temperature of 203 °C. The former was confirmed to be a dehydrate process. The latter was the decomposition of TNPG and ATZ+ in the compound. The exothermic enthalpy change of this process was −212.10 kJ·mol−1. The kinetic parameter calculation from Kissinger's method were, E=132.1 kJ·mol−1, ln(A/s−1)=12.54 with r=0.9990, and the calculation results from Ozawa-Doyle's method were, E=133.1 kJ·mol−1 with r=0.9992.  相似文献   

16.
A sensitive extraction-spectrophotometric method of the determination of osmium, taking advantage of the ion-associate of the chloride osmium anion with brilliant green has been developed. The complex is extracted from aqueous phase with a mixture of C6H5Cl + CCl4 (3 + 1). Molar absorptivity () at 640 nm is 1.95 × 105 liters mol−1cm−1 (specific ABSORPTIVITY = 1.03). The relative standard deviation is 1–3%. The mole ratio of Os:BG in the complex is 1:3. Platinum metals interfere with the determination of osmium. The determination can be highly selective after preliminary separation of osmium by distillation as OsO4.  相似文献   

17.
Using spectrophotometric methods, the protopysis constant of the 5.ClDMPAP reagent (pKa1 = −0.19; pKa2 = 1.97; pKa3 = 11.98) and the stability constant of its vanadic complex (6.0 ± 0.11) × 1014 were determined. A high-sensitivity spectrophotometric method was developed to determine V(V) using 0.1–1.2 ppm and pH = 3.8. ε586 = 55,300 ± 400 liters · mol−1 · cm−1. A study on the most important interferences and the way to eliminate them was carried out. The method can be applied to the determination of the element in steels and ferrovanadiums.  相似文献   

18.
Room temperature rate coefficients and product distributions are reported for the reactions initiated in D2O with dications of the alkaline-earth metals Mg, Ca, Sr and Ba. The measurements were performed with a selected-ion flow tube (SIFT) tandem mass spectrometer and electrospray ionization (ESI). Mg2+ reacts with water by a fast electron transfer leading to charge separation with a rate coefficient of 1.4 × 10−9 cm3 molecule−1 s−1. Ca2+ reacts with D2O in a first step to form the adduct Ca2+(D2O), with an effective bimolecular rate coefficient of 2.3 × 10−11 cm3 molecule−1 s−1, which then undergoes rapid charge separation by deuteron transfer to form CaOD+ and D3O+ in a second step with k = 7.9 × 10−10 cm3 molecule−1 s−1. The CaOD+ ion reacts further by clustering up to five more D2O molecules. Sr2+ clusters up to eight D2O molecules and Ba2+ up to seven D2O molecules, with the first addition of D2O being rate determining in each case and the last addition being distinctly slower, as might be expected from a transition in the occupation of the added water molecules from an inner to an outer hydration shell.  相似文献   

19.
The ultraviolet absorption spectrum of CF3CFClO2 and the kinetics of the self reactions of CF3CFCl and CF3CFClO2 radicals and the reactions of CF3CFClO2 with NO and NO2 have been studied in the gas phase at 295 K by pulse radiolysis/transient UV absorption spectroscopy. The UV absorption cross section of CF3CFCl radicals was measured to be (1.78 ± 0.22) × 10?18 cm2 molecule?1 at 220 nm. The UV spectrum of CF3CFClO2 radicals was quantified from 220 nm to 290 nm. The absorption cross section at 250 nm was determined to be (1.67 ± 0.21) × 10?18 cm2 molecule?1. The rate constants for the self reactions of CF3CFCl and CF3CFClO2 radicals were (2.6 ± 0.4) × 10?12 cm3 molecule?1 s?1 and (2.6 ± 0.5) × 10?12 cm3 molecule?1 s?1, respectively. The reactivity of CF3CFClO2 radicals towards NO and NO2 was determined to (1.5 ± 0.6) × 10?11 cm3 molecule?1 s?1 and (5.9 ± 0.5) × 10?12 cm3 molecule?1 s?1, respectively. Finally, the rate constant for the reaction of F atoms with CF3CFClH was determined to (8 ± 2) × 10?13 cm3 molecule?1 s?1. Results are discussed in the context of the atmospheric chemistry of HCFC-124, CF3CFClH. © 1994 John Wiley & Sons, Inc.  相似文献   

20.
The spectra and kinetic behavior of solvated electrons (esol) in alkyl ammonium ionic liquids (ILs), i.e. N,N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium bis(trifluoromethanesulfonyl)imide (DEMMA-TFSI), N,N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium tetrafluoroborate (DEMMA-BF4), N,N,N-trimethyl-N-propylammonium bis(trifluoromethanesulfonyl)imide (TMPA-TFSI), N-methyl-N-propylpiperidinium bis(trifluoromethanesulfonyl)imide (PP13-TFSI), N-methyl-N-propylpyrrolidinium bis(trifluoromethanesulfonyl)imide (P13-TFSI), and N-methyl-N-butylpyrrolidinium bis(trifluoromethanesulfonyl)imide (P14-TFSI) were investigated by the pulse radiolysis method. The esol in each of the ammonium ILs has an absorption peak at 1100 nm, with molar absorption coefficients of 1.5–2.3×104 dm3 mol−1 cm−1. The esol decayed by first order with a rate constant of 1.4–6.4×106 s−1. The reaction rate constant of the solvated electron with pyrene (Py) was 1.5–3.5×108 dm3 mol−1 s−1 in the various ILs. These values were about one order of magnitude higher than the diffusion-controlled limits calculated from measured viscosities. The radiolytic yields (G-value) of the esol were 0.8–1.7×10−7 mol J−1. The formation rate constant of esol in DEMMA-TFSI was 3.9×1010 s−1. The dry electron (edry) in DEMMA-TFSI reacts with Py with a rate constant of 7.9×1011 dm3 mol−1 s−1, three orders of magnitude higher than that of the esol reactions. The G-value of the esol in the picosecond time region is 1.2×10−7 mol J−1. The capture of edry by scavengers was found to be very fast in ILs.  相似文献   

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