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1.
Ladislav Omelka Silvie Ondrášová Lothar Dunsch Andreas Petr Andrej Staško 《Monatshefte für Chemie / Chemical Monthly》2001,132(5):597-606
Summary. The oxidation of aniline and some derivatives of 1,2-phenylenediamine was performed by the system Pb(CH3COO)4—CF3COOH—CH2Cl2. An ESR investigation of the oxidized aniline confirmed the presence of secondary cation radical. Its structure was determined
by comparison of its ESR spectrum with those of cation radicals prepared from derivatives of 1,4-phenylenediamine. The oxidation
of 1,2-phenylenediamine and its derivatives leads to the formation of either primary or secondary cation radicals, the latter
having the character of substituted dihydrophenazinium cation radicals.
Received August 17, 2000. Accepted (revised) October 16, 2000 相似文献
2.
Alexander Konkin Frank Wendler Frank Meister Hans-Klaus Roth Albert Aganov Oliver Ambacher 《Cellulose (London, England)》2007,14(5):457-468
Degradation processes of N-methylmorpholine-N-oxide monohydrate (NMMO), cellulose and cellulose/NMMO solutions were studied by high performance liquid chromatography (HPLC)
and electron spin resonance (ESR) spectroscopy. Kinetics of radical accumulation processes under UV (λ = 248 nm) excimer laser
flash photolysis was investigated by ESR at 77 K. Beside radical products of cellulose generated and stabilized at low temperature,
radicals in NMMO and cellulose/NMMO solutions were studied for the first time in those systems and attributed to nitroxide
type radicals ∼CH2–NO•–CH2∼ and/or ∼CH2–NO•–CH3∼ at the first and methyl •CH3 and formyl •CHO radicals at the second step of the photo-induced reaction. Kinetic study of radicals revealed that formation and recombination
rates of radical reaction depend on cellulose concentration in cellulose/NMMO solutions and additional ingredients, e.g.,
Fe(II) and propyl gallate. HPLC measurements showed that the concentrations of ring degradation products, e.g., aminoethanol
and acetaldehyde, are determined by the composition of the cellulose/NMMO solution. Results based on HPLC are mainly maintained
by ESR that supports the assumption concerning a radical initiated ring-opening of NMMO. 相似文献
3.
Dong-Zhao Gao Dai-Zheng Liao Zong-Hui Jiang Shi-Ping Yan 《Transition Metal Chemistry》2008,33(1):107-112
Two hetero-spin metal–radical complexes [Cu(NIT2Py)2Cl] · ClO4 · H2O (
1
) and [Co(NIT2Py)2(H2O)(CH3OH)] · (ClO4)2
(
2
) (NIT2Py = 2-(2′-pyridinyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide), were synthesized and characterized structurally
and magnetically. The two complexes crystallize in mononuclear structures where two radical ligands coordinate to the metal
ion through the nitroxide oxygen atoms directly via the bidentate chelating mode. The magnetic measurements show that two
complexes exhibit strong antiferromagnetic interactions between the metal ions and the nitroxide radicals. 相似文献
4.
The geometries of acyclic and three-membered ring (nitroxide) H4C2NO radicals in their ground 2Π electronic states have been optimized completely at ab initio UHF and ROHF theoretical levels with the STO-3G and the 6-31G** basis sets. The optimizations favour the cyclic nitroxide
structure energetically. However ΔE(acyclic - cyclic) at the UHF and ROHF/6-31G** levels are only 3.2 and 1.9 kcal mol-1, respectively. Incomplete MP2/6-311G** optimizations support these results. The zero-point energy computed at the ROHF/6-31G**
level for the nitroxide radical is 2.5 kcal mol-1 higher than that for the acyclic structure, thus reversing the relative energies by 0.6 kcal mol-1. The energies of the two radical structures, relative to the sum of those for ethylene and NO, are very close to literature
values of the activation energies for the thermal, NO catalyzed geometrical isomerizations of olefins. Thus cyclic nitroxide
intermediates may play a role not only in the Hg 6(3P1) photosensitized, but also in the thermal, NO-catalyzed geometric isomerizations of olefins.
Paper dedicated to Professor Otto P. Strausz; presented in part at the 75th Canadian Chemical Congress and Exhibition, Edmonton,
May 31 – June 4, 1992. 相似文献
5.
A. V. Yakovenko L. Sorace E. A. Mikhalyova A. W. Addison V. V. Pavlishchuk 《Theoretical and Experimental Chemistry》2010,46(4):243-249
The temperature dependences of the magnetic susceptibilities for the complexes [Fe2III MIIO(p-NitPhCOO)6]∙MeCN (M = Co, Ni, p-NitPhCOO–= p-benzoatenitronyl nitroxide radical, MeCN = acetonitrile) revealed the existence of antiferromagnetic exchange coupling among
the metal ions in the trinuclear units, as well as between these units and the free radicals in the crystal lattices of the
complexes. 相似文献
6.
V. D. Sen N. A. Rukina V. V. Tkachev A. V. Pis'menskii L. M. Volkova S. A. Goncharova T. A. Raevskaya A. G. Tikhomirov L. B. Gorbacheva N. P. Konovalova 《Russian Chemical Bulletin》2000,49(9):1613-1619
Mixed-ligand platinum complexescis-PtII(R6NH2)(NH3)X2 andcis-PtII(R5NH2)(NH3)X2 (R6 is 2,2,6,6-tetramethyl-4-piperidyl-1-oxyl and R5 is 2,2,5,5-tetramethyl-3-pyrrolidinyl-1-oxyl) were synthesized by either the reaction of aminonitroxides RNH2 with Na[PtII(NH3)Cl2I] generatedin situ (for X2=ClI) or by replacement of the iodo-chloro ligands incis-Pt11(RNH2)(NH3)ClI by dichloro and oxalato ligands. The complexes obtained were characterized by elemental analysis and by IR, UV, and ESR
spectra. Forcis-Pt11(R5NH2)(NH3)Cl2, crystal and molecular structures were determined by X-ray diffraction analysis. Cisplatin accelerates autooxidation of methyl
linoleate and the platinum nitroxide complexes synthesized exhibit antioxidant properties. The rate of isolated DNA binding
with the new complexes is almost as high as that for cisplatin.cis-Pt11(R6NH2)(NH3)Cl2 exhibits the highest antitumor activity. The high antitumor activity of platinum nitroxide complexes shows that the possible
“radical component” is not a crucial factor in the cytotoxic action of cisplatin.
Published inIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1624–1630, September, 2000. 相似文献
7.
The magnetic coupling interactions of the nitronyl nitroxide radicals bound to diamagnetic (YIII) and paramagnetic (GdIII) rare earth ions in two model magnetic systems based on novel rare earth organic radical complexes Ln(hfac)3(NITPhOCH3)2 (Ln = YIII 1, GdIII 2; hafc = hexafluoroacetylacetonate; NITPhOCH3 = 4′-methoxyo-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide) have been investigated by density functional theory (DFT).
The magnetic coupling mechanisms were also explored from the viewpoint of molecular orbital and spin density populations.
DFT calculations show that the empty 4d-orbitals of YIII and 5d-orbitals of GdIII play an important role in the antiferromagnetic coupling between the two nitronyl nitroxide radical ligands, and that the
ferromagnetic coupling between the GdIII ion and the radical magnetic centers can be attributed to the nearly complete localization of the isotropic 4f-shell and singly occupied magnetic orbital (Π*) of the nitronyl nitroxide. 相似文献
8.
Bikshandarkoil R. Srinivasan Christian Näther Sunder N. Dhuri Wolfgang Bensch 《Monatshefte für Chemie / Chemical Monthly》2006,137(4):397-411
Summary. Four new organic ammonium tetrathiotungstates (N–Me–enH2)[WS4] (1), (N,N′-dm-1,3-pnH2)[WS4] (2), (1,4-bnH2)[WS4] (3), and (mipaH)2[WS4] (4), (N–Me–enH2 = N-methylethylenediammonium, N,N′-dm-1,3-pnH2 = N,N′-dimethyl-1,3-propanediammonium, 1,4-bnH2 = 1,4-butanediammonium, and mipaH = monoisopropylammonium) were synthesized by the base promoted cation exchange reaction and characterized by elemental analysis,
infrared, Raman, UV-Vis and 1H NMR spectroscopy as well as single crystal X-ray crystallography. The structures of 1–4 consist of [WS4]2− tetrahedra which are linked to the organic ammonium cations via N–H⋯S hydrogen bonding. The strength and number of the S⋯H
interactions affect the W–S bond lengths as evidenced by distinct short and long W–S bonds. The IR spectra exhibit splitting
of the W–S vibrations, which can be attributed to the distortion of the [WS4]2− tetrahedron. From a comparative study of several known tetrathiotungstates it is observed that a difference of more than
0.033 ? between the longest and shortest W–S bonds in a tetrathiotungstate will result in the splitting of the asymmetric
stretching vibration of the W–S bond. 相似文献
9.
Kinetic data for the oxidation of glutathione (reduced, GSH), cysteine, glycine and glutamic acid by colloidal manganese dioxide,
(MnO2)
n
are reported. Colloidal MnO2, oxidized glutathione to disulphide (glutathione, oxidized), was reduced to manganese (II). Glycine and glutamic acid (structural
units of glutathione) are not oxidized by colloidal MnO2, but the other structural unit, cysteine, is also oxidized by the same oxidant under similar experimental conditions. This
is interpreted in terms of the rate-determining colloidal MnO2-S bonded intermediate. The reactivity of GSH towards colloidal MnO2 is very much higher than cysteine. Kinetics of oxidation of GSH and cysteine by colloidal MnO2 were performed spectrophotometrically as a function of [GSH], [cysteine], colloidal [(MnO2)
n
], [HClO4], temperature and trapping agents sodium fluoride and manganese (II) (reduction product of colloidal MnO2). The purpose of this work was to study the role of –NH2, –COOH, –SH groups present in the carbon chain of the above amino acids. It was found that the reactivity of –SH group is
higher than –NH2 and –COOH groups. The mechanisms, involving a colloidal MnO2 complex with GSH and cysteine, are proposed. The complexes decompose in a rate-determining step, leading to the formation
of free radical and manganese (III), which is also an intermediate. The dimerization of radicals takes place in a subsequent
fast step to yield the products. 相似文献
10.
Jun Young Lee Chongchan Lee Yong Min Lee Kuk Young Cho Jang Wook Choi Jung-Ki Park 《Journal of Solid State Electrochemistry》2012,16(2):657-663
We report a novel combination of organic sensitizer and redox mediator in the electrolyte for dye-sensitized solar cells (DSSCs):
a thiophene dye and nitroxide radicals. Nitroxide radicals and their oxidized counterparts of oxoammonium cations show robust
reversible redox reactions, thus supporting robust DSSC operations. Moreover, their redox potentials (E
1/2) and thus open-circuit voltages (V
OC) can be tuned further by attached functional groups. Optical and electrochemical characterization reveal that these new combinations
exhibit enhanced V
OC and power conversion efficiencies compared to the existing iodine mediator (I−/I3−) due to the increased V
OC. Also, the selection of the sensitizer–redox mediator turns out to be critical in the overall cell performance. Indeed, the
typical ruthenium dye loses its light absorption capability when it is operated in conjunction with the nitroxide radicals. 相似文献
11.
Jun-Hua Dong Hong-Yan Dou Yue-Fa Gong Cheng-Xue Zhao 《Research on Chemical Intermediates》2006,32(2):137-144
Radical cations of 1,4-dialkoxybenzenes 1 and 2 and alkyl 1,4-dialkoxybenzenes 3–9 generated in oxidation of the parent donors by perfluorodi[1-(2-fluorosulfonyl)ethoxy]propionyl peroxide 10 at −40°C and pentafluorobenzoyl peroxide 11 at 15°C were observed by ESR. Radical cation 6+˙, generated in other oxidation systems, i.e., Ce(SO4)2/THF, NH4/OAc and (NH4)2S2O8/HOAc, has also been investigated. Based on ESR observation and products analysis, an electron-transfer mechanism of the oxidation
reaction is proposed and the influencing factors on hyperfine splitting constants of the radical cations are discussed. 相似文献
12.
Electrochemical acetoxylation of 1,4-dimethoxybenzene during amperostatic electrolysis in an undivided cell at Pt electrodes
in MeCN or MeOH solutions containing Et4NOAc gives 2,5-dimethoxyphenyl acetate if AcOH or CH2Cl2 co-solvent has been added in a concentration of ≥50%. The reaction mechanism includes a nucleophilic attack of AcO− ion on the ipso-position of 1,4-dimethoxybenzene radical cation. The process efficiency depends on factors that determine the stability and
reactivity of the intermediate 1,4-dimethoxy-1-acetoxyarenonium cation.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1534–1538, July, 2005. 相似文献
13.
Samih A. Halawy 《Monatshefte für Chemie / Chemical Monthly》2003,134(3):371-380
Summary. Unpromoted cobalt molybdate was prepared from Co(NO3)2·6H2O and (NH4)6Mo7O24·4H2O, then calcined between 350 and 600°C for 5 h. K2O (10 w%), as a promoter, was added to the calcined sample at 350°C from two different sources (i.e. KOH and KNO3) and was subjected to further calcination at 350°C for 5 h. The catalytic activity of unpromoted catalysts towards the vapour
phase decomposition of CH3COOH was greatly influenced by the increase in the calcination temperature. This is attributed to the diminution of both S
BET and their dual acidic–basic characters. The promoted sample from the KOH source was found to be the most active of the catalysts
studied. This is due to its high population of both acidic–basic surface sites and the formation of two new phases. XRD and
FTIR analyses of the used catalysts, after the decomposition reaction of acetic acid, showed a remarkable change in its structure
compared with the parent samples.
E-mail: shalawy99@yahoo.com
Received May 8, 2002; accepted (revised) July 9, 2002 相似文献
14.
A novel heterospin one-dimensional (1-D) chain complex containing both Cu(II) and nitroxide radical ligands, {[Cu(tcph)(H2O)4][Cu(tcph)(NIT3Py)2]·2H2O}
n
(1) (H2tcph = tetrachloro-phthalic acid, NIT3Py = 2-(3′-pyridyl)-4,4,5,5-tetramethyl-imidazoline-1-oxyl-3-oxide), has been synthesized
and structurally characterized. The structure consists of neutral chains of copper(II) ions bridged by tcph and coordinated
alternatively by nitroxide radicals as spin branches and solvated water as co-ligand. The magnetic data were fitted using
an approximate theoretical model based on population analysis to obtain the coupling parameter values of J
Cu2-Rad = 22.4 cm−1 and J′Cu1-Cu2 = −2.4 cm−1, indicating the intramolecular ferromagnetic interaction between Cu(II) and NIT3Py and weak antiferromagnetic interaction
between Cu1 and Cu2 linked by tcph. 相似文献
15.
Maurizio Casarin Andrea Vittadini Ulrich Schubert 《Monatshefte für Chemie / Chemical Monthly》2007,138(12):1217-1223
Summary. DFT calculations were carried out on Ti2(OCH3)8 (NH2CH3)2 and Ti2(OCH3)8(NH3)2, which are model compounds for the previously isolated amine adducts Ti2(OR)8(NH2
R′)2. The calculations show that the Ti–N bond strength is weak; however, coordination of the amine to the metal center is supported
by a N–H···O hydrogen bond of the amine with the neighboring alkoxo ligand. The Ti–N interaction is purely σ in nature, while
the Ti–O interactions include both σ and π contributions. The lowest unoccupied molecular orbitals are mainly localized on
Ti t2g-like orbitals. 相似文献
16.
The N—H bond dissociation energy (D
NH) in the 4-anilinodiphenylaminyl radical formed from N,N-diphenyl-1,4-phenylenediamine was experimentally determined and calculated by the quantum-chemical method. The experimental D
NH value was found from the enthalpy of the reaction of N,N-diphenyl-1,4-benzoquinonediimine with 4-hydroxydiphenylamine taking into account the bond dissociation energies in 4-hydroxydiphenylamine and its aminyl and phenoxyl radicals, which were determined by the intersecting parabolas method from the kinetic data. The quantum-chemical calculations of D
NH used several semiempirical methods by the MOPAC program and the ab initio and DFT methods by the GAUSSIAN 94/98 program. The D
NH values, which were closest to the experimental values, were obtained by the B3LYP/6-31+G* method. The results of quantum-chemical calculations of the N—H and O—H bond dissociation energies in 4-hydroxydiphenylamine and its radicals are presented.Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1549–1554, August, 2004. 相似文献
17.
The electrochemical amination of anisole in 4.0–6.0 M H2SO4 solutions containing CH3COOH and small amounts of water is studied with the use of the Ti(IV)/Ti(III)-NH2OH system. Under these conditions, the products of radical substitution are para- and ortho-anisidines. Their total current efficiency and yield by hydroxylamine are 82.0% at a complete conversion of the source of
amine radicals. Owing to the chain mechanism, the electrochemical process is terminated upon consumption of no more than 0.5
electrons per NH2OH molecule. At a small charge passed through the electrolyte, the anisidines current efficiency can exceed 380%. 相似文献
18.
V. R. Gorelik V. F. Tarasov S. R. Shakirov E. G. Bagryanskaya 《Russian Chemical Bulletin》2008,57(7):1416-1427
The multispin systems consisting of spin-correlated radical pairs (SCRPs) and stable nitroxide radicals, localized in micelles
of sodium dodecyl sulfate (SDS), were studied by ESR and pulse laser photolysis techniques. In all the systems studied, the
stable nitroxide radicals exert no effect on the shape of the ESR spectra of the SCRPs (in particular, on the shape of their
antiphase structure) and on the decay kinetics of the ESR signal of the SCRPs. In the SDS micelles, the electron spin polarization
transfer from the nonequilibrium electron spin states of the molecular triplets (SCRP precursors) is the most efficient mechanism
of generation of the electron spin polarization in nitroxide radicals. The experimental data also show that the nitroxide
radicals and SCRP radicals are most probably distributed uniformly in the micellar phase.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1390–1401, July, 2008. 相似文献
19.
A. E. Gorodetskii R. Kh. Zalavutdinov V. L. Bukhovets S. P. Vnukov A. P. Zakharov 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2008,82(13):2340-2345
The stream technique was used to comparatively analyze the characteristics of the deposition of a-C:H films from methyl radicals
transferred by a carrier gas CH4/C2H
y
/H2 (y = 2, 4, 6) in a quartz tube with cylindrical insets made of Cu, Ni, Fe, W, Si, and stainless steel (SS), initial and coated
with thin Pd or Rh films, over the temperature range 300–1000 K. The deposition of methyl was fully suppressed in a tube section
heated to 380–800 K with all the insets specified. During further mixture movement outside this section in the tube with a
decreasing wall temperature, carbon deposition resumed. The most effective catalyst of the hydrogenation reaction was stainless
steel. Radicals and unsaturated hydrocarbons capable of polymerization at 300–400 K were fully removed from the carrier gas
flow (CH4/C2H
y
/H2) after several hundreds of collisions with the surface of SS heated to 420–470 K. The possibility of creating an SS recombination
filter for hydrocarbon radicals (the performance of radical hydrogenation reactions) transferred by a CH4/C2H
y
/H2 laminar flow was demonstrated. The deposition of a thin Pd film (∼10 nm) on steel did not increase the effectiveness of the
surface with respect to radical recombination reactions. At the same time, Rh films increased the catalytic effectiveness
of the surface of SS with respect to the hydrogenation of methyl and unsaturated hydrocarbons (380–420 K). The data obtained
were used to select temperature conditions and mutual arrangement for the construction elements of an ITER diverter made of
tungsten and stainless steel. 相似文献
20.
Mohammed M. Ghoneim Ibrahim S. El-Hallag Kamal Y. El-Baradie Hanaa S. El-Desoky Mona A. El-Attar 《Monatshefte für Chemie / Chemical Monthly》2006,137(3):285-299
Summary. The electrochemical behavior of some hydrazones derived from 6-chloro-2-hydrazinopyridine in the Britton-Robinson universal buffer of pH 2–11 containing 35% ethanol was investigated at the mercury electrode using dc-polarography, controlled-potential coulometry,
and cyclic voltammetry techniques. The examined hydrazones were reduced in solutions of pH < 9 in a single 4-electron diffusion-controlled irreversible step corresponding to both the saturation of –N=C< double bond
and cleavage of the –HN–NH– single bond of the hydrazone molecule via the consumption of two electrons for each center. Whereas the starting compound, 6-chloro-2-hydrazinopyridine, was reduced
in a single 2-electron diffusion-controlled irreversible step corresponding to cleavage of its –NH–NH2 single bond. The mechanistic pathway of the electrode reaction of the studied compounds was elucidated and discussed. The
pKa values of the examined hydrazones and the stoichiometry of their complexes in solution with some transition metal ions were
determined spectrophotometrically. The dissociation constants and the thermodynamic parameters of the investigated hydrazones,
and the stability constants of their metal complexes in solution were determined potentiometrically. 相似文献