共查询到20条相似文献,搜索用时 31 毫秒
1.
S. V. Kukharenko L. N. Novikova V. V. Strelets N. A. Ustynyuk A. I. Yarmolenko 《Russian Chemical Bulletin》1994,43(10):1710-1714
The electrochemical reduction of (6-C13H9)Mn(CO)3 (1, where C13H9—fluorenyl) has been studied in THF by cyclic voltammetry and preparative controlled potential electrolysis. One-electron reduction of1 to the corresponding 19-electron radical anion1
.– is accompanied by the haptotropic isomerization of the latter to the radical anion (5-C13H9)Mn(CO)3
.– (2
.–), which is oxidized at the electrode to neutral complex2. Electron-transfer induced isomerization1 2 is an electrocatalytic process with current efficiency of 600%, which can be also promoted by catalytic amounts (20%) of the chemical reducing agents (benzophenone radical anion or sodium amalgam). If the reaction is chemically induced, the radical anion2
.– is oxidized by initial complex1; as a result the electron-transfer induced isomerization1 2 proceeds by a chain mechanism. The influence of the electronic state (18e–/19e–) of 6- and 5-fluorenyl complexes on the position of the equilibrium of the intra-ring haptotropic isomerization reaction is discussed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1805–1809, October, 1994.This work was supported in part by the Russian Foundation for Basic Research (Project No. 93-03-05209) and the International Science Foundation (Grant No. REV 000). 相似文献
2.
Malinovskii S. T. Bologa O. A. Coropceanu E. B. Luboradzki R. Gerbeleu N. V. 《Russian Journal of Coordination Chemistry》2004,30(5):339-345
Crystal structures of [Co(MH)2(Thio)2][BF4] · H2O (I) and [Co(DH)2(NH3)2][BF4] (II), where MH– is H3C–C(NOH)–C(NO–)–H and DH– is H3C–C(NOH)–C(NO–)–CH3, were determined by X-ray diffraction. The crystals are monoclinic, space group C2/c, unit cell parameters (for I and II, respectively): a = 22.018(2) Å, b = 7.943(1) Å, c = 11.681(1) Å, = 92.68(1)° and a = 21.436(2) Å, b = 6.400(2) Å, c = 12.389(2) Å, = 113.13(1)°. In both cases, the Co(III) coordination polyhedron is a centrosymmetrical trans-octahedron, N4S2 for I and N6 for II. In the crystals of I and II, the complex cations and the outer-sphere [BF4]– anions (and the crystal water molecules in I) form elaborate hydrogen bonding system. 相似文献
3.
A. Fratiello V. Kubo-Anderson E. Bolanos R. D. Perrigan L. Saenz S. M. Stoll 《Journal of solution chemistry》1996,25(11):1071-1082
A direct, low-temperature hydrogen-1, carbon-13, and nitrogen-15 nuclear magnetic resonance study of lutetium(III)-isothiocyanate complex formation in aqueous solvent mixtures has been completed. At –100°C to –120°C in water-acetone-Freon mixtures, ligand exchange is slowed sufficiently to permit the observation of separate1H,13C, and15N NMR signals for coordinated and free water and isothiocyanate ions. In the13C and15N spectra of NCS–, resonance signals for five complexes are observed over the range of concentrations studied. The13C chemical shifts of complexed NCS– varied from –0.5 ppm to –3 ppm from that of free anion. For the same complexes, the15N chemical shifts from free anion were about –11 ppm to –15 ppm. The magnitude and sign of the15N chemical shifts identified the nitrogen atom as the binding site in NCS–. The concentration dependence of the13C and15N signal areas, and estimates of the fraction of anion bound at each NCS–:Lu3+ mole ratio, were consistent with the formation of [(H2O)5Lu(NCS)]2+ through [(H2O)Lu(NCS)5]2–. Although proton and/or ligand exchange and the resulting bulk-coordinated signal overlap prevented accurate hydration number measurements, a good qualitative correlation of the water1H NMR spectral results with those of13C and15N was possible. 相似文献
4.
Teresa Mancilla Percino Roxana Magaly Flores Ancona Marisol Lpez Martínez 《Polyhedron》2009,28(13):2771-2775
A new, mild and friendly method for the synthesis of (N → B) phenyl[N-alkyliminodiacetate-O,O′,N]boranes 2–7 is reported. All compounds were identified by 1H, 11B, 13C NMR and their high resolution mass spectra (HRMS) are reported. The structure of the compounds 2, 4 and 5 were established by single crystal X-ray. Compounds 2 and 4 crystallized with two independent molecules 2A, 2B and 4A, 4B, respectively in the asymmetric unit. These molecular structures established the bicyclic structure showing a N → B bond length of 1.666 (2) Å for 2A, 1.675 (2) Å for 2B, 1.675 (3) Å for 4A, 1.663 (3) Å for 4B and 1.679 (2) Å for 5, as well as different torsion angles of the junction, 28.70 (2)° (C11–B1–N6–C17) for 2A, 21.50 (2)° (C11a–B1a–N6a–C17a) for 2B, 25.76 (0.26)° (C11–B1–N6–C17) for 4A, 21.96 (0.28)° (C11a–B1a–N6a–C17a) for 4B and −29.22 (0.20)° (C5–N1–B1–C13) for 5. 相似文献
5.
R. I. Khusnutdinov D. K. Galeev A. I. Malikov U. M. Dzhemilev O. M. Nefedov 《Russian Chemical Bulletin》1994,43(11):1871-1872
endo,exo-Hexacyclo[9.2.02,10.03,8.04,6.05,9]tetradec-12-ene (1) undergoes cyclocodimerization with quadricyclane (Q) in the presence of the Pd(PPh3)4 complex to giveexo,exo,endo,exo-decacyclo[9.9.1.02,10.03,8.04,6.05,9.012,20.013,18.014,16.015,19]heneicosane (2) andendo,exo,endo,exo-decacyclo[9.9.1.02,10.03,8.04,6.05,9.012,20.013,18.014,16.015,19]heneicosane (3) in a ratio of 10 7 (yield up to 26 %). Simultaneously, homocyclotrimerization of Q occurs to give three known C21 hydrocarbons (4–6). The yields of compounds2 and3 and the selectivity of the process depend considerably on the reaction conditions and the molar ratio of1 and Q. Compounds2 and3 that were obtained were characterized by13C NMR spectra.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 1983–1985, November, 1994. 相似文献
6.
Eberhard Hohaus 《Monatshefte für Chemie / Chemical Monthly》1980,111(4):863-875
The i.r., u. v.,1H n.m.r.,13C n.m.r., and11B n.m.r. spectra of several substituted diphenylboron chelates derived from salicylaldehyde azomethines were compared with respect to the influence of the amine substituentR. O–B–N-6-ring constitution of the chelates29–32 [R=OH, NH2, NHC6H5, N(CH3)2] can be deduced from the spectra.
Als 3. Mitt. gilt:F. Umland undE. Hohaus mit Beiträgen vonW. Riepe, K. Brodte, C. Schleyerbach undD. Szonn. Untersuchungen über borhaltige Ringsysteme vom Chelattyp. Forschungsbericht des Landes Nordrhein-Westfalen Nr. 2538. Opladen: Westdeutscher Verlag. 1976. 相似文献
7.
A. I. Yarmolenko S. V. Kukharenko L. N. Novikova V. V. Strelets 《Russian Chemical Bulletin》1995,44(7):1300-1305
It has been shown by cyclic voltammetry in THF within the –90 to 40 °C temperature range that fluorenyl (5-9-R-C13H8)Mn(CO)3 complexes (R=But (3) and Ph (4)) undergo two-electron reduction to form allyl type [(3-9-R-C13H8)Mn(CO)3]2– dianions as final products. At low temperatures complexes3 and4 are reduced in two one-electron steps according to the EEC-scheme. The first step is reversible and corresponds to the formation of 19-radical anions 3–. and 4–.. TheE
0 values for redox pairs3
0/–. and4
0/–. are –1.88 and –1.73 V, respectively. The further reduction of radical anions3
–. and4
–. at more negative potentials is accompanied by fast 5 3 haptocoordination of the fluorenyl ligand to form 18-dianions [(3-9-R-C13H8)Mn(CO)3]2–. These dianions obtained by the reduction of complexes3 and4 by the radical anion of pyrene are stable at –80 °C and are characterized by their IR spectra. At room temperature the 5 3 hapticity change is a fast and reversible process occurring at the step of 19-radical anions3
–. and4
–. and leading to the electron deficient 17-species [(3-9-R-C13H8)Mn(CO)3]–., which are reduced easier than the initial complexes. As a result, complexes3 and4 are reduced to the corresponding dianions [(3-9-R-C13H8)Mn(CO)3]2– at room temperature in one reversible two-electron step according to the ECE-scheme. Reactivities of 19e–-species of the isomeric 5- and 6-fluorenylmanganesetricarbonyl complexes are compared.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1347–1353, July, 1995.The work was financially supported by the Russian Foundation for Basic Research (Project No. 93-03-05209) and the International Science Foundation (Grant No. REV 000). 相似文献
8.
Summary Oxazolin-2-ylidene-malononitriles3a–d, obtainable from thioketenaminals and -halogen-ketones, react with primary and secondary amines to afford 2,4-diamino-pyrroles5a–h. Mercaptobenzen as nucleophilic agent gives the 4-amino-2-phenylthio-pyrrole5j. Analogously, cyano-(3,5-diphenyl-3H-oxazol-2-ylidene)-acetic acid methyl esters were prepared as intermediates for the synthesis of 2-amino-4-oxo-pyrrolines10a–d. The isomeric 4-amino-2-oxo-pyrrolines13a–d can be obtained from 4-amino-2-methoxy-pyrroles, which serves as proof for the position of substituents. The structures were investigated by1H and13C NMR spectroscopy.
Neue Synthesen von 2,4-Diaminopyrrolen und Aminopyrrolinonen
Zusammenfassung Die Oxazolin-2-yliden-malononitrile3a–d. die aus Thioketenaminalen und -Halogenketonen erhalten wurden, reagieren mit primären und sekundären Aminen zu den 2,4-Diaminopyrrolen5a–h. Mercaptobenzol als nukleophiles Reagens liefert 4-Amino-2-phenylthiopyrrol (5j). Analog wurden Cyan-(3,5-diphenyl-3H-oxazol-2-yliden)-essigsäuremethylester als Zwischenprodukte für die Synthese der 2-Amino-4-oxo-pyrroline10a–d hergestellt. Die isomeren 4-Amino-2-oxo-pyrroline13a–d können aus den 4-Amino-2-methoxy-pyrrolen11a,b erhalten werden, was als Nachweis für die Position der Substituenten dient. Die Verbindungen wurden1H- und13C NMR-spektroskopisch untersucht.相似文献
9.
Thermal reaction of [Ru2(CO)6(μ-PFu2)(μ-η1,η2-Fu)] (Fu=2-furyl) with (9-anthracenyl)diphenylphosphine (AnPPh2) produces a novel diruthenium complex [Ru2(CO)5(μ-PFu2)(μ-η1,η1,η2-C14H8PPh2)] (1) in good yield whereas the corresponding reaction between [(μ-H)4Ru4(CO)12] and AnPPh2 gives [HRu(CO)3(PPh2C14H8)][(μ-H)4Ru4(CO)11(AnPPh2)] (2). Both compounds 1 and 2 were fully characterized by spectroscopic methods and their X-ray crystal structures were determined. For 1, initial coordination of the PPh2 functionality at the Ru atom is accompanied by cyclometalation of the anthracenyl ring to form a Ru–C σ bond together with concomitant formation of a π bond to the adjacent Ru center and loss of the furyl ligand. The formation of 2 involves the cleavage of two Ru–Ru bonds, and the making of a Ru–P bond, followed by orthometalation of the anthracenyl ring. The optical absorption and emission spectra of 1 were recorded and the results were correlated to the DFT calculations.Dedicated to Professor F. Albert Cotton on the occasion of his 75th birthday. 相似文献
10.
S. P. Zhdanov L. S. Kosheleva T. I. Titova M. A. Shubaeva 《Russian Chemical Bulletin》1993,42(4):619-623
The variations in the structure of deep-level calcinated NH4Na-Y zeolite (68 % NH4
+, Si/Al = 2.56) at 873 K (stage I of the hydrothermal dealumination) as a result of ammonation and subsequent calcination in water vapor at 973 and 1023 K (stageII) were studied using the IR spectra of zeolite framework vibrations. It was shown that ammonation of the product of stageI promotes the formation of linear disiloxane bonds and extra-framework =AlVI-OH species identified by absorption at 482, 1196 cm–1, and 524, 612, 829 cm–1. The ammonation is also accompanied by an increase in the excessive negative framework charge (ENFC), which is manifested in the high-frequency (HF) shift of the bands that have maxima in thev
as
(TO4) region and equals 10 cm–1, and also by a decrease in the unit cell parameter (a
0) by 0.14 Å. The decrease in both the ENFC anda
0 for the products of stageII, v
as
(TO4) = 10–20 cm–1 and a
0 = 0.07–0.14 Å, is due to the formation of nonlinear disiloxane bonds and non-framework aluminum hydroxide species identified by the absorption bands at 478, 1173 cm–1 and 530, 615, 835 cm–1.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 660–664, April, 1993. 相似文献
11.
REDOR technique was applied to natural abundance 13C nuclei coupled to a singly labeled 15N nucleus to determine the 13C, 15N interatomic distances simultaneously in crystalline ammonium [15N]
-glutamate monohydrate (1). Consequently, the interatomic C–N distances between 15N and 13C=O, 13Cα, 13Cβ, 13Cγ, and 13Cδ carbon nuclei for 1 were determined with a precision of ±0.15 Å, after the experimental conditions such as the location of samples in the rotor, length of π pulse etc. were carefully optimized. 13C-REDOR factors for three spin system, (ΔS/S0)CN1N2, and the sum of two isolated 2-spin system, (ΔS/S0)*=(ΔS/S0)CN1+(ΔS/S0)CN2, were further evaluated by the REDOR measurements on isotopically diluted 1 in a controlled manner. Subsequently, the intra- and intermolecular C–N distances were separated by searching the minima in the contour map of root mean square deviation (RMSD) between the theoretically and experimentally obtained (ΔS/S0)* values against two interatomic distances, rC–N1 and rC–N2. When the intramolecular C–N distance (rC–N1) of the particular carbon nucleus is substantially shorter than the intermolecular one (rC–N2), C–N distances within a single molecule were obtained with an accuracy of ±0.06 Å as in the cases of C=O, Cα and Cβ carbon nuclei. C–N distances between the molecule in question and the nearest neighboring molecules can be also obtained, although accuracy was lower. On the contrary, it was difficult to determine the interatomic distances in the same molecule when the intermolecular dipolar contribution is larger than the intramolecular one as in the case of Cδ carbon nucleus. 相似文献
12.
K. Strijckmans C. Vandecasteele M. Esprit 《Fresenius' Journal of Analytical Chemistry》1980,303(2):106-110
Summary The determination of boron, carbon, nitrogen and oxygen in nickel by charged particle activation using the reactions 10B(d, n)11C, 12C(d, n)13N, 14N(p, )11C and 16O(3He, p)18F is studied. The interference of 11B(p, n)11C with the 14N(p, )11C reaction is taken into account. 11C, 13N and 18F are separated by oxygen combustion followed by trapping of 11CO2 in NaOH and by steam distillation of 13NH3 and of H2Si18F6, respectively. The results obtained were 0.129±0.035 g g–1 for boron, 86.4±8.3 g g–1 for carbon, 1.077±0.037 g g–1 for nitrogen and 8.91±1.00 g g–1 for oxygen. The results for nitrogen and oxygen agreed satisfactorily with those of other analytical methods.Grateful acknowledgement is made to Prof. J. Hoste for his interest shown in this work, to J. Pauwels (B.C.M.N., Geel) for providing the samples, to B. F. Schmitt (Bundesanstalt für Materialprüfung, Berlin) for helpful information concerning the radiochemical separation of 11C and to the NFWO and the IIKW for financial support. 相似文献
13.
Zeliha Hayvali Mustafa Hayvali Zeynel Kiliç Tuncer Hökelek Edwin Weber 《Journal of inclusion phenomena and macrocyclic chemistry》2003,45(3-4):285-294
Condensation reactions between 4'-formyl-5'-hydroxybenzo-15-crown-5and 2-aminopyridine, 2-amino-6-methylpyridine, 2-amino-4-methylpyridine or2-(aminomethyl)furan yielded the new laterally functionalized crown ethers1–4. The crown compounds 1–3 form crystalline 1:1 (Na+:ligand) complexes 1a–3a with sodium perchlorate. Ligands and complexes have been characterized by elemental analyses, IR, UV-Vis, 1H-, 13C-NMR and mass spectra. The tautomeric equilibria (phenol-imine, O...H–N and keto-amine, O...H–N forms) have been systematically studied by using UV-Vis absorption spectra. The spectra of the ligands 1–4 and complexes 1a–3a were recorded in polar, non-polar, acidic, and basic media. In solutions of polar solvents, tautomeric interconversion of the Schiff base into the keto-amine form has been observed. A crystal structure [monoclinic, space group P21/c,a = 14.292(2), b = 9.449(6), c = 16.059(2) Å, = 114.20(1)°,V = 1978.4(13) Å3, Z = 4 and Dx = 1.314 g cm-3] shows that compound 4 is in the form of phenol-imine in solid state. There is a strong intramolecular [O–H...N 1.78(6), O...N 2.581(7), O–H 0.89(6) Å and N...H–O 148.4(5)°] hydrogen bond between the phenolic oxygen and imine nitrogen atoms. The C=N imine bond reveals a trans planar (1E) configuration. The molecules stack in columns parallel to the a/c plane of the unit cell. 相似文献
14.
C. A. Strydom E. M. Groenewald J. H. Potgieter 《Journal of Thermal Analysis and Calorimetry》1997,49(3):1501-1507
Using a heating rate of 2°C min–1, CaS reacts with oxygen in air from 700°C to form CaSO4, with a complete conversion at 1100°C. Synthesis of CaS from the reaction between CaSO4 containing compounds and carbon compounds in air would not be possible, as the carbon reacts from 600°C with oxygen in the air to give CO2. Heating stoichiometric amounts of carbon and pure CaSO4, synthetic gypsum or phosphogypsum in a nitrogen atmosphere, results in the formation of CaS from 850°C. Using a heating rate of 10°C min–1, the formation of CaS is completed at 1080°C. Addition of 5% Fe2O3 as a catalyst lowers the starting temperature of the reaction to 750°C. Activation energy values at different fraction reaction values () differ between 340 and 400 kJ mol–1. The relationship between the activation energy values and conversion () indicates that the reaction proceeds via multiple steps. 相似文献
15.
Yu. V. Tomilov E. V. Shulishov A. B. Kostitsyn O. M. Nefedov 《Russian Chemical Bulletin》1994,43(4):612-618
1-Pyrazolines1 and2 obtained by 1,3-dipolar cycloaddition of diazocyclopropane to norbornene or deltacyclene undergo dediazotization at 410–450°C to give a mixture of strained hydrocarbons, namely, spirocyclopropane-1,3'-tricyclo[3.2.1.02,4]octane (4) or spiro{cyclopropane-1,4'-pentacyclo[4.4.0.02,8.03,5.07,9]decane} (6) and isomeric tricyclo[5.2.1.02,5]dec-5-enes (5) or pentacyclo[6.4.0.02,10.03,6.09,11]dec-6-enes (7) in a 30–70% overall yield. An increase in temperature favors the isomerization of spiro hydrocarbons4 and6 to the respective unsaturated hydrocarbons5 and7. The latter undergo cyclopropanation with diazomethane in the presence of Pd(acac)2 or (PhO)3P · CuCl to afford polycyclanes9a,b or10a,b containing a spiro[2.3]hexane moiety condensed at thecis-1,4 position. Unsaturated 1-pyrazoline3 obtained from diazocyclopropane and norbornadiene decomposes at 330–370°C with elimination of cyclopentadiene to give 3(5)-vinylpyrazole in a yield up to 75%.Some of the results reported in this paper have been presented at the VIIIth European Symposium on organic chemistry (Barcelona, August–September 1993),cf. Ref. 1.Translated fromIzyestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 662–667, April, 1994.This study was financially supported by the Russian Fund for Fundamental Research (grant 94-03-08902). 相似文献
16.
Rabindra N. Roy James J. Gibbons Guilio LaCross Jr. Charles W. Krueger 《Journal of solution chemistry》1976,5(5):333-343
The two thermodynamic dissociation constants of glycine at 11 temperatures from 5 to 55°C in 50 mass % methanol-water mixed solvent have been determined from precise emf measurements with hydrogen-silver bromide electrodes in cells without liquid junction. The first acidic dissociation constant (K
1)for the process HG+H++G± is expressed as a function ofT(oK) by the equation pK
1 = 2043.5/T – 9.6504 + 0.019308T. At 25°C, pK
1is 2.961 in the mixed solvent, as compared with 2.350 in water, with H°=1497 cal-mole–1, G°=4038 cal-mole–1, S°=–8.52 cal-°K–1-mole–1, and C
p
o
=–53 cal-°K–1-mole–1. The second acidic dissociation constant (K
2)for the process G±H++G– over the temperature range studied is given by the equation pK
2 = 3627.1/T – 7.2371 + 0.015587T. At 25°C, pK
2is 9.578 in MeOH–H2O as compared with 9.780 in water, whereas H° is 10,257 cal-mole–1, G° is 13,063 cal-mole–1, S° is –9.41 cal-°K–1-mole–1, and C
p
o
is –43 cal-°K–1-mole–1. The protonated glycine becomes weaker in 50 mass % methanol-water, whereas the second dissociation process becomes stronger despite the lower dielectric constant of the mixed solvent (=56.3 at 25°C). 相似文献
17.
The title compound was obtained by reduction of diethyl (ferrocenylmethyl)malonate with lithium aluminium hydride in diethyl ether. The structure of this novel ferrocene derivative was assigned by means of elemental analysis, IR, [1H]NMR, and [13C]NMR spectroscopy. The structure was also confirmed by a single crystal X-ray study. The compound crystallizes in monoclinic P21/a space group with unit cell dimensions: a = 9.7360(6), b = 27.040(5), c = 14.767(3) Å, = 103.835(6)°, V = 3774.8(11) Å3, Z = 12. The asymmetric unit contains three crystallographically independent molecules. In the ferrocenyl moieties, the Fe–C bond distance values are in the range 2.006(5)—2.051(3) Å and C–C distances in the range 1.366(7)–1.425(4) Å. The cyclopentadienyl rings in each of the molecules are mutually twisted by about 13° from the eclipsed conformation. The hydroxyl groups are involved in the intermolecular O–H...O hydrogen bond formation with O-O distances in the range 2.686(3)–2.801(4) Å forming infinite two-dimensional network in a [0 0 1] plane. The crystal structure is additionally stabilized by C–H-O weak intermolecular hydrogen bonds. 相似文献
18.
A. S. Rozenberg E. I. Aleksandrova G. I. Dzhardimalieva N. V. Kir'yakov P. E. Chizhov V. I. Petinov A. D. Pomogailo 《Russian Chemical Bulletin》1995,44(5):858-866
Thermal transformations (at 340 to 390 °C) of coprecipitates of iron and cobalt acrylates, [Fe3O(CH2CHCOO)6OH][Co(CH2CHCOO)2]2.4 (1) and [Fe3O(CH2CHCOO)6OH][Co(CH2CHCOO)2]1.5·3H2O (2), are studied. The dependence of the degree of gas evolution () on time is described by the equation () wherek
1=2.3 · 1012 · exp[–49500/(RT)] s–1,k
2=6.0 · 106 · exp[–33000/(RT)] s–1 andk
1=2.6 · 1012 · exp[–49000/(RT)] s–1,k
2=6.6 · 105 · exp[–30000/(RT)] s–1 for cocrystallizates1 and2, respectively. The coefficient 1 decreases as the temperature increases. The value of 1 for compound1 is higher than that for compound2. The composition of products of the transformations of1 and2 are studied. The main solid state products of the decomposition are nanometer-sized particles of cobalt ferrite, CoFe2O4, with a narrow size distribution stabilized by the polymeric matrix. The thermal transformations of cocrystallizates1 and2 include dehydration, thermal decomposition, copolymerization in the solid state, and decarboxylation of the metallocarboxylate groups of the polymer. The effect of the ratio between the Fe clusters and the Co-containing fragments on the process of thermal transformation is analyzed.For Part 40, seeRuss. Chem. Bull., 1994,43, 2020.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 885–893, May, 1995.The authors are grateful to A. N. Titkov for optical microscopic and electron microscopic studies. 相似文献
19.
Yu Liu Jian-Rong Han Yan-Li Zhao Heng-Yi Zhang Zhong-Yu Duan 《Journal of inclusion phenomena and macrocyclic chemistry》2005,51(3-4):191-198
Two new selenacrown ethers, i.e., N,N′-dimethyl-1,11-diaza-4,8,14,18,-tetraselenacycloicosane (1) and 7,11-diseleno-2,3,15,16,-dibenzo-1,4,14,17,20,23-hexaoxacyclopentacosane (2), have been synthesized and characterized by elemental analysis and UV, and 1H-NMR spectroscopy. An X-ray crystallographic structure was obtained for 1. UV-spectrophotometric titrations have been performed in CCl4 solution at 25–50 °C to obtain the complex stability constants (Ks) and the thermodynamic parameters (ΔH0 and TΔS0) for the stoichiometric 1:1 complexation of [60]-fullerene (C60) with the crown ethers 1–4. The obtained Ks values together with that reported for dicyclohexano-24-crown-8 (5) reveal that, the more the heteroatom numbers in crown ether ring are, and the larger the cavity sizes of crown ethers are, the higher theKsvalues for complexation with C60 are. Thermodynamically, the complexation of C60 with 1–5 is absolutely enthalpy-driven in CCl4, while the complex stability is governed by the entropy term. 相似文献
20.
Q. Zini 《Fresenius' Journal of Analytical Chemistry》1992,344(7-8):322-325
Summary A sensitive spectrofluorimetric method is based on the complexation of Al with the dye Mordant Black 17 or Calcon (CI 15705). The complex solution in n-propyl alcohol (1.5×10–4 mol/l) is mixed (5:20) with 1 mol/l acetic acid — sodium acetate buffer (pH 4.8) and maintained at 40°C for 60 min. The fluorescence intensity is measured at Ex=565 nm, Em=610 nm: The calibration curve for Al was found to be linear in the range 0 to 60 ng×ml–1 with a standard deviation of =1.5 and an Al detection limit of 3 ng×ml–1. The interferences due to more than 40 ions were investigated; the presence of Fe3+, Cr3+, Co2+, Cu2+, Ti4+, VO2+, ZrO2+, WO
4
2–
, MoO
4
2–
, CrO
4
2–
and particularly F–, must be avoided or masked during the determination of Al. The sample of silicon/silicon dioxide was treated with a mixture of conc. HF and HNO3 (2:1), followed by digestion and distillation at 90°C to eliminate the matrix as fluorosilicic acid. A small residue of AlF3 was decomposed with HClO4. In SiO2 anodized layers (25–250 g) the minimum detection of Al was estimated to be 1018 At×cm–3, in monocrystalline silicon (25–250 mg) 1016 At×cm–3. The method can also be employed to determine the presence of Al in the residues by distillation of a small quantity (5–10g) of many solvents or reagent solutions.
Presented at: IX. Congresso Nazionale — Div Chim Anal (S.C.I.) Ferrara 1990 相似文献