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1.
Dijana Šimkūnaitė Emilija Ivaškevič Ignas Valsiūnas Aleksandras Kaliničenko Antanas Steponavičius 《Journal of Solid State Electrochemistry》2008,12(3):225-236
The early stages of Cu electrodeposition onto a GC electrode were investigated in 0.5 M H2SO4 + 0.01 M CuSO4 solution without or with H2SeO3 when a molar concentration ratio [Cu(II)]/[Se(IV)] was 1.104 to 2.102. The H2SeO3 solution in 0.5 M H2SO4 was also used. The electrochemical techniques such as cyclic voltammetry and chronoamperometry and structural investigation
using ex situ AFM were applied to study the nucleation and growth of Cu onto a GC electrode. Chronoamperometric results were
shown to follow an instantaneous 3D nucleation and diffusion-controlled growth model by Scharifker and Hills. The values of
number of Cu nuclei N and average nuclei radius r
av were calculated. It was shown that, in the presence of H2SeO3 in amounts of 0.001 to 0.005 mM, N increases and r
av decreases. At higher concentrations of the additive, the changes of these parameters with the deposition potential E
dep were shown to be somewhat more complex. The dependences of N and r
av on the concentration of H2SeO3 in different regions of Cu overpotentials were also revealed. 相似文献
2.
G. Giester 《Monatshefte für Chemie / Chemical Monthly》1994,125(11):1223-1228
Summary The compound RbFe(SeO4)2 was prepared hydrothermally by reaction of Rb2CO3 and FeC2O4·2H2O with H2O and H2SeO4 at 490 K. Single crystal X-ray methods revealed isotypy with KAl(SO4)2. RbFe(SeO4)2 crystallizes in space group P321;Z=1;a=5.005(1)Å,c=8.548(2) Å,V=185.4 Å3; 781 unique data up to 80 °2;R,R
w
=0.045, 0.042. The structure is best described as sheets of [Fe(SeO4)2]– parallel (001), interconnected by Rb+. FeO6 trigonal prims and SeO4 tetrahedra have bond lengths of 1.99 Å and 1.63 Å, respectively. The Rb atom is [6 + 6] coordinated with Rb-O distances of 3.04 Å and 3.48 Å.
Die Kristallstruktur des wasserfreien Alauns RbFe3+(SeO4)2
Zusammenfassung Die Verbindung RbFe(SeO4)2 wurde hydrothermal dargestellt durch Reaktion von Rb2CO3 und FeC2O4·2H2O mit H2O und H2SeO4 bei 490K. Einkristallröntgenmethoden belegten die Isotypie mit KAl(SO4)2 RbFe(SeO4)2 kristallisiert in der Raumgruppe P321;Z=1;a=5.005(1) Å,c=8.548(2) Å,V=185.4 Å3; 781 unabhängige Daten bis 80 °2;R,R w =0.045, 0.042. Die Struktur läßt sich am besten als Schichten von [Fe(SeO4)2]– parallel (001) beschreiben, die durch Rb+ verbunden sind. FeO6 trigonale Prismen und SeO4 Tetraeder weisen Bindungslängen von 1.99 Å bzw. 1.63 Å auf. Das Rb-Atom ist [6+6] koordiniert mit Rb-O Abständen von 3.04 Å und 3.48 Å.相似文献
3.
Manfred Wildner 《Monatshefte für Chemie / Chemical Monthly》1991,122(8-9):585-594
Summary The crystal structures of the new, hydrothermally synthesized, isotypic compounds Co3(SeO3)3·H2O and Ni3(SeO3)3·H2O were determined by direct and Fourier methods and refined toR
w=0.023, 0.032 using single crystal X-ray data up to sin/=0.81 Å–1 [space group P
,a=8.102 (2), 7.986 (3) Å;b=8.219 (2), 8.133 (3) Å;c=8.572 (2), 8.422 (3) Å, =69.15 (1), 69.50 (1)°; =62.88 (1), 62.50 (1)°; =67.23 (1), 67.64 (1)°;Z=2]. The structures are built up from [Me
5(SeO3)6·2H2O]2– sheets containing three crystallographically different types of octahedrally coordinatedMe
2+ and trigonal pyramidal coordinated Se4+ atoms, respectively. These sheets are linked only by a fourth type ofMe
2+[6] atom. All coordination polyhedra deviate significantly from their ideal shapes, bond lengths within the extremly distortedMe(4)O6 polyhedra range from 1.983 (2) Å to 2.403 (2) Å in Co3(SeO3)3·H2O and from 1.987 (4) Å to 2.301 (3) Å in the Ni compound, O-Se-O bond angles were found between 92.8 (2)° and 104.9 (1)°. Hydrogen bond lengths are 2.802 (3)Å and 2.600 (4)Å in the Co compound, and 2.762 (6) Å and 2.561 (6) Å in Ni3(SeO3)3·H2O. The latter is one of the shortest known hydrogen bonds donated by a water molecule.
Die Kristallstrukturen von Co3(SeO3)3·H2O und Ni3(SeO3)3·H2O, zwei neue isotype Verbindungen
Zusammenfassung Die Kristallstrukturen der neuen, hydrothermal synthetisierten, isotypen Verbindungen Co3(SeO3)3·H2O und Ni3(SeO3)3·H2O wurden mit direkten und Fourier-Methoden bestimmt und unter Verwendung von Einkristallröntgendaten bis sin/=0.81 Å–1 aufR w-Werte von 0.023, 0.032 verfeinert [Raumgruppe P ,a=8.102 (2), 7.986 (3) Å;b=8.219 (2), 8.133 (3) Å;c=8.572 (2), 8.422 (3) Å, =69.15 (1), 69.50 (1)°; =62.88 (1), 62.50 (1)°; =67.23 (1), 67.64 (1)°;Z=2]. Die Strukturen werden von [Me 5(SeO3)6·2H2O]2– Schichten aufgebaut, die je drei kristallographisch unterschiedliche Arten von oktaedrisch koordiniertenMe 2+ und trigonal pyramidal koordinierten Se4+ Atomen enthalten. Diese Schichten sind nur durch eine vierte Art vonMe 2+[6] Atomen verknüpft. Alle Koordinationspolyeder weichen deutlich von ihren Idealformen ab, Bindungslängen in den extrem verzerrtenMe(4)O6 Polyedern variieren zwischen 1.983 (2) Å und 2.403 (2) Å in Co3(SeO3)3·H2O und zwischen 1.987 (4) Å und 2.301 (3) Å in der Ni-Verbindung, O-Se-O-Bindungswinkel liegen zwischen 92.8 (2)° und 104.9 (1)°. Wasserstoffbrückenlängen sind 2.802 (3) Å und 2.600 (4) Å in der Co-Verbindung, und 2.762 (6) Å und 2.561 (6) Å in Ni3(SeO3)3·H2O. Letztere ist eine der kürzesten bekannten Wasserstoffbrücken eines Wassermoleküls.相似文献
4.
Gerald Giester 《Monatshefte für Chemie / Chemical Monthly》1989,120(8-9):661-666
Summary Single crystal X-ray data of the hydrothermally grown new phase Li2Cu3(SeO3)2(SeO4)2 were measured with a four-circle diffractometer up to sin /=0.81 Å–1 [I2/a,Z=4,V=1175.5 Å3,a=16.293(6),b=5.007(2),c=14.448(6) Å, = 94.21(1)°]. The structure was determined by direct and Fourier methods and refined toR=0.034,R
w
=0.027 for 2 086 independent reflections.Cu(1)[4+1]O5 forms a tetragonal pyramid, Cu(2)[4 + 2]O6 is a strongly elongated octahedron. The Li atom is surrounded by four O atoms forming a distorted tetrahedron. Se(IV)O3 and Se(VI)O4 groups are in accordance to literature, mean Se-O bond lengths are 1.714 and 1.644 Å.
Die Kristallstruktur von Li2Cu3(SeO3)2(SeO4)2
Zusammenfassung Einkristall-Röntgendaten der hydrothermal gezüchteten neuen Phase Li2Cu3(SeO3)2(SeO4)2 wurden mit einem Vierkreisdiffraktometer im Bereich bis zu sin /=0.81 Å–1 gemessen [I2/a,Z=4,V=1175.5 Å3,a=16.293(6),b=5.007(2),c=14.448(6) Å, =94.21(1)°]. Die Kristallstruktur wurde mittels direkter und Fourier-Methoden bestimmt und für 2 086 unabhängige Reflexe zuR=0.034,R w =0.027 verfeinert.Cu(1)[4+1]O5 bildet eine tetragonale Pyramide, Cu(2)[4+2]O6 ist ein stark verlängertes Oktaeder. Das Li-Atom ist von vier O-Atomen in Gestalt eines verzerrten Tetraeders umgeben. Die Se(IV)O3-und Se(VI)O4-Gruppen entsprechen der Literatur, die mittleren Se-O-Abstände betragen 1.714 und 1.644 Å.相似文献
5.
Herta Effenberger 《Monatshefte für Chemie / Chemical Monthly》1986,117(10):1099-1106
Crystals of PbCu3(OH)(NO3)(SeO3)3·1/2H2O [a=7.761(3)Å,b=9.478(4)Å,c=9.514(4)Å, =66.94(2)°, =69.83(2)°, =81.83(2)°, space group P
,Z=2] and Pb2Cu3O2(NO3)2(SeO3)2 [a=5.884(2)Å,b=12.186(3)Å,c=19.371(4)Å, space group Cmc21,Z=4] were synthesized under hydrothermal conditions. Their crystal structures were refined with three-dimensional X-ray data toR
w=0.033 resp. 0.055. In PbCu3(OH)(NO3)(SeO3)3·1/2H2O the Cu atoms are [4+1] and [4+2] coordinated and via SeO3 groups a three-dimensional atomic arrangement is built up. In Pb2Cu3O2(NO3)2(SeO3)2 there are
sheets, which are connected only via Pb-O bonds ranging from 2.98 Å to 3.16 Å. 相似文献
6.
Hanuza J Maczka M Lorenc J Kaminskii AA Bohaty L Becker P 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2008,71(1):68-72
Polarised IR and Raman spectra of Na3Li(SeO4)2·6H2O single crystal have been recorded. Discussion of the results has been based on the factor group approach for the trigonal R3c (C3v6) space group with Z = 2. The obtained results for the spontaneous Raman scattering have been used in the discussion of the stimulated Raman spectra of the material studied—a new Raman laser crystal. 相似文献
7.
G. Giester 《Monatshefte für Chemie / Chemical Monthly》1996,127(4):347-354
Summary The new synthetic compound ZnFe
2
3+
(SeO3)4 forms at low-hydrothermal conditions at 220 °C. It belongs to the monoclinic system; the structure was determined by single-crystal X-ray diffraction in the space group Pc. The unit cell data are:a=8.196(4) Å,b=7.997(4) Å,c=8.033(4) Å, =92.27(3)°,V=526.1 Å3;Z=2. The structure of ZnFe
2
3+
(SeO3)4 contains two types of FeO6 octahedra, one distorted ZnO5 trigonal bipyramid, and four selenite groups. Formal clusters consisting of the ZnO5 group, edge-linked with both FeO6 groups and one SeO3 pyramid, are connected by common corners, involving three further selenite groups to a framework structure.
Die Kristallstruktur von ZnFe 2 3+ (SeO3)4
Zusammenfassung Die neue synthetische Verbindung ZnFe 2 3+ (SeO3)4 bildet sich bei niedrighydrothermalen Bedingungen (220°C). Die Kristallstruktur wurde mit Einkristallröntgenmethoden in der monoklinen Raumgruppe Pc gelöst. Die Zellparameter sind:a=8.196(4) Å,b=7.997(4) Å,c=8.033(4) Å, =92.27(3)°,V=526.1 Å3;Z=2. Die Kristallstruktur von ZnFe 2 3+ (SeO3)4 weist zwei Arten von FeO6-Oktaedern, eine verzerrte trigonale ZnO5-Dipyramide sowie vier Selenitgruppen auf. Formal können Cluster, bestehend aus dem ZnO5-Polyeder, kantenverknüpft mit den beiden FeO6-Gruppen sowie einer SeO3-Pyramide, beschrieben werden. Die Verknüpfung über Ecken zu einer Gerüststruktur erfolgt unter Beteiligung von drei weiteren Selenitgruppen.相似文献
8.
Syntheses within the system CuO-SeO2-H2O revealed four copper(II)-oxo-selenites. The crystal structures of these compounds were determined by single crystal X-ray techniques. Chemical formulae, lattice parameters and space groups are: Cu2O(SeO3)-I [a=8.925 (1) Å, P213], Cu2O(SeO3)-II [a=6.987 (5) Å,b=5.953 (4) Å,c=8.429 (6) Å, =92.17 (3)°, P21/n], Cu4O(SeO3)3-I [a=15.990 (8) Å,b=13.518 (8) Å,c=17.745 (12) Å, =90.49 (5)°, P21/a], and Cu4O(SeO3)3-II [a=7.992 (6) Å,b=8.141 (6) Å,c=8.391 (6) Å, =77.34 (3)°, =65.56 (3)°, =81.36 (3)°,
].All the Cu atoms are-with one exception-[4], [4+1], and [4+2] coordinated by O atoms. The four nearest O atoms are more or less distorted square planar arranged. Within the CuO4 squares the Cu-O bond lengths are significantly shorter for the [4] coordinated O atoms as compared with those of the [4+1] and [4+2] coordinated Cu atoms. The exception in the coordination of the Cu atoms is the Cu(1) atom in Cu2O(SeO3)-I with the site symmetry 3, which is trigonal dipyramidal [5] coordinated. A common feature of these four crystal structures is, that O atoms outside the SeO3 groups are tetrahedrally coordinated by four Cu(II) atoms. The Se atoms are as usual [3] coordinated, building up SeO3 pyramids. In all these four compounds the copper-oxygen polyhedra are combined to a three-dimensional network. 相似文献
9.
G. Giester 《Monatshefte für Chemie / Chemical Monthly》1994,125(5):535-538
Summary Single crystals of LiFe3+(SeO3)2 were prepared by hydrothermal synthesis. The crystal structure of LiFe3+(SeO3)2 is reported: tetragonal, space group I
2d,a=10.649(2) Å,c=9.959(2) Å,V=1129.4 Å3,Z=8, 1268 unique reflections,R=0.037. The structure contains LiFeO8 groups, built up by FeO6 octahedra edgesharing with strongly distorted LiO4 tetrahedra. These LiFeO8 groups share corners with trigonal pyramidal SeO3 groups to form a three dimensional network. The mean bondlengths are 1.994 Å, 2.006 Å and 1.699 Å for Li-O, Fe-O and Se(IV)-O, respectively.
Die Kristallstruktur von LiFe3+(SeO3)2
Zusammenfassung Einkristalle von LiFe3+(SeO3)2 wurden auf hydrothermalem Weg dargestellt und ihre Kristallstruktur bestimmt: tetragonal, Raumgruppe I 2d,a=10.649(2) Å,c=9.959(2) Å,V=1129.4 Å3,Z=8, 1268 unabhängige Reflexe,R=0.037. Kennzeichnend für die Atomanordnung sind LiFeO8 Gruppen, die aus FeO6 Oktaedern und mit ihnen kantenverknüpften, stark verzerrten LiO4 Tetraedern aufgebaut sind. Diese LiFeO8 Baueinheiten bilden, mit trigonal pyramidalen SeO3 Gruppen über Ecken verbunden, ein dreidimensionales Netzwerk. Die Mittelwerte der Li-O, Fe-O and Se(IV)-O Abstände sind 1.994 Å, 2.006 Å und 1.699 Å.相似文献
10.
F. J. Millero R. L. Johnson C. A. Vega V. K. Sharma S. Sotolongo 《Journal of solution chemistry》1992,21(12):1271-1287
The rates of reduction of Cu(II) with H2O2 have been measured in NaCl and NaBr solutions and mixtures with NaClO4 as a function of pH (6 to 9), temperature (5 to 45°C) and ionic composition (0.1 to 6M). The effect of pH on the rates was
found to be independent of temperature and ionic composition. The rates increased as a function of [H+] raised to the power of 1.3 to 1.6. Speciation calculations indicate that this pH dependence can be attributed to Cu(OH)2 being the reactive species. The rate constants in NaCl and NaBr and mixtures with NaClO4 were independent of ionic strength, but proportional to the halide concentration raised to the power of 2.0 (0.2 to 2.6M).
These results can be attributed to Cu(OH)2Cl
2
2−
being the reactive species to reduction with H2O2. The Cu(I) halide complexes formed from the reduction are not easily oxidized with O2 or H2O2. The faster rates in Br− solutions, which form stronger complexes with Cu+, support this contention. Measurements made in NaCl with added NaHCO3, NaB(OH)4 EDTA, NTA and glycine were also made. These measurements indicate that the CuL complexes (L=B(OH)
4
−
, CO
3
2−
, EDTA, NTA, and glycine) are not very reactive to reduction with H2O2. The addition of Mg2+ or Ca2+ caused the rates to increase due to the formation of MgL or CaL complexes and the resultant release of reactive Cu2+. 相似文献
11.
Gerald Giester 《Monatshefte für Chemie / Chemical Monthly》1992,123(11):957-963
Summary The crystal structure of the hydrothermally synthesized compound Fe(SeO2OH) (SeO4) · H2O was determined by single crystal diffraction methods:a=8.355(2) Å,b=8.696(2) Å,c=9.255(2) Å, =93.72(1)°,V=670.95 Å3;Z=4, space group P21/c,R=0.029,R
w=0.027 for 2430 independent reflections (sin /0.76 Å–1). Isolated FeO5(H2O)-octahedra share five corners with [SeO2OH] and [SeO4] groups to form sheets parallel to (100). These sheets are interconnected via hydrogen bonds only.
Die Kristallstruktur von Fe(SeO2OH)(SeO4)·H2O
Zusammenfassung Die Kristallstruktur der hydrothermal dargestellten Verbindung Fe(SeO2OH) (SeO4)·H2O wurde mittels Einkristallbeugungsmethoden bestimmt:a=8.355(2) Å,b=8.696(2) Å,c=9.255(2) Å, =93.72(1)°,V=670.95 Å3;Z=4, Raumgruppe P21/c,R=0.029,R w=0.027 für 2 430 unabhängige Reflexe (sin / 0.76 Å–1). Isolierte FeO5(H2O)-Oktaeder teilen fünf Ecken mit [SeO2OH]- und [SeO4]-Gruppen, wobei sie Schichten parallel (100) bilden. Diese Schichten sind nur über Wasserstoffbrücken miteinander verbunden.相似文献
12.
Thermal and calorimetric studies were carried out on M(IO3)2·6H2O and M(IO3)2·6D2O forM
2+=Ca2+ and Sr2+, using DTA and DSC methods. The thermal behaviour of the ordinary and deuterated hydrates is outlined and the differences observed between them are discussed. The enthalpies of the phase transitions were determined. The H
f
o
for Ca(IO3)2·6H2O, Ca(IO3)2·6H2O(D2O) and Sr(IO3)2·6H2O(D2O) were calculated from the H
deh data and comments are made on the isotope effect observed.
Zusammenfassung Mittels DTA- und DSC-Methoden wurden Me(IO3)2·6H2O und Me(IO3)2·6D2O (mitMe 2+=Ca2+ und Sr2+) thermisch und kalorimetrisch untersucht. Es wird ein Überblick über das thermische Verhalten ordentlicher und deuterierter Hydrate gegeben, in dem auch die Unterschiede zwischen beiden diskutiert werden. Die Enthalpien der untersuchten Phasenumwandlungen wurden bestimmt. Aus den Daten für Hdeh wurde Hf von Ca(IO3)2·6H2O, Ca(IO3)2H2O(D2O) und Sr(IO3)2·6H2O(D2O) berechnet und Bemerkungen zum beobachteten Isotopeneffektes gemacht.相似文献
13.
《Analytical letters》2012,45(10):1975-1989
ABSTRACT Electroanalytical methods have been widely used for determination of Se(IV), but the nature of the reduction processes involved is not well understood. Polarographic reduction occurs in three waves (i1, i2, and i3) the height of which changes with pH. We proved that in wave i1, H3SeO3 + is reduced, in i2 H2SeO3, and in i3 HSeO3 -. SeO3 2? is not reducible. All reductions involve a transfer of six electrons and yield selenides. Limiting currents are controlled by the rate of protonation. As proton donors, in addition to H3O+, the acid forms of the buffer present also act. Limiting currents increase markedly with increasing concentration of the buffer. Tenfold increase in buffer concentration can result in up to 200% increase in limiting current. 相似文献
14.
Trilochan Swain Prakash Mohanty 《Phosphorus, sulfur, and silicon and the related elements》2013,188(8):1702-1713
Abstract Substitution reactions of the complex [Pt(dien)H2O]2+ (where dien = diethylentriamine or 1,5-diamino-3-azapentane) with sulfur-containing L-cystine have been studied in a 1.0 × 10?1 mol dm?3 aqueous perchlorate medium at various temperatures (298–323 K) and 4.45 ≤ pH ≤ 2.15 using UV-vis spectroscopy. The products obtained have been characterized by their infrared and 1H NMR datasets at various pH levels and temperatures. From infrared and 1H NMR data, products have indicated that [Pt(dien)H2O]2+ reacted with L-cystine forming a Pt–S bond at low pH. At high pH, a product complex through the Pt–N bond has been formed. All rate constants have been evaluated from nonlinear double exponential plots. The activation parameters ΔH# and ΔS# have been determined using the Eyring equation. The products, SNi, and reversible rate constants have been evaluated. Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file. GRAPHICAL ABSTRACT 相似文献
15.
Ioannis T. Papadas Chariklia Kosma Yiannis Deligiannakis 《Journal of colloid and interface science》2009,339(1):19-30
Cu2+ binding on γ-Al2O3 is modulated by common electrolyte ions such as Mg2+, , and in a complex manner: (a) At high concentrations of electrolyte ions, Cu2+ uptake by γ-Al2O3 is inhibited. This is partially due to bulk ionic strength effects and, mostly, due to direct competition between Mg2+ and Cu2+ ions for the SO− surface sites of γ-Al2O3. (b) At low concentrations of electrolyte ions, Cu2+ uptake by γ-Al2O3 can be enhanced. This is due to synergistic coadsorption of Cu2+ and electrolyte anions, and . This results in the formation of ternary surface species (SOH2SO4Cu)+, (SOH2PO4Cu), and (SOH2HPO4Cu)+ which enhance Cu2+ uptake at pH < 6. The effect of phosphate ions may be particularly strong resulting in a 100% Cu uptake by the oxide surface. (c) EPR spectroscopy shows that at pH pHPZC, Cu2+ coordinates to one SO− group. Phosphate anions form stronger, binary or ternary, surface species than sulfate anions. At pH pHPZC Cu2+ may coordinate to two SO− groups. At pH pHPZC electrolyte ions and are bridging one O-atom from the γ-Al2O3 surface and one Cu2+ ion forming ternary [γ-Al2O3/elecrolyte/Cu2+] species. 相似文献
16.
Gerald Giester 《Monatshefte für Chemie / Chemical Monthly》1991,122(4):229-234
Summary The crystal structure of synthetic Cu3SeO4(OH)4 was determined by single crystal X-ray methods:a=8.382 (2) Å,b=6.087 (1) Å,c=12.285 (2) Å,V=626.8 Å3,Z=4, space group Pnma,R=0.026,R
w
=0.021 for 1255 independent reflections (sin / 0.8 Å–1). The crystal structure is isotypic to that of the mineral antlerite, Cu3SO4(OH)4. The copper atoms are Jahn-Teller distorted with Cu[4+2]O6 polyhedra forming triple chains along [010]. These chains are linked via SeO4 tetrahedra and weak hydrogen bonds to a framework structure.
Die Kristallstruktur von synthetischem Cu3SeO4(OH)4
Zusammenfassung Die Kristallstruktur von synthetischem Cu3SeO4(OH)4 wurde mittels Einkristall-Röntgenmethoden ermittelt:a=8.382 (2) Å,b=6.087 (1) Å,c=12.285 (2) Å,V=626.8 Å3,Z=4, Raumgruppe Pnma,R=0.026,R w =0.021 für 1255 unabhängige Reflexe (sin / 0.8 Å–1). Die Kristallstruktur ist isotyp mit der des Minerals Antlerit, Cu3SO4(OH)4. Die Kupferatome sind Jahn-Teller-verzerrt, die Cu[4+2]O6 Polyeder bilden Dreierketten entlang [010]. Diese Ketten sind über SeO4-Tetraeder und schwache Wasserstoffbrücken zu einer Gerüststruktur verbunden.相似文献
17.
Matthias Weil 《Journal of solid state chemistry》2003,172(1):35-44
Mercury(I) selenite(IV) is polymorphic and crystallizes at least in three modifications, named α-, β-and γ-Hg2SeO3. Polycrystalline β-Hg2SeO3 was prepared by precipitation of a concentrated mercurous nitrate solution with selenous acid. Hydrothermal treatment of the colorless β-Hg2SeO3 powder in demineralized water at 250°C (10 days) yields light-yellow single crystals of α-Hg2SeO3 which show the highest density of the three modifications. Colorless needle-shaped single crystals of β-Hg2SeO3 and very few single crystals of γ-Hg2SeO3 co-crystallize from strongly diluted Hg2(NO3)2 and H2SeO3 solutions and were grown by a diffusion technique. All crystal structures were solved and refined from single crystal diffractometer data sets and are based on Hg22+ dumbbells and trigonal pyramidal SeO32− anions as the main building units. A common structural feature of all modifications is the formation of open channels extending parallel to the shortest crystallographic axis. The non-bonding orbitals of the SeIV atoms are stereochemically active and protrude into the channels. Upon heating in an open system under N2 atmosphere, both α- and β-Hg2SeO3 decompose in a well-separated three-step mechanism. The first step (T > 250°C) involves disproportionation into elementary mercury and α-HgSeO3 which at ca. 400°C subsequently transforms into β-HgSeO3. The second step between T = 400 and 500°C is accompanied by a loss of Hg and SeO2 and the formation of the basic salt Hg3SeO6. In the third step, at temperatures between T = 500° and 600°C, this material decomposes completely. Upon heating in a closed system (sealed silica capillaries), β-Hg2SeO3 transforms between 320-340°C into the more dense α-Hg2SeO3 which on further heating likewise converts into elementary mercury and β-HgSeO3. 相似文献
18.
Detailed quartet and doublet potential energy surfaces for the Ti+ + C3H8 → TiC3H6+ + H2 and Ti+ + C3H8 → TiC2H4+ + CH4 elimination reactions have been studied using density functional theory with B3LYP functional and ab initio coupled cluster
CCSD(T) methods. Several H2 elimination and CH4 elimination reaction paths have been examined including the IRC following. In particular, the mechanisms involving, respectively,
the H2TiC3H6+ and CH3TiHC2H4+ intermediates have been studied.
Contribution to the Mark S. Gordon 65th Birthday Festschrift Issue. 相似文献
19.
α-Fe2O3/SiO2纳米颗粒混合体系表面的酸碱性质及其对重金属离子的吸附行为 总被引:1,自引:0,他引:1
以Fe(NO3)3·9H2O和正硅酸乙酯(TEOS)为原料, 通过溶胶-凝胶法和辅助模板法分别制备了纳米α-Fe2O3和SiO2, 并对所合成样品进行了粉末X射线衍射(XRD)和BET表征. 使用自动电位滴定仪测定了α-Fe2O3/SiO2纳米颗粒混合体系的表面酸碱性质. 研究了在不同pH下α-Fe2O3/SiO2混合体系对Cu2+、Pb2+、Zn2+离子的吸附行为. 基于上述实验数据, 用WinSGW软件计算了α-Fe2O3/SiO2混合体系表面酸碱配位常数, 并得出结论: α-Fe2O3/SiO2混合体系表面反应为单一脱质子反应≡XOH ⇔ ≡XO-+ H+(lg K = -8.19±0.15), 明显区别于同时具有加质子和脱质子反应的α-Fe2O3/SiO2/γ-Al2O3, α-Fe2O3/γ-Al2O3和SiO2/γ-Al2O3等纳米颗粒混合体系. 在此基础上拟合得到α-Fe2O3/SiO2混合体系吸附重金属离子Cu2+、Pb2+、Zn2+的表面络合反应平衡常数分别为:
≡XOH + M2+ ⇔ ≡XOM++ H+ [lg K = -3.1, -3.6, -3.8 (M = Cu, Pb, Zn)].
≡XOH+M2++H2O ⇔≡XOMOH+2H+[lg K = -8.8, -8.0, -10.5 (M = Cu, Pb, Zn)] 相似文献
20.
M. S. Hegde 《Journal of Chemical Sciences》1984,93(3):373-387
Results of investigations of the adsorption and decomposition of methanol on the surface of transition metals such as Fe,
Ni, Cu, Pd, Ag, Mo, W and Pt byuv and x-ray photoelectron spectroscopy, electron energy loss spectroscopy, Auger electron spectroscopy and thermal desorption
spectroscopy have been reviewed. The first step in the decomposition of CH3OH on these metal surfaces is the formation of the methoxy species, OCH3 radical. In the case of Fe, Mo and W, complete decomposition of CH3OH occurs leaving CO(β), H2 and CH4 on the surface. Dissociation proceeds upto CO(α) and H2 on the surface of Ni, Pd and Pt whereas on Ag and Cu, selective oxidation of CH3OH to H2CO is preferred. The difference in the reactivity of metals towards CH3OH is rationalised from the heats of adsorption of O2, CO and H2 on these metals.
Contribution No. 253 from the Solid State and Structural Chemistry Unit. 相似文献