close

Вход

Забыли?

вход по аккаунту

?

The SF5Ox Radicals x=0Ц3.

код для вставкиСкачать
Angewandte
Chemie
Atmospheric Chemistry
The SF5Ox Radicals, x = 0–3**
Marc Kronberg, Stefan von Ahsen, Helge Willner,* and
Joseph S. Francisco*
Sulfur hexafluoride, SF6, has found widespread use beyond its
original application as an insulator gas in electrical highvoltage equipment and switchgear boxes.[1] It is a major
[*] Dr. M. Kronberg, Dr. S. von Ahsen, Prof. Dr. H. Willner
Fachbereich C, Anorganische Chemie
Bergische Universitt Wuppertal
Gaussstrasse 20, 42097 Wuppertal (Germany)
Fax: (+ 49) 202-439-3053
E-mail: willner@uni-wuppertal.de
Prof. Dr. J. S. Francisco
Department of Chemistry, Earth and Atmospheric Sciences
Purdue University
1393 H. C. Brown Building, West Lafayette IN 47907 (USA)
Fax: (+ 1) 765-494-0239
E-mail: francisc@purdue.edu
[**] This work was supported by the Deutsche Forschungsgemeinschaft.
J.S.F. expresses his thanks to the Alexander von Humboldt
Foundation for a research award for senior U.S. scientists.
Supporting information for this article is available on the WWW
under http://www.angewandte.org or from the author.
Angew. Chem. Int. Ed. 2005, 44, 253 –257
plasma etching gas now commonly used in the semiconductor
industry.[2] Because SF6 is an excellent source of fluorine
atoms upon strong excitation and contains no carbon, it leaves
no carbonaceous deposits in the plasma etching process.[3–5]
An attractive feature of SF6 is its nonflammability and
chemical inertness. Surprisingly, the environmental concerns
of the long-term usage of SF6 have become an issue only
recently as a result of its increasing abundance in the
atmosphere.[6, 7] Because SF6 is a greenhouse gas with a
global-warming potential that is 23 900 times higher than that
of CO2, this also has contributed to the growing concern about
its atmospheric impact.[8] Recent studies of the environmental
consequences of the decomposition of SF6 have attempted to
characterize the breakdown products that result from electrical discharges.[9–12] The main products observed under
various spark arc and corona discharge conditions are SF2O,
SF2O2, and SF4O. Detailed mechanisms to describe their
formation remain unclear.[13, 14] The observation of the even
stronger greenhouse gas SF5CF3, chemically related to SF6, in
stratospheric air samples has further raised questions of the
atmospheric consequence of these species.[15] At present the
molar ratio of SF5CF3 relative to SF6 amounts to about 4 %.
Here we report on the spectroscopic characterization of the
key radical species SF5, a product of the photodissociation of
SF6 and SF5CF3, and the radicals SF5O, SF5OO, and SF5OOO,
which form in the oxidation reactions of the SF5 radical.
The SF5 radical: Smardzewski et al.[16] found two new IR
bands at 812 and 552 cm 1 from the photodissociation of SF5X
compounds (X = F, Cl, Br, SF5). The same bands were
observed in reactions of F atoms with SF4, which confirmed
the presence of the SF5 radical. Andrews et al.[17] also isolated
the SF5 radical in an Ar matrix and observed an additional IR
band at 885 cm 1. Since these studies, other bands of SF5 have
not been reported nor has the UV spectrum of SF5 been
published.
The SF5 radical belongs to the symmetry point group C4v.
Hence, the nine normal modes are represented by three A1,
two B1, one B2, and three E modes, of which only the A1- and
E-type vibrations are IR active. In order to measure all six IRactive modes, a much more efficient synthesis for matrixisolated SF5 radicals was needed. For this purpose the
thermally labile precursors S2F10,[18] SF5NO2,[19] and
N(SF5)3[20, 21] highly diluted in Ne or Ar were flash thermolyzed at low pressures and subsequently quenched as matrices. All three precursors resulted in the same set of IR matrix
bands with three additional weak bands at 633.0, 524.7, and
387.2 cm 1 (Ne matrix). In Table 1 the bands are assigned by
comparison with the calculated band positions and intensities.
The UV spectrum of SF5 was obtained from the matrixisolated thermolysis products of SF5NO2 diluted in Ne.
Because a 1:1 mixture of SF5 and NO2 is present in the
matrix, the cross sections of SF5 were determined by
calibration[22] using the UV spectrum of the by-product
NO2, and a reference spectrum of NO2 could be used in
turn for subtraction. The UV spectrum of SF5 shows a
structureless weak absorption beginning at about 235 nm (s <
10 20 cm2) and ending at 200 nm with an absorption cross
section of 1.1 10 18 cm2 (see the Supporting Information).
Hence, SF5 should be photostable in the stratosphere, as the
DOI: 10.1002/anie.200461235
2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
253
Communications
Table 1: Calculated [B3LYP/6–311 + + G(3df,3pd)] and observed IR band positions [cm 1] and relative
intensities of the matrix-isolated radicals SF5 and SF5OO.
absorber (for its Ne matrix UV spectrum, see the Supporting Information).
SF5
SF5OO
Ne
Ar
Calcd[a,b]
O2
Calcd[a,b]
The SF5OO radical: The existence
ñ [cm 1] Rel. int. ñ [cm 1] ñ [cm 1] Rel. int.
ñ [cm 1] Rel. int. ñ [cm 1] Rel. int.
of the SF5OO radical was first postulated by Czarnowski and Schu891.7
15
887
862
16
n1 A1 1135
6.1
1217
14
n1 A’
macher[25, 26] in the mechanism for for817.8
100
797
778
100
n7 E
929
81
892
94
n2 A’
100
880
100
n13 A’’
633.0
2.4
631
601
0.90 n2 A1 919
mation of the trioxide F5SOOOSF5.
65
855
71
n3 A’
553
–
n5 B2 870
The trioxide is accessible by photolysis
553.4
6.6
552
522
2.9
n3 A1 693
2.0
653
0.88 n4 A’
of SF5Cl in the presence of a large
622
0.09 n5 A’
524.7
1.1
524
494
0.01 n8 E
excess of oxygen at low temperatures.
437
–
n4 B1
606
0.01 n6 A’
Feliz and Schumacher[27] suggested that
602
17
582
12
n7 A’
387.2
0.6
384
339
0.01 n9 E
the
SF5 radicals, the primary photolysis
1.6
551
3.0
n14 A’’
226
–
n6 B2 555
products
together with chlorine atoms,
[a] A relative intensity of 100 corresponds to 918 km mol 1 for SF5 and 397 km mol 1 for SF5OO. [b] Low1
rapidly
add
molecular oxygen. Schufrequency modes in cm , (rel. int.), assignment: 530 (2.4), n8 A’; 488 (0.03), n9 A’; 426 (0.25), n15 A’’; 408
macher and co-workers could not iden(0.35), n10 A’; 329 (0.13), n11 A’; 315 (0.00), n16 A’’; 282 (0.05), n17 A’’; 218 (0.09), n12 A’; 82 (0.01), n18 A’’.
tify the SF5OO radicals directly in their
experiment. They argued that SF5OO
is unstable and the bimolecular self reaction yielding SF5O
reaction with oxygen is expected to be its dominant fate. This
is similar to the known atmospheric fate of the radical CF3,
and O2 is very fast.
which is converted rapidly into CF3OO in the presence of
Indeed, in our experiments conducted in an oxygen
matrix, SF5 adds O2. However, flash thermolysis of the
O2.[23]
trioxide SF5OOOSF5 in excess of noble gas yields SF5O +
The SF5O radical: Merill and Cady postulated that the
SF5O radical results from irradiation of bis(pentafluorosulfur)
SF5 + O2, although a mixture of SF5O and SF5OO is expected.
peroxide, F5SOOSF5.[24] Czarnowski and Schumacher[25, 26] also sugTable 2: Calculated [B3LYP/6-311 + + G(3df,3pd)] and observed IR band positions and relative
gested the formation of SF5O from
intensities of the matrix-isolated radicals SF5O and SF5OOO.
the thermal decomposition of the
peroxide. Neither of these studies
SF5O
SF5OOO
Ne
Ar
Calcd[a,b]
O2
Calcd[a,b]
identified the radical, although a
1
1
1
1
[27]
ñ [cm ] Rel. int. ñ [cm ] ñ [cm ] Rel. int.
ñ [cm ] Rel. int. ñ [cm 1] Rel. int.
study by Feliz and Schumacher,
in which CO was added to
937.7
47
933
912
66
n1 A1 1513
18
1637
46
n1
F5SOOSF5
during
photolysis,
915.6
30[d]
912
883
81
n8 B1
899
88
891
100
n2
905.9
100
899
877
100
n12 B2 897
48
876
74
n3
showed that carbon monoxide was
730
1.1
n2 A1
884
100
869
81
n4
oxidized to CO2 providing indirect
621
0.42 n3 A1
755
1.9
726
4.8
n5
evidence for the existence of SF5O.
597
0.84 n4 A1
612
0.42 n6
Quantum chemical calculations
609.0
1.0
604
587
4.4
n13 B2 614
3.9
592
1.7
n7
predict the SF5O radical to have
602.3
12
601
587
7.9
n5 A1
585
3.2
n8
C2v symmetry (and not C4v) as an
575.1
5.4
571
550
4.4
n9 B1
600
16
579
19
n9
SO bond with participation of an
520
0.05 n14 B2 592
1.6
558
2.8
n10
1
1
oxygen sp or p orbital results in a p[a] A relative intensity of 100 corresponds to 407 km mol for SF5O and 499 km mol for SF5OOO.
type singly occupied molecule orbi[b] Low-frequency modes of SF5O in cm 1, (rel. int.), assignment: 475 (inactive), n7 A2 ; 416 (0.74), n10 B1;
tal (SOMO) mainly located at the
350 (0.00), n15 B2 ; 324 (0.00), n6 A1; 289 (0.09), n11 B1. [c] Low-frequency modes of SF5OOO in cm 1 (rel.
int.): 518 (0.04), 477 (0.00), 458 (0.81), 346 (0.00), 328 (0.42), 320 (1.0), 193 (1.3), 67 (1.6), 63 (0.30), 44
O atom. This orbital geometry is
(0.02), 22 (0.01). [d] Intensity affected by overlap with SF4O bands.
inconsistent with a fourfold axis.
Our observed IR spectrum of SF5O
isolated in Ne matrix obtained by
flash thermolysis of SF5OOSF5 and SF5OOOSF5 is consistent
The F5S O2 bond in SF5OO must be weaker than the O O
with this finding. The observed IR band positions are
bonds in the trioxide. For the trioxide a bonding energy of
presented in Table 2 and Figure 1 and are in accordance
106 kJ mol 1 and for SF5 OO a dissociation energy of about
with the computational data. From the 15 fundamentals (six
55 kJ mol 1 were estimated.[25, 26] Our observations are in
A1, one A2, four B1, four B2 modes) only the A2 mode is IR
agreement with these data. DFT calculations [B3LYP/6311 + + G(3df,3pd)] predict a dissociation energy of
inactive. Six fundamentals were observed while for the
19.1 kJ mol 1, which represents a lower limit as the bond
missing modes the calculations predict either a low frequency
(not yet measured) and/or a very low intensity. Photolysis of
strengths of weak bonds are generally underestimated.
SF5O in a Ne matrix with full radiation of a xenon or mercury
SF5OO is expected to show Cs symmetry, like many other
high-pressure lamp resulted in a slow decrease of its IR bands,
peroxy radicals. Hence, all 18 fundamentals (twelve A’ and six
yielding mainly SF4O and fluorine atoms, and as a minor
A’’) should be observable in the IR spectrum. The typical
feature in the IR spectrum of matrix-isolated SF5OO is the
channel SF4 + OF (see Figure 1). Hence, SF5O is a weak UV
254
2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.angewandte.org
Angew. Chem. Int. Ed. 2005, 44, 253 –257
Angewandte
Chemie
Table 3: Calculated [B3LYP/6-311 + + G(3df,3pd)] structures, partial
charges, and dipole moments of the SF5Ox radicals (x = 0–3).[a]
Symmetry
r(SF)[b]
SF5
SF5O
SF5OO
SF5OOO
C4v
1.623
1.554
C2v
1.585
1.591
1.580
1.612
Cs
1.585
1.588
1.567
1.805
1.276
C1
1.591 (avg)
1.585
87.6
92.0
92.4
90.1
90.8
90.8
91.2
87.2
114.5
87.4 (avg)
91.1 (avg)
92.6 (avg)
90.5 (avg)
120.4
107.4
180.0
180.0
r(SO)
r(OO)[c]
a(FSF)[d]
91.8
a(OSF)[e]
a(OOS)
a(OOO)
t
Figure 1. Upper half: IR spectrum of SF5O radicals isolated in an Ar
matrix; bands of the SF5O radical are labeled with (o). The simulated
spectrum of SF5O is shown underneath. Lower half: IR spectrum of
SF5O radicals isolated in an O2 matrix; bands of the product SF5OOO
are labeled with (*). The simulated spectrum of SF5OOO is shown
underneath. Both experimental IR spectra are difference spectra from
spectra measured before and after photolysis. The photolysis products
show negative bands while the absorptions of the photolyzed radicals
are positive. The assigned absorptions of the photolysis products
belong to SF4O (a), SF4 (b), and FOO (c).
presence of an absorption at 1135 cm 1, which is assigned to
the O O stretching mode. The seven most intensive fundamentals were observed while the eleven missing modes have
low intensities and/or are outside the experimental spectral
range. Band positions and intensities are in good agreement
with the calculated data (see Table 1).
The SF5OOO radical: Trioxy radicals are formed when a
highly electronegative oxy radical interacts with molecular
oxygen. In analogy to CF3OOO[28] the radical SF5OOO is
observed in an oxygen matrix. The IR-matrix spectrum of
SF5OOO has several dominant features that distinguish the
trioxy radical from SF5O (see Table 2 and Figure 1): 1) a
strong band at 1513 cm 1, assigned as n(OO) of the terminal
OO bond; 2) a strong red shift of the stretching modes of the
SF5O moiety; 3) significant differences in the intensities of the
SF5O fundamentals when recorded with O2 or Ar as matrix
materials; 4) the rapid UV photolysis of O2-matrix-isolated
SF5OOO while SF5O photolyzes one order of magnitude
slower when isolated in Ne matrix. In oxygen matrix
photolysis produces SF4O and FOO.
The computations predict a structure with C1 symmetry,
close to Cs, and a SF5O OO bond length of 2.36 . Table 3
presents the (calculated) structural data and some properties
of the SF5Ox radicals, x = 0–3. The calculated structures are
shown in the Supporting Information.
With the characterization of the SF5Ox (x = 0–3) radicals,
their existence is now proven. Nevertheless, their significance
in atmospheric chemistry has to be considered. A summary of
the important oxidation reactions in the atmosphere is shown
in Figure 2. SF6 photolysis is possible only in the upper
stratosphere as the solar flux in the high-energy UV region is
significant only above the ozone layer. The formed SF5
Angew. Chem. Int. Ed. 2005, 44, 253 –257
45.0
q(S)
q(F)eq,avg
q(F)ax
q(O)[f ]
+1.20
0.26
0.17
+1.05
0.18
0.26
0.05
m
0.28
0.05
+1.17
0.16
0.29
0.10
0.12
0.63
1.605
2.362
1.192
+0.88
0.17
0.25
0.05
+0.08
0.00
1.56
[a] Bond lengths r are given in , bond angles a and dihedral angles t in
8, charges q in units of e, and dipole moments m in Debye. [b] Feqs, Fax : last
value. [c] SO OO and OO O. [d] FaxSFeq. [e] OSFeq. [f] In order of
SF5O1O2O3.
Figure 2. Reaction scheme for SF5Ox species in the atmosphere.
radicals react with O2 rather than degrade photochemically
due to the high concentration of molecular oxygen in the
atmosphere. The peroxy radical is probably in equilibrium
with the SF5 radical as the calculations and experiments
predict only a weak F5S O bond. However, the peroxy radical
can be reduced by reaction with NO, CO, or O3 forming the
oxy radical SF5O. The oxy radical is expected to be photostable but, in equilibrium with the SF5OOO radical, it will be
photolyzed much faster. SF5O is expected to oxidize atmospheric trace compounds like NO. Independent of the
degradation process—thermal or photochemical—SF5O is
www.angewandte.org
2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
255
Communications
converted to SF4O, which is thermally and photochemically
stable. The latter compound undergoes hydrolysis to form
SO2F2, which is even more stable. Because hydrolysis requires
significant water concentration, a downward diffusion of
SF4O and/or SO2F2 from the stratosphere into more humid air
should be observable. Finally, SO2F2 hydrolyzes very slowly
(yields sulfuric acid and HF) which makes it suitable as a
tracer for SF6 or SF5CF3 degradation in the atmosphere.
Experimental Section
Precursors for the thermal radical generation: The compounds S2F10,
N(SF5)3, and SF5NO2 were used as sources for SF5 radicals. S2F10[29]
and N(SF5)3[20] were prepared as described in the literature. SF5NO2
was provided by N. Lu (group J. S. Thrasher).[19] For SF5O generation
the compounds SF5OOSF5[25] and SF5OOOSF5[26] were used and
prepared according to literature procedures.
Generation of the radicals in matrix: SF5 or SF5O radicals were
generated by low-pressure flash thermolysis of the respective
precursors diluted 1:1000 with Ne or Ar and subsequent quenching
of the reaction products in a noble-gas matrix. The stable precursors
S2F10 and SF5NO2 were mixed with the excess noble gas in a 1-L
stainless-steel storage container. The labile precursors N(SF5)3,
SF5OOSF5, and SF5OOOSF5 were placed in a U-trap mounted
directly in front of the matrix support and cooled to temperatures of
65 8C, 125 8C, 120 8C, respectively (maintaining the respective
vapor pressures are in the 10 3-mbar range). A flow of nobel gas
passed the cooled samples achieving a mixing ratio of noble gas to
host close to 1:1000. Finally, the gas mixture passed the thermolysis
device that was mounted directly in front of the matrix support and
heated to 400 8C for S2F10, 340 8C for SF5NO2, 400 8C for N(SF5)3,
420 8C for SF5OOSF5, and 200 8C for SF5OOOSF5. The matrix support
(Cu block) was held under high vacuum, and the matrices were
formed at 16 K (Ar) or 6 K (Ne). About 1 mmol of noble gas was used
in a typical experiment and deposited within 10–20 min.
SF5OO and SF5OOO were generated by isolating SF5 or SF5O in
O2 matrix at 16 K. Photolysis experiments on the matrix-isolated
species were carried out with UV light from a 150-W Xe (AMKO) or
Hg high-pressure lamp (TQ 150, Heraeus) or from a Hg low-pressure
lamp (TK 15, Heraeus)—in some cases in combination with a 235-nm
cutoff filter (Schott). Details of the matrix apparatus are given
elsewhere.[30]
IR spectra of the matrix-isolated species were recorded with a FTIR spectrometer (IFS 66 v/S, Bruker) with a resolution of 1 cm 1 (Ar,
O2 matrix) or 0.25 cm 1 (Ne matrix) in reflection mode. A KBr (or a
6-mm Mylar/Ge for SF5 far-IR) beamsplitter was used together with a
DTGS detector, and 64 scans were co-added. UV spectra of Nematrix-isolated compounds were measured in reflection mode using a
quartz fiber optic (Hellma) with a Lambda 900 spectrometer (Perkin
Elmer). An integration time of 1 s per data point, a data point spacing
of 1 nm, and a slit width of 0.5 nm were applied.
All calculations were performed using the Gaussian98 software
package.[31] For accurate structures, energies, and vibrational frequencies the density functional[32] method B3LYP[33, 34] and a 6-311 +
+ G(3df,3dp) basis set was used. Within the IR simulation procedure
for each normal mode a Gaussian function was derived which is
characterized by three parameters: calculated band position, calculated total (integrated) intensity as given in the G98 output file, and a
half height width set to 4 cm 1. Integrated intensity and absorption
differ only by a constant factor for a Gaussian band profile.
Received: July 8, 2004
.
Keywords: atmospheric chemistry · matrix isolation · radicals ·
sulfur fluorides · vibrational spectroscopy
256
2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
[1] V. N. Maller, M. S. Naidu, High Voltage Insulation and Arc
Interruption in SF6 and Vacuum, Pergamon, Oxford, 1981.
[2] D. M. Manos, D. L. Flamm, Plasma Etching: An Introduction,
Academic Press, Boston, 1989.
[3] A. Picard, G. Turban, B. Grolleau, J. Phys. D 1986, 19, 991.
[4] R. Pinto, K. W. Ramonathan, R. S. Baba, J. Electrochem. Soc.
1987, 134, 165.
[5] K. R. Ryan, I. C. Plumb, Plasma Chem. Plasma Process. 1988, 8,
263.
[6] M. Maiss, C. A. M. Brenninkmeijer, Environ. Sci. Technol. 1998,
32, 3077.
[7] J. W. L. Goodwin, A. G. Salway, T. P. Murrels, C. J. Dove, H. S.
Eggleston, UK Emissions of Air Pollutants 1970–1997: A Report
of the National Atmospheric Emissions Inventury, AEA Technology, Harwell, 1999.
[8] Scientific Assessment of Ozone Depletion: 1998, Global Ozone
Research and Monitoring Project, Rep. 44, World Meteorological
Organization, Geneva, 1999.
[9] G. D. Griffin, C. E. Easterly, I. Sauers, H. W. Elles, L. G.
Christopherous, Toxicol. Environ. Chem. 1984, 9, 139.
[10] F. Y. Chu, IEEE Trans. Electr. Insul. 1986, E1–21, 693.
[11] A. Derodouri, J. Casanovas, R. Grob, J. Mathieu, IEEE Trans.
Electr. Insul. 1989, 24, 1147.
[12] R. J. van Brunt, J. T. Herron, IEEE Trans. Electr. Insul. 1990, 25,
75.
[13] O. Toubert, J. Pelletiev, C. Fiori, T. A. N. Tan, J. Appl. Phys. 1990,
67, 4291.
[14] K. R. Ryan, I. C. Plumb, Plasma Chem. Plasma Process. 1990,
10, 207.
[15] W. T. Sturges, T. J. Wallington, M. D. Hurley, K. P. Shine, K.
Sihra, A. Engel, D. E. Oram, S. A. Penkett, R. Mulvaney,
C. A. M. Brenninkmeijer, Science 2000, 289, 611.
[16] R. R. Smardzewski, W. B. Fox, J. Chem. Phys. 1977, 67, 2309.
[17] P. Hassanzadeh, L. Andrews, J. Phys. Chem. 1992, 96, 79.
[18] H. L. Roberts, J. Chem. Soc. 1962, 3183.
[19] N. Lu, J. S. Thrasher, S. von Ahsen, H. Willner, D. Hnyk, H.
Oberhammer, D. Lentz, 224th ACS Fluorine Division National
Meeting, ACS Meeting Abstracts 224:044-FLUO Part 1, Boston,
USA, 2002.
[20] J. S. Thrasher, J. B. Nielsen, J. Am. Chem. Soc. 1986, 108, 1108.
[21] M. R. Choudhury, J. W. J. Harrell, J. B. Nielson, J. S. Thrasher, J.
Chem. Phys. 1988, 89, 5353.
[22] S. Sander, H. Pernice, H. Willner, Chem. Eur. J. 2000, 6, 3645.
[23] M. K. W. Ko, N. D. Sze, J. M. Rodriguez, D. K. Weistenstein,
C. W. Heisey, R. P. Wayne, P. Biggs, C. E. Canosa-Mas, H. W.
Sidebottom, J. Treacy, Geophys. Res. Lett. 1994, 21, 101.
[24] C. I. Merrill, G. H. Cady, J. Am. Chem. Soc. 1961, 83, 298.
[25] J. Czarnowski, H. J. Schumacher, J. Fluorine Chem. 1978, 12, 497.
[26] J. Czarnowski, H. J. Schumacher, Int. J. Chem. Kinet. 1978, 10,
111.
[27] M. Feliz, H. J. Schumacher, J. Photochem. 1981, 15, 109.
[28] S. von Ahsen, H. Willner, J. S. Francisco, Angew. Chem. 2003,
115, 4838; Angew. Chem. Int. Ed. 2003, 42, 4690.
[29] G. Brauer, Handbuch der prparativen Anorganischen Chemie,
3rd ed., Ferdinand Enke, Stuttgart, 1975/1981.
[30] H. Schnckel, H. Willner in Infrared and Raman Spectroscopy:
Methods and Applications (Ed.: B. Schrader), VCH, Weinheim,
1994, p. 297.
[31] Gaussian 98 (Revision A.7), M. J. Frisch, G. W. Trucks, H. B.
Schlegel, G. E. Scuseria, M. A. Robb, J. R. Cheeseman, V. G.
Zakrzewski, J. A. Montgomery, R. E. Stratmann, J. C. Burant, S.
Dapprich, J. M. Millam, A. D. Daniels, K. N. Kudin, M. C. Strain,
O. Farkas, J. Tomasi, V. Barone, M. Cossi, R. Cammi, B.
Mennucci, C. Pomelli, C. Adamo, S. Clifford, J. Ochterski, G. A.
Petersson, P. Y. Ayala, Q. Cui, K. Morokuma, D. K. Malick,
A. D. Rabuck, K. Raghavachari, J. B. Foresman, J. Cioslowski, J.
www.angewandte.org
Angew. Chem. Int. Ed. 2005, 44, 253 –257
Angewandte
Chemie
V. Ortiz, B. B. Stefanov, G. Liu, A. Liashenko, P. Piskorz, I.
Komaromi, R. Gomperts, R. L. Martin, D. J. Fox, T. Keith, M. A.
Al-Laham, C. Y. Peng, A. Nanayakkara, C. Gonzalez, M.
Challacombe, P. M. W. Gill, B. G. Johnson, W. Chen, M. W.
Wong, J. L. Andres, M. Head-Gordon, E. S. Replogle, J. A.
Pople, Gaussian, Inc., Pittsburgh, PA, 1998.
[32] W. Kohn, L. J. Sham, Phys. Rev. 1965, 140, 1133.
[33] A. D. Becke, Phys. Rev. A 1988, 38, 3098.
[34] A. D. Becke, J. Chem. Phys. 1993, 98, 5648.
Angew. Chem. Int. Ed. 2005, 44, 253 –257
www.angewandte.org
2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
257
Документ
Категория
Без категории
Просмотров
1
Размер файла
118 Кб
Теги
0ц3, radical, sf5ox
1/--страниц
Пожаловаться на содержимое документа