Flash vacuum thermolysis of 4H-3,1-benzoxathiin-4-thione: UV-photoelectron spectroscopy characterization and quantum chemistry studies

Article abstract of DOI:10.1002/hlca.200890079

The mechanism of the reaction of 4H-3,1-benzoxathiin-4-thione (3) under flash vacuum thermolysis conditions has been studied by UV-photoelectron spectra. It was shown that in the first step of the reaction at 400° 3 underwent the Schoenberg - Newman - Kwart rearrangement to give 4H-1,3-benzodithiin-4-one (6). Increasing of the temperature to 650° resulted in the elimination of thioformaldehyde and the formation of benzothiet-2-one (1). Subsequent elevation of the temperature prompted presumably the ring opening of 1 to (6-thioxocyclohexa-2,4-dien-1-ylidene) methanone (7) (at 680°), which at 700° eliminated CO and underwent a Wolff-type ring contraction to give (cyclopenta-2,4-dien-1-ylidene)methanethione (2). UV-Photoelectron spectra were recorded at different steps of the reaction and analyzed considering the theoretical evaluation of ionization potentials.

Full text of DOI:10.1002/hlca.200890079

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Flash Vacuum Thermolysis of 4H-3,1-Benzoxathiin-4-thione:
UV-Photoelectron Spectroscopy Characterization and Quantum Chemistry
Studies
by Tomasz Drewnowskia)b), Anna Chrostowska*a), Stanisław Les´niak*b), Alain Dargelosa), and
Saïd Khayara)
a
´
) Institut Pluridisciplinaire de Recherche sur lꢀEnvironnement et les Materiaux UMR 5254,
´
´
Universite de Pau et des Pays de lꢀAdour, Av. de lꢀUniversite, BP 1155, F-64013 Pau Cedex
(e-mail: anna.chrostowska@univ-pau.fr)
b
´
´
´
´
) Department of Organic and Applied Chemistry, University of Łodz, 68 Narutowicza, PL-90-136 Łodz
(e-mail: slesniak@chemul.uni.lodz.pl)
The mechanism of the reaction of 4H-3,1-benzoxathiin-4-thione (3) under flash vacuum thermolysis
conditions has been studied by UV-photoelectron spectra. It was shown that in the first step of the
reaction at 4008 underwent the Schçnberg – Newman – Kwart rearrangement to give 4H-1,3-
3
benzodithiin-4-one (6). Increasing of the temperature to 6508 resulted in the elimination of
thioformaldehyde and the formation of benzothiet-2-one (1). Subsequent elevation of the temperature
prompted presumably the ring opening of 1 to (6-thioxocyclohexa-2,4-dien-1-ylidene)methanone (7) (at
6808), which at 7008 eliminated CO and underwent a Wolff-type ring contraction to give (cyclopenta-2,4-
dien-1-ylidene)methanethione (2). UV-Photoelectron spectra were recorded at different steps of the
reaction and analyzed considering the theoretical evaluation of ionization potentials.
Introduction. – Benzothiet-2-one (¼ 7-thiabicyclo[4.2.0]octa-1,3,5-trien-8-one; 1)
has been shown to be a transient intermediate in many photochemical and thermal
organic reactions. This product can be obtained by flash vacuum thermolysis (FVT) of
2-sulfanylbenzoic acid or benzo[b]thiophene-2,3-dione at 600 – 6108 [1], as well as
photolytically, starting either from 4H-1,2,3-benzothiadiazin-4-one [2] or from 2-
phenyl-4H-3,1-benzoxathiin-4-one [3]. 1 is stable only below À 208 in the solid state;
above this temperature, rapid polimerization, as well as partial di- and trimerization
takes place. Above 8008, the loss of CO from 1 and a Wolff-type ring contraction to give
(cyclopenta-2,4-dien-1-ylidene)methanethione (2) were mentioned [4] (Scheme 1).
It is noteworthy that the analogous 2H-naphtho[2,3-b]thiet-2-one was successfully
isolated and identified at room temperature [4]. Both thiet-2-ones were characterized
by IR, 1H- and 13C-NMR spectra [4], and, additionally, UV-photoelectron spectra of 1
were registered [1]. Although the more stable ring in 1 could exist in equilibrium with
its ring-opened valence tautomer, the latter has not been detected until now. In
contrast, the open keto-ketene form of the dioxygen analogue has been characterized
by photoelectron spectra [1].
Recently, we have shown that 1 could also be obtained by flash vacuum thermolysis
of 4H-3,1-benzoxathiin-4-thione (3) [5]. The present paper is mainly aimed at the
study of relevant details of the mechanism of this transformation.
ꢁ 2008 Verlag Helvetica Chimica Acta AG, Zürich

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Scheme 1
Results and Discussion. – The preparative FVT experiment of 3 with MeOH
trapping yielded 2-sulfanylbenzoic acid methyl ester as the sole product [5]. The
elimination of formaldehyde and the formation of the sulfanylbenzoic acid ester via the
reaction of MeOH with transient benzothiet-2-thione (¼ 7-thiabicyclo[4.2.0]octa-1,3,5-
triene-8-thione; 4) or its ring-opened isomer 6-thiocarbonyl-2,4-cyclohexadiene-1-
thione 5 has not been detected (Scheme 2).
Scheme 2
FVT of 3 in conjunction with variable-temperature UV-photoelectron spectral
detection has been applied to directly follow the progress of this reaction, and thus to
elucidate the mechanism of this transformation. In the first step of our experimental
study, the spectrum of 4H-3,1-benzoxathiin-4-thione (3) has been recorded at 3008
(Fig. 1). First, the broad band with three well distinguished bands at 8.2, 8.6 and 8.9 eV
is observed in the lower energy part of the spectrum. Then, a sharp and intense
ionization at 9.7 eV is followed by a broad and less intense one at 10.45 eV.
The interpretation of the photoelectron (PE) spectra is not straightforward,
therefore the theoretical estimation of ionization potentials (IP) has been carried

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Fig. 1. Photoelectron spectrum of 3 at 3008
out after full optimization of geometrical parameters of 31) and is displayed in
Table 1.
Considering these experimental and theoretical data for 3, the first IP at 8.2 eV
corresponds to the ejection of one electron from the S s-lone pair of the C¼S group, the
second IP at 8.6 eV reflects mainly the antibonding interaction of the S p-lone pair and
the p3 orbital of the aromatic ring, 8.9 eV IP appears as a shoulder and has been
attributed to the ionization of the C¼S bond. Two PE bands at 9.7 and 10.45 eV
correspond to the aromatic p electrons interacting with O and S lone pairs of the same
symmetry. In this case, the good coherence between experimental and theoretical
values should be underlined.
At 4308, the PES (photoelectron spectrum) has changed (Fig. 2), and the
appearance of three new ionizations at 8.45, 8.8, and 10.2 eV is accompanied with
modifications of the intensity of the bands at 9.4and 9.6 eV. The comparison of these
experimental data with the calculated ones of the thioketene 51) (for which the first two
IPs are expected in the range of ca. 7.2 – 7.7 eV; Table 2), or with those of 41) (for which
lower energy ionizations are expected at 8.2 – 8.4, 8.4 – 8.6, 9.2 – 9.3 eV; Table 3),
(supposed reaction path in Scheme 2), excludes their formation, considering the most
important fact, that the formaldehyde IP at 10.88 eV is not present in this spectrum.
1
)
The geometrical parameters are available as supporting material from the authors.

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Table 1. Calculated and Experimental IPs of 4H-3,1-Benzoxathiin-4-thione (3) (all values in eV, *DSCF,
**Exp. IP)
Molecular orbital
À eKS
6.20
TD-DFT
8.13*
ꢂCorrectedꢀ x ¼ 2.00
8.20**
OVGF
8.17
Exp.
8.2
6.69
8.56
8.69
8.44
8.6
7.048.82
9.04
8.69
8.9
8.08
8.45
9.80
10.08
10.45
9.91
9.7
10.13
10.34
10.45
Therefore, the first step of FVT of 3 at 4008 does neither lead to 5 or to 4. Thus, the
hypothesis that the first step of this reaction should correspond to the Schçnberg –
Newman – Kwart rearrangement [6] has been proposed (Scheme 3).
The analysis of the PES (Fig. 2) has been performed considering calculated
(Table 4) and experimental data for the rearranged molecule 6 (¼4H-1,3-benzodithiin-
4-one), and the new band at 8.45 eV has been attributed to the ionization of the S p-
lone pair. The second band at 8.8 eV corresponds to the ejection of an electron from the
orbital corresponding to the antibonding interaction between the second S lone pair
and the C¼O group (npS À pC¼O)), while the third PE band at 9.4eV is associated with
the antibonding interaction between S and O s-lone pairs. The fourth and fifth bands
are due to the ionization of the p-system of the aromatic ring (p3, p2 þ npSþ ). According
to the total energy comparison, 61) is more stable than 3 by 12.2 kcal/mol.
Further increase of the temperature allowed us to remark an important change in
the spectrum at 6508: appearance of the very sharp and intense band at 9.4eV ( Fig. 3),
corresponding to the ionization of the S s-lone pair of H2C¼S [7]; this fact confirms the
retro-Diels – Alder cleavage as presented in Scheme 3.

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Fig. 2. Comparison of the photoelectron spectra of 3 at 3008 and 4308
Fig. 3. Photoelectron spectrum of 3 at 6508

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Table 2. Calculated IPs of Thioketene 5 (all values in eV, *DSCF)
Molecular orbital
À eKS
5.83
TD-DFT
7.56*
ꢂCorrectedꢀ x ¼ 1.73
7.56*
OVGF
7.23
A’’
A’
5.86
7.86
7.68
9.62
7.59
9.59
7.63
9.36
A’’
A’’
A’
8.44
9.47
10.62
11.32
10.17
11.20
10.00
10.43
Scheme 3
For a reliable identification of these experimental data, the theoretical study has
started by the energy comparison of two isomers1), thus 1 is more stable than (6-thioxo-
2,4-cyclohexadien-1-ylidene)methanone (7) by only 9.9 kcal/mol, and the barrier
height of this transformation requires solely 10.1 kcal/mol (B3LYP/6-311G(d,p)).
According to the earlier work of Schweig [1], four main ionizations at 8.56, 9.94, 10.87,
and 11.76 eVare characteristic of 1, and indeed they are clearly visible in our spectrum
of 3 at 6508 (Fig. 3, Table 5). The first IP corresponds to the ejection of an electron
from the S-atom lone pair in antibonding interaction with p-electrons of the aromatic
ring. The second band contains two ionizations; the first one of s-symmetry reflects the

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Table 3. Calculated IPs of 4 (all values in eV, *DSCF)
Molecular orbital
À eKS
6.54
TD-DFT
8.41*
ꢂCorrectedꢀ x ¼ 1.87
8.41*
OVGF
8.16
A’’
A’
6.69
7.48
8.31
9.33
8.48
8.56
9.35
8.57
9.21
A’’
A’’
A’
9.27
10.23
10.18
10.06
11.2411.20
11.25
antibonding interaction of the S and O s-lone pairs, the second one is associated with
the p3 orbital. The third band corresponds to the antibonding interaction of the S p-lone
pair, C¼O group, and p2 orbital. The last one is associated with s-bond ionizations.
With a slight increase of the temperature (to 6808), the appearance of new bands at
8.15 eVand 10.2 eV has been noticed as well as the lowering of 9.94eV band intensity
(Fig. 4). Thus, the presence of the less stable ketene isomer 7 has been supposed.
In fact, on the basis of the time-dependent density functional theory (TD-DFT) and
Outer Valence Greenꢀs Function (OVGF) theoretical predictions of the IPs for 7
(Table 6), its PES observation cannot be excluded. In this case, the first band observed
at 8.15 eV should correspond to the ejection of an electron from the totally antibonding
combination of p-orbitals (pCÀ¼C À nS À nOp ) and the S-atom lone pair ionization nsS. The
p
band located at 10.2 eV should contain ionization of the p system: p3 À npO and the one
at 10.9 eV corresponds to p3 À pC¼S. Finally, the 11.8 eV PE band should reflect the S s-
lone pair in interaction with s-bonds of the molecule.

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Fig. 4. Photoelectron spectrum of 3 at 6808
Fig. 5. Photoelectron spectrum of 3 at 7708

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Table 4. Calculated and Experimental IPs of 6 (all values in eV, *DSCF, **Exp. IP)
Molecular orbital
À eKS
6.56
TD-DFT
8.44*
ꢂCorrectedꢀ x ¼ 1.89
8.45**
OVGF
8.30
Exp.
8.45
7.13
7.44
8.77
9.03
9.02
9.33
9.02
9.30
8.8
9.4
7.67
8.33
9.35
9.56
9.88
9.6
10.31
10.22
10.03
10.2
Scheme 4
In the next step of this thermal decomposition, 7 may lose C¼O and generate 2 as
suggested in Scheme 4.
In fact, the spectrum corresponding to the FVTof 3 at 7708 (Fig. 5) contains the CO
ionization at 14.03 eV. The first three IPs observed in this spectrum are in good
agreement with the previously published data [1], and are equal to 8.5 eV, 8.7 eV and
11.14eV. The band at 10.5 eV corresponds to the H 2S IP and indicates rather high
instability of these intermediates and secondary reaction pathways. Moreover, the final
state leading to the formation of CO and 2 is 26.3 kcal/mol energetically less stable than
7 and thus, corroborates the hypothesis of the latter formation at 6808.

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Table 5. Calculated and Experimental IPs of 1 (all values in eV, *DSCF, **Exp. IP)
Molecular orbital
À eKS
6.40
TD-DFT
8.41*
ꢂCorrectedꢀ x ¼ 2.16
8.56**
OVGF
8.13
Exp.
8.56
A’’
A’
7.69
9.75
8.85
9.59
9.94
A’’
A’’
A’
7.88
8.66
9.60
9.78
10.79
11.60
10.049.79
10.82
9.94
10.52
11.68
10.87
11.76
11.76
As a first step of the studied reaction, the Schçnberg – Newman – Kwart rearrange-
ment [6] has been postulated. To improve this hypothesis by an independent
experiment, 2-benzofuran-1(3H)-thione (8) has been synthesized and submitted to
the FVT-PES experiment (Scheme 5).
The spectrum of the starting compound has been recorded at 2008 (Fig. 6), and its
interpretation has been done, as previously, by comparison with theoretical estimation
of ionization potentials (Table 7).
Calculated IPs have allowed the assignment of the first PE band at 8.5 eV to the
ejection of an electron from the HOMO, which corresponds to the S lone pair in the s-
plane. The second band at 8.9 eV corresponds to the C¼S group ionization, while the
third one at 9.7 eV is attributed to the ejection of an electron from the p3 orbital of the
aromatic ring. The two next bands localized at 10.2 and 11.9 eV are significant of the
ionization of the p2 aromatic ring orbital in antibonding interaction with the S p-lone
pair and s-bond electron ejection, respectively. In this case, the third and fourth TD-
DFT IPs are strongly incoherent with the rest of the calculated values.

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Fig. 6. Photoelectron spectrum of 8 at 2008
Fig. 7. Photoelectron spectrum of 8 at 6408

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Table 6. Calculated and Supposed Experimental IPs of 7 (all values in eV, *DSCF, **Exp. IP)
Molecular orbital
À eKS
5.89
TD-DFT
7.77*
ꢂCorrectedꢀ x ¼ 2.26
8.15**
OVGF
7.41
Exp.
8.15
A’’
A’
6.00
8.02
8.26
7.82
8.15
A’’
A’’
A’
8.32
8.62
9.77
10.26
10.33
11.81
10.58
10.88
12.03
9.99
10.28
11.75
10.2
10.9
11.8
Scheme 5
At 6408, the PES has changed (Fig. 7). Considering the B3LYP/6-311G(d,p) total
energy values for 81) and 91), 2-benzothiophen-1(3H)-one (9) is more stable than 2-
benzofuran-1(3H)-thione (8) by 14.3 kcal/mol. By comparison with the theoretical
evaluation of the IPs of 9 (Table 8), the two first very close IPs at 8.8 and 8.95 eV have
been attributed to the ejection of an electron from the orbital corresponding to the
antibonding interaction of S and O lone pairs in p and s plane, respectively. The third
and fourth IPs are attributed to the ejection of an electron from the p aromatic ring

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Table 7. Calculated and Experimental IPs of 8 (all values in eV, *DSCF, **Exp. IP)
Molecular orbital
À eKS
6.16
TD-DFT
8.34*
ꢂCorrectedꢀ x ¼ 2.34OVGF
8.5**
Exp.
8.19
8.5
8.9
6.76
8.56
9.10
8.50
7.66
8.03
8.86
9.56
10.00
10.37
9.58
9.92
9.7
10.2
9.71
11.27
12.05
11.9411.9
bonds (p2 and p3), while the fifth PE band at 11.8 eV reflects mainly the S s-lone pair
ionization. Particularly good agreement of calculated values and experimental data has
to be underlined, and thus confirms the formation of 9 by thermal rearrangement of 8.
In summary, the detailed mechanism of the thermal decomposition of 3 has been
proposed as shown in Scheme 6.
Scheme 6
The following conclusions can be drawn:
a) The first IP of the studied precursors 3 and 8 corresponds to the ejection of an
electron from the s-lone pair of the S atom of the C¼S group.

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Table 8. Calculated and Experimental IPs of 9 (all values in eV, *DSCF, **Exp. IP)
Molecular orbital
À eKS
7.00
TD-DFT
9.01*
ꢂCorrectedꢀ x ¼ 1.80
8.80**
OVGF
9.148.8
Exp.
7.30
9.26
9.10
9.30
9.28
8.95
7.50
7.65
9.28
9.349.4
5
9.649.4
9.59
9.7
9.56
11.61
11.36
11.69
11.8
b) The energetic position of the C¼S bond is the same in the two precursors (3 and 8).
c) The first step of the studied reactions occurs via a Schçnberg – Newman – Kwart
rearrangement.
d) The S lone pair in the rearranged compounds 6 and 9 is subjected to the strong
electron withdrawing effect of the C¼O group and its IP is equal to 8.8 eV.
e) UV-PES Experiments in conjunction with quantum calculations of IPs confirm the
formation of 1 and 2 as thermal decomposition intermediates in FVT of 3;
formation of the less stable 7 is supposed.
The replacement of the O-atom in the C¼O group of lactons by an S-atom results in
an unexpected course of the FVT.
T. D. and A. C. are grateful to the French Ministry of Foreign and European Affairs for its Eiffel
Doctorate Scholarship, the French Ministry of High Education and Research for financial support and
`
acknowledge Mr. Patrick Baylere for very efficient technical assistance. The authors thank the Rector of
´
´
the University of Łodz for financial support (Grant 505/740).

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Experimental Part
1. Starting Material. 4H-3,1-Benzoxathiin-4-thione (3) and 2-benzofuran-1(3H)-thione (8) were
prepared following the literature procedures [5] and [8], resp.
2. Thermolysis and Photoelectron Spectra. The photoelectron spectra (PES) were recorded on a
home-built, three-part spectrometer equipped with a spherical analyzer (Omicron), main body device
(Meca2000), HeI radiation source (Focus), and monitored by a microcomputer supplemented with a
digitalÀanalog converter. The spectra were calibrated against the auto-ionization of Xe at 12.13 and
13.45 eV, and N2 at 15.59 and 16.98 eV. They contain 2000 points and are accurate to 0.1 eV. Sample
manipulations were carried out in a thermolysis oven attached directly to the inlet probe; the distance
between the oven exit and the ionization head does not exceed 1 cm. Compounds 3 and 8 were slowly
vaporized under low pressure (10 – 7 Torr in the ionization chamber) directly in the oven, and the gaseous
thermolysate was continuously analyzed.
3. Computational Details. The calculations were performed using the Gaussian 98 [9] program
packages. The 6-311G(d,p) basis set was used for all calculations since the inclusion of polarization
functions is necessary for the accurate description of the neutral molecules containing third row atom and
their cations. Geometry optimizations were carried out at the density functional theory (DFT) [10][11]
level of theory with the B3LYP [12 – 14] functional and confirmed as true minima via frequency
analysis1). Ionization energies were calculated with DSCF-DFTwhich means that separate self-consistent
field (SCF) calculations are performed to optimize the orbitals of the ground-state and the appropriate
ionic state (IE ¼ Ecation À Eneut.mol.). The time-dependent density functional theory (TD-DFT) [15][16]
approach provides a first principles method for the calculation of excitation energies within a density
functional context, taking into account the low lying ion calculated by DSCF method. The vertical
ionization potentials were also calculated at the ab initio level according to the outer valence greenꢀs
function (OVGF) [17][18] method. In this case, the effects of electron correlation and reorganization are
including beyond the Hartree – Fock (HF) approximation and the self-energy part was expanded up to
third order. To compare the ionization potentials resulting from these rigorous methods of calculation,
we proceeded also to the currently used estimation of ionization potentials. Indeed, recent works [19 – 23]
have shown that eKi S could be linked up to experimental vertical ionization potentials (IPv) by uniform
shift x ¼jÀ ei(HOMO) À IPevxp j . This approach gives a remarkable agreement with experimental values
and is justified by the fact that the first calculated vertical ionization potential lies very close to
experimental values. Stowasser and Hoffman [24] have shown that the localization of Kohn – Sham (KS)
orbitals are very similar to those obtained after HF calculations.
DFT has been shown to predict various molecular properties successfully [12 – 14]. The advantages
of the most employed method of calculations of the first ionization energies (DSCF-DFT calculations)
have been thoroughly demonstrated [25 – 28]. On the other hand, the frequently used estimation of IPs
by ꢂshiftingꢀ of calculated KF energies (a not very rigorous process, but nicely working) has also proved its
efficacy. Nevertheless, we have to consider that each theoretical method of approaching ionization
potentials is limited by the calculation procedure. In the DSCF method, we have to take into account that
the single-configuration approximation is not valid when several ions of the same symmetry are near in
energy. For the TD-DFT approach, the configuration interaction process is based on the quality of the
evaluation of the low lying ion described by DSCF method. In the OVGF calculation, the quality of the
theoretical results depends on the validity of the HF approximation.
REFERENCES
[1] R. Schulz, A. Schweig, Tetrahedron Lett. 1979, 20, 59.
[2] A. T. Fanning Jr., G. R. Bickford, T. D. Roberts, J. Am Chem. Soc. 1972, 94, 8505.
[3] O. L. Chapman, C. L. McIntosh, J. Am. Chem. Soc. 1970, 92, 7001.
[4] C. Wentrup, H. Bender, G. Gross, J. Org. Chem. 1987, 52, 3838.
´
´
[5] T. Drewnowski, S. Lesniak, G. Mloston, R. Siedlecka, J. Skarz˙ewski, Helv. Chim. Acta 2006, 89, 991.
[6] S. Scheithauer, R. Mayer, ꢂThio- and Dithiocarboxylic Acids and Their Derivativesꢀ, in ꢂTopics in
Sulfur Chemistryꢀ, Ed. A. Senning, Vol. 4, Georg Thieme Verlag, Stuttgart, 1979.

Helvetica Chimica Acta – Vol. 91 (2008)
781
[7] B. Solouki, P. Rosmus, H. Bock, J. Am. Chem. Soc. 1976, 98, 6054.
[8] A. G. M. Barrett, A. C. Lee, J. Org. Chem. 1992, 57, 2818.
[9] 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. Stratman, 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. V. Ortiz,
A. G. Baboul, B. B. Stefanov, G. Liu, A. Liashenko, P. Piskorz, I. Komaromi, R. Gomperts, R.
Martin, D. J. Fox, D. T. Keith, M. A. Al-Laham, C. Y. Peng, A. Nanayakkara, C. Gonzalez, M.
Challacombe, P. M. W. Gill, B. Jonhson, W. Chen, M. W. Wong, J. L. Andres, M. Head-Gordon, E. S.
Replogle, J. A. Pople, Gaussian 98, Revision A.7, Gaussian, Inc., Pittsburgh PA, 1998.
[10] R. G. Parr, W. Yang, ꢂFunctional Theory of Atoms and Moleculesꢀ, Oxford University Press, New
York, 1989.
[11] M. J. Frish, G. W. Trucks, J. R. Cheeseman, ꢂSystematic Model Chemistries Based on Density
Functional Theory: Comparison with Traditional Models and with Experimentꢀ, in: ꢂRecent
Development and Applications of Modern Density Functional Theory, Theoretical and Computa-
tional Chemistryꢀ, Ed. J. M. Semminario, Vol. 4, Elsevier, 1996, pp. 679 – 707.
[12] A. D. Becke, Phys. Rev. 1988, A38, 3098.
[13] A. D. Becke, J. Chem. Phys. 1993, 98, 5648.
[14] C. Lee, W. Yang, R. G. Parr, Phys. Rev. 1988, B37, 785.
[15] R. E. Stratmann, G. E. Scuseria, M. J. Frisch, J. Chem. Phys. 1998, 109, 8218.
[16] M. E. Casida, C. Jamorski, K. C. Casida, D. R. Salahub, J. Chem. Phys. 1998, 108, 4439.
[17] W. von Niessen, J. Schirmer, L. S. Cederbaum, Comput. Phys. Rep. 1984, 1, 57.
[18] J. V. Ortiz, J. Chem. Phys. 1988, 89, 6348.
[19] A. J. Arduengo III, H. Bock, H. Chen, M. Denk, A. D. Dixon, J. C. Green, W. A. Herrmann, N. L.
Jones, M. Wagner, R. West, J. Am. Chem. Soc. 1994, 116, 6641.
[20] H. M. Muchall, N. H. Werstiuk, J. L. Pitters, M. S. Workentin, Tetrahedron 1999, 55, 3767.
[21] H. M. Muchall, N. H. Werstiuk, B. Choudury, J. Ma, J. Warkentin, J. Pezacki, Can. J. Chem. 1998, 76,
238.
[22] H. M. Muchall, N. H. Werstiuk, B. Choudury, Can. J. Chem. 1998, 76, 221.
[23] H. M. Muchall, P. Rademacher, J. Mol. Struct. 1998, 471, 189.
[24] R. Stowasser, R. Hoffmann, J. Am. Chem. Soc. 1999, 121, 3414.
´
[25] S. Joanteguy, G. Pfister-Guillouzo, H. Chermette, J. Phys. Chem., A 1999, 103, 3505.
[26] A. Chrostowska, K. Miqueu, G. Pfister-Guillouzo, E. Briard, J. Levillain, J.-L. Ripoll, J. Mol.
Spectrosc. 2001, 205, 323.
`
´
[27] R. Bartnik, P. Baylere, A. Chrostowska, A. Galindo, S. Lesniak, G. Pfister-Guillouzo, Eur. J. Org.
Chem. 2003, 2475.
[28] V. Lemierre, A. Chrostowska, A. Dargelos, H. Chermette, J. Phys. Chem., A 2005, 109, 8348.
Received November 26, 2007