404
L. Du et al. / Journal of Molecular Structure 875 (2008) 400–405
nonbonding orbital raises sharp and narrow peak. The ion-
ization of nS lone pair in C6H5C(O)OSCCl3 is similar to
those in other sulfur(II)-containing compounds, such as
H2S (10.48 eV), CH3SH (9.46 eV), CH3CH2SH (9.36 eV),
and CH3SCH3 (8.72 eV) [24]. In these molecules, the first
ionization energies are all caused by the ionization of nS
lone pair. The ionization energy caused by the ionization
of nS lone pair in C6H5C(O)OSCCl3 is larger than those
of homonuclear dichalcogens, such as HSSCl (9.266 eV)
[25], CH3SSCH3 (8.96 eV) [24], and FC(O)SSCH3
(9.0 eV) [26].
The bands at high energy region are caused by more
complicated ionization processes, and difficult for
assignment.
4. Conclusion
A derivative of benzoic acid, C6H5C(O)OSCCl3 was het-
erogeneously generated and characterized by photoelectron
spectroscopy with complement of quantum chemical calcu-
lations. The dihedral angle dCSOC of C6H5C(O)OSCCl3 is
determined to be 104.4ꢀ (MP2/6-311++G(d,p)). The first
vertical ionization energy is measured to be 9.46 eV. The
HOMO of C6H5C(O)OSCCl3 is mainly localized on the p
orbital of benzene ring.
The second group of bands in the spectrum (Fig. 3) is
composed of two peaks at 10.89 and 10.96 eV, respectively.
The peak at 10.89 eV is caused by the ionization of Cl 3p
nonbonding electron at CCl3 moiety. In the photoelectron
spectrum of CCl3CCl3, the ionization energy caused by nCl
is 11.22 eV [24], which is slightly higher than
C6H5C(O)OSCCl3. According to the theoretical calcula-
tions, the peak at 10.96 eV comes from the ionization pro-
Acknowledgement
This project was supported by the 973 program of Min-
istry of Science and Technology of China (No.
2006CB403701), Hundred Talents Fund and Knowledge
Innovation Program of the Chinese Academy of Sciences
(Grant No. KZCX2-YW-205), the National Natural Sci-
ence Foundation of China (Contract Nos. 20577052,
20673123, 20473094, 20503035).
cesses of {64a(nS, nCl)}ꢁ1 and {63a(nO(C@O))}ꢁ1
.
The band at 11.44 eV is due to the ionization of an elec-
tron from the 3p nonbonding orbital of Cl atom in CCl3
moiety. The electron ionization from the p orbital of
C@O moiety results in the band at 11.94 eV in the spec-
trum. It is lower than the ionization energies coming from
the same ionization process of HC(O)OCH3 (14.10 eV),
CH3COOH (12.05 eV), and CH3C(O)CH3 (12.59 eV) [24].
The band centered at 12.25 eV is caused by the ionization
of electron from the orbitals mainly localized at the CCl3
moiety and the r orbital at benzene ring. In benzene, the
ionization from r orbital corresponds to the ionization
energy of 11.53 eV [24], which is lower than that in
C6H5C(O)OSCCl3. The band at 12.39 eV can be assigned
to the ionization of nonbonding electron of O atom at
S–O bond. Compared with the ionization of nS at S-O
bond, the lone pair electron of O atom is more difficult
to be ionized.
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