Conformational properties and spectroscopic characterization of m-chlorosulfinylaniline

Article abstract of DOI:10.1016/j.molstruc.2016.11.024

In the present work we report a combined experimental and theoretical study on the molecular structure and vibrational spectra of m-chlorosulfinylaniline. The substance was characterized by ¹H and ¹³C NMR and GC-mass spectrometry as

Full text of DOI:10.1016/j.molstruc.2016.11.024

Accepted Manuscript
Conformational properties and spectroscopic characterization of
m-chlorosulfinylaniline
Doly M. Chemes, Diego J. Alonso de Armiño, Edgardo H. Cutin, Norma L. Robles
PII:
S0022-2860(16)31180-2
10.1016/j.molstruc.2016.11.024
MOLSTR 23125
DOI:
Reference:
To appear in: Journal of Molecular Structure
Received Date: 24 June 2016
Revised Date: 3 November 2016
Accepted Date: 7 November 2016
Please cite this article as: D.M. Chemes, D.J. Alonso de Armiño, E.H. Cutin, N.L. Robles,
Conformational properties and spectroscopic characterization of m-chlorosulfinylaniline, Journal of
Molecular Structure (2016), doi: 10.1016/j.molstruc.2016.11.024.
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Graphical Abstract

ACCEPTED MANUSCRIPT
Conformational Properties and Spectroscopic Characterization
of m-chlorosulfinylaniline
Doly M. Chemes,a Diego J. Alonso de Armiño,a Edgardo H. Cutinb and Norma L. Roblesb*
a
Instituto de Química Física – Facultad de Bioquímica, Química y Farmacia, Universidad
Nacional de Tucumán. San Lorenzo 456, 4000 Tucumán, República Argentina.
b INQUINOA UNT CONICET. Ayacucho 471, 4000 Tucumán, República Argentina.
nrobles@herrera.unt.edu.ar
ABSTRACT
In the present work, we report a combined experimental and theoretical study on the
molecular structure and vibrational spectra of m-chlorosulfinylaniline. The substance was
1
13
characterized by H and C NMR and GC-mass spectrometry as well as by FT-IR and
Raman spectroscopy. Experimental results were complemented with theoretical
calculations at the B3LYP and MP2 levels of theory for electronic structure and harmonic
oscillator and Vibrational Self-consistent Field levels of theory for vibrational structure.
The observed and calculated frequencies were found to be in good agreement. Natural
Bond Orbital analysis provides an explanation of the stability of the molecule and its
electronic properties upon charge delocalization.
Keywords m-Chlorosulfinylamine; vibrational spectroscopy; quantum chemical
calculations; conformational properties.
1. Introduction
Our main interest in the study of N-sulfinylamines of general formula R‒N=S=O (R =
aromatic ring) is focused on their vibrational, structural and conformational properties. The
parent compound, N-sulfinylamine was synthesized in 1890 by Michaelis et al [1, 2] and its
structure was determined in 1999 [3]. The conformational preferences, vibrational spectra
and pre-resonant Raman properties of compounds including the−N=S=O group have been
extensively studied [4]. Due to the nonlinearity of the N=S=O group, these compounds can
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in principle be found in one of two configurations, syn or anti. Interestingly however, all of
the molecules studied so far have been experimentally observed only in the syn orientation
[5−10].
The cumulated π system of the N=S=O group confers these molecules some interesting
properties in pre-resonant Raman spectroscopy, as it has been shown to be quite useful as a
conformational sensor for excited states [4]. Spectroscopic analyses of this kind are
relatively scarce, though, as their low stability usually comes in the way of this kind of
experiments.
There is an interesting range of applications for this kind of molecules, as they can
participate in cycloaddition reactions through their N=S bond. The hydrolysis of N-
sulfinylamines is also quite interesting, as the kinetics of these reactions depend very
strongly on the identity of the R substituent and can range from explosive, in the case of
ClNSO, for example, to quite mild in the case of N-sulfinylanilines [11].
There has been a considerable effort in the past decades directed to the study of R‒N=S=O
general family of molecules and a fair number of works have been published on this subject
over the years [12]. However, there are comparatively few works on the N-sulfinylaniline
family, with early work centered on N-sulfinylaniline (C6H5–N=S=O) [3] and the sterically
hindered derivatives O=S=N–C6H3[(CH–CH3)]2-2,6 and O=S=N–C6H3(CH3–CH2)2-2,6 by
Romano et. al. [12], and more recently studies focusing on fluorine-substituted N-
sulfinilanilines by our group [13‒15] employing a wide variety of spectroscopic techniques.
In all cases the N=S=O group was observed to acquire a syn configuration (see Scheme I).
Scheme I. Syn and anti forms with respect to the C‒N single and S=O double bond.
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In this work we present the second part of an ongoing series featuring chlorosulfinylaniline
isomers [16]. In this opportunity, we present a detailed analysis of the vibrational and
structural properties of m-chlorosulfinylaniline, a member of the aromatic branch of the N-
sulfinylamine family of compounds. A detailed characterization is performed on the basis
of 1H, 13C, NMR spectroscopy and GC-mass spectrometry, followed by a vibrational study
using FTIR and Raman spectroscopies, supported by quantum chemical calculations at
various levels of electronic and vibrational structure theories. These results complement
those reported previously by several research groups [17–19]. We analyze the effect of the
halogen substitution in the meta position with respect of the sulfinyl group of the aromatic
ring, and compare it with the para isomer previously reported by our group, with particular
attention to the NSO marker bands.
2. Computational Details
The analyses of the potential energy surface of m-chlorosulfinylaniline and optimization of
the structural parameters of stable minima found were performed by using the
GAUSSIAN03 program [20]. Vibrational frequencies as well as Raman and IR intensities
were calculated using a combination of several electronic and vibrational structure
methodologies. In particular, for electronic structure calculations we used gradient
corrected Density Functional Theory (DFT) with the three-parameter hybrid functional
(B3) [21] for the exchange part and the Lee-Yang-Parr (LYP) correlation function [22] in
combination with 6-311+G(df), 6-311++G(df,pd) and cc-pVTZ basis sets, as well as
second order Moller-Plesset Perturbation Theory (MP2), in combination with the cc-pVDZ
basis set.Natural population analysis NBO [23], as implemented in the GAUSSIAN03
program, was performed together with the Gauge-including atomic orbital (GIAO) method
[24]. In addition to these calculations for the m-chlorosulfinylaniline, the B3LYP/6-
311+G(df) method was applied also to the parent sulfinylaniline and to p-
chlorosulfinylaniline compounds for the sake of comparison.
In the particular case of vibrational structure calculations, in addition to the customary
harmonic oscillator approximation for the vibrational energies and wavefunctions we
performed advanced vibrational structure calculations using the vibrational self-consistent
field (VSCF) ansatz, recently implemented in the QUMVIA software package [15],
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developed by our group. VSCF is a mean-field, variational iterative method for the
calculation of the vibrational wavefunction, entirely analogous to the Hartree-Fock method
in electronic structure theory. Following is a brief summary of VSCF theory. A more
detailed account can be found elsewhere [25‒27].
The vibrational Schrödinger equation for a molecular system expressed in rectilinear
normal coordinates {qi} can be formulated, neglecting rotational coupling, as follows:
ꢌ
ꢁ
ꢄꢂ
ꢄꢅꢂ
ꢈ ꢋ
ꢈ ꢋ
ꢈ ꢋ
ꢀ− ꢃ
+ ꢇ ꢅꢉꢊ ꢎ ꢏꢐ ꢅꢉꢊ = ꢑꢐꢏꢐ ꢅꢉꢊ
ꢂ
ꢆ
ꢆꢍꢁ
With
ꢌ
ꢈ ꢋ
ꢈ ꢋ
ꢏꢐ ꢅꢉꢊ = ꢒ ꢓꢆ,ꢐ ꢅꢉꢊ
ꢆꢍꢁ
The vibrational wavefunction is represented as a Hartree product, this is, a product of one-
dimensional, single-mode wavefunctions or “modals” {φi}, (with i=1,..,f) which in turn, are
functions of the mass weighted normal coordinates qi, in analogy to orbitals in electronic
structure theory. Using this assumption and the variational principle it is possible to obtain
the VSCF equations for each modal.
ꢔ
ꢈ ꢋ ꢈ ꢋ
ꢈ ꢋꢗ ꢈ ꢋ
ꢕ°ꢆ ꢅꢆ + ꢖꢆ ꢅꢆ ꢓꢆ ꢅꢆ = ꢘꢆꢓꢆ ꢅꢆ
ꢌ
ꢌ
ꢈ ꢋ
ꢈ ꢋ
ꢖꢆ ꢅꢆ = ꢙꢒ ꢓꢚ ꢜꢇꢝ ꢅꢉꢊ ꢜ ꢒ ꢓꢚꢞ
ꢚꢛꢆ
ꢚꢛꢆ
Hio is the core Hamiltonian for mode “i”, consisting of the kinetic energy and the diagonal
potential and υi is the mean field potential.
Because the solutions (the modals) are necessary to compute the mean field potential, the
VSCF equations must be solved iteratively until self-consistency.
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Distributed Gaussian functions are used as a basis set [28]. The nuclear potential energy
surface (PES) is approximated using a quartic force field (QFF) with a 3-mode coupling
representation [29], i.e. three normal modes are allowed to couple simultaneously. Third
and fourth order force constants are obtained by numerical differentiation of Hessian
matrices calculated analytically using a separate electronic structure software
(GAUSSIAN03, in our case) at MP2/cc-pVDZ and B3LYP/6-311++G(df,pd) electronic
structure level of theory. Molecular structures were optimized using a “very strict”
convergence criterion, following a frequency calculation to obtain normal modes, harmonic
frequencies and hessian matrix in GAUSSIAN03. With these data, a series of
conformations distorted along each normal mode were generated by QUMVIA, and hessian
matrices were calculated for each of these using GAUSSIAN03. Finally these Hessian
matrices were used to compute 3-mode coupling QFFusing QUMVIA. Sixteen distributed
Gaussian basis functions positioned at 16 scaled Gauss-Hermite quadrature points were
used for each normal mode. A VSCF energy convergence criterion of 10-9 Hartrees was
used.
3. Experimental details
3.1 Synthesis
The preparation of R‒N=S=O compounds follows the method proposed by Michaelis et al
[1]. m-Chlorosulfinylaniline was prepared using a 1:2:5 molar relation of the corresponding
chlorinated aniline, thionyl chloride and benzene as the reaction solvent, respectively. m-
Chloroaniline (3.63g; 28.48mmol ) and benzene (13.20 g; 169 mmol) were placed in a
closed three neck round bottom flask equipped with a Liebig condenser which was sealed
with CaCl2 trap. Thionyl chloride (9.80g; 82.30nmmol) was added drop wise to the
mixture. To prevent the interaction with air humidity, the reaction was carried out in
nitrogen atmosphere. A vigorous reaction took place and the mixture was continuously
stirred and heated for 8 hours at 80‒85 °C until a dark solution was obtained. The liquid
mixture obtained was purified by several distillation cycles in order to get a dark green
liquid as the final product with ca. 97% yield. Its purity was controlled by 1H and 13C NMR
spectroscopy (CDCl3 solvent, TMS internal reference), GC-Mass Spectrometry, IR and
Raman spectroscopy. The substance is highly hygroscopic and corrosive.
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3.2 Raman and FT-IR measurement
The Raman spectrum of the liquid was recorded at room temperature in the range 3500–50
cm-1 by employing a diode-pump, solid state 532 nm green laser with 9.0 mW power at the
sample for excitation in a Thermoscientific DXR Smart Raman instrument equipped with
CCD detector. The resolution was 4 cm-1 with a grating groove density of 900 lines/mm. A
confocal aperture of 50 ꢀm slit was used and 60 expositions of 1 s were accumulated for
the sample in order to achieve sufficient signal to noise ratio. The samples were handled in
Pyrex capillaries at room temperature.
The FT-IR spectra of m-chlorosulfinylaniline were recorded between 3500 and 400 cm-1 at
room temperature using a Perkin-Elmer GX1 Fourier Transform infrared instrument, by
placing the liquid sample between KRS-5 windows (1cm-1 spectral resolution).
3.3 NMR and GC/MS measurements
Varian Unity 200 spectrometer was used for NMR studies. 1H and 13C NMR spectra
were recorded at 200 MHz and 50 MHz, respectively (chemical shifts expressed in
parts per million ppm or ∂ relative to tetramethylsilane, TMS). The number of scans
was appropriate to generate good quality spectra for analysis.
The GC-MS analysis was carried out using a Model Trace GC Ultra gas
chromatograph coupled to a Polaris Q mass spectrometer with an ion-trap analyzer
using a DB-5 capillary column. Split-less injection was used for this study. The
initial temperature of the oven was 60°C. After maintaining that temperature for 3
min, the oven temperature was increased at a rate of 15°C/min to reach a final oven
temperature of 250°C. The final temperature was maintained for 5 min and the total
run time was 20 min. Helium was used as carrier gas. The mass spectrometer was
operated in the electron ionization scan mode (range, m/z: 60-180). Quantification of
the peaks was based on peak area. In the total-ion chromatogram and the mass
spectra of m-chlorosulfinylaniline were observed an intense signal at 9.56 min (97 %
relative area) and a m/z 173 relation (base peak of molecular ion), respectively,
which account for the presence of the studied molecule.
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4. Results and discussion
4.1 Molecular geometry, structural properties and NBO analysis
As it was already observed for the fluorinated isomer of -chlorosulfinylaniline [14]
and previously for -chlorosulfinylaniline itself [30], the geometry adopted by the
m
m
N=S=O group determines that two different structures with very similar energy
might be feasible, one with the chlorine atom closer to the oxygen atom of the
N=S=O group than the other, which shows an opposite disposition of the meta
substituent. The relative energy values predicted with the B3LYP/6-311+G(df)
approximation confirms this assumption, with ꢁE = 0.16 kcal.mol-1. A 5.48
kcal.mol-1 energy barrier for rotation around the C−N bond was predicted between
both forms by this approximation. The optimized molecular structure of the most
stable conformer of m-chlorosulfinylaniline obtained at this level of theory is shown
in Figure 1. Such small energy difference between both forms would prevent their
being identified separately in the vibrational and NMR spectra. The optimized
molecular structure reveals that the meta-substituted N=S=O group is coplanar with
the benzene ring.
The structural parameters calculated using different basis sets are presented in Table
1. In order to confirm the assumption that the most stable conformer possesses syn
geometry, the potential energy function for the coordinate of rotation around the
N=S bond was determined by a relaxed scan of the C‒N=S=O dihedral angle in
steps of 30° at the B3LYP/6-311+G(df) level of theory. The results predicted a syn
conformer with CS symmetry as the global minimum of the potential energy surface
and the anti conformation as a local minimum with ∆E° (anti
and ∆G° (anti
syn) = 6.78 kcal.mol-1. Figure 2 show the calculated potential function
-
syn) = 7.26 kcal.mol-1
-
for rotation around the N=S bond obtained with the B3LYP/6-311++G(df,pd)
approximation. The higher stability of the sterically unfavourable syn conformation
of the C‒N=S=O group observed for all sulfinylanilines reported hitherto may be
rationalized by orbital interactions. A Natural Bond Orbital (NBO) analysis
performed also at the DFT/B3LYP/6-311+G(df) level of theory suggests that two
orbital interactions between nitrogen and sulfur lone pairs with vicinal antibonding
‒O) and lp (S) →σ* (C‒N) (anomeric effects) stabilize
orbitals, i.e. lp (N) →σ* (S
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the syn conformer relative (15.34 kcal.mol-1and 9.84 kcal.mol-1) to the anti structure
(5.57 kcal.mol-1and 0.73 kcal.mol-1).
4.2 Vibrational assignment
Table 2 and Fig 3 show vibrational spectral assignment and experimental FT-IR and Raman
spectra of a liquid sample of m-chlorosulfinylaniline, respectively. For the assignment of
the vibrational bands we used a combination of several theoretical techniques for the
prediction of vibrational spectra. Harmonic oscillator (HO) vibrational frequencies and
intensities were obtained using potential energy surfaces at the B3LYP/6-311++G(df,pd),
B3LYP/cc-pVTZ and MP2/cc-pVDZ electronic levels of theory, whereas Vibrational Self-
Consistent Field vibrational energies and wavefunctions were obtained using potential
energy surfaces at the B3LYP/6-311++G(df,pd) and MP2/cc-pVDZ electronic levels of
15
theory. In addition, theoretical N substitution was used to help identifying the vibrational
modes expected for the N=S=O group. As it was already observed for molecules containing
the N=S=O group, the N=S and S=O stretching modes are strongly coupled, therefore the
vibrations will be described as symmetric and antisymmetric stretching modes for the
N=S=O group.
Previous studies showed that there is a strong dependence between the vibrational
frequencies of this group and the substituent bonded to the N atom [4], so the assignment
must be carefully considered. Many studies have focused in the past on the vibrational
aspects of the related sulfinylaniline molecule [18, 31‒34]. In particular, Stufkens [33]
reported a very detailed analysis on the Raman spectra of sulfinylaniline and its 15N
isotopologue, and found that 7 bands (at 1299, 1284, 1161, 1034, 1020, 747 and 638 cm-1)
had significant nitrogen contributions. Building on this work, Romano et. al. [3] used a
combination of higher resolution IR, pre-resonant and normal Raman spectroscopies, and
assigned the antisymmetric and symmetric stretching modes to the 1298 cm-1 and 1163 cm-
1 bands, respectively. Moreover, equivalent assignments were made at 1298/1174 cm-1 for
the O=S=N–C6H3(CH2–CH3)2-2,6 derivative and more tentatively at 1287/1173 cm-1 for the
O=S=N–C6H3[CH(CH3)2]2-2,6 derivative. In all cases these bands showed medium to
strong intensity in both Raman and IR spectra. It is to be expected that the equivalent bands
for m-chlorosulfinylaniline will not be observed far from these values. However, some
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differences were already observed for the symmetric N=S=O stretching mode in the
halogen substituted derivatives p-, m- and o-fluorosulfinylaniline series [13–15] and
recently for p-chlorosulfinylaniline [16]. In the present study, theoretical calculations at the
harmonic oscillator level predict N=S=O group stretching modes at 1312/1058 cm-1
(B3LYP/cc-pVTZ potential), 1310/1051 cm-1 (B3LYP/6-311++G(df,pd) potential) and
1307/1016 cm-1 (MP2/cc-pVDZ) for the antisymmetric and symmetric modes, respectively.
More advanced theoretical calculations at the vibrational self-consistent field (VSCF)
vibrational structure level of theory, using a 3-mode coupling quartic force field predict
these bands at 1295/1041 cm-1(B3LYP/6-311++G(df,pd) potential) and 1294/1006 cm-1
(MP2/cc-pVDZ potential). The N=S=O antisymmetric and symmetric stretching modes of
m-chlorosulfinylaniline were therefore assigned to the1298 and 1039 cm-1 (IR) and 1304
and 1043cm-1 (Raman) bands, respectively. A slight blue shift of the N=S=O stretching
modes in the meta with respect to the para isomer (1297/1031 cm-1, respectively) is to be
expected, due to mesomeric effects of the chlorine lone pair with the –N=S=O group (See
Scheme II).
S
S
S
S
N
N
O
N
N
O
O
O
Cl
Cl
Cl
Cl
Scheme II. Different mesomeric structures for
m-chlorosulfinylaniline
The in plane deformation of the N=S=O group had been described as a very weak
signal in the vibrational spectra of the fluorosulfinylaniline serie and also for
p-
chlorosulfinylaniline. For the meta isomer this signal was no discernible in the
experimental spectra, but the theoretical calculations predicted it at 641, 638 and 634
cm-1 according to B3LYP/cc-pVTZ, B3LYP/6-311++G(df,pd) and MP2/cc-VDZ,
respectively, in good agreement with the observed values for those related
compounds. On the other hand, the out of plane deformation was observed at 440
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cm-1 in the IR spectrum with theoretical calculations predicting it at 410, 411 and
414 cm-1HO//B3LYP/cc-pVTZ, HO//B3LYP/6-311++G(df,pd) and HO//MP2/cc-
pVDZ, respectively, and at 406 and 412 cm-1 for VSCF//B3LYP/6-311++G(df,pd)
and VSCF//MP2/cc-pVDZ levels of theory, respectively.
We now address the analysis of the C‒N stretching mode, assigned at 786 cm-1 in the
infrared spectra, with theoretical calculations predicting it at 702, 694 and 674 cm-1 at the
HO//B3LYP/cc-pVTZ, HO//B3LYP/6-311++G(df,pd) and HO//MP2/cc-pVDZ levels of
theory respectively and at 711 and 669 cm-1 for VSCF//B3LYP/6-311++G(df,pd) and
VSCF//MP2/cc-pVDZ, respectively for anharmonic vibrational calculations. A comparison
with the corresponding mode in the para isomer (770 cm-1, IR) shows that it is slightly
blue-shifted in the meta compound with respect to the former. This trend is different from
the observed for the corresponding isomers in the fluorinated series, where the red-shift
shown in the vibrational spectra for the band belonging to the C‒N stretching mode
accounts for mesomeric effects of the fluorine atom, which are now proved to be different
in the chlorinated specie. The different trend may be explained through orbital interactions,
as evidenced by the Natural Bond Orbital analysis performed for the present study.
Mesomeric effects affect predominantly o- and p- possitions with respect to the halogen
atom. By simply writing the resonance structures for the molecules, we can see that it
confers a partial double bond character over the C−N bond when it is situated at those
positions with respect to the halogen. In our calculations, this effect is observed to be far
more important in the case of the fluorinated series than in the chlorinated series. In the p-
and o-fluoro substituted isomers the C−N stretching signal was observed at larger
frequency values with respect to the m- isomer, while for the chlorinated series, the
opposite was true. We explain these differences by invoking the stronger mesomeric effects
observed for the fluorinated series as explained above. In other words, the strong
mesomeric effects in fluorinated compounds blue-shift the C−N frequencies for o- and p-
isomers so much, that they appear at higher frequency than the m- isomer, but when these
effects become weaker, as in the chlorinated series, C−N stretching bands for o- and p-
isomers appear at lower frequencies than for the m- isomer.
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In agreement to the previous reasoning, the C‒Cl stretching mode follows this trend as it
was observed in the present study at 825 cm-1 in comparison with the 836 cm-1 frequency
found in the p- isomer.
4.3 NMR profile
We used a combination of nuclear magnetic resonance (NMR) spectroscopy and
mass-spectrometry for the molecular structure determination using theoretical
methods to help in the assignments. The molecular structure of m-
chlorosulfinylaniline was optimized at the B3LYP/6-311+G(df) level of theory
followed by 13C and 1H chemical shift calculations through the GIAO method which
were subsequently compared to the experimental chemical shift values (see Tables 3
and 4). The GIAO method is one of the most common approaches for calculating
nuclear magnetic shielding tensors. Aromatic carbons show signals in the 100 to 150
ppm range [35] while signals belonging to aromatic protons are usually found
around 7.00‒8.00 ppm. In a correlative order, the signals observed for C1 to C6 were
142.90, 130.10, 134.71, 130.42, 129.90 and 125.10 ppm; on the other hand, the
hydrogen atoms H1, H4, H3 and H2 showed signals at 7.80, 7.70, 7.32 and 7.32
ppm, respectively. The external magnetic field experienced by carbon nuclei is
affected by the electronegativity of atoms/groups bonded therefore the influence of
the chlorine atom and N=S=O group must be considered. The assignment proposed
is based on shifts reported for similar molecules [13–16]. The increase in the
chemical shift observed for C1 and C3 with respect to the other carbon atoms might
be attributed to the presence of the chlorine and the N=S=O group attached to the
aromatic ring.
5. Conclusions
The present article features the study of the conformational and vibrational
properties of
m-chlorosulfinylaniline, and is the second in an ongoing series
dedicated to chlorine monosubstituted sulfinilanyline series of compounds. In the
present work we performed the conformational analysis and characterization of
m-
13
chlorosulfinylaniline by nuclear magnetic resonance spectroscopy (1H and C), gas
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chromatography/mass spectrometry, vibrational spectra and quantum chemical
calculations at different levels of theory, thus complementing partial results reported
previously. The title compound was obtained through the reaction
and SOCl2, obtaining a highly hygroscopic and corrosive substance.
m-chloroaniline
As observed with all sulfinylamine derivatives, theoretical calculations strongly
indicate that only the syn conformation of the N=S=O moiety can be observed in the
gas phase, implying a global Cs symmetry, in agreement with the properties
observed for the parent sulfinylaniline. Moreover, Natural Bond Oribital analysis
showed that this thermodynamic preference is due to strong stabilizing annomeric
interactions for the syn configuration that are lower in the anti conformer.
In comparison with the parent sulfinylaniline and p-chlorosulfinylaniline, previously
reported, the vibrational fundamentals of the N=S=O group, as well as the C‒N and
C‒Cl stretching modes, show some interesting shifts that offer some clues on the
effect of substitution on the molecular electronic structure, and some possible
rationalizations are explored in this work. A complete assignment of the fundamental
vibrational transition bands is proposed on the basis of present and previous
experimental work, and strongly supported by theoretical calculations at harmonic
and anharmonic vibrational levels of theory. With regard to this later point, the
vibrational self-consistent field (VSCF) ansatz as implemented in the QUMVIA
software package, developed by our group, proved to be quite useful in the
assignment of fundamental bands, as well as for the identification of possible
overtones and combination bands, and presents itself as a much more physically
motivated method than the widespread practice of using simple ad-hoc scaling
factors for harmonic oscillator vibrational frequencies, as the former is capable of
handling non-trivial effects of anharmonicity, that cannot be modeled by more
traditional techniques.
Acknowledgements
Authors acknowledge CONICET (Consejo Nacional de Investigaciones Científicas y
Técnicas) and UNT (Universidad Nacional de Tucumán) for the financial support. Authors
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also kindly acknowledge staff from LISA (Laboratorio de Investigación
ServiciosAnalíticos) for NMR and GC/MS measurements.
y
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16

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Figure Captions
Scheme I. Syn and anti forms with respect to the C‒N single and S=O double bond.
Scheme II. Different mesomeric structures for m-chlorosulfinylaniline
Fig. 1. Molecular model of the syn conformer of m-chlorosulfinylaniline.
Fig. 2. Calculated potential function for rotation around the N=S bond (B3LYP/6-
311++G(df,pd)).
Fig. 3. Experimental infrared and Raman spectra of
m-chlorosulfinylaniline. Top:
infrared spectrum of a liquid sample held between KRS-5 windows; bottom: room
temperature Raman spectrum of a liquid sample (* impurity).

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Table 1. Calculated geometric parameters for the m-chlorosulfinylaniline.
Structural parameters
m-chlorosulfinylaniline
B3LYP/
B3LYP/
6-311++G(df,pd) cc-pVTZ
C‒Cl
1.753
1.081
1.408
1.385
1.391
1.380
1.530
1.483
119.8
132.4
119.1
121.1
124.3
115.9
119.1
0.0
1.751
C‒H
1.077
1.406
1.384
1.390
1.391
1.535
1.478
119.7
132.0
119.0
121.1
1.243
116.0
119.1
0.0
C1‒C2(6)
C2(5)‒C3(6)
C4‒C3(5)
C1‒N
N=S
S=O
N=S=O
C1‒N=S
C2‒C1‒C6
C3‒C4‒C5
C2‒C1‒N
C6‒C1‒N
Cl‒C‒C
C1‒N=S=O
a Bond lengths in Å and angles in degrees. Mean values are given for parameters that are
not unique. For atom numbering see Fig. 1.

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Table 2. Experimental and calculated wavenumbers of the m-chlorosulfinylaniline and
tentative assignments of main fundamental vibrational modes.
Experimental b
Theoretical c
B3LYP/
6-311++G(df,pd)
Mode
Approximate description a
B3LYP/ cc-pVTZ
HO
MP2/cc-pVDZ
VSCF
IR (liq.) Raman (liq.)
HO
VSCF
HO
3278
3254
3247
3228
1634
1615
1501
1473
1443
1307
1279
1203
1173
1128
1098
1016
1001
956
ν1 (A') C–H Stretch.
3088 m
-
-
3239(5)[<1]
3210(2)[56]
3205(1)[23]
3183(5)[26]
3233(4)[3]
3042
3070
3077
3121
3075
3059
1608
1590
1480
1445
1424
1294
1265
1198
1171
1121
1092
1006
992
ν2(A') C–H Stretch.
3073 m
3211(1)[40]
ν3(A') C–H Stretch.
3068 m
3034 m
1581 m
1563 s
1472 s
1416 m
1334 vw
1298 s
1286 s
1168 vs
-
-
3206(<1)[17] 3038
3185(3)[19] 3012
ν4(A') C–H Stretch.
-
ν5(A') C–C Stretch. + C–H Def.
ν6(A') C–C Stretch. + C–H Def.
ν7(A') C–C Stretch. + C–H Def.
ν8(A') C–C Stretch. + C–H Def.
ν9(A') C–C Stretch.
1582 vs
1621(<1)[78] 1619(<1)[66] 1595
1596(34)[6] 1593(28)[4] 1570
1504(29)[20] 1502(21)[16] 1484
1564 sh
1467 m
1419 w
1446(8)[9]
1442(6)[8]
1426
1338
-
1350(4)[49]
1349(1)[32]
ν10(A') N=S=O Asym. Stretch.
ν11(A') C–H Def. i.p.
1304 vs
1312(38)[86] 1310(24)[63] 1295
1298(9)[100] 1299(8)[100] 1284
1284 s
ν12(A') C–C Stretch.
1169 vs
1190(16)[<1]
1191(4)[2]
1188
ν13(A') Ring Def. i.p.
ν14(A') C–H Def i.p.
-
1176(100)[43] 1162(100)[28] 1148
1122(11)[<1] 1122(10)[<1] 1116
1100 m
1077 m
1039 m
998 w
-
1100 w
ν15(A') C–H Def. i.p.
-
1099(14)[2]
1058(22)[24] 1051(21)[22] 1041
1016(4)[17] 1013(3)[16] 1003
1005(<1)[<1] 1006(<1)[<1] 1029
1098(10)[1]
1092
ν16(A') N=S=O Symm. Stretch.
ν17(A') Ring Def. i.p.
ν18(A'') C–H Def. o.o.p.
ν19(A'') C–H Def. o.o.p.
ν20(A'') C–H Def. o.o.p.
ν21(A') C–Cl Stretch.
1043 s
999 s
982 w
995
906 w
880 s
825 m
804 sh
786 m
-
-
943(9)[<1]
931(6)[<1]
836(45)[3]
814(27)[<1]
702(16)[<1]
682(3)[6]
939(6)[<1]
927(7)[<1]
835(37)[3]
810(26)[<1]
694(11)[<1]
681(2)[5]
969
952
828
845
711
676
633
598
468
444
406
377
370
237
207
157
114
80
895
926
-
877
900
825 w
824
816
ν22(A'') C–H Def. o.o.p.
ν23(A') C–N Stretch
806 w
781
830
-
674
669
ν24(A') Ring Def.
-
643
691
ν25(A') N=S=O Def. i.p.
ν26(A'') C–H Def. o.o.p.
ν27(A'') C–H Def. o.o.p.
ν28(A') Ring Def.
-
-
641(5)[2]
638(5)[2]
634
631
677 vs
484 m
-
670 w
608(2)[<1]
461(1)[<1]
447(10)[1]
410(3)[2]
606(2)[<1]
461(<1)[<1]
446(8)[1]
575
600
-
444
458
-
434
433
ν29(A'') N=S=O Def. oop
ν30(A'') C Skeletal Def.
ν31(A') C–Cl Def. i.p.
ν32(A') Skeletal Def.
440 s
410 m
-
441 w
411(2)[2]
414
412
413 m
375(5)[<1]
369(3)[<1]
240(6)[2]
371(5)[]<1
368(3)[<1]
237(4)[15]
200(<1)[<1]
141(<1)[<1]
112(<1)[1]
56(4)[<1]
360
362
-
356
360
-
243 w
240
239
ν33(A'') C–Cl Def. o.o.p.
ν34(A'') Torsion N=S=O
ν35(A') Skeletal Def.
-
207 m
201(<1)[<1]
142(2)[<1]
114(1)[1]
199
208
-
-
-
-
141
156
-
123
123
ν36(A'') Def. C‒N=S
-
57(<1)[<1]
51
73
a Stretch.: stretching; Def.: deformation; Asym.: asymmetric; Sym.: symmetric; sh:
shoulder; i.p.: in phase; o.o.p.: out of phase; b s: strong; vs: very strong; m: medium; w:
weak; vw: very weak c Relative infrared intensities in parentheses, normalized to 100%;
Relative Raman activities between brackets, normalized to 100%.

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Table 3. 13C NMR experimental (50 MHz, CDCl3, TMS) and calculated data of m-
chlorosulfinylaniline.
C a
Chemical shift δ [ppm]
Experimental Theoreticalb
C(6)
C(5)
C(4)
C(3)
C(2)
C(1)
125.10
129.90
130.42
134.71
130.10
142.90
129.85
132.09
136.17
148.77
132.56
151.88
a For atom numbering see Fig. 1; b Calculated chemical shifts (GIAO method) using
B3LYP/6-311+G(df) approximation.

ACCEPTED MANUSCRIPT
Table 4.1H NMR experimental (200 MHz) and calculated data of the m-chlorosulfinylaniline.
H a
δ [ppm]
δ [ppm]
Experimental Theoretical b
H1
H4
H3
H2
7.80
7.70
7.32
7.32
8.84
7.06
7.04
6.95
a For atom numbering see Fig. 1; b Calculated chemical shifts (GIAO method) using B3LYP/6-
311+G(df) approximation.

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Figure 1

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Figure 2

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Figure 3

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•
A complete assignment of the FT-IR, Raman, NMR and GC/MS spectra was
performed.
•
•
•
•
Conformational properties confirm the trend observed for related compounds.
Theoretical results are in good agreement with experimental data.
The Cl substitutent modifies the frequency of signals in the experimental spectra.
Full vibrational assignment is performed and compared to similar molecules.