Experimental and computational studies on the 1:1 complex of anthranilic acid with p-toluenesulfonic acid

Article abstract of DOI:10.1080/10426507.2013.777724

The proton-transfer compound (3) was synthesized in good yields by the reaction of anthranilic acid with p-toluenesulfonic acid. It was characterized by elemental analysis, infrared spectroscopy, and X-ray single-crystal determination. The crystal structure analysis of 2-carboxyanilinium p-toulenesulfonate (3) has revealed a one-dimensional hydrogen-bonded network structure, involving the tosylate anion, the carboxyl group, and the ammonium group. The H(N)···O distances range from 1.97 to 2.23 A. The molecular geometry and vibrational frequencies of 3 were calculated using the ab-initio method (HF) with the 6-31G(d) and 6-31+G(d,p) basis sets. The computed results indicate that the optimized geometry reproduces the crystal structure well, and the assignments of fundamental vibrations also agree well with the theoretical frequencies. The intermolecular proton transfer process between the ionic (3) and nonionic (4) structures was also investigated with the theoretical computations. The nonionic form (4) is energetically more stable than the ionic form (3) and TS(3→4) by 9.76 and 7.01 kcal/mol, respectively, including the zero-point vibrational energy correction at the HF/6-31+G(d,p) level. In addition, the atomic charges, the molecular electrostatic potentials, the nucleus-independent chemical shifts, and the frontier molecular orbitals of 3 were carried out at the HF/6-31+G(d,p) level of theory. Supplementary materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfer, and Silicon and the Related Elements for the following free supplemental files: Additional figures and tables

Full text of DOI:10.1080/10426507.2013.777724

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EXPERIMENTAL AND COMPUTATIONAL STUDIES ON
THE 1:1 COMPLEX OF ANTHRANILIC ACID WITH p-
TOLUENESULFONIC ACID
İbrahim Şen a , Cem Burak Yildiz a b , Hülya Kara c & Akın Azizoglu a
a Department of Chemistry, Faculty of Arts and Sciences, University of Balikesir, TR, 10145,
Balikesir, Turkey
b Department of Chemistry, Faculty of Arts and Sciences, University of Aksaray, TR, 68100,
Aksaray, Turkey
c Department of Physics, Faculty of Arts and Sciences, University of Balikesir, TR, 10145,
Balikesir, Turkey
Accepted author version posted online: 05 Apr 2013.
To cite this article: Phosphorus, Sulfur, and Silicon and the Related Elements (2013): EXPERIMENTAL AND COMPUTATIONAL
STUDIES ON THE 1:1 COMPLEX OF ANTHRANILIC ACID WITH p-TOLUENESULFONIC ACID, Phosphorus, Sulfur, and Silicon and the
Related Elements, DOI: 10.1080/10426507.2013.777724
To link to this article: http://dx.doi.org/10.1080/10426507.2013.777724
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EXPERIMENTAL AND COMPUTATIONAL STUDIES ON THE 1:1 COMPLEX OF
ANTHRANILIC ACID WITH p-TOLUENESULFONIC ACID
İbrahim Şen1, Cem Burak Yildiz1,2, Hülya Kara3 and Akın Azizoglu1,*
1Department of Chemistry, Faculty of Arts and Sciences, University of Balikesir, TR-10145,
Balikesir, Turkey
2Department of Chemistry, Faculty of Arts and Sciences, University of Aksaray, TR-68100,
Aksaray, Turkey
3 Department of Physics, Faculty of Arts and Sciences, University of Balikesir, TR-10145,
Balikesir, Turkey
Abstract
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The proton-transfer compound (3) was synthesized in good yields by the reaction of anthranilic
acid with p-toluenesulfonic acid. It was characterized by elemental analysis, infrared
spectroscopy and X-ray single-crystal determination. The crystal structure analysis of 2-
carboxyanilinium p-toulenesulfonate (3) has revealed a one-dimensional hydrogen-bonded
network structure, involving the tosylate anion, the carboxyl group and the ammonium group.
The H(N)∙∙∙O distances range from 1,97 to 2,23 Å. The molecular geometry and vibrational
frequencies of 3 were calculated using the ab-initio method (HF) with the 6−31G(d) and 6-
31+G(d,p) basis sets. The computed results indicate that the optimized geometry reproduces the
crystal structure well, and the assignments of fundamental vibrations also agree well with the
theoretical frequencies. The intermolecular proton transfer process between the ionic (3) and
nonionic (4) structures was also investigated with the theoretical computations. The nonionic
form (4) is energetically more stable than the ionic form (3) and TS(3→4) by 9.76 and 7.01
kcal/mol, including the zero-point vibrational energy correction at the HF/6-31+G(d,p) level. In
addition, the atomic charges, the molecular electrostatic potentials, the nucleus-independent
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chemical shifts, and the frontier molecular orbitals of 3 were carried out at the HF/6-31+G(d,p)
level of theory.
Keywords: Proton transfer compound; FTIR spectra; crystal structure; Hartree-Fock method;
NICS analysis
[Supplementary materials are available for this article. Go to the publisher’s online
edition of Phosphorus, Sulfer, and Silicon and the Related Elements for the following
free supplemental files: Additional figures and tables.]
<AQ> Editorial work on your manuscript has created a file of supplemental materials
that will be available on-line only.</AQ>
Received ….. 2012; accepted ….2012
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Address correspondence to Akın Azizoglu, Department of Chemistry, Faculty of Arts and
Sciences,
University
of
Balikesir,
TR-10145,
Balikesir,
Turkey,
E-mail:
azizoglu@balikesir.edu.tr
INTRODUCTION
The chemistry of anthranilic acid (2-aminobenzoic acid, 1) is of importance in medicinal
and biological chemistry because it is the biochemical precursor to the amino acid tryptophan, as
well as a catabolic product of tryptophan in animals.1-3 It is also integrated into many alkaloids
isolated from plants. Like other amino acids, anthranilic acid is amphoteric. Due to the electron
donating effect of the amino group anthranilic acid is a weaker acid than benzoic acid. It also
contains both a hydrogen bond acceptor and a donor that are conjugated. As a base, anthranilic
acid is much weaker than aniline because of the pronounced electron-withdrawing effect of the
carboxyl function.1
In the past few decades, there has been an enormous amount of interest in proton transfer
self-associated systems because intra- or intermolecular proton transfer exhibits potential for the
control of a variety of physical properties of organic solids.4-12 The intermolecular bond in such
systems may consist of ion-pairing, hydrogen bonding, hydrophobic or hydrophilic, host-guest,
- stacking, and donor-acceptor interactions. In an ideal case, one or combination of some of
these intermolecular bonding processes may result in the formation of specific and spontaneous
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self-associated forms of the desired aggregate. Although there have been several experimental
and theoretical studies on proton-transfer between a carboxylic acid and an amine,9-12 the crystal
structures of proton-transfer compounds with toluene-4-sulfonic acid (or p-toluenesulfonic acid,
PTSA, 2) are uncommon, possibly because of the absence of interactive functional substituent
groups to promote secondary hydrogen-bonding extension.13-14
Herein, we have prepared a novel proton-transfer compound obtained from anthranilic
acid and PTSA (Scheme 1). The optimal geometry and the detailed vibrational analysis of the
title ion pair (3) with the help of theoretical and spectroscopic methods have been also reported
in detail. Moreover, the molecular electrostatic potential maps, natural bond orbitals, frontier
molecular orbitals, and nucleus-independent chemical shifts (NICS) have been calculated at the
HF/6-31G(d) and the HF/6-31+G(d,p) levels. These studies are valuable for providing insight
into molecular properties of proton-transfer compounds.
RESULTS AND DISCUSSION
Description of the Crystal Structure
Table 1 lists the experimental parameters used for data collection and determination of the
structure (3). The crystal structure of the 1:1 proton-transfer compound of anthranilic acid with
+
PTSA (C7H8NO2 .C7H7O3S), 3, is also depicted in detail (Fig.1). Hydrogen bond motifs are
commonly used as a way of guiding the interactions between molecules. It is important to
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understand what a likely outcome is for functional group interactions between molecules. As can
be seen from Fig.2, the N-H∙∙∙O(C) and N-H∙∙∙O(S) intramolecular hydrogen bonds and the N-
H∙∙∙O(S), and O-H∙∙∙O(S) type intermolecular hydrogen bonds are formed in 3. Three hydrogen
donors of the protonated amine group give direct hydrogen-bonding associations, with three of
the sulfonate O-atom acceptors from three independent PTSA anions [N∙∙∙O distances: N1∙∙∙O5i
= 2.8475(17), N1∙∙∙O3ii =2.7725(17) and N1∙∙∙O4 = 2.9751(17) Å; symmetry codes: (i) [-x, -y, 1-
z], (ii) [1-x, -y, 1-z]. Moreover, the O2∙∙∙O4iii =2.6392(16) [iii = -1+x, y, z] and N1∙∙∙O1=
2.6565(17) hydrogen bonds are formed in 3. These result in a linear polymer structure extending
along the a axis.
Table 1
Figure 1
Figure 2
The hydrogen bonded geometry and details are listed in Table 2. For the complex (3),
where the interacting units appear, the N-H…O hydrogen bonds are formed between PTSA and
anthranilic acid. Analysis of hydrogen bonds in 3 reveals that all potential donor/acceptor groups
are involved in intermolecular interactions. The delocalization in complex (3) involves the weak
interaction of the N(1)-H(1C) bonding with the S(1)-O(4) anti-bonding. This interaction effects
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the stabilization of complex (3), by very low energy, 0.17 kcal/mol, computed by the NBO
analysis.
Table 2
Optimized geometries
The ionic (3) and nonionic (4) structures were optimized at the HF/6-31G(d) and the
HF/6-31+G(d,p) levels. The calculated geometrical parameters of 3 and 4 are summarized in
Table 3 in accordance with its atom numbering scheme, shown in Fig. 2. It can be indicated for
the structural data of 3 that there is a rather good agreement between our theoretical calculations
and the experimental ones (Table 3). Especially, the calculated value of O(4)-H(1C) (1.830 Å)
distance is found to be much shorter than the X-ray data of 2.176 Å for 3, whereas that of N(1)-
H(1C) (1.032 Å) bond length is a little longer than the experimental one 0.910 Å at the level of
HF/6-31+G(d,p) theory. The discrepancy between the experimental (X-ray) and calculated
values for the atomic coordinates might result from the different environments of a molecule in
the experimental crystalline state and in the theoretical gas phase. However, it may be stated that
the modeling techniques applied in the present work properly reflect the main properties of the
actual structure and can be successfully applied for predicting the features of the title molecule 3.
Table 3
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The transition structure (TS3→4) for the proton-transfer between the ionic (3) and
nonionic (4) structures were determined successfully, and their relative energies were also
calculated at the HF/6-31+G(d,p) level (Fig. 3). In other words, the intermolecular proton
transfer process 3→TS→4 was investigated with the theoretical computations at the gas phase.
Because of the migration of a hydrogen atom from atom N1 to atom O4, some changes are
observed between 3 and 4. The distance between atoms O4 and H(1C) decreases upon the proton
transfer 3→TS→4. The N1—H(1C) and O4—H(1C) distances are found to be 1.032 Å and
1.830 Å for 3, 1.190 Å and 1.282 Å for TS, and 1.919 Å and 0.968 Å for 4, respectively (Table
3). Besides, the nonionic form (4) is energetically more stable than the ionic form (3) by 9.76
kcal/mol, including the zero-point vibrational energy correction at the HF/6-31+G(d,p) level. The
activation energy barrier for the proton-transfer of PTSA to anthranilic acid is also found to be
quite low, by 7.01 kcal/mol (Fig. 3). From X-ray measurements, the complex (3) is found to be
in the ionic form, whereas in the gas phase the charge separation is destabilized by the absence of
intermolecular bonding interactions from the surrounding media.
Figure 3
Vibrational spectra
The FT-IR spectrum of the title ion-pair (3) was recorded in the 4000–400 cm-1 region
using KBr pellets on a Perkin-Elmer 1600 series FTIR spectrophotometer. Harmonic vibrational
frequencies of 3 were also computed at the HF/6-31G(d) and the HF/6-31+G(d,p) levels. The
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vibrational band assignments were carried out using the GaussView molecular visualization
program. In order to facilitate assignment of the observed peaks, we have analyzed the
vibrational frequencies and compared our theoretical calculation for 3 with the experimental
results (see supplemental data Table S1). The assignment of the experimental frequencies are
based on the observed band frequencies in the infrared spectrum of this species confirmed by
establishing “one to one” correlation between experiment and theory. In total, there are 102
vibrations from 12 to 4044 cm–1 at the RHF/6-31G(d) level, 5 to 4113 cm–1 at the RHF/6-
31+G(d,p) level. As it is seen from Table S1, the agreement between the experimental and
calculated frequencies is reasonably good, especially considering that no scaling is employed.
The hydroxyl vibrations are likely to be the most sensitive to the environment, so they
show pronounced shifts in the spectra of the hydrogen bonded species. The experimental OH-
stretching vibrations were observed at around 3500 cm−1. However, the theoretical values of O-
H-stretching modes are found to be larger than the experimental one and this implies that the H
atom has an intermolecular hydrogen bonding.15 Besides, aromatic primary amines display two
medium intensity absorption bands: the one near 3500 cm-1 corresponds to the asymmetrical and
the other, near 3400 cm-1, to symmetrical N-H stretching modes.16 In the ion-pair (3), the bands
found at 3478 (calculated at 3681 cm-1) and 3195 cm-1 (calculated at 3248 cm-1) correspond to
the asymmetric and symmetric stretches in the experimental IR spectrum, respectively. The
lowering of N-H stretching wavenumbers can be attributed to the intermolecular N-H···O
interaction.
The C=O stretching frequencies usually lie in the region between 2000 and 1500 cm-1.
Various other vibrations, such as C=C, C=N stretching and N-H bending vibrations, also occur in
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this region. However, the C=O stretching is normally more intense than any other vibrations in
this region. The position of C=O stretching depends upon conjugation, hydrogen bonding and the
size of the ring to which it is attached. In the IR spectrum of 3, the ν(C=O) mode was computed
at 1980.9 cm−1 and 1956.0 cm−1, with the HF/6-31G(d) and HF/6-31+G(d,p) theory of level,
respectively, this mode is observed at 1712 cm−1 as a very strong band in the IR spectrum. Due
to the association of molecules in the solid phase the observed C=O stretching frequency is lower
than the calculated ones.
Atomic charges
The calculation of effective atomic charges plays an important role in the application of
quantum chemical calculations to molecular systems.17,18 Main atomic charges also affect the
reactivity of molecules. Atomic charges of the title complex (3) has been calculated with help of
natural bond orbital (NBO) analysis at HF/6-31G(d) and HF/6-31+G(d,p) levels given in Table
S2. Generally, the theoretical results show that the sulfur atom and oxygen atom (O5) of sulfite
group have the highest positive (+2.690) and negative charge (-1.148) on 3 at the HF/6-
31+G(d,p) method, respectively. It is noticed that the carbon atom attached to nitrogen and
oxygen atoms (C2 and C7) in both levels is an electron-deficient atom (i.e. it possesses positive
charge due to the electronegative character). However, the high negative values are those that are
present at nitrogen and oxygen, in the order: N1, O2, and O1. The remaining carbon atoms
possess negative electronic charge. The magnitude of the hydrogen atomic charges is found to be
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only positive and is arranged in an order from 0.222 to 0.520 for the complex 3. From the
calculated results, it will also be possible to say to the change to charge distribution by a change
in the basis sets. The charges depend on the basis set and are changed due to the polarization and
diffuse functions used herein.
Molecular electrostatic potential
The molecular electrostatic potential (MEP) is used widely for deciding sites molecular
reactivity, intermolecular interactions, molecular recognition, nucleophilic and electrophilic
reactions, as well as hydrogen-bonding interactions.19 To predict reactive sites for electrophilic
and nucleophilic attack for the title molecule, MEP was calculated by applying the HF method
and the 6-31+G(d,p) basis set for the optimized geometry. The negative (red) regions of MEP
were related to the electrophilic reactivity and the positive (blue) regions to nucleophilic
reactivity depicted in Fig. S1. As can be seen from the figure, the negative regions of the title
-
structures were observed around the SO3 part of C7H7O3S, whereas a maximum positive region
+
+
is localized on the NH3 part of C7H8NO2 for the complex 3 at the HF/6-31+G(d,p) level.
Moreover, there are two possible sites on the title compound for electrophilic attack. The
negative regions are mainly over the O3 and O5 atoms. These results provide information
concerning the region where the compound can have intra- or intermolecular interaction and
metallic bonding. Hence, the MEP map confirms the existence of intra- and intermolecular
interactions observed in the solid state.
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Frontier molecular orbitals
The frontier molecular orbitals (highest occupied molecular orbital-HOMO and lowest
unoccupied molecular orbital-LUMO) are the main orbitals taking part in chemical reactions.20
The HOMO energy characterizes the ability of electron donating, LUMO energy characterizes
the ability of electron accepting, and the gap between HOMO and LUMO characterizes the
molecular chemical stability. It is known that the HOMO-LUMO gap also play an important role
in the electric and optical properties, as well as in UV-Vis spectra and chemical reactions.21-26 As
it can be seen from Fig. S2, HOMO of 3 is mainly on C7H7O3S part, whereas LUMO of the
+
structure substantially localized on C7H8NO2 part of title molecule. The values of the energy
separation between the HOMO and LUMO for 3, 4, and TS, also are 0.358, 0.381, and 0.425 eV
at HF/6-31+G(d,p) theory of level, respectively. Molecular orbital coefficients analyses based on
their optimized geometries indicate that the frontier molecular orbitals are mainly composed of
-atomic orbitals, so the electronic transitions are mainly derived from the contribution of bands
–*.
Nucleus-Independent chemical shifts (NICS)
Aromaticity (aromatic) is considered as one of the most important concepts in modern
organic chemistry.27 The simplest criterion for aromatic compounds is that the presence of cyclic
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conjugated π-systems containing the proper number of π-electrons. In 1996, Schleyer proposed a
simple and efficient probe for aromaticity: Nucleus-independent chemical shift (NICS), which is
the computed value of the negative magnetic shielding at some selected point in space, generally,
at a ring or cage center.28 The theoretical HF/6-31+G(d) method was applied by Scheleyer for the
computation of aromaticities for a series of aromatic, antiaromatic, or nonaromatic compounds; it
was proposed that negative NICS values indicate aromaticity (-9.7 for benzene), whereas large
positive NICS values indicate antiaromaticity (27.6 for cyclobutadiene) and small NICS values
denote nonaromaticity (-2.2 for cyclohexane). NICS data for the present systems were computed
with the HF/6-31+G(d,p) method at the ring center (NICS(0)). The justification of the applied
method was performed by obtaining -9.7, 28.8, and -2.4 for benzene, cyclobutadiene, and
cyclohexane, respectively.
+
The NICS(0) data calculated at the ring center indicate that C7H7O3S and C7H8NO2 part
of the complex (3) have an aromatic character with -10.3 for Bq1 and -10.9 for Bq2, respectively,
(See supplemental data Fig. S3), while the NICS values of p-toluenesulfonic acid and anthranilic
acid are found to be -10.4 for Bq3 and -8.6 for Bq4, respectively (see supplemental data Fig. S4).
The NICS value can be affected by other structural features that are not directly related to the
aromatic ring current. In fact, the data depict that NICS value of C7H7O3S part (Bq1) of
+
complex (3) are almost equal to that of p-toluenesulfonic acid, whereas NICS value of C7H8NO2
part (Bq2) is by only 2.3 lower than to that of anthranilic acid (Table S3).
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CONCLUSION
Success with PTSA is unusual, considering that crystal structures of proton-
transfer Lewis base compounds with PTSA are uncommon, possibly because of the absence of
interactive secondary substituent functional groups to promote hydrogen-bonding extension. In
this work, PTSA and anthranilic acid forms a crystalline complex of the stoichiometry 1:1. The
X-ray and IR spectral data for the title compound show that one proton from PTSA is transferred
to anthranilic acid and the molecules are linked by the N–H···O hydrogen bonds. The
comparisons between the theoretical results and the X-ray single-crystal data indicate that both
HF/6-31G(d) and HF/6-31+G(d,p) level are adequate to reproduce the experimental geometric
parameters. The vibrational frequencies of 3 are precisely assigned to its molecular structure with
the aid of the theoretical calculations at the HF/6-31G(d) and the HF/6-31+G(d,p) levels, in
which the experimental and theoretical results support each other. The MEP map shows that the
-
negative potential site is on the SO3 part of C7H7O3S while the positive potential sites are
+
+
around the NH3 part of C7H8NO2 for the complex 3 at the HF/6-31+G(d,p) level. These sites
give information about the region from where the compound (3) can have intermolecular
interactions and metallic bonding.
EXPERIMENTAL
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General method
Anthranilic acid (1), PTSA (2), and solvents were purchased from Sigma–Aldrich
Chemical Company (U.S.A.) with a stated purity of greater than 98% and used as such without
further purification. Infrared spectrum of 2-carboxyanilinium p-toluenesulfonate (3) was
recorded between 4000 and 400 cm−1 on Perkin-Elmer FTIR spectrophotometer using solid KBr
plates. The spectrum was recorded at room temperature, with scanning speed of 30 cm−1 min−1
and the spectral resolution of 2.0 cm−1 in CSL Laboratory, Balikesir University, Turkey.
Synthesis
+
The title compound (3, C7H8NO2 ·C7H7O3S) was synthesized by the reaction of
anthranilic acid (1 mmol) with PTSA (1 mmol) in methanol (50 mL) for 40 min under reflux.
After concentration to ca 30 ml of the hot-filtered solution, colorless prismatic crystals of (3),
suitable for X-ray analysis were obtained by slow evaporation at room temperature. m.p. 163-
164 ºC. Analysis for C14H15NO5S calculated: %C, 54.36; %H, 4.89; %N, 4.53; found: %C,
54.29; %H, 4.92; %N, 4.56.
Crystal structure determination
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Diffraction measurements were made on a Bruker ApexII kappa CCD diffractometer using
graphite monochromated Mo–K radiation (λ = 0.71073 Å) at 100 K for 3. The intensity data
were integrated using the APEXII program.29 Absorption corrections were applied based on
equivalent reflections using SADABS.30 The structures were solved by direct methods and
refined using full–matrix least–squares against F2 using SHELXL.17 All non–hydrogen atoms
were assigned anisotropic displacement parameters and refined without positional constraints.
Hydrogen atoms were included in idealized positions with isotropic displacement parameters
constrained to 1.5 times the Uequiv of their attached carbon atoms for methyl hydrogens, and 1.2
times the Uequiv of their attached carbon atoms for all others. A possible disorder in the
ethanolamine portion of the ligand for the title complex (3) has been considered. All of the
crystallographic computations were carried out with the help of SHELXTL31, MERCURY32, and
ORTEP-333 programs. Details of the data collection parameters and crystallographic information
for the complexes are summarized in Table 1.
COMPUTATIONAL DETAILS
The proton transfer compound (3) and its non-ionic form (4) were examined using ab-initio
methods implemented in the GAUSSIAN 03W program package.34,35 Full geometry
optimizations without any constrained were performed at the HF/6-31G(d) and the HF/6-
31+G(d,p) levels of theory. The vibrational frequencies of the title compound (3) were also
calculated at the HF/6-31G(d) and the HF/6-31+G(d,p). Agreement among the two methods is a
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good indicator that the vibrational modes have been correctly assigned. Each motion (stretching,
symmetric stretching, asymmetric stretching, in-plane bending, out-of-plane bending, wagging,
scissoring, rocking, twisting) of normal modes were interpreted by means of visual inspection
with the help of GaussView program.36 Stationary points were characterized as minima or
transition structures by way of an analytic evaluation of harmonic frequencies at the level of
geometry optimization. All energies values reported here include unscaled zero-point vibrational
energies.
To predict reactive sites for electophilic and nucleophilic attack for the title molecule,
molecular electrostatic potential (MEP) was calculated using the HF/6-31+G(d,p) level. MEP,
V(r), at a given point r(x,y,z) in the vicinity of a molecule, is defined in terms of the interaction
energy between the electrical charge generated from the molecule electrons and nuclei and
positive test charge (a proton) located at r. For the systems studied, V(r) was calculated as
described previously, using the equation,37
(1)
where ZA is the charge of nucleus A, located at RA, ρ(r′) is the electronic density function of the
molecule as obtained from ab-initio calculations, and r′ is the dummy integration variable.
Supplemental data
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CCDC 752447 contains the supplementary crystallographic data, Molecular electrostatic
potential map, HOMO/LUMO images, nucleus-independent chemical shift (NICS) images, and
atomic charges of the structures for this paper. These data can be obtained free of charge
via www.ccdc.cam.ac.uk/retrieving.html (or from the Cambridge Crystallographic Data Centre,
12, Union Road, Cambridge, B2 1EZ, UK; fax +44 1223 336033; or deposit@ccdc.cam.ac.uk).
Acknowledgements
The authors are indebted to the Scientific and Technical Research Council of Turkey
(TUBITAK) and University of Balikesir for their financial support. Dr. Kara would like to thank
TUBITAK for NATO-B1 and the Royal Society short visit fellowship for financial support and
Prof. Guy Orpen (School of Chemistry, University of Bristol, UK) for his hospitality. The
authors are also very grateful to Dr. Mairi F. Haddow (The School of Chemistry, University of
Bristol) for the X-ray measurements.
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Figure S 1: Molecular electrostatic potential map of 3 calculated at the HF/6-31+G(d,p) level
(where red indicates negative, blue indicates positive and green indicates neutral)
3
TS(3→4)
4
EHOMO
-0.323
-0.301
-0.320
ELUMO
∆E(eV
)
+0.035
0.358
+0.124
0.425
+0.061
0.381
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Figure S 2: Molecular orbital surfaces and energies for the HOMO and LUMO of 3, 4, and TS
at the HF/6-31G+(d,p) level
Figure S 3: Bq1 (pink, left side) and Bq2 (pink, right side) atoms at the ring centers of the title
complex (3)
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(1)
(2)
Figure S4: Bq3 (pink, left side) and Bq4 (pink, right side) atoms at the ring centers of the
anthranilic acid (1) and PTSA (2), respectively
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Table S 1: Selected experimental and theoretical vibrational frequencies (cm−1) of title
compound 3
Exp.
434
HF/6-31G(d)
HF/6-31G+(d,p)
Assignmentsa
Frequency Intensity Frequency Intensity
424.1
644.6
699.0
755.6
809.5
845.9
900
4.3
102.2
0.1
422.5
631.7
696.5
749.3
807.1
844.5
901.9
903.1
951.1
1136.4
1202.0
5.2
154.7
0.2
γ(C-C-C)
Φ(O-H)
γ(C-C-C)
ν(-C-SO3)
δ(C-OH)
γ(C-H)
685
755
806
837
890
187.4
32.4
99.5
0.7
176.7
31.2
101.1
1.3
γ(C-H)
+
904.1
955.8
1143.2
1208.7
12.4
0.4
12.5
0.5
ν(C-NH3 )
966
γ(C-H)
ν(C=C)
7.6
9.4
+
163.1
116.8
ω(NH3 )
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1255
1295 1283
1329.7
1542.0
187.0
5.6
1527.7
1274.2
1324.7
1331.4
1360.6
1804.1
1617.1
1734.1
215.1
3.1
ν(C-OH)
α(C=C-H)
ν(C-CH3)
α(O-H)
0.1
1.2
1345.7
1379.3
1558.4
1566.6
1632.5
253.6
473.6
10.4
1.1
205.4
447.9
20.0
12.8
486.8
1417
1554
ν(S=O)
ν(C=C)
ω(C-H)
4.4
α(C-H)
ν(C=O), α(N-
H)
1712
1714
1980.9
1761.9
1776.6
1796.8
3203.4
3248.4
3681.4
4044.3
444.0
430.3
152.5
35.5
3182.9
1755.5
1794.2
1956.0
3266.2
3673.7
4112.9
4198.1
43.7
139.0
42.4
+
ω(NH3 )
+
δ(NH3 )
+
495.3
741.7
351.3
221.6
143.9
θ(NH3 )
2921
3195
3478
3691
43.8
νs(C-H)
νs(N-H)
νas(N-H)
νs(O-H)
891.2
329.6
211.3
a Vibrational modes: ν, stretching; νs,symmetric stretching; νas, asymmetric stretching; δ, in-plane
bending; γ, out-of-plane bending; ω, wagging; α, scissoring; Φ, rocking; θ, twisting
Table S 2: NBO Atomic Charges of title compound 3 at the HF/6-31G(d) and HF/6-31+G(d,p)
HF/
6-
HF/
6-
HF/
6-
HF/
6-
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31G(d) 31+G(d,p)
31G(d) 31+G(d,p)
S1
2.732
-1.081
-1.159
-1.161
-0.371
-0.183
2.690
-1.148
-1.148
-1.102
-0.365
-0.179
-0.010
-0.175
-0.659
-0.736
-0.771
-0.879
-0.229
0.190
C3
-0.239
-0.151
1.005
0.254
0.250
-0.244
-0.159
0.990
0.270
0.249
0.230
0.236
0.236
0.495
0.527
0.527
0.291
0.266
O3
O4
O5
C8
C9
C6
C7
H9
H13
H14A 0.222
H14B 0.231
H14C 0.225
C11 -0.013
C13 -0.181
C14 -0.642
H1A
H1B
H1C
H3
0.481
0.520
0.510
0.278
0.259
O1
O2
N1
C1
C2
-0.733
-0.754
-0.838
-0.229
0.194
H6
Table S 3 Comparison of NICS data (ppm) of anthranilic acid (1), PTSA (2) and the title
complex (3) at the HF/6-31G+(d,p) level
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Compound
Bq1 of C7H7O3S part
of 3
NICS
-10.3
+
Bq2 of C7H8NO2 part
-10.9
-8.6
of 3
Bq3 of Anthranilic
acid
Bq4 of PTSA
-10.4
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Table 1
Crystal data and structure refinement for 3
Empirical formula
Formula weight (g mol–1 )
Temperature (K)
Crystal system
C14H15NO5S
309.33
100(2)
Triclinic
P-1
Space group
Unit cell dimensions
a = 6.3703(5)

=
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Å
93.156(2)°
b = 9.0379(6)

=
=
Å
90.301(3)°
=

c
11.8521(8) Å
680.46(8)
92.883(3)°
Volume (Å3 )
Z
2
Density (calculated) (g/cm–3 ) 1.510
Absorption coefficient (mm– 0.260
1
)
1.72 to 27.60°
 range for data collection
hkl ranges
-7<=h<=8
-11<=k<=11
-14<=l<=15
7208
Reflections collected
Independent reflections
3142 [Rint = 0.0278]
Refinement method
Full-matrix least-squares on
F2
Data / restraints / parameters 3142 / 0 / 193
Goodness-of-fit on F2
R indices
S = 1.054
[for 2741 reflections with R1 = 0.0353, wR2 = 0.0923
I>2(I)]
R indices
(for all 3142 data)
R1 = 0.0415, wR2 = 0.0969
Largest diff. peak and hole
0.402 and -0.479 eÅ-3
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