Synthesis, thermogravimetric, spectroscopic and theoretical characterization of copper(II) complex with 4-chloro-2-nitrobenzenosulfonamide

Article abstract of DOI:10.1016/j.molstruc.2011.03.059

4-Chloro-2-nitrobenzenesulfonamide (ClNbsa) was purified and characterized. A new copper(II) complex, [Cu(ClNbsa)₂(NH₃)₂], has been prepared using the sulfonamide as ligand. The thermal behavior of both, the ligand and the Cu(II) complex, was investigated by thermogravimetric analyses (TG) and differential thermal analysis (DT), and the electronic characteristics analyzed by UV-VIS, FTIR, Raman and ¹H NMR spectroscopies. The experimental IR, Raman and UV-VIS spectra have been assigned on the basis of DFT calculations at the B3LYP level of theory using the standard (6-31 + G¹) basis set. The geometries have been fully optimized in vacuum and in modeled dimethylsulfoxide (DMSO) solvent, using for the latter a continuum solvation model that reproduced the experimental conditions of the UV-VIS spectroscopy. The theoretical results converged to stable conformations for the free sulfonamide and for the complex, suggesting for the latter a distorted square planar geometry in both environments.

Full text of DOI:10.1016/j.molstruc.2011.03.059

Journal of Molecular Structure 995 (2011) 72–77
Contents lists available at ScienceDirect
Journal of Molecular Structure
journal homepage: www.elsevier.com/locate/molstruc
Synthesis, thermogravimetric, spectroscopic and theoretical characterization
of copper(II) complex with 4-chloro-2-nitrobenzenosulfonamide
G. Camí a, E. Chacón Villalba b, Y. Di Santi b, P. Colinas c, G. Estiu d, D.B. Soria b,
⇑
a Área de Química General e Inorgánica, Departamento de Química, Facultad de Química, Bioquímica y Farmacia, Universidad Nacional de San Luis,
Chacabuco y Pedernera, 5700 San Luis, Argentina
b CEQUINOR, Departamento de Química, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, 47 y 115 (1900) La Plata, Argentina
c LADECOR, Departamento de Química, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, 47 y 115 (1900) La Plata, Argentina
d Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556, USA
a r t i c l e i n f o
a b s t r a c t
Article history:
4-Chloro-2-nitrobenzenesulfonamide (ClNbsa) was purified and characterized. A new copper(II) complex,
[Cu(ClNbsa)2(NH3)2], has been prepared using the sulfonamide as ligand. The thermal behavior of both,
the ligand and the Cu(II) complex, was investigated by thermogravimetric analyses (TG) and differential
thermal analysis (DT), and the electronic characteristics analyzed by UV–VIS, FTIR, Raman and 1H NMR
spectroscopies. The experimental IR, Raman and UV–VIS spectra have been assigned on the basis of
DFT calculations at the B3LYP level of theory using the standard (6-31 + G⁄⁄) basis set. The geometries
have been fully optimized in vacuum and in modeled dimethylsulfoxide (DMSO) solvent, using for the
latter a continuum solvation model that reproduced the experimental conditions of the UV–VIS spectros-
copy. The theoretical results converged to stable conformations for the free sulfonamide and for the com-
plex, suggesting for the latter a distorted square planar geometry in both environments.
Ó 2011 Elsevier B.V. All rights reserved.
Received 13 February 2011
Received in revised form 23 March 2011
Accepted 24 March 2011
Available online 9 April 2011
Keywords:
Sulfonamide
Copper(II) complex
Synthesis
Infrared and Raman
Theoretical results
Thermal analyses
1. Introduction
are known to be promising reagents for the cleavage of nucleic
acids [8].
Sulfonamides, which have been clinically used for many years,
have been found to possess a large number of different biological
activities, including antibacterial, antiviral, antidiabetic, diuretic,
and anti thyroid activities [1]. They exert their diverse pharmaco-
logical effects by interacting with a wide range of different cellular
targets. The coordination chemistry of sulfonamides has under-
gone noticeable development in recent years due to the interesting
properties of these substances, such as those related to superoxide
dismutase (SOD) mimetic activity [2] and chemical nucleases. In
1941 Braun and Towel obtained the silver salt of sulfanilamide
[3]. Nevertheless, it was not until the early 1980 that, after the
work by Bult [4] and Malecki, [5] the sulfonamide anion started
to be broadly used as s-donor ligand for cations. Later on Supuran
et al. investigated the metal complexes as a new class of carbonic
anhydrase inhibitors [6]. Carbonic anhydrases (CAs) are ubiquitous
zinc enzymes that catalyze the interconversion between carbon
dioxide and the bicarbonate ion [7]. Complexes based on sulfona-
mides as ligands are also artificial chemical nucleases that degrade
DNA in the presence of sodium ascorbate. Thus, copper complexes
In the light of the interest on coordination chemistry of sulfon-
amides, we describe here the synthesis and characterization of
the sulfonamide 4-chlorine-2-nitro benzenesulfonamide as well
as its copper complex. Due to their poor solubility in water and
in most organic solvents, it was not possible to obtain crystals
of the metallic complex to analyze their structure by single-
crystal X-raydiffraction (XRD) technique. Thus, the theoretical
optimized geometry is reported, together with the spectroscopic
(FTIR, Raman, 1H NMR and UV–VIS) and thermogravimetric prop-
erties of the copper(II) complex, as an alternative way to infer
details of the molecular structure. The assignment of experimen-
tal electronic, infrared and Raman bands was accomplished with
the aid of the theoretical results based in density functional
theory.
2. Experimental
2.1. Physical and chemical measurements
4-Chloro-2-nitrobenzenesulfonamide (ClNbsa) and copper
chloride were purchased from Fluka AG and all reagents used were
of analytical grade. Chemical analyses for carbon, hydrogen, and
nitrogen were performed on 1108 elemental analyzer from Carlo
⇑
Corresponding author. Tel.: +54 221 4259485; fax: +54 221 4240172.
E-mail address: soria@quimica.unlp.edu.ar (D.B. Soria).
0022-2860/$ - see front matter Ó 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.molstruc.2011.03.059

G. Camí et al. / Journal of Molecular Structure 995 (2011) 72–77
73
Erba EA and copper content was determined by iodimetry. The
FTIR (KBr pellets) and Raman spectra were recorded with a Bruker
IFS 66v FTIR spectrophotometer with a NIR Raman attachment.
UV–VIS spectra were recorded with a Hewlett–Packard 8453
diode-array using 10 mm quartz cells. The electronic spectra of
the ligand and the complex were recorded at room temperature
using dimethylsulfoxide as solvent. DT and TG analyses were per-
formed with Shimadzu TGA-50 and DTA-50H units at a heating
rate of 5 °C/min. and oxygen flow of 50 ml/min. 1H NMR spectrum
of ClNbsa in CDCl3 purchased from Sigma solution was recorded on
a Varian Mercury Plus, 200 MHz instrument at room temperature
with TMS as an internal standard.
(a)
(b)
(c)
(d)
2.2. Synthesis of complex
4-Chloro-2-nitrobenzenesulfonamide was purified by several
crystallizations from ethyl acetate (AcOEt)/hexane.
4000
3500
3000
1500 1250 1000 750 500 250
Wavenumber (cm-1)
The copper complex was prepared by direct reaction of etha-
nolic solutions of sulfonamide and copper(II) chloride in the
2:1 M ratio, followed by dropwise addition of 2 ml of NH3 2 M.
The resulting mixture was stirred for ca. 12 h. and the light blue
solid was filtered. Yield was in the 70–75% range. The elemental
analysis of the complex suggests the general formula, [Cu(ClNb-
sa)2(NH3)2]: Analytical Calculation for C12H10Cl2N4O4S2CuAN2H6
C, 25.5%; H, 2.6%; N, 14.7%; S,11.2% Found: C, 25.6%; H, 2.4%; N,
14.3%; S,11.1%.
Fig. 1. FTIR and Raman spectra at room temperature. (a) IR spectrum of the free
sulfonamide. (b) IR spectrum of the copper complex. (c) Raman spectrum of the
copper complex. (d) Raman spectrum of the free sulfonamide.
complex and the assignments of the bands become more compli-
cated. Nevertheless, on the basis of group frequencies, tentative
assignments of the most prominent spectral features can be done,
and further confirmed by theoretical calculations [15–17]. The
spectrum of the complex was compared with those of the free sul-
fonamide in order to determine the coordination atoms that may
be involved in chelation. It was also compared with similar com-
plexes reported in the literature [18–20]. Table 1 summarizes the
main observed and calculated bands, their approximate intensities
and their proposed assignments.
The FTIR spectrum of the ligand shows bands at 3400–
3250 cmꢀ1 and at 1550–1500 cmꢀ1 associated with the presence
of the sulfonamide NH2 groups, which are assigned to stretching
and bending vibrations, respectively. As Table 1 shows, these bands
are shifted in the complex. These results and the disappearance of
3. Computational methods
The computational study of the ligand and the copper complex
were performed using the density functional theory (DFT) methods
implemented in Gaussian 09 [9]. The systems studied herein were
subjected to unrestrained energy minimizations using the B3LYP
functional [10] with the 6-31 + G⁄⁄ basis set [11] for nonmetal
atoms and the Los Alamos effective core potentials LANL2DZ [12]
for the metal. DFT methods have been shown to reproduce the
structural properties of several biologically interesting transition
metal centers, and their validity to model ground-state properties
is widely accepted [13]. The basis sets were chosen as those that
better reproduces the experimental UV–VIS data.
The geometries of both ligand and Cu-complex have been opti-
mized in gas phase and in DMSO modeled solvent, and their calcu-
lated spectral features compared with experimental IR, Raman and
UV–VIS data respectively. The geometry optimized in gas phase
has been used to calculate the IR frequencies, as they were deter-
mined in solid phase. IR frequencies have been corrected using
0.96 as scaling factor. In order to model the UV–VIS spectra exper-
imentally determined in DMSO, the geometries were optimized
modeling the solvent within a continuous approach (Polarizable
Continuous Model, PCM) [14] and used to calculate the UV–VIS
spectra in the same conditions. Time dependent DFT models were
used for the latter, allowing us to assign the nature of the observed
electronic transitions.
one mNH band of the ligand in the spectrum of the complex indi-
cate that the NH2 group is involved in the coordination with the
copper atom. The broad band at ꢁ3400 cmꢀ1, together with a
new band at ꢁ700 cmꢀ1 are also indicative of the presence of coor-
dinating NH3.
Among the IR bands originated in the ligands, those associated
with the SO2 group are most informative. Bands due to the anti-
symmetric and symmetric vibration modes of the SO bonds in
the complex are recorded close to 1300 and 1000 cmꢀ1, i.e. at low-
er frequencies than those corresponding to the free ligand. This
spectral feature is associated with the binding of the sulfonamides
through the deprotonated sulfonamide moiety [18–20]. This mode
is observed at 1348 cmꢀ1 as a strong band (calc. 1283) in the IR
spectrum of the ligand and as a shoulder in Raman spectrum. It
is shifted to 1212 cmꢀ1 (calc. 1212) in the IR spectrum of the cop-
per complex and is not visible in Raman. The symmetric SO2 mode
is poorly affected in both infrared and Raman spectra, displaying at
1060 (calc.1064) in the ligand and at 1055 cmꢀ1 (calc. 1042) in the
complex [20–22].
4. Results and discussion
4.1. Spectroscopic properties
As a general behavior, the deprotonation and metal coordi-
nation of sulfonamide nitrogen increases the SAN bond order
4.1.1. Infrared and Raman spectra
The FTIR spectra of the sulfonamide (ClNbsa) and its Cu(II)
complex are given in Fig. 1a and b, respectively. The Raman spectra
of both samples are also included (Fig. 1c for complex and Fig. 1d
for ligand). For a proper understanding of FTIR and Raman spectra,
reliable assignment of all vibrational bands is essential. However
no reliable crystal structure has been yet determined for the Cu
[20–23], leading to a shift of the m(SAN) band to higher frequency.
The changes of the v(SAN) vibrations from 920 cmꢀ1 in the com-
plex to 978 cmꢀ1 in the ligand, are expected from the shortening
of the SAN bond length. The coordination of the NH3 molecules
is indicated by the broad band centered at 688 cmꢀ1 (calc.
655 cmꢀ1) assigned to a torsion mode. This band is absent in the

74
G. Camí et al. / Journal of Molecular Structure 995 (2011) 72–77
Table 1
Observed FTIR and Raman bands and calculated IR frequencies and Raman amplitudes, in cmꢀ1, of 4-chloro-2-nitrobenzenosulfonamide and Copper complex.
ClNbsa
IR
Cu(ClNbsa)2(NH3)2]
B3LYP IR
Raman
B3LYP Raman
IR
B3LYP IR
Raman
B3LYP Raman
Assignments
3431 sh
3394 sh
3420(68)
3397(12)
3420 (55)
3404(134)
m
m
asNH3
NAH
3368 vs
3272 vs
3482(59)
3370(62)
3483(54)
3370 (147)
mas NH2
(
3362 s
3281 s
3095 m
1617 m
1592 sh
1536 s
3350(10)
3285(44)
3114(14)
1614(32)
1578(125)
1539(67)
3351(88)
3285(176))
3111 (101)
1615(3.5)
1577(20)
1540 (12)
ms NH2)a
m NAH
m
m
sNH3
CAH
3089 m
3114 (6)
3088 m
1600 m
3114(97)
3087 m
dNH3
Ring +
Ring +
dNH2
1592 m
1533 s
1365 vs
1578(109)
1530(28)
1339(192)
1578(15)
1540(67)
1339(63)
1593 w
1547 w
m
m
asNO2
asNO2
1351 s
1212 s
1160 m
1136 s
1055 s
978 s
1352(161)
1212(112)
1162(48)
1141(122)
1042(96)
830(819)
847(64)
1348 s
–
1353(27)
1213(9)
1163(17)
1141(26)
1044(45)
830(15)
855(1)
dCAH +
msNO2
1348 vs
1164 s
1136 m
1060 w
920 m
885 m
776 s
1283(107)
–
1348 sh
1162 vs
1136 w
1054 s
1279(9)
–
1134(9)
1044(4)
–
dNAH + masSO2 + ring
1156 m
1134 w
1055 s
989 m
–
(dNH2)a dNH3
1141(80)
1064 (7)
818(168)
856 (51)
733(23)
(dNH2)a dNH3 + ring
m
m
sSO2 + ring
SAN + ring
856(2)
743(12)
887 m
dNO2
NH2 + dNO2 + ring
dNAH + dNH3
NH2)a dNAH + dNH3
SO2 NH2 + ring
+ mCANO2 + ring
773 s
666 s
–
q
775 s
721(155)
655(88)
566(100)
459(50)
473(64)
368(10)
775 m
–
594 m
–
722 (17)
655(9)
566 (3)
459(4)
474(30)
368(2)
662 m
541 s
450 m
622(150)
544(77)
443(31)
622(3)
545 (3)
443 (1)
688 m
560 w
486 m
434 m
(q
q
+ q
m
m
m
CACl + ring
CuANH
CuANH3
–
394 m
a
Ligand only.
spectrum of the ligand. The nature of the metal–ligand bond is con-
firmed by the new band that develops at ꢂ440 cm–1 in the spec-
trum of the complex, which is assigned to CuAN vibration. The
in 192 and 225 nm, originated in p ?
p⁄ transitions, which are
experimentally obscured by DMSO absorption. An additional band
is calculated at 326 nm (f = 0.03), originated in HOMO–LUMO tran-
sitions, for the HOMO centered in the chlorobenzene and the
LUMO in the nitrobenzene moieties respectively. This band is ob-
served in the FTIR spectra in the second-derivative of the mode
at 318 nm. The spectra of the complex shows similar features, orig-
stretching vibrations of CuANH appear as
a weak band, at
434 cmꢀ1 (calc. 473 cmꢀ1). The CuANH3 vibration is observed as
a weak band in Raman spectrum at 394 cmꢀ1 (calc. 368 cmꢀ1) [22].
inated in n ? p⁄ and
solved band in the visible region at 650 nm (
p
?
p⁄ transitions, together with a poorly re-
4.1.2. Electronic absorption spectra
e
. = 81.00 cmꢀ1Mꢀ1
)
The electronic absorption spectra are often very helpful in the
evaluation of results furnished by other methods of structural
investigation. The electronic spectrum of the Cu(II) complex is
compared with that of the ligand. They are reported in Fig. 2.
Two intense bands appear at 286 and 266 nm in the latter, which
are in agreement with the calculated transitions at 286 (oscillator
strength (f = 0.007) and 268 (f = 0.07) assigned to n ? p⁄ and
assigned to d–d transitions The assignment is confirmed by the
theoretical calculated transitions at 652, 540, 477 and 462 nm.
These transitions are calculated with intensity zero, but can gain
intensity through vibronic coupling. Moreover, the experimentally
determined energies and intensities (e. = 1.10) are in agreement
with reported ligand field transitions of planar or tetragonal Cu(II)
?
p⁄ transitions respectively. Strong bands are also calculated
chromophores having equatorial CuN4 ligation [24,25].
p
200
300
400
500
nm
600
700
800
Fig. 2. Electronic spectra in DMSO: (a) free ligand and (b) the copper complex. Inset: (I) 200–400 nm region and (II) 500–800 nm region.

G. Camí et al. / Journal of Molecular Structure 995 (2011) 72–77
75
4.1.3. 1H NMR spectra
singlet at 5.49 ppm corresponds to the hydrogen atoms of the
sulfonamide moiety. Unfortunately, the NMR spectrum of the para-
magnetic Cu(II) complex could not be measured in solution, and no
comparison with the ligand has been possible.
The 1NMR spectrum of the ligand has been measured to support
the structural assignment. Four groups of signals around 8.15 ppm,
7.92 ppm, 7.73 ppm and 5.49 are observed in the 1H NMR (see
Scheme 1). The first group is a doublet assigned to the hydrogen
atom ortho to the sulfonamide group with a coupling constant of
8.5 Hz. The doublet at 7.73 ppm corresponds to the hydrogen atom
ortho to the chlorine atom and to the nitro group and shows a cou-
pling constant of 2.1 Hz. The peak around 7.92 ppm is a double
doublet with coupling constants of 2.1 and 8.5 Hz, which is
assigned to the hydrogen atom ortho to the chlorine one. The broad
4.2. Thermogravimetric study
4.2.1. TG-DT of the ligand
The thermogravimetric curve shows that the ligand is stable up
to 220 °C. A sharp loss of weight of 85% takes place in the 220–
300 °C temperature range, followed by a slow weight loss of 15%
until 600 °C that is attributed to the breakage of the sulfonamide.
The DT curve shows and endothermic processes at approxi-
mately 165 °C, without weight loss in the TG curve corresponding
to the melting point. The second endothermic peak is observed at
280 °C. An exothermic peak with maximum at 550 °C is also dis-
played [26].
O
NH2
5.49
O
S
H
H
NO2
8.15
7.73
4.2.2. TG-DT of the complex
The TG curve of the complex reveals that the decomposition
takes place in three steps. The first one corresponds to a weight
loss of 51% and is probably due to decomposition of the two NH3
groups, and of those coordinated to the benzene ring as NO2 and
Cl (loss of weight calculated 52%). This process takes place between
150 and 290 °C. The second step occurs until 350 °C and is
H
7.92
Cl
Scheme 1. 1H NMR chemical shifts for the ligand.
124.10
157.21
2.03
1.75
1.40
a
b
c
Fig. 3. Geometry optimized structures (a) free sulfonamide, (b) copper complex in gas phase, (c) complex in DMSO modeled solvent. The most significant changes in the
torsion angles are shown. More details are given in the text.

76
G. Camí et al. / Journal of Molecular Structure 995 (2011) 72–77
Table 2
Selected bond distances, in Å, angles and torsion angles, in degrees, of the 4-chloro-2-nitrobenzenosulfonamide and Copper complex. The numbers between parentheses are those
calculated in DMSO modeled solvent.
Bonds distances (Å)
Angles (Deg)
Torsion (Deg)
ClNbsa
SAO
SAN
CAS
1.462
1.693
1.823
1.402
1.747
1.481
1. 225
CASAN
CASAO
NASAO
CACAS
OANAO
CACAC
101.17
109.27
105.74
122.78
125.96
117.97
ClACACAS
OANACAC
CACASAN
CACASAO
SACACAN
ꢀ94.358
ꢀ38.06
19.95
C@C
ꢀ91.27
CACl
CAN
NAO
ꢀ5.294
[Cu(ClNbsa)2(NH3)2]
SAO
SAN
CAS
C@C
CACl
CAN(O2)
NAO
CuANH3
CuANH
CuANH
1.482
1.627
1.826
1.393
1.743
1.480
1. 231
2.094
2.035
1.989
CASAN
OASAO
NASAO
CACAS
OANAO
CACAC
NH3ACuANH3
NHACuANH
SACuAS
105.17
120.35
107.99
118.93
126.07
121.45
154.47
160.81
158.03
ClACACAS
OANACAC
CACASAN
CACASAO
SACuASAC
NACuANAC
SANACuAN
CuANASAC
CuANASAC
131.684
133.27
26.54
140.009
106.78
93.841
47.64
ꢀ157.21 (ꢀ121.59)
124.10 (110.46)
associated with the Cu-coordinated NH groups as well as with one
of the SO2 groups (calc. 16% and observed 16%). Immediately after
the second step, a third step takes place until 600 °C with weight
loss of 26%, assigned to the reaction of the other SO2 group with
Cu and a partial oxidation to cupric sulfate in a similar way as that
observed in a thermogravimetric study of the sulfonamide cupper
complexes [22].
The DT curve shows three exothermic peaks at 178, 190 and
214 °C corresponding to the partial decomposition of the ligand.
A second group of exothermic peaks is observed at 375, 384, 389
and 409 °C, and corresponds to the complete decomposition of
the ligands and to the oxidation process described for the TG curve
interpretation.
the same plane but forming CuANASAC torsional angles of
ꢀ157.27° and 124.81°, respectively, and they are trans to each
other attending the relative orientation of the NO2 groups. The
two NH3 ligands define an staggered conformation. The optimized
geometries in DMSO show different CuANASAC torsional angles of
ꢀ121.59° and 110.46°, respectively. The values are shown in Table
2 between parenthesis and the torsions indicated as arrows in
Fig. 3.
The optimized geometry of the complex is in very good agree-
ment with the X-ray structure of other sulfonamides [20,22,24].
5. Conclusions
This study reports the successful synthesis and characterization
of new Cu(II) complex, [Cu(ClNbsa)2(NH3)2], with (ClNbsa = 4-
chloro-2-nitrobenzenosulfonamide), using analytical and physico-
chemical techniques. UV–VIS, NMR, FTIR and FT-Raman spectra
of the free ClNbsa and its copper complex, have been investigated.
B3LYP calculations have been used to determine the structural
characteristics and to better assign the electronic and vibrational
spectroscopic features. The good agreement between the experi-
mental and calculated wavenumbers of the normal modes of both
compounds allows us to safely assign the vibrational spectrum of
the molecules. The resulting optimized geometry is in agreement
with reported X-ray structure of other sulfonamides and their
copper complexes.
4.3. Theoretical results
The structures of the ligand and the complex, as they result
from the in vacuum geometry optimization procedure, are shown
in Fig. 3. The figure also shows the geometry of the Cu complex
modeled in DMSO, in order to show how the presence of the sol-
vent affects the structure. The geometry of the ligand does not
show any significant difference when modeled in both conditions.
Relevant bond distances and angles are reported in Table 2 and
compared with available data found in the literature for similar
compounds [20,22,24].
In the ligand structure the two substituents, namely the chlo-
rine and the nitrogen atom of the NO2 group, are located in a plane
defined by the benzene ring and the sulfur atom. Therefore, the
nitrogen atom of the NH2 group lies out of the plane defining a
dihedral angle of ꢀ28°. The oxygen atoms of the SO2 group are al-
Acknowledgments
D.B.S., E.Ch.V. and P.C. thanks CONICET (CEQUINOR and
PIP0356), SUBCYT and CICPBA, República Argentina, for financial
support. G.C. thanks to the Universitiy of San Luis and G.E. thanks
to the Center for Research Computing at the University of Notre
Dame.
most perpendicular to that plane. The average CAC bond distance
0
in the benzene ring is 1.402 ÅA, and the CAS and SAN bonds lengths
0
0
are 1.823 ÅA and 1.693 ÅA, respectively.
The optimized geometry of the complex is best described as dis-
torted square planar. The metal ion is tetracoordinated by four N
atoms, two of them belonging to the NH3 ligands with CuANH3
References
0
0
bonds lengths of 2.094 ÅA and 2.073 ÅA, and the other two belonging
[1] A. Scozzafava, T. Owa, A. Mastrolorenzo, C.T. Supuran, Curr. Med. Chem. 10
(2003) 925.
[2] M. González-Álvarez, G. Alzuet, J. Borrás, L.C. Agudo, S. Garcia-Granda, J.M.
Montejo-Bernardo, Inorg. Chem. 44 (2005) 9424.
[3] C.E. Braun, J.L. Towle, J. Am. Chem. Soc. 63 (1941) 3523.
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[6] C.T. Supuran, J.Y. Winum, Drug Design of Zinc-Enzyme Inhibitors: Functional,
Structural, and Disease Applications, Wiley, Hoboken, NJ, 2009. p. 439.
to the NAH of the sulfonamide deprotonated groups with CuANH
0
0
bonds of 1.989 ÅA and 2.035 ÅA. It is to be noted that the SAN bond
0
length in 0the complex is shorter than in the free ligand, 1.627 ÅA
vs. 1.693 ÅA. This is agreement with the shift to the higher frequency
of the stretching bands originated in coordination. On the other
hand, the CAS bond remains almost unchanged in the complex,
0
0
1.823 ÅA vs. 1.826 ÅA. The sulfonamide ligands are not located in

G. Camí et al. / Journal of Molecular Structure 995 (2011) 72–77
77
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