Crystal structure, spectroscopy and theoretical studies of p-cyanobenzenosulfonamide and a Cu(II) complex

Article abstract of DOI:10.1016/j.molstruc.2012.05.006

The results of the structural and electronic structure of p-cyanobenzenosulfonamide (L), and its copper(II) complex, Cu(L) ₂(NH₃)₂ are reported. Both compounds have been prepared and their crystal structures determined. The sulfonamide crystallizes in the orthorhombic system, space group, Pnma and Z = 4, whereas the complex crystallizes in the triclinic system, P-1 and Z = 2. The coordination geometry of the copper(II) ion in the complex can be described as a distorted square planar with two N-sulfonamide and two NH₃ in opposite vertices. The thermal behavior of both, the ligand and the Cu(II) complex, was investigated by thermogravimetric analyses (TG) and differential thermal analysis (DT). The experimental IR, Raman and UV-VIS spectra have been assigned on the basis of DFT calculations.

Full text of DOI:10.1016/j.molstruc.2012.05.006

Journal of Molecular Structure 1024 (2012) 110–116
Contents lists available at SciVerse ScienceDirect
Journal of Molecular Structure
journal homepage: www.elsevier.com/locate/molstruc
Crystal structure, spectroscopy and theoretical studies
of p-cyanobenzenosulfonamide and a Cu(II) complex
G.E. Camí a, M.E. Chacón Villalba b, P. Colinas c, G.A. Echeverría d, G. Estiu e, 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 LANADI e IFLP (CCT-La Plata, CONICET), Departamento de Física, Facultad de Ciencias Exactas and Facultad de Ingeniería, Universidad Nacional de La Plata, CC67,
1900 La Plata, Argentina
e Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556, USA
h i g h l i g h t s
"
"
"
p-Cyanobenzenosulfonamide and a new copper complex were prepared and characterized.
The thermal behavior was investigated by thermogravimetric and differential thermal analysis.
The experimental IR, Raman and UV–VIS spectra have been assigned using Density Functional (DFT) calculations at B3LYP/6-311+G⁄⁄ level.
a r t i c l e i n f o
a b s t r a c t
Article history:
The results of the structural and electronic structure of p-cyanobenzenosulfonamide (L), and its copper(II)
complex, Cu(L)2(NH3)2 are reported. Both compounds have been prepared and their crystal structures
determined. The sulfonamide crystallizes in the orthorhombic system, space group, Pnma and Z = 4,
whereas the complex crystallizes in the triclinic system, P-1 and Z = 2. The coordination geometry of
the copper(II) ion in the complex can be described as a distorted square planar with two N-sulfonamide
and two NH3 in opposite vertices. The thermal behavior of both, the ligand and the Cu(II) complex, was
investigated by thermogravimetric analyses (TG) and differential thermal analysis (DT). The experimental
IR, Raman and UV–VIS spectra have been assigned on the basis of DFT calculations.
Received 29 February 2012
Received in revised form 1 May 2012
Accepted 2 May 2012
Available online 12 May 2012
Keywords:
p-Cyanobenzenosulfonamide
Cu(II) complex
Spectroscopic properties
X-ray structure
Ó 2012 Elsevier B.V. All rights reserved.
Density functional calculations
1. Introduction
bind in vivo with proteins and peptides [2]. Simple sulfonamides
have been observed to attract much attention into this emerging
Sulfonamides are recognized for their antibacterial, antitumor,
diuretic, antidiabetic, and antithyroid activity among others and
are well known as carbonic anhydrase and protease inhibitors
[1]. A new field of increasing interest in the last years is related
to the use of metal based therapeutics for both diagnosis and treat-
ment of diseases. The condensation products of sulpha drugs with
aldehydes, ketones or their derivatives are very active biologically,
besides having good complexing ability. Their activity, too, in-
creases on complexation with metal ions. The most significant part
of such metal based drug chemistry is, the ability of metal ions to
area of metal based sulfa drugs, initially stimulated by the success-
ful introduction of metal complexes of sulfadiazine to prevent bac-
terial infections [3]. Complexes based on sulfonamides as ligands
are also artificial chemical nucleases that degrade DNA in the pres-
ence of sodium ascorbate. The interaction of these complexes with
DNA has gained much attention due to possible applications as
new therapeutic agents [4]. Thus, copper complexes are known
to be promising reagents for the cleavage of nucleic acids [5].
In the light of the interest on coordination chemistry of sulfon-
amides, we report in the present study the synthesis of the
p-cyanobenzenosulfonamide (L, in what follows) as well as its
copper complex with formula Cu(L)2(NH3)2. Their characterization
by means of X-ray diffraction, thermogravimetry, IR, Raman,
NMR and UV–VIS spectra is also discussed. The assignment of
⇑
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 2012 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.molstruc.2012.05.006

G.E. Camí et al. / Journal of Molecular Structure 1024 (2012) 110–116
111
experimental electronic, infrared and Raman bands was accom-
plished with the aid of the theoretical results based in density
functional theory.
cell parameters and the orientation matrix for data collection were
obtained from a least-squares refinement using the setting angles
of 25 reflections in the h range 14–45°. Data were collected at room
temperature (293(2) K) in the
x–2h scan mode up to hmax = 70°,
with scan rate ranging between 6.7 and 20° minꢀ1. Two standard
reflections measured every 30 min were used to apply a decay cor-
rection (the maximum decay was 13%). The data collection and
reduction were performed with the programs CAD-4 [6] and
XCAD4 [7] respectively.
2. Experimental
2.1. Material and methods
Chemical analyses for carbon, hydrogen and nitrogen were per-
formed on 1108 elemental analyzer from Carlo Erba EA and copper
content was determined by iodimetry. The FTIR spectra were car-
ried out with an EQUINOX 55 spectrophotometer, in the range
from 4000 to 400 cmꢀ1 using the KBr pellet technique, with a spec-
tral resolution of 4 cmꢀ1. The Raman spectra were recorded with a
Bruker IFS 66 FTIR spectrophotometer provided with the NIR
Raman attachment, with a resolution of 4 cmꢀ1. The electronic
absorption spectra of the compounds were measured in two
different conditions: on freshly prepared DMSO solutions in the
200–800 nm spectral range, and in solid state with KBr reference
pellet. They were recorded with a Hewlett–Packard 8452-A diode
array spectrometer, using 10 mm quartz cells. NMR spectra of
p-cyanobenzenosulfonamide in DMSO-d6 (purchased from Aldrich)
solution was recorded on a Varian Mercury Plus, 200 MHz instru-
ment at room temperature with TMS as an internal standard. DT
and TG analyses were performed using Shimadzu TGA-50 and
DTA-50H units at a heating rate of 5 °C minꢀ1 and oxygen flow of
Data for complex 2 were obtained on an Oxford Xcalibur, Eos,
Gemini CCD diffractometer with graphite-monochromated CuK
(k = 1.54184 Å) radiation. X-ray diffraction intensities were
collected ( and scans with -offsets), integrated and scaled
a
u
x
j
with the CrysAlisPro [8] suite of programs. The unit cell
parameters were obtained by least-squares refinement based
on the angular settings for all collected reflections using
CrysAlisPro. Data were corrected empirically for absorption with
CrysAlisPro.
The structures were solved by direct methods with SHELXS-97
and the molecular model refined by full-matrix least-squares pro-
cedure on F2 with SHELXL-97 [9]. The crystallographic data, as well
as additional details of data collection and refinement results for
the two compounds are summarized in Table 1.
The programs SHELX [8], PLATON [10], PARST [11] and ORTEP-3
[12] within the WinGX packages [13] and MERCURY [14] were
used for structure analysis and to prepare materials for
publication.
In p-cyanobenzenosulfonamide compound, the hydrogen atoms
were positioned stereo-chemically and refined with the riding
model, while in the Cu(L)2(NH3)2 complex they were located from
the electronic Fourier different map and allowed to refine freely
with the exception of the ammonia hydrogen atoms which were
stereo-chemically located and refined by treating them as rigid
bodies (allowing to rotate around the C–NH3 bond).
50 ml minꢀ1
.
2.1.1. Synthesis of the p-cyanobenzenosulfonamide (1)
A cold solution of NaNO2 (1.2 g, 17 mmol) was added to a sus-
pension of sulfanilamide (2.5 g, 15 mmol) in 20 mL of a 2.3 N HCl
solution at 0 °C with vigorous stirring. The resultant solution
was poured into a suspension of KCN (4.16 g, 64 mmol) and
CuSO4ꢁ5H2O (3.85 g, 15 mmol) in 20 mL of water. After stirring for
30 min, the solution was heated to 80 °C and then chilled. The pre-
cipitate was filtered, dried and extracted with 5% ethanol in ben-
zene Soxhelt apparatus. The organic extract was concentrated and
the solid recrystallized from water to afford p-cyanobenzenosulf-
onamide (1.6 g, 60%). m.p. 173.2 °C determined by thermogravime-
try measures (TG-DT) and by melting point.
Table 1
Crystal data, structure determination and refinement summary.
(1)
(2)
Empirical formula
Formula weight
Temperature (K)
C7H6N2O2S
182.20
293(2)
C14H16CuN6O4S2
460.02
293(2)
1H NMR spectra: 1H NMR: d 7.58 (bs, –NH2), 7.95 (d, J = 8.4 Hz,
H-2, H-6), 8.06 (d, J = 8.4 Hz, H-3, H-5). 13C NMR: d 114.1 (C-4),
118.1 (–CN), 126.2 (C-2, C-6), 133.5 (C-3, C-5), 147.7 (C-1).
Analytical calculation for C7H6N2 O2S (%) C, 46.10%; H, 3.29%; N,
15.37%; found: C, 46.15%; H, 3.32%; N, 15.45%.
k [Cu(K
a
)] (Å)
1.54184
Orthorhombic
Pnma
19.84(2)
7.826(1)
5.316(1)
–
1.54184
Triclinic
P-1
Crystal system
Space group
a (Å)
b (Å)
c (Å)
6.2510(6)
7.7440(8)
10.6939(8)
99.832(7)
102.891(7)
104.892(8)
473.16(8)
1.614
2.1.2. Synthesis of the [Cu(L)2(NH3)2] complex (2)
a
(°)
b (°)
–
–
The copper complex was prepared by direct reaction of
ethanolic solutions of sulfonamide and copper(II) chloride in the
2:1 molar ratio, followed by drop wise addition of 0.6 ml of
concentrated ammonia, under continuous stirring. The resulting
mixture was stirred during ca. 4 h. and then was left to stand at
room temperature. Slow evaporation of the solution provided
well-developed violet crystals that were suitable for X-ray diffrac-
tion. They were collected by filtration washed and dried. The yield
was 80%.
c
(°)
V (Å3)
825.4(7)
1.466
qcalc (g/cm3)
Z
4
2
l
[Cu(K
F(000)
Crystal size (mm)
a
)] (mmꢀ1
)
3.178
376
4.001
235
–
4.37–73.94
ꢀ6 6 h 6 7
ꢀ9 6 k 6 9
ꢀ13 6 l 6 12
3548
0.16 ꢂ 0.16 ꢂ 0.36
4.46–69.96
ꢀ24 6 h 6 24
ꢀ9 6 k 6 1
ꢀ6 6 l 6 0
975
h Range for data collection (°)
Limiting indices
Analytical calculation for C14H16CuN6 O4S2 (%) C, 36.52%; H,
3.47%; N, 12.17%; found: C, 36.58%; H, 3.54%; N, 12.45%.
Reflections collected
Reflections unique with I > 2
Completeness to h = 69.90°
Data/restraints/parameters
Goodness-of-fit on F2
R
r
(I)
846
99.6%
846/0/65
1.090
0.0729
1911
99.7%
1911/0/148
1.036
0.0444
2.2. X-ray crystallography
Single-crystal X-ray data for compound 1 were taken on an
automatic four-circle Enraf–Nonius CAD-4 diffractometer with
graphite monochromated CuKa (k = 1.54184 Å) radiation. The unit
Rw
0.1874
0.438/ꢀ0.405
0.1125
0.504/ꢀ0.335
(
D
/
q)max/(D
/q
)
min
(e/Åꢀ3
)

112
G.E. Camí et al. / Journal of Molecular Structure 1024 (2012) 110–116
2.3. Computational methods
by the diagonal glide plane (n) are pointing to the sulfonyl oxygen
atoms connecting them through N–Hꢁ ꢁ ꢁO short contacts (1.968 Å)
as can be seen in Table 3. These contacts develop an extended
two-dimensional hydrogen bonds network parallel to the (1,0,0)
plane. On this plane the p-cyanobenzenosulfonamide molecules
are arranged with their main molecular axis at an angle of
46.4(5)°. The cyano groups are antiparallely stacked along the b
axis at a distance of 4.064(5)Å between two adjacent C–N bond
centers. These arrangement allow short contact between a carbon
ring hydrogen atoms (H13) and a cyano nitrogen atom and
although this distance are rather long, intermolecular interaction
via dipolar electric forces could not be ruled out.
The computational study of the ligand and the copper complex
were performed using the density functional theory (DFT) methods
implemented in Gaussian 09 [15]. The systems studied herein were
subjected to unrestrained energy minimizations using the B3LYP
functional [16] with the 6-31+Gꢃꢃ basis set [17] for nonmetal atoms
and the Los Alamos effective core potentials LANL2DZ [18] for the
metal. DFT methods have been shown to reproduce the structural
properties of several biologically interesting transition metal cen-
ters, and their validity to model ground-state properties is widely
accepted [19]. The basis sets were chosen as those that better
reproduces the experimental UV–VIS data.
Complex 2 crystallizes in the centrosymmetric triclinic space
group P-1. The Cu(II) cation is located in a planar environment
coordinated by two sulfonamide nitrogen atoms and two ammonia
nitrogen atoms related by an inversion center. In Fig. 2 is shown
the p-cyanobenzenosulfonamide molecules coordinated around
the copper atoms and in Fig. 3a and b are plotted two view of its
crystal packing. Along the b axis, sulfonamide groups of adjacent
Cu(II) cations are linked by centrosymmetric cyclic dimer of N–
Hꢁ ꢁ ꢁO contacts, involving the amine hydrogen atom H1 and oxygen
atom O1. The cyclic dimer plane and that one formed by the atoms
coordinated to Cu(II) cations lie approximately on the same layer
parallel to the (ꢀ1,0,3) plane. On this layer, another four inversion
related N–Hꢁ ꢁ ꢁO contacts are observed (see Fig. 3a). Two of them
link the ammonia hydrogen atom H31 with the oxygen atom O2
of sulfonamide groups bounded to the same Cu(II) cation, whereas
the other two link the ammonia hydrogen atom H33 with the
oxygen atom O1 of sulfonamide groups bounded to Cu(II) cations
related by inversion centers (see Fig. 3a). These layers are con-
nected also by N–Hꢁ ꢁ ꢁO contacts involving the ammonia hydrogen
atom H32 and the sulfonamide oxygen atom O2, developing a
corrugated two-dimensional network of N–Hꢁ ꢁ ꢁO contacts parallel
to the (0,0,1) layer, as can be seen in Fig. 3a. Finally, these layers
are connected by C–Hꢁ ꢁ ꢁN contacts involving the ring carbon
hydrogen atom H13 and the cyanide nitrogen atom N2 (see Table 3
and Fig. 3b).
A comparison of the p-cyanobenzenosulfonamide molecule in 1
with that bound to Cu(II) cation in 2 shows that sulfonamide group
are differently orientated with respect to the molecular ring plane,
the C12–C11–S1–N1 torsional angles are 88.7(3)° and 37.9(3)°
respectively. In addition, in 2 the N1–S1 distance is shorter, while
the S1–O1 and S1–O2 distances are longer than those observed in 1
(Table 2). The comparison of the calculated mean bond distances in
14/90 sulfonamide groups bounded/not bounded to a transition
metal atom obtained from a search in the CSD [21], S–N =
1.5804/1.6039, S–O = 1.4421/1.4350 and S–O0 = 1.4429/1.4351 Å
respectively, shows a similar behaviour of the sulfonamide group.
These results suggest a partial charge transfer after deprotonation
from the amine nitrogen atom to the sulfonyl S1–N1 bond, increas-
ing its S1–N1 bond order while decreasing the S–O double bonds
character.
The geometry of the Cu-complex has been optimized in gas
phase and both gas phase and DMSO modeled solvent were used
for the optimization of the ligand. Their calculated spectral fea-
tures were compared with experimental IR, Raman and UV–VIS
data. The geometry optimized in gas phase has been used to calcu-
late the IR frequencies, as they were determined in solid phase. IR
frequencies have been corrected using 0.96 as scaling factor. The
calculation of the UV–VIS spectra determined in solid phase was
also based on the gas phase optimized geometry. In order to model
the UV–VIS spectra experimentally determined in DMSO, the
geometries were optimized modeling the solvent within a contin-
uous approach (Polarizable Continuous Model, PCM) [20]. The
same solvent model was used to calculate the UV–VIS spectra in
DMSO. Time dependent DFT models were used in both cases in or-
der to assign the nature of the observed electronic transitions.
2.4. CSD survey methodology
Version 5.31 of the CSD [21], containing 495,968 structures was
used in this work. The complete CSD software system, which com-
prise Data base along with programs ConQuest [22] and Vista [23]
were employed in the survey. We search structures containing at
least one benzenosulfonamide derivative substituted in the para
position with any substituent and bounded and not bounded to a
transition metal atom through the amine nitrogen atom. The fol-
lowing filters were applied: error-free coordinates after CCDC in-
house validation, no disorder, no powder studies and R 6 0.1.
3. Results and discussion
3.1. Description of the crystal structure
System 1 crystallizes in the orthorhombic Pnma space group
with four molecules in the unit cell located on the mirror plane
(0,1,0). Fig. 1 shows the p-cyanobenzenosulfonamide molecule.
The cyano group, the sulfonamide sulfur and the nitrogen atoms
lie on the mirror plane and the six carbon ring planes been perpen-
dicular to it. The amine hydrogen atoms of those molecules related
3.2. Thermogravimetric study
3.2.1. TG-DT of the ligand
The thermogravimetric curve shows that the ligand is stable up
to 230 °C. Two sharp loss of weight of 58.6% (23% and 35.16%) take
place in the 200–360 °C temperature range, probably due to the
evolution of those coordinated to the benzene as sulfonamide
and CN groups (expected 58%). The third step occur with a weight
loss of 41.4% ending at 500 °C. This is probably due to decomposi-
tion of the benzene ring (expected 41.8%).
The DT curve shows and endothermic processes at
approximately 172.9 °C, without weight loss in the TG curve corre-
sponding to the melting point.
Fig. 1. Molecular plot of the p-cyanobenzenosulfonamide showing the labeling of
the non-hydrogen atoms and their displacement ellipsoids at the 50% probability
level.

G.E. Camí et al. / Journal of Molecular Structure 1024 (2012) 110–116
113
Fig. 2. Molecular plot of the p-cyanobenzenosulfonamide copper complex.
Fig. 3. (a) Projection of the p-cyanobenzenosulfonamide copper complex down the crystal a-axis. (b) Diagram showing the corrugated N–Hꢁ ꢁ ꢁO contacts layer. For clarity,
benzene moiety and cyano group are not included. Contacts are represented in dashed lines.
Two endothermic peaks are observed at 298 and 322 °C due to
the coordinated groups. Finally and endothermic one with maxi-
mum at 550 °C is also displayed.
of the ligand. A second group of exothermic peaks is observed at
375, 384, 389 and 409 °C, and corresponds to the complete decom-
position of the ligands and to the oxidation process described for
the TG curve interpretation.
3.2.2. TG-DT of the complex
The TG curve of the complex reveals that the decomposition
takes place in three steps. The two first ones correspond to a
weight loss of 6.82% which is consistent with the evolution of
the two NH3 groups (loss of weight calculated 7.30%). These pro-
cess take place with two endothermic peaks observed in DT curve
at 137 °C and 186 °C. The third step occurs with a weight loss of
52.73% corresponding to the decomposition of the benzene ring
and the coordinated groups as CN and NH (loss of weight calcu-
lated 51.52%). This value may be assigned to the reaction of the
SO2 group with Cu and a partial oxidation to cupric sulfate, as ob-
served in the infrared spectra of the residue. This fact was also ob-
served in a thermogravimetric study of the sulfonamide copper
complexes [24,28]. The DT curve shows three exothermic peaks
at 178, 190 and 214 °C corresponding to the partial decomposition
3.3. Spectroscopic properties
3.3.1. IR and Raman spectra
The observed Raman and FTIR bands of the p-cyanobenezeno-
sulfonamide (1) and its Cu(II) complex (2) are shown in Fig. 4
and the most significant experimental and calculated frequencies
are given in Table 4. The spectrum of the complex was compared
with the one of the free sulfonamide in order to determine the
coordination sites that may be involved in chelation. It was also
compared with those of previously reported similar complexes
[24–32].
The most remarkable difference is noticed in the band corre-
sponding to the sulfonamide stretching vibrations. The FTIR spec-
trum of the ligand (1) shows bands at 3350–3250 cmꢀ1 and at

114
G.E. Camí et al. / Journal of Molecular Structure 1024 (2012) 110–116
Table 2
Selected bond distances (Å), bond angles (°), and torsional angles (°) for ligand (1) and
complex (2).
10
8
a
Parameter
1
2
Exp.
Calc.
Exp.
Calc.
Cu1–N1
Cu1–N3
S1–O1
S1–O2
S1–N1
C11–S1
C11–C12
C12–C13
–
–
–
–
1.983(2)
2.002(3)
1.449(2)
1.445(2)
1.554(2)
1.788(3)
1.375(4)
1.387(4)
1.388(5)
1.450(4)
1.123(5)
88.7(1)
105.1(1)
110.9(1)
109.5(1)
115.4(1)
120.9(3)
119.9(2)
179.0(5)
37.9(3)
1.991
2.074
1.472
1.486
1.619
1.815
1.398
1.393
1.406
1.436
1.164
88.54
104.9
107.2
107.9
119.9
119.6
119.6
179.7
89.1
6
1.420(2)
–
1.463
1.463
1.677
1.809
1.397
1.393
1.406
1.436
1.163
–
106.9
105.6
107.3
123.5
119.2
119.1
179.8
90.0
22.9
–
410
520
2233
b
1.601(3)
1.777(4)
1.377(3)
1.386(5)
1.383(4)
1.461(7)
1.129(6)
1617
4
839
646
567
1207
C13–C14
C14–C21
C21–N2
2
3364
3276
977
N1–Cu1–N3
C11–S1–O1
N1–S1–O1
N1–S1–C11
O1–S1–O1 or O2
C12 or C16–C11–C12
C12–C11–S1
C14–C21–N2
C12–C11–S1–N1
O1–S1–C11–C12
O1–S1–N1–Cu1
O2–S1–C11–C16
O2–S1–N1–Cu1
–
0
107.4(1)
106.6(1)
108.7(2)
119.6(2)
122.5(4)
118.7(2)
178.3(6)
88.7(3)
ꢀ26.4(3)
–
c
d
-2
4000 3500 3000
2000
1500
1000
500
Fig. 4. 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.
ꢀ81.0(3)
ꢀ175.1(2)
ꢀ24.8(3)
ꢀ46.1(2)
44.4
86.1
26.5
14.8
–
–
–
–
Raman) under complexation. This is in agreement with the shorten-
ing of the S–N bond length relative to that of the uncoordinated li-
gand as was discussed in Section 3.1.
Table 3
Selected non-bonded contacts (Å) and angles (°).
The nature of the metal–ligand bond is confirmed by the new
bands that develop at 410 and 365 cmꢀ1 in the IR and Raman spec-
tra of the complex, which are assigned to Cu–NH and Cu–NH3
vibrations, respectively (calc. 422 and 383 cmꢀ1, correspondingly)
[24,31].
D–Ha
HꢁꢁꢁAa
DꢁꢁꢁAa
D–HꢁꢁꢁAa
Compound 1
N1–H1ꢁ ꢁ ꢁO1i
0.981
1.02
1.97
2.59
2.931(3)
3.565(5)
166.4
160.1
C13–H13ꢁ ꢁ ꢁN2ii
Complex 2
3.3.2. Electronic absorption spectra
N1–H1ꢁ ꢁ ꢁO1iii
N3–H33ꢁ ꢁ ꢁO1iii
N3–H31ꢁ ꢁ ꢁO2iv
N3–H32ꢁ ꢁ ꢁO2v
N3–H32ꢁ ꢁ ꢁS1v
0.86
0.85
0.83
0.89
0.89
2.41
2.32
2.30
2.35
2.81
3.039(3)
3.119(3)
2.936(3)
3.229(3)
3.671(3)
130.9
158.5
134.4
167.6
161.5
The electronic absorption spectra of the ligand (1) and complex
(2) were first determined in DMSO. However the results obtained
for the complex, together with the color change of the solution
suggest that it undergoes some decomposition in DMSO. For that
reason the spectrum was determined in solid state in KBr pellet.
The spectrum of the ligand was determined in the same conditions
for consistency.
Symmetry codes: (i) ꢀx + 1/2, ꢀy, z ꢀ 1/2; (ii) ꢀx, y ꢀ 1/2, ꢀz ꢀ 1; (iii) ꢀx + 1, ꢀy ꢀ 1,
ꢀz + 1; (iv) ꢀx + 1, ꢀy, ꢀz + 1; (v) x ꢀ 1, y, z
a
D = C or N and A = N, O, or S.
The spectrum of the ligand (1) shows four intense bands at 245,
273, 282 together with a weak one at 333 nm, (in DMSO the ob-
served bands are: 258, 278, 286 and a weak one at 324 nm). Similar
features are displayed in the DMSO calculated spectrum, for the
molecule modeled as deprotonated in the sulfonamide end. The in-
tense bands at 286, 278 and 258 nm are in agreement with calcu-
lated transitions at 276 (oscillator strength f = 0.08), 272 (f = 0.03)
1560–1500 cmꢀ1, which are assigned to stretching and bending
vibrations of the sulfonamide NH2 groups, respectively. Table 4
shows a shifting of these bands in the complex (see Table 4). The
appearance of a new band at 3447 cmꢀ1 observed in the IR spec-
trum of the complex is indicative of the presence of coordinating
NH3 [23,27]. The strong band at 3350 and the doublet at 3268
and 3255 cmꢀ1 are due to the asymmetric and symmetric modes
of the NH2 groups. An important feature in the spectrum of the
complex is that the band at 3255 cmꢀ1 is absent, indicating depro-
tonation of the amino group.
and 250 nm (f = 0.12) assigned to n ? pꢃ, n ? pꢃ and
p ?
pꢃ tran-
sitions respectively. An additional band is calculated at 322 nm
(f = 0.02), originated in HOMO–LUMO transitions, for the HOMO
centered in the sulfonamide N atom and the LUMO in the benzene
moiety. The UV–VIS spectrum of the solid ligand is not easily cal-
culated as the molecule is involved in a network of H-bonded inter-
actions as shown in Fig. 2, characterized by N–Hꢁ ꢁ ꢁO bonds with
non-bonded Hꢁ ꢁ ꢁO distances of 1.968 Å. The associated N–H dis-
tance is slightly larger than the average values reported for other
sulfonamide complexes (0.981 vs 0.8 Å) [33–35]. These conditions
cannot be modeled through the optimization of a single molecule,
which does not represent either the periodicity of the solid struc-
ture, leading to shorter N–H distances and no H-bonds. An ensem-
ble of two molecules or the modeling of explicit water molecules to
mimic the H-bond coordination did not give either the expected
result in the calculated spectrum. In all the cases no calculated
bands develop before 270 nm. However, the n ? pꢃ transitions
The strong band at 2228 cmꢀ1 in the spectra of the ligand is
attributed to m
(CN) vibrations. This band is shifted to 2231 cmꢀ1
(calc. 2228 cmꢀ1) and reduce its intensity after complexation. The
asymmetric and symmetric modes of SO2 groups appear at 1332
and at 1096 cmꢀ1, respectively. The asymmetric mode is shifted
to 1207 cmꢀ1 (calc. 1225 cmꢀ1) and the symmetric one remains
almost unchanged in the complex, 1099 cmꢀ1 (calc. 1062 cmꢀ1).
In the Raman spectra the asymmetric mode appears at
1334 cmꢀ1 and is not observed after complexation. However, the
symmetric one is observed at 1092 in the ligand and at
1097 cmꢀ1 in the complex. The band at 904 cmꢀ1 in the IR spectrum
of the ligand and at 900 cmꢀ1 in Raman spectrum is attributed to
the
m
(S–N) vibrations which is shifted to 977 cmꢀ1 (986 cmꢀ1 in

G.E. Camí et al. / Journal of Molecular Structure 1024 (2012) 110–116
115
Table 4
Observed FTIR and Raman bands and calculated IR frequencies and Raman amplitudes, in cmꢀ1, of p-cyanobenzenosulphonamide and copper complex.
Ligand
Complex
Infrared
Assignments
Infrared
B3LYP
Raman
B3LYP
Raman
3447 sh
3380 vs
3364 vs
3283 vs
3276 vs
3088 w
2231 m
1617 m
1597 w
3451
3392
3386
3205
3187
3116
2228
1620
1607
ma NH3
m
(
(
N–H
ma NH2)
ms NH2
3350 vs
3268 vs/3255 vs
3493
3370
m
) m
N–H
N–H
3257 vw
ms NH3
3096 m
2228 vs
3081
2234
3080 w
2228 vs
3078 m
2234 vs
m
m
C–H
CN
d NH3
C–H + ring
d NH2
C–C
mas SO2 d NH2
C–C
1595 m
1555 m
1344 s
1332 s
1288 w
1166 s
1568
1528
1365
1283
1274
1597 vs
1595 s
m
1338 m
1207 m
1293 m
1169 w
1133 s
1099 s
977 s
839 m
700 w
646 m
600 sh
567 s
1364
1225
1275
1176
1139
1062
855
820
706
614
591
m
1334 vw
1163 s
m
1188 m
d NH2 + d NH3
d NH3
1096 s
904 s
839 s
1084
786
1092 m
900 m
842 vw
1097 sh
986 m
ms SO2
S–N
Ring
NH3
+ m C–S + ring
m
x
645 m
623
639 m
641 m
d NH + d NH3
Ring
d SO2 + ring
560 s
524 m
514 m
600
524
563 vw
524 vw
514 vw
555
q
NH2
520 s
410 w
439 w
513
422
Ring
m
Cu–NH
435 w
438 m
270 m
Ring
383
365 w
276 w
m
Cu–NH3
Lattice
should be strongly influenced by the charge density on the sulfon-
amide N atom, and hence by the N–H distance. As previously
shown for the DMSO modeled case, the band ꢄ320 nm is only cal-
culated for the negative species, leading us to assume that at least
some NH bonds should be lengthened in the solid phase.
These data can be obtained free of charge via http://www.
ccdc.ca-m.ac.uk/conts/retrieving.html, or from the Cambridge
Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ,
UK; fax: +44 1223 336 033; or e-mail: deposit@ccdc.cam.ac.uk.
The experimental spectrum of the complex shows a low inten-
sity, broad absorption bands centered at 737 and 592/505 nm (cal-
culated at 732 and 532 nm) originated in a ligand to metal charge
transfer transition to the d-centered LUMO orbital. The band at
732 nm is calculated with intensity zero, but can gain intensity
through vibronic coupling. Several bands are calculated between
490 and 450 nm, with no intensity, originated in d–d transitions,
followed by n ? pꢃ transitions at 384–380 nm and ligand to metal
Acknowledgments
D.B.S., M.E.Ch.V. G.A.E. and P.C. thanks CONICET (CEQUINOR,
PIP0356 and PIP 1529), ANPCyT (PME06 2804 and PICT06 2315),
SUBCYT and CICPBA, República Argentina, for financial support.
G.E.C. thanks to the University of San Luis and G.E. thanks to the
Center for Research Computing at the University of Notre Dame.
charge transfer between 354 and 305 nm. Calculated
p ?
pꢃ transi-
References
tions start at 295 nm. As for the case of the ligand, the position of the
bands can be strongly affected by the structure of the solid (see
Fig. 4). This is particularly important for the charge transfer
transitions.
[1] A. Scozzafava, T. Owa, A. Mastrolorenzo, C.T. Supuran, Curr. Med. Chem. 10
(2003) 925.
[2] M.A. Ilies, Metal complexes of sulfonamides as dual carbonic anhydrase
inhibitors, in: C.T. Supuran, J.-Y. Winum (Eds.), Drug Design of Zinc–Enzyme
Inhibitors: Functional, Structural, and Disease Applications, John Wiley
&
Sons, Inc., Hoboken, NJ, USA, 2009, pp. 439. http://dx.doi.org/10.1002/
9780470508169.ch21.
4. Conclusions
[3] A. Bult, Met. Ions Biol. Syst. 16 (1983) 261.
[4] M. Dizdaroglu, Free Radic. Biol. Med. 10 (1991) 225.
[5] L.M. Rossi, A. Neves, A.J. Botoluzzi, R. Hörner, B. Szpoganicz, H. Terenzi, A.S.
Mangrich, E. Pereira-Maia, E.E. Castellano, W. Haase, Inorg. Chim. Acta 358
(2005) 1807.
[6] CAD4 Express Software, Enraf–Nonius, Delft, The Netherlands, 1994.
[7] K. Harms, S. Wocadlo, XCAD-4, Program for Processing CAD-4 Diffractometer
Data, University of Marburg, Germany, 1995.
[8] CrysAlisPro, Oxford Diffraction Ltd., Version 1.171.33.48 (Release 15–09-2009
CrysAlis 171.NET).
[9] G.M. Sheldrick, Acta Cryst. A64 (2008) 112.
This study reports the synthesis and characterization of the
p-cyanobenzenosulfonamide and a new Cu(II) complex [Cu(L)2-
(NH3)2]. Both compounds were structurally characterized via
X-ray crystallography. Their UV, IR and Raman properties are in a
good agreement with the X-ray crystallography. B3LYP calcula-
tions have been used to compare the structural characteristics
and to better assign the spectroscopic features. The agreement
with the experimental excitation energies and intensities shows
that the theoretical description of the electronic and vibrational
structure are essentially correct.
[10] A.L. Spek, Acta Crystallogr., Sect. A C34 (1990) 46.
[11] M. Nardelli, J. Appl. Crystallogr. 28 (1995) 659.
[12] M.N. Burnett, C.K. Johnson, ORTEP-III Report ORNL-6895, Oak Ridge National
Laboratory, Oak Ridge, Tennessee, USA, 1996.
[13] L.J. Farrugia, WinGX, An Integrate System of Windows Programs for the
Solution, Refinement and Analysis of Single Crystal X-Ray Diffraction Data,
Dept. of Chemistry, University of Glasgow, 1997–2003.
[14] C.F. Macrae, P.R. Edgington, P. McCabe, E. Pidcock, G.P. Shields, R. Taylor, M.
Towler, J. van de Streek, J. Appl. Cryst. 39 (2006) 453.
Supplementary data
CCDC 849244 and CCDC 849243 contain the supplementary
crystallographic data for 1 and 2 respectively.
[15] B. Murphy, B. Hathaway, Coord. Chem. Rev. 243 (2003) 237.

116
G.E. Camí et al. / Journal of Molecular Structure 1024 (2012) 110–116
[16] M.J. Frisch, G.W. Trucks, H.B. Schlegel, G.E. Scuseria, M.A. Robb, J.R. Cheeseman,
G. Scalmani, V. Barone, B. Mennucci, G.A. Petersson, H. Nakatsuji, M. Caricato,
X. Li, H.P. Hratchian, A.F. Izmaylov, J. Bloino, G. Zheng, J.L. Sonnenberg, M.
Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hasegawa, M. Ishida, T. Nakajima, Y.
Honda, O. Kitao, H. Nakai, T. Vreven, J.A. Montgomery Jr., J.E. Peralta, F. Ogliaro,
M. Bearpark, J.J. Heyd, E. Brothers, K.N. Kudin, V.N. Staroverov, R. Kobayashi, J.
Normand, K. Raghavachari, A. Rendell, J.C. Burant, S.S. Iyengar, J. Tomasi, M.
Cossi, N. Rega, J.M. Millam, M. Klene, J.E. Knox, J.B. Cross, V. Bakken, C. Adamo,
J. Jaramillo, R. Gomperts, R.E. Stratmann, O. Yazyev, A.J. Austin, R. Cammi, C.
Pomelli, J.W. Ochterski, R.L. Martin, K. Morokuma, V.G. Zakrzewski, G.A. Voth,
P. Salvador, J.J. Dannenberg, S. Dapprich, A.D. Daniels, Ö. Farkas, J.B. Foresman,
J.V. Ortiz, J. Cioslowski, D.J. Fox, Gaussian 09, Revision ꢃA.02ꢃ, Gaussian, Inc.,
Wallingford, CT, 2009.
[22] I.J. Bruno, J.C. Cole, P.R. Edgington, M. Kessler, C.F. Macrae, P. McCabe, Acta
Cryst. B58 (2002) 389.
[23] CCCD, A Program for the Analysis and Display of Data Retrieved from the CSD,
Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge, England,
1994.
[24] B. Mennucci, J. Tomasi, R. Cammi, J.R. Cheeseman, M.J. Frisch, F.J. Devlin, S.
Gabriel, J. Phys. Chem. A106 (2002) 6102.
[25] G.E. Camí, E.E. Chufán, J.C. Pedregosa, E.L. Varetti, J. Mol. Struct. 570 (2001) 119.
[26] B. Macías, M.V. Villa, E. Fiza, I. García, A. Castiñeiras, M. Gonzalez-Alvarez, J.
Borrás, J. Inorg. Biochem. 88 (2002) 101.
[27] B. Murphy, B. Hathaway, Coord. Chem. Rev. 243 (2003) 237.
[28] C. Pedregosa, J. Casanova, G. Alzuet, J. Borrás, S. Garcia-Granda, M.R. Diaz, A.
Gutierrez-Rodriguez, Inorg. Chim. Acta 232 (1995) 117.
[29] E. Kremer, G. Facchin, E. Estévez, P. Alborés, E.J. Baran, J. Ellena, M.H. Torre, J.
Inorg. Biochem. 100 (2006) 1167.
[17] A.D. Becke, D.R. Yarkony, Modern Electronic Structure Theory Part II, World
Scientific, Singapore, 1995.
[18] L. Radom, P.v.R. Schleyer, J.A. Pople, Ab Initio Molecular Orbital Theory, John
Wiley & Sons, New York, 1986.
[30] B. Macías, I. García, M.V. Villa, J. Borrás, M. González-Álvarez, A. Castiñeiras,
Inorg. Chim. Acta 353 (2003) 139.
[19] (a) P.J. Hay, W.R. Wadt, J. Chem. Phys. 82 (1985) 270;
(b) W.R Wadt, P.J. Hay, J. Chem. Phys. 82 (1985) 284.;
[31] E. Borrás, G. Alzuet, J. Borrás, J. Server-carrió, A. Castiñeiras, M. Liu-González, F.
Sanz-Ruiz, Polyhedron 19 (2000) 1859.
(c) P.J. Hay, W.R. Wadt, J. Chem. Phys. 82 (1985) 299.
[32] M. González-Álvarez, G. Alzuet, J. Borrás, S. García-Granda, J.M. Montejo-
Bernardo, J. Inorg. Biochem. 96 (2003) 443.
[33] B. Malika, B. Radia, A. Nour-Eddine, B. Carrole, X-ray Struct. Anal. Online 26
(2010) 13.
[20] (a) D.L. Harris, Curr. Opin. Chem. Biol. 5 (2001) 724;
(b) L. Noodleman, T. Lovell, W.G. Han, J. Li, F. Himo, Chem. Rev. 104 (2004)
459;
(c) E.I. Solomon, R.K. Szilagyi, S. DeBeer, G.L. Basumallick, Chem. Rev. 104
(2004) 419;
(d) G. Estiu, K.M. Merz Jr., J. Phys. Chem. B111 (2007) 10263.
[21] F.H. Allen, Acta Cryst. B58 (2002) 380.
[34] M. Mondelli, V. Brune, G. Borthagaray, J. Ellena, O.R. Nascimento, Q. Clarice,
C.Q. Leite, A.A. Batista, M.H. Torre, J. Inorg. Biochem. 102 (2008) 285.
[35] C.A. Otter, S.M. Couchman, J.C. Jeffery, K.L.V. Mann, E. Psillakis, M.D. Ward,
Inorg. Chim. Acta 278 (1998) 178.