Synthesis, crystal structure, spectroscopic, thermogravimetric and theoretical characterization of Ni(II) and Zn(II) complexes with 4-chloro-2-nitrobenzenesulfonamide

Article abstract of DOI:10.1016/j.molstruc.2013.11.058

Two new complexes of Ni and Zn with 4-chloro-2-nitrobenzenesulfonamide (ClNbsa) have been synthesized and characterized. The structure of the [Ni(ClNbsa)₂(NH₃)₄] complex was determined by X-ray diffraction methods. It crystallizes in the monoclinic P2₁/c space group with a = 12.8679(3) ?, b = 7.7254(1) ?, c = 12.2478(2) ?, β = 109.899(2), V = 1144.85 (4)?³ and Z = 4 molecules per unit cell. The coordination geometry of the Nickel (II) ion in the complex can be described as a distorted octahedron with two N-sulfonamide and four NH₃ groups in opposite vertices. Due to the poor solubility of the Zn(II) complex, their cell parameters were determined by indexing the powder X-ray pattern using the successive dichotomy method implemented in the Fullprof Suite software package. A triclinic cell was determined with cell parameters a = 18.3724(1) ?, b = 7.9468(8) ?, c = 10.2212(9) ? α = 63.061(6) β = 108.754(6) γ = 109.153(6) and V = 1229.97(2) ?³. Nuclear magnetic resonance (NMR) spectroscopy of ¹H and ¹³C have been used for support the structure of the Zn complex. Vibrational and electronic spectroscopy have been used to characterize the compounds, using theoretical calculations for the assignment of the experimental bands. The thermal behavior was investigated by thermogravimetric analyses (TG) and differential thermal analysis (DT).

Full text of DOI:10.1016/j.molstruc.2013.11.058

Journal of Molecular Structure 1062 (2014) 82–88
Contents lists available at ScienceDirect
Journal of Molecular Structure
journal homepage: www.elsevier.com/locate/molstruc
Synthesis, crystal structure, spectroscopic, thermogravimetric and
theoretical characterization of Ni(II) and Zn(II) complexes with
4-chloro-2-nitrobenzenesulfonamide
G. Estiu a, M.E. Chacón Villalba b, G.E. Camí c, G.A. Echeverria d, D.B. Soria b,
⇑
a Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556, USA
b CEQUINOR, Departamento de Química, Facultad de Ciencias Exactas, Universidad Nacional de la Plata, 47 y 115 (1900) La Plata, Buenos Aires, Argentina
c 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
d IFLP (CONICET La Plata)-Departamento de Física, Facultad de Ciencias Exactas, Universidad Nacional de La Plata 49 y 115 (1900) La Plata, Buenos Aires, Argentina
h i g h l i g h t s
ꢀ
ꢀ
ꢀ
Ni and Zn with 4-chloro-2-nitrobenzenesulfonamide complexes have been prepared.
The structure of the nickel complex was determined by X-Ray diffration methods.
FTIR, Raman and UV-VIS spectra have been assigned on the basis of DFT calculation.
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 20 August 2013
Received in revised form 28 November 2013
Accepted 28 November 2013
Available online 7 December 2013
Two new complexes of Ni and Zn with 4-chloro-2-nitrobenzenesulfonamide (ClNbsa) have been synthe-
sized and characterized. The structure of the [Ni(ClNbsa)2(NH3)4] complex was determined by X-ray dif-
fraction methods. It crystallizes in the monoclinic P21/c space group with a = 12.8679(3) Å,
b = 7.7254(1) Å, c = 12.2478(2) Å, b = 109.899(2)°, V = 1144.85 (4)Å3 and Z = 4 molecules per unit cell.
The coordination geometry of the Nickel (II) ion in the complex can be described as a distorted octahe-
dron with two N-sulfonamide and four NH3 groups in opposite vertices. Due to the poor solubility of the
Zn(II) complex, their cell parameters were determined by indexing the powder X-ray pattern using the
successive dichotomy method implemented in the Fullprof Suite software package. A triclinic cell was
Keywords:
4-Chloro-2-nitrobenzenosulfonamide
Ni(II) and Zn(II) complexes
Spectroscopic properties
X-Ray structure
determined with cell parameters a = 18.3724(1) Å, b = 7.9468(8) Å, c = 10.2212(9) Å
a = 63.061(6)
b = 108.754(6)
c
= 109.153(6) and V = 1229.97(2)Å3. Nuclear magnetic resonance (NMR) spectroscopy
of 1H and 13C have been used for support the structure of the Zn complex. Vibrational and electronic spec-
troscopy have been used to characterize the compounds, using theoretical calculations for the assign-
ment of the experimental bands. The thermal behavior was investigated by thermogravimetric
analyses (TG) and differential thermal analysis (DT).
Density functional calculations
Ó 2013 Elsevier B.V. All rights reserved.
1. Introduction
years due to their interesting properties. They are recognized as
antitumor, antibacterial, diuretic, hypoglycaemic and anti-thy-
The use of metal based therapeutics for both diagnosis and
treatment of diseases constitutes a new field of increasing interest.
Metal ions have been always relevant in biological systems, [1,2]
with several diverse features determining the characteristics of
metal coordinated systems, as the spatial arrangement of the
ligands around the metal ion.
roid pro-drugs and protease inhibitors [3–6]. In general, metal
complexes of heterocyclic sulfonamides possess much stronger
carbonic anhydrase (CA) inhibitory properties than the sulfona-
mides from which they were prepared [7,8]. On the other hand,
binary and ternary complexes of transition metals are usually
found in biological media and might play important roles in pro-
cesses as diverse as the catalytic interaction of viruses with bac-
terial cell walls, or the transport and storage of oxygen [9]. In
view of the versatile importance of metal complexes and in order
to identify their coordination properties, we have previously
reported the results of the structural and electronic investigations
The coordination chemistry of simple and N-substituted sul-
fonamides has also undergone noticeable development in recent
⇑
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 2013 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.molstruc.2013.11.058

G. Estiu et al. / Journal of Molecular Structure 1062 (2014) 82–88
83
Table 1
of p-cyanobenzenosulfonamide (L), and its copper(II) complex
Crystal data and structure refinement for [Ni (ClNbsa)2(NH3)4] complex.
[10]. We also prepared and characterized a new copper(II) com-
plex, [Cu(L)2(NH3)2], with the 4-chloro-2-nitrobenzenesulfona-
mide as ligand [11].
Empirical formula
C12H20Cl2N8NiO8S2
Formula weight
Temperature
598.09
295(2) K
The structures of both were analyzed computationally, render-
ing stable conformations for the free sulfonamide and for the cop-
per complex, and suggesting for the latter a distorted square planar
geometry. In light of the interesting coordination chemistry of
these compounds, herein we describe the synthesis of two com-
plexes with 4-chloro-2-nitrobenzenesulfonamide (in further text
denoted as L) with formula Ni(L)2(NH3)4 and Zn(L)2(NH3)2. Their
characterization by means of X-ray diffraction, thermogravimetry,
FTIR, Raman, NMR and UV–VIS spectra is also discussed. The
assignment of experimental electronic, infrared and Raman bands
was accomplished with the aid of theoretical results based in
density functional theory.
Wavelength
0.71073 Å
Crystal system
Space group
Monoclinic
P 1 21/c 1
Unit cell dimensions
a = 12.8679(3) Å
b = 7.72540(10) Å
c = 12.2478(2) Å
b = 109.90(2)°
Volume
1144.85(4) Å3
Z, Density (calculated)
Absorption coefficient
F(000)
4, 1.735 Mg/m3
1.320 mmÀ1
612
Crystal size
0.337 Â 0.278 Â 0.189 mm3
Crystal shape/color
h-range for data collection
Index ranges
Reflections collected
Independent reflections
Observed reflections [I > 2
Completeness to h = 26.50°
Absorption correction
Max. and min. transmission
Refinement method
Prism/bluish
3.18–28.95°
À17 6 h 6 16, À10 6 k 6 10, À15 6 l 6 16
19379
2. Experimental
2841 [R(int) = 0.0206]
2390
93.4%
Semi-empirical from equivalents
1.00000 and 0.97369
Full-matrix least-squares on F2
2841/0/157
r(I)]
2.1. Materials and methods
The FTIR spectra were carried out with an EQUINOX 55 spec-
trophotometer, in the range from 4000 to 400 cmÀ1 using the
KBr pellet technique, with a spectral resolution of 4 cmÀ1. The
Raman spectra were recorded with a Bruker IFS 66 FTIR spectro-
photometer provided with the NIR Raman attachment, with a res-
olution of 4 cmÀ1. 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 sate with KBr reference pellet. They were re-
corded with a Hewlett–Packard 8452-A diode array spectrometer,
using 10 mm quartz cells. DT and TG analyses were performed
using Shimadzu TGA-50 and DTA-50H units at a heating rate of
5 °C/min. and oxygen flow of 50 ml/min. NMR spectra were
carried out with an Spectrophotometer 500 MHz multinuclear,
Bruker Avance II 500
Data/restraints/parameters
Goodness-of-fit on F2
1.007
Final Ra indices [I > 2
R indices (all data)
r
(I)]
R1 = 0.0251, wR2 = 0.0654
R1 = 0.0319, wR2 = 0.0672
0.230 and À0.425 e ÅÀ
3
Largest diff. peak and hole
a
R1
=
R
||Fo|-|Fc||/
R
|Fo|, wR2 = [
R
w(|Fo|2À|Fc|2)2/
R .
w(|Fo|2)2]1/2
2.3. Computational methods
The computational study of the complexes was performed using
the density functional theory (DFT) methods implemented in
Gaussian 09 [17].
The systems studied herein were subjected to unrestrained en-
ergy minimizations using the (B3LYP [18] functional with the 6-
31 + G** basis set [19,20] for non-metal atoms and the Los Alamos
effective core potentials LANL2DZ [20,21] for the metal. The vibra-
tional frequencies were calculated from the second derivatives and
on this basis the vibrational modes have been assigned. In order to
model the UV–VIS spectra experimentally determined in DMSO,
the geometries were optimized, at the same level, under the sol-
vent condition (Polarizable Continuous Model, PCM) [21–23]. The
same solvent model was used in the time dependent DFT calcula-
tions (TDDFT). 90 electronic transitions were analyzed using the
Merz–Kollman electron density.
2.2. X-ray diffraction data
The data for the Nickel complex were collected on an Agilent
Gemini Diffractometer with an EOS CCD detector equipped with a
graphite-monochromated Mo K
a
(k = 0.71073 Å) radiation. X-ray
scans with h and -offsets),
diffraction intensities were collected (
x
j
integrated and scaled with CrysAlisPro [12] suite of programs. The
unit cell parameters were obtained by least-squares refinement
(based on theangular settings for all collectedreflections withinten-
sities larger than seven times the standard deviation of measure-
ment errors) using CrysAlisPro Data were corrected empirically for
absorption employing the multi-scan method implemented in
CrysAlisPro. The structure was solved by direct methods with
SHELXS-97 [13] and the molecular model refined by full-matrix
least-squares procedure on F2 with SHELXL-97 [14,15].
2.4. Synthesis of the complexes
The hydrogen atoms were positioned stereo-chemically and re-
fined with the riding model. The angular locations of the ammonia
groups were optimized during the refinement by treating them as
rigid bodies allowed to rotate around the Ni-NH3 bond. Crystal
data and refinement results are summarized in Table 1.
The X-ray powder diffraction data (XRPD) were collected on a
Philips PW1710 powder diffractometer with a scintillation counter
and an exit beam graphite monochromator using Cu Ka radiation
(k = 1.5406 Å). The 2h range covered was from 4° to 95° with a step
interval of 0.02° and a counting time of 3 s. The XRPD pattern was
analyzed using the DICVOL4 program as implemented in the
Fullprof code [16].
4-Chloro-2-nitrobenzenesulfonamide (L) was purified by sev-
eral crystallizations from ethyl acetate /hexane.
The metal complexes were prepared by direct reaction of
ethanol solutions of sulfonamide and metal(II) chloride in the
2:1 M ratio, followed by drop wise addition of 2 ml of 2 M
NH3, under continuous stirring. The resulting mixture was stir-
red during ca. 4 h. and was then left to stand at room tempera-
ture. Slow evaporation of the solution of the Ni complex
provided well-developed violet crystals that were suitable for
X-ray diffraction. They were collected by filtration washed and
dried. For Zn complex, slow evaporation of the solution pro-
vided a white powder.

84
G. Estiu et al. / Journal of Molecular Structure 1062 (2014) 82–88
Analytical calculation for C12H20Cl2N8NiO8S2 (%) C, 24.08%; H,
3.34%; N, 18.73%; S: 10.70%. Found: C, 24.12%; H, 3.35%; N,
18.75%, S 10,72%.
C12H16Cl2ZnN6O4S2(%) C, 25.4%; H, 2.8%; N, 14.8%; S, 11,20%
Found: C, 25.61%; H, 2.6%; N, 14.3%; S, 11.23%
3. Results and discussion
3.1. Structure
The experimentally determined bond distances and angles
around the Ni(II) cation in the [Ni (L)2(NH3)4] complex are listed
in Table 2. Fig. 1 shows the coordination sphere and the labeling
scheme used. The Ni(II) cations are located on an inversion center
octahedrally coordinated by four equatorial ammonia at a NÁ Á ÁNi
distances of 2.113(1) and 2.146(1) Å and two axial sulfonamide
nitrogen atoms at a NÁ Á ÁNi distance of 2.151(1) Å forming a C1–
S1–N1–Ni torsional angle of 112.9(1)°. These values are in good
agreement with those observed in other similar sulfonamide nick-
el(II) complex where the Ni(II) cation coordinates also with four
ammonia molecules, at distances N–Ni of 2.092 Å and 108.8(5)
respectively [24]. The C1–S1–N1–Ni torsional angle values ob-
served in these systems are larger than those found by the same
authors in the hydrated methazolamide and pyridine nickel com-
plex, 86.2(2)° [25]. The lower value might be attributed to the fact
that the thiadiazole and pyridine rings [24] are in a paralallel
arrangement at a distance of 3.683(2) Å. The sulfonamide nitrogen
Fig. 1. Plot of Ni[(ClNbsa)2(NH3)4] complex showing the labeling of the indepen-
dent non-H atoms and their displacement ellipsoids at the 30% probability level.
The H-bonding structure is denoted by dashed lines. Os: Oxygen atoms belonging to
sulfonamide groups of another molecule.
atom is located very close to the benzene ring plane, forming the
N1–S1–C1–C6 torsional angle of 6.3(1)°, with a S–N bond distance
of 1.534(1) Å (see Table 2). These values are similar to those
Table 2
Angles and Interatomic Distances Observed and Calculated.
Bond distances (Å)
S–O
X-Ray observed
B3LYP Ni (II) Complex
B3LYp Zn(II) Complex
1.4602 (13)
1.4412 (12)
1.5340 (13)
1.7932 (15)
1.7336 (17)
1.215 (2)
1.204
1.388 (2)
1.373 (2)
1.385 (2)
2.1128 (13)
2.1464 (15)
2.1508 (13)
1.215
1.4838
1.4846
1.4742
1.4867
1.6089
1.8357
1.3748
1.2245
1.2356
1.3980
1.3955
1.3953
2.1283
2.1671
2.0371
1.2249
1.4763
S–N
S–C
C–Cl
N–O
N–O
C–C
C–C
C–C
Ni–NH3
Ni–NH3
Ni–NH
O–N
1.61069
1.82893
1.7498
1.22959
1.22322
1.40138
1.3923
1.39273
2.16622
2.17016
2.19479
1.22322
1.47941
N–C
1.478 (2)
Angles (Deg)
O–S–O
O–S–N
O–S–C
O–N–O
C–C–C
C–C–C
C–C–S
C–C–N
S–NH–Ni
O(3)–N(2)–C(2)
N(1)–S(1)–C(1)
N(3)–Ni(1)–N(3)
N(3)–Ni(1)–N(4)
114.89
110.21 (8)
102.21
117.560
113.322
104.537
125.944
121.589
117.700
124.351
122.890
114.500
117.43
119.491
111.478
103.590
124.608
122.381
117.329
125.370
122.822
124.830
117.70
125.36 (18)
123.31(14)
116.96(14)
122.58 (11)
120.67
136.92 (8)
118.19 (16)
109.14 (7)
180.00 (10)
88.76 (6)
105.960
179.999
86.909
105.859
103.248
114.214
Torsion (Deg)
C–C–S–N
6.303
52.943
32.360
96.763
34.519
128.120
179.80
159.143
56.790
74.842
137.438
92.975
161.536
179.997
159.692
21.207
110.735
137.02
39.119
166.235
164.995
O–S–N–Me
O–S–N–Me
O–S–C–C
O–S–C–C2
S–N–Me–N
Cl–C–C–Cl

G. Estiu et al. / Journal of Molecular Structure 1062 (2014) 82–88
85
observed by Alzuet et al. [24,25]). The NO2 plane is rotated an angle
of 78.0(1)° from the benzene ring plane, which is larger than the
one calculated in gas phase for Cu(II) complex 29.56° [11]. The
structure is further stabilized by a network of hydrogen bond inter-
actions involving NH3 and the benzene hydrogen atoms with sul-
fonamide oxygen atoms see Table 3 and Fig. 1.
The geometry of the Ni complex optimized at the B3LYP/ level is
shown in Fig. 2(a front view and b lateral view). The gas phase opti-
mized structure is in close agreement with the experimentally
determined one (Table 2). The optimization in solvent keeps the
octahedral coordination and does not change significantly the
overall structure of the complex. A slight difference was observed
in the shortening of S–N distances, 1.58 Å in a solvent and 1.61
in gas phase
We were not able to obtain crystals of the Zn(II) complex. Con-
versely, a powder X-ray diffraction pattern was recorded (Fig. 3).
The cell parameters were determined by indexing the X-ray
powder pattern, employing the program DICVOL04 [16], included
in the Fullprof Suite software package: a = 18.372(8) Å,
Fig. 2. Geometry optimized structures for Ni complex in gas phase using B3LYP
level. (a) front view and (b) lateral view.
b = 7.947(3) Å,
c
c = 10.221(3) Å,
a=63.06(2)°,
b = 108.75(2)°,
=109.15(2)°, and cell volume = 1230(2) Å3 (figure of merit
M(20) = 10.5). The measured and calculated peak intensities are
shown in Fig. 3 together with the expected Bragg positions. The cell
volume, 85 Å3 larger than the one determined for the Ni(II) com-
plex, is consistent with two Zn(L)2(NH3)2 formula in the unit cell.
The structure of the Zn(II) complex was analyzed using compu-
tational techniques, after geometry optimizations using the B3LYP
functional. Two different geometries have been obtained in this
case, holding a tetrahedral coordination around the Zn center
(Fig. 4) but differing in the spatial distribution of the substituent
groups. In both cases the zinc ion is tetracoordinated by four N
atoms, two of them belonging to the NH3 ligands and the other
two belonging to the N–H of the sulfonamide deprotonated groups.
The calculated parameters of the complex in the optimized geom-
etry (see Fig. 4a) are in good agreement with those previously re-
ported for a similar cupper complex having a distorted square
planar geometry [11] and they are very close to the X ray structure
of another sulfonamide-Zn complexes [26].
In the gas phase optimization, B3LYP favors the linear structure
(see Fig. 4a) by 1.2 kcal/mol. This difference is not large enough to
disregard any of the structures. Moreover, in the packed crystal,
the linear structure shown in Fig. 4a would be more likely, as can
also be confirmed by the analysis of the IR spectra. The agreement
with the experimental FTIR bands is better when the linear struc-
ture is used for the calculations (See Table 2). The geometry
optimization in solvent favors the non-linear structure (Fig. 4b)
by 6.27 kcal/mol.
Fig. 3. Measured and calculated X-ray diffraction profiles and their difference plot
for the Zn complex.
ligand has been previously reported [11] and it is compared here
with those of the complexes in order to confirm which groups
are involved in chelation.
In the spectra of both complexes new bands are attributed to
the NH stretching vibrations of ammonia molecules. The positions
of the stretching bands due to NH2 groups are modified with regard
to the ligand, suggesting that this amino group is involved in the
coordination with the metal centre [11,12,25,26]. The strong band
observed at 3372 cmÀ1 and the shoulder at 3355 cmÀ1 in the IR
spectrum of the Ni(II) complex are indicative of the presence of
coordinating NH3 as can be observed in the Fig. 1. This result is
consistent with the weak band observed at 1612 cmÀ1 assigned
to the bending mode of this group and with the strong one at
662 cmÀ1 associated with its torsion mode. These modes are ob-
served at 3380, 3347, 1592 and 668 cmÀ1 respectively, in the infra-
red spectrum of the Zn(II) complex. The assignment of the
ammonia bands is bases on standard references [28] and in good
agreement with those for Ni(II) and Zn(II) mixed-ligand sacchari-
nato complexes containing ammonia as the second ligand [29].
The bands assigned to the SO2 groups are usually shifted to lower
frequencies under complexation, associated with the binding of the
sulfonamides through the deprotonated sulfonamido group
[11,12,24–27]. In the free ligands the assimetric and symmetric
3.2. Spectroscopic properties
3.2.1. FTIR and Raman spectra
The observed FTIR and Raman bands are shown in Fig. 5a and d
for the Ni(II) complexes, and in Fig. 5b and c for Zinc(II) complex.
The most significant IR and Raman data are reported in Table 4,
together with the theoretically derived ones. The IR data for the
Table 3
Hydrogen bonds distances and angles for 4-chloro-2-nitrobenzenosulfonamide.
Atoms
D–H
HÁ Á ÁA
DÁ Á ÁA
D–HÁ Á ÁA
N1–H1Á Á ÁO1i
0.81
0.89
0.89
0.89
2.33
2.30
2.29
2.16
3.129(2)
3.180(2)
3.148(2)
2.933(2)
167.3
170.1
160.6
145.4
N3–H3AÁ Á ÁO1i
N3–H3BÁ Á ÁO1ii
N3–H3CÁ Á ÁO2iii
Symmetry transformations used to generate equivalent atoms: (i) Àx + 1, Ày + 1,
Àz; (ii) x, Ày + 1/2, z-1/2; (iii) Àx + 1, Ày, Àz.

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G. Estiu et al. / Journal of Molecular Structure 1062 (2014) 82–88
Cl
(a)
(b)
1.225
1.61
Zn
1.61
1.230
2.034
Cl
Fig. 4. Two different geometries optimized structures for Zn complex in gas phase.
3.2.2. Electronic absorption spectra
The electronic absorption spectra of the complexes were mea-
sured in DMSO and compared with that of the ligand, previously
reported [11]. Two intense bands appear in the spectrum of the li-
gand at 286 and 266 nm, which can be assigned to
n ? * transitions, respectively [11]. An intense peak develops in
the Ni(II) UV–VIS spectrum at 260 nm with shoulders at 290 nm
and 340 nm, which are assigned to * and n ? * transitions
p ? p* and
p
p
?
p
p
centered in the sulfonamide ligand on the basis of the theoretical
calculations. At the present level of theory, bands are calculated
at 266 nm, 288 nm and 340 nm, with relative intensities of
f = 0.11, 0.0198, 00.628 respectively. The poorly resolved band ob-
served in the visible region at 616 nm (
culated at 653 nm (f = 0.0) and assigned to d–d transitions. This
band is absent in the Zn complex, while the * and n ? p*
e
. = 96026 cmÀ1 MÀ1) is cal-
p
?
p
transitions bands are observed at 320, 290 and 262 nm for the
structure shown in Fig. 4a. As previously mentioned, the geometry
optimization in solvent favors the non-linear structure (Fig. 4b) by
3.77 kcal/mol. Nevertheless, the position of the bands do not
change markedly, and are calculated at 330, 295 and 260 nm
Fig. 5. (a) FTIR and (d) Raman spectrum of the Zn complex, (b) FTIR and (c) Raman
spectrum of the Ni complex,
(f = 0.053, 0.005, 0.030), They are also assigned to
n ? * transitions.
p ? p* and
p
stretching of these modes appear at 1348 and 1060 cmÀ1
respectively [11]. In the spectrum of the nickel(II) complex the
asymm(SO2) and
symm(SO2) are shifted to 1255 and 1056 cmÀ1
,
m
m
,
respectively. These modes are observed at 1243 and 1058 cmÀ1
in the case of the Zn(II) complex. In the Raman spectra the asym-
metric mode of the nickel(II) complex is not observed after com-
plexation, but it develops as a very weak band at 1242 cmÀ1in
the zinc(II) spectrum. The symmetric one is observed at
1058 cmÀ1 for both complexes.
3.2.3. NMR spectroscopy
1H and 13C NMR spectra of the Zn complex in DMSO-d6 have
been measured to support the structural assignment and com-
pared to the ligand [11]. The 1H NMR spectrum shows three groups
of signals for the three different hydrogen atoms of the benzene
rings sulfonamide. The three groups are doublet and appear at
7.99 ppm (J = 1.9 Hz) 7.93 ppm (J = 8.5 Hz) and 7.61 ppm
(J = 7.7 Hz) slightly shifted respect to the ligand (8.15 ppm,
7.92 ppm and 7.73 ppm, respectively). The ligand signal at
5.4 ppm, due to the protons of the sulfonamide moiety does not
appear in the complex. The remaining signal as a broad doublet
at 3.03 ppm could be assigned to the hydrogen of the NH and
NH3 groups.
The m
(S–N) vibration is observed in the ligand at 923 cmÀ1, and
shifted to 988 and 994 cmÀ1 in the spectra of the Ni(II) and the
Zn(II) complexes, respectively. This is in agreement with the short-
ening of the S–N bond length (and increase of the bond order) rel-
ative to that of the uncoordinated ligand, shifting the m(S–N) band
to higher frequency. The S–N bond distance calculated for the li-
gand is 1.69 Å, and it shortens in the Ni(II) and Zn(II) complexes
to 1.61(13) Å and 1.60 Å respectively
The 13C NMR spectrum shows six singlet signals at 147.95 ppm,
138.94 ppm, 135.43 ppm 132.16 ppm 130.73 ppm and 123.72 ppm
assigned to the six aromatic carbon of the sulfonamide. Unfortu-
nately, the NMR spectra of the paramagnetic Ni(II) complex could
not be measured in solution and no comparison with the Zn com-
plex has been possible.
The nature of the metal–NH3 bond is confirmed by a new band
that develops at 380 cm–1 in the Raman spectrum of the complex,
which appears at 391 and 377 cmÀ1 (for Ni and Zn complexes,
respectively). The bands associated with the N–H corresponding
modes are observed at 362 and at 352 cmÀ1
.

G. Estiu et al. / Journal of Molecular Structure 1062 (2014) 82–88
87
Table 4
FTIR and Raman frequencies observed and calculated in 4-chloro-2-nitrobenzenesulfonamide of nickel and zinc complexes. Observed FTIR bands of ligand are also included.
Liganda
Infrared
Ni 4-Chloro-2-nitrobenzenesulfonamide
Zn 4-Chloro-2-nitrobenzenesulfonamide
Assignments
Infrared
3372 vs
Raman
B3LYP
Infrared
3380 sh
Raman
B3LYP (linear)
3443 (61)
B3LYP (non-linear)
3442 (27)
3370 (133)
3407 (81)
3372 vs
m
asNH3
mas NH2
asN–H3
ms NH
3368 vs
3272 vs
3355 sh
3280 vs
3235 sh
3389 (133)
3316 (6.8)
3298 (85)
3232 (565)
3105 (11)
3347 vs
3279 sh
3355 sh
3412 (70)
3376 (15)
3302 (25)
3439 (20)
3389 (25)
3249 (61)
3241(184)
3106(4)
3091(2.7)
1667 (33)
1576 129)
1536(127)
1558(167)
1349(200)
m
3299 (6.8)
m
sN–H3
3089 m
3092 m
3094 w
3077 m
3094 vw
3075 vw
1621 w
1592 m
1543 s
3105(4)
3090 (1)
m
m
C–H
C–H
3078 w
1652 (135)
1601 (341)
1546 (77)
1566 (188)
1354 (369)
1651 (17)
1575 (123)
1536(127)
1558 (164)
1355 (215)
dNH3
masNO2 + ring
1592 m
1533 s
1564 w
1365 s 1348 s
1587 m
1535 vs
1562 m
1365 vs
1585w
1542 w
1566 w
1363 w
1588w
1542 w
1562 w
1363 s
1560 w
1361 s
Ring
m
m
sC–NO2
asSO2
+
m
sNO2
NH
1282 m
1263 m
1280 sh
1286 (40)
1281 m
1271 m
1243 m
1279 (22)
1251(31)
1237 (224)
1219(220)
1219 (270)
1206 (173)
1164 (182)
1145 (39)
1130 (24)
1102 (64)
1054 (137)
883 (122)
856 (508)
818 (22)
1282 (12)
1258 (77)
1232(322)
Ring mCH + m
1255 br
1224 (50)
1242 w
q
q
NH3
+
q
NH
NH
NH3
1235 sh 1193 vs
1211 (506) 1194 (365)
1190 m
1193 vw
1215(245)
1207(130)
1170(89)
1157(174)
1134 (21)
1102 (59)
1051(251)
892 (301)
858 (31)
819 (19)
817 (19)
745(31)
678 (162)
636 (129)
NH3
+
q
1164 s
1166 s
1157 vs
1133 vs
1100 m
1056 m
988 vs
886 m
873 m
770 s
747 m
662 s
619 s
577 w
551 m
485 s
1159 m
1142 sh
1134 vs
1105 m
1058 m
994 s
887 m
875 m
773 s
1159 m
1144 m
1135 m
(
q
NH2)a
q
1150 w
1132 w
1139 (157)
1129 (167)
1103 (143)
1044 (290)
851 (713)
858 (142)
858 (142)
746 (81)
dNH + Ring
dNH + ring
Ring
1136 w
1060 w
920 m
885 m
875 m
776 m
1058 m
993 m
1058 m
998 m
m
m
sSO2
S–N
dNO2 + ring
Ring
Ring
769 m
744 w
666 w
772 s
816 (22)
738 (78)
752 m
668 w
637 m
555 m
744 (34)
660 (134)
622 (66)
606 (150)
575 (230)
476 (113)
349 (3.1)
347 (3)
q
q
x
x
q
NO2 + ring
NH + NH3
N–H ring
NH3
NH3
662 w
643 (166)
600 (392)
579 (237)
537 (55)
411 (117)
372 (11)
q
NH3
N–H +
SO2
+
x
559 w
x
560 w
450 m
564 (120)
450 (70)
340 (12)
346 (5)
+
x
+
x
N–H
480 w
391 w
362 w
481 w
m
m
m
C–Cl + ring
M–NH3 + ring
M–NH
377 w
352w
319 (6)
a
Ref. [11].
3.3. Thermogravimetric study of the complexes, TG-DT
4. Conclusions
The TG curve of the complex reveals that the decomposition
takes place in three steps. The first one corresponds to a weight
loss of 11.70% which is consistent with the evolution of the four
NH3 groups (loss of weight calculated 11.36%). This process takes
place with one endothermic peak observed in the DTA curve at
120 °C and an exothermic peak at 155 °C. The second step occurs
with a weight loss of 51.45% probably due to the evolution of the
two sulphonamide ligands with their substituents except one SO2
group (expected 51.4%). The third step shows an incomplete reac-
tion until 800 °C. This feature may be assigned to the oxidation of
the other SO2 group, loss of weight observed 9.75%, calculated
10.70%.
As for the case of the nickel complex, the Zn complex TG curve
shows three steps. The first one corresponds to a weight loss of
39.57% consistent with the evolution of the two NH3 and one of
the sulfonamide ligands (loss of weight calculated 38.89%). In the
DTA curve two endothermic peaks are observed at 187 and at
197 °C. The second step of the TG curve is compatible with a
weight loss of 25.79% and might be attributed to the decomposi-
tion of the benzene ring with their substituents except the SO2
group (calculated 23.98%). This process takes place with one endo-
thermic peak observed in the DTA curve at 234 °C. The last incom-
plete step probably corresponds to the decomposition of the
remaining SO2 group, loss of weight observed 11.26%, calculated
9.78% with an exothermic peak observed in DTA at 410 °C.
This study reports the synthesis and characterization of
Ni(L)2(NH3)4 and Zn(L)2(NH3)2 complexes with L = 4-chloro-2-
nitrobenzenesulfonamide. The Ni(II) complex was structurally
characterized by single crystal X-ray diffractometry while the
Zn(II) complex was characterized by powder X-ray method. The
structural data derived from IR and Raman spectroscopies are in
a good agreement with those determined by X-ray diffraction
methods. Electronic structure calculations have been used to ana-
lyze the structural characteristics of the Zn complex, for which the
crystal structure was not obtained, and to better assign the spec-
troscopic features. The agreement of the calculated data with the
experimental excitation energies and intensities supports the accu-
racy of the theoretical description.
Supplementary material
Tables of fractional coordinates and equivalent isotropic dis-
placement parameters of the non-H atoms (Table S4), full bond dis-
tances and angles (Table S5), atomic anisotropic displacement
parameters (Table S6), hydrogen atoms positions (Table S7), and
H-bond distances and angles (S8). A CIF file with details of the
crystal structure reported in the paper has been deposited with
the Cambridge Crystallographic Data Centre, under deposition
number CCDC 923214. Tel.: +54 221 4246062/4247201/4230122;
E-mail address: geche@fisica.unlp.edu.ar.

88
G. Estiu et al. / Journal of Molecular Structure 1062 (2014) 82–88
[15] G.M. Sheldrick. SHELXL-97. Program for Crystal Structures Analysis. Univ. of
Acknowledgments
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G.E. thanks to the Center for Research Computing at the
University of Notre Dame. M.E.Ch.V., G.A.E. and D.B.S. thanks Uni-
versidad Nacional de La Plata, CONICET (CEQUINOR and PIP0356,
PIP1529), ANPCyT (PME06 2804 and PICT06 2315), SUBCYT and
CICPBA. G.C. thanks to the University of San Luis, Argentina for
financial support. The authors would like to thank to Dr. J. Jios from
LASEISIC-PLAPIMU, UNLP, for his helpful advice and comment on
the NMR spectra interpretation.
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