Synthesis, crystal structures and characterization of three novel complexes with N-[2-(2-hydroxybenzylideneamino)ethyl]-4-methyl-benzene-sulfonamide as ligand

Article abstract of DOI:10.1016/j.ica.2008.10.002

Reaction of the N-tosyl-ethylenediamine and salicylaldehyde forms a new sulfonamide Schiff base N-[2-(2-hydroxybenzylideneamino)ethyl]-4-methyl-benzene-sulfonamide (H₂L). Three novel complexes constructed from H₂L, namely, [M(HL)

Full text of DOI:10.1016/j.ica.2008.10.002

Inorganica Chimica Acta 362 (2009) 2217–2221
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Inorganica Chimica Acta
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Synthesis, crystal structures and characterization of three novel complexes with
N-[2-(2-hydroxybenzylideneamino)ethyl]-4-methyl-benzene-sulfonamide as ligand
*
Shu-Ni Li, Quan-Guo Zhai, Man-Cheng Hu , Yu-Cheng Jiang
Key Laboratory of Macromolecular Science of Shaanxi Province, School of Chemistry and Materials Science, Shaanxi Normal University, Xi’an, Shaanxi 710062, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 2 August 2008
Received in revised form 3 October 2008
Accepted 6 October 2008
Available online 14 October 2008
Reaction of the N-tosyl-ethylenediamine and salicylaldehyde forms a new sulfonamide Schiff base N-[2-
(2-hydroxybenzylideneamino)ethyl]-4-methyl-benzene-sulfonamide (H2L). Three novel complexes con-
structed from H2L, namely, [M(HL)2] ꢀ xH2O (M = Cu, x = 0 for 1, M = Ni, x = 0 for 2 and M = Zn, x = 1 for 3)
have been prepared and characterized via X-ray single-crystal diffraction, elemental analysis, X-ray pow-
der diffraction (XRPD), FT-IR, UV–Vis, TGA and photoluminescence measurements. Complex hydrogen
bonds, C–Hꢀꢀꢀ
p
and
p
–
p
stacking interactions lead 1–3 to present 1-D, 2-D and 3-D supramolecular archi-
Keywords:
tectures, respectively.
N-Tosyl-ethylenediamine
Sulfonamide Schiff base
Supramolecular architecture
Fluorescence
Ó 2008 Elsevier B.V. All rights reserved.
1. Introduction
[2-(2-hydroxybenzylideneamino)ethyl]-4-methyl-benzene-sulfon-
amide (H2L) (Scheme 1) was prepared and three novel complexes
on the base of this ligand, namely, [M(HL)2] ꢀ xH2O (M = Cu, x = 0
for 1, M = Ni, x = 0 for 2 and M = Zn, x = 1 for 3) have also been pre-
pared and characterized by elemental analysis, X-ray single-crystal
diffraction, X-ray powder diffraction (XRPD), FT-IR, UV–Vis, TGA
and photoluminescence measurements.
Metal complexes with Schiff base ligands have played an impor-
tant role in the development of coordination chemistry due to their
preparative accessibility and structural variety [1–3]. Moreover,
they have been widely used not only in inorganic and biological
field [4–6], but also in catalytic field [7–9]. A great deal of review
[3,7,10–12] has been reported in the synthesis, characterization
and application of salen like Schiff base with transition metal com-
plexes. However, changes in the electronic, steric and geometric
properties of the ligand alter the orbitals at the metal centre and
thus affect its properties.
2. Experimental
2.1. Materials
The tetradentate salen ligand is a strong electron donor. Elec-
tron withdrawal of the sulfonyl group in the sulfonamide Schiff
base causes important changes in both the ligand and the com-
plexes. Over the past 10 years, there have been many reports on
transition metal complexes with sulfonamide Schiff base [13,14].
The research mainly focused on two types of sulfonamide Schiff
base, one is derived from the condensation of 2-tosylaminobenzal-
dehyde and diamines [15–19], and the other is the condensation of
N-tosyl-diamine and aldehydes [20–22].
As a part of our going research of project dealing with the coor-
dination chemistry of Schiff base ligands, we recently turn our
attention to the study of asymmetric sulfonamide Schiff base in
contrast to salen. In this work, a new sulfonamide Schiff base N-
All solvents, Cu(CH3COO)2 ꢀ H2O, NiCl2 ꢀ 6H2O and Zn plate were
commercial products and used without further purification. N-To-
syl-ethylenediamine was synthesized according to the literature
method [23].
2.2. Analyses and physical measurements
C, H and N elemental analysis was performed on a Vario EL-III
analyzer. Infrared spectra were recorded as KBr pellet on a Nicolet
Avatar 360 spectrophotometer in the range 4000–400 cmꢁ1. UV–
Vis absorptions were recorded on a SHIMADZU UV-1700 spectro-
photometer. Luminescence emission and excitation spectra were
recorded with a Perkin–Elmer LS55 luminescence spectrometer
at room temperature. Thermogravimetric analysis was performed
on Q1000 DSC with a heating rate of 10 °C minꢁ1 under N2
atmosphere.
* Corresponding author. Tel.: +86 29 85307765; fax: +86 29 85307774.
E-mail address: hmch@snnu.edu.cn (M.-C. Hu).
0020-1693/$ - see front matter Ó 2008 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2008.10.002

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S.-N. Li et al. / Inorganica Chimica Acta 362 (2009) 2217–2221
2.3.3. [Ni(HL)2] (2)
O
S
To an ethanol solution (25 mL) of H2L (0.318 g, 1 mmol),
H
C
N
HN
CH
3
NiCl2 ꢀ 6H2O (0.238 g, 1 mmol) was added as solid slowly. Large
amount brown-green precipitation was produced and then filtered.
It was collected and washed with ethanol, then redissolved in DMF.
Brown-green column crystals were obtained from the filtrate after
a week. Anal. Calc. for C32H34N4O6S2Ni: C, 55.42; H, 4.940; N, 8.080.
Found: C, 55.66; H, 4.835; N, 8.118%.
O
OH
Scheme 1. H2L.
2.3. Synthesis
2.3.4. [Zn(HL)2] ꢀ H2O (3)
To a methanol solution (30 mL) of H2L (0.16 g, 0.5 mmol), 10 mg
of tetraethylammonium perchlorate was added as supporting elec-
trolyte. The solution was electrolyzed using a platinum wire as the
cathode and Zn plate as the sacrificial anode according to the liter-
ature method [13,14,18]. The light yellow precipitation was col-
lected and washed with hot ethanol. It was redissolved in DMF.
Yellow block crystals were obtained from the filtrate after two
weeks. Anal. Calc. for C32H36N4O7S2Zn: C, 37.35; H, 6.730; N,
14.53. Found: C, 37.53; H, 6.640; N, 14.17%.
2.3.1. N-[2-(2-Hydroxybenzylideneamino)ethyl]-4-methyl-benzene-
sulfonamide (H2L)
The Schiff base ligand H2L was obtained by refluxing the etha-
nol solution (60 mL) of N-tosyl-ethylenediamine (2.14 g,
0.01 mol) and salicylaldehyde (1.22 g, 0.01 mol). Yellow needle
crystals were collected from the solution. M.p. 123.6–124.4 °C.
Anal. Calc. for C16H18N2O3S: C, 60.38; H, 5.660; N, 8.805. Found:
C, 60.52; H, 5.487; N, 8.595%.
2.3.2. [Cu(HL)2] (1)
2.4. Single-crystal X-ray diffraction studies
To a THF solution (20 mL) of H2L (0.318 g, 1 mmol), Cu(CH3-
COO)2 ꢀ H2O (0.20 g, 1 mmol) was added slowly. The mixture was
stirred for 2 h and the resulting green powder was filtrated and
redissolved in DMF. Brown column crystals were obtained after
one month. Anal. Calc. for C32H34N4O6S2Cu: C, 55.01; H, 4.871; N,
9.169. Found: C, 55.43; H, 4.717; N, 9.306%.
The crystal determination was performed at room temperature
on a Brucker-Smart APEX CCD diffractometer, using graphite
0
monochromated Mo Ka radiation (k = 0.71073 ÅA). Absorption cor-
rections were made using the SADABS program [24]. The structures
were solved by direct methods and refined by full-matrix least
squares based on F2, using SHELX-97 software [25]. All non-hydrogen
atoms were anisotropically refined. Hydrogen atoms were included
at geometrically calculated positions and refined using a riding
model except those bonded to the water molecule. The crystal
data, experimental details, refinement results and details of struc-
ture determinations are shown in Table 1. Selected bond lengths
and bond angles are listed in Table S1.
Table 1
Crystal data and structure refinements for complexes 1–3.
Identification code
1
2
3
Empirical formula
Formula weight
Temperature (K)
Wavelength (Å)
Crystal system
Space group
Unit cell dimensions
a (Å)
C32H34N4O6S2Cu
698.29
296(2)
C32H34N4O6S2Ni
693.46
296(2)
0.71073
monoclinic
P2(1)/c
C32H35N4O7S2Zn
717.13
296(2)
0.71073
orthorhombic
Pbcn
0.71073
triclinic
3. Results and discussion
ꢀ
P1
3.1. Crystal structures of [Cu(HL)2] (1) and [Ni(HL)2] (2)
7.6332(8)
10.1629(11)
10.5240(11)
94.172(2)
102.5190(10)
99.504(2)
781.04(14)
1
16.832(4)
5.2417(13)
19.415(5)
90
111.717(4)
90
1591.4(7)
2
1.447
11.1950(18)
9.9744(16)
29.520(5)
90
90
90
3296.3(9)
9
1.445
b (Å)
c (Å)
The molecular structure of complexes 1 and 2 is presented in
Fig. 1. The Cu(II) and Ni(II) ions are tetra-coordinated by the imine
nitrogen atoms and phenolate oxygen atoms of two bidentate an-
ionic Schiff base ligands. The M–Nimine distance is much longer
than M–Ophenolate distance in both complexes. The coordination
a
(ꢁ)
b (ꢁ)
c
(ꢁ)
V (Å3)
Z
Dcalc. (Mg/m3)
Absorption
coefficient
1.485
0.884
0.791
0.925
(mmꢁ1
)
F(000)
363
724
1492
Crystal size (mm)
h Range for data
collection (°)
0.37 ꢂ 0.25 ꢂ 0.20 0.38 ꢂ 0.28 ꢂ 0.14 0.42 ꢂ 0.36 ꢂ 0.20
1.99–25.10
2.15–25.09
2.28–25.10
Limiting indices
ꢁ9 6 h 6 8
ꢁ9 6 k 6 12
ꢁ12 6 l 6 9
3969
ꢁ20 6 h 6 20
ꢁ5 6 k 6 6
ꢁ23 6 l 6 21
7418
ꢁ13 6 h 6 9
ꢁ11 6 k 6 11
ꢁ32 6 l 6 35
15287
Reflections
collected
Independent
reflections (Rint
Maximum and
minimum
2718 (0.0380)
2814 (0.0385)
2933 (0.0325)
)
0.8773 and
0.7657
0.8959 and
0.7536
0.8388 and
0.6997
transmission
Data/restraints/
parameters
2718/0/205
1.002
2814/0/194
1.003
2933/1/184
1.034
Goodness-of-fit on
F2
R1, wR2 [I > 2d(I)]
R1, wR2 (all data)
0.0476, 0.1143
0.0731, 0.1263
0.345/ꢁ0.439
0.0415, 0.1166
0.0542, 0.1273
0.448/ꢁ0.613
0.0364, 0.1139
0.0475, 0.1209
0.433/ꢁ0.373
q
fin(max/min)
Fig. 1. Molecular structure of complexes 1 and 2 (H atoms omitted for clarity)
(M = Cu(II) and Ni(II) for 1 and 2).
(e Åꢁ3
)

S.-N. Li et al. / Inorganica Chimica Acta 362 (2009) 2217–2221
2219
Fig. 2. 1-D chain structure of complex 1 (a) and 2-D layer structure of complex 2 (b).
geometry around Cu(II) and Ni(II) ion is a slightly distorted square
3.2. Crystal structure of [Zn(HL)2] ꢀ H2O (3)
planar with the cis angles of 92.15(13)° and 87.85(13)° for 1, and
87.0(10)° and 93.0(10)° for 2, respectively. Each ligand forms one
M–O1–C2–C1–C7–N1 six-membered chelate ring (deviation 0.08
and 0.03 Å for 1 and 2), and the metal lies deviating from this cal-
culated plane with +0.13 and ꢁ0.05 Å for 1 and 2, respectively. The
deviation value of 2 is much small than that of 1, which may be ex-
plained as the larger crystal field stabilization energy (CFSE) of d8
Complex 3 consists of a neutral coordination unit Zn(HL)2 and a
solvated water molecule (Fig. 3a). The coordination sphere around
Zn(II) is completed by the imine nitrogen and deprotonated phenol
oxygen of two anionic Schiff base ligands. Zn(II) is in a [ZnN2O2] dis-
torted tetrahedron with the dihedral angle between both N–Zn–O
plane of 73.2°. The Zn2+ is about ꢁ0.29 Å below the calculated plane
of Zn1O1O1AN1N1A (deviation +0.79 Å). The bond angles are in the
range 94.91(8)–123.89(13)° deviating from the ideal values. The Zn–
Ophenolate distance is shorter than Zn–Nimine distance.
configuration of Ni2+
Although complexes 1 and 2 have almost the same coordination
geometry, the different electron configuration of Cu2+ and Ni2+
.
,
leads to the much different crystal packing of two complexes. Com-
plex 1 is extended into the final 1-D chain supramolecular struc-
When viewed from bc plane (Fig. S2), weak intermolecular C3–
H3ꢀꢀꢀOtosyl hydrogen bonds (CꢀꢀꢀO 3.428(3) Å) link the molecules
ture as shown in Fig. 2a, through weak aromatic
p–p
stacking
into a 1-D chain. Then, two weak C16–H16ꢀꢀꢀ interactions (Cꢀꢀꢀcen-
p
interactions between phenyl rings from adjacent organic ligands,
with a centre-to-centre distance of about 4.0 Å. In the structure
of complex 2, intermolecular Namide–HꢀꢀꢀOtosyl hydrogen bond
(NꢀꢀꢀO 2.9345(3) Å) links the molecules into a 1-D chain along the
troid 3.989(5) Å), one as donor and one as acceptor, link the 1-D
chains into a 2-D layer. And the 1-D chains in the layer are packed
in the ABAB alternated mode. Then, the solvated water molecules
lies in the net by O4–H4BꢀꢀꢀOtosyl hydrogen bonds (OꢀꢀꢀO
3.039(6) Å) (Fig. S2). Further, when viewed from ab plane
(Fig. S3), each [Zn(HL)2] molecule forms four Namide–HꢀꢀꢀOphenolate
intermolecular hydrogen bonds (NꢀꢀꢀO 2.822(3) Å), forming a 2-D
c-axis direction (Fig. S1). Then, two weak C6–H6ꢀꢀꢀ
p interactions
(Cꢀꢀꢀcentroid 3.60 Å), link the chains into a 2-D layer structure on
ac plane (Fig. 2b).

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S.-N. Li et al. / Inorganica Chimica Acta 362 (2009) 2217–2221
of the solvated water molecule and the band at 3066 cmꢁ1 indi-
cates the uncoordination mode of the amide N–H. And complexes
1–3 show a negative shift of the N–H band relative to the free li-
gand. This may be caused by the formation of N–HꢀꢀꢀO hydrogen
bonds. Moreover, the bands at about 1617 cmꢁ1 for 1 and 2, and
1610 cmꢁ1 for 3 are attributed to
m(C@N), showing a lower fre-
quency shift of 15 and 22 cmꢁ1 compared with the free ligand at
1632 cmꢁ1. This suggests the coordination of the ligand to the met-
als through the imine nitrogen atoms. In addition, two bands at
about 1151 and 1320 cmꢁ1 are attributable to the asymmetric
and symmetric vibration modes of SO2 group, respectively [26].
3.4. UV–Vis absorption and fluorescence studies
The UV–Vis absorption spectra of the ligand in ethanol, complex
1, 2 and 3 in DMF were given in Fig. 4. The absorption band at
359 nm for free ligand shift to 364, 405 and 365 nm in complexes
1, 2 and 3, respectively. The red shift indicates the coordination of
C@N to the metal. The band at 321 nm for ligand still appears in
complex 2 but disappear in complexes 1 and 3. These bands in
the UV wavelength region can be assigned to the intraligand
p
?
p* transition of C@N group. Moreover, there exist weak d–d
transition at about 599 nm for complex 1, and about 653 and
767 nm for complex 2. However, complex 3 has no bands in the
visible range because of the d10 configuration of Zn2+
.
Solid state fluorescence spectra show that the ligand and the
complexes have the similar excitation at 212 nm and emission at
361 nm at room temperature (Fig. S7). The only difference is that
the chelation of the metal ion to HLꢁ decrease the fluorescence
intensity of the complexes comparing with the ligand.
The solution fluorescence properties of the ligand and its com-
plexes 1, 2 were studied at room temperature in DMF solutions
(10ꢁ4 mol Lꢁ1
) (Fig. 5). The emission spectra of the ligand
(k = 443 nm) and complex 3 (k = 451 nm) are similar, but the exci-
tation of complex 3 (k = 309 nm) is strong red-shifted compared to
the ligand (k = 249 nm). This may be explained that the electron
density of C@N group is decreased when the metal coordinating
to the ligand. It also can be seen that the emission intensity of com-
plex 3 is much stronger than that of the ligand. This is in general
called as chelation enhanced fluorescence intensity. However,
complex 2 shows a fluorescence quenching in solution. For fluores-
cence character of the complexes in the solid and the solution, no
emission can be assigned to the MLCT or LMCT transition. Thus, the
emission of the complexes and the ligand can be assigned to intral-
Fig. 3. (a) Molecular structure of complex 3 (solvated water and H atoms omitted
for clarity). (b) 3-D supramolecular structure of complex 3.
igand
p
?
p* fluorescence [27,28].
hydrogen bonded (4,4) network. Moreover, each [Zn(HL)2] mole-
cule also generates four C7–H7ꢀꢀꢀ
p
interactions (Cꢀꢀꢀcentroid
3.863(3) Å), which help to stabilize the 2-D network along the ab
plane (Fig. S4). Finally, all the complex weak interactions link the
molecules of 3 into a 3-D supramolecular network (Fig. 3b).
3.3. XRPD and FT-IR spectra
As shown in Fig. S5, complexes 1–3 were characterized via X-
ray powder diffraction (XRPD) at room temperature. The XRPD pat-
tern measured for the complexes are in good agreement with the
results simulated from the single-crystal X-ray data using MERCURY
1.4.2 program, indicating that the compounds were isolated as a
single phase.
In the IR spectrum of free ligand H2L, the
at 3439 and 3225 cmꢁ1 (Fig. S6). But complexes 1 and 2 show the
absence of the (O–H) and the presence of the (N–H), indicating
m(O–H) and m(N–H) are
m
m
only the deprotonation of O–H group in the coordination com-
plexes. For complex 3, the band at 3426 cmꢁ1 shows the presence
Fig. 4. UV–Vis spectra of H2L and complexes 1–3.

S.-N. Li et al. / Inorganica Chimica Acta 362 (2009) 2217–2221
2221
Appendix A. Supplementary material
CCDC 694915, 694916 and 694917 contain the supplementary
crystallographic data for 1, 2 and 3. These data can be obtained free
of charge from The Cambridge Crystallographic Data Centre via
http://www.ccdc.cam.ac.uk/data_request/cif. Supplementary data
associated with this article can be found, in the online version, at
doi:10.1016/j.ica.2008.10.002.
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In this paper, we have reported the synthesis, crystal structure
and characterization of three novel metal–organic coordination
complexes with sulfonamide Schiff base ligands. The potentially
tridentate Schiff base acts as bidentate ligand in the three com-
plexes because of the presence of the tosyl group. The hydrogen
bonds, weak C–Hꢀꢀꢀ
p
and
p p interactions in the crystals link the
ꢀꢀꢀ
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, Program for Area Detector Adsorption Correction,
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of Göttingen, Germany, 1997.
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structures.
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We thank the National Natural Science Foundation of China
(Nos. 20801033 and 20871079).