Synthesis, structure and coordination properties of three cyclam-based ligands bearing one scorpionate arm

Article abstract of DOI:10.1016/j.ica.2011.04.013

In this work, three new cyclam-based ligands L₁, L₂ and L₃ bearing N-sulfonylacetamide pendant arm and their Cu(II), Zn(II), Cd(II) and Pb(II) complexes were synthesized and characterized by mass spectrometry, NMR, infrared and UV-Vis spectroscopies. The ligands present an original zwitterionic form in which the nitrogen atom of the sulfonylacetamide is deprotonated and one nitrogen of the macrocycle is protonated. This observation was confirmed by X-ray crystallography. The infrared spectra of the ligands revealed very low CO vibrational band values which can be explained by the fact that the oxygen atom is involved in some hydrogen bonds. The amidate form of the sulfonylacetamide arm is maintained upon complexation. Infrared data revealed a probable different coordination mode for Pb(II) than for the other three cations. Some additional studies by UV-Vis and EPR spectroscopies were performed for the Cu(II) complexes. Finally, the geometry coordination of the Cu(II) L₃, Zn(II) L₃ and Cd(II) L₃ complexes in the solid state was studied by X-ray crystallography.

Full text of DOI:10.1016/j.ica.2011.04.013

Inorganica Chimica Acta 373 (2011) 150–158
Contents lists available at ScienceDirect
Inorganica Chimica Acta
journal homepage: www.elsevier.com/locate/ica
Synthesis, structure and coordination properties of three cyclam-based ligands
bearing one scorpionate arm
Ramu Kannappan a, Yoann Rousselin a, Rim Zaari Jabri a,b, Christine Goze a, Stéphane Brandès a,
Roger Guilard a, Abdellah Zrineh b, Franck Denat a,
⇑
a ICMUB, UMR 5260, CNRS-Univ. de Bourgogne, 9 avenue Alain Savary, 21078 Dijon Cedex, France
b Laboratoire de Physique Générale, Université Mohamed V Agdal, Faculté des Sciences, 4 avenue Ibn Battouta, B.P. 1014 RP, Rabat, Morocco
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 8 April 2010
Received in revised form 24 March 2011
Accepted 6 April 2011
Available online 19 April 2011
In this work, three new cyclam-based ligands L1, L2 and L3 bearing N-sulfonylacetamide pendant arm and
their Cu(II), Zn(II), Cd(II) and Pb(II) complexes were synthesized and characterized by mass spectrometry,
NMR, infrared and UV–Vis spectroscopies. The ligands present an original zwitterionic form in which the
nitrogen atom of the sulfonylacetamide is deprotonated and one nitrogen of the macrocycle is proton-
ated. This observation was confirmed by X-ray crystallography. The infrared spectra of the ligands
revealed very low CO vibrational band values which can be explained by the fact that the oxygen atom
is involved in some hydrogen bonds. The amidate form of the sulfonylacetamide arm is maintained upon
complexation. Infrared data revealed a probable different coordination mode for Pb(II) than for the other
three cations. Some additional studies by UV–Vis and EPR spectroscopies were performed for the Cu(II)
complexes. Finally, the geometry coordination of the Cu(II) L3, Zn(II) L3 and Cd(II) L3 complexes in the
solid state was studied by X-ray crystallography.
Keywords:
Cyclam
N-Sulfonylacetamide
X-ray studies
Metal complexes
EPR
Ó 2011 Elsevier B.V. All rights reserved.
1. Introduction
Here, we report the synthesis of three new ligands bearing N-
sulfonylacetamide pendant arm and their metal complexes. The
1,4,8,11-Tetraazacyclotetradecane (cyclam) is one of the most
extensively studied macrocyclic ligands. This macrocycle can coor-
dinate various metal ions with large stability constants [1]. Cyclam
and its derivatives have also been studied as carriers of metal ions
for imaging applications [2,3] and, most recently, as anti-HIV
agents [4].
In most of the cyclam complexes the metal is coordinated in a
square stereochemical arrangement, in which the four nitrogen
atoms of the ring are coplanar with the metal center. In this situa-
tion, the complex is highly resistant to demetallation due to the so
called macrocyclic effect [5].
The affinity of the macrocycle towards a specific guest, a metal-
lic cation in most cases, might be tuned by varying the nature, the
number, and the relative positions of the pendant arms on the
nitrogen atoms [6]. The addition of a coordinating pendant arm
such as an amide or acid arm results in a fifth binding site that
can create a square pyramidal coordination polyhedron.
It should be noted that the interaction of the metal ion with the
nitrogen atom bound axially is quite labile and the pendant group
can be removed from the coordination sphere on pH change [7].
This type of ligand is called scorpionate. These systems can be
symbolized by a rigid ring (the tetraazamacrocycle) and a flexible
part (the arm).
N-sulfonylacetamide moiety, possessing a negative charge at
physiologic pH, represents an isosteric alternative to the carboxylic
acid group. This offers the possibility to modulate several proper-
ties of the resulting complexes (charge, size, hydrophilicity). In this
work, we considered three cyclam based macrocyclic ligands,
which form a zwitterion upon addition of the N-sulfonylacetamide
arm (Fig. 1). The crystal structures highlighting such a zwiterrionic
form of a sulfonamide function are reported. It has to be noted that
the zwitterionic form resulting from addition of the arm to the
non-substituted macrocycle L1 is different than the ones obtained
when starting from trans disubstituted cyclams L2 and L3.
We studied the coordination properties of these new cyclam
based ligands toward Cu(II), Cd(II), Zn(II) and Pb(II). The geometry
of the complexes was studied by X-ray crystallography and by EPR
spectroscopy. We put forward evidence that the zwitterionic form
is maintained in the metal complexes.
2. Experimental
2.1. Materials and physical measurements
The chemicals used to prepare the title compounds including
CuCl2ꢀ2H2O, Zn(NO3)2ꢀ6H2O, Cd(NO3)ꢀ4H2O, Pb(NO3)2 were pur-
chased from Aldrich. Cyclam, trans-dimethylcyclam and trans-di
benzylcyclam were obtained from CheMatechÒ and used without
⇑
Corresponding author. Tel.: +33 (0)38 039 6115; fax: +33 (0)38 039 6117.
E-mail address: Franck.Denat@u-bourgogne.fr (F. Denat).
0020-1693/$ - see front matter Ó 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2011.04.013

R. Kannappan et al. / Inorganica Chimica Acta 373 (2011) 150–158
151
to precipitate the unreacted trans-dimethylcyclam, and this opera-
tion was repeated 3–4 times until no more precipitate appeared.
Recrystallization in hot methanol gave pure L2 (3.3 g, 85% yield).
MALDI-TOF MS: m/z = 439.94 [M+H]+. 1H NMR (CDCl3, 300 MHz):
7.88 (d, 2H, J = 8.3 Hz), 7.17 (d, 2H, J = 8.3 Hz), 3.45 (bs, 2H),
2.75–2.39 (m, 16H), 2.32 (s, 3H), 2.29 (s, 3H), 2.25 (s, 3H), 1.73
(m, 3H), 1.52 (m, 2H). 13C {1H} NMR (CDCl3, 75 MHz): 176.1,
139.3, 139.1, 128.5, 127.6, 126.7, 125.3, 61.3, 55.6, 53.5, 52.8,
51.4, 48.8, 46.8, 41.3, 22.2, 19.5. IR (ATR): m
(C@O): 1596 cmꢁ1. Anal.
Fig. 1. Cyclam derivatives containing N-sulfonylacetamide arm.
Calc. for C21H37N5O3Sꢀ0.5CH3OH (455.64): C, 56.68; H, 8.63; N,
15.37. Found: C, 57.10; H, 9.42; N, 15.20%.
further purification. 2-Bromo-N-tosylethanamide was prepared
and purified according to the literature procedures [8]. The 1H
and 13C spectra were recorded at room temperature. NMR spectra
2.2.3. 20-(4,11-Dibenzyl-1,4,8,11-tetraazacyclotetradecan-1-
yl)acetyl(tosyl)amide (L3)
were run on
a BRUKER Avance 300 spectrometer at room
To a solution of trans-dibenzylcyclam (3.04 g, 8 mmol), and
anhydrous potassium carbonate (2.07 g, 15 mmol) in CH3CN
(600 mL) was slowly added a solution of 2-bromo-N-tosylaceta-
mide (2.32 g, 8 mmol) in acetonitrile (10 mL). The mixture was
stirred for 24 h under argon. The crude product was filtered
through Celite to remove K2CO3, and acetonitrile was evaporated.
The white crude powder was dissolved in chloroform and cooled
to 0 °C in order to precipitate the unreacted trans-dibenzylcyclam,
and this operation was repeated 3–4 times until no more precipi-
tate appeared. Recrystallization in hot methanol gave pure L3
(3.55 g, 75% yield). MALDI-TOF MS: m/z = 592 [M+H]+. 1H NMR
(CDCl3, 300 MHz): 7.86 (d, 2H, J = 8.5 Hz); 7.31–7.25 (m, 10H);
7.14 (d, 2H, J = 8.5 Hz); 3.76 (bs, 4H); 2.91 (s, 2H); 2.89–2.36 (m,
17H); 2.31 (s, 3H); 2.15 (m, 4H); 1.71 (m, 4H). 13C {1H} NMR (CDCl3,
75 MHz): 176.8, 141.2, 140.9, 136.8, 136.6, 129.7, 129.5, 128.6,
128.4, 127.9, 127.6, 63.2, 60.4, 59.1, 55.9, 54.9, 52.4, 51.3, 50.8,
temperature using perdeuterated solvents as internal standard.
Elemental analyses were obtained on EA 1108 CHNS Fisons Instru-
ment. Absorption spectra were recorded on a VARIAN CARY 50.
Infrared spectra were recorded using a Bruker Vector 22 spectrom-
eter (4000–500 cmꢁ1). Matrix-assisted laser desorption ionization
time-of-flight mass spectrometry (MALDI-TOF) was carried out
using a Bruker Daltonics Proflex III spectrometer. Continuous wave
(CW) EPR spectra were recorded on a Bruker ELEXSYS 500. The
instrument was equipped with a 4122 SHQE/0405 X-band reso-
nant cavity operating at 9.43 GHz, a X-band high power dual
gun-oscillator bridge, and a quartz cryostat cooled with a stream
of nitrogen. Sample were analyzed at 100 K in a frozen EtOH (or
MeOH)/toluene mixture. The temperature was regulated with an
ER 4131VT accessory. All the equipments as well as the data acqui-
sition were controlled with the Xepr software. Spectra were re-
corded at 6 mW power, 100 kHz modulation, 5 G modulation
amplitude and 40 ms conversion time. All the spectrometers were
available at the ‘‘Plateforme d’Analyse Chimique et de Synthèse
Moléculaire de l’Université de Bourgogne’’ (PACSMUB).
48.4, 48.3, 46.1, 23.5, 22.9, 21.4. IR (ATR): m
(C@O): 1542 cmꢁ1. Anal.
Calc. for C33H45N5O3Sꢀ0.5CH3OH (607.83): C, 66.20; H, 7.79; N,
11.52. Found: C, 66.20; H, 8.64; N, 11.73%.
2.3. Synthesis of the complexes
2.2. Synthesis of the ligands
2.3.1. General procedure
2.2.1. [2’-(1,4,8,11-Tetraazacyclotetradecan-1-yl)acetyl](tosyl)amide
(L1)
To a solution of cyclam (10 g, 0.05 mol) and anhydrous potas-
sium carbonate (1.38 g, 0.01 mol) in CHCl3 (600 mL) was slowly
A solution of 1 equiv of the metal salt in methanol was added
dropwise to a solution of ligand in methanol and the resulting mix-
ture was refluxed for 5 h. After cooling, diethylether was added and
the precipitate was filtrated.
added
a
solution of 2-bromo-N-tosylacetamide (1.45 g,
0.005 mol) in 10 mL of chloroform. The mixture was stirred for
24 h. The crude product was filtered through Celite to remove
K2CO3, and chloroform was evaporated. The white crude powder
was dissolved in CH3CN and cooled to 0 °C in order to precipitate
the unreacted cyclam, and this operation was repeated 3–4 times
until no more precipitate appeared. Recrystallization in MeOH gave
pure L1 (1.03 g, 50% yield). 1H NMR (CDCl3, 300 MHz): 7.85 (d, 2H,
J = 8.2 Hz), 7.16 (d, 2H, J = 8.2 Hz), 5.48 (bs, 3H), 3.05 (s, 2H), 3.00–
2.53 (m, 17H), 2.34 (s, 3H), 1.81 (m, 2H), 1.67 (m, 2H). 13C {1H}
NMR (CDCl3, 75.4 MHz): 177.9, 141.5, 141.2, 130.1, 128.7, 127.2,
126.9, 60.4, 54.7, 54.0, 49.8, 48.1, 47.0, 44.2, 26.5, 24.3, and 21.5.
2.3.1.1. CuL1Cl. According to the general procedure starting from
41.4 mg (0.243 mmol) of CuCl2ꢀ2H2O in 10 mL of MeOH and
100 mg (0.243 mmol) of L1 in 20 mL of MeOH. Yield: 97 mg
(0.19 mmol, 79%). MALDI-TOF MS: m/z = 473 [MꢁCl]+. IR (ATR):
m
(C@O): 1634 cmꢁ1. UV–Vis (CHCl3) k nm ( , Mꢁ1 cmꢁ1) = 620
e
(125). Anal. Calc. for
44.56; H, 6.52; N,13.33. Found: C, 44.29; H, 6.79; N, 13.41%.
C
19H32ClCuN5O3Sꢀ0.5CH3OH (525.57): C,
2.3.1.2. CuL2Cl. According to the general procedure starting from
42.25 mg (0.248 mmol) of CuCl2ꢀ2H2O in10 mL of MeOH and
102 mg (0.248 mmol) of L2 in 20 mL of MeOH. Yield: 109 mg
(0.20 mmol, 82%). MALDI-TOF MS: m/z = 502.81 [MACl+H]+ UV–
MALDI-TOF MS: m/z = 412.35 [M+]. IR (ATR): (C@O): 1596 cmꢁ1
m .
Anal. Calc. for C19H33N5O3Sꢀ2MeOH: C, 53.03; H, 8.69; N, 14.72.
Vis (CHCl3) k nm (e m(C@O):
, Mꢁ1 cmꢁ1) = 646 (128). IR (ATR):
Found: C, 52.75; H, 8.72; N, 14.30%.
1633 cmꢁ1. Anal. Calc. for C21H36ClCuN5O3Sꢀ2H2O (573.64): C,
2.2.2. [20-(4,11-Dimethyl-1,4,8,11-tetraazacyclotetradecan-
1yl]acetyl)(tosyl)amide (L2)
43.97; H, 7.03; N, 12.21. Found: C, 43.82; H, 7.11; N, 12.33%.
To a solution of trans-dimethylcyclam (2 g, 8.75 mmol), and
anhydrous potassium carbonate (2.4 g, 17.5 mmol) in CH3CN
(300 mL) was slowly added a solution of 2-bromo-N-tosylaceta-
mide (2.56 g, 8.75 mmol) in 10 mL of CHCl3. The mixture was stir-
red for 24 h. The crude product was filtered through Celite to
remove K2CO3, and acetonitrile was evaporated. The white crude
powder was dissolved in chloroform and cooled to 0 °C in order
2.3.1.3. CuL3Cl. According to the general procedure starting from
144 mg (0.845 mmol) of CuCl2ꢀ2H2O in 20 mL of MeOH and
500 mg (0.845 mmol) of L3 in 30 mL of MeOH. After precipitation,
blue crystals of pure complex were obtained after recrystallization
in CH3OH/H2O (394 mg, 67% yield). MALDI-TOF MS: m/z = 654.81
[MꢁCl]+ UV–Vis (CHCl3) k nm (
e
, Mꢁ1 cmꢁ1) = 623 (144). IR
(ATR):
m
(C@O): 1578 cmꢁ1
.
Anal. Calc. for C33H44ClCu-

152
R. Kannappan et al. / Inorganica Chimica Acta 373 (2011) 150–158
N5O3Sꢀ2H2Oꢀ1.5CH3OH (773.89): C, 53.54; H, 7.03; N, 9.05. Found:
2.3.1.11. PbL2NO3. According to the general procedure starting
from 75.51 mg (0.228 mmol) of Pb(NO3)2 dissolved in 20 mL of
H2O and 100 mg (0.228 mmol) of L2 in 20 mL of H2O. After filtra-
tion, the product was further washed with a mixture of metha-
nol/water. Yield: 10 mg (0.14 mmol, 60%). MALDI-TOF MS:
C, 53.40; H, 7.04; N, 9.37%.
2.3.1.4. ZnL1NO3. According to the general procedure starting from
74.52 mg (0.243 mmol) of Zn(NO3)2ꢀ6H2O in 15 mL of MeOH and
100 mg (0.243 mmol) of L1 in 20 mL of MeOH. After filtration, the
solid was further washed with dichloromethane. Yield: 99 mg
(0.185 mmol, 76%). MALDI-TOF MS: m/z = 474 [MꢁNO3]+. IR
m/z = 646 [MꢁNO3]+. IR (ATR):
m
(C@O): 1596 cmꢁ1. Anal. Calc. for
C
21H36N6O6PbSꢀ2H2O (743.84): C, 33.91; H, 5.42; N, 11.30. Found:
C, 33.82; H, 5.51; N, 11.33%.
(ATR):
m
(C@O): 1650 cmꢁ1. Anal. Calc. for C19H32N6O6SZnꢀ2H2O:
2.3.1.12. PbL3NO3. According to the general procedure starting
from 280 mg (0.845 mmol) of Pb(NO3)2 dissolved in 30 mL of
H2O and 500 mg (0.845 mmol) of L3 in 70 mL of H2O. After filtra-
tion, the product was further washed with a mixture of metha-
nol/water. Yield: 421 mg (0.59 mmol, 58%). MALDI-TOF MS:
C, 39.76; H, 6.32; N, 14.64. Found: C, 39.65; H, 6.45; N, 14.70%.
2.3.1.5. ZnL2NO3. According to the general procedure starting from
67.72 mg (0.228 mmol) of Zn(NO3)2ꢀ6H2O in 15 mL of MeOH and
100 mg (0.228 mmol) of L2 in 20 mL of MeOH. After filtration, fur-
ther recrystallization in hot CH3OH gave pure complex (102 mg,
79% yield). MALDI-TOF MS: m/z = 504.67 [MꢁNO3]+. IR (ATR):
m/z = 798.87 [MꢁNO3]+. IR (ATR):
m
(C@O): 1542 cmꢁ1. Anal. Calc.
for C33H44N6O6PbSꢀH2O (878.02): C, 45.14; H, 5.28; N, 9.57. Found:
C, 45.08; H, 5.32; N, 9.60%.
m
(C@O): 1618 cmꢁ1. Anal. Calc. for C21H36N6O6SZn: C, 44.56; H,
6.41; N, 14.85. Found: C, 44.49; H, 6.50; N, 14.88%.
2.4. X-ray crystallography
2.3.1.6. ZnL3NO3. According to the general procedure starting from
251 mg (0.845 mmol) of Zn(NO3)2ꢀ6H2O in 20 mL of MeOH and
500 mg (0.845 mmol) of L3 in 30 mL of MeOH. The solution was re-
fluxed during 5 h, then the crystals were obtained after evapora-
tion of the solvent. After filtration, further recrystallization in hot
CH3OH gave pure complex. Yield: 491 mg (0.201 mmol, 81% yield).
Experimental details of the X-ray analyses are provided in
Table 1 for ligand L1 and L3 and Table 2 for the L3 complexes.
Diffraction data were collected on a Nonius Kappa CCD or Nonius
Kappa Apex II diffractometer equipped with a nitrogen jet stream
low-temperature system (Oxford Cryosystems). The X-ray source
was graphite-monochromated Mo K
a radiation (k = 0.71073 Å)
MALDI-TOF MS: m/z = 654.10 [MꢁNO3]+. IR (ATR):
m(C@O):
from a sealed tube. In both cases, lattice parameters were obtained
by least-squares fit to the optimized setting angles of the entire set
of collected reflections. No temperature drift was observed during
the data collections. Data were reduced by using DENZO software
[9] without applying absorption corrections; the missing absorp-
tion corrections were partially compensated by the data scaling
procedure. The structures were solved by direct methods using
the SIR92 [10] program. Refinements were carried out by full-ma-
trix least-squares on F2 using the SHELXL97 [11] program and the
complete set of reflections. Anisotropic thermal parameters were
used for non-hydrogen atoms. All H atoms, on carbon atom, were
placed at calculated positions using a riding model with C–
H = 0.95 Å (aromatic), 0.98 Å (methyl), 0.99 Å (methylene) or 1 Å
(methine) with Uiso(H) = 1.5 Ueq(CH3), Uiso(H) = 1.2 Ueq(CH2) or
Uiso(H) = 1.2 Ueq(CH). H atoms on nitrogen atoms were located in
1562 cmꢁ1. Anal. Calc. for C33H44N6O6SZnꢀ0.5CH3OH: C, 54.80; H,
6.31; N, 11.45. Found: C, 55.01; H, 6.91; N, 11.69%.
2.3.1.7. CdL1NO3. According to the general procedure starting from
75 mg (0.243 mmol) of Cd(NO3)2ꢀ4H2O in 15 mL of MeOH and
100 mg (0.243 mmol) of L1 in 20 mL of MeOH. After filtration, the
complex was further recrystallized in hot CH3OH. Yield: 97 mg
(0.165 mmol, 68%). MALDI-TOF MS: m/z = 521.1 [MꢁNO3]+. IR
(ATR):
m
(C@O): 1619 cmꢁ1. Anal. Calc. for C19H32CdN6O6Sꢀ0.5-
CH3OH: C, 39.01; H, 5.51; N, 14.37. Found: C, 38.95; H, 5.58; N,
14.42%.
2.3.1.8. CdL2NO3. According to the general procedure starting from
177 mg (0.569 mmol) of Cd(NO3)2ꢀ4H2O in 20 mL of MeOH and
250 mg (0.569 mmol) of L2 in 25 mL of MeOH. After filtration, the
complex was further recrystallized in hot CH3OH. Yield: 227 mg
(0.37 mmol, 65%). MALDI-TOF MS: m/z = 551.67 [MꢁNO3]+. IR
Table 1
Crystallographic data for ligands L1 and L3.
(ATR):
m
(C@O): 1648 cmꢁ1. Anal. Calc. for C21H36CdN6O6Sꢀ0.5-
Ligands
L1
L3
CH3OH: C, 41.05; H, 6.09; N, 13.36. Found: C, 40.95; H, 6.17; N,
Formula
C26H42N6O5S2
582.78
monoclinic
P21/c
colorless
0.12 ꢂ 0.12 ꢂ 0.10
C33H45N5O3S
591.80
monoclinic
P21/c
colorless
0.55 ꢂ 0.17 ꢂ 0.12
13.38%.
Formula weight
Crystal system
Space group
Color
Crystal size (mm)
Unit cell dimensions
a (Å)
2.3.1.9. CdL3NO3. According to the general procedure starting from
260 mg (0.845 mmol) of Cd(NO3)2ꢀ4H2O in 25 mL of MeOH and
500 mg (0.845 mmol) of L3 in 30 mL of MeOH. After refluxing
during 5 h, and slow evaporation of the solvent, colorless crystals
of pure complex were obtained. Yield: 398 mg (0.52 mmol, 62%).
15.3876(4)
9.3581(4)
20.5995(7)
90
96.683(2)
90
2946.15(18)
4
1.314
115(2)
8800
1.33–27.50
0.227
1248
11.8976(2)
19.2804(4)
16.2070(3)
90
123.135(1)
90
3113.17(10)
4
1.263
115(2)
13 962
2.94–27.49
0.146
1272
b (Å)
c (Å)
MALDI-TOF MS: m/z = 703.73 [MꢁNO3]+. IR (ATR):
m(C@O):
1685 cmꢁ1. Anal. Calc. for C33H44CdN6O6S (765.22): C, 51.80; H,
a
(°)
b (°)
5.80; N, 10.98. Found: C, 51.74; H, 5.84; N, 11.00%.
c
(°)
V (Å3)
Z
2.3.1.10. PbL1NO3. According to the general procedure starting
from 81 mg (0.243 mmol) of Pb(NO3)2 dissolved in 20 mL of H2O
and 100 mg (0.243 mmol) of L1 in 20 mL of H2O. After filtration,
the product was further washed with a mixture of methanol/water.
Yield: 10 mg (0.13 mmol, 52%). MALDI-TOF MS: m/z = 618
Dcalc (mg mꢁ3
T (K)
)
Number of reflections
h (°)
l
(mmꢁ1
)
[MꢁNO3]+. IR (ATR):
m
(C@O): 1596 cmꢁ1
.
Anal. Calc. for
F(0 0 0)
R1, wR2 [I > 2
Goodness-of-fit (GOF) on F2
r(I)]
0.0741, 0.1340
1.129
0.0388, 0.0879
1.022
C
19H32N6O6PbSꢀ2H2O (715.79): C, 31.88; H, 5.07; N, 11.74. Found:
C, 31.65; H, 5.15; N, 11.87%.

R. Kannappan et al. / Inorganica Chimica Acta 373 (2011) 150–158
153
Table 2
oxygen atom of the carbonyl group of the sulfonylacetamide arm
(Fig. 2).
Crystallographic data for complexes of L3.
Ligands L2 and L3 were obtained by equimolar addition of
2-bromo-N-tosylethanamide and 1,8-dimethylcyclam or 1,8-dib-
enzylcyclam in refluxing acetonitrile (Scheme 2). They were
isolated in 87% and 70% yield, respectively.
Ligands
CdL3NO3
33H44CdN6O6S
ZnL3NO3
CuL3Cl
Formula
Formula
weight
Crystal
system
Space group
Color
Crystal size
(mm)
Unit cell dimensions
C
C33H44N6O6SZn
718.17
C34H60ClCuN5O10
829.92
S
765.20
1H NMR shows that the two ligands contain an amidate group,
as observed for L1. These amidate forms were confirmed by X-ray
analyses. However the zwitterionic form in these two ligands is
different from L1. Indeed, the protonated nitrogen is localized on
the opposite of the sulfonylacetamide arm. This difference can be
explained by the presence of methyl or benzyl groups on the two
nitrogen atoms adjacent to the arm in L2 and L3. The remaining
secondary amine group is more basic than the three substituted
tertiary amine groups.
triclinic
monoclinic
orthorhombic
ꢀ
P21
colorless
Pbca
P1
colorless
blue
0.12 ꢂ 0.12 ꢂ 0.10 0.55 ꢂ 0.17 ꢂ 0.12 0.17 ꢂ 0.12 ꢂ 0.08
a (Å)
b (Å)
c (Å)
9.9591(2)
10.2459(4)
14.7449(5)
11.1222(4)
90
105.568(2)
90
10.2100(2)
25.8373(6)
30.7536(7)
90
90
90
11.3696(4)
15.6131(5)
74.590(1)
86.748(2)
77.240(2)
1662.24(9)
2
a
(°)
b (°)
c
(°)
3.2. Structures of L1 and L3
V (Å3)
Z
1618.64(10)
2
8112.8(3)
8
Dcalc
1.529
1.474
1.359
Some prismatic colorless crystals of L1 and L3 were obtained by
slow evaporation of MeOH. The compound L1 co-crystallized with
tosylamine, which was formed during recrystallization. L1 and L3
adopt a zwitterionic form resulting from the proton transfer of
the sulfonamide to the nitrogen atom of the macrocyclic ring. This
zwitterionic form does not involve the same nitrogen atom in L1
and in L3 and so it gives rise to different intermolecular and intra-
molecular interactions in the two ligands. Similar zwitterionic
forms have been already reported in the literature [13].
In the ligand L1, the protons on the nitrogen atom N4 interact
with the nitrogen atom N1 of the macrocyclic ring, the oxygen
atom of the pendant arm and an oxygen atom of the sulfonamide
group from another asymmetric unit. The ORTEP [14] view of inter-
and intramolecular hydrogen bonds is depicted in Fig. 2. We can
also notice that the proton H31 on N3 points toward the tosyla-
mide phenyl group. The distance and angle between hydrogen
H31 and the centroid Ct of the phenyl group reveal a weak interac-
tion (d(N3. . .Ct) = 3.471(1) Å and N3–H31–Ct = 154(3)°) [15].
The delocalization of the lone pair of the nitrogen atom can be
confirmed by infrared spectroscopy. Indeed, the C@O band appears
at 1704 cmꢁ1 in bromo-N-tosylethanamide while this value is con-
siderably lowered to 1596 and 1542 cmꢁ1 in L1 and L3,
respectively.
(mg mꢁ3
)
T (K)
Number of
115(2)
14 404
115(2)
6652
115(2)
17 642
reflections
h (°)
(mmꢁ1
2.03–27.55
0.774
792
1.90–27.48
0.879
756
1.71–27.49
0.714
3528
l
)
F(0 0 0)
R1, wR2
[I > 2
Goodness-of-
fit (GOF)
on F2
0.0378, 0.0745
0.0460, 0.0950
0.0595, 0.1218
r
(I)]
1.097
1.108
1.130
the Fourier difference maps. Their position parameters were re-
fined freely with Uiso(H) = 1.2 Ueq(N). In CdL3NO3, oxygen atoms
on the disordered nitrate anion (45/55) were constrained with
EADP instructions to maintain a reasonable model. Finally, H atoms
on water molecule in CuL3Cl were located in the Fourier difference
maps. Their position parameters were fixed.
3. Results and discussion
The X-ray structure of L3 reveals intramolecular hydrogen
bonding between a proton on N3 and nitrogen atoms N1 and N2,
as well as intermolecular hydrogen bonding with the oxygen atom
O3 from the amide group of another asymmetric unit (Fig. 3).
The C–O bond in L3 (1.2519(18) Å) is longer than in L1
(1.238(4) Å) because the intermolecular hydrogen bond between
the oxygen atom O3 and N3–H of another asymmetric unit (N3–
H. . .O3 = 2.7085(16) Å) is shorter in L3, and thus stronger than
the intramolecular hydrogen bond between the oxygen atom O3
and N3–H in L1 (N4–H. . .O3 = 2.863(4) Å). This is also consistent
3.1. Synthesis of the ligands
Ligand L1 was synthesized by reacting 10 equiv of cyclam and
1 equiv of 2-bromo-N-tosylethanamide in a low dissociating sol-
vent in order to favor the monofunctionalization of the macrocycle
(Scheme 1)[12]. The excess of unreacted cyclam was eliminated by
precipitation in cold acetonitrile.
Interestingly, proton NMR analysis displays the disappearance
of the amide proton on the sulfonamide group. Elemental analysis
and X-ray diffraction confirm this observation. These analyses re-
veal a zwitterionic neutral system containing an amidate form on
the sulfonamide group and a protonated nitrogen atom. Specifi-
cally, the proton is located on the nitrogen atom which is separated
from the nitrogen bearing the arm by a propyl group. The localiza-
tion of the proton on this nitrogen can be explained by a favorable
intramolecular hydrogen bond between this proton and the
with infrared data (L1:
m m
(CO) = 1596 cmꢁ1, L3: (CO) = 1542 cmꢁ1).
3.3. Synthesis of the complexes
The Cu(II), Zn(II), Cd(II) and Pb(II) complexes were prepared by
reaction of the ligands L1–L3 with CuCl2ꢀ2H2O, Zn(NO3)2ꢀ6H2O,
Scheme 1. Synthesis of L1.

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R. Kannappan et al. / Inorganica Chimica Acta 373 (2011) 150–158
Fig. 2. ORTEP [14] view of L1. The thermal ellipsoids are at the 50% probability level. H-atoms attached to carbon are omitted for clarity. Tosylamine which co-crystallized
with L1 is not depicted. Intramolecular (left) and intermolecular (right) hydrogen bonds are indicated by dashed lines. The D–H. . .A distances are N2H–N3 = 2.996(4) Å, N4H–
N1 = 2.867(4) Å, N4H–O3 = 2.863(4) Å, N4H–O2 = 2.754(4) Å.
Scheme 2. Synthesis of L2 and L3.
Fig. 3. ORTEP [14] drawing of L3 ligand. The thermal ellipsoids are at the 50% probability level. H-atoms attached to carbon are omitted for clarity. Intermolecular (left) and
intramolecular (right) hydrogen bonds are indicated by dashed lines. The D–H. . .A distances are N3H–N2 = 2.9047(17) Å, N3H–N1 = 3.4373(17) Å, N3H–O3 = 2.7085(16) Å.
Cd(NO3)2ꢀ4H2O and Pb(NO3)2, respectively. They were character-
EPR spectroscopy, and the solid-state structures of CuL3Cl,
ZnL3NO3, CdL3NO3 were determined by X-ray diffraction analysis.
ized by elemental analysis, mass spectrometry, UV–Vis, IR and

R. Kannappan et al. / Inorganica Chimica Acta 373 (2011) 150–158
155
This solid-state analysis shows that the amidate form was main-
tained upon complexation. Moreover, in the three structures, the
carbonyl group of the tosylacetamide arm is coordinated to the
metal cation (Figs. 4, 6 and 7).
Infrared spectra shown that the metallation of L3 with Cu(II),
Zn(II) and Cd(II) induced a shift of the CO band from 1542 to
1562–1578 cmꢁ1. This shift can be explained by the fact that after
coordination O3 atom is not involved in hydrogen bonding. The
same phenomenon was observed with the ligands L1 and L2. We
can deduce from these observations that the carbonyl group
probably coordinates to Cu(II), Zn(II) and Cd(II) in the three ligands
L1–L3. Concerning Pb(II) cation, no shift of the vibration band of the
CO bond was observed upon complexation with ligands L1–L3, sug-
gesting that the pendant arm in these complexes is not involved in
the coordination of Pb(II).
3.4. Structures of CdL3NO3, ZnL3NO3 and CuL3Cl
The crystal structures of the three complexes of L3 with Cd2+
,
Zn2+ and Cu2+ have been obtained, and the amidate form was ob-
served in three cases. The coordination geometry of the metal,
the conformation of the macrocycle and some selected bond
lengths are reported in Table 3.
The cadmium complex adopts a cis I conformation (see Fig. 4)
[16].
The asymmetric unit contains one molecule with a coordinated
nitrate counter ion disordered over two sites (55:45). The Cd(II) is
hexacoordinated by four non-coplanar nitrogen atoms of the mac-
rocycle, one oxygen from the nitrate counter ion and the oxygen of
the carbonyl group on the pendant arm. The Cd–N distances range
from 2.304(2) to 2.367(2) Å, while the Cd–O bond lengths are
2.267(2) to 2.406(5) Å, which is in good agreement with the dis-
tances found in the literature (2.332(88) and 2.412(226) for Cd–
N and Cd–O, respectively) [17]. The different distances and angles
revealed an octahedral distorted geometry (see Table 3). One may
notice the hydrogen bonding interactions between the hydrogen
atoms attached to N3 and the oxygen of the nitrate counter ion
(Fig. 5).
Fig. 5. ORTEP [14] view of H-bonds in CdL3NO3 complex. The thermal ellipsoids are
at the 50% probability level. H-atoms attached to carbon and disordered parts are
omitted for clarity. The D–H. . .A distance is N3H–O5b = 2.861(7) Å. Intermolecular
hydrogen bonds are indicated by dashed lines.
coplanar nitrogen atoms of the macrocycle and two oxygen atoms
in apical position, one from the nitrate counter ion, one from the
carbonyl group in the pendant arm.
The regular octahedral coordination sphere of Zn(II) is con-
firmed by the N–Zn–N angles (cf. Table 4) close to 90° and by the
Zn–N distances ranging from 2.054(3) to 2.237(3) Å, while the
Zn–O bond lengths are 2.131(3) and 2.229(3) Å. These values are
in good agreement with the distances found in the literature
(2.196(195) and 2.116(111) Å for Zn–N and Zn–O, respectively
The Zn(II) complex of the dibenzyl derivative L3, adopts a trans
III arrangement (see Fig. 6). The Zn(II) is hexacoordinated by four
Fig. 4. ORTEP [14] view of cis I CdL3NO3 complex. The thermal ellipsoids are at the 50% probability level. H-atoms attached to carbon and disordered parts are omitted for
clarity.

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R. Kannappan et al. / Inorganica Chimica Acta 373 (2011) 150–158
Fig. 6. ORTEP [14] view of trans III ZnL3NO3 complex. The thermal ellipsoids are at the 50% probability level. H-atoms attached to carbon are omitted for clarity. Dashed lines
indicate intramolecular hydrogen bonds. N3–H. . . O5 = 2.967(5) Å.
Fig. 7. ORTEP [14] view of trans III CuL3Cl complex. The thermal ellipsoids are at the 50% probability level. H-atoms attached to carbon and solvent molecules are omitted for
clarity.
Table 3
[18]). It is interesting to note that the Zn–N3 bond length
(2.054(3) Å) is somewhat shorter than the other Zn–N distances.
This is probably due to a hydrogen bonding interaction between
the hydrogen atom attached to N3 and the oxygen atom O5 from
the nitrate counter ion.
The complex CuL3NO3 also adopts a trans III arrangement
(Fig. 7). The asymmetric unit of the Cu(II) complex of 5 contains
the Cu(II) complex, a non-coordinated chloride counter ion, six
water molecules and one methanol molecule.
Cu(II) is pentacoordinated by four coplanar nitrogen atoms from
the macrocycle and one oxygen atom in apical position belonging
to the carbonyl group of the pendant arm. The regular pyramidal
coordination sphere of Cu2+ is confirmed by the N–Cu–N angles
Coordination geometry, conformation and selected bond lengths [Å] for CdL3NO3,
ZnL3NO3 and CuL3Cl.
Metal
Cd2+
Zn2+
Cu2+
Geometry
Symmetry
Conformation
N1–M
N2–M
N3–M
N4–M
O3–M
O4B–M
O4A–M
distorted octahedron
Oh
cis I
2.367(2)
2.365(2)
2.304(2)
2.358(2)
2.267(2)
2.406(5)
2.329(7)
octahedron
Oh
square pyramid
C4v
trans III
2.065(3)
2.084(3)
1.992(3)
2.089(3)
2.204(2)
trans III
2.117(3)
2.237(3)
2.054(3)
2.198(3)
2.131(3)
2.229(3)

R. Kannappan et al. / Inorganica Chimica Acta 373 (2011) 150–158
157
Table 4
Selected angles [°] in the complexes CdL3NO3, ZnL3NO3 and CuL3Cl.
Angle (°)
CdL3NO3
ZnL3NO3
CuL3Cl
N1–M–N2
N2–M–N3
N3–M–N4
N4–M–N1
O3–M–N1
O3–M–N2
N4–M–O4B
N4–M–O4A
79.67(8)
89.71(8)
78.40(8)
89.98(8)
75.41(7)
96.32(8)
103.04(12)
93.05(15)
93.26(12)
85.16(12)
94.78(12)
86.92(12)
81.23(11)
92.77(12)
91.66(12)
86.33(10)
90.74(11)
85.82(11)
95.95(10)
82.62(9)
91.86(9)
(Table 4) close to 90° and the Cu–N distance ranging from 1.992(3)
to 2.089(3) Å, while the Cu–O bond length is 2.204(3) Å. These dis-
tances are in good agreement with those of analogous systems
[19]. It is interesting to note that the N–Cu bond lengths are some-
what shorter than the Cu–O bond length. This deformation is re-
lated to the d9 copper(II) electronic configuration and reflects an
energy stabilization of the complex by lowering of symmetry
(‘‘Jahn–Teller’’ effect). There are also some hydrogen bonding inter-
actions between the hydrogen atom attached to N3 and the oxygen
atom from a water molecule.
3.5. UV–Vis spectral properties and EPR studies of Cu complexes
The UV–Vis spectra of the three Cu(II) complexes were recorded
in CHCl3. These complexes exhibit a d–d [20] transition band with
kmax = 620 nm for
(
e
= 125 Mꢁ1 cmꢁ1
)
L1,
648 nm
(e
= 128 Mꢁ1 cmꢁ1) for L2 and 623 nm ( = 144 Mꢁ1 cmꢁ1) for L3.
e
These kmax values are consistent with a pentacoordinated center
in a square pyramidal geometry, or an hexacoordinated center
with an octahedral geometry.
Fig. 8. X-band EPR spectra (
CuL3Cl)/toluene (3/1 v/v) solution for (a) CuL1Cl, (b) CuL2Cl and (c) CuL3Cl. The
asterisk indicates the presence of an impurity in the CuL1Cl spectrum.
m
= 9.309 GHz) recorded at 100 K in EtOH (or MeOH for
Electron paramagnetic resonance corroborates the coordination
geometry proposed for the copper ion in Cu(II) complexes. EPR
spectra were recorded in EtOH (or MeOH)/toluene 3/1 solution at
100 K for the three CuL1–3Cl complexes (Fig. 8). The spectra are
characterized by a magnetic anisotropy in frozen solution and ex-
hibit the three x, y and z contributions for Cu(II) complexes typical
of the S = 1/2 state with slight rhombic distortions.
The spectra show the typical four line pattern in the lower field
part of the spectra as expected from the coupling of the unpaired
electron with the nuclear spin (I = 3/2) of the copper(II) nucleus
[21]. The EPR parameters reported in Table 5 follow the sequence
g3 (ꢃ2.20) > g2 (ꢃ2.08) ꢃ g2 (ꢃ2.05) > ge (2.0023), which indicates
that the magnetic orbital in the ground state corresponds to
Table 5
EPR data for CuL1–3Cl complexes recorded at 100 K in EtOH (or MeOH for CuL3Cl)/
toluene (3/1 v/v) frozen solution.
Rhombicitya Az ꢂ 10ꢁ4
gz/Az
(cm)
a
Compounds g3
(= gz)
g1, g2
(cmꢁ1
191
)
CuL1Cl
CuL2Cl
CuL3Cl
2.188
2.201
2.194
2.082 0.34
2.046
2.094 0.30
2.062
2.075 0.21
2.050
114
123
118
179
186
a
dx2 , as expected for a nearly axial g tensor with small rhombic
The rhombicity of the complex gives gx – gy (g\ = gx = gy for complexes with a
ꢁy2
four order symmetry axis). The rhombicity factor [26] is defined by R = (g2 ꢁ g1)/
distortions [22]. These results are consistent with copper(II) com-
plexes in an axial symmetry, namely a tetragonal geometry around
the Cu(II) center, with a square pyramidal arrangement with slight
equatorial distortions or Jahn–Teller axially elongated octahedral
geometry. Moreover, the gi and the Az hyperfine coupling constants
values are in good agreement with those found for copper com-
plexes of N-functionalized cyclams [23].
The three complexes appear to have similar symmetry by con-
sidering the rhombicity factor R (Table 5), which is a good indicator
of the geometry, values less than 1 being typical of C4v or D4h
tetragonal geometry. According to the ligand field theory, an
increasing gz value is concomitant to the decrease of the Az value
as the equatorial ligand field becomes weaker or as the axial ligand
(g3 ꢁ g2) with g3 > g2 > g1.
values in the 120–150 cm range are typical for square pyramidal
complexes exhibiting slight to moderate distortions. Higher values
are indicative of considerable distortions. The Az and gz/Az values
indicate slight differences between the three CuL1–3Cl complexes,
and the values of 191 ꢂ 10ꢁ4 cmꢁ1 and 114 cm, respectively, for
CuL1Cl are characteristic of an axially elongated octahedral coordi-
nation geometry with almost no in plane distortion and a weak ax-
ial ligand field strength. Considering the more
r-bond donor of the
secondary amine compared to tertiary amine, L1 behaves as a
stronger ligand field chelate than L2 and L3, which explains the
slightly higher Az value and lower gz/Az ratio observed for CuL1Cl.
The values reported for CuL3Cl are also consistent with a pentaco-
ordinated or a hexacoordinated Cu(II) complex with a strong equa-
torial ligand field, that is a short in plane Cu–N bond and a longer
axial Cu–O bonds. Given that L1 and L3 are pentadentate, the
field becomes stronger due to a less overlap of the dx2
magnetic
ꢁy2
orbital with the nitrogen atom orbitals of the ligand [24]. Thus, it is
possible to get more structural information from the EPR data by
considering the gz/Az ratio, which can be used as an estimate of
the coordination geometry. Values of 110–120 cm have been as-
signed to planar or axially elongated octahedral complexes, while

158
R. Kannappan et al. / Inorganica Chimica Acta 373 (2011) 150–158
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hypothesized octahedral environment is certainly due to axial
coordination of a solvent molecule (EtOH) at the opposite side of
oxygen atom from the amide group. Finally, CuL2Cl complex shows
a slightly more distorted environment around Cu(II), as reflected
by the Az and gz/Az values.
For pentacoordinated complexes, efforts have been made to ob-
tain quantitative measurements of distortions, the simplest angu-
lar parameter commonly used for these complexes is that
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proposed by Addison [25]. A
Eq. (1), where and b describe the two largest L–M–L bond angles,
so that complexes with an ideal trigonal bipyramidal structure
have = 1, and those with ideal square pyramidal geometry have
= 0, and distorted complexes give values between 0 and 1:
s value is calculated according to
a
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s
s
s
s
¼ ð ꢁ bÞ=60
a
ð1Þ
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A value of 0.15 calculated for CuL3Cl thanks to its crystallo-
graphic data indicates an almost ideal square pyramidal geometry
with a copper ion lying in the mean plane of the four nitrogen
atoms, thus leading to a strong overlap of the metal dx2
orbital
ꢁy2
and the nitrogen atom orbitals. The weak distortion of the coordi-
nation polyhedron is mainly due to the trans III configuration
adopted by the macrocycle (Fig. 5).
4. Conclusion
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form of the three corresponding ligands. It has been shown that
the amidate form of the pendant arm is maintained in the different
complexes. In order to study competition between carboxylic and
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of coordinating arms are currently synthesized in our laboratory.
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Appendix A. Supplementary material
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23;
CCDC 763222, 763223, 763224, 763225 and 763226 contain the
supplementary crystallographic data for L3, CuL3Cl, ZnL2NO3,
CdL3NO3 and L1. These data can be obtained free of charge from
The Cambridge Crystallographic Data Centre via www.ccdc.cam.
ac.uk/data_request/cif. Supplementary data associated with this
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