Binuclear Co(II), Ni(II), Cu(II) and Zn(II) complexes with Schiff-bases derived from crown ether platforms: Rare examples of ether oxygen atoms bridging metal centers

Article abstract of DOI:10.1016/j.poly.2010.04.036

Bibracchial lariat ethers L³ and L⁴, derived from the condensation of N,N'-bis(2-aminobenzyl)-l,10-diaza-15-crown-5 or N,N'-bis(2-aminobenzyl)-4,13-diaza-18-crown-6 with salicylaldehyde, form binuclear complexes with Co(II), Ni(II), Cu(II) and Zn(II). Our studies show that the different denticity and crown moiety size of the two related receptors give rise to important differences on the structures of the corresponding complexes. Single crystal X-ray diffraction analysis shows that the [Ni ₂(L³XH₂O)₂]²⁺ and [Cu₂(L³XNO₃)] complexes constitute a rare example in which an oxygen atom of the crown moiety is bridging the two six coordinate metal ions. In contrast, none of the oxygen atoms of the crown moiety is acting as a bridging donor atom in the [Co₂(L⁴XCH ₃CN)₂]²⁺, [Cu2(L4)]2* and [Zn2(L4)]2* complexes. This is attributed to the larger size the crown moiety and the higher denticity of L⁴ compared to L³. In [Co₂(L⁴J(CH₃CN)₂]²⁺ the metal ions show a distorted octahedral coordination, while in the Cu(II) and Zn(II) analogues the metal ions are five-coordinated in a distorted trigonal bipyramidal environment. In [Cu₂(L³J(NO₃)] ⁺ the coordinated nitrate anion acts as a bidentate bridging ligand, which results in the formation of a ID coordination polymer.

Full text of DOI:10.1016/j.poly.2010.04.036

Polyhedron 29 (2010) 2269–2277
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Polyhedron
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Binuclear Co(II), Ni(II), Cu(II) and Zn(II) complexes with Schiff-bases derived
from crown ether platforms: Rare examples of ether oxygen atoms bridging metal
centers
Lea Vaiana, Marta Mato-Iglesias, David Esteban-Gómez, Carlos Platas-Iglesias,
*
**
Andrés de Blas , Teresa Rodríguez-Blas
Departamento de Química Fundamental, Facultad de Ciencias, Universidade da Coruña, Campus da Zapateira s/n 15071 A Coruña, Spain
a r t i c l e i n f o
a b s t r a c t
Bibracchial lariat ethers L3 and L4, derived from the condensation of N,N0-bis(2-aminobenzyl)-1,10-diaza-
15-crown-5 or N,N0-bis(2-aminobenzyl)-4,13-diaza-18-crown-6 with salicylaldehyde, form binuclear
complexes with Co(II), Ni(II), Cu(II) and Zn(II). Our studies show that the different denticity and crown
moiety size of the two related receptors give rise to important differences on the structures of the corre-
sponding complexes. Single crystal X-ray diffraction analysis shows that the [Ni2(L3)(H2O)2]2+ and
[Cu2(L3)(NO3)]+ complexes constitute a rare example in which an oxygen atom of the crown moiety is
bridging the two six coordinate metal ions. In contrast, none of the oxygen atoms of the crown moiety
is acting as a bridging donor atom in the [Co2(L4)(CH3CN)2]2+, [Cu2(L4)]2+ and [Zn2(L4)]2+ complexes. This
is attributed to the larger size the crown moiety and the higher denticity of L4 compared to L3. In
[Co2(L4)(CH3CN)2]2+ the metal ions show a distorted octahedral coordination, while in the Cu(II) and
Zn(II) analogues the metal ions are five-coordinated in a distorted trigonal bipyramidal environment.
In [Cu2(L3)(NO3)]+ the coordinated nitrate anion acts as a bidentate bridging ligand, which results in
the formation of a 1D coordination polymer.
Article history:
Received 22 March 2010
Accepted 27 April 2010
Available online 26 May 2010
Keywords:
Macrocyclic ligands
Crystal structures
Schiff-bases
Binuclear complexes
Crown ethers
Transition-metal complexes
Ó 2010 Elsevier Ltd. All rights reserved.
1. Introduction
Ba(II) [10], Pb(II) and Cd(II) [11–13]. We have also demonstrated
that L2 is able to form binuclear complexes with metal ions such
Transition-metal complexes of Schiff-base ligands have been
proven to be useful for the design of molecular ferromagnets, cata-
lysts for many organic reactions, models for the active sites in
metalloenzymes, optical and luminescent materials, or DNA cleav-
age reagents [1–5]. A rational control of the nuclearity of transition-
metal complexes is important to design systems with the desired
properties, as some of these applications require the presence of
more than one metal center in the particular complex. Indeed, binu-
clear complexes may have very different reactivity than mononu-
clear counterparts, thereby enabling transformations inaccessible
to single metal ions [6]. For instance, nucleic acid hydrolysis is pos-
tulated to be facilitated by the cooperative action of two metal ions
[7]. Furthermore, bi- or oligonuclear complexes containing transi-
tion metals may be formed by bridging ligands that can mediate
magnetic interactions between paramagnetic metal ions [8].
In previous works we have carried out studies to assess the dif-
ferent complexation capabilities of the bibracchial lariat ethers L1
and L2 (Scheme 1) towards divalent metal ions such as Zn(II) [9],
as Ni(II), Co(II) and Cu(II) [14], while L1 forms mononuclear com-
plexes with first row transition metal ions such as Mn(II), Co(II),
Ni(II) or Cu(II) [15,16]. These complexes represent unusual exam-
ples of structurally characterized seven coordinate (pentagonal
bipyramidal) complexes of first row transition-metal ions. Both
L1 and L2 can react with different monoaldehydes to form Schiff-
bases with interesting coordination properties towards Pb(II) and
the trivalent lanthanide ions [17–19]. Furthermore, reaction of L1
and L2 with dialdehydes led to the formation of macrobicyclic
structures that are useful for the coordination of both cations
and anions [20–22]. In this paper, we report a series of binuclear
Co(II), Ni(II), Cu(II) and Zn(II) complexes with ligands L3 and L4,
which are obtained by reaction of the corresponding precursor
(L1 or L2) with salicylaldehyde.
2. Experimental
2.1. Reagents
The diamine precursors N,N0-bis(2-aminobenzyl)-1,10-diaza-
15-crown-5 (L1) and N,N0-bis(2-aminobenzyl)-4,13-diaza-18-
crown-6 (L2) were prepared as previously described by us [16,23].
* Corresponding author. Tel.: +34 981167000; fax: +34 981167065.
** Corresponding author. Tel.: +34 981167000; fax: +34 981167065.
E-mail addresses: ucambv@udc.es (A. de Blas), mayter@udc.es (T. Rodríguez-Blas).
0277-5387/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2010.04.036

2270
L. Vaiana et al. / Polyhedron 29 (2010) 2269–2277
NH2
N
H2N
N
N
N
N
N
OH
HO
O
O
n
n
O
O
O
O
L1: n = 1
L2: n = 2
H2L3: n = 1
H2L4: n = 2
Scheme 1.
All other chemicals were purchased from commercial sources and
used without further purification. Solvents were of reagent grade
purified by the usual methods.
2.2.5. [Co2(L3)](NO3)2ꢀC3H8OꢀH2O (5)
The preparation followed the same procedure described for 1 by
using a solution of Co(NO3)2ꢀ6H2O (0.118 g, 0.406 mmol) in 8 mL of
2-propanol. The resultant solution was filtered while hot and left to
evaporate at room temperature for several days. The orange micro-
crystalline solid formed was collected by filtration and air-dried.
Yield: 0.098 g (51%). Anal. Calc. for C38H42Co2N6O11ꢀ4H2O: C,
48.11; H, 5.31; N, 8.86. Found: C, 48.00; H, 5.03; N, 8.62%. FAB-
MS: m/z (%BPI) = 814(25) [Co2(L3)(NO3)]+, 694(100) [Co(HL3)]+. IR
2.2. Synthesis
2.2.1. [Co2(L3)](ClO4)2ꢀC3H8OꢀH2O (1)
Triethylamine (65 lL, 0.466 mmol) was added with stirring to a
(KBr discs): 1606 m(C@N)imine; 1384 m .
(N–O) cmꢁ1
solution of salicylaldehyde (43 lL, 0.400 mmol) in 2-propanol
(10 mL). The mixture was refluxed for 1 h, and then a solution of
N,N’-bis(2-aminobenzyl)-1,10-diaza-15-crown-5 (L1) (0.086 g;
0.201 mmol) in 20 mL of 2-propanol was added. The resultant
solution was refluxed for 2 h, and then a solution of Co(ClO4)2ꢀ
6H2O (0.149 g, 0.407 mmol) in 2-propanol (12 mL) was added.
The mixture was heated to reflux with stirring for 4 h and the or-
ange precipitate formed was collected by filtration and air-dried.
Yield: 0.115 g (56%). Anal. Calc. for C38H42Cl2Co2N4O13ꢀC3H8OꢀH2O:
C, 47.83; H, 5.09; N, 5.44. Found: C, 47.99; H, 5.18; N, 5.61%.
FAB-MS: m/z (%BPI) = 851(53) [Co2(L3)(ClO4)]+, 694(100)
2.2.6. [Ni2(L3)](NO3)2ꢀ5H2O (6a)
The preparation of the yellow microcrystalline complex
followed the same procedure described for 1 by using a solution
of Ni(NO3)2ꢀ6H2O (0.117 g, 0.402 mmol) in 7 mL of 2-propanol.
Yield: 0.092 g (48%). Anal. Calc. for
C
38H42N6Ni2O11ꢀ5H2O: C,
47.24; H, 5.42; N, 8.70. Found: C, 47.66; H, 5.60; N, 8.54%. FAB-
MS: m/z (%BPI) = 812(75) [Ni2(L3)(NO3)]+, 693(100) [Ni(HL3)]+. IR
(KBr discs): 1606 m(C@N)imine; 1382 m
(N–O) cmꢁ1. Slow evapora-
tion of the mother liquor gave single crystals of formula
[Co(HL3)]+. IR (KBr discs): 1611
das(O–Cl–O) cmꢁ1
m(C@N)imine; 1086 mas(Cl–O); 624
[Ni2(L3)(H2O)2]2(Et3NH)(NO3)5ꢀ4H2O (6b).
.
2.2.7. [Cu2(L3)](NO3)2ꢀ2H2O (7a)
2.2.2. [Ni2(L3)](ClO4)2ꢀ4H2O (2)
The preparation of the green complex followed the same proce-
dure described for 1 by using a solution of Cu(NO3)2ꢀ6H2O (0.096 g,
0.397 mmol) in 30 mL of 2-propanol. Yield: 0.118 g (64%). Anal.
Calc. for C38H42Cu2N6O11ꢀ2H2O: C, 49.51; H, 5.03; N, 9.12. Found:
C, 50.22; H, 4.94; N, 8.67%. FAB-MS: m/z (%BPI) = 822(100)
[Cu2(L3)(NO3)]+, 698(7) [Cu(HL3)]+. IR (KBr discs): 1608
The preparation of the green microcrystalline complex followed
the same procedure described for 1 by using a solution of
Ni(ClO4)2ꢀ6H2O (0.148 g, 0.405 mmol) in 18 mL of 2-propanol.
Yield: 0.096 g (47%). Anal. Calc. for C38H42Cl2N4Ni2O13ꢀ4H2O: C,
44.61; H, 4.93; N, 5.48. Found: C, 44.75; H, 5.26; N, 5.32%.
FAB-MS: m/z (%BPI) = 851(42) [Ni2(L3)(ClO4)]+, 693(72) [Ni(HL3)]+.
m
(C@N)imine; 1384 m
(N–O) cmꢁ1. X-ray quality crystals of formula
IR (KBr discs): 1606
m(C@N)imine; 1085
mas(Cl–O); 626 das(O–Cl–O)
[Cu2(L3)(NO3)2]ꢀ2CH3CN (7b) were grown by slow diffusion of
diethyl ether into a solution of 7a in acetonitrile.
cmꢁ1
.
2.2.8. [Zn2(L3)](NO3)2ꢀ3H2O (8)
2.2.3. [Cu2(L3)](ClO4)2ꢀ2H2O (3)
The preparation of the yellow complex followed the same pro-
cedure described for 1 by using a solution of Zn(NO3)2ꢀ6H2O
(0.117 g, 0.402 mmol) in 12 mL of 2-propanol. Yield: 0.106 g
(56%). Anal. Calc. for C38H42N6O11Zn2ꢀ3H2O: C, 48.37; H, 5.13; N,
8.91. Found: C, 47.73; H, 4.77; N, 8.89%. FAB-MS: m/z
(%BPI) = 828(38) [Zn2(L3)(NO3)]+, 699(30) [Zn(HL3)]+. IR (KBr discs):
The preparation of the green complex followed the same
procedure described for 1 by using a solution of Cu(ClO4)2ꢀ6H2O
(0.147 g, 0.396 mmol) in 30 mL of 2-propanol. Yield: 0.171 g
(86%). Anal. Calc. for C38H42Cl2Cu2N4O13ꢀ2H2O: C, 45.79; H, 4.65;
N, 5.62. Found: C, 46.14; H, 4.66; N, 5.50%. FAB-MS: m/z (%BPI) =
861(100) [Cu2(L3)(ClO4)]+, 698(13) [Cu(HL3)]+. IR (KBr discs):
1614 m(C@N)imine; 1385 m .
(N–O) cmꢁ1
1608 m(C@N)imine; 1088 m .
as(Cl–O); 626 das(O–Cl–O) cmꢁ1
2.2.9. [Co2(L4)](ClO4)2ꢀH2O (9a)
2.2.4. [Zn2(L3)](ClO4)2ꢀ2H2O (4)
Triethylamine (65
l
L, 0.466 mmol) was added with stirring to a
The preparation of the complex followed the same procedure
described for 1 by using a solution of Zn(ClO4)2ꢀ6H2O (0.151 g,
0.405 mmol) in 5 mL of 2-propanol. Yield: 0.101 g (51%). Anal.
Calc. for C38H42Cl2N4O13Zn2ꢀ2H2O: C, 45.62; H, 4.63; N, 5.60. Found:
C, 45.81; H, 5.00; N, 5.45%. FAB-MS: m/z (%BPI) = 865(87)
solution of salicylaldehyde (43
(10 mL). The mixture was refluxed for 60 min and then
lL, 0.400 mmol) in 2-propanol
a
solution of N,N’-bis(2-aminobenzyl)-4,13-diaza-18-crown-6 (L2)
(0.095 g; 0.201 mmol) in 22 mL of 2-propanol was added. The
resultant solution was refluxed for 4 h, and then a solution of
Co(ClO4)2ꢀ6H2O (0.156 g, 0.426 mmol) in 2-propanol (4 mL) was
added. The mixture was heated to reflux with stirring for 4 h.
[Zn2(L3)(ClO4)]+, 699(97) [Zn(HL3)]+. IR (KBr discs): 1610
1091
as(Cl–O); 624 das(O–Cl–O) cmꢁ1
m(C@N)imine;
m
.

L. Vaiana et al. / Polyhedron 29 (2010) 2269–2277
2271
The orange precipitate formed was collected by filtration and air-
dried. Yield: 0.181 g (89%). Anal. Calc. for C40H46Cl2Co2N4O14ꢀH2O:
C, 47.40; H, 4.77; N, 5.53. Found: C, 47.58; H, 4.75; N, 5.58%.
FAB-MS: m/z (%BPI) = 895(13) [Co2(L4)(ClO4)]+, 738(45) [Co(HL4)]+.
Avance 300 using acetonitrile-d3 as solvent. IR spectra were re-
corded, as KBr discs, using a Bruker Vector 22 spectrophotometer.
2.4. X-ray crystallography
IR (KBr discs): 1606 m(C@N)imine; 1081 mas(Cl–O); 623 das(O–Cl–
O) cmꢁ1. X-ray quality crystals of formula [Co2(L4)(CH3CN)2](ClO4)2
(9b) were grown by slow evaporation of a solution of 9a in
acetonitrile.
Three-dimensional X-ray data were collected on Bruker SMART
1000 CCD (compounds 6b, 9b and 11), Bruker-Nonius FR591-Kap-
pa CCD 2000 (7b) or Bruker X8 APEXII CCD diffractometers (14b)
by the omega and phi scan method. Reflections were measured
from a hemisphere of data collected of frames each covering 0.3°
in omega. The reflections measured were corrected for Lorentz
and polarization effects and for absorption by semi-empirical
methods based on symmetry-equivalent and repeated reflections.
The solution, refinement and analysis of the single crystal X-ray
diffraction data was performed with WINGX suite for small molecule
single-crystal crystallography [24]. The structures were solved by
Patterson methods with DIRDIF99 [25] (6b and 14b), or direct meth-
ods with SHELXS-97 [27] (9b and 11) or SIR2002 [26] (7b), and refined
by full-matrix least-squares methods on F2 with SHELX97 [27]. The
hydrogen atoms were included in calculated positions and refined
by using a riding mode. Refinement converged with allowance for
thermal anisotropy of all non-hydrogen atoms. Crystal data and
details on data collection and refinement are summarized in Tables
1 and 2.
2.2.10. [Ni2(L4)](ClO4)2ꢀ2H2Oꢀ2C3H8O (10)
The preparation of the green complex followed the same proce-
dure described for 9 by using a solution of Ni(ClO4)2ꢀ6H2O (0.146 g,
0.399 mmol) in 7 mL of 2-propanol. Yield: 0.085 g (37%). Anal. Calc.
for C40H46Cl2N4Ni2O14ꢀ2H2Oꢀ2C3H8O: C, 47.99; H, 5.78; N, 4.87.
Found: C, 47.76; H, 5.90; N, 4.97%. FAB-MS: m/z (%BPI) =
895(100) [Ni2(L4)(ClO4)]+, 737(8) [Ni(HL4)]+. IR (KBr discs): 1608
m
(C@N)imine; 1083
m .
as(Cl–O); 626 das(O–Cl–O) cmꢁ1
2.2.11. [Zn2(L4)](ClO4)2 (11)
The preparation of the yellow complex followed the same pro-
cedure described for 9 by using a solution of Zn(ClO4)2ꢀ6H2O
(0.149 g, 0.400 mmol) in 3 mL of 2-propanol. Yield: 0.135 g (67%).
Anal. Calc. for C40H46Cl2N4O14Zn2: C, 47.64; H, 4.60; N, 5.56. Found:
C, 47.32; H, 5.05; N, 5.65%. FAB-MS: m/z (%BPI) = 907(9)
[Zn2(L4)(ClO4)]+, 743(30) [Zn(HL4)]+. IR (KBr discs): 1610
m
(C@N)imine; 1091 m
as(Cl–O); 624 das(O–Cl–O) cmꢁ1. X-ray quality
crystals were grown by slow diffusion of diethyl ether into a solu-
tion of 11 in acetonitrile.
3. Results and discussion
3.1. Synthesis and characterization
2.2.12. [Co2(L4)](NO3)2ꢀH2O (12)
Reaction of L3 or L4 [prepared in situ by the condensation of L1
or L2 and salicylaldehyde in the presence of triethylamine] and the
corresponding hydrated Co(II), Ni(II), Cu(II) or Zn(II) salts (perchlo-
rates or nitrates) in 2-propanol led to compounds of formula
[M2(L)](X)2ꢀysolv (M = Co, Ni, Cu or Zn). The IR and FAB-mass spec-
tra confirmed the formation of the complexes with the correspond-
ing Schiff-base lariat ether. The IR spectra (KBr disks) feature a
The preparation of the orange complex followed the same pro-
cedure described for 9 by using a solution of Co(NO3)2ꢀ6H2O
(0.119 g, 0.409 mmol) in 10 mL of 2-propanol. Yield: 0.146 g
(78%). Anal. Calc. for C40H46Co2N6O12ꢀH2O: C, 51.18; H, 5.15; N,
8.95. Found: C, 51.35; H, 5.37; N, 9.22%. FAB-MS: m/z
(%BPI) = 858(7) [Co2(L4)(NO3)]+, 738(53) [Co(HL4)]+. IR (KBr discs):
1610 m(C@N)imine; 1384 m(N–O).
2.2.13. [Ni2(L4)](NO3)2ꢀ3H2O (13)
Table 1
The preparation followed the same procedure described for 9 by
using a solution of Ni(NO3)2ꢀ6H2O (0.118 g, 0.405 mmol) in 7 mL of
Crystal data and structure refinement for 6b and 7b.
6b
7b
2-propanol. Yield: 0.112 g (57%). Anal. Calc. for C40H46N6Ni2O12
ꢀ
3H2O: C, 49.31; H, 5.38; N, 8.63. Found: C, 49.19; H, 5.42; N,
Empirical formula
Molecular weight
Temperature (K)
Wavelength (Å)
Crystal system
Space group
a (Å)
C82H116N14Ni4O33 C42H48Cu2N8O11
8.47%. FAB-MS: m/z (%BPI) = 856(100) [Ni2(L4)(NO3)]+, 737(20)
2060.73
100.0(2)
0.71073
triclinic
967.96
[Ni(HL4)]+. IR (KBr discs): 1608
m(C@N)imine; 1384 m(N–O).
120.0(2)
0.71073
triclinic
2.2.14. [Cu2(L4)](NO3)2ꢀH2O (14a)
ꢀ
ꢀ
P1
P1
The deep green complex was prepared as previously described
[16]. X-ray quality crystals of formula [Cu2(L4)](NO3)2 (14b) were
grown by slow diffusion of diethyl ether into a solution of 14a in
acetonitrile.
12.248(1)
16.675(2)
23.233(2)
95.925(2)
96.473(2)
103.102(2)
4550.9(8)
2164
10.5319(5)
11.8784(4)
17.7500(7)
93.367(3)
96.008(3)
105.385(2)
2120.55(15)
1004
b (Å)
c (Å)
a
(°)
b (°)
c
(°)
2.2.15. [Zn2(L4)](NO3)2ꢀ3H2O (15)
V (Å3)
F(0 0 0)
The preparation followed the same procedure described for 9 by
using a solution of Zn(NO3)2ꢀ6H2O (0.119 g, 0.400 mmol) in 5 mL of
2-propanol. Yield: 0.174 g (88%). Anal. Calc. for C40H46N6O12Zn2ꢀ
3H2O: C, 48.64; H, 5.31; N, 8.51. Found: C, 48.70; H, 5.25; N,
8.85%. FAB-MS: m/z (%BPI) = 681(22) [H2L4+H]+. IR (KBr discs):
Z
2
2
Calculated density (g cmꢁ3
)
1.504
0.907
1.45–28.28
0.0712
54965
21486
1.008
0.0623
0.1785
1.516
1.837
2.51–72.72
0.0823
8039
6667
1.127
0.0743
0.2092
Absorption coefficient (mmꢁ1
)
h Range for data collection (°)
Rint
Reflections measured
Reflections observed
Goodness-of-fit (GOF) on F2
1614
m(C@N)imine; 1385 m(N–O).
2.3. Measurements
a
R1
wR2 (all data)b
Largest differences peak and hole
1.527 and ꢁ0.972 1.025 and
Elemental analyses were carried out on a Carlo Erba 1180 ele-
mental analyser. FAB-mass spectra were recorded on a Fisons Qua-
tro mass spectrometer with a Cs ion gun using 3-nitrobenzyl
alcohol as matrix. 1H and 13C NMR spectra were run on a Bruker
(e Åꢁ3
)
ꢁ1.183
a
R1
wR2 = {
=
R
||Fo| ꢁ |Fc||/
R|Fo|.
b
R
[w(||Fo|2 ꢁ |Fc|2|)2]|/
R .
[w(Fo4)]}1/2

2272
L. Vaiana et al. / Polyhedron 29 (2010) 2269–2277
Table 2
Table 3
Crystal data and structure refinement for 9b, 14b and 11.
Selected bond lengths (Å) and angles (°) for 6ba.
9b
14b
11
Ni(1)–O(1)
Ni(1)–N(1)
Ni(1)–N(2)
Ni(1)–O(6)
Ni(1)–O(3)
Ni(1)–O(2)
1.940(3)
2.028(4)
2.057(4)
2.069(3)
2.077(3)
2.422(3)
Ni(2)–O(5)
Ni(2)–N(4)
Ni(2)–O(7)
Ni(2)–N(3)
Ni(2)–O(4)
Ni(2)–O(2)
1.946(3)
2.037(4)
2.051(3)
2.053(3)
2.134(3)
2.426(3)
Empirical formula C44H52Cl2Co2N6O14 C40H46Cu2N6O12 C40H46Cl2N4O14Zn2
Molecular weight 1077.68
929.91
298(2)
0.71073
monoclinic
P21/n
12.437(5)
9.476(5)
17.096(12)
90
95.01(3)
90
1999.8(19)
964
1008.45
150.0(2)
0.71073
triclinic
Temperature (K)
Wavelength (Å)
Crystal system
Space group
a (Å)
100.0(2)
0.71073
monoclinic
P21/c
10.0689(15)
10.1689(15)
22.134(3)
90
95.408(3)
90
2256.2(6)
1116
ꢀ
N(1)–Ni(1)–O(3)
O(1)–Ni(1)–N(2)
O(6)–Ni(1)–O(2)
O(1)–Ni(1)–O(6)
O(1)–Ni(1)–O(3)
O(1)–Ni(1)–N(1)
O(1)–Ni(1)–O(2)
N(2)–Ni(1)–O(6)
N(2)–Ni(1)–O(3)
N(2)–Ni(1)–N(1)
N(2)–Ni(1)–O(2)
O(2)–Ni(1)–O(3)
O(6)–Ni(1)–O(3)
O(6)–Ni(1)–N(1)
N(1)–Ni(1)–O(2)
173.1(1)
168.9(1)
173.7(1)
93.9(1)
91.4(1)
93.6(1)
92.0(1)
93.7(1)
81.0(1)
94.8(1)
80.2(1)
91.6(1)
85.8(1)
89.0(1)
93.0(1)
N(4)–Ni(2)–O(4)
O(5)–Ni(2)–N(3)
O(7)–Ni(2)–O(2)
O(5)–Ni(2)–O(7)
O(5)–Ni(2)–O(4)
O(5)–Ni(2)–N(4)
O(5)–Ni(2)–O(2)
N(3)–Ni(2)–O(7)
N(3)–Ni(2)–O(4)
N(3)–Ni(2)–N(4)
N(3)–Ni(2)–O(2)
O(2)–Ni(2)–O(4)
O(7)–Ni(2)–O(4)
O(7)–Ni(2)–N(4)
N(4)–Ni(2)–O(2)
172.5(1)
169.5(1)
177.0(1)
90.3(1)
92.1(1)
94.4(1)
91.8(1)
96.4(1)
80.2(1)
93.7(1)
81.3(1)
91.8(1)
86.0(1)
90.4(1)
91.6(1)
P1
9.971(4)
11.020(4)
11.252(4)
104.597(7)
109.533(6)
105.709(6)
1019.9(7)
520
b (Å)
c (Å)
a
(°)
b (°)
c
(°)
V (Å3)
F(0 0 0)
Z
2
2
1
Calculated density 1.586
1.544
1.642
(g cmꢁ3
)
Absorption
coefficient
0.930
1.136
1.382
(mmꢁ1
)
h Range for data
collection (°)
Rint
Reflections
measured
1.85–28.29
1.92–27.14
2.07–27.48
a
Only the bond distances and angles of one of the complex cations present in the
asymmetric unit are given.
0.0733
14726
0.0638
11822
0.0531
11523
Reflections
observed
2993
1.025
2576
0.981
3103
directly bound to a pivotal nitrogen atom, a nitrogen atom of an
imine group, two oxygen atoms of the crown moiety and an oxy-
gen atom of the phenolate group. Coordination number six is com-
pleted by an oxygen atom of an inner-sphere water molecule. The
metal ions show distorted octahedral coordination environments,
the trans angles ranging from 164.6(6)° to 177.6(1)°, and the cis an-
gles between 80.2(1)° and 95.3(1)°.
Goodness-of-fit
1.065
(GOF) on F2
a
R1
0.0450
0.1003
0.0576
0.1218
0.31 and
ꢁ0.277
0.0501
0.1244
0.59 and ꢁ0.711
wR2 (all data)b
Largest differences 0.47 and ꢁ0.603
peak and hole
(e Åꢁ3
)
In the [Ni2(L3)(H2O)2]2+ cations the macrocyclic ligand adopts
an anti conformation with the two pendant arms disposed on
opposite sides of the crown moiety. One of the Ni(II) ions is placed
above the mean square plane defined by the donor atoms of the
crown moiety, while the second Ni(II) ion is placed below that
plane. An oxygen atom of the crown moiety [O(2) or O(9), see
Fig. 1] is acting as a bridge between the two metal ions, which
are separated by ca. 4.3 Å. Weakly basic ether donors rarely bridge
metal centers [29,30], and even the bridging role for THF, one of
the most utilized ether-type ligands, is very uncommon in the solid
state [31]. A simple search into the Cambridge Structural Data Base
(Version V5.31 (2010)) shows only 26 entries for transition-metal
complexes containing bridging ether donor atoms. Among these
hits, 13 include THF bridging ligands and another 13 contain other
oxygen ether bridges. Among the latter group seven entries corre-
spond to silver complexes, three to mercury complexes and two
cadmium complexes. Our search did not provide any nickel com-
plex containing ether bridging ligands, while only one cobalt com-
plex with a THF bridge [32], another cobalt complex with a
different ether bridge [30] and one copper complex with a methyl
ether bridging group [30] were found. The distance between the
Ni(II) ions and the bridging ether oxygen atom is 0.29–0.48 Å long-
er than the remaining bond distances of the metal coordination
environments. The C–O(2)–C angle [109.7(3)°] is very close to the
ideal tetrahedral value, while the C–O(3)–C [115.0(3)°] and C–
O(4)–C [113.9(3)°] angles, which involve non bridging ether donor
atoms, are considerably more open. The distance between the two
a
R1
wR2 = {
=
R
||Fo| ꢁ |Fc||/
R|Fo|.
b
R
[w(||Fo|2 ꢁ |Fc|2|)2]|/
R .
[w(Fo4)]}1/2
band attributable to the
m(C@N)imine stretching mode at 1606–
1614 cmꢁ1. The presence of this band together with the absence
of bands due to carbonyl and/or amine vibration modes confirms
the formation of the imine. In the case of the perchlorate salts,
bands corresponding to the mas(Cl–O) stretching and das(O–Cl–O)
bending modes of the perchlorate groups appear at ca. 1100 and
630 cmꢁ1 [28]. The absorptions at ca. 630 cmꢁ1 clearly show up
without splitting, as befit uncoordinated anions. The IR spectra of
the nitrate salts show an intense band at ca. 1384 cmꢁ1 character-
istic of ionic NO3ꢁ. The FAB-mass spectrum of each complex dis-
plays a rather intense peak corresponding to the [M2(L)(X)]+
fragment (M = Co, Ni, Cu or Zn, X = ClO4ꢁ or NO3ꢁ), which indicates
the formation of the desired binuclear complexes.
3.2. X-ray crystal structures of L3 complexes
The solid state structures of compounds 6b and 7b were deter-
mined by single crystal X-ray diffraction analyses. The asymmet-
ric unit in crystals of 6b contains two complex cations
[Ni2(L3)(H2O)2]2+ with slightly different bond distances and angles
of the metal coordination environment, five nitrate anions, a trieth-
ylammonium cation and four water molecules. Inner-sphere water
molecules are involved in hydrogen bonding interaction with ni-
trate anions and non coordinated water molecules. Nitrate anions
are further involved in hydrogen bonding interactions with non
coordinated water molecules and triethylammonium cations,
giving rise to a complicated 3D hydrogen bonding network. Bond
distances and angles of the metal coordination environments are
given in Table 3, while a view of the structure of the complex
cations is shown in Fig. 1. The metal ions are six-coordinate, being
Ni(II) ions amounts to 4.3 Å. The Ni–l(O)–Ni angle is about 125°,
while the distance between the two pivotal nitrogen atoms
amounts to 5.68 Å.
Unlike the nickel compound, inspection of crystals of the cop-
per analogue 7b reveals the presence of a 1D cationic coordina-
tion polymer in which [Cu2(L3)]+ units are liked by nitrate
bridges. The crystal lattice also contains acetonitrile molecules
and a well separated nitrate anion. Table 4 summarizes selected

L. Vaiana et al. / Polyhedron 29 (2010) 2269–2277
2273
Fig. 1. PLUTON view of the two [Ni2(L3)(H2O)2]2+ complex cations present in the asymmetric unit of 6b.
bond lengths and angles of the metal coordination environments,
while the structure of the complex is depicted in Fig. 2. The Cu(II)
ions are six-coordinate, being directly bound to a pivotal nitrogen
atom, the nitrogen atom of the imine group, two oxygen atoms of
the crown moiety, the oxygen atom of a phenolate group and an
oxygen atom of a nitrate ligand. One of the ether oxygen atoms of
the crown moiety is bridging the two Cu(II) ions, as observed for
the Ni(II) analogue. The distance between the two Cu(II) ions in
0.71 Å longer than the remaining bond distances of the
metal coordination environments. The trans angles vary between
164.6(1)° and 173.1(1)°, while the cis angles of the equatorial
planes range between 77.0(1)° and 99.4(1)°.
Inspection of the crystal structure of 7b also reveals the pres-
ence of intermolecular face to face
p–p stacking interactions [33]
between the benzyl units of neighboring [Cu2(L3)(NO3)]+ units
(Fig. 2). The distance between the centers of these rings is 3.6 Å,
while the dihedral angle between the least squares planes amounts
to 8.28°.
[Cu2(L3)(NO3)]+ units amounts to 4.305(1) Å, while the Cu–
l(O)–
Cu angle is 114.3(1)°. The distance between Cu(II) ions of neigh-
boring [Cu2(L3)(NO3)]+ complexes is 6.3358(9) Å. The metal
coordination environments can be described as distorted octahe-
dral, where the Jahn–Teller distortions occur through the O(7)–
Cu(1)–O(4) and O(6)–Cu(2)–O(4) axes. Indeed, the Cu(1)–O(4),
Cu(1)–O(7), Cu(2)–O(4) and Cu(2)–O(6) distances are ca. 0.50–
3.3. X-ray crystal structures of L4 complexes
The solid state structures of compounds 9b, 14b and 11 were
also determined by single crystal X-ray diffraction analyses.
Crystals of 9b contain the cation [Co2(L4)(CH3CN)2]2+ and two
well-separated perchlorate anions, while those of 14b and 11 con-
tain cations [M2(L4)]2+ (M = Cu or Zn) and two uncoordinated
(nitrate or perchlorate) anions. Table 5 summarizes selected bond
lengths and angles of the metal coordination environments, while
the structures of the cations are depicted in Figs. 3–5. In all cases,
the macrocyclic ligand adopts an anti conformation in the com-
plexes, with the two pendant arms disposed on opposite sides of
the crown moiety. The asymmetric unit comprises a half complex
cation and one anion and, as a consequence, the two metal ions
within a complex cation are centrosymmetrically related and pos-
sess identical coordination environments. Unlike in the L3 ana-
logues, none of the oxygen atoms of the crown moiety is acting
as a bridging donor atom in the [Co2(L4)(CH3CN)2]2+, [Cu2(L4)]2+
and [Zn2(L4)]2+ complexes. This is attributed to the larger size of
the crown moiety and the presence of an additional oxygen donor
atom in L4 compared to L3.
Table 4
Selected bond lengths (Å) and angles (°) for 7b.
Cu(1)–O(1)
Cu(1)–N(1)
Cu(1)–O(2)
Cu(1)–N(2)
Cu(1)–O(7)
Cu(1)–O(4)
1.884(3)
1.975(4)
2.029(3)
2.030(3)
2.586(4)
2.531(3)
Cu(2)–O(5)
Cu(2)–N(4)
Cu(2)–O(3)
Cu(2)–N(3)
Cu(2)–O(6)
Cu(2)–O(4)
1.878(3)
1.982(4)
2.044(3)
2.020(4)
2.566(3)
2.592(3)
N(1)–Cu(1)–O(2)
O(1)–Cu(1)–N(2)
O(7)–Cu(1)–O(4)
N(1)–Cu(1)–N(2)
N(1)–Cu(1)–O(4)
O(1)–Cu(1)–N(1)
O(7)–Cu(1)–N(1)
O(7)–Cu(1)–N(2)
O(7)–Cu(1)–O(2)
O(7)–Cu(1)–O(1)
O(2)–Cu(1)–N(2)
O(4)–Cu(1)–N(2)
O(1)–Cu(1)–O(2)
O(4)–Cu(1)–O(2)
O(4)–Cu(1)–O(1)
173.1(1)
170.1(1)
164.6(1)
96.5(1)
93.3(1)
93.2(1)
81.3(1)
88.4(1)
91.9(1)
95.4(1)
81.9(1)
77.8(1)
88.8(1)
92.9(1)
99.4(1)
N(4)–Cu(2)–O(3)
O(5)–Cu(2)–N(3)
O(6)–Cu(2)–O(4)
N(4)–Cu(2)–N(3)
N(4)–Cu(2)–O(6)
O(5)–Cu(2)–N(4)
O(4)–Cu(2)–N(4)
O(4)–Cu(2)–N(3)
O(4)–Cu(2)–O(3)
O(4)–Cu(2)–O(5)
O(3)–Cu(2)–N(3)
O(6)–Cu(2)–N(3)
O(5)–Cu(2)–O(3)
O(6)–Cu(2)–O(3)
O(6)–Cu(2)–O(5)
170.7(1)
168.6(1)
169.5(1)
96.9(1)
90.7(1)
93.9(1)
93.5(1)
77.0(1)
95.1(1)
98.7(1)
81.8(1)
93.0(1)
88.2(1)
80.2(1)
90.5(1)
In the Co(II) complex the metal ions are six-coordinate, being
directly bound to a pivotal nitrogen atom [N(2)], the nitrogen atom
of the imine group, N(1), two oxygen atoms of the crown moiety,
[O(2) and O(3)], and the oxygen atom of the phenolate group
[O(1)]. Coordination number six is completed by a nitrogen atom

2274
L. Vaiana et al. / Polyhedron 29 (2010) 2269–2277
Fig. 2. (a) PLUTON view of the {[Cu2(L3)(NO3)]+} unit present in crystals of 7b. (b) View of the {[Cu2(L3)(NO3)]+}n coordination polymer present in crystals of 7b.
of an acetonitrile molecule. The metal ions present a distorted
octahedral coordination environment; the trans angles O(1)–
Co(1)–N(2) [173.7(1)°], N(1)–Co(1)–O(3) [168.8(1)°] and O(2)–
Co(1)–N(3) [172.3(1)°] are close to 180°, while the cis angles in
Table 5
Selected bond lengths (Å) and angles (°) for 9b, 14b and 11.
9b
14b
11
Co(1)–O(1)
Co(1)–N(1)
Co(1)–O(2)
Co(1)–N(2)
Co(1)–O(3)
Co(1)–N(3)
1.944(2)
2.070(3)
2.116(2)
2.127(3)
2.170(2)
2.266(3)
Cu(1)–O(1)
Cu(1)–N(1)
Cu(1)–N(2)
Cu(1)–O(2)
Cu(1)–O(3)
1.864(3)
1.961(3)
1.999(3)
2.154(3)
2.169(3)
Zn(1)–O(1)
Zn(1)–N(1)
Zn(1)–N(2)
Zn(1)–O(2)
Zn(1)–O(3)
1.905(3)
2.060(3)
3.076(3)
2.170(3)
2.240(2)
O(1)–Co(1)–N(1)
O(1)–Co(1)–O(2)
N(1)–Co(1)–O(2)
O(1)–Co(1)–N(2)
N(1)–Co(1)–N(2)
O(2)–Co(1)–N(2)
O(1)–Co(1)–O(3)
N(1)–Co(1)–O(3)
O(2)–Co(1)–O(3)
N(2)–Co(1)–O(3)
O(1)–Co(1)–N(3)
N(1)–Co(1)–N(3)
O(2)–Co(1)–N(3)
N(2)–Co(1)–N(3)
O(3)–Co(1)–N(3)
92.5(1)
96.1(1)
97.3(1)
173.7(1)
92.5(1)
79.4(1)
95.39(9)
168.8(1)
89.73(9)
80.2(1)
89.9(1)
87.2(1)
172.3(1)
94.3(1)
85.0(1)
N(2)–Cu(1)–O(2)
O(1)–Cu(1)–O(3)
N(1)–Cu(1)–O(3)
N(2)–Cu(1)–O(3)
O(2)–Cu(1)–O(3)
N(1)–Cu(1)–N(2)
O(1)–Cu(1)–O(2)
O(1)–Cu(1)–N(1)
O(1)–Cu(1)–N(2)
N(1)–Cu(1)–O(2)
82.0(1)
96.4(1)
123.9(1)
79.5(1)
105.0(1)
95.2(1)
90.7(1)
94.4(1)
170.2(1)
129.7(1)
N(2)–Zn(1)–O(2)
O(1)–Zn(1)–O(3)
N(1)–Zn(1)–O(3)
N(2)–Zn(1)–O(3)
O(2)–Zn(1)–O(3)
N(1)–Zn(1)–N(2)
O(1)–Zn(1)–O(2)
O(1)–Zn(1)–N(1)
O(1)–Zn(1)–N(2)
N(1)–Zn(1)–O(2)
77.9(1)
93.2(1)
123.6(1)
78.4(1)
113.82(9)
94.7(1)
99.6(1)
95.8(1)
169.1(1)
119.2(1)

L. Vaiana et al. / Polyhedron 29 (2010) 2269–2277
2275
Fig. 3. PLUTON view of the [Co2(L4)(CH3CN)2]2+ complex cation present in crystals of 9b.
Fig. 4. PLUTON view of the [Cu2(L4)]2+ complex cation present in crystals of 14b.
the corresponding equatorial planes range between 79.4(1)° and
97.3(1)°. The mean deviation from planarity of the three equatorial
planes are 0.095(3) Å [Co(1)N(1)N(3)O(2)O(3)], 0.061(3) Å
[Co(1)N(2)N(3)O(1)O(2)] and 0.092(3) Å [Co(1)N(1)N(2)O(1)O(3)].
In the Cu(II) and Zn(II) complexes the metal ions are five-coor-
dinate, being directly bound to a pivotal nitrogen atom [N(2)], the
nitrogen atom of the imine group, N(1), two oxygen atoms of the
crown moiety, [O(2) and O(3)], and the oxygen atom of the pheno-
late group [O(1)]. The metal ions show a distorted trigonal–bipyra-
midal coordination environment, as indicated from the value of the
group, while the pivotal nitrogen atom and the oxygen atom of
the phenolate group occupy the apical positions. The angles of
the equatorial plane [N(1)–M(1)–O(2), N(1)–M(1)–O(3) and O(2)–
M(1)–O(3), Table 3] are relatively close to the ideal value expected
for a regular trigonal-bipyramidal coordination (120°), while the
N(2)–M(1)–O(1) angles deviate by ca. 10° from the expected value
(180°).
It is important to note that the coordination environment
around the metal ion found in 14b is somewhat different than that
observed in the analogous perchlorate salt [16]. The bond distances
of the metal coordination environment are very similar for both
compounds with the exception of the Cu–O(3) distance, which
amounts to 2.169(3) Å in 14b and to 2.359(3) Å in the perchlorate
analogue. These two compounds also show significant differences
in some of the bond angles of the metal coordination environment.
index of trigonality
s
of 0.68 (14b) and 0.76 (11) (s = 0 for a perfect
square-pyramidal geometry and
s
= 1 for a regular trigonal bipyra-
midal geometry) [34,35]. The equatorial plane of the trigonal-
bipyramid can be considered to be comprised by the two oxygen
atoms of the crown moiety and the nitrogen atom of the imine

2276
L. Vaiana et al. / Polyhedron 29 (2010) 2269–2277
Fig. 5. PLUTON view of the [Zn2(L4)]2+ complex cation present in crystals of 11.
[4] G. Consiglio, S. Failla, I.P. Oliveri, R. Purrello, S. Di Bella, Dalton Trans. (2009)
10426.
The main differences affect to the N(1)–Cu(1)–O(2) and N(1)–
Cu(1)–O(3) angles, which amount to 129.7(1)° and 123.9(1)° in
14b and 145.9(2)° and 107.3(1)° in the perchlorate salt, respec-
tively. These values indicate a larger deviation from the expected
values for a perfect trigonal-bipyramidal coordination (120°) in
the case of the perchlorate analogue, which results in a value of
the index of trigonality indicating an intermediate coordination be-
tween a square-pyramidal and a trigonal-bipyramidal coordination
[5] B. Dede, I. Ozmen, F. Karipcin, Polyhedron 28 (2009) 3967.
[6] A.L. Gavrilova, B. Bosnich, Inorg. Chim. Acta 352 (2003) 24.
[7] C. Liu, M. Wang, T. Zhang, H. Sun, Coord. Chem. Rev. 248 (2004) 147.
[8] S. Alvarez, A.A. Palacios, G. Aullon, Coord. Chem. Rev. 185–186 (1999) 431.
[9] L. Vaiana, C. Platas-Iglesias, D. Esteban-Gomez, F. Avecilla, A. de Blas, T.
Rodríguez-Blas, Eur. J. Inorg. Chem. (2007) 1874.
[10] C. Platas-Iglesias, D. Esteban, V. Ojea, F. Avecilla, A. de Blas, T. Rodríguez-Blas,
Inorg. Chem. 42 (2003) 4299.
[11] D. Esteban, D. Bañobre, A. de Blas, T. Rodríguez-Blas, R. Bastida, A. Macías, A.
Rodríguez, D.E. Fenton, H. Adams, J. Mahía, Eur. J. Inorg. Chem. (2000) 1445.
[12] D. Esteban, F. Avecilla, C. Platas-Iglesias, J. Mahía, A. de Blas, T. Rodríguez-Blas,
Inorg. Chem. 41 (2002) 4337.
(s = 0.40).
4. Conclusions
[13] D. Esteban, F. Avecilla, C. Platas-Iglesias, A. de Blas, T. Rodríguez-Blas,
Polyhedron 22 (2003) 2709.
[14] L. Vaiana, C. Platas-Iglesias, D. Esteban-Gómez, F. Avecilla, J.M. Clemente-Juan,
J.A. Real, A. de Blas, T. Rodríguez-Blas, Dalton Trans. (2005) 2031.
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T. Rodríguez-Blas, Inorg. Chem. 44 (2005) 9704.
[16] C. Rodríguez-Infante, D. Esteban, F. Avecilla, A. de Blas, T. Rodríguez-Blas, J.
Mahia, A.L. Macedo, C.F.G.C. Geraldes, Inorg. Chim. Acta 317 (2001) 190.
[17] C. Platas, F. Avecilla, A. de Blas, T. Rodríguez-Blas, R. Bastida, A. Macias, A.
Rodríguez, H. Adams, J. Chem. Soc., Dalton Trans. (2001) 1699.
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J.-C.G. Bünzli, A. de Blas, T. Rodríguez-Blas, Inorg. Chem. 42 (2003) 6946.
[19] D. Esteban-Gomez, C. Platas-Iglesias, T. Enriquez-Perez, F. Avecilla, A. de Blas,
T. Rodríguez-Blas, Inorg. Chem. 45 (2006) 5407.
A series of binuclear Ni(II), Co(II), Cu(II) and Zn(II) complexes
based on 1,10-diaza-15-crown-5 or 4,13-diaza-18-crown-6 plat-
forms have been synthesized and characterized. The solid state
structures of the Ni(II) and Cu(II) complexes of the smaller ligand
L3 show a quite rare feature, as an ether oxygen atom of the crown
moiety is bridging the two metal ions. This situation is not ob-
served for the complexes of L4 as a consequence of the higher den-
ticity of this ligand and the larger size of its crown moiety.
[20] D. Esteban-Gomez, C. Platas-Iglesias, F. Avecilla, A. de Blas, T. Rodríguez-Blas,
Eur. J. Inorg. Chem. (2007) 1635.
5. Supplementary data
[21] D. Esteban-Gomez, R. Ferreiros, S. Fernandez-Martinez, F. Avecilla, C. Platas-
Iglesias, A. de Blas, T. Rodríguez-Blas, Inorg. Chem. 44 (2005) 5428.
[22] D. Esteban-Gomez, C. Platas-Iglesias, A. de Blas, L. Fabbrizzi, T. Rodríguez-Blas,
Chem. Eur. J. 14 (2008) 5829.
[23] D. Esteban, D. Bañobre, A. de Blas, T. Rodríguez-Blas, R. Bastida, A. Macias, A.
Rodríguez, D.E. Fenton, H. Adams, J. Mahia, Eur. J. Inorg. Chem. (2000) 1445.
[24] L.J. Farrugia, J. Appl. Cryst. 32 (1999) 837.
[25] P.T. Beurskens, G. Beurskens, R. de Gelder, S. Garcia-Granda, R.O. Gould, R.
Israel, J.M.M. Smits, DIRDIF99 Program System, Crystallography Laboratory,
University of Nijmegen, The Netherlands, 1999.
CCDC 770663, 770665, 770664, 770661 and 77662 contain the
supplementary crystallographic data for (6b), (7b), (9b), (11) and
(14b). These data can be obtained free of charge via http://
www.ccdc.cam.ac.uk/conts/retrieving.html, or from the Cambridge
Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ,
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Authors thank Universidade da Coruña and Xunta de Galicia
(INCITE09E1R103013ES) for generous financial support.
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