The templating effect of halides in the tetrameric copper(II) [Cu 2(LH)2(μ4-X)Cu2(LH) 2]3+ complexes (LH2 = N-(2-pyridylmethyl)-N,N- bis-[2′-hydroxy-5′-methyl-benzyl]-amine; X =

Article abstract of DOI:10.1016/j.poly.2014.03.048

The synthesis, magnetic and structural characterization of two tetrameric copper(II) complexes {N(C₄H₉)₄}-[Cu ₂(LH)₂(μ₄-Br)Cu₂(LH) ₂](PF₆)₄ (1) a

Full text of DOI:10.1016/j.poly.2014.03.048

Polyhedron 76 (2014) 117–121
Contents lists available at ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
The templating effect of halides in the tetrameric copper(II)
[Cu2(LH)2(l
4-X)Cu2(LH)2]3+ complexes (LH2 = N-(2-pyridylmethyl)-N,
N-bis-[20-hydroxy-50-methyl-benzyl]-amine; X = Br, Cl). Synthesis
and magneto-structural characterization
J. Manzur a,b, , A. Vega b,c, A. Escuer d
⇑
a Facultad de Ciencias Físicas y Matemáticas, U. de Chile, Santiago, Chile
b CEDENNA, Santiago, Chile
c Universidad Andres Bello, Facultad de Ciencias Exactas, Departamento de Ciencias Químicas, Santiago, Chile
d Departament de Química Inorgánica, Universitat de Barcelona, Av. Diagonal 645, 08028 Barcelona, Spain
a r t i c l e i n f o
a b s t r a c t
Article history:
The synthesis, magnetic and structural characterization of two tetrameric copper(II) complexes
{N(C4H9)4}-[Cu2(LH)2(l4-Br)Cu2(LH)2](PF6)4 (1) and [Cu2(LH)2(l4-Cl)Cu2(LH)2](Cl)2(PF6) (2) is described.
Received 7 January 2014
Accepted 31 March 2014
Available online 13 April 2014
LH stands for the hemi-deprotonated anion of the tripodal aminophenol ligand N-(2-pyridylmethyl)-
N,N-bis-[20-hydroxy-50-methyl-benzyl]-amine. The complexes are tetrametallic species formed around
the central halide ion which behaves as an anion template for the formation of the tetranuclear species,
by bridging two dimeric phenoxo bridged [Cu2(LH)2]2+ units. The magnetic behaviour is dominated by the
strong antiferromagnetic exchange within the dimeric unit, mediated by the phenoxo bridges:
J = ꢀ439(4) cmꢀ1, g = 2.10(2) for (1) and J = ꢀ429(2) cmꢀ1, g = 2.090(9) for (2).
Keywords:
Tetracopper complexes
Crystal structure
Template effect
Magnetism
Ó 2014 Elsevier Ltd. All rights reserved.
Phenoxo-bridged
1. Introduction
(l
4-Cl), is responsible for the self-assembly of two [Cu2L]+ units,
giving the tetrameric complex. Although synthesized, the crystal
structure of the corresponding bromide analogue has not been
reported to date. Another system was described by Noel et al. [5]
who reported different bridging modes of the bromide anion in
Over the last decades, the templating effect of anions in the
syntheses of a wide range of organic [1] and metal-organic [2]
assemblies has been firmly demonstrated. Simple mono-atomic
anions are able to nucleate polymetallic assemblies generating
interesting structures depending on various factors, such as size,
charge and nature of the nucleating atom. Halide nucleating examples
the nickel(II) complex (l6-bromo)-bis(l3-bromo)-hexakis(l2-bromo)-
tris( 2-3,5-bis(2,6diisopropylphenylimino-methyl)-pyrazolato)-
l
hexa-nickel(II) chloroform solvate.
include l3
,
l4
,
l5 and higher nuclearity metal clusters [3–8]. For
In previous works we have reported [9,10] the magneto-
structural characterization of a series of copper(II) complexes with
tripodal N,N-bis(pyridylalkyl)-aminophenol ligands. Bis-pyridyl-
aminophenols can act as polydentate ligands, producing different
polymetallic species depending on the synthetic conditions. Even
though, for the preparation of the reported complexes we started
from copper(II) chloride as the precursor salt, the chloride does
not act as a template for the assembly of polymetallic species. In
contrast, in this work the use of the pyridyl-amino-bisphenol
ligand and copper(II) chloride or bromide as the metal salt leads,
under the same experimental conditions, to the isolation of
example, Kamiyama et al. [3], reported the synthesis of the
copper(II) complex [Cu6Cl(MeO)2(pz)9] via a chloride templated
reaction. Within this complex two trinuclear units, [Cu3(MeO)
(pz)3]2+, are linked by three pyrazolate ligands. The six copper(II)
ions form a trigonal prism, and the chloride ion occupies the centre
of the cage. Paital et al. [4] described the synthesis of a new family
of tetranuclear copper(II) clusters [Cu4(l4-X)L2]ClO4 where X = Cl,
Br, I, and H3L = 2-(2-hydroxyphenyl)-1,3-bis[4-(2-hydroxyphenyl)-
3-azabut-3-enyl]-1,3-imidazolidine. The X-ray crystal structure of
the chloride species shows that the spherical Cl bridging anion
l4-halide bridged tetranuclear copper(II) species.
In this work we describe the synthesis, the magnetic properties
⇑
Corresponding author at: Facultad de Ciencias Físicas y Matemáticas, U. de
Chile, Santiago, Chile. Tel.: +56 2 29784232; fax: +56 2 26994119.
and the X-ray crystal structures of the new
l4-bromide and
l
4-chloride bridged tetranuclear copper(II) complexes, {N(C4H9)4}
E-mail address: jmanzur@ing.uchile.cl (J. Manzur).
http://dx.doi.org/10.1016/j.poly.2014.03.048
0277-5387/Ó 2014 Elsevier Ltd. All rights reserved.

118
J. Manzur et al. / Polyhedron 76 (2014) 117–121
[Cu2(LH)2(
l
4-Br)Cu2(LH)2](PF6)4, (1), and [Cu2(LH)2(
l
4-Cl)Cu2(LH)2
for Cu4C88H92N8O8 Br ꢁ (C4H9)4N ꢁ 4(PF6): C, 49.04; H: 5.07; N: 4.95;
(Cl)2(PF6), (2), with the ligand LH2 = N-(2-pyridylmethyl)-N,N-bis-
Cu: 9.98. Found: C, 50.0; H, 5.1; N, 4.8; Cu, 9.8%.
[20-hydroxy-50-methyl-benzyl]-amine.
2.4. Synthesis of [Cu2(LH)2(l4-Cl)Cu2(LH)2](Cl)2(PF6) (2)
2. Experimental
This compound was synthesized by the same procedure as the
bromide, but using CuCl2 instead CuBr2. Anal. Calc. for C88H92Cu4
Cl3F6N8O8P: C: 47.33; H: 4.16; N: 5.02; Cu: 11.38. Found: C, 48.1;
H, 4.2; N, 5.2: Cu, 11.2%.
2.1. Materials and measurements
All reagents were reagent grade and used without further
purification. HPLC quality solvents were freshly distilled under
nitrogen before use. The ligand LH2, N-(2-pyridylmethyl)-N,
N-bis-[20-hydroxy-50-methyl-benzyl]-amine, was prepared by a
Mannich reaction of bis(2-pyridylmethyl) amine, paraformalde-
hyde and p-cresol (Scheme 1), as described for similar ligands
[10]. Elemental analyses for C, H, and N were performed at
CEPEDEQ (University of Chile) on a Fison-Carlo Erba EA 1108
model analyzer. Copper was determined by atomic absorption
spectroscopy. 1H NMR spectra were recorded in CDCl3 on a Bruke-
rAMX-300 NMR spectrometer. Chemical shifts are reported as d
values downfield of an internal Me4Si reference.
Magnetic susceptibility measurements for (1) and (2) were car-
ried out on polycrystalline samples, at the Servei de Magnetoqui-
mica of the Universitat de Barcelona, with a Quantum Design
SQUID MPMS-5 equipment working in the range 2–300 K under an
external magnetic field of 1 Tesla. X-band EPR spectra were
recorded with a Brucker ES200 spectrometer.
3. Crystallographic measurements
The crystal structure of {N(C4H9)4}[Cu2(LH)2(l4-Br)Cu2(LH)2]
(PF6)4 was determined at 150 K by X-ray diffraction measurements
on a prismatic 0.38 ꢂ 0.30 ꢂ 0.28 mm3 single crystal. Data collec-
tion was run on a SMART CCD diffractometer, using
x-scans. Data
reduction was done with SAINT [12], while the structure solution by
direct methods, completion and refinement was conducted with
SHELXL [13]. Multi-scan absorption correction was applied using
SADABS [14]. The hydrogen atoms positions were calculated after
each cycle of refinement with SHELXL, using a riding model for each
structure, with C–H distance of 0.98 Å and O–H distance of 0.88 Å.
Uiso(H) values were set equal to 1.2 Ueq of the parent carbon atom
(1.5 Ueq for methyl) and 1.5 Ueq of the parent oxygen atom. During
the final stages of the refinement it was clear that there was disor-
der on the uncoordinated charge balancing hexafluorphosphate
anion. It was modelled using two disordered positions, labelled A
and B, for four of the six fluorine atoms. They were then refined
and finally held constant at 0.63/0.37 (A/B), while the fluorine to
phosphorous distance was constrained to be 1.615 Å. During the
structure completion process by difference Fourier synthesis, it
was clear that some ill defined electron density were present in
voids left by the cations and hexafluorophosphate anions. Efforts
to model this density as molecules gave no meaningful result.
The remaining and unassigned electron density was modelled
using PLATON SQUEEZE [15], a method allowing a good modelling
of unresolved electron density [16]. It leads to about 159 electrons
for each void within the unitary cell. Taking this into account, one
tetrabutylammonium cation per copper tetramer was included in
the reported formulae of the compound, C104H128BrCu4F24-
2.2. Synthesis of the ligand N-(2-pyridylmethyl)-N,N-bis-[20-hydroxy-
50-methyl-benzyl]-amine (LH2)
To a suspension of paraformaldehyde 1.8 g (0.06 mol) in meth-
anol (100 mL) were added 3.2 g (0.03 moles) of 2-pyridylmethyl-
amine [11] and 6.5 g (0.06 moles) of p-cresol. The reaction mixture
was refluxed for 48 h. under nitrogen. After cooling to room tem-
perature, the solvent was removed under vacuum and the residue
crystallized from acetonitrile giving 5.1 g (49%) of a white crystal-
line solid. 1H NMR (CDCl3): d 8.6 (1H, d, H -Py), 7.7 (1H, t, Hb-Py),
a
7.27 (1H, t, H -Py), 7.1 (1H, d, Hd-Py), 6.98 (2H, dd); 6.87 (2H, d)
c
and 6.80 (2H, d) (phenyl protons), 3.89 (2H, s, CH2-Py), 3.78 (4H,
s, CH2-Ph), 2.25 (6H, s, CH3-Ph), 10.5 (2H, broad, OH).
N9O8P4. The crystal structure of [Cu2(LH)2(l4-Cl)Cu2(LH)2](Cl)2
2.3. Synthesis of {N(C4H9)4}[Cu2(LH)2(
l
4-Br)Cu2(LH)2](PF6)4 (1)
(PF6) was determined at room temperature on a stick shaped
0.67 ꢂ 0.19 ꢂ 0.15 mm3 single crystal. During the final stages of
the refinement it became clear there was disorder on the uncoor-
dinated charge balancing hexafluorphosphate anion. It was mod-
elled using seven positions, subjected to add six fluorine atoms
per tetrameric unit. Their occupancies were then refined and
finally held constant during the last cycles of refinement. Table 1
contains data collection and structure refinement details, while
selected bond distances and bond angles are given in Table 2.
A solution of CuBr2 (0.447 g, 2 mmol) in 5 mL MeOH was added
to a solution of the ligand LH2 (0.70 g, 2 mmol) and triethylamine
(280 lL, 2 mmol) in MeOH (20 mL), and the mixture was refluxed
for 60 min. Addition of excess tetrabutylammonium hexafluoro-
phosphate to the solution precipitates the crystalline product
immediately (0.648 g, 51%). Recrystallization from boiling metha-
nol affords crystals suitable for X-ray structural studies. Anal. Calc.
CH3
OH
OH
CH2O
N
CH2 NH2
CH2
N
2
+
reflux, N2, 48 h.
CH3
N
CH3
HO
LH2
Scheme 1. Synthesis of the ligand N-(2-pyridylmethyl)-N,N-bis-[20-hydroxy-50-methyl-benzyl]-amine, LH2.

J. Manzur et al. / Polyhedron 76 (2014) 117–121
119
hemi-deprotonated anion of the N-(2-pyridylmethyl)-N,N-bis-[20-
hydroxy-50-methyl-benzyl]amine ligand) were obtained straight-
forward as dark brown polycrystalline solids from the reaction
mixture of the ligand and copper(II) salt, by precipitation with
N(C4H9)4PF6.
Table 1
Crystal data and structure refinement details for {N(C4H9)4}[Cu2(LH)2(l4-Br)Cu2
(LH)2](PF6)4 (1) and [Cu2(LH)2(l4-Cl)Cu2(LH)2](Cl)2(PF6) (2).
(1)
(2)
Formula weight
T (K)
2546.0
293
1859.76
293
Crystal system
tetragonal
P42/n
16.1565(9)
tetragonal
P42/n
16.1287(2)
4.2. Structural description
Space group
0
a (AÅ)
4.2.1. {N(C4H9)4}[Cu2(LH)2(
l4-Br)Cu2(LH)2](PF6)4 (1) and
0
20.902(2)
5456.0(6)
21.0989(7)
5488.6(2)
c (AÅ)
[Cu2(LH)2( 4-Cl)Cu2(LH)2](Cl)2 (PF6) (2)
l
0
V (ÅA3)
Z (Z0)
Both complexes display a tetrametallic [Cu2(LH)2(l4-X)Cu2
(LH)2]3+ cation, formed by two dimeric [Cu2(LH)2]2+ units bonded
to a central halide anion, which connects them as depicted in
Scheme 2. Fig. 1(a and b) show details for the [Cu2(LH)2
8(2)
1.384
1.29
8(2)
d (g cmꢀ3
l
)
1.116
0.884
1910
(mmꢀ1
)
F (000)
h range
hkl range
2334
(l
4-Br)Cu2(LH)2]3+ species. Within the cation the halide is tetrahe-
Hmin = 1.6°,hmax = 25.1° Hmin = 1.6°,hmax = 26.0°
h = ꢀ13 ? 13
h = ꢀ19 ? 14
k = ꢀ17 ? 14
l = ꢀ24 ? 24
19066, 5362(0.0575),
2663
329 parameter
(25 restrains)
1.057
0.081, 0.246
0.175, 0.331
Dmax = 1.01 and
Dmin = ꢀ1.30
drally surrounded by cupric centres, Fig. 1b. Although significant
differences in the ionic radii between bromide and chloride exist
(182 vs. 167 pm), both cations are almost isostructural.
k = 0 ? 19
l = 0 ? 24
4858, 4858(0.00), 3117
Ntot, Nuniq (Rint), Nobs
The coordination environment of each cupric centre within
[Cu2(LH)2(
hedron along the central halide, in contrast to what is observed for
[Cu4(
4-Cl)L2]ClO4 [4]; (H3L = 2-(20-hydroxyphenyl)-1,3-bis[4-(2-
l
4-X)Cu2(LH)2]3+ is well described as an elongated octa-
Refinement parameters 298 parameter
(9 restrains)
Goodness-of-fit
R1, wR2 (obs)
R1, wR2 (all)
0.94
l
0.077, 0.237
0.107, 0.262
Dmax = 0.87 and
Dmin = ꢀ1.11
hydroxyphenyl)-3-azabut-3-enyl]-1,3-imidazolidine), where the
coordination of the copper(II) centre is better described as a square
base pyramid. The hemi-deprotonated ligand molecule LHꢀ in (1)
and (2), acts as a tetradentate ligand occupying four of the six coor-
dination positions of the octahedron, while one is occupied by the
bromide and the other by the phenolate oxygen bridge. Consider-
ing that the halide ion bridges the two cupric centres within the
Cu2(LH)22+ unit, these are described as two fused face-sharing octa-
hedron. A second Cu2(LH)22+ unit, rotated by 90°, is bonded to the
other end of the bromide, defining an approximately tetrahedral
environment for this anion between the Cu2(LH)22+ units. This con-
formation allows the lowest steric hindrance between the two
dimeric units bonded to the halide.
Maximum and
minimum
Dq
Table 2
Selected bond distances (Å) and bond angles (°) for {N(C4H9)4}[Cu2(LH)2(
LH)2](PF6)4 (1) and [Cu2(LH)2(
l
4-Br)Cu2(-
l4-Cl)Cu2(LH)2](Cl)2(PF6) (2).
(1)
(2)
Cu-O2
Cu-O2i
O2-Cui
Cu-O1
Cu-N1
Cu-N2
Cu-X1
X1-Cui
X1-Cuii
X1-Cuiii
CuꢁꢁꢁCui
O2-Cu-O2i
O2-Cu-N1
O2-Cu-N2
N1-Cu-N2
O2i-Cu-Br1
N2-Cu-Br1
Cu-O2-Cui
O2-Cu-O1
N1-Cu-O1
N2-Cu-O1
O2i-Cu-N1
O2i-Cu-N2
O2-Cu-Br1
N1-Cu-Br1
Cu-Br1-Cuiii
Cu-Br1-Cui
Cuiii-Br1-Cui
Cu-Br1-Cuii
Cuii-Br1-Cuiii
Cuii-Br1-Cui
1.931 (4)
1.954 (4)
1.954 (4)
2.494(5)
1.977 (5)
2.038 (5)
3.1500 (8)
3.1500 (8)
3.1500 (8)
3.1500 (8)
2.932 (1)
1.924(4)
1.961(4)
1.961(4)
2.512(6)
1.982(5)
2.035(5)
3.0812(9)
3.0812(9)
3.0812(9)
3.0812(9)
2.923(2)
For each compound, the Cu2(LH)22+ unit is composed of two crys-
tallographically equivalent Cu(LH)+ centres related by a 180° rota-
tion. Inside the dimeric unit both metal centres are bridged
through the phenolate oxygen atoms defining a central Cu2O2,
which is better described as a butterfly, since the dihedral angles
defined by the Cu–O2–Cui and the Cu–O2 –Cui planes are as large
i
75.7 (2)
170.7 (2)
94.6 (2)
84.0 (2)
81.5 (1)
91.6 (1)
98.0 (2)
101.8(2)
87.3(2)
76.5(2)
172.3(2)
93.9(2)
84.2(2)
80.6(2)
92.3(2)
97.6(2)
96.9(2)
90.5(2)
85.8(2)
as 34.2(2)° for (1) and 33.2(2) for (2) (i: ꢀx + 1/2, ꢀy + 1/2, z).
The distance between the metal centres inside the dimer is
2.932(1) Å and 2.923(2) Å for (1) and (2), respectively. In addition
to the phenolate bridges there is an halide bridge between the cup-
ric centres, showing rather long copper to halide distances,
3.1500(8) and 3.0812(9) Å, respectively.
As depicted in Fig. 1S, the empty space available for the tetrabu-
thylammonium cation (computed by means of Platon Squeeze
[15]) has the shape of a four legged tetrahedral X (Fig. 1S), accord-
ing to the expected geometry of the cation, with rather linear C4H9
chains.
85.6(2)
104.6 (2)
168.8 (2)
81.8 (1)
104.5(2)
168.8(2)
80.6(2)
91.5 (2)
140.8(2)
56.64(2)
140.8(2)
140.8(2)
56.64(2)
140.8(2)
89.1 (1)
141.55 (2)
55.50 (2)
141.55 (2)
141.55 (2)
55.50 (2)
141.55 (2)
Copper(II) dimers Cu2(l-O-L)2 have been described forming tet-
rameric units by coordination of the copper(II) centres to an anion
[4], or to a cation like sodium [17] through the dimer bridging oxy-
gen atoms. The anion encapsulation has been known for a long
time for compounds like Cu4OX6L4, where a central O2ꢀ anion is
tetrahedrally surrounded by copper(II) ions [18].
The encapsulation of halides within several arrangements of
metal ions has been reported, including four metal ions connected
in a rather square planar environment [19] or six metal neighbours
in an anti-prismatic [20] or even planar hexagonal environment
Symmetry labels: i: ꢀx + 1/2, ꢀy + 1/2, z; ii: y, ꢀx + 1/2, ꢀz + 3/2; iii: ꢀy + 1/2, x,
ꢀz + 3/2.
4. Results and discussion
4.1. Synthesis
[21]. Paital et al. [4] reported the syntheses of a family of l4-halide
tetrameric copper(II) complexes, but only the X-ray structure of
the chloride analogue was determined. The geometry around the
encapsulated anion is highly flexible and it is determined mainly
The compounds {N(C4H9)4}[Cu2(LH)2(
l4-Br)Cu2(LH)2](PF6)4
(1) and [Cu2(LH)2( 4-Cl)Cu2(LH)2](Cl)2(PF6) (2), (LH is the
l

120
J. Manzur et al. / Polyhedron 76 (2014) 117–121
3+
elongated Oh (4+2) environment with no distortion towards a tri-
HO
gonal bypyramid geometry. Bond parameters (Table 2), including
the Cu-(O2,O20)-Cu0 dihedral angles, exhibit very close values of
33.2 and 34,2° for (1) and (2), respectively. Both compounds show
very similar magnetic behaviour as can be anticipated from their
N
OH
Cu
N
O
Cu
structural similarities. At room temperature the
vMT value is close
to 0.30 cm3 molꢀ1 K, well below the theoretical value of
0.750 cm3 molꢀ1 K for two 1/2 spin non coupled copper centers,
with a g value of 2.0 (Fig. 2), suggesting a very strong antiferromag-
N
O
N
netic interaction. The value of the
vMT product decreases continu-
X
ously until ca. zero and both compounds become diamagnetic
below 80 K. The magnetic susceptibility curve does not show a
maximum in the experiment temperature range, being above room
temperature.
N
N
Cu
O
The copper(II) cations in each dinuclear subunit are linked by
two O-phenolate atoms, and according to reported DFT calcula-
tions [22] the antiferromagnetic exchange for Cu–O–Cu bond
angles close to 98° should be strong. In contrast, the interaction
O
Cu
N
OH
N
HO
through the halogen bridge (Cu-(l4-X)-Cu) between dinuclear sub-
units is expected to be weak, since the overlap mainly involves the
non magnetic dz2 copper(II) orbitals. The shape of the curve indi-
cates a dominant antiferromagnetic coupling, which results from
the interaction between the copper(II) atoms mediated by the
phenoxo bridges. The parameters that determine the magnitude
of the magnetic exchange in this type of systems, with two phen-
oxo bridges, are the geometry around the copper atoms, the Cu–O–
Cu angle and the dihedral Cu–O–O–Cu angle. Therefore, if the
interaction mediated by the Cu–O–Cu angle is strong, the Cu2 frag-
ments are fully coupled at moderated temperatures, and the eval-
uation of the magnetic exchange coupling constant due to the
halogen bridge becomes null.
N
O-
N
X = Br- (1)
X = Cl- (2)
N
N
OH
OH
O-
Scheme 2. General structure of the [Cu2(LH)2(
l
4-X)Cu2(LH)2]3+ cation.
According to the above considerations the interaction mediated
by the halide bridge was assumed as negligible and the experimen-
tal data was fitted with the Bleaney–Bowers equation [23] derived
from the Hamiltonian H = ꢀ J(S1ꢁS2).
ꢀ
ꢁ
2Ng2b2
kT
1
vM
¼
3 þ expðꢀJ=kTÞ
Best fit parameters were J = ꢀ439(4) cmꢀ1, g = 2.10(2) for the Br
complex (1) and J = ꢀ429(2) cmꢀ1, g = 2.090(9) for the Cl complex
(2), These magnetic exchange coupling constants are comparable
to other reported complexes with similar structural parameters
[24].
The CuꢁꢁꢁCu distances of 2.932(1) Å and 2.923(2) Å for (1) and
(2) inside the dimeric subunits should make operative dipolar
interactions, but EPR spectra (X-band) do not show evidence of
splitting of the bands due to D effect (Fig. 2). The spectra for both
compounds is very similar, exhibiting a main absorption at
Fig. 1. Molecular structure diagram for the cationic dimeric [Cu2(LH)2]2+ unit (up).
The tetrameric [Cu2(LH)2(
4-Br)Cu2(LH)2]3+ cation showing the tetrahedral coordi-
l
nation of the bromine ion (down).
by the degree of flexibility of the encapsulating moieties and by the
steric hindrance between them.
To the best of our knowledge the complex reported in this work
is the first example of the encapsulation of a bromide anion within
a
tetrahedral arrangement of four copper centres, which is
structurally characterized.
4.3. Magnetic properties
Susceptibility data for compounds (1) and (2) are depicted in
Fig. 2.
vMT vs. T plot for compounds 1 (diamonds) and 2 (circles). Inset, X-band EPR
Fig. 2 as a
vMT vs T graph. Compounds (1) and (2) show an
spectrum for compound 2.

J. Manzur et al. / Polyhedron 76 (2014) 117–121
121
g = 2.098 (1) and 2.083 (2) in excellent agreement with susceptibil-
References
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4.22 (2) (Fig. 2, inset). Hiperfine coupling with A of c.a.100 G can be
observed for (2).
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first example structurally characterized of
a
l4-Br-copper(II)
tetrameric compound, which illustrates the templating effect of
the bromide anion.
Acknowledgments
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Financial support from Project FONDECYT 1120109 and Basal
Project FB0807 (CEDENNA) is gratefully acknowledged.
Appendix A. Supplementary data
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CCDC 916507 and 970887 contains the supplementary crystal-
lographic data for (1) and (2). 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, UK; fax: (+44) 1223-336-033; or e-mail:
deposit@ccdc.cam.ac.uk. Supplementary data associated with this
article can be found, in the online version, at http://dx.doi.org/
10.1016/j.poly.2014.03.048.