Two new tetranuclear copper(II) complexes: Structure and magnetic studies

Article abstract of DOI:10.1016/j.ica.2008.03.050

The syntheses, structural characterization and magnetic behaviour of two new tetranuclear copper(II) compounds with formulae [Cu₄(μ₂-PhCOO)₂(μ-bdmap)₂(μ_1,3-N₃)₂(N₃)₂(H₂O)₂] 1, and [Cu₄(μ₂-PhCOO)₂(μ-bdmap)₂(μ_1,3-N₃)₂(PhCOO)₂(CH₃OH)₂] 2, in which bdmap is 1,3-bis(dimethylamino)-2-propanolato are reported herein. The magnetic behaviour of the two complexes has been checked giving a bulk antiferromagnetic coupling in the two cases with J values of -85.4 and -89.5 cm^-1 for 1 and 2, respectively.

Full text of DOI:10.1016/j.ica.2008.03.050

Inorganica Chimica Acta 361 (2008) 4065–4069
Contents lists available at ScienceDirect
Inorganica Chimica Acta
journal homepage: www.elsevier.com/locate/ica
Two new tetranuclear copper(II) complexes: Structure and magnetic studies
a
a
a
b
b
M. Salah El Fallah a, , Ramon Vicente , Albert Escuer , Fatima Badyine , Xavier Solans , Mercè Font-Bardia
*
a Departament de Química Inorgànica, Universitat de Barcelona, Martí i Franquès, 1-11, 08028-Barcelona, Spain
b Departament de Cristalꢀlografia i Mineralogia, Universitat de Barcelona, Martí i Franquès s/n, 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 syntheses, structural characterization and magnetic behaviour of two new tetranuclear copper(II)
compounds with formulae [Cu4(l2-PhCOO)2(l-bdmap)2(l1,3-N3)2(N3)2(H2O)2] 1, and [Cu4(l2-PhCOO)2-
(l-bdmap)2(l1,3-N3)2(PhCOO)2(CH3OH)2] 2, in which bdmap is 1,3-bis(dimethylamino)-2-propanolato
are reported herein. The magnetic behaviour of the two complexes has been checked giving a bulk
antiferromagnetic coupling in the two cases with J values of ꢁ85.4 and ꢁ89.5 cmꢁ1 for 1 and 2,
respectively.
Received 30 January 2008
Received in revised form 11 March 2008
Accepted 11 March 2008
Available online 16 March 2008
Dedicated to Professor Dante Gatteschi.
Ó 2008 Elsevier B.V. All rights reserved.
Keywords:
Tetranuclear compounds
Copper(II)
Aminoalcohols
Antiferromagnetic behaviour
Countercomplementarity
1. Introduction
common dinuclear [Cu2L(l2-acetato)]2+ unit is shown in Scheme
2, (R = H, CH3, R0 = CH3). With the aim to study the influence of
The aminoalcohols 1,3-bis(dimethylamino)-2-propanol (Hbd-
map) and 1,3-bis(amino)-2-propanol (Hbdap) can generate, after
deprotonation, the anionic poly-topic ligands 1,3-bis(dimethyl-
amino)-2-propanolato (bdmap) and 1,3-bis(amino)-2-propanolato
(bdap), respectively, which contain anchoring N-donor atoms and
alkoxo units able to act as a bridge between two or three cations.
bdmap and bdap have been widely used to generate high nuclear-
ity compounds [1–18]. The analysis of the structures reported to
date shows that bdmap and bdap can use several coordination
modes [15,16]. The most common coordination mode of these li-
gands is shown in Scheme 1.
the carboxylato ligand in the coupling constant of related new
compounds with the same skeleton shown in Scheme 2 (R = CH3,
R0 = C6H5), we have reacted copper(II) benzoate with Hbdmap
and azide salts. We have been able to isolate two new polynuclear
species with formulae [Cu4(l2-PhCOO)2(l-bdmap)2(l1,3-N3)2(N3)2
(H2O)2] 1, and [Cu4(l2-PhCOO)2(l-bdmap)2(l1,3-N3)2(PhCOO)2
(CH3OH)2] 2. The compounds 1 and 2 have been structurally char-
acterised by means of single crystal X-ray diffraction and, in the
two cases, the [Cu2L(l2-benzoato)]2+ unit can be identified. In spite
of the different structural patterns, the compounds 1 and 2 may
be considered from the magnetic point of view as dinuclear
[Cu2L(l2-benzoato)]2+ entities (L = l-bdmap).
We can suppose that this dinuclear [Cu2L]3+ entity (L = l-bdmap
or l-bdap) is formed when the corresponding aminoalcohol and
the copper(II) salt are mixed in aqueous or alcoholic media. Each
metal ion has still other free coordination positions (temporally
occupied by solvent or counteranion labile ligands) that can be
used by means of the appropriate ligands to prepare new polynu-
clear compounds (complex as metal approximation).
The found J values for 1 and 2 of ꢁ85.4 and ꢁ89.5 cmꢁ1, respec-
tively, can be justified from the structural data taking into account
the orbital countercomplementarity [19].
2. Experimental
In a recent work [17], we have used the complex as metal
approximation to prepare a series of four structurally related
compounds possessing the dinuclear [Cu2L(l2-acetato)]2+ unit
(L = l-bdmap or l-bdap) with the aim to study the countercomple-
mentarity phenomenon in these compounds. The structure of the
2.1. Starting materials
Copper(II) benzoate trihydrate was prepared by mixing aqueous
solutions of copper(II) sulfate and sodium benzoate, according to
the literature method [20,21]. 1,3-Bis(dimethylamino)-2-propanol,
and sodium azide (Aldrich) were used as such.
Caution: Although no incidents were recorded in this study, azi-
do salts of metal complexes with organic ligands are potentially
* Corresponding author. Fax: +34 93 490 7725.
E-mail address: salah.elfallah@qi.ub.es (M.S. El Fallah).
0020-1693/$ - see front matter Ó 2008 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2008.03.050

4066
M.S. El Fallah et al. / Inorganica Chimica Acta 361 (2008) 4065–4069
tions attributed to the aminoalcohol are detected in the interval
2800–3095 cmꢁ1 and close to 1466 cmꢁ1 corresponding to (mC–H
R2N
NR2
and dCH ).
= M
2
O
The elemental analyses (C, N, H) for the different syntheses
were consistent with the product formulation: Found for 1: C,
34.2; H, 5.1; N, 22.6%. Calc. for C28H48Cu4N16O8: C, 33.9; H, 4.9;
N, 22.6. Found for 2: C, 43.4; H, 5.1; N, 12.8%. Calc. for C44H64Cu4-
N10O12: C, 44.8; H, 5.7; N, 11.8.
Scheme 1.
R
R
R
2.5. Crystal structure determination and refinement
H
CH3
N
N
R
R =
Good quality crystals of complex 1 and complex 2 were selected
and mounted on a MAR345 diffractometer with image plate detec-
tor. The crystallographic data, conditions retained for the intensity
data collection and some features of the structure refinements are
listed in Table 1. The accurate unit-cell parameters were deter-
mined from automatic centring of 2196 (3° < h < 31°) for 1, 105
(3° < h < 31°) for 2, refined by least-squares method. Intensities
were collected with graphite monochromated MoKa radiation for
1 and 2. 22291 (1), 30570 (2), reflections were measured in the
2.65° 6 h 6 30.00°, 2.55° 6 h 6 32.50°, range for 1, and 2, respec-
tively. 5873 (1), and 16158 (2), reflections were non-equivalent
by symmetry, Rint (on I) = 0.0661 (1) and 0.0543 (2). The observed
reflections applying the condition I > 2r(I) were, 4234 for 1, and
11926 for 2. Lorentz polarization was made for 1, 2 and absorption
corrections were made only for 1. The structures were solved by
Patterson synthesis using the SHELXS computer program [22] and re-
fined by full-matrix least-squares method, using the SHELX97 com-
O
Cu
Cu
CH3
O
O
R' =
C
C6H5
R'
Scheme 2.
explosive. Only a small amount of material should be prepared,
and it should be handled with care.
2.2. Spectral and magnetic measurements
Infrared spectra (4000–200 cmꢁ1) were recorded from KBr pel-
lets in a Perkin Elmer 1330 IR spectrophotometer. Magnetic sus-
ceptibility measurements under magnetic fields of approximately
0.1 T, in the range 2–300 K, were performed with a Quantum De-
sign MPMS-XL SQUID magnetometer at the Magnetochemistry
Service of the University of Barcelona. All measurements were per-
formed on polycrystalline samples. Diamagnetic corrections were
estimated from Pascal Tables.
puter program [23] using 22291 for 1, and 30570 for
reflections (very negative intensities were not assumed). The func-
2
P
2
2 2
tions minimised were
w
[jFoj ꢁ jFcj ] , where w = [r2(I) +
(0.0621 ꢀ P)2 + 2.9096 ꢀ P]ꢁ1 for
1
and w = [r2(I) + (0.0655 ꢀ P)2 +
1.429 ꢀ P]ꢁ1 for 2. P = (jFoj + 2jFcj )/3 for 1 and 2. f, f0, and f00 were
taken from international tables of X-ray crystallography [24].
22H atoms for 1 and all H atoms for 2 were computed and refined,
using a riding model, with an isotropic temperature factor equal to
1.2 times the equivalent temperature factor of the atom which are
linked. Final R (on F) factor was 0.0550, and 0.667, for 1 and 2,
2
2
2.3. Synthesis of complexes
2
respectively; wR (on jFoj ) was 0.1604 for 1, and 0.1496 for 2. The
2.3.1. [Cu4(l2-PhCOO)2(l-bdmap)2(l1,3-N3)2(N3)2(H2O)2] 1
To a suspension of 1.08 g (3 mmol) of Cu(PhCOO)2 ꢀ 3H2O in
50 ml of water were added 0.22 g (1.5 mmol) of 1,3-bis(dimethyl-
amino)-2-propanol in 5 ml of water: a green solution was formed.
After 1/2 h of stirring, 0.195 g (3 mmol) of sodium azide were
added. After air filtration, slow evaporation of the green solution
gave after few days green dark crystals of compound 1 suitable
for X-ray determination.
number of refined parameters was 253 and 641 for 1 and 2, respec-
tively. The maximum and the minimum shift/esd were 0.00 for 1
and 2. The molecular plots were obtained using the ORTEP32 pro-
gram [25].
3. Results and discussion
3.1. Description of the structure of [Cu4(l2-PhCOO)2(l-bdmap)2-
(l1,3-N3)2(N3)2(H2O)2] 1
2.3.2. [Cu4(l2-PhCOO)2(l-bdmap)2(l1,3-N3)2(PhCOO)2(CH3OH)2] 2
To a suspension of 1.08 (3 mmol) of Cu(PhCOO)2 ꢀ 3 H2O in
50 ml of water/methanol 1:1 was added a solution of 0.439
(3 mmol) of 1,3-bis(dimethylamino)-2-propanol in 10 ml of water:
a green solution was formed. After few minutes of stirring, a solu-
tion of 0.1 g (1.5 mmol) of sodium azide in 10 ml of water was
added and a green precipitated in small amount was formed. After
air filtration, slow evaporation of the green mother solution gave
after few days compound 2 as green crystals suitable for X-ray
determination.
The structure of the compound 1 is illustrated in Fig. 1. Selected
bonds lengths and angles are listed in Table 2. The structure of
compound 1 can be described as a tetranuclear compound formed
by two dinuclear units of copper(II) atoms [Cu2(bdmap/benzoate)]
bridged by two azido ligands in the l1,3 coordination mode. In each
dinuclear unit the copper(II) atoms are bridged by the l-bdmap li-
gand through one oxygen atom and by one l-syn-syn-benzoate li-
gand. Two azide ligands in the l1,3 coordination mode link two
copper atoms of different dinuclear units with a long and a short
distance. In the compound, the nearest-neighbour Cuꢀ ꢀ ꢀCu dis-
tances are 3.468(4) and 4.859(4) Å, corresponding to the two sets
of bdmap/benzoate and di-l1,3-azide bridges, respectively. The
coordination around the Cu(1) and Cu(2) centres is square pyrami-
dal, the Addison parameter, s is 0.08 and 0.05, respectively, [26].
The equatorial plane around Cu(1) is formed by O(1) and N(1)
(bdmap ligand), O(2) (benzoato), and N(6) (bridging azide). The
2.4. IR and analytical data
The most characteristic bands are those attributable to benzo-
ate registered as two bands centred in the ranges 1362–1405 and
1547–1595 cmꢁ1 for the two complexes. The azido band appears
and at 2071(s) cmꢁ1 for the compound 1 and at 2057(s) cmꢁ1 for
the compound 2, respectively. In the infrared spectra, the absorp-

M.S. El Fallah et al. / Inorganica Chimica Acta 361 (2008) 4065–4069
4067
Table 1
Crystal data and structure refinement for 1 and 2
Compound
1
2
Empirical formula
Formula weight
Temperature (K)
Wavelength (Å)
Crystal system, space group
Unit cell dimensions
a (Å)
b (Å)
c (Å)
a (°)
b (°)
C
28H48Cu4N16O8
C44H64Cu4N10O12
1179.21
293(2)
990.98
293(2)
0.71073
monoclinic, P21/c
0.71073
triclinic, Pi
ꢀ
8.571(4)
10.592(3)
22.494(7)
90.0
94.96(2)
90.0
2034.4(13)
2, 1.618
2.128
11.348(9)
14.503(9)
16.649(3)
110.01(3)
99.63(4)
89.90(4)
2534(3)
2, 1.546
1.725
c (°)
V (Å3)
Z, Dcalc (Mg/m3)
Absorption coefficient (mmꢁ1
)
F(000) 1016
1220
h Range for data collection (°)
Index ranges
2.65–30.00
ꢁ12 6h 6 11;
0 6k 6 14;
2.55–32.50
ꢁ15 6 h 6 16;
ꢁ21 6 k 6 20
0 6 1 6 25
0 6 1 6 31
Reflections collected
22291
30570
Independent reflections (Rint
Refinement method
)
5873 (0.0661)
full-matrix least-squares on F2
5873/4/253
1.156
R1 = 0.0550, wR2 = 0.1604
R1 = 0.0889, wR2 = 0.1772
0.542 and ꢁ0.508
16158 (0.0543)
full-matrix least-squares on F2
16158/0/641
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices [I > 2r(I)]
R indices (all data)
1.199
R1 = 0.0667, wR2 = 0.1496
R1 = 0.0995, wR2 = 0.1601
0.723 and ꢁ0.329
Largest difference in peak and hole (e Åꢁ3
)
Cu(1)–O(1), Cu(1)–N(1), Cu(1)–O(2) and Cu(1)–N(6) distances are
1.903(3), 2.030(4), 1.947(4) and 1.965(4) Å, respectively. The axial
position is occupied by the N(8)#1 atom of the other l1,3 azido li-
gand. The Cu(1)–N(8)#1 distance is 2.584(4) Å.
C(12)
C(13)
C(11)
C(14)
C(9)
C(10)
N(5)
The equatorial plane around Cu(2) is formed by O(1) and N(2)
(bdmap ligand), O(3) (carboxylato), and N(3) (terminal azide).
The Cu(2)–O(1), Cu(2)–N(2), Cu(2)–O(3) and Cu(2)–N(3) distances
are 1.1936(3), 2.064(4), 1.970(3) and 1.950(5) Å, respectively. The
axial position of Cu(2) is occupied by the oxygen atom of one water
molecule O(4). The Cu(2)–O(4) distance is 2.278(4) Å. The Cu(1)–
O(1)–Cu(2), Cu(1)–N(6)–N(7) and Cu(1)#1–N(8)–N(7) angles are
129.2(2)°, 124.87(4)° and 108.76(4), respectively. The bond dis-
tances and angles related with the benzoate ligand are in good
agreement with data reported in the literature.
O(3)
C(8)
Cu(1)#1
N(4)
N(3)
O(2)
N(8)
N(7)
N(6)
N(8)#1
O(4)
Cu(2)
N(2)
Cu(1)
N(1)
O(1)
C(7)
C(6)
C(2)
C(1)
C(5)
C(3)
C(4)
Fig. 1. ORTEP drawing of the compound 1 showing atom labelling scheme. Ellips-
oids at the 50% probability level.
3.2. Description of the structure of [Cu4(l2-PhCOO)2(l-bdmap)2-
(l1,3-N3)2(PhCOO)2(CH3OH)2] 2
The asymmetric unit contains two independent clusters of four
copper(II) atoms. The structures of the two clusters are similar
with very slight differences in bonds lengths and angles; therefore
only one tetranuclear molecule (A) will be discussed further. As
shown in Fig. 2, the structure of the tetranuclear compound can
be described as two dinuclear subunit of copper(II) atoms [Cu2(bd-
map/benzoate)] bridged by two azido ligands in the l1,3 coordina-
tion mode. Selected bonds lengths and angles are listed in Table 3.
In the molecule (A) of 2, the nearest-neighbour Cuꢀ ꢀ ꢀCu distances
are 3.489(3) and 5.233(3) Å, corresponding to the two sets of
bdmap/benzoate and di-l1,3-azide bridges, respectively. In each
dinuclear unit the copper(II) atoms are bridged by one oxygen
atom from the l-bdmap ligand and one l-syn-syn-benzoate ligand.
The coordination around the Cu(1) and Cu(2) centres is distorted
square pyramidal, the Addison parameter, s, is 0.26 and 0.07,
respectively, [26]. Around Cu(1), the equatorial plane is formed
by O(3) and N(1) (bdmap ligand), O(1) and O(4) from two benzoate
ligands (bridge and terminal ones, respectively). The Cu(1)–O(3),
Cu(1)–N(1), Cu(1)–O(1) and Cu(1)–O(4) distances are 1.943(3),
Table 2
Relevant bond lengths (Å) and angles (°) for 1
Cu(1)–O(1)
Cu(1)–O(2)
Cu(1)–N(6)
1.903(3)
1.947(4)
1.965(4)
2.030(4)
2.584(4)
3.468(4)
94.3(1)
167.9(2)
88.6(2)
85.4(1)
172.6(2)
90.2(2)
93.6(2)
93.8(2)
93.7(2)
Cu(2)–O(1)
Cu(2)–N(3)
Cu(2)–O(3)
Cu(2)–N(2)
1.936(3)
1.950(5)
1.970(3)
2.064(4)
2.278(4)
4.859(4)
Cu(1)–N(1)
Cu(1)–N(8)#1
Cu(2)–O(4)
Cu(1)ꢀ ꢀ ꢀCu(2)
Cu(1)ꢀ ꢀ ꢀCu(1)#1
O(1)–Cu(2)–N(3)
O(1)–Cu(2)–O(3)
N(3)–Cu(2)–O(3)
O(1)–Cu(2)–N(2)
N(3)–Cu(2)–N(2)
O(3)–Cu(2)–N(2)
O(1)–Cu(2)–O(4)
N(3)–Cu(2)–O(4)
O(3)–Cu(2)–O(4)
N(2)–Cu(2)–O(4)
O(1)–Cu(1)–O(2)
O(1)–Cu(1)–N(6)
O(2)–Cu(1)–N(6)
O(1)–Cu(1)–N(1)
O(2)–Cu(1)–N(1)
N(6)–Cu(1)–N(1)
O(2)–Cu(1)–N(8)#1
O(1)–Cu(1)–N(8)#1
N(1)–Cu(1)–N(8)#1
N(6)–Cu(1)–N(8)#1
Cu(1)–O(1)–Cu(2)
168.6(2)
93.4(1)
90.0(2)
85.1(1)
88.8(2)
165.4(2)
92.2(2)
98.3(2)
94.5(2)
100.1(2)
97.7(2)
129.2(2)
#1
1 ꢁ x, ꢁy, ꢁz.

4068
M.S. El Fallah et al. / Inorganica Chimica Acta 361 (2008) 4065–4069
2.0
1.5
1.0
0.5
(2)
(1)
0.0
0
50
100
150
200
250
300
T /K
Fig. 2. ORTEP drawing of the compound 2 showing atom labelling scheme. Ellips-
Fig. 3. Plot of observed vMT vs. T of (s) compound 1, (h) compound 2. Solid lines
oids at the 50% probability level.
represent the best theoretical fit for each compound (see text).
Table 3
field was 1 T. The compounds 1 and 2 show a similar moderate
antiferromagnetic behaviour with very slight differences. In Fig. 3
we show the magnetic behaviour of 1 and 2 in the form of vMT ver-
sus T plots.
Relevant bond lengths (Å) and angles (°) for 2
Molecule A
Molecule B
Cu(1)–O(1)
Cu(1)–O(3)
Cu(1)–O(4)
Cu(1)–N(1)
Cu(1)–O(6)
Cu(2)–O(3)
Cu(2)–N(3)
Cu(2)–N(2)
1.924(3)
1.943(3)
1.963(2)
2.023(4)
2.337(3)
1.890(3)
1.912(3)
1.984(3)
2.022(3)
2.572(3)
3.489(3)
5.233(3)
92.9(1)
Cu(3)–O(7)
Cu(3)–O(9)
Cu(3)–O(10)
Cu(3)–N(6)
Cu(3)–O(12)
Cu(4)–O(9)
Cu(4)–N(8)
Cu(4)–N(7)
1.904(3)
1.924(2)
1.948(2)
2.028(3)
2.317(3)
1.907(3)
1.929(3)
2.051(3)
1.858(3)
2.698(3)
3.510(3)
5.297(3)
94.5(1)
As expected, the magnetic response of the two compounds is
dominated by the antiferromagnetic coupling through the
bdmap/benzoate bridges with large Cu–OL–Cu bond angles
(129.2 for 1 and 131.0 for 2). At room temperature, compounds 1
and 2, show a vMT value of 1.667, and 2.061 cm3 K molꢁ1, respec-
tively, those values are slightly high to that expected for four
uncoupled S = 1/2 spins (1.5 cm3 K molꢁ1, g = 2.0). In the case of
compound 2, the relative high value of vMT is due probably to
the high g value which depends mainly to the environment of
copper(II) atoms. With decreasing temperature, vMT decreases
gradually for 1 and 2 to reach the zero cm3 K molꢁ1 value approx-
imately at around 10 K, indicating antiferromagnetic coupling.
The structures of 1 and 2 consist of copper ions linked between
them by bdmap/benzoate and double l1,3-azide bridges giving lin-
eal tetramer compounds. Thus, two coupling parameters (J1, J2) can
be considered to interpret the magnetic interactions in the com-
plexes 1 and 2. J1 corresponds to the bdmap/benzoate bridges,
while J2 corresponds to the double azide in the end-to-end bridging
mode in the two compounds (Scheme 3). As consequence of the
coupling scheme the Hamiltonian to use in the two cases is
H = ꢁJ1(S1S2 + S3S4) ꢁ J2(S2S3). The fit on the indicated scheme
was performed by means of the computer program CLUMAG [27].
The best fit parameters found were J1 = ꢁ85.4 cmꢁ1, J2 = ꢁ5.5 cmꢁ1
and g = 2.06 for 1 and J1 = ꢁ89.5 cmꢁ1, J2 = ꢁ7.0 cmꢁ1 and g = 2.27
for 2. The J1 values of ꢁ85.4 and ꢁ89.5 cmꢁ1 are the mean value
corresponding to the bdmap/benzoate bridges.
Cu(2)–O(2)
Cu(4)–O(8)
Cu(2)–N(5)#1
Cu(4)–N(10)#2
Cu(1)ꢀ ꢀ ꢀCu(2)
Cu(3)ꢀ ꢀ ꢀCu(4)
Cu(2)ꢀ ꢀ ꢀCu(2)#1
O(1)–Cu(1)–O(3)
O(1)–Cu(1)–O(4)
O(3)–Cu(1)–O(4)
O(1)–Cu(1)–N(1)
O(3)–Cu(1)–N(1)
O(4)–Cu(1)–N(1)
O(1)–Cu(1)–O(6)
O(3)–Cu(1)–O(6)
O(4)–Cu(1)–O(6)
N(1)–Cu(1)–O(6)
O(3)–Cu(2)–N(3)
O(3)–Cu(2)–N(2)
N(3)–Cu(2)–N(2)
O(3)–Cu(2)–O(2)
N(3)–Cu(2)–O(2)
N(2)–Cu(2)–O(2)
N(5)#1–Cu(2)–O(2)
N(5)#1–Cu(2)–O(3)
N(5)#1–Cu(2)–N(2)
N(5)#1–Cu(2)–N(3)
Cu(1)–O(3)–Cu(2)
Cu(4)ꢀ ꢀ ꢀCu(4)#2
O(7)–Cu(3)–O(9)
O(7)–Cu(3)–O(10)
O(9)–Cu(3)–O(10)
O(7)–Cu(3)–N(6)
O(9)–Cu(3)–N(6)
O(10)–Cu(3)–N(6)
O(7)–Cu(3)–O(12)
O(9)–Cu(3)–O(12)
O(10)–Cu(3)–O(12)
N(6)–Cu(3)–O(12)
O(9)–Cu(4)–N(8)
O(9)–Cu(4)–N(7)
N(8)–Cu(4)–N(7)
O(8)–Cu(4)–O(9)
O(8)–Cu(4)–N(8)
O(8)–Cu(4)–N(7)
N(10)#2–Cu(4)–O(8)
N(10)#2–Cu(4)–O(9)
N(10)#2–Cu(4)–N(7)
N(10)#2–Cu(4)–N(8)
Cu(3)–O(9)–Cu(4)
91.8(1)
89.6(1)
160.3(1)
176.1(1)
84.7(2)
89.4(1)
93.4(1)
99.3(1)
99.5(1)
90.0(1)
171.9(1)
81.9(1)
91.2(1)
93.4(1)
92.6(1)
167.8(1)
89.2(1)
98.0(1)
102.5(1)
87.6(1)
158.1(1)
175.7(1)
86.7(1)
87.7(1)
92.2(1)
104.3(1)
97.1(1)
91.4(1)
175.1(1)
85.6(1)
89.6(1)
97.6(1)
87.1(1)
170.3(1)
84.9(1)
94.36(1)
104.0(1)
87.6(1)
131.0(1)
132.7(1)
On the other side, taking into account the relatively low J2 value,
we can consider that in compounds 1 and 2 the magnetic coupling
is mainly dominated by the relative strongest interaction, J1, which
reduces the system to two dinuclear units magnetically isolated in
each compound. To prove this possibility, the experimental mag-
netic data were fitted again by using the Bleaney–Bowers expres-
sion, based on the following isotropic Hamiltonian: H = ꢁJ(S1 ꢀ S2)
#1
ꢁx, ꢁy, ꢁz.
#2
1 ꢁ x, 1 ꢁ y, z.
2.023(4), 1.924(3) and 1.963(2) Å, respectively. The axial position
is occupied by the O(6) atom of one methanol molecule. The
Cu(1)–O(6) distance is 2.337(3) Å. The equatorial plane around
Cu(2) is formed by O(3) and N(2) (bdmap ligand), O(2) (benzoate),
and N(3) (azido bridge). The Cu(2)–O(3), Cu(2)–N(2), Cu(2)–O(2)
and Cu(2)–N(3) distances are 1.890(3), 1.984(3), 1.964(3) and
2.022(3) Å, respectively. The axial position is occupied by the
N(5)#1 atom of one bridging azido ligand. The Cu(2)–N(5)#1 dis-
tance is 2.572(3) Å. The Cu(1)–O(3)–Cu(2), Cu(2)–N(3)–N(4) and
Cu(2)#1–N(5)–N(4) angles are 131.0(1)°, 124.5(4)° and 120.4(4),
respectively.
Ng2l2B 2 expðJ=kTÞ
vM
¼
ð1Þ
kT 1 þ 3 expðJ=kTÞ
The parameters N, lB and k in Eq. (1) have their usual meanings,
J = singlet–triplet splitting. Least-square fitting of experimental data
leads to the following parameter: J = ꢁ84.7 cmꢁ1 and g = 2.06 for
Cu4
Cu2
Cu1
J1
J1
Cu3
3.3. Magnetic study
J2
Magnetic measurements were carried out on polycrystalline
powder samples in the 2–300 K range of temperatures. The applied
Scheme 3.

M.S. El Fallah et al. / Inorganica Chimica Acta 361 (2008) 4065–4069
4069
complex 1; J = ꢁ86.3 cmꢁ1 and g = 2.23 for complex 2. The J values
and azido ligands with formulae [Cu4(l2-PhCOO)2(l-bdmap)2(l1,3
-
found in 1 and 2 are close to those found above. This fact confirms
that 1 and 2 behave, from the magnetic point of view, as dinuclear
compounds. It is necessary to indicate here that to fit the magnetic
data of 1 and 2, we have multiplied the Eq. (1) by 2, to reach the cor-
rect number of copper atoms in each cluster. In all the calculations,
N3)2(N3)2(H2O)2] 1, and [Cu4(l2-PhCOO)2(l-bdmap)2(l1,3-N3)2-
(PhCOO)2(CH3OH)2] 2. In compounds 1 and 2 the magnetic core
is [Cu2(l-Obdmap)(l-syn-syn-benzoate)]2+ and the relatively small
jJj values (ꢁ85.4 and ꢁ89.5 cmꢁ1) can be explained from the orbital
countercomplementarity.
P
P
2
2
the agreement factor R ¼ ½ðvMTÞobs ꢁ ðvMTÞcalcdꢂ = ½ðvMTÞobsꢂ is
lower than R = 5.7 ꢃ 10ꢁ6
.
Acknowledgements
3.4. Coupling constants correlation
The financial support given by the Spanish (CTQ2006-01759)
and Catalan (2005SGR-00593) governments are acknowledged.
It seems to be that the magnetic response of compounds 1 and 2
is dominated mainly by the expected antiferromagnetic coupling
trough the double bdmap/benzoate bridge. In the two compounds,
Appendix A. Supplementary material
the magnetic exchange is propagated principally via the dx2
ꢁy2
CCDC 676412 and 676413 contain the supplementary crystallo-
graphic data for complexes 1 and 2. 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 article can be found, in the online version, at
doi:10.1016/j.ica.2008.03.050.
orbitals of the Cu(II) ions which interact with the appropriate orbi-
tals of the oxygen or nitrogen atoms of the bdmap bridging ligand
(J1 = ꢁ85.4 and ꢁ89.5 cmꢁ1 for 1 and 2, respectively). While, the
magnetic coupling between the Cu(II) atoms through the axial
positions (long distances) should be practically negligible
(J2 = ꢁ5.5 and ꢁ7.0 cmꢁ1 for 1 and for 2, respectively). This agree
with a previous theoretical studies reported on l1,3-N3 asymmetric
double bridges with one large Cu–N distance [28].
References
In copper(II) complexes bridged by a pair of hydroxide or alkox-
ide oxygen atoms the value and sign of the jJj coupling is mainly
dependent on the Cu–O–Cu bridge angle. In a yet classical paper
Hatfield and Hodgson [29] have published a linear correlation for
homobridged [Cu(OH)2Cu]2+ dinuclear compounds between the
experimental exchange coupling constant and the Cu–O–Cu bond
angle (h). The dinuclear compounds with h larger than 97.6° are
antiferromagnetically coupled, while the coupling is ferromagnetic
if h is lower than 97.6°. For h larger than 97.6° the jJj value increases
with increasing h. The antiferromagnetic interaction in 1 and 2, ex-
pressed as jJj values of 85.4 and 89.5 cmꢁ1, respectively, is smaller
than that expected from their large Cu–O–Cu angles of 129.2 and
131.0/132.7° for which jJj values around 400 cmꢁ1 have been ob-
tained in similar polynuclear compounds with only alkoxo bridges
[15,16]. The lowering of the jJj value in heterobridged dinuclear
systems in which one hydroxo or alkoxo bridge is substituted by
one carboxylate bridging ligand is due to the orbital countercom-
plementarity phenomenon. This concept was reported for the fist
time by Nishia et al. [30] and by Mckee et al. [31] In a recent work
[17], we have reported a series of four structurally related com-
pounds possessing the dinuclear [Cu2L(l2-acetato)]2+ unit (L = l-
bdmap or l-bdap) (see Scheme 2). The Cu–O–Cu angles for these
compounds are in the range 130.3–133.3° with jJj values in the
range 109–144 cmꢁ1. The relatively low jJj values have been justi-
fied in basis to the orbital countercomplementarity. The Cu–O–Cu
angles in 1 and 2 are similar [129.2 and 131.8° (mean)] but if we
compare the jJj values (85.4 and 89.5 cmꢁ1) found in complexes 1
and 2 with the values reported for the four [Cu2L(l2-acetato)]2+
compounds [17], we observe that they are small: they decrease
30% approximately. This fact may indicate that the countercomple-
mentarity phenomenon generated for the benzoate group when
combines with the aminoalcohol is strongest than the combination
of the acetate group with the aminoalcohol.
[1] (a) R. Kivekas, Finn. Chem. Lett. (1974) 39;
(b) R. Kivekas, Finn. Chem. Lett. (1977) 252.
[2] R. Kivekas, Cryst. Struct. Commun. 6 (1977) 483.
[3] R. Kivekas, Finn. Chem. Lett. (1978) 71.
[4] A. Pajunen, R. Kivekas, Cryst. Struct. Commun. 8 (1979) 385.
[5] S. Wang, K.D.L. Smith, Z. Pang, M.J. Wagner, Chem. Commun. (1992) 1594.
[6] S. Wang, S.J. Trepanier, J.C. Zheng, Z. Pang, M.J. Wagner, Inorg. Chem. 31 (1992)
2118.
[7] S. Wang, Z. Pang, K.D.L. Smith, Inorg. Chem. 32 (1993) 4992.
[8] S. Wang, S.J. Trepanier, M.J. Wagner, Inorg. Chem. 32 (1993) 833.
[9] S. Wang, Z. Pang, J.C. Zheng, M.J. Wagner, Inorg. Chem. 32 (1993) 5975.
[10] Z. Pang, K.D.L. Smith, M.J. Wagner, J. Chem. Soc., Dalton Trans. (1994) 955.
[11] S.R. Breeze, S. Wang, L.K. Thompson, Inorg. Chim. Acta 250 (1996) 163.
[12] J. Ribas, M. Monfort, R. Costa, X. Solans, Inorg. Chem. 32 (1993) 695.
[13] M.S. El Fallah, E. Rentschler, A. Caneschi, R. Sessoli, D. Gatteschi, Inorg. Chem.
35 (1996) 3723.
[14] K.A. Fleeting, P. O’Brien, A.C. Jones, D.J. Otway, A.J.P. White, D.J. Williams, J.
Chem. Soc., Dalton Trans. (1999) 2853.
[15] M.S. El Fallah, A. Escuer, R. Vicente, F. Badyine, X. Solans, M. Font-Bardía, Inorg.
Chem. 43 (2004) 7218.
[16] A. Escuer, M.S. El Fallah, R. Vicente, N. Sanz, M. Font-Bardía, X. Solans, F.A.
Mautner, J. Chem. Soc., Dalton Trans. (2004) 1867.
[17] M.S. El Fallah, F. Badyine, R. Vicente, A. Escuer, X. Solans, M. Font-Bardıa, J.
Chem. Soc., Dalton Trans. (2006) 2934.
[18] M.S. El Fallah, F. Badyine, R. Vicente, A. Escuer, X. Solans, M. Font-Bardía, Chem.
Commun. (2006) 3113.
[19] O. Kahn, Molecular Magnetism, VCH Publishers, New York, 1993.
[20] H. Koizumi, K. Osaki, T. Watanabe, J. Phys. Soc. Jpn. 18 (1963) 117.
[21] F. Ephraim, A. Pfister, Helv. Chim. Acta 8 (1925) 374.
[22] G.M. Sheldrick, SHELXL-97, Program for the Solution for Crystal Structure,
Universität Göttingen, Germany, 1997.
[23] G.M. Sheldrick, SHELXL-97, Program for the Refinement of Crystal Structure,
Universität Göttingen, Germany, 1997.
[24] International Tables of X-ray Crystallography, vol. IV, Kynoch Press, 1974, p.
99. and 149.
[25] ORTEP 32 for Windows: L.J. Farrugia, J. Appl. Crystallogr. 30 (1997) 565.
[26] A.W. Addison, T.N. Rao, J. Reedijk, J. van Rijn, G.C. Verschoor, J. Chem. Soc.,
Dalton Trans. (1984) 1349.
[27] The series of calculations were made using the computer program CLUMAG
which uses the irreducible tensor operator formalism (ITO): D. Gatteschi, L.
Pardi, Gazz. Chim. Ital. 123 (1993) 231.
´
[28] S. Triki, J.C. Gómez-García, E. Ruiz, J. Sala-Pala, Inorg. Chem. 44 (2005) 5501.
and references cited therein.
[29] V.H. Crawford, H.W. Richardson, J.R. Wasson, D.J. Hodgson, W.E. Hatfield,
Inorg. Chem. 15 (1976) 2107.
[30] (a) Y. Nishida, S. Kida, J. Chem. Soc., Dalton Trans. (1986) 2633;
(b) Y. Nishida, M. Takeuchi, K. Takahashi, S. Kida, Chem. Lett. (1983) 1815;
(c) Y. Nishida, M. Takeuchi, K. Takahashi, S. Kida, Chem. Lett. (1985) 631.
[31] (a) V. Mckee, M. Zwagulis, J.V. Dagdigian, M.G. Patch, C.A. Reed, J. Am. Chem.
Soc. 106 (1984) 4765;
4. Conclusion
Here we have presented the syntheses, crystal structure and
magnetic study of two new tetranuclear compounds obtained from
copper(II) benzoate trihydrate, 1,3-bis(dimethylamino)-2 propanol
(b) V. Mckee, M. Zwagulis, C.A. Reed, Inorg. Chem. 24 (1985) 2914.