Use of a reduced schiff-base ligand to prepare novel chloro-bridged chains of rare Cu(II) trinuclear complexes with mixed azido/oxo and chloro/oxo bridges

Article abstract of DOI:10.1021/ic101183n

Two mixed bridged one-dimensional (1D) polynuclear complexes, [Cu ₃L₂(μ_1,1-N₃)₂(μ-Cl) Cl]_n (1) and {[Cu₃L₂(μ-Cl)₃Cl] 0.46CH₃OH}_n (2),

Full text of DOI:10.1021/ic101183n

Inorg. Chem. 2010, 49, 8155–8163 8155
DOI: 10.1021/ic101183n
Use of a Reduced Schiff-Base Ligand to Prepare Novel Chloro-Bridged Chains of
Rare Cu(II) Trinuclear Complexes with Mixed Azido/Oxo and Chloro/Oxo Bridges
†
‡
,§
,†
Apurba Biswas, Michael G. B. Drew, Carlos J. G ꢀo mez-Garc ´ı a,* and Ashutosh Ghosh*
†
Department of Chemistry, University College of Science, University of Calcutta, 92, APC Road, Kolkata-700
‡
0
09, India, School of Chemistry, The University of Reading, P.O. Box 224, Whiteknights, Reading RG 66AD,
§
U.K., and Instituto de Ciencia Molecular (ICMol), Parque Cientı ´f ico, Universidad de Valencia, 46980 Paterna,
Valencia, Spain
Received June 12, 2010
Two mixed bridged one-dimensional (1D) polynuclear complexes, [Cu L (μ -N ) (μ-Cl)Cl] (1) and {[Cu L (μ-
3
2
1,1 3 2
n
3 2
Cl) Cl] 0.46CH OH} (2), have been synthesized using the tridentate reduced Schiff-base ligand HL (2-[(2-
3
3
3
n
dimethylamino-ethylamino)-methyl]-phenol). The complexes have been characterized by X-ray structural analyses
and variable-temperature magnetic susceptibility measurements. In both complexes the basic trinuclear angular units
are joined together by weak chloro bridges to form a 1D chain. The trinuclear structure of 1 is composed of two terminal
square planar [Cu(L)(μ -N )] units connected by a central Cu(II) atom through bridging nitrogen atoms of end-on
1
,1
3
azido ligands and the phenoxo oxygen atom of the tridentate ligand. These four coordinating atoms along with a
chloride ion form a distorted trigonal bipyramidal geometry around the central Cu(II). The structure of 2 is similar; the
only difference being a Cl bridge replacing the μ -N bridge in the trinuclear unit. The magnetic properties of both
1
,1
3
trinuclear complexes can be very well reproduced with a simple linear symmetrical trimer model (H = -JSiS ) with
iþ1
only one intracluster exchange coupling (J) including a weak intertrimer interaction (j) reproduced with the molecular
field approximation. This model provides very satisfactory fits for both complexes in the whole temperature range with
-
1
-1
the following parameters: g = 2.136(3), J = -93.9(3) cm and zj = -0.90(3) cm (z = 2) for 1 and g = 2.073(7),
-
1
0
-1
J = -44.9(4) cm and zJ = -1.26(6) cm (z = 2) for 2.
Introduction
or chloro bridged copper centers by analyzing the results of
4
numerous homodibridged compounds {Cu(μ-X) Cu}, also
2
The chemistry of multinuclear copper complexes has aroused
considerable interest for their possible utility in modeling the
multimetal active sites of metalloproteins and understand-
ing the fundamental science of magnetic interactions and
magneto-structural correlations in molecular systems. A
good degree of success has been obtained in providing the ex-
change coupling between the azido, hydroxo, alkoxo, phenoxo,
4d,5
substantiated by theoretical calculations.
The simplicity
1,2
of these dimeric molecules makes them very popular as a
subject of exhaustive studies for magnetic interactions, and
the derived magneto-structural correlations can be extended
easily to relatively complicated polymeric systems to explain
their magnetic properties. For the situation where the brid-
ging species that mediate the magnetic coupling are different,
hardly any attempt has been made to correlate coupling with
geometric parameters, largely because of a lack of suitable
comparative structures containing the {Cu(μ-X)(μ-Y)Cu}
motif. There are some examples where mixed bridges link two
3
*
To whom correspondence should be addressed. E-mail: carlos.gomez@
uv.es (C.J.G.-G.), ghosh_59@yahoo.com (A.G.).
1) (a) Handbook of Metalloproteins; Messerschmidt, A., Huber, R., Poulos,
(
T., Wieghardt, K., Eds.; John Wiley & Sons: Chichester, 2001. (b) Karlin, K. D.;
Tyeklar, Z. Bioinorganic Chemistry of Copper; Chapman & Hall: New York,
1
993.
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(
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9
6, 2563.
(
(
3) Kahn, O. Molecular Magnetism; VCH Publishers: New York, 1993.
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r 2010 American Chemical Society
Published on Web 08/11/2010
pubs.acs.org/IC

8
156 Inorganic Chemistry, Vol. 49, No. 17, 2010
Biswas et al.
6
-22
copper(II) ions to result in a dinuclear entity,
and most of
exchange interactions between the paramagnetic centers of
26
them contain binucleating ligands derived from 2-formyl
such systems. Among the variety of mixed-bridging com-
plexes, those containing phenoxo- and azido-/chloro- are of
special interest because they represent valuable model com-
pounds for the active site of a number of metalloenzymes and
7-14,16,17,19,23
salicylaldehyde.
The degree of magnetic coupling between two Cu(II)
centers is related to a number of parameters which can be
determined using single crystal X-ray analysis. The pathway
for coupling is the available orbital interactions between
copper centers provided by the way in which the bridging
species arrange the local copper geometries. The most usually
encountered situations are penta-coordination with the ex-
tremes of trigonal bipyramidal and square-based pyramidal
geometry that can be derived from octahedral geometry. In
the square-pyramidal geometry, one of the ligands along the
25c,d,27
also possess interesting magnetic properties.
In this paper we report the syntheses, crystal structures,
and magnetic properties of two novel one-dimensional (1D)
polynuclear mixed bridged copper(II) complexes, [Cu L -
3
2
(μ , -N ) (μ-Cl)Cl] (1) and {[Cu L (μ-Cl) Cl] 0.46CH OH}
1
1
3 2
n
3
2
3
3
3
n
(2), obtained from the reduced Schiff base ligand 2-[(2-
dimethylamino-ethylamino)-methyl]-phenol (HL). In both
compounds, the basic trinuclear angular units are joined
together by a weak chloro bridge to form 1D chains. To our
knowledge, such mixed-bridged trinuclear species are very
rare, and bridging of such species by the chloride ion is un-
precedented although there are numerous examples of var-
z-axis is removed, and the d
x2-y2 orbital is singly occupied. On
the contrary in a trigonal bipyramidal environment, one
ligand in the xy plane is removed and the dz orbital is the
magnetic orbital”.
Examples of trinuclear Cu(II) complexes, especially those
containing the mixed bridged entitiy {Cu(μ-X)(μ-Y)Cu(μ-
X)(μ-Y)Cu} are very limited. The tri- or tetradentate Schiff
bases are found to be very useful for the construction of
phenoxo bridged trinuclear species. Such species can be linear
or bent. The literature shows that in most of the reported
compounds an additional bridging group (e.g., carboxylate,
nitrate, halide, etc.) between the copper ions is also present in
such trinuclear species, and the resulting tribridged molecules
2
“
28
ious types of chloro bridged Cu(II) complexes. The pre-
sence of an additional hydrogen atom on the N-atom in the
reduced Schiff base facilitates the formation of an interesting
H-bonding network which has also been analyzed.
14
Experimental Section
Materials. The reagents and solvents used were of commer-
cially available reagent quality.
Caution! Azide complexes are potentially explosive; and cau-
tion should be exercised when dealing with such derivatives.
Synthesis of the Reduced Schiff Base Ligand (HL) 2-[(2-
Dimethylamino-ethylamino)-methyl]-phenol. The Schiff base li-
gand was synthesized by refluxing a solution of salicylaldehyde
24,25
are linear.
There is an increasing demand for mixed-
bridged angular trinuclear copper(II) systems to obtain a
better understanding of the fundamental chemistry as well as
the magnetic properties of biomolecules. The studies of such
systems may be helpful to develop basic knowledge about the
(
0.52 mL, 5 mmol) and N,N-dimethylethylenediamine (0.54 mL,
5
0
mmol) in methanol (30 mL) for 1 h. The solution was cooled to
ꢀC, and solid sodium borohydride (210 mg, 6 mmol) was added
(
6) Kahn, O.; Sikorav, S.; Gouteron, J.; Jeannin, S.; Jeannin, Y. Inorg.
Chem. 1983, 22, 2877.
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C. J. Inorg. Chem. 1987, 26, 1375.
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Inorg. Chem. 1988, 27, 3710.
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Chem. 2009, 277.
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Inorg. Chim. Acta 1996, 248, 135.
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Soc., Dalton Trans. 1989, 1117.
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Commun. 2007, 356.
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Sinn, E.; Zubieta, J. Inorg. Chem. 1987, 26, 1271.
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004, 43, 5931.
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Polyhedron 2006, 25, 81.
19) Foxon, S. P.; Utz, D.; Astner, J.; Schindler, S.; Thaler, F.; Heine-
slowly to this methanolic solution with stirring. After comple-
tion of the addition, the resulting solution was acidified with
(
2
9
concentrated HCl (5 mL) and then evaporated to dryness. The
reduced Schiff base ligand HL was extracted from the solid mass
with methanol, and this methanol solution (ca. 20 mL) was used
for preparation of the complexes.
(
(
Synthesis of the Complex [Cu
extracted methanol solution of HL as prepared above was added
to a solution of CuCl 2H O (1.275 g, 7.5 mmol) in methanol
20 mL), and an aqueous solution (1 mL) of NaN (0.325 g,
.00 mmol) was added to this mixture with stirring. The mixture
3 2 3 2 n
L (μ1,1-N ) (μ-Cl)Cl] (1). An
(
(
2
3
2
(
3
(
5
was stirred for 1 h and filtered. The filtrate was kept undisturbed
at room temperature. Brown crystals of 1 suitable for X-ray
diffraction were obtained after several days on slow evaporation
of the solvent. Yield: (1.390 g, 76%), Anal. Calcd for C H Cl -
(
(
2
2
34
2
(
Cu
3
3 10 2
N O : C, 36.09; H, 4.68; N, 19.13; Cu, 26.04%. found: C,
6.13; H, 4.59; N, 19.01; Cu, 25.92%. IR (KBr): ν(N-H),
(
(
(25) (a) Zeng, Y.-F.; Zhao, J.-P.; Hu, B.-W.; Hu, X.; Liu, F.-C.; Ribas, J.;
2
Ribas -Arino, J.; Bu, X. -H. Chem.—Eur.J. 2007, 13, 9924. (b) Tangoulis, V.;
Panagoulis, D.; Raptopoulou, C. P.; Samara, C. D. Dalton Trans. 2008, 1752.
(c) Youngme, S.; Chotkhun, T.; Leelasubcharoen, S.; Chaichit, N.; van Albada,
G. A.; Chumillas, M. V.; Reedijk, J. Inorg. Chem. Commun. 2007, 10, 843.
(d) Sang, Y.-L.; Lin, X.-S. J. Coord. Chem. 2010, 63, 315. (e) Sang, Y.-L.; Lin,
X.-S. Trans. Met. Chem. 2009, 34, 931. (f) Jiang, J.; Chu, Z.; Huang, W. Inorg.
Chim. Acta 2009, 362, 2933.
(26) (a) Sarkar, S.; Mondal, A.; Chopra, D.; Ribas, J.; Rajak, K. K. Eur.
J. Inorg. Chem. 2006, 3510. (b) Gehring, S.; Fleischauer, P.; Paulus, H.; Haase,
W. Inorg. Chem. 1993, 32, 54. (c) Meenakumari, S.; Tiwary, S. K.; Chakravarty,
A. R. Inorg. Chem. 1994, 33, 2085.
(27) Kitajima, N.; Tollman, W. B. Prog. Inorg. Chem. 1995, 43, 419.
(28) Englert, U. Coord. Chem. Rev. 2010, 254, 537.
(29) (a) Colpas, G. J.; Hamstra, B. J.; Kampf, J. W.; Pecoraro, V. L. Inorg.
Chem. 1994, 33, 4669. (b) Biswas, A.; Drew, M. G. B.; Ghosh, A. Polyhedron
2010, 29, 1029.
(
(
mann, F. W.; Liehr, G.; Mukherjee, J.; Balamurugan, V.; Ghosh, D.;
Mukherjee, R. Dalton Trans. 2004, 2321.
(
20) Tang, J.; Costa, J. S.; Pevec, A.; Kozlevcar, B.; Massera, C.;
Roubeau, O.; Mutikainen, I.; Turpeinen, U.; Gamez, P.; Reedijk, J. Cryst.
Growth Des. 2008, 8, 1005.
21) Koval, I. A.; Huisman, M.; Stassen, A. F.; Gamez, P.; Roubeau, O.;
Belle, C.; Pierre, J. L.; Saint-Aman, E.; Luken, M.; Krebs, B.; Lutz, M.;
Spek, A. L.; Reedijk, J. Eur. J. Inorg. Chem. 2004, 4036.
22) Chattopadhyay, T.; Banu, K. S.; Banerjee, A.; Ribas, J.; Majee, A.;
(
(
Nethaji, M.; Das, D. J. Mol. Struct. 2007, 833, 13.
(
(
23) Eduok, E. E.; O’Connor, C. J. Inorg. Chim. Acta 1984, 88, 229.
24) Thakurta, S.; Chakraborty, J.; Rosair, G.; Tercero, J.; Fallah,
M. S. E.; Garribba, E.; Mitra, S. Inorg. Chem. 2008, 47, 6227.

Article
Inorganic Chemistry, Vol. 49, No. 17, 2010 8157
Table 1. Crystal Data and Structure Refinement of Complexes 1 and 2
Scheme 1. Formation of the Complexes
1
2
formula
M
C
22
H
34Cl
732.11
monoclinic
P2 /n
2
Cu
3
N
10
O
2
C
22.46
H
35.84Cl
4
Cu
3
N
4
O
2.46
733.69
monoclinic
P2 /n
19.897(3)
13.8715(8)
14.3812(12)
104.487(5)
2907.8(2)
4
1.676
2.571
1493
0.054
crystal system
space group
1
1
˚
a/A
11.5818(6)
16.2364(9)
16.2417(9)
110.392(6)
2862.8(3)
4
1.699
2.436
1492
0.059
˚
b/A
˚
c/A
β/deg
3
˚
V/A
Z
-3
D
μ/mm
F (000)
c
/g cm
-
1
R(int)
total reflections
19017
unique reflections 8292
19998
8419
I > 2σ(I)
R1, wR2
temp (K)
4705
0.0418, 0.0760
150
5690
0.0939, 0.1821
150
235 cm 1, ν(C-N), 1595 cm-1; λmax (nm), [εmax (dm mol
-
3
-1
3
cm )] (methanol), 612 (212).
-1
3 2 3 3 n
Synthesis of the Complex {[Cu L (μ-Cl) Cl] 0.46CH OH}
3
(
2). Another extracted methanol solution of HL (20 mL),
prepared using the same quantity of reactants as stated above,
was added to a solution of CuCl 2H O (1.275 g, 7.5 mmol) in
2
3
2
methanol (20 mL). The mixture was stirred for 1 h and filtered.
Deep green crystals of 2 suitable for X-ray diffraction were
obtained on keeping the filtrate at room temperature for 24 h.
1
.2 times (or 1.5 times for methyl hydrogen atoms) those of the
atom to which they were attached. Absorption corrections were
32
carried out using the ABSPACK program. In 2, two positions
Yield: (1.500 g, 82%). Anal. Calcd for [Cu
CH Cu 2.46, : C, 36.77; H, 4.92; N,
.64; Cu, 25.98%. found: C, 36.70; H, 4.98; N, 7.54; Cu,
3 2 3
L (μ-Cl) Cl],0.46-
were located for a terminal chlorine atom attached to Cu(3),
named Cl(3a) and Cl(3b), and these were given occupancy
factors, x and 1 - x. A solvent methanol molecule hydrogen
bonded to Cl(3b) was given an equivalent occupancy of 1 - x. x
3
OH, C22.46
H35.84Cl
4
3 4
N O
7
2
-
1
-1
5.86%. IR (KBr): ν(N-H), 3208 cm , ν(C-N), 1596 cm
;
3
-1
-1
λmax (nm), [εmax (dm mol cm )] (methanol), 608 (201).
2
was refined to 0.54(1). The structures were refined on F using
Physical Measurements. Elemental analyses (C, H, and N)
were performed using a Perkin-Elmer 240C elemental analyzer.
IR spectra in KBr pellets (4500-500 cm- ) were recorded using
a Perkin-Elmer RXI FT-IR spectrophotometer. Electronic
spectra in methanol (1200-350 nm) were recorded in a Hitachi
U-3501 spectrophotometer. The magnetic susceptibility measure-
ments were carried out in the temperature range 2-300 K with
an applied magnetic field of 0.5 T on polycrystalline samples of
compounds 1 and 2 (with masses of 42.27 and 46.68 mg, respec-
tively) with a Quantum Design MPMS-XL-5 SQUID suscept-
ometer. Isothermal magnetizations were performed on the same
samples at 2 K with magnetic fields up to 5 T. Susceptibility data
were corrected for the sample holders previously measured using
the same conditions and for the diamagnetic contributions of
the salt as deduced by using Pascal’s constant tables.
31
Shelxl97 to R1 0.0418 and 0.0939 and wR2 0.0760 and 0.1821
for 4705, 5690 reflections with I > 2σ(I) for 1 and 2, respectively.
1
Results and Discussion
Synthesis of the Complexes. The condensation of N,N-
dimethylethylenediamine in 1:1 molar ratio with salicy-
laldehyde afforded the Schiff base, 2-[(2-dimethylamino-
ethylimino)-methyl]-phenol, which on reduction with
sodium borohydride readily produced the reduced Schiff
base, HL. HL on reaction with copper(II) chloride in
a 2:3 molar ratio yielded compound 2. Compound 1 was
produced when sodium azide (equimolar to ligand) was
also present in the reaction mixture (Scheme 1). The
deprotonated ligand reacts readily with Cu(II) to occupy
three of the four equatorial coordination sites and the
azide (in 1) or chloride (in 2) ions coordinate to the
remaining one. The coordinated azide (or chloride) and
the phenoxo oxygen of two such mononuclear units
coordinate to a free Cu(II) ion, which is present in excess
to yield the mixed bridged trinuclear species. Connecting
the two mononuclear units via Cu(II) is not surprising as
the bridging abilities of both phenoxo oxygen and azide
Crystal Data Collection and Refinement. Crystal data for the
two crystals are given in Table 1. 8292, 8419 independent data
respectively were collected with Mo KR radiation at 150 K using
the Oxford Diffraction X-Calibur CCD System. The crystals
were positioned at 50 mm from the CCD. 321 frames were
measured with a counting time of 10 s. Data analyses were carried
3
0
out with the CrysAlis program. The structures were solved
3
1
using direct methods with the Shelxs97 program. The non-
hydrogen atoms were refined with anisotropic thermal para-
meters. The hydrogen atoms bonded to carbon were included in
geometric positions and given thermal parameters equivalent to
(or chloride) groups are well documented. Of the two
chloride ions which are required to maintain the electro-
neutrality of such trinuclear complexes, one coordinates
terminally to the central Cu(II) and the other bridges the
trinuclear units to form the 1D chains (Scheme 1)
(30) CrysAlis; Oxford Diffraction Ltd.: Abingdon, U.K., 2006.
(31) Sheldrick. G. M. Shelxs97 and Shelxl97, Programs for Crystallo-
graphic solution and refinement; Acta Crystallogr. 2008 A64 112.
32) ABSPACK program for absorption corrections; Oxford Diffraction:
Abingdon, U.K., 2007.
33) (a) Mukherjee, P.; Drew, M. G. B.; G oꢀ mez-Garcı
(
IR and Electronic Spectra. A moderately strong, sharp
peak due to N-H stretching vibration at 3235 and 3208
cm for complexes 1 and 2, respectively, shows that the
(
´
a, C. J.; Ghosh, A.
-
1
Inorg. Chem. 2009, 48, 5848. (b) Tandon, S. S.; Thompson, L. K.; Manuel, M. E.;
Bridson, J. N. Inorg. Chem. 1994, 33, 5555.
imine group of the Schiff base is reduced. The reduction of

8
158 Inorganic Chemistry, Vol. 49, No. 17, 2010
Biswas et al.
the imine group isalsoveryclearly indicatedby the absence
of the strong band due to imine vibration which appears in
show a single absorption band at 612 and 608 nm for
compounds 1 and 2, respectively. The positions of these
bands are typical of d-d transitions in Cu(II) ions with a
-
1
the region 1620-1650 cm for the complexes of the
corresponding unreduced Schiff bases. The sharp peak
3
3a
34
square-pyramidal geometry.
-
1
at 2076 cm for complex 1 is due to ν(N ) suggesting the
Crystal Structures of the Complexes. Structure of
3
3
3b
end-on (μ ) bridging mode of the azide ion.
[Cu L (μ -N ) (μ-Cl)Cl] (1). The structure of 1 is shown
1
,1
3
2
1,1 3 2
n
The electronic spectra of these two compounds were
recorded in methanol solution. The electronic spectra
in Figure 1 together with the atomic numbering scheme.
The structure consists of trinuclear Cu(II) units which
are bridged by weak Cu Cl interactions to form a 1D
polymer (Figure 2a) by sharing the vertex of the trinuclear
units (Figure 2b). The two outer copper atoms Cu(1) and
Cu(2) have equivalent environments having four strong
bonds in a equatorial plane being bonded to three atoms
of the ligand together with an azide nitrogen atom. Bond
3
3 3
˚
˚
lengths from Cu(1) are 1.914(2) A to O(11), 2.014(2) A to
˚
N(19), 2.031(2) A to N(22) in the terdentate ligand, and
˚
.031(3) A to the azide N(1). Equivalent distances from
2
Cu(2) are 1.946(2) A to O(31), 1.998(2) A to N(39),
˚
˚
˚
.042(3) A to N(42), and 2.000(3) A to the azide N(4)
˚
2
(Table 2). The four donor atoms in the equatorial planes
of Cu(1) and Cu(2) are almost planar with root mean
˚
square (rms) deviations of 0.038 and 0.052 A, respec-
˚
tively, with the copper atoms 0.306(1) and 0.270(1) A
from the plane in the direction of a weakly bound chlorine
˚
atom in an axial position, namely, Cl(2) at 2.647(1) A
a
a
from Cu(2) and Cl(2 ) ( =0.5-x,-0.5þy, 1.5-z) at
˚
.539(1) A from Cu(1). This Cl(2) atom thus forms a
2
c
bridge between adjacent trinuclear units with a Cu(1 )-
c
Cl(2)-Cu(2) ( = 0.5-x, 0.5þy, 1.5-z) angle of 140.6(1)ꢀ.
In the trinuclear unit, the central copper atom Cu(3)
has a five-coordinate trigonal prismatic environment
being bonded to two azide nitrogen atoms N(1) and
N(4) which bridge to Cu(1) and Cu(2), respectively, and
two oxygen atoms O(11) and O(31) which also bridge to
Figure 1. Trinuclear structure of 1 with ellipsoids at 30% probability.
The open bonds show the weak Cu
3 3 Cl interactions.
3
Figure 2. (a) 1D polymer formed by weak Cu Cl interactions between the trinuclear units in compound1. (b) The vertex sharing 1D polymer formed by
weak Cu Cl interactions between the trinuclear units in compound 1.
3
3 3
3
3 3

Article
Inorganic Chemistry, Vol. 49, No. 17, 2010 8159
3
5
˚
Table 2. Bond Distances (A) and Angles (deg) for Complexes 1 and 2
amid have been calculated by the Addison parameter (τ)
as an index of the degree of trigonality. The value of τ is
defined as the difference between the two largest donor-
metal-donor angles divided by 60, a value that is 0 for the
ideal square pyramid and 1 for the trigonal bipyramid.
The τ values are 0.11 and 0.05 for Cu(1) and Cu(2),
respectively, indicating that the geometry around these
two copper ions is nearly square pyramidal. However, the
τ value (0.49) for Cu(3) shows that the geometry of the
central Cu(II) ion is intermediate between the two ideal
geometries.
complex 1
Cu(1)-O(11)
complex 2
Cu(1)-N(19)
1.914(2)
2.014(2)
2.031(2)
2.031(3)
2.539(1)
1.946(2)
1.998(2)
2.000(3)
2.042(3)
2.647(1)
1.993(3)
2.002(3)
2.080(2)
2.091(2)
2.222(1)
1.999(7)
2.054(8)
1.981(6)
2.310(2)
2.624(2)
2.000(6)
2.070(8)
1.982(6)
2.315(2)
2.547(2)
1.951(5)
1.942(5)
2.187(5)
2.296(4)
2.480(2)
2.500(2)
Cu(1)-N(19)
Cu(1)-N(22)
Cu(1)-N(1)
Cu(1)-N(22)
Cu(1)-O(11)
Cu(1)-Cl(1)
Cu(1)-Cl(4)
Cu(2)-N(39)
Cu(2)-N(42)
Cu(2)-O(31)
Cu(2)-Cl(2)b
Cu(2)-Cl(4)
Cu(3)-O(11)
Cu(3)-O(31)
Cu(3)-Cl(3b)
Cu(3)-Cl(3a)
Cu(3)-Cl(1)
Cu(3)-Cl(2)
a
Cu(1)-Cl(2)
Cu(2)-O(31)
Cu(2)-N(39)
Cu(2)-N(4)
Cu(2)-N(42)
Cu(2)-Cl(2)
Cu(3)-N(4)
Cu(3)-N(1)
Cu(3)-O(11
Cu(3)-O(31)
Cu(3)-Cl(1)
Structure of {[Cu L (μ-Cl) Cl] 0.46CH OH} (2). The
3
2
3
3
3
n
trinuclear structure of 2 is shown in Figure 3. As in 1, the
trinuclear units are bridged by chlorine atoms to form a
vertex sharing 1D polymer (Figure 4).
The formula of this structure is similar to that in 1 but
with chloride ions replacing azides. However, while the
geometry of the outer atoms Cu(1) and Cu(2) is similar to
that found in 1, that of the central Cu(3) is very different.
Cu(1) and Cu(2) show equivalent square planar geome-
tries being bonded to the three donor atoms of the
tridentate ligand together with a chlorine atom. Bond
O(11)-Cu(1)-N(19) 91.38(9)
O(11)-Cu(1)-N(19)
92.4(3)
163.8(3)
85.8(3)
82.6(2)
165.6(2)
95.3(2)
101.1(2)
90.5(2)
95.0(2)
103.7(1)
93.0(3)
165.2(3)
85.0(3)
83.3(2)
161.9(2)
94.1(2)
97.4(2)
94.3(2)
97.4(3)
103.7(2)
172.2(3)
O(11)-Cu(1)-N(22) 165.16(10) O(11)-Cu(1)-N(22)
N(19)-Cu(1)-N(22) 85.95(10)
N(19)-Cu(1)-N(22)
O(11)-Cu(1)-Cl(1)
158.34(11) N(19)-Cu(1)-Cl(1)
O(11)-Cu(1)-N(1)
N(19)-Cu(1)-N(1)
N(22)-Cu(1)-N(1)
O(11)-Cu(1)-Cl(2)
78.73(9)
98.66(10)
96.52(7)
97.27(8)
98.29(8)
102.93(8)
N(22)-Cu(1)-Cl(1)
O(11)-Cu(1)-Cl(4)
N(19)-Cu(1)-Cl(4)
N(22)-Cu(1)-Cl(4)
Cl(1)-Cu(1)-Cl(4)
O(31)-Cu(2)-N(39)
O(31)-Cu(2)-N(42)
a
a
˚
˚
lengths from Cu(1) are 1.981(6) A to O(11), 1.999(7) A to
˚
N(19)-Cu(1)-Cl(2)
N(22)-Cu(1)-Cl(2)
a
N(19), and 2.054(8) A to N(22) in the terdentate ligand
˚ ˚
a
N(1)-Cu(1)-Cl(2)
and 2.310(2) A to Cl(1) and from Cu(2) are 1.982(6) A to
˚
O(31)-Cu(2)-N(39) 93.07(9)
˚
O(31), 2.000(6) A to N(39), 2.070(8) A to N(42), and
O(31)-Cu(2)-N(4)
N(39)-Cu(2)-N(4)
O(31)-Cu(2)-N(42) 162.21(9)
N(39)-Cu(2)-N(42) 85.52(10)
78.31(9)
˚
.315(2) A to Cl(2) (Table 2). The four donor atoms form
2
an equatorial plane with rms deviations of 0.038 and
165.16(10) N(39)-Cu(2)-N(42)
O(31)-Cu(2)-Cl(2)
N(39)-Cu(2)-Cl(2)
N(42)-Cu(2)-Cl(2)b
O(31)-Cu(2)-Cl(4)
˚
0.010 A, respectively, around Cu(1) and Cu(2) with the
N(4)-Cu(2)-N(42)
O(31)-Cu(2)-Cl(2)
N(39)-Cu(2)-Cl(2)
N(4)-Cu(2)-Cl(2)
N(42)-Cu(2)-Cl(2)
N(4)-Cu(3)-N(1)
N(4)-Cu(3)-O(11)
N(1)-Cu(3)-O(11)
N(4) -Cu(3)-O(31)
N(1)-Cu(3)-O(31)
98.97(11)
104.15(7)
89.28(8)
104.45(7)
93.57(7)
˚
metal atoms 0.298(3) and 0.273(3) A from the plane in the
b
direction of an axial chloride ion, namely, Cl(4) which is
˚
N(39)-Cu(2)- Cl(4)b
N(42)-Cu(2)-Cl(4b)
Cl(2)-Cu(2)-Cl(4)
b
b
2
.624(2) A from Cu(1) and Cl(4 ) ( = xþ0.5, 0.5-y,
˚
zþ0.5) which is 2.547(2) A from Cu(2). As in 1, the
166.57(11) O(31)-Cu(3)-O(11)
bridging chlorine atom forms a 1D polymer in which
95.60(9)
75.63(9)
75.13(9)
95.93(10)
O(31)-Cu(3)-Cl(3b) 94.8(2)
O(11)-Cu(3)-Cl(3b) 92.7(2)
O(31)-Cu(3)-Cl(3a) 93.2(2)
O(11)-Cu(3)-Cl(3a) 93.9(2)
O(31)-Cu(3)-Cl(1)
O(11)-Cu(3)-Cl(1)
Cl(3b)-Cu(3)-Cl(1)
Cl(3a)-Cu(3)-Cl(1)
O(31)-Cu(3)-Cl(2)
O(11)-Cu(3)-Cl(2)
Cl(3b)-Cu(3)-Cl(2)
Cl(3a)-Cu(3)-Cl(2)
Cl(1)-Cu(3)-Cl(2)
d
d
the Cu(1)-Cl(4)-Cu(2 ) ( = x-0.5, 0.5-y, z-0.5)
angle is 126.3(1)ꢀ, significantly smaller than the corre-
sponding bridging angle of 140.6(1)ꢀ in 1.
O(11)-Cu(3)-O(31) 98.99(8)
97.2(2)
78.8(2)
104.9(2)
144.2(1)
79.3(2)
95.8(2)
143.4(2)
103.8(1)
111.7(1)
Just as in 1, the central copper atom Cu(3) has a five-
coordinate trigonal bipyramidal coordination sphere.
Cu(3) is bonded to two bridging oxygen atoms from the
ligand, two bridging chloride anions and a terminal
chloride anion. However while in 1, the bridging azides
are in axial positions, in 2, by contrast, it is the bridging
oxygens O(11) and O(31) that are in axial positions with
N(4) -Cu(3)-Cl(1)
N(1) -Cu(3)-Cl(1)
O(11)-Cu(3)-Cl(1)
O(31)-Cu(3)-Cl(1)
97.63(8)
95.73(8)
124.00(7)
136.99(6)
˚
bond lengths of 1.951(5), 1.942(5) A, significantly shorter
a
b
Symmetry operation: 0.5-x, y-0.5, 1.5-z for complex 1. Sym-
metry operation: 0.5þx, 0.5-y, 0.5þz for complex 2.
˚
than the distances of 2.080(2), 2.091(2) A found in 1 where
the oxygen atoms are in equatorial positions. This differ-
ence seems to be responsible for the considerable bent
structure of 1 with a Cu(1)-Cu(3)-Cu(2) angle of
Cu(1) and Cu(2), respectively, and a terminal chlorine
atom Cl(1). O(11), O(31), and Cl(1) make up the equator-
ial plane which together with Cu(3) provide a rms devia-
1
10.2(1)ꢀ compared to a quasi-linear structure of 2 where
˚
this angle is 171.3(1)ꢀ. In the equatorial plane there are
two bridging chloride anions at 2.480(2) and 2.500(2) A
tion of 0.006 A. The two axial atoms are the azide
nitrogen atoms N(1) and N(4). Bond lengths from Cu(3)
˚
˚
are 2.002(3) and 1.993(3) A to azide nitrogen atoms and
and a third chloride Cl(3) which is disordered over 2 sites,
named Cl(3a) and Cl(3b). These two alternative positions
˚
are close to the equatorial plane being 0.063(5), 0.163(5) A
˚
.080(2) and 2.091(2) A to ligand oxygen atoms and
˚
.222(1) A to Cl(1). The distortions of the coordination
2
2
from the plane of Cu(3), Cl(1), and Cl(2). The two
positions of Cl(3) are approximately equivalent as the
angles subtended at the metal by Cl(3a) with Cl(1) and
Cl(2) are 144.2(1)ꢀ and 104.9(2)ꢀ and by Cl(3b) are
polyhedra from the square pyramid to the trigonal bipyr-
(
34) (a) Costes, J.-P.; Dahan, F.; Laurent, J.-P. Inorg. Chem. 1986, 25,
4
13. (b) Kwiatkowski, M.; Kwiatkowski, E.; Olechnowicz, A.; Ho, D. M.;
Deutsch, E. Inorg. Chim. Acta 1988, 150, 65. (c) Bian, H.-D.; Xu, J.-Y.; Gu, W.;
Yan, S.-P.; Cheng, P.; Liao, D.-Z.; Jiang, Z.-H. Polyhedron 2003, 22, 2927.
103.8(2)ꢀ and 143.4(2)ꢀ, respectively. There is a methanol
(d) Ray, M. S.; Chattopadhyay, S.; Drew, M. G. B.; Figuerola, A.; Ribas, J.; Diaz,
C.; Ghosh, A. Eur. J. Inorg. Chem. 2005, 4562. (e) Sarkar, B.; Ray, M. S.; Drew,
M. G.; Figuerola, A.; Diaz, C.; Ghosh, A. Polyhedron 2006, 25, 3084.
(35) Addison, A. W.; Rao, T. N.; Reedijk, J.; Van Rijn, J.; Verschoor,
G. C. J. Chem. Soc., Dalton Trans. 1984, 1349.

8
160 Inorganic Chemistry, Vol. 49, No. 17, 2010
Biswas et al.
Figure 3. Trinuclear structure of 2 with ellipsoids at 30% probability. Atoms Cl(3a) and Cl(3b) are alternative positions with occupancies of 0.54(1) and
0.46(1), respectively, and bonds to the metal are shown as dotted lines. The weak Cu Cl interactions are shown as open bonds.
3
3 3
˚
Table 3. Hydrogen Bonding Distances (A) and Angles (deg) for the Complexes
-2
1
D-H
(A)
A
H
D
(A)
A
—D-H-A
(deg)
3
3 3
3 3 3
˚
˚
˚
(A)
complex
D-H
3 3 A
3
a
1
2
N(19)-H Cl(2) 0.91
3 3
2.78
2.40
2.62
3.345(3)
3.232(7)
3.298(6)
121
152
132
3
b
N(19)-H Cl(2) 0.91
3
3 3
c
N(39)-H Cl(4) 0.91
3 3
3
a
b
Symmetry operation: (0.5þx, 1.5-y, 0.5þz). Symmetry operation:
c
(
2
-0.5þx, 0.5-y, z-0.5). Symmetry operation: (1.5-x, -0.5þy,
.5-z).
Figure 4. 1Dpolymer formed by weak Cu3 3 3 Cl(4) interactions between
the trinuclear units in compound 2.
molecule hydrogen bonded to Cl(3b) with dimensions
˚
˚
O-H Cl 129ꢀ, O Cl 3.23(3) A, and H Cl 2.62 A.
3
3 3
3 3 3
3 3 3
The solvent molecule was refined with an equivalent
occupancy to the chloride to which it was attached. As
in 1, the τ values (0.03 and 0.05 for Cu(1) and Cu(2),
respectively) indicate a nearly regular square pyramidal
geometry for the two terminal Cu(II) ions but a consider-
able distortion (τ = 0.47(av.)) toward trigonal bipyramid
for Cu(3). The Cu1 Cu3 and Cu2 Cu3 distances in 1
are 3.117 A and 3.128 A, respectively. The same distances
˚
in 2 are 3.053 A and 3.083 A. The distances between the
two terminal copper atoms are 5.12 A and 6.12 A for the
complexes 1 and 2, respectively.
Hydrogen Bonding. In the extended structures of 1 and
3
3 3
3 3 3
˚
˚
˚
˚
˚
Figure 5. Hexameric macrocycle of 1; carbon and hydrogen atoms
except H19 have been excluded for clarity. Color code: Cu = light blue,
N = dark blue, O = red, Cl = green.
2
, a self-assembled two-dimensional (2D) framework is
molecules as shown in Figure 6. In complex 2, the amine
hydrogen atom N(19)-H forms an intrachain H-bond
with chloride ion Cl(2) (-0.5þx, 0.5-y, z-0.5) whereas
N(39)-H involves interchain H-bonding with Cl(4) (1.5-x,
formed by hydrogen-bonding interactions (Table 3). In
complex 1, the amine hydrogen atom N(19)-H forms a
hydrogen bond with chloride ion Cl(2) (0.5þx, 1.5-y,
˚
˚
0
.5þz) of a neighboring chain with dimensions 3.345(3)
-0.5þy, 2.5-z) with dimensions 3.298(7) A, 2.62 A and
˚
˚
˚ ˚
132ꢀ and 3.228(8) A, 2.62 A and 129ꢀ for N Cl, H Cl
3 3 3 3 3 3
A, 2.78 A, 121ꢀ for N Cl, H Cl, and N-H Cl,
3
3 3
3 3 3
3 3 3
respectively (Figure 5). These hydrogen-bonding intera-
ctions lead to the formation of a honeycomb-like 2D
network with macrocyclic cavities involving six trinuclear
and N-H Cl, respectively, (Figures S1 and S2).
Magnetic Properties. The thermal variation of the
molar magnetic susceptibility per copper trinuclear unit
3
3 3

Article
Inorganic Chemistry, Vol. 49, No. 17, 2010 8161
Figure 8. Isothermal magnetizationof compounds 1 (solid circles) and 2
(empty circles) at 2 K. Solid and dashed lines are the fit to a Brillouin
function for an S = 1/2 ion for 1 and 2, respectively.
coupling, only effective at very low temperatures, that
connects the S = 1/2 spin ground state of each Cu(II)
trimer resulting in a further decrease of the magnetic
moment at very low temperatures.
From these data and the molecular structure of compound
which contains chains of trimers with weak Cu-Cl-Cu
intertrimer interactions, we have fitted the magnetic proper-
1
Figure 6. Supramolecular network in the lattice of 1; carbon and
hydrogen atoms except H19 have been excluded for clarity. Color code:
Cu = light blue, N = dark blue, O = red, Cl = green.
ties to a simple symmetrical Cu(II) S = 1/2 linear trimer
3
model (the Hamiltonian is written as H = -JSiS ):
iþ1
2
2
Ng β 1 þ expðxÞ þ 10 expð3x=2Þ
χtrim
¼
4
kT 1 þ expðxÞ þ 2 expð3x=2Þ
with x ¼ J=kT
where J is the intratrimer coupling constant. The weak
intertrimer coupling arising from the long Cu-Cl-Cu
intertrimer bridges is reproduced with the molecular field
3
6
approximation:
χtrim
χ ¼
,
2
2
1
- ð2zj=Ng β Þχ
trim
where χtrim is the susceptibility expression for the symme-
trical trinuclear unit (see above) and zj is the product of
the number of neighboring trinuclear units (z) times the
intertrimer coupling constant (j).
m
Figure 7. Thermal variation of the χ T product for compound 1. Inset
shows the low temperature region. Solid lines represent the best fit to the
model (see text).
times the temperature (χ T) for compound 1 shows at
This simple model reproduces very satisfactorily the
magnetic properties of compound 1 in the whole tem-
perature range (solid line in Figure 7) with the following
m
-
1
room temperature a value of about 1.0 emu K mol
(Figure 7). This value is slightly lower than expected for
three isolated Cu(II) S = 1/2 ions (1.125 emu K mol for
-
1
-1
set of parameters: g = 2.136(3), J = -93.9(3) cm , and
-
1
g = 2.0). When cooling down the sample, the χ T product
zj = -0.90(3) cm (z = 2 in this case, since each trimer is
connected to only two neighboring trimers). Note that
although the two intratrimer bridges are not identical,
they are very similar and, to reduce the number of
adjustable parameters, they have been assumed to be
equivalent. The very satisfactory fit obtained with the
model confirms that this assumption is acceptable.
A further confirmation of the antiferromagnetic cou-
pling present in this compound can be obtained from the
isothermal magnetization at 2 K that shows a saturation
m
-
1
decreases to reach a value of about 0.4 emu K mol
below about 30 K that remains constant down to about
K and decreases again below this temperature (inset in
5
Figure 7). This behavior indicates the presence of pre-
dominant antiferromagnetic interactions between the
Cu(II) ions. In fact, the presence of a plateau with a value
-
1
of about 0.4 emu K mol is expected for an antiferro-
magnetically coupled Cu(II) linear trinuclear complex
where the central spin is coupled with the two terminal
ones, but there is no coupling between the terminal ones.
As a result of the odd number of Cu(II) ions, the resulting
spin ground state corresponds to an S = 1/2 ion, as
clearly shown by the plateau that can be observed at low
temperatures. The decrease observed at very low tem-
peratures indicates that there in an additional intertrimer
value of about 1.0 μ and a behavior that can be very well
B
reproduced with a Brillouin function for an isolated S = 1/
2 ion although with a reduced g value given the intertrimer
antiferromagnetic interactions present at 2 K (Figure 8).
(36) O’Connor, C. J. Prog. Inorg. Chem. 1982, 29, 203.

8
162 Inorganic Chemistry, Vol. 49, No. 17, 2010
Biswas et al.
Table 4. Magnetic and Structural Parameters of Compound 1 and of All the
Known Cu(II) Dimers Presenting a Mixed-Double μ1,1-N
3
and Oxo Bridge
-1
CCDC code
J (cm ) Cu-O-Cu -OR Cu-N-Cu ref.
CAWFEL
FAMKAF
FIFWEW
GIPVEG
HONKAX
JOGBUC
LIBPAO
ROGPOS
SATYOB
SATZES
-200
-86.5
-161
-388
-119
-482
-188.6
-132.4
-278
-408
102.5
98.7
100.5
106.0
102.1
98.4
101.3
99.2
99.4
100.4
102.5
101.5
OH
95.7
100.0
99.7
100.7
102.9
104.6
98.3
6
7
8
9
10
11
22
12
13
13
OPh
OPh
OPh
OPh
OPh
OPh
OPh
OPh
OPh
OPh
OPh
99.9
106.1
102.8
101.2
103.2
COMPOUND 1 -93.9
93.9
this work
-
m
Figure 9. Thermal variation of the χ T product for compound 2. Inset
shows the low temperature region. Solid lines represent the best fit to the
model (see text).
an isolated S = 1/2 ion although with a reduced g value
given the intertrimer antiferromagnetic interactions pre-
sent at 2 K.
The thermal variation of the molar magnetic suscept-
ibility per Cu(II) trinuclear unit times the temperature
Compound 1 is the first example of a chloro bridged 1D
chain of Cu(II) trimers containing mixed μ1,1-N and oxo
bridges, and, therefore, its magnetic properties cannot be
compared with other similar complexes. Nevertheless,
there are some Cu(II) dimers containing these kind of
mixed double bridges. Thus, the CCDC database
(updated Nov. 2009) shows up to 14 structurally char-
3
(
of about 1.1 emu K mol , very close to expected for three
χ T) for compound 2 shows at room temperature a value
m
-
1
-
1
S = 1/2 Cu(II) non-interacting ions (1.125 emu K mol
for g = 2). When the temperature is lowered, the χ T
value decreases to reach a value of about 0.45 emu K
m
-
1
mol at about 15 K. Below about 15 K, χ T remains
acterized copper dimers presenting mixed μ1,1-N and oxo
m
3
constant down to about 5 K, and then it shows an
additional decrease to reach a value of 0.36 emu K mol
bridges although only 10 have been also magnetically
characterized (see Table 4). All these compounds show
quite strong antiferromagnetic couplings with J values
(normalized for a spin Hamiltonian H = -JS S ) in the
-
1
at 2 K (Figure 9). This behavior is very similar to that
shown by compound 1 and, as confirmed by the structural
data, also indicates the presence of antiferromagnetically
coupled Cu(II) linear trimers where the central spin is
coupled with the two terminal ones, but there is no
coupling between the terminal ones. As in compound 1,
the odd number of Cu(II) ions in the trimer results in a
ground spin state S = 1/2 that is responsible of the
plateau observed at low temperatures. The decrease of
χmT at very low temperatures also indicates that there is
an additional intertrimer coupling.
1
2
-
1
range -86 to -482 cm (see Table 4). Unfortunately,
there is no direct relationship between the J values and the
Cu-O-Cu nor the Cu-N-Cu bond angles in these
compounds. This fact can be easily explained from pre-
4
a,37-40
vious magneto structural correlations
tical calculations
and theore-
for oxo-bridged complexes (either
4
d,5
hydroxo, alkoxo, or phenoxo) showing that, although the
main parameter governing the magnetic coupling is the
Cu-O-Cu angle, there are some others that need to be
2
2
As already mentioned, the structure of compound 2 is
very similar to that of compound 1 both containing chains
of Cu(II) trimers connected through long Cu-Cl-Cu
bridges. The only difference involves the intratrimer
considered. These correlations establish that for the
phenoxo bridges present in compound 1 with Cu-O-Cu
bond angles of 102.53(10)ꢀ and 101.54(9)ꢀ the magnetic
-
1
coupling should be about 400 cm , well above the
-
1
bridges: a μ1,1-N and a O atom in 1 versus a Cl and an
experimental value (ca. -94 cm ). There are two expla-
nations for the lower experimental values. On the one
hand, although the geometry of the terminal Cu(II) ions is
close to the square pyramid (the Addison parameters, τ,
are 0.11 and 0.05 for Cu(1) and Cu(2), respectively, see
3
O atom in 2. Since both kinds of intratrimer bridges are
expected to generate antiferromagnetic couplings (see
below), we have fitted the magnetic properties of com-
pound 2 to the same simple symmetrical Cu(II) S = 1/2
linear trimer model used for compound 1 (see above).
This simple model reproduces very satisfactorily the
magnetic properties of compound 2 in the whole tem-
perature range (solid line in Figure 9) with the following
3
5
above), the geometry of the central Cu(II) ion is inter-
mediate between the trigonal bipyramid and the square
pyramid (τ = 0.49 for Cu(3), see above). This fact reduces
significantly the orbital overlap between the central and
the terminal Cu(II) ions and, therefore, the magnetic
-
1
set of parameters: g = 2.073(7), J = -44.9(4) cm , and
0
-1
zJ = -1.26(6) cm , with z the number of nearest
neighbors of each trimer (z = 2, as in 1). The Hamiltonian
coupling. On the other hand, the μ1,1-N bridge is well-
3
known to give rise to ferromagnetic coupling for low Cu-
is also written as H = -JSiS . Note that, as observed in
N-Cu angles and antiferromagnetic coupling for large
iþ1
33,41
compound 1, although the two intratrimer bridges are not
identical, they are very similar and have been assumed to
be equivalent.
angles, with a crossing angle of about 104ꢀ.
In compound
(
(
37) Hodgson, D. J. Prog. Inorg. Chem. 1975, 19, 173.
38) Merz, L.; Haase, W. J. Chem. Soc., Dalton Trans. 1980, 875.
As expected, the isothermal magnetization of com-
pound 2 at 2 K shows very similar behavior to that of
compound 1 with a saturation value of about 1.0 μB
(Figure 8). As in compound 1, the isothermal magnetiza-
tion can be well reproduced with a Brillouin function for
(39) Handa, M.; Koga, N.; Kida, S. Bull. Chem. Soc. Jpn. 1988, 61, 3853.
40) Walz, L.; Paulus, H.; Haase, W. J. Chem. Soc., Dalton Trans. 1985,
13.
41) Ruiz, E.; Cano, J.; Alvarez, S.; Alemany, P. J. Am. Chem. Soc. 1998,
120, 11122.
(
9
(

Article
Inorganic Chemistry, Vol. 49, No. 17, 2010 8163
Table 5. Magnetic and Structural Parameters of Compound 2 and of All the
Known Cu(II) Dimers and Trimers Presenting a Mixed-Double Chlorine and Oxo
Bridge
the lowest Cu-Cl-Cu angle and also the lowest J value
and by compound 2 that also presents very low Cu-
Cl-Cu angles, in agreement with the low J value found in
this compound.
-
1
CCDC code
PETSOX
J (cm ) Cu-O-Cu -OR Cu-Cl-Cu
ref.
-291
162
-335
-443
-85
-348
-374
-104
-177
103.5
106.5
111.4
113.4
117.3
112.8
116.2
109.5
112.4
103.6
101.8
OPh
OPh
OPh
OPh
OPh
OR
OPh
OPh
OPh
OPh
OPh
85.6
78.2
89.6
86.1
78.1
87.7
84.8
82.7
81.8
79.5
79.1
14
Conclusions
-
FESJIW
FOGGIR
IBUJOF
JEDFUU
OBOWUY
UFATEB
WAHSOO
15
9
The use of the tridentate reduced Schiff-base ligand HL
(2-[(2-dimethylamino-ethylamino)-methyl]-phenol) with
17
18
19
21
21
Cu(II) and potentitally bridging ligands as chloride or azide
anions has afforded two related trinuclear Cu(II) complexes.
These two complexes confirm once again the ability of
tridentate Schiff base ligands to chelate and bridge Cu(II)
ions while leaving some coordination positions vacant that
can be easily occupied by diverse bridging or terminal
ligands. In the title compounds the use of azide and chloride
anions has led to the formation of two novel chloro-bridged
COMPOUND 2 -44.9
44.9
this work
-
1
1
the Cu-N-Cu bond angles are 101.25(12)ꢀ and
03.18(11)ꢀ and, therefore, they are expected to originate
moderate to strong ferromagnetic couplings of about 100
1D chains of trinuclear units presenting double mixed-
-
1
cm that should partially cancel the antiferromagnetic
coupling expected for the phenoxo bridge, resulting in a
reduction of the antiferromagnetic coupling, as experi-
mentally observed.
bridges (μ1,1-N and O in 1 and Cl and O in 2). The originality
3
of both complexes is clearly evidenced by the fact that such
angular trinuclear Cu(II) complexes with mixed-double
μ-1,1N and oxo or chloro and oxo bridges is very rare, and
3
For compound 2 the situation is quite similar since
there is only one known example of trimeric Cu(II)
complex with double-mixed chloride and oxo bridges
joining of such trinuclear units with chloride ion to result in
1D chains is unprecedented. The magnetic properties of both
1
4
compounds are very similar: both complexes present mode-
rate antiferromagnetic couplings that can be very well ratio-
nalized from the structural parameters of the mixed-double
bridges. The use of similar Schiff base or reduced Schiff base
ligands combined with different halide and pseudo halide
ligandsisexpectedto lead to novelmixedbridged compounds
with original structures. The magneticpropertiesof a series of
such complexes would help to draw a magneto-structural
correlation. This work is underway.
and, therefore, we cannot establish any magneto-struc-
tural correlation. Nevertheless, a search in the CCDC
database (updated Nov 2009) shows up to 20 Cu(II)
dimers presenting similar double-mixed chloride and
oxo bridges. Among these, only seven have been structu-
rally and magnetically characterized (see Table 5). In all
these complexes the magnetic coupling is antiferromag-
netic and quite strong, with J values ranging from -85 to
-
1
-
-
443 cm (normalized for a spin Hamiltonian H =
JS S , Table 5). Although compound 2 presents the
1
2
Acknowledgment. We thank CSIR, Government of India
lowest antiferromagnetic coupling in this table, this fact
can also be explained by two reasons: (1) The central
Cu(II) ion presents a trigonal bipyramidal geometry
whereas the two external Cu(II) ions present quite regular
square pyramidal geometries. Thus, the Addison para-
meters are 0.03 and 0.05 for Cu(1) and Cu(2), respectively
whereas τ = 0.47(av.) for the central Cu(3). (2) A second
fact is the acute Cu-Cl-Cu angle observed in compound
[
0
(
Junior Research Fellowship to A.B., Sanction No.
9/028(0717)/2008-EMR-I], the European Union
MAGMANet network of excellence), the Spanish Min-
isterio de Educaci oꢀ n y Ciencia (Projects MAT2007-61584
and Consolider-Ingenio 2010 CSD 2007-00010 in Molec-
ular Nanoscience) and the Generalitat Valenciana
(
PROMETEO/2009/095 project). We also thank EPSRC
and the University of Reading for funds for the X-Calibur
system.
2
(both angles are below 80ꢀ). Although we cannot
establish a direct magneto-structural correlation between
the Cu-Cl-Cu angle and the magnetic coupling in these
Cu(II) dimers, the clear trend is that as this angle de-
creases, the magnetic coupling becomes smaller. This fact
is further supported by compound IBUJOF, that presents
Supporting Information Available: Further details are given in
Figures S1 and S2, and crystallographic data is given in CIF
format. This material is available free of charge via the Internet
at http://pubs.acs.org.