Ferromagnetic coupling in a unique Cu(II) metallacyclophane with functionalized diazamesocyclic ligands formed by Cu(II)-directed self-assembly: Magneto-structural correlations for dichloro-bridged Cu(II) dinuclear complexes

Article abstract of DOI:10.1039/b110465a

Two new di-μ-Cl dinuclear Cu^II complexes [Cu(HL¹)Cl₂]₂(ClO₄)₂ (1) and [Cu₂(L²)₂Cl₂](ClO₄) ₂ (2) with the pyridyl-functionalized diazamesocyclic ligands 1,5-bis(pyridin-4-ylmethyl)-1,5-diazacyclooctane (L¹) and 1-(pyridin-2-ylmethyl)-1,4-diazacycloheptane (L²) have been synthesized and structurally characterized by single crystal X-ray diffraction. Complex 1 is a unique paramagnetic Cu^II metallamacrocycle (ca. 14.1 × 3.5 A ²) directly self-assembled by metal ions and the organic spacer under strongly acidic conditions. The magnetic properties of both complexes have been investigated by variable-temperature magnetic susceptibility measurements. Although complexes 1 and 2 have almost the same geometrical parameters for Cu^II, their magnetic parameters vary from ferromagnetic for 1 to antiferromagnetic for 2. The magneto-structural correlation of such complexes has been further developed.

Full text of DOI:10.1039/b110465a

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Ferromagnetic coupling in a unique Cu(II) metallacyclophane with
functionalized diazamesocyclic ligands formed by Cu(II)-directed
self-assembly: magneto-structural correlations for dichloro-bridged
Cu(II) dinuclear complexes
Miao Du,a Ya-Mei Guo,a Xian-He Bu,*a Joan Ribasb and Montserrat Monfortb
a
Department of Chemistry, Nankai University, Tianjin 300071, P. R. China.
E-mail:buxh@nankai.edu.cn; Fax: þ86-22-23502458
b
´ `
Departament de Quımica Inorganica, Universitat de Barcelona, Diagonal 647, 08028
Barcelona, Spain
Received (in Montpellier, France) 15th November 2001, Accepted 14th January 2002
First published as an Advance Article on the web
1
2
II
Two new di-m-Cl dinuclear Cu complexes [Cu(HL )Cl2]2(ClO4)2 (1) and [Cu2(L )2Cl2](ClO4)2 (2) withthe
pyridyl-functionalized diazamesocyclic ligands 1,5-bis(pyridin-4-ylmethyl)-1,5-diazacyclooctane (L1) and
1-(pyridin-2-ylmethyl)-1,4-diazacycloheptane (L2) have been synthesized and structurally characterized by
+
2
II
single crystal X-ray diffraction. Complex 1 is a unique paramagnetic Cu metallamacrocycle (ca. 14.1 Â 3.5 A )
directly self-assembled by metal ions and the organic spacer under strongly acidic conditions. The magnetic
properties of bothcomplexes have been investigated by variable-temperature magnetic susceptibility
II
measurements. Although complexes 1 and 2 have almost the same geometrical parameters for Cu , their
magnetic parameters vary from ferromagnetic for 1 to antiferromagnetic for 2. The magneto-structural
correlation of such complexes has been further developed.
Particular interest has been directed towards the study of
II
dinuclear Cu complexes to elucidate the spin coupling
[Cu(HL1)Cl2]2(ClO4)2 (1) and [Cu2(L2)2Cl2](ClO4)2 (2) with
new pyridyl-functionalized diazamesocyclic ligands, 1,5-bis-
(pyridin-4-ylmethyl)-1,5-diazacyclooctane (L1) and 1-(pyridin-
2-ylmethyl)-1,4-diazacycloheptane (L2). To our knowledge, 1
between paramagnetic metal centers, bothfrom structural and
theoretical points of view, especially for the monoatomic
II
II
bridged (suchas m-OH, OCH3 , S and Cl) Cu dimers, since
is the first structurally characterized water-soluble Cu mac-
they provide the simplest case of magnetic interaction invol-
ving only two unpaired electrons.1–4 Concurrent with this has
been the development of the magneto-structural correlation in
the [Cu(m-Cl)2Cu] dimeric motif, displaying a wealthof
structures witha variety of Cu–Cl lengths and Cu–Cl–Cu
angles depending on the coordinated ligands and also on the
counterions.5–8 However, no simple magneto-structural rela-
tionship relating the value of the singlet–triplet gap (J) to th e
Cu–Cl–Cu angle or CuÁ Á ÁCu distance, for example, has been
established, especially for the asymmetric [Cu(m-Cl)2Cu]
dimers. Hatfield et al. have shown that J in suchcompounds
varies in a regular way with the quotient of the Cu–Cl–Cu
bridging angle (f) and the long, out-of-plane Cu–Cl bond
length( R).9
rometallacycle assembled in strong acidity conditions. It is
interesting that although 1 and 2 have almost the same quo-
tient values of f=R, their magnetic parameters differ from
ferromagnetic to antiferromagnetic. This means that Hatfield’s
rule seems to be less general in this case, and other factors
should also be taken into consideration. The magneto-
structural correlation of such complexes has been further
developed.
Mesocyclic diamines, which have two nitrogen donors as
bidentate chelating ligands and offer the potential for further
functionalization, are the smallest members of the family of
cyclic polyamines.10,11 1,5-Diazacyclooctane (DACO) and
1,4-diazacycloheptane (DACH) are the most typical diaza-
mesocyclic ligands. The former always takes the unique
‘‘boat=chair’’ configuration when coordinated to metal ions,
while the latter can take on different forms. In our efforts to
systematically investigate the control of the structures and
magnetic properties as well as the coordination chemistry of
diazamesocyclic ligands by modifying their backbone, we have
Results and discussion
Syntheses and general characterization
The doubly substituted ligand L1 was prepared by using an
excess of 4-chloromethylpyridine, and an excess of DACH was
used to obtain the monoalkylated product L2. Acid-free
ligands were obtained as oils so they were converted into the
HCl salts to get purified crystalline solids. The yields for both
ligands were over 50% and all the analytical data were in good
agreement with the theoretical requirements.
II
reported a variety of Cu complexes withdifferent coordina-
tion modes and magnetic properties by altering the donor
pendants.12–14 In this contribution, we report the syntheses
II
and crystal structures of two chloro-bridged Cu dimers
DOI: 10.1039/b110465a
New J. Chem., 2002, 26, 645–650
645
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+
Table 1 Selected bond distances (A) and angles (ꢁ) for complexes 1
and 2
The syntheses of the complexes 1 and 2 were achieved by the
reactions of the protonated ligand (L1Á4HCl) or the corres-
ponding acid-free ligand (L2, neutralized withKOH aqueous
solution prior to complexation) withCu(ClO 4)2Á6H2O. The IR
spectra for bothcomplexes show absorption bands resulting
from the skeletal vibrations of the aromatic rings in the 1400–
1600 cmÀ1 region. For 1, there is a weak but sharp band at
3066 cmÀ1 due to the N–ÀH stretching of the protonated
ligand.15 The bands of ClO4 appear at ꢀ1100 and 623 cmÀ1
for 1, and an interesting feature of the spectrum ofÀ2 is the
occurrence of highly split nCl–O stretches of the ClO4 ions at
ꢀ1100 cmÀ1, which provides good evidence of their involve-
ment in the formation of hydrogen bonds.
Complex 1
Cu(1)–N(1)
Cu(1)–Cl(1)
Cu(1)–Cl(2A)
2.023(6) Cu(1)–N(4)
2.266(3) Cu(1)–Cl(2)
2.918(3)
1.995(6)
2.292(2)
Cl(1)–Cu(1)–Cl(2)
N(4)–Cu(1)–Cl(1)
N(4)–Cu(1)–Cl(2)
Cu(1)–Cl(2)–Cu(1A)
174.27(9)
N(4)–Cu(1)–N(1)
N(1)–Cu(1)–Cl(1)
N(1)–Cu(1)–Cl(2)
173.5(3)
90.4(2)
92.0(2)
89.2(2)
87.8(2)
94.7(6)
Complex 2
Cu(1)–N(1)
Cu(1)–N(3)
Cu(1)–Cl(2)
Cu(2)–N(6)
Cu(2)–Cl(1)
N(2)–Cu(1)–N(3)
N(2)–Cu(1)–N(1)
N(2)–Cu(1)–Cl(2)
N(4)–Cu(2)–N(6)
N(6)–Cu(2)–N(5)
N(6)–Cu(2)–Cl(1)
Cu(1)–Cl(1)–Cu(2)
2.020(7) Cu(1)–N(2)
1.996(7) Cu(1)–Cl(1)
2.273(3) Cu(2)–N(4)
2.001(6) Cu(2)–N(5)
2.279(2) Cu(2)–Cl(2)
1.991(7)
2.624(2)
1.986(7)
2.022(7)
2.656(3)
166.9(2)
82.3(3)
98.6(2)
79.1(3)
97.6(2)
169.8(2)
86.11(8)
Description of crystal structures
158.9(3)
N(1)–Cu(1)–Cl(2)
2þ
À
In complex 1, a [Cu(HL1)Cl2]2 cation unit and two ClO4
79.8(3)
96.3(3)
155.5(3)
82.4(3)
97.8(2)
86.76(8)
N(3)–Cu(1)–N(1)
N(3)–Cu(1)–Cl(2)
N(4)–Cu(2)–N(5)
N(4)–Cu(2)–Cl(1)
N(5)–Cu(2)–Cl(1)
Cu(1)–Cl(2)–Cu(2)
ions were found to exist due to the mono-protonation of the
ligand L1. In the complex cation [Fig. 1(a)], resulting from the
pairing of two mononuclear units related by a crystallographic
II
center of symmetry, the two Cu ions are bridged equivalently
by two ClÀ anions in a very weak coordination witha Cu–Cl
+
II
lengthof 2.918(3) A. EachCu is penta-coordinated, in an
approximately ideal square pyramid polyhedron reflected by
the t value (0.01 here) defined by Addison et al. (t ¼ 0 for an
the ‘‘symmetry interaction’’ model to construct metal-based
17
ideal square pyramid and 1 for an ideal trigonal bipyramid)16
and deviates by only 0.107 A from the basal plane defined by
supramolecules withspecial topology.
Another interesting
point is the stacking pattern of this assembly in the solid state
+
N(1)–N(4)–Cl(1)–Cl(2) towards the apical Cl(2A). The axial
Cu–Cl bond length is significantly longer than that of the Cu–
Cl bond in the basal plane (Table 1). Also, it is longer than
the normal values in similar dimeric complexes with C4v
because the cation parts of the metallamacrocycle are stacked
along the a axis about 5.9 A apart, resulting in long, channel-
+
like cavities [Fig. 1(b)]. This interesting arrangement may find
application in solid-state catalysis, especially in cases where
the exact dimensions of the absorbing channels are of
importance.18
13
II
coordination geometry of Cu . The Cu–Cl–Cu bridging
angle is 94.7(6)ꢁ and the intramolecular CuÁ Á ÁCu separation is
+
Complex 2 consists of aÀdichloro-bridged [Cu2(L2)2Cl2]2þ
3.856 A. The shortest intermolecular CuÁ Á ÁCu distance is 8.916
+
II
dimeric unit and two ClO4 ions. BothCu centers are also
penta-coordinated, in a distorted square pyramid geometry
A and the DACO ring takes the normal ‘‘boat=chair’’ con-
figuration.12 1 is a unique dinuclear water-soluble Cu metal-
II
+
2
II
lamacrocycle (ca. 14.1 Â 3.5 A ) directly self-assembled by Cu
with t values of 0.13 for Cu(1) and 0.24 for Cu(2). Cu(1) is
0.234 A above the mean basal plane defined by N(1)–N(2)–
N(3)–Cl(2) toward the apical Cl(1), and Cu(2) is 0.191 A
+
and the new organic spacer L1, and is also a nice example for
+
above the N(4)–N(5)–N(6)–Cl(1) mean plane toward Cl(2).
The Cu–Cl bond lengths in the axial position are significantly
longer than those in the basal plane (Table 1) and the Cu–
Cl–Cu bridging angles are 86.76(8) and 86.11(8)ꢁ. Th
e
+
intramolecular CuÁ Á ÁCu separation is 3.376 A, and the
shortest intermolecular CuÁ Á ÁCu lengthin the unit cell is 7.772
+
A. The DACH ring takes the normal boat configuration.
One feature of this structure is that each [Cu2(L2)2Cl2]2þ
À
unit carries one ClO4 hydrogen-bonded to the non-
substituted nitrogen atoms of the diazamesocycle to form a
macrocycle-like ring system including a N–HÁ Á ÁOÁ Á ÁH–N
bridge (Fig. 2), reflected by the highly split bands for ClO4À in
the IR spectrum.
Electronic and EPR spectra
The UV-Vis spectrum of complex 1 (light green) in water
solution shows a quite weak absorption maximum at 804 nm,
which indicates that the coordination geometry changes to the
planar form.19 For 2 (dark blue), a broad and intense band
centered at 645 nm was found in methanol solution, and this
II
spectral feature is typical of penta-coordinated Cu complexes
withdistorted square-pyramidal geometry, wihchgenerally
exhibits a band in the 550–660 nm range (dxz , dyz ! dx2Ày2).20
The relative higher lmax value suggests the coordination geo-
II
metry of Cu in 2 is distorted from square-pyramidal (toward
trigonal bipyramid),20 which is consistent with the degree
of distortion found in the X-ray structural analysis. In addi-
tion, the electronic spectra of both complexes display charac-
teristic absorptions at 200–300 nm assigned to ligand p ! p*
transitions.
Fig. 1 (a) ORTEP structure of [Cu2(HL1)Cl2]2þ unit in complex 1
with50% probability thermal ellipsoids. (b) Stacking diagram of 1 in
the unit cell showing the channel-like cavities along the a direction.
646
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Fig. 2 ORTEP structure of the {[Cu2(L1)2Cl2](ClO4)}þ ring system
showing the hydrogen bonds in complex 2 with50% probability
thermal ellipsoids.
The X-band EPR spectra of both complexes were registered
in the solid state at different temperatures (from room tem-
perature to 4 K). For 1, at all the temperatures, the spectra
show isotropic bands with gav ¼ 2.14. The triplet did not
appear even at the lowest temperature and it is normal for
II
these kinds of ferromagnetic Cu complexes, probably owing
to exchange narrowing. No absorption is observed at half-field
(Dms ¼ 2, g ¼ 4) indicating a small zero-field splitting effect.21
For 2, at all temperatures there is a typical pattern from axial
distortion with g ¼ 2.15 and g ¼ 2.06, and there is only a
Fig. 3 Magnetic coupling diagram of (a) 1; (b) 2. The solid lines
represent the best fit from the Bleaney–Bowers expression.
k
?
small variation with the temperature. This pattern is typical for
a square-pyramidal geometry, withteh unpaired electron
mainly located in the dx2Ày2 orbital.
A number of investigations have been carried out concern-
ing the magneto-structural correlation and different mag-
Magnetic properties
II
netic behaviors have been found in chloro-bridged Cu
The magnetic properties of 1 and 2 in the form of wMT vs. T
plots are shown in Fig. 3 (wM is the magnetic susceptibility per
dimers.5–9,13,14,23–28 To date, three types5 of pyramidal
arrangements in [Cu(m-Cl)2Cu] units are found in the litera-
ture. The two complexes studied in this paper belong to the
II
two Cu ions). For 1, the value of wMT at room temperature
is 0.85 cm3 K molÀ1, continuously increasing to a maximum
of 1.06 cm3 K molÀ1 at 5.6 K. It then decreases to 1.01 cm3 K
molÀ1 at 2 K. This shape of the curve is typical of a moderate
same type (I): square pyramids sharing one base-to-apex edge
II
but withparallel basal planes [Scheme 1(a)]. SuchCu
dimers
have been well studied, with the aim to correlate their struc-
tures and magnetic properties, but no simple magneto-struc-
tural relationship relating the value of J to the Cu–Cl–Cu
angle or CuÁ Á ÁCu distance, for example, has been established.
Hatfield et al.9 have shown that the singlet–triplet gap in such
compounds varies in a regular way withthe quotient f=R as
described above. It was found that for values of this quotient
lower than 32.6 and higher than 34.8, the exchange interaction
is antiferromagnetic. For values falling between these limits it
is ferromagnetic. In the case of 1 and 2 having similar cores,
the magnetic properties are widely divergent. 1 is ferromag-
netic while 2 being antiferromagnetic although the parameter
f=R is almost the same [32.43 for 1 and 32.74 (average) for 2].
This indicates that Hatfield’s rule seems to be less general for
our new case, and other structural factors should be taken into
consideration.
II
ferromagnetic interaction between Cu ions. The decrease at
lower temperatures is due to intermolecular interactions
and=or zero-field splitting effects. For 2, the value of wMT at
298 K is 0.84 cm3 K molÀ1, corresponding to two independent
II
uncoupled Cu ions. The wMT value decreases monotonically
down to 2 K, attaining a value of 0.53 cm3 K molÀ1. This
feature is characteristic of the presence of a weak intramole-
II
cular antiferromagnetic interaction between Cu ions. Very
good fits can be obtained through a simple Bleaney–Bowers
II
expression for a Cu dimer using the hamiltonian H ¼
ÀJSS1ÁS2 ,22 and the best-fit parameters are J ¼ 10.70 cmÀ1
,
J0 ¼ À0.26 cmÀ1, g ¼ 2.12 and R ¼ 3.9 Â 10À6 for 1, and
J ¼ À1.95 cmÀ1, g ¼ 2.11 and R ¼ 2.2 Â 10À5 for 2 (all symbols
have their usual meanings). For 1, a new parameter J0 indi-
cating intermolecular interactions must be introduced in the
formula, according to the theory reported by Kahn,3 in order
to take into account the decrease of wMT at very low
temperature.
Actually, in the case of complexes 1 and 2, the values of the
quotient f=R are near 32.6, and thus near the limit between
ferro and antiferromagnetic interactions. The main difference
New J. Chem., 2002, 26, 645–650
647

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(and the origin of the magnetic behavior) is the characteristics
II
of the magnetic orbitals: in 2 the geometry of Cu is not a
perfect square-pyramid, thus the magnetic orbital is a mixture
of dx2Ày2 and dz2 , mainly located in the equatorial plane
(dx2Ày2) but withnon-zero spin density on its axial position.
This feature (participation of the dz2 orbital) creates a small
II
overlap between the two Cu magnetic orbitals, giving the
antiferromagnetic coupling. On the contrary, in 1, the geo-
II
metry of Cu is almost a perfect square-pyramid. Thus, the
magnetic orbital is purely dx2Ày2 , without any (or with only
negligible) delocalization in dz2 . Consequently, there is no
overlap between magnetic orbitals and the behavior must be
ferromagnetic [Scheme 1(b)].
Another important point, according to the literature, is the
dihedral angle between two Cl–Cu–Cl planes (planarity or
deviation of the planarity for Cl–Cu–Cl–Cu). The bending of
the dihedral angle d causes a shortening of the CuÁ Á ÁCu dis-
tance. A very crude monoelectronic reasoning would lead one
to expect an enhancement of bonding and antibonding char-
acter of single occupied MOs, leading to an increase of the
antiferromagnetic coupling. However, variational ab initio MO
calculations have shown that these bent structures display
ferromagnetic properties.29 Moreover, the relationship
between the S–T gap and the d angle shows that the non-
planarity of the bridge increases the ferromagnetic coupling.
Scheme 1 (a) The type of pyramidal arrangements (I) in [Cu(m-
Cl)2Cu] units for complexes 1 and 2. (b) Schematic representation of
the magnetic orbitals of 1.
and 2, are needed in order to explore this magneto-structural
II
correlation. Furthermore, Cu ions have weakly coordinated
axial chloride anions in both complexes that may be replaced
by other donor molecules or ions (such as azide, thiocyanate
II
and cyanate, etc.) to form the corresponding Cu dimers,
which is under way in our laboratory.
The experimental d value is 9.4ꢁ for 2, thus enhancing the
II
ferromagnetic contribution between bothCu
atoms and,
Experimental
logically, diminishing the global antiferromagnetic coupling.
For 1, however, the d value is zero, increasing the anti-
ferromagnetic component in the global ferromagnetic cou-
Materials and general methods
II
pling. From the magnetic parameters of several such Cu
All the reagents and solvents for syntheses and analyses were
of analytical grade. FT-IR spectra (KBr pellets) were taken on
dimers (type I),23–28,30–35 as listed in Table 2, we can also see
that the magnetic coupling is, as expected, relatively small
(either ferro- or antiferromagnetic) due to the near orthogon-
ality of the magnetic orbitals as illustrated in Scheme 1(b).
a
FT-IR 170SX (Nicolet) spectrometer and electronic
absorption spectra on a Hitachi UV-3010 spectrometer. Car-
bon, hydrogen, and nitrogen analyses were performed on a
1
Perkin–Elmer 240C analyzer. H NMR spectra were recorded
on a Bruker AC-P 400 spectrometer (400 MHz) at 25 ꢁC with
tetramethylsilane as the internal reference. ESR spectra were
recorded on powder samples at X-band frequency witha
Bruker 300E automatic spectrometer, varying the temperature
between 4 and 300 K.
Conclusions
II
Two novel di-m-chloride Cu dimers withnew diazamesocyclic
ligands functionalized by pyridine pendants have been
rationally designed and synthesized, and their structures elu-
cidated by X-ray analyses. Complex 1, obtained from direct
self-assembly by the metal ion and organic spacer, constitutes
a rare example of a paramagnetic dinuclear metallacycle.36 The
crucial structural parameter f=R for complexes 1 and 2
(having the same geometric arrangement) are almost the same,
however, their magnetic couplings are different. This indicates
that the superexchange pathway of such complexes depends on
various orbitals, and therefore, different structural dimers
must be studied separately. More appropriate examples, like 1
Magnetic measurements
Magnetic measurements were carried out in the Servei de
Magnetoquımica (Universitat de Barcelona) on polycrystalline
samples (30 mg) witha Quantum Design MPMS SQUID
susceptometer operating at a magnetic field of 0.1 T between 2
and 300 K. The diamagnetic corrections were evaluated from
Pascal’s constants.
II
Table 2 Structural and magnetic data of some out-of-plane di-m-chloro-bridged Cu complexes
+
+
+
Compounda
J=cmÀ1
fCuÀClÀCu
=
RCuÀCl=A
f=R=A
dCuÁ Á ÁCu=A
Ref.
ꢁ
[Cu(tmso)Cl2]2
[Cu(2-Mepy)Cl2]2
[Cu(terpy)Cl]2(PF6)2
[Cu(tmen)Cl2]2
[Cu(Metz)(dmf)Cl2]2
[Cu(Me2en)Cl2]2
[Cu(Et3en)Cl2]2
[Cu(dmg)Cl2]2
Complex 1
À16
88.5
100.6
89.9
96.8
95.3
86.1
94.8
88.0
94.7
86.44
3.02
3.36
2.72
3.15
2.72
2.73
2.73
2.70
2.92
2.64
29.30
29.94
33.05
30.73
35.03
31.53
34.72
32.59
32.43
32.77
3.74
4.40
—
4.09
—
3.46
3.70
3.44
3.86
3.37
30
31
32
33
9
À7.4
À5.8
À5.6
À3.0
À2.2
þ0.06
þ6.3
10.70
À1.95
34
35
15
b
*
Complex 2
**b
a
Abbreviations: tmso ¼ tetramethylensulfoxide, 2-Mepy ¼ 2-Methylpyridine, terpy ¼ N,N0,N00-terpyridine, tmen ¼ N,N,N0,N0-tetramethylethylene-
diamine, Metz ¼ 4-methyltiazole, Me2en ¼ N,N-dimethylethylenediamine, Et3en ¼ N,N,N0-triethylethylenediamine, dmg ¼ dimethylglyoxime,
b
bpy ¼ 2,20-bipyridine. This work.
648
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Table 3 Summary of crystal data for [Cu(HL1)Cl2]2(ClO4)2 (1) and
[Cu2(L2)2Cl2(ClO4)2 (2)
Syntheses
1,5-Bis(pyridin-4-ylmethyl)-1,5-diazacyclooctane tetrahydro-
chloridetrihydrate(L1Á4HClÁ3H2O). AsolutionofDACOÁ2HBr
(1.42 g, 5.3 mmol) and KOH (0.90 g, 13.2 mmol) in anhydrous
ethanol (50 mL) was vigorously stirred for ca. 4 hand then
filtered at room temperature. 4-Chloromethylpyridine (1.84 g,
11.2 mmol) was added to the filtrate with stirring. The stirring
was continued for 3 days at room temperature, and small por-
tions of solid KOH were added to keep the pH value of the
mixture at ca. 9 during this period. Then the mixture was filtered.
After rotary evaporation of the solvent, the residue was dissolved
in water (15 mL) and extracted withCH 2Cl2 (100 mL Â 5). The
combined CH2Cl2 phases were dried over anhydrous MgSO4 .
The organic solvent was removed by rotary evaporation and the
residue was dissolved in anhydrous EtOH. Concentrated
hydrochloride acid was added to the ethanol solution and the
white solid was obtained by filtration. Yield: 1.54 g (60% based
on DACO). 1H NMR (D2O): d 2.21–2.40 (m, 2H), 3.52 (t, J ¼ 5.2
Hz, 8H), 4.68 (s, 4H), 8.9 (d, J ¼ 6.4 Hz, 4H), 8.3 (d, J ¼ 6.4 Hz,
4H). IR (KBr pellet, cmÀ1): 3465vs, 3403b, 3064s, 1641s, 1600s,
1511s, 1482s, 1464s, 1452s, 1427s, 1370w, 1319m, 1232s, 1090m,
999m, 940m, 867m, 812s. Anal. calcd for C18H24N4Á4HClÁ3H2O:
C, 43.56; H, 6.91; N, 11.29%. Found: C, 43.76; H, 6.68; N,
11.51%.
1
2
Formula
FW
T=K
C
36H50Cl6Cu2N8O8
C22H34Cl4Cu2N6O8
779.43
293(2)
Monoclinic
P21=n
11.860(4)
8.114(3)
32.848(10)
90.908(6)
3160.6(17)
4
17.37
5528
2463
0.0611
0.1362
1062.62
293(2)
Monoclinic
P21=n
8.916(3)
19.774(5)
13.027(4)
106.411(6)
2203.1(11)
2
13.88
3850
1456
0.0661
0.1285
Crystal system
Space group
+
a=A
+
b=A
+
c=A
b=ꢁ
+
u=A3
Z
m=cmÀ1
Unique reflect.
Obsd reflect.
Ra
wRb
R ¼ SkFoj À jFck=SjFoj. wR ¼ [S[w(Fo À Fc2)2]=Sw(Fo2)2]1=2
.
a
b
2
dilute KOH aqueous solution. Then the blue solution was
filtered and left to stand at room temperature. Single crystals
suitable for X-ray analysis were obtained by slow evaporation
of the solvent. Yield: 41 mg (70%). IR (KBr pellet, cmÀ1):
1609s, 1571m, 1475s, 1467s, 1448s, 1433s, 1145s, 1111vs,
1090vs, 1053s, 624s. Anal. calcd for C22H34N6Cl4Cu2O8 : C,
33.90; H, 4.40; N, 10.78%. Found: C, 33.55; H, 4.35; N,
10.87%.
1-(Pyridin-2-ylmethyl)-1,4-diazacycloheptane dihydrochloride
tetrahydrate (L2Á2HClÁ4H2O). To a solution of DACH (0.57 g,
5.6 mmol) in anhydrous ethanol (100 mL), 2-(chloro-
methyl)pyridine hydrochloride (0.47 g, 2.9 mmol) was added
withvigorous stirring at reflux for ca. 2 h. The stirring was
continued for about 4 days at room temperature, and small
portions of solid KOH were added during this time. After
filtration of the mixture, the solvent was removed by rotary
evaporation. Then the residue was dissolved in water (15 mL)
and extracted withCH 2Cl2 (100 mL Â 5). The combined
organic phases were dried over anhydrous MgSO4 . The sol-
vent was removed and the residue was purified by silica
gel column chromatography (CH2Cl2–CH3OH–NH3ÁH2O ¼
10 : 10 : 1). The free ligand was further purified by conversion
to the HCl salt to obtain white solid material. Yield: 0.50 g
[52% based on 2-(chloromethyl)pyridine hydrochloride]. 1H
NMR (D2O): d 2.15–2.34 (m, 2H), 3.39 (t, J ¼ 5.2 Hz, 2H),
3.46 (t, J ¼ 5.2 Hz, 2H), 3.60 (s, 4H), 4.52 (s, 2H), 7.75 (t,
J ¼ 6.2 Hz, 1H), 7.80 (d, J ¼ 7.6 Hz, 1H), 8.24 (t, J ¼ 7.6 Hz,
1H), 8.70 (d, J ¼ 4.8 Hz, 1H). IR (KBr pellet, cmÀ1): 3448vs,
3392vs, 3358vs, 2996s, 2693vs, 1642s, 1620s, 1605m, 1547m,
1469s, 1447s, 1435m, 1387m, 1376m, 1298w, 1232m, 1160m,
1111s, 1102m, 1050m, 1016m, 994m, 948m, 775s. Anal. calcd
for C11H17N3Á2HClÁ4H2O: C, 39.29; H, 8.09; N, 12.50%.
Found: C, 39.56; H, 8.03; N, 12.19%.
Caution! Although no problems were encountered in this
study, transition metal perchlorate complexes are potentially
explosive and should be handled with proper precautions.
X-Ray diffraction
Single crystal X-ray diffraction studies were performed on a
Bruker Smart 1000 CCD diffractometer withMo-K a radiation
+
(l ¼ 0.71073 A). The structures were solved by direct methods
and semi-emperical absorption corrections were applied. The
non-hydrogen atoms were located by direct phase determina-
tion and full-matrix least-squares refinement on F2. Hydrogen
atoms were generated theoretically and refined isotropically.
Further details of the structural analyses are summarized in
Table 3.
CCDC reference numbers 182815 and 182816. See http:==
www.rsc.org=suppdata=nj=b1=b110465a= for crystallographic
data in CIF or other electronic format.
Acknowledgements
[Cu(HL1)Cl2]2(ClO4)2 1. The ligand L1Á4HClÁH2O (0.10 g,
0.2 mmol) was dissolved in methanol (20 mL) and to it
Cu(ClO4)2Á6H2O (0.08 g, 0.2 mmol) dissolved in methanol–
acetone (15 mL) was added dropwise withstirring for 2 hat
pH ꢀ 2. Then the solution was filtered and the light green
precipitate was collected. Single crystals suitable for X-ray
analysis were obtained by recrystallization of the precipitate
from methanol. Yield: 64 mg (58%). IR (KBr pellet, cmÀ1):
3066m, 1641s, 1597m, 1506s, 1487m, 1466m, 1454m, 1145s,
1090vs, 623vs. Anal. calcd for C36H50N8Cl6Cu2O8 : C, 40.69;
H, 4.74; N, 10.55%. Found: C, 40.90; H, 5.08; N, 10.20%.
This work was financially supported by Natural Science
Foundation of China (no. 29971019), Tianjin Natural Science
Foundation and the Spanish government (Grant BQU2000-
0791).
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