Polymeric networks of copper(II) phenylmalonate with heteroaromatic N-donor ligands: Synthesis, crystal structure, and magnetic properties

Article abstract of DOI:10.1021/ic0503986

Two new phenylmalonate-bridged copper(II) complexes with the formulas [Cu(4,4′-bpy)(Phmal)]_n·2nH₂O (1) and [Cu(2,4′-bpy)(Phmal)(H₂O)]_n (2) (Phmal = phenylmalonate dianion, 4,4′-bpy = 4,4′-bipyridine, 2,4′-bpy = 2,4′-bipyridine) have been synthesized and characterized by X-ray diffraction. Complex 1 crystallizes in monoclinic space group P2₁, Z = 4, with unit cell parameters of a = 9.0837(6) A, b = 9.3514(4) A, c = 11.0831(8) A, and β = 107.807(6)°, whereas complex 2 crystallizes in orthorhombic space group C2cb, Z = 8, with unit cell parameters of a = 10.1579(7) A, b = 10.3640(8) A, and c = 33.313(4) A. The structures of 1 and 2 consist of layers of copper(II) ions with bridging bis-monodentate phenylmalonate (1 and 2) and 4,4′-bpy (1) ligands and terminal monodentate 2,4′-bpy (2) groups. Each layer in 1 contains rectangles with dimensions of 11.08 x 4.99 A², the edges being defined by the Phmal and 4,4′-bpy ligands. The intralayer copper-copper separations in 1 through the anti-syn equatorial-apical carboxylate-bridge and the 4,4′-bpy molecule are 4.9922(4) and 11.083(1) A, respectively. The anti-syn equatorial-equatorial carboxylate bridge links the copper(II) atoms in complex 2 within each layer with a mean copper-copper separation of 5.3709(8) A. The presence of 2,4′-bpy as a terminal ligand accounts for the large interlayer separation of 15.22 A. The copper(II) environment presents a static pseudo-Jahn-Teller disorder which has been studied by EPR and low-temperature X-ray diffraction. Magnetic susceptibility measurements of both compounds in the temperature range 2-290 K show the occurrence of weak antiferromagnetic [J = -0.59(1) cm^-1 (1)] and ferromagnetic [J = +0.77(1) cm^-1 (2)] interactions between the copper(II) ions. The conformation of the phenylmalonate-carboxylate bridge and other structural factors, such as the planarity of the exchange pathway in 1, account for the different nature of the magnetic interaction.

Full text of DOI:10.1021/ic0503986

Inorg. Chem. 2005, 44, 7794−7801
Polymeric Networks of Copper(II) Phenylmalonate with Heteroaromatic
N-donor Ligands: Synthesis, Crystal Structure, and Magnetic Properties
Jorge Pasa´n,† Joaqu´ın Sanchiz,‡ Catalina Ruiz-Pe´rez,*,† Francesc Lloret,§ and Miguel Julve§
Laboratorio de Rayos X y Materiales Moleculares, Departamento de F´ısica Fundamental II,
UniVersidad de La Laguna, AV. Astrof´ısico Francisco Sa´nchez s/n,
38206 La Laguna (Tenerife), Spain, Laboratorio de Rayos X y Materiales Moleculares,
Departamento de Qu´ımica Inorga´nica, UniVersidad de La Laguna, AV. Astrof´ısico Francisco
Sa´nchez s/n, 38204 La Laguna (Tenerife), Spain, and Departament de Qu´ımica Inorga`nica/
Instituto de Ciencia Molecular, Facultat de Qu´ımica, UniVersitat de Vale`ncia, AV. Dr. Moliner 50,
46100 Burjassot (Vale`ncia), Spain
Received March 17, 2005
Two new phenylmalonate-bridged copper(II) complexes with the formulas [Cu(4,4
[Cu(2,4 -bpy)(Phmal)(H2O)]n (2) (Phmal phenylmalonate dianion, 4,4 -bpy 4,4
bipyridine) have been synthesized and characterized by X-ray diffraction. Complex 1 crystallizes in monoclinic
space group P21, Z 4, with unit cell parameters of a 9.0837(6) Å, b 9.3514(4) Å, c 11.0831(8) Å, and
â ) 107.807(6) , whereas complex 2 crystallizes in orthorhombic space group C2cb, Z 8, with unit cell parameters
of a 10.1579(7) Å, b 10.3640(8) Å, and c 33.313(4) Å. The structures of 1 and 2 consist of layers of
copper(II) ions with bridging bis-monodentate phenylmalonate (1 and 2) and 4,4 -bpy (1) ligands and terminal
monodentate 2,4 -bpy (2) groups. Each layer in 1 contains rectangles with dimensions of 11.08
4.99 Å2, the
edges being defined by the Phmal and 4,4 -bpy ligands. The intralayer copper copper separations in 1 through
the anti syn equatorial apical carboxylate-bridge and the 4,4 -bpy molecule are 4.9922(4) and 11.083(1) Å,
respectively. The anti syn equatorial equatorial carboxylate bridge links the copper(II) atoms in complex 2 within
each layer with a mean copper copper separation of 5.3709(8) Å. The presence of 2,4 -bpy as a terminal ligand
accounts for the large interlayer separation of 15.22 Å. The copper(II) environment presents a static pseudo-Jahn
Teller disorder which has been studied by EPR and low-temperature X-ray diffraction. Magnetic susceptibility
′
-bpy)(Phmal)]n
‚
2nH2O (1) and
′
)
′
)
′
-bipyridine, 2,4
′
-bpy 2,4
)
′-
)
)
)
)
°
)
)
)
)
′
′
×
′
−
−
−
′
−
−
−
′
−
measurements of both compounds in the temperature range 2
−
290 K show the occurrence of weak antiferromagnetic
1
1
[J ) −0.59(1) cm- (1)] and ferromagnetic [J ) +0.77(1) cm- (2)] interactions between the copper(II) ions. The
conformation of the phenylmalonate
−carboxylate bridge and other structural factors, such as the planarity of the
exchange pathway in 1, account for the different nature of the magnetic interaction.
Introduction
at understanding the structural and chemical factors that
govern the exchange coupling between paramagnetic centers
through multiatom bridges are of continuing interest.3,6-8
The investigation of properties, such as porosity, guest
inclusion, chirality, and magnetism, and their cooperative
effects in self-assembled multifunctional molecular materials
are of current interest. The design and exploration of new
synthetic routes to obtain this type of metal-organic
coordination network are topics of the recent research of
inorganic chemists.1-5 In the context of molecular magne-
tism, the study of the magnetostructural correlations aimed
(1) Pikington, M.; Decurtins, S. Crystal Design: Structure and Function;
Desiraju, G. R., Ed.; Wiley: Chichester, U.K., 2003.
(2) (a) Janiak, C. Dalton Trans. 2003, 2781. (b) Moulton, B.; Zaworotko,
M. J. Chem. ReV. 2001, 101, 1629. (c) Zaworotko, M. J. Chem.
Commun. 2001, 1.
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Coronado, E., Delhae`s, P., Gatteschi, D., Miller, J. S. Eds.; NATO
ASI Series E321; Kluwer: Dordrecht, The Netherlands, 1996.
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J., Rovira, C., Amabilino, D. B., Eds.; NATO ASI Series C518;
Kluwer: Dordrecht, The Netherlands, 1999.
* To whom correspondence should be addressed. E-mail: caruiz@ull.es.
† Departamento de F´ısica Fundamental II, Universidad de La Laguna.
‡ Departamento de Qu´ımica Inorga´nica, Universidad de La Laguna.
§ Departament de Qu´ımica Inorga`nica/Instituto de Ciencia Molecular,
Universitat de Vale`ncia.
7794 Inorganic Chemistry, Vol. 44, No. 22, 2005
10.1021/ic0503986 CCC: $30.25
© 2005 American Chemical Society
Published on Web 09/24/2005

Phenylmalonate-Bridged Cu(II) Complexes
A reasonable synthetic approach to build three-dimensional
structures in crystal engineering consists of connecting layers
of transition metal ions through bridging ligands.1,2 The
dimensionality of the structure can be controlled by a careful
selection of the metal coordination structure and the organic
spacer. Recent reports have focused on the malonate ligand
(anion of the malonic acid, hereafter noted mal) as a flexible
and fruitful tool for the design of magnetic systems with
different dimensionalities when an appropriate coligand is
used.9-11 The introduction of substituents on the methylene
group of the malonate ligand could induce different confor-
mations because of geometrical constraints, and it would
make possible specific interactions between substituents,
which would contribute to the overall stability of the resulting
compound. In the first steps of these investigations, we have
focused on the phenylmalonate dianion (Phmal), and recent
reports were devoted to its complexation of copper(II).12
The dimensionality of the structures of the copper(II)-
phenylmalonate coordination complexes can be modified
with the presence of adequate ligands such as 4,4′-bipyridine
(4,4′-bpy) and 2,4′-bipyridine (2,4′-bpy). The efficiency of
these ligands stems from their rigidity, which allows for some
degree of control to be exerted upon the steric constraints
of the assembly process. The use of these ligands has yielded
a great variety of coordination polymers, some of them
featuring unprecedented physical phenomena (porosity,
catalysis, gas and small molecule sorption, magnetism, etc).
The current state of the knowledge in this topical area is
described in several recent reviews.2,13
1 and 2 are two-dimensional compounds that are structurally
very different because of the terminal and bridging coordina-
tion modes of the 2,4′-bpy and 4,4′-bpy ligands, respectively.
Intralayer antiferromagnetic and ferromagnetic interactions
are observed in 1 and 2, respectively.
Experimental Section
Materials. Phenylmalonic acid (H2Phmal), copper(II) acetate
hydrate [Cu(CH3COO)2‚2.5H2O], 4,4′-bipyridine (4,4′-bpy), 2,4′-
bipyridine (2,4′-bpy), and methanol (MeOH) were purchased from
Aldrich and used as received. Elemental analyses (C, H, N) were
performed on an EA 1108 CHNS-O microanalytical analyzer.
Synthesis of [Cu(4,4′-bpy)(Phmal)]n‚2nH2O (1). An aqueous
solution of copper(II) phenylmalonate (120 mg, 0.5 mmol), prepared
as previously described,12 was placed into one arm of an H-shaped
tube, and a 50/50 MeOH/water solution of the 4,4′-bpy (78 mg,
0.5 mmol) was put into the other arm. A 50/50 MeOH/water
solution was added dropwise to fill the H-shaped tube. Rectangular
blue single crystals of 1 appeared within a week by slow diffusion
at room temperature and were used for all measurements. Anal.
Calcd for C19H18N2O6Cu (1): C, 52.59; H, 4.15; N, 6.46. Found:
C, 52.30; H, 4.25; N, 6.38. IR (KBr, cm-1): ν 1614 vs, 1580 vs,
1494 m, 1430 s, 790 m.
Synthesis of [Cu(2,4′-bpy)(Phmal)(H2O)]n (2). Compound 2
was obtained by following a similar procedure to that of 1, but
2,4′-bpy was used instead of 4,4′-bpy. Single crystals of 2 as blue
rods appeared within a week by slow diffusion at room temperature
and were used for all measurements. Anal. Calcd for C19H16N2O5-
Cu (2): C, 54.87; H, 3.69; N, 6.74. Found: C, 54.58; H, 3.76; N,
6.72. IR (KBr, cm-1): ν 1614 vs, 1593 vs, 1452 m, 1410 vs, 788
s.
In previous reports, these ligands were incorporated into
copper(II)-malonate complexes producing, for instance, the
isolated tetranuclear unit [Cu4(mal)4(2,4′-bpy)4(H2O)4]‚8H2O
and the two-dimensional compound [Cu4(mal)4(4,4′-bpy)2-
(H2O)4]n.14 In addition to the stacking interactions between
the pyridyl groups that stabilize the structure in both malonate
compounds, π-π interactions between the pyridyl and
phenyl rings are expected in the Phmal-copper(II) com-
plexes.
We report herein the synthesis, crystallographic study, and
magnetic properties of two new phenylmalonate-copper-
(II) complexes with the formulas [Cu(4,4′-bpy)(Phmal)]n‚
2nH2O (1) and [Cu(2,4′-bpy)(Phmal)(H2O)]n (2). Complexes
Physical Techniques. IR spectra (450-4000 cm-1) of 1 and 2
were recorded on a Bruker IF S55 spectrophotometer with samples
prepared as KBr pellets. EPR spectra on a polycrystalline sample
of 2 were carried out on a Bruker Elexsys E580 EPR spectrometer
operating at Q-band (34 GHz) frequency. Magnetic susceptibility
measurements on polycrystalline samples of 1 and 2 were performed
in the temperature range of 1.9-290 K with a Quantum Design
SQUID magnetometer. Diamagnetic corrections of the constituent
atoms were estimated from Pascal’s constants15 to be -238 × 10-6
and -225 × 10-6 cm3 mol-1 for 1 and 2, respectively. Experimental
susceptibilities were also corrected for the temperature-independent
paramagnetism [60 × 10-6 cm3 mol-1 per Cu(II) ion] and the
magnetization of the sample holder.
(14) For malonate containing Cu(II) complexes, see: (a) Chattopadhyay,
D.; Chattopadhyay, S. K.; Lowe, P. R.; Schwalbe, C. H.; Mazumder,
S. K.; Rana, A.; Ghosh, S. J. Chem. Soc., Dalton Trans. 1993, 913.
(b) Gil de Muro, I.; Mautner, F. A.; Insausti, M.; Lezama, L.; Arriortua,
M. I.; Rojo, T. Inorg. Chem. 1998, 37, 3243. (c) Ruiz-Pe´rez, C.;
Sanchiz, J.; Herna´ndez-Molina, M.; Lloret, F.; Julve, M. Inorg. Chim.
Acta 2000, 298, 245. (d) Ruiz-Pe´rez, C.; Sanchiz, J.; Herna´ndez-
Molina, M.; Lloret F.; Julve, M. Inorg. Chem. 2000, 39, 1363. (e)
Ruiz-Pe´rez, C.; Herna´ndez-Molina, M.; Lorenzo-Luis, P.; Lloret, F.;
Cano, J.; Julve, M. Inorg. Chem. 2000, 39, 3845. (f) Ruiz-Pe´rez, C.;
Sanchiz, J.; Herna´ndez-Molina, M.; Lloret, F.; Julve, M. Inorg. Chim.
Acta 2000, 298, 245. (g) Rodr´ıguez-Mart´ın, Y.; Sanchiz, J.; Ruiz-
Pe´rez, C.; Lloret, F.; Julve, M. Inorg. Chim. Acta 2001, 326, 20. (h)
Rodr´ıguez-Mart´ın, Y.; Ruiz-Pe´rez, C.; Sanchiz, J.; Lloret, F.; Julve,
M. Inorg. Chim. Acta 2001, 318, 159. (i) Sanchiz, J.; Rodr´ıguez-
Mart´ın, Y.; Ruiz-Pe´rez, C.; Mederos, A.; Lloret, F.; Julve, M. New J.
Chem. 2002, 26, 1624. (j) Rodr´ıguez-Mart´ın, Y.; Herna´ndez-Molina,
M.; Delgado, F. S.; Pasa´n, J.; Ruiz-Pe´rez, C.; Sanchiz, J.; Lloret, F.;
Julve, M. CrystEngComm 2002, 4, 440. (k) Sain, S.; Maji, T. K.;
Mostafa, G.; Lu, T. H.; Chanduri, N. R. New J. Chem. 2003, 27, 185.
(15) Earnshaw, A. Introduction to Magnetochemistry; Academic Press:
London, 1968.
(6) Magnetic Molecular Materials; Gatteschi, D., Kahn, O., Miller, J. S.,
Palacio, F., Eds.; Kluwer: Dordrecht, The Netherlands, 1991.
(7) Kahn, O. Molecular Magnetism; VCH: New York, 1993.
(8) (a) Olivier Kahn Special Issue. Polyhedron 2001, 20 (11-14). (b)
Proceedings of the 8th International Conference on Molecule-Based
Magnets. Polyhedron 2003, 22 (14-17).
(9) Rodr´ıguez-Mart´ın, Y.; Herna´ndez-Molina, M.; Delgado, F. S.; Pasa´n,
J.; Ruiz-Pe´rez, C.; Sanchiz, J.; Lloret, F.; Julve, M. CrystEngComm
2002, 4, 522.
(10) Ruiz-Pe´rez, C.; Rodr´ıguez-Mart´ın, Y.; Herna´ndez-Molina, M.; Del-
gado, F. S.; Pasa´n, J.; Sanchiz, J.; Lloret, F.; Julve, M. Polyhedron
2003, 22, 2111.
(11) Pasa´n, J.; Delgado, F. S.; Rodr´ıguez-Mart´ın, Y.; Herna´ndez-Molina,
M.; Ruiz-Pe´rez, C.; Sanchiz, J.; Lloret, F.; Julve, M. Polyhedron 2003,
22, 2143.
(12) (a) Pasa´n, J.; Sanchiz, J.; Ruiz-Pe´rez, C.; Lloret, F.; Julve, M. New J.
Chem. 2003, 27, 1557. (b) Pasa´n, J.; Sanchiz, J.; Ruiz-Pe´rez, C.; Lloret,
F.; Julve, M. Eur. J. Inorg. Chem. 2004, 4081.
(13) (a) Batten, S. R.; Robson, R. Angew. Chem., Int. Ed. 1998, 37, 1461.
(b) Batten, S. R. CrystEngComm, 2001, 3, 67. (c) James, S. L. Chem.
Soc. ReV. 2003, 32, 276.
Inorganic Chemistry, Vol. 44, No. 22, 2005 7795

Pasa´n et al.
Table 1. Crystallographic Data for Complexes 1 and 2
1
2
2
formula
fw
cryst syst
space group
a (Å)
C19H18O6N2Cu C19H13O5N2Cu C19H13O5N2Cu
433.86
412.88
orthorhombic
C2cb
412.88
monoclinic
P21
orthorhombic
C2cb
9.0837(6)
9.3514(4)
11.0831(8)
107.807(6)
896.35(10)
4
10.1579(7)
10.3640(8)
33.313(4)
-
10.2178(4)
10.2909(5)
32.825(2)
-
b (Å)
c (Å)
â (deg)
V (Å3)
3507.1(6)
8
3451.6(3)
8
Z
µ(Mo KR) (cm-1
T (K)
)
12.59
12.84
13.01
293(2)
293(2)
100(2)
F
calc (g cm-3
)
1.593
1.642
1.612
λ (Å)
0.71073
0.71073
0.71073
-14 e h e 12
-14 e k e 11
index ranges
-12 e h e 12 -14 e h e 13
-13 e k e 12
-15 e l e 13
-14 e k e 13
-46 e l e 43 -46 e l e 36
independent reflns 4940 (0.050)
4904 (0.085)
4571 (0.079)
(Rint
)
observed reflns
[I > 2σ(I)]
parameters
GOF
4242
4224
4247
254
263
263
1.025
0.0394
0.0858
0.0525
0.0907
1.038
0.0485
0.1228
0.0577
0.1282
1.132
0.0678
0.1807
0.0754
0.1905
R [I > 2σ(I)]
R
w [I > 2σ(I)]
R (all data)
w (all data)
R
Crystallographic Data Collection and Structural Determi-
nation. Single crystals of 1 and 2 were used for data collection
with a Nonius Kappa CCD diffractometer. The data collection was
carried out using graphite-monochromated Mo KR radiation (λ )
0.71073 Å) at 293 K, and it was also done at 100 K for compound
2. A summary of the crystallographic data and structure refinement
is given in Table 1. The structures were solved by direct methods
and refined with a full-matrix least-squares technique on F2 using
the SHELXL-9716 program included in the WINGX17 software
package. All non-hydrogen atoms were refined anisotropically. The
C(13) and C(14) carbon atoms from the 2,4′-bpy ligand in 2 were
delocalized between two positions with the sof parameter being
0.48 and 0.52. The hydrogen atoms in both structures were set in
calculated positions and isotropically refined as riding atoms. The
final geometrical calculations and graphical manipulations were
carried out with the PARST9718 and CRYSTALMAKER19 pro-
grams.
Description of the Structures
Figure 1. View of a fragment of the structures of (a) 1 and (b) 2 with the
numbering scheme.
[Cu(4,4′-bpy)(Phmal)]n‚2nH2O (1). The structure of
complex 1 consists of chains of carboxylate(phenylmalonate)-
bridged copper(II) ions which are linked through bis-
monodentate 4,4′-bpy ligands to produce a sheetlike polymer
growing in the bc plane (Figures 1a and 2a). Rectangles with
dimensions of 11.08 × 4.99 Å2 are repeated within each
layer, the longer edge corresponding to the 4,4′-bpy ligand
(c axis), whereas the shorter side is defined by the phenyl-
malonate-carboxylate group (b axis). The separation be-
tween adjacent layers is 8.64 Å. The layers are not stacked
parallel along the a axis but form an angle of 17.807(6)°
with the normal plane vector. They are staggered in the
ABCABCABC trend and the nearest neighbors are shifted
by c/3 from each other. Adjacent layers are linked through
hydrogen bonds involving two carboxylate oxygens [O(1)
and O(3)] and the crystallization water molecules (Figure
3); the values of the O‚‚‚O distances range from 2.839(5) to
3.085(6) Å. It should be noted that the crystallization water
molecules are placed between the layers close to the
carboxylate groups because of the hydrogen bonds they form.
Thus, the water molecules avoid the rectangular cavities
because of their hydrophobic character. The π-π interactions
play an important role in the packing of this structure as
observed in previous reports concerning Phmal-containing
copper(II) complexes.12 Several intra- and interlayer C-
H‚‚‚π contacts can be identified,20 the shortest centroid‚‚‚
centroid distance being 4.8781(4) Å, a value which is close
to the molecular dynamics calculation for benzene21 (opti-
mum distance of 4.99 Å between two ring centers in the
T-shaped orientation). The values of the dihedral angle
between the aromatic rings range from 52.2° to 89.31°.
(16) Sheldrick, G. M. SHELXL-97 and SHELXS-97; Universita¨t Go¨ttin-
gen: Go¨ttingen, Germany, 1998.
(17) Farrugia, L. J. J. Appl. Crystallogr. 1999, 32, 837.
(18) Nardelli, M. PARST95, J. Appl. Crystallogr. 1995, 28, 659.
(19) CrystalMaker, version 4.2.1; CrystalMaker Software: Bicester, U.K.
7796 Inorganic Chemistry, Vol. 44, No. 22, 2005

Phenylmalonate-Bridged Cu(II) Complexes
Figure 3. Supramolecular layers of phenylmalonate-copper(II) chains
bridged through hydrogen bonds with the crystallization water molecules.
Phenyl rings of Phmal, carbon atoms of 4,4′-bpy, and hydrogen atoms are
omitted for clarity.
Table 2. Selected Bond Lengths (Å) and Bond Angles (deg) for
Compounds 1 and 2a,b
1
Cu(1)-O(1a)
Cu(1)-O(2)
Cu(1)-O(4)
1.952(2)
2.185(2)
1.928(2)
Cu(1)-N(1)
Cu(1)-N(2b)
2.041(2)
2.0220(19)
O(4)-Cu(1)-O(1a)
O(4)-Cu(1)-N(2b)
O(1a)-Cu(1)-N(2b)
O(4)-Cu(1)-N(1)
O(1a)-Cu(1)-N(1)
176.69(9) N(2b)-Cu(1)-N(1) 168.70(12)
90.60(9) O(4)-Cu(1)-O(2)
88.94(9) O(1a)-Cu(1)-O(2)
89.26(9) N(2b)-Cu(1)-O(2)
90.55(9) N(1)-Cu(1)-O(2)
89.40(8)
93.90(8)
94.72(11)
95.29(9)
2
Cu(1)-O(2)
Cu(1)-O(4)
Cu(1)-O(1c)
2.128(3)
2.076(3)
2.208(3)
Cu(1)-O(3d)
Cu(1)-N(1)
Cu(1)-O(1w)
2.110(3)
2.026(3)
2.004(2)
O(1w)-Cu(1)-N(1)
O(1w)-Cu(1)-O(4)
N(1)-Cu(1)-O(4)
O(1w)-Cu(1)-O(3d)
N(1)-Cu(1)-O(3d)
O(4)-Cu(1)-O(3)
O(1w)-Cu(1)-O(2)
N(1)-Cu(1)-O(2)
176.32(11) O(4)-Cu(1)-O(2)
90.71(12) O(3d)-Cu(1)-O(2)
90.73(12) O(1w)-Cu(1)-O(1c)
91.68(11) N(1)-Cu(1)-O(1c)
87.19(11) O(4)-Cu(1)-O(1c)
174.49(13) O(3d)-Cu(1)-O(1c)
91.59(11) O(2)-Cu(1)-O(1c)
91.91(12)
84.79(14)
90.18(13)
89.50(10)
87.13(11)
89.41(13)
95.57(12)
174.12(14)
Figure 2. (a) View through the [100] direction of a fragment of complex
1. The 4,4′-bpy ligand connects chains of phenylmalonate-bridged copper-
(II) ions. Hydrogen atoms are omitted for clarity. (b) Crystal packing of
complex 2 with the corrugated layers viewed through the [101] direction.
a Estimated standard deviations in the last significant digits are given in
parentheses. b Symmetry code is as follows: (a) -x, y - 1/2, -z; (b) x, y,
z + 1; (c) x, y + 1/2, -z + 1/2; and (d) x + 1/2, y, -z + 1/2.
Each copper atom exhibits a somewhat distorted square
pyramidal environment, the geometric τ value being 0.13 (τ
) 0 for square pyramidal and τ ) 1 for trigonal bipyrami-
dal).22 Two nitrogen atoms from the 4,4′-bpy molecule [N(1)
and N(2a); (a) x, y, z + 1] and two carboxylate-oxygen atoms
from the Phmal ligand [O(4) and O(1b); (b) -x, y - 1/2,
-z] build the basal plane, whereas another carboxylate-
oxygen atom [O(2)] occupies the apical position (selected
interatomic distances and angles are listed in Table 2). The
equatorial bond lengths vary in the range of 1.928(2)-2.041-
(2) Å, and the apical bond distance is 2.185(2) Å. The copper
atom is shifted by 0.0989(3) Å from the mean basal plane
toward the apical position. The copper-copper separation
through the phenylmalonate-carboxylate bridge is 4.9922-
(4) Å, a value which is much shorter than the metal-metal
separation through the 4,4′-bpy ligand [11.083(1) Å].
The phenylmalonate ligand simultaneously adopts mono-
dentate [through O(1) to Cu(1e); (e) -x, y + 1/2, -z] and
bidentate [through O(2) and O(4) to Cu(1)] coordination
modes. The bidentate coordination of the Phmal ligand
involves one equatorial O(4) bond and one apical O(2) bond,
a feature which is unprecedented for Phmal- or malonate-
containing copper(II) complexes,12,14 although it is not
(20) For examples of C-H‚‚‚π interactions, see: (a) Janiak, C.; Temiz-
demir, S.; Dechert, S.; Deck, W.; Girgsdies, F.; Heinze, J.; Kolm, M.
J.; Scharmann, T. G.; Zipffel, O. M. Eur. J. Inorg. Chem. 2000, 1229.
(b) McNelis, B. J.; Nathan, L. C.; Clark, C. J. J. Chem. Soc., Dalton
Trans. 1999, 1831. (c) Biradha, K.; Seward, C.; Zaworotko, M. J.
Angew. Chem., Int. Ed. 1999, 38, 492.
(21) Cox, E. G.; Cruickshank, D. W.; Smith, J. A. S. Proc. R. Soc. London,
Ser. A 1958, 247, 1
(22) Addison, A. W.; Rao, T. N. J. Chem. Soc., Dalton Trans. 1984, 1349.
Inorganic Chemistry, Vol. 44, No. 22, 2005 7797

Pasa´n et al.
uncommon for copper(II)-oxalate complexes.23,24 The pref-
erence of the copper(II) ion for the nitrogen donor atoms
versus the oxygen ones and the fact that the two 4,4′-bpy
nitrogen atoms in 1 occupy trans positions in the coordination
sphere of the copper atom account for this singularity. The
value of the angle subtended at the copper atom by the
bidentate Phmal ligand is 89.40(8)°. The pyridyl rings of
the 4,4′-bpy molecule are planar, but the ligand as a whole
is far from being planar [the dihedral angle between the two
pyridyl rings is 19.99(10)°]. As far as we know, there are
two recently reported compounds whose structures are very
24
similar to that of 1: [Cu3(µ-ox)3(µ-4,4′-bpy)(4,4′-bpy)2]n
25
and {[Cu(Hsal)2(4,4′-bpy)]‚H2O‚H2sal}n (ox ) oxalate
dianion and H2sal ) salicylic acid). In light of these structures
(see Supporting Information), it is clear that the rectangular
moiety observed in 1 is not unique, but layered motifs are
ensured by the reaction of copper(II) with the appropriate
bridging ligand and 4,4′-bpy.
Figure 4. View of the corrugated layer of the phenylmalonate-bridged
copper(II) atoms of complex 2 forming a square grid. The phenyl (Phaml)
pyridyl (2,4′-bpy) rings are omitted for the sake of clarity.
We would like to finish the present structural description
with a comparison of the structure of 1 with that of the
previously reported malonato copper(II) complex [Cu4(mal)4-
(H2O)4(4,4′-bpy)2]14h (H2mal ) malonic acid). This structure
consists of layers of tetranuclear entities of carboxylate-
malonate-bridged copper(II) ions linked by 4,4′-bpy ligands.
The tetranuclear units are small squares with the copper(II)
ions at the corners and the bridging-malonato ligand defining
the edges. These units are linked by the 4,4′-bpy groups to
form large squares of 15.784(1) × 15.784(1) Å2. Although
the dimensionality of this structure as a whole is identical
to that of 1, the presence of the phenyl ring in 1 provides
additional interactions (C-H‚‚‚π- and π-π-type interactions,
steric effects, etc.) which account for the new coordination
mode of the Phmal ligand and the hydrophobic character in
the structure.
[Cu(2,4′-bpy)(Phmal)(H2O)]n (2). The structure 2 consists
of a sheetlike arrangement of trans-aqua(2,4′-bipyridine)-
copper(II) units bridged by phenylmalonate ligands running
parallel to the ac plane (see Figures 1b and 2b). A corrugated
square grid of copper atoms results (Figure 4) where the 2,4′-
bpy terminal ligands are alternatively located above and
below each layer and, at the same time, inversely to the
position of the phenyl group of the Phmal ligand. These
sheets are stacked parallel along the b axis but rotated 90°
through this axis in a twisted fashion (i.e., odd units in the
same position and even units rotated by 90°) exhibiting the
ABABAB sequence. Intralayer hydrogen bonds involving
the coordinated water molecule [O(1w)] and oxygen atoms
from the carboxylate-phenylmalonate groups [2.615(4) and
Table 3. Bond Distances at Cu(1) and Calculated ∆MSDA Values for
Compound 2 at Different Temperaturesa
T ) 293 K
T ) 100 K
∆MSDA
∆MSDA
bond
d (Å)
(×10-4 Å2)
d (Å)
(×10-4 Å2)
Cu(1)-O(2)
Cu(1)-O(4)
Cu(1)-O(1c)
Cu(1)-O(3d)
Cu(1)-O(1w)
Cu(1)-N(1)
2.128(3)
2.076(3)
2.208(3)
2.110(3)
2.004(2)
2.026(3)
269
255
293
315
59
2.111(5)
2.087(5)
2.187(5)
2.156(5)
1.992(3)
2.014(4)
355
301
247
201
29
64
36
a Symmetry code is as follows: (c) x, y + 1/2, -z + 1/2 and (d) x -1/2,
y, -z +1/2.
2.633(4) Å for O(1w)‚‚‚O(2c) and O(1w)‚‚‚O(4f), respec-
tively; (c) x, y + 1/2, -z + 1/2; (f) x - 1/2, y, -z + 1/2]
contribute to stabilize the structure. Weak π-type interactions
occur between the phenyl rings and the 2,4′-bpy groups, the
shortest centroid‚‚‚centroid distance being 4.154(6) Å and
the shortest off-set angle being 29.6°, values which are
somewhat larger than the average ones observed in π-π
interactions with pyridyl-like groups.26
Each copper atom exhibits a six-coordinated environment
defined by four carboxylate-phenylmalonate oxygen atoms,
one 2,4′-bpy-nitrogen atom, and a water molecule. The
CuNO5 chromophore could be described as an unusual
compressed tetragonal octahedron with two short distances
[2.004(2) and 2.026(3) Å for Cu(1)-O(1w) and Cu(1)-N(1),
respectively] and four long ones [values ranging from 2.076-
(3) to 2.208(3) Å] (see Table 2). A low-temperature
crystallographic study has been carried out to give a clear-
cut answer to this compression. In light of Table 3, one can
see that the bond distances and angles at 293 and 100 K do
not vary significantly, and hence, the presence of a static
pseudo-Jahn-Teller disorder could be suspected.27-30 The
(23) (a) Oshio, H.; Nagashima, U. Inorg. Chem. 1992, 31, 3295. (b) Castillo,
O.; Luque, A.; Lloret, F.; Roma´n, P. Inorg. Chim. Acta 2001, 324,
141. (c) Luo, J.; Hong, M.; Liang, Y.; Cao, R. Acta Crystallogr., Sect.
E, 2001, 57, m361. (d) Cavalca, L.; Villa, A. C.; Manfredotti, A. G.;
Tomlinson, A. A. G. J. Chem. Soc., Dalton Trans. 1972, 391. (e)
Castillo, O.; Luque, A.; Julve, M.; Lloret, F.; Roma´n, P. Inorg. Chim.
Acta, 2001, 315, 9. (f) Castillo, O.; Luque, A.; Roma´n, P.; Lloret, F.;
Julve, M. Inorg. Chem. 2001, 40, 5526. (g) Sua´rez-Varela, J.;
Dom´ınguez-Vera, J. M.; Colacio, E.; AÄ vila-Roso´n, J. C.; Hidalgo, M.
A.; Mart´ın-Ramos, D. J. Chem. Soc., Dalton Trans. 1995, 2143.
(24) Castillo, O.; Alonso, J.; Garc´ıa-Couceiro, U.; Luque, A.; Roma´n, P.
Inorg. Chem. Commun. 2003, 6, 803.
(26) Janiak, C. J. Chem. Soc., Dalton Trans. 2000, 3885.
(27) Hathaway, B. J. Struct. Bonding, 1984, 57, 55.
(28) Falvello, L. R. J. Chem. Soc., Dalton Trans. 1997, 4463.
(29) Halcrow, M. A. Dalton Trans. 2003, 4375.
(30) Solanki, N. K.; Leech, M. A.; McInnes, E. J. L.; Mabbs, F. E.; Howard,
J. A. K.; Kilner, C. A.; Rawson, J. M.; Halcrow, M. A. J. Chem.
Soc., Dalton Trans. 2002, 1295.
(25) Zhu, L.-G.; Kitagawa, S. Inorg. Chem. Commun. 2003, 6, 1051.
7798 Inorganic Chemistry, Vol. 44, No. 22, 2005

Phenylmalonate-Bridged Cu(II) Complexes
Figure 5. Two different copper(II) environments [(a) and (b)] which occur
in complex 2 because a static pseudo-Jahn-Teller disorder. Arrows indicate
the atoms that fill equatorial (compressed) or apical (elongated) positions
at the metal environment.
Figure 6. Thermal dependence of the øMT product for complexes 1 and
2 (1, red squares; 2, blue circles). The solid line represents the best fit
through eqs 3 and 4 for complexes 1 and 2, respectively.
vibrational amplitudes of the ligand donor atoms along the
metal-ligand bonds represented by the quantity d2 or
equivalently ∆MSDA27-30 are also listed in Table 3. These
values correspond to the difference in the mean-square
displacements parameters (MSDAs) of a given donor atom
and the Cu atom along their common vector (eqs 1 and 2).
bis-monodentate ligand [through O(1) and O(3) to Cu(1 g)
and Cu(1d), respectively; (g) x, y - 1/2, -z + 1/2]. The
2,4′-bpy ligand is quasi-planar [the dihedral angle between
pyridyl rings is 4°]. The pyridyl ring formed by the N(1)-
C(10)-C(11)-C(12)-C(13)-C(14) set of atoms is slightly
distorted, and two crystallographic positions are found for
the C(13) and C(14) atoms [0.977(16) and 1.012(15) Å for
C(13A)-C(13B) and C(14A)-C(14B), respectively]. These
two positions are also found in the low-temperature X-ray
study of a different crystal; hence, a static disorder within
the crystal could be the responsible for this feature. The
copper-copper separations through the two crystallographi-
cally independent anti-syn carboxylate bridges are 5.3217-
(9) and 5.4202(6) Å, values which are much shorter than
the interlayer Cu‚‚‚Cu distance [15.221(2) Å].
The comparison of the structure of 2 with that of the
previously reported31 malonato-manganese(II) complex of
formula [Mn(mal)(H2O)(2,4′-bpy)]n reveals that both are very
similar, fact that cannot be extended to the compound [Cu4-
(mal)4(2,4-bpy)4(H2O)4]‚8H2O.14j Therefore, from a structural
point of view and in the presence of the 2,4′-bpy ligand, the
copper(II) ion acts as the manganese(II) cation when the
malonate is substituted by the phenylmalonate ligand.
3
3
U n n
i j
∑∑
ij
MSDA ) i)1j)1
(1)
2
|n|
d
2 ) ∆MSDA ) MSDA(donor) - MSDA(Cu) (2)
where Uij is an element of the 3 × 3 matrix of thermal
parameters and ni and nj are elements of the vector describing
the bond. Values of ∆MSDA are typically found in the range
of (10-100) × 10-4 Å2.28 The values of the ∆MSDA for
O(1w) and N(1) are within this range but the four carboxylate
oxygen atoms present ∆MSDAs in the range of (255-315)
× 10-4 Å2. This disparity from the “static” values can be
attributed to the presence of a static pseudo-Jahn-Teller
disorder of two of the three axes of the octahedral copper
environment. The shorter bond distances correspond with
the Cu(1)-O(1w) and Cu(1)-N(1) bonds indicating that
these two atoms belong to the basal plane of Cu(1). The
O(2), O(4), O(1c), and O(3d) [(d) x + 1/2, y, -z + 1/2] are
statically disordered in pairs between the equatorial and axial
positions [two different environments are found within the
crystal, one with O(1w), N(1), O(2), and O(1c) in equatorial
positions and O(4) and O(3d) in axial positions; the other
with O(1w), N(1), O(4), and O(3d) in equatorial positions
and O(2) and O(1c) in axial positions] (Figure 5). The
analysis of the EPR spectrum at room temperature (see
Supporting Information) reveals three different effective g
values (g1 ) 2.27, g2 ) 2.20, g3 ) 2.15) indicating a rhombic
environment of the copper(II) ion or, according to our
approximation, the averaged values of a static pseudo-Jahn-
Teller disorder in the crystal as they appear in the X-ray
crystal structure. EPR spectra at low temperatures do not
change significantly from the rhombic distortion; the slight
variations in the g values are most likely associated with
the spin coupling.
Magnetic Properties
The magnetic properties of compounds 1 and 2 under the
form of the øMT vs T plot [øM is the molar susceptibility per
copper(II) ion] are shown in Figure 6. The values of øMT at
room temperature are 0.41 and 0.42 cm3 mol-1 K for 1 and
2, respectively. These values are as expected for magnetically
isolated spin doublets. The øMT values remains almost
constant down to 10 K for compound 1 and then smoothly
decreases to 0.34 cm3 mol-1 K at 2.0 K indicating that there
is a very weak antiferromagnetic coupling between the
copper(II) ions. For compound 2, øMT remains almost
constant until 30 K and then it increases to reach a value of
0.53 cm3 mol-1 K at 2.0 K, a feature which is indicative of
an overall ferromagnetic coupling in 2.
The phenylmalonate ligand acts simultaneously as a
bidentate ligand [through O(2) and O(4) to Cu(1)] and as a
(31) Rodr´ıguez-Mart´ın, Y.; Herna´ndez-Molina, M.; Sanchiz, J.; Ruiz-Pe´rez,
C.; Lloret, F.; Julve, M. Dalton Trans. 2003, 2359.
Inorganic Chemistry, Vol. 44, No. 22, 2005 7799

Pasa´n et al.
Two different magnetic exchange pathways between
copper atoms are present in 1: the 4,4′-bpy bridging ligand
and the carboxylate bridge in the anti-syn conformation
linking one apical position with an equatorial position at the
copper(II) atoms. Since the distance between the copper(II)
ions through the 4,4′-bpy bridge is 11.083(1) Å and the
values of -J, from previous reports14d,32 on 4,4′-bpy-bridged
copper dimers, vary in the range of 0.05-0.1 cm-1, the
magnetic coupling has to be very small compared with that
of the anti-syn carboxylate bridge. Therefore, from a
magnetic point of view, compound 1 can be seen as uniform
chains of antiferromagnetically coupled copper(II) ions, and
the magnetic data can be analyzed by means of the following
numerical expression:33
(2) interactions. Let us try to analyze, first, the magnitude
and, second, the nature of the magnetic interaction. The
carboxylate group can adopt three different bis-monodentate
bridging modes: syn-syn, anti-anti, and anti-syn. From
moderate to strong antiferromagnetic coupling is observed
for the first two modes, whereas weak either ferromagnetic
or antiferromagnetic interactions occur in the third.35 This
ability of the carboxylate group has been substantiated by
DFT-type calculations.36 As the copper(II) ions in compounds
1 and 2 are bridged by carboxylate groups in the anti-syn
conformation, the weak values of the magnetic coupling
observed are as expected.
In addition to the conformation of the bridge, the relative
orientation of the magnetic orbitals centered on the metal
ions in both compounds is very unfavorable for a strong
magnetic coupling. In the case of compound 1, the carboxy-
late bridge links an equatorial position of one copper(II) ion
with an axial position of the adjacent copper(II) ion. The
magnetic orbital for copper(II) ions in a square pyramidal
Ng2â2
kT
0.25 + 0.074975x + 0.075235x2
øM )
1.0 + 0.9931x + 0.172135x2 + 0.757825x3
(3)
where x ) |J|/kT, the Hamiltonian is defined as ∑iJSi‚Si+1
,
2
2
surrounding is of the dx -y -type; the x and y axes are roughly
J is the magnetic coupling constant, and N, g, â, and k have
their usual meaning. Best-fit parameters using a nonlinear
regression analysis are as follows: J ) -0.59(1) cm-1, g )
2.21(2), and R ) 5.2 × 10-5 (R is the agreement factor
defined as ∑i[(øMT)obs(i) - (øMT)calc(i)]2/∑[(øMT)obs(i)]2) The
calculated curve matches well the experimental data in the
whole temperature range (Figure 6).
2
defined by the equatorial bonds. Some admixture of the dz
orbital is present as a result of trigonal distortion. The
magnetic coupling is very weak because it is the result of
2
2
2
the interaction of a dx -y -type orbital with a dz -type orbital,
the latter having a very small spin density. In the case of
compound 2, the environment of the copper(II) ion is
2
2
distorted octahedral and the magnetic orbital also has dx -y
According to the square lattice layer defined by the copper-
(II) ions of compound 2 (Figure 4), its magnetic data were
analyzed by the high-temperature series expansion derived
from the two-dimensional Heisenberg model for a S ) 1/2
ferromagnetic square lattice34
character. Each copper(II) ion is connected to four other
copper(II) ions through anti-syn carboxylate bridges to give
a quadratic layer. The magnetic coupling in this compound
is also very weak because the equatorial plane of the copper
environment (Scheme 1) is quasi-perpendicular to the plane
of the bridging carboxylate (the exchange pathway) and only
two of the four exchange pathways have important spin
density (half of the exchange pathways are inactive). This
situation is very unfavorable for a large magnetic interaction
and leads to a very weak coupling constant.
We will now try to explain the different nature of the
magnetic coupling for compounds with apparently similar
chemical and structural features. The exchange constant can
be expressed as the sum of two contributions, one ferro-
magnetic (small and positive) and another antiferromagnetic
(negative and proportional to the square of the overlap
between the orbitals on the bridge with those of the metal
ions bearing the unpaired electrons), in such a way that the
lower the overlap is, the smaller the antiferromagnetic
contribution [J ) JF + JAF].37 In the case of compound 1,
the copper(II) ions and carboxylate groups lie in a plane with
an out-of-plane maximum deviation of 0.321(2) Å for O(2).
This situation enhances the overlap between the interacting
magnetic orbitals of the metal ions and those of the atoms
of the bridge and makes the antiferromagnetic term dominant.
On the other hand, the copper(II) ions in compound 2 lie in
10
ø ) [Ng2â2/(3kT)]S(S + 1)(1 + a Kn)
(4)
∑
n
n)1
with K ) J/kT. The coefficients for the square lattice are
represented by an, and J is the intralayer magnetic coupling
between the local spins of the nearest-neighbors with the
Hamiltonian of eq 4 defined as
H ) -Σi JSi‚Si+1
(5)
Best-fit parameters using a nonlinear regression analysis
are as follows: J ) 0.77(1) cm-1, g ) 2.22(1), and R ) 1.2
× 10-5 (R is the agreement factor defined as ∑i[(øMT)obs(i)
- (øMT)calc(i)]2/∑[(øMT)obs(i)]2). The calculated curve matches
well the experimental data in the temperature range explored
(Figure 6). The calculated value of g is in agreement with
that obtained from the EPR spectra.
The analysis of the magnetic data shows that compounds
1 and 2 exhibit weak antiferromagnetic (1) and ferromagnetic
(32) (a) Haddad, M. S.; Hendrickson, D. N.; Cannady, J. P.; Drago, R. S.;
Bieksza, D. S. J. Am. Chem. Soc. 1979, 101, 898. (b) Julve, M.;
Verdaguer, M.; Faus, J.; Tinti, F.; Moratal, J.; Monge, A.; Gutie´rrez-
Puebla, E. Inorg. Chem. 1987, 26, 3520.
(33) Estes, W. E.; Gavel, D. P.; Hatfield, W. E.; Hodgson, D. Inorg. Chem.
1978, 17, 1415.
(35) Pasa´n, J.; Delgado, F. S.; Rodr´ıguez-Mart´ın, Y.; Herna´ndez-Molina,
M.; Ruiz-Pe´rez, C.; Sanchiz, J.; Lloret, F.; Julve, M. Polyhedron, 2003,
22, 2143.
(34) Navarro, R. Application of High- and Low-Temperature Series
Expansions to Two-Dimensional Magnetic Systems; de Jongh, L. J.;
Ed., Kluwer: Dodrecht, The Netherlands, 1990.
(36) Rodr´ıguez-Fortea, A.; Alemany, P.; AÄ lvarez, S.; Ruiz, E. Chem.s
Eur. J. 2001, 7, 627.
(37) Kahn, O. Molecular Magnetism; VCH: New York, 1993.
7800 Inorganic Chemistry, Vol. 44, No. 22, 2005

Phenylmalonate-Bridged Cu(II) Complexes
Scheme 1
ally, the layers in 1 are almost planar, whereas they are
corrugated in 2 with angles of 87.8°. The structures of 1
and 2 are also very different from those of the malonate
copper(II) derivatives [Cu(mal)(H2O)(4,4′-bpy)0.5] and
[Cu(mal)(H2O)(2,4′-bpy)], demonstrating that the phenyl ring
of the phenylmalonate exerts important structural effects.
Nevertheless the structure of 2 is similar to that of
[Mn(2,4′-bpy)(mal)(H2O)].31
Under a magnetic point of view, both compounds display
very weak interactions mainly caused by the anti-syn
conformation of the carboxylate bridge. However, compound
2 exhibits a ferromagnetic coupling between the copper(II)
ions, but magnetic ordering down to 2.0 K is not achieved
because of the weak magnetic interaction. It seems interesting
to determine if other potentially bridging ligands such as
pyrazine or pyrimidine lead to similar structures in which
the magnetic coupling could be stronger. The work of our
group will be oriented in that direction trying to increase
the intralayer magnetic coupling and paying attention to the
effect of introducing smaller ligands that may lead to a
shorter interlayer separation.
Acknowledgment. We thank the Ministerio Espan˜ol de
Ciencia y Tecnolog´ıa (Projects CTQ2004-03633 and
BQU2001-3794), the Consejer´ıa de Educacio´n, Cultura y
Deportes of Gobierno Auto´nomo de Canarias (Project
PI2002/175), and the Ministerio Espan˜ol de Educacio´n y
Ciencia (Project MAT2004-03112) for financial support. J.P.
also thanks the Ministerio Espan˜ol de Educacio´n y Ciencia
for a predoctoral fellowship (Ref. AP2001-3322).
a corrugated layer that makes the magnetic orbitals of the
metal ions form an angle of 87.8(4)° in the bridge (Figure
4). This situation leads to a very poor overlap making the
antiferromagnetic contribution very small and causing the
ferromagnetic contribution to be dominant.
Conclusions
Supporting Information Available: Crystallographic data in
CIF format for 1 (CCDC 266328) and 2 (CCDC 266329) and the
Q-band EPR spectra of complex 2 at different temperatures. This
material is available free of charge via the Internet at http://
pubs.acs.org.
The compounds [Cu(4,4′-bpy)(Phmal)]n‚2nH2O (1) and
[Cu(2,4′-bpy)(Phmal)(H2O)]n (2) were prepared, and their
structures and magnetic properties were investigated. Al-
though both compounds are sheetlike polymers, their struc-
tures are very different. There are two bridging ligands in 1
(Phmal and 4,4′-bpy), and only one in 2 (Phmal). Addition-
IC0503986
Inorganic Chemistry, Vol. 44, No. 22, 2005 7801