Synthesis, spectral and magnetical characterization of monomeric [Cu(2-NO2bz)2(3-pyme)2(H2O) 2] and polymeric [Cu{3,5-(NO2)2bz} 2(3-pyme)2]n

Article abstract of DOI:10.1016/j.ica.2005.10.040

Two new complexes of composition [Cu(2-NO₂bz) ₂(3-pyme)₂(H₂O)₂] (1) and/or [Cu{3,5-(NO₂)₂bz}₂(3-pyme)₂] (2) (3-pyme = 3-pyridylmethanol, ronicol or 3-pyridylcarbinol, 2-NO₂bz = 2-nitrobenzoate and 3,5-(NO₂)₂bz = 3,5-dinitrobenzoate) have been prepared and studied by elemental analysis, electronic, infrared and EPR spectroscopy, magnetic susceptibility measurements and the structure of both complexes has been solved. Complex (1) shows an unusual molecular type of structure consisting of the [Cu(2-NO₂bz)₂(3-pyme) ₂(H₂O)₂] molecules held together by hydrogen bonds and van der Waals interactions. Complex (2) exhibits a polymeric chain-like structure [Cu{3,5-(NO₂)₂bz}₂(3-pyme) ₂]_n with copper atoms doubly bridged by two 3-pyridylmethanol molecules and the polymeric molecules are held together by van der Waals interactions. Complex (1) exhibits a magnetic moment μ_eff = 1.84 B.M. at 300 K that remains nearly constant within the temperature region (5-300 K). Further cooling results in lowering the magnetic moment to μ_eff = 1.82 B.M. at 1.8 K. The magnetic susceptibility temperature dependence obeys Curie-Weiss law with Curie constant of 0.423 cm³ K mol^-1 and with Weiss constant of -0.06 K. The magnetic moment of (2) exhibits a small increase with a decrease in the temperature (μ_eff = 1.80 B.M. at 300 K and μ_eff = 1.85 B.M. at 1.8 K) with Curie constant of 0.409 cm³ K mol ^-1 and with Weiss constant of +1.1 K, which can indicate a very weak ferromagnetic interaction between the copper atoms within the chain. Applying the molecular field model resulted in obtaining zJ′ values -0.08 cm ^-1 for complex (1), and -0.07 cm^-1 for complex (2), respectively, that could characterize intermolecular and interchain interactions transmitted through π-π stacking.

Full text of DOI:10.1016/j.ica.2005.10.040

Inorganica Chimica Acta 359 (2006) 1275–1281
www.elsevier.com/locate/ica
Synthesis, spectral and magnetical characterization of
monomeric [Cu(2-NO2bz)2(3-pyme)2(H2O)2] and polymeric
[Cu{3,5-(NO2)2bz}2(3-pyme)2]n
a,
b
a
a
b
*
´
´
P. Stachova , M. Korabik , M. Koman , M. Melnık , J. Mrozinski ,
b
c
a
T. Glowiak , M. Mazu´r , D. Valigura
a
Department of Inorganic Chemistry, Faculty of Food and Chemical Technology, Slovak Technical University, Radlinske´ho 9, 812 37 Bratislava, Slovakia
b
Faculty of Chemistry, University of Wroclaw, 50-383 Wroclaw, Poland
Department of Physical Chemistry, Slovak Technical University, Radlinske´ho 9, 812 37 Bratislava, Slovakia
c
Received 15 August 2005; received in revised form 19 October 2005; accepted 21 October 2005
Available online 2 December 2005
Abstract
Two new complexes of composition [Cu(2-NO2bz)2(3-pyme)2(H2O)2] (1) and/or [Cu{3,5-(NO2)2bz}2(3-pyme)2] (2) (3-pyme = 3-pyr-
idylmethanol, ronicol or 3-pyridylcarbinol, 2-NO2bz = 2-nitrobenzoate and 3,5-(NO2)2bz = 3,5-dinitrobenzoate) have been prepared
and studied by elemental analysis, electronic, infrared and EPR spectroscopy, magnetic susceptibility measurements and the structure
of both complexes has been solved. Complex (1) shows an unusual molecular type of structure consisting of the [Cu(2-NO2bz)2(3-
pyme)2(H2O)2] molecules held together by hydrogen bonds and van der Waals interactions. Complex (2) exhibits a polymeric chain-like
structure [Cu{3,5-(NO2)2bz}2(3-pyme)2]n with copper atoms doubly bridged by two 3-pyridylmethanol molecules and the polymeric mol-
ecules are held together by van der Waals interactions. Complex (1) exhibits a magnetic moment leff = 1.84 B.M. at 300 K that remains
nearly constant within the temperature region (5–300 K). Further cooling results in lowering the magnetic moment to leff = 1.82 B.M. at
1.8 K. The magnetic susceptibility temperature dependence obeys Curie–Weiss law with Curie constant of 0.423 cm3 K molꢀ1 and with
Weiss constant of ꢀ0.06 K. The magnetic moment of (2) exhibits a small increase with a decrease in the temperature (leff = 1.80 B.M. at
300 K and leff = 1.85 B.M. at 1.8 K) with Curie constant of 0.409 cm3 K molꢀ1 and with Weiss constant of +1.1 K, which can indicate a
very weak ferromagnetic interaction between the copper atoms within the chain. Applying the molecular field model resulted in obtaining
zJ0 values ꢀ0.08 cmꢀ1 for complex (1), and ꢀ0.07 cmꢀ1 for complex (2), respectively, that could characterize intermolecular and inter-
chain interactions transmitted through p–p stacking.
ꢀ 2005 Elsevier B.V. All rights reserved.
Keywords: Copper; Carboxylate complexes; Crystal structure; Spectral properties; Magnetic properties; Pyridylmethanol
1. Introduction
complexes of stoichiometry [Cu(RCO2)2(3-pyme)2] that
are one-dimensional chain-like [2–4], or two-dimensional
sheet-like [5–7] polymeric ones. According to our knowl-
edge, up to now the only one ‘‘low molecular’’ carboxyla-
tocopper(II) 3-pyridylmethanol complex is known – dimeric
[Cu2(ac)4(3-pyme)2] Æ CH2Cl2 (where ac = acetate) [1], and
the only one known monomeric complex is [CuCl2(3-
pyme)4] [8]. In this paper, we present our results on the
structural, spectroscopic and magnetic properties of two
The interaction of the copper(II) atom, which plays a
vital role in a number of quite different biological processes
with therapeutically administered drugs is a subject of con-
siderable interest. 3-Pyridylmethanol is one of the very
interesting anti-inflammatory agents [1]. It is well known
as a ligand that usually forms carboxylatocopper(II)
*
3-pyridylmethanol
complexes
[Cu(2-NO2bz)2(3-
Corresponding author. Tel.: +421 2 59325611; fax: +421 2 52493198.
pyme)2(H2O)2] (1) and [Cu{3,5-(NO2)2bz}2(3-pyme)2]n (2).
´
E-mail address: petra.stachova@stuba.sk (P. Stachova).
0020-1693/$ - see front matter ꢀ 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2005.10.040

1276
P. Stachova´ et al. / Inorganica Chimica Acta 359 (2006) 1275–1281
pffiffiffiffiffiffiffiffi
2.4. X-ray crystallography
2. Experimental
2.1. Complex preparation
leff ¼ 2:83 vmT ðB.M.Þ
Both complexes were prepared in the same way by the
reaction of an aqueous solution of copper(II) acetate
(1 mmol) with 3-pyridylmethanol (2 mmol) followed by
the addition of the appropriate acid (2 mmol). The reaction
mixture was stirred until a light blue product was precipi-
tated. The microcrystalline product was filtered off, washed
with small portion of water and dried at ambient tempera-
ture. The light blue mother liquids obtained after filtration
were left for crystallization and blue crystals suitable for X-
ray structure determination were obtained after a few days.
The compositions of powder products were according to
the elemental analysis the same as that of the crystals
(proved by X-ray structure analysis).
Data collection and cell refinement of the presented
complexes were carried out using Kuma KM4 diffractom-
eter [10]. Intensity data were corrected for Lorentz and
polarization factors. The structure was solved by the heavy
atom method using SHELX86 [11], and subsequent Fourier
synthesis using SHELXS93 [12]. Geometrical analysis was
performed using SHELXL97 [13] and the structure was drawn
using ORTEP-3 for Windows program [14]. Final crystal
data and structure refinement parameters are given in
Table 1.
3. Results and discussion
Anal. Calc. for Cu(2-NO2bz)2(3-pyme)2 Æ 2H2O: Cu,
9.76; C, 47.97; H, 4.18; N, 8.61. Found: Cu, 9.36; C,
48.13; H, 3.81; N, 9.02%.
Anal. Calc. for Cu{3,5-(NO2)2bz}2(3-pyme)2: Cu, 9.03;
C, 44.36; H, 2.86; N, 11.94. Found: Cu, 9.27; C, 44.41;
H, 2.87; N, 12.05%.
3.1. Structure determination
The principal structural features and atom numbering
scheme of (1) are depicted in Fig. 1 and selected bond
distances and angles are listed in Table 2. The structure
consists of the centrosymmetric molecules in which two
2-nitrobenzoato anions via O1 oxygen atoms (Cu–O1
2.2. Analytical methods
Carbon, hydrogen and nitrogen analyses were carried
out on a CHNSO FlashEA 1112 (ThermoFinnigan)
elemental analyzer. Copper was determined by the elec-
trolysis of water solution obtained by the sample mineral-
ization with a mixture of sulfuric acid and potassium
peroxodisulfate.
Table 1
Crystal data and structure refinement for [Cu2(2-NO2bz)2(3-
pyme)2(H2O)2] (1) and [Cu{3,5-(NO2}2bz)2(3-pyme)2]n (2) complexes
Identification code
Empirical formula
Formula weight
Temperature (K)
tg23
tg31a
C26H20N6O14Cu
642.02
293(2)
0.71073
triclinic
C
26H26N4O12Cu
650.05
293(2)
0.71073
triclinic
2.3. Physical measurement
˚
Wavelength (A)
Crystal system
Space group
Unit cell dimensions
ꢀ
ꢀ
P1
P1
Electronic spectra (190–1100 nm) of the complexes were
measured in Nujol suspension with a SPECORD 200 (Carl
Zeiss Jena) spectrophotometer, and infrared spectrum in
the region of 4000–100 cmꢀ1 were measured with a Nicolet
MAGNA 750 IR spectrometer using both KBr pellet and
Nujol suspension techniques for 4000–400 cmꢀ1 region
and Polyethylene pellet for 400–100 cmꢀ1 region.
EPR spectra of the powdered sample were recorded at
room temperature and at 77 K, on Bruker ESP 300 spec-
trometer, operating at X-band equipped with an ER
035M Bruker NMR gaussmeter and a HP 5350B Hew-
lett–Packard microwave frequency counter.
˚
a (A)
7.6050(8)
8.7746(10)
10.9461(11)
86.231(9)
73.063(10)
68.867(11)
651.13(12)
1
1.658
0.916
335
3.9–28.30
4460
7.6180(15)
8.2320(16)
12.288(3)
87.21(3)
72.07(3)
66.48(3)
669.8(2)
1
1.745
0.905
˚
b (A)
˚
c (A)
a (ꢁ)
b (ꢁ)
c (ꢁ)
3
˚
Volume (A )
Z
Dcalc (Mg/m3)
Absorption coefficient (mmꢀ1
F(000)
)
359
3.35–28.43
4614
h Range for data collection (ꢁ)
Reflection collected
Magnetic susceptibility measurements in the tempera-
ture range of 1.8–300 K were carried out on powdered sam-
ples of complexes, at the magnetic field 0.5 T, using a
Quantum Design SQUID Magnetometer (type MPMS-
XL5). Corrections for diamagnetism of the constituting
atoms were calculated using the Pascal constants [9], the
value of 60 · 10ꢀ6 cm3 molꢀ1 was used as the tempera-
ture-independent paramagnetism of copper(II) ion. The
effective magnetic moments were calculated from the
expression:
Independent reflections
Refinement method
2856
2939
full matrix least
squares on F2
2856/0/248
1.086
R1 = 0.0274,
wR2 = 0.0700
R1 = 0.0289,
wR2 = 0.0711
0.377 and ꢀ0.667
full matrix least
squares on F2
2939/0/254
1.061
R1 = 0.0281,
wR2 = 0.0715
R1 = 0.0313,
wR2 = 0.0731
0.367 and ꢀ0.589
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices [I > 2r(I)]
R indices (all data)
Largest difference in peak
3
˚
and hole (e A )

P. Stachova´ et al. / Inorganica Chimica Acta 359 (2006) 1275–1281
1277
the neighbouring complex molecule with a O6–H2O6 dis-
ii
ii
˚
˚
tance of 0.799 A, H2O6ꢁ ꢁ ꢁO5 distance of 1.920 A, O5 –
ii
ii
iv
˚
H1O5 distance of 0.793 A and H1O5 ꢁ ꢁ ꢁO6 distance of
˚
2.038 A (where ii = x, y + 1, z, and iv = ꢀx + 1, ꢀy ꢀ 2,
ꢀz).
The mutual positions of complex molecules (1) within
the structure lead to the coplanarity of the coordinated 3-
pyridylmethanol molecules (Fig. 2) with similar interplane
˚
distances 3.553(3), and 3.516(3) A, respectively. The con-
stant angle between 3-pyridylcarbinol pyridine ring and
2-nitrobenzoate anion benzene ring (84.51(5)ꢁ) results in
the coplanarity between 2-nitrobenzoate anions too. The
interplanar distance between the benzene rings stacked
one over the other (e.g., i = ꢀx, ꢀy, ꢀz and vii = x ꢀ 1,
y, z + 1 or vi = ꢀx, ꢀy + 1, ꢀz and ix = x ꢀ 1, y + 1,
˚
z + 1) is 3.413(3) A. The other interplanar distance between
a pair of 2-nitrobenzoate anion benzene rings (vii = x ꢀ 1,
y, z + 1 and vi = ꢀx, ꢀy + 1, ꢀz) is even lesser
˚
(3.124(3) A), but their mutual positions do not allow any
interaction to take place. The data shown in Table 3 help
us to conclude that only two out of the four mutual posi-
tions of the aromatic rings could be taken as p–p stacking
˚
(d(centre–centre) < 3.8 A and d < 30ꢁ) [15].
The molecular structure of (2) with the atom number-
ing scheme of independent part is shown in Fig. 3. The
independent part of the molecule consists of the copper
atom centrosymmetrically bonded with two monodentate
3,5-dinitrobenzoato anions via oxygen O1 atoms (Cu1–
Fig. 1. Structure of [Cu(2-NO2bz)2(3-pyme)2(H2O)2] (1) with the non-
hydrogen atom numbering of independent part.
˚
distances are of 1.970(1) A), two 3-pyridylmethanol mole-
cules via N2 nitrogen atoms and two water molecules via
˚
O1 distances are 1.952(1) A) and two 3-pyridylmethanol
˚
O6 oxygen atom (Cu–O6 distances are of 2.392(1) A) are
molecules bonded via nitrogen N6 atoms (Cu1–N6
bonded to copper atom in trans-positions. The significantly
smaller O1–Cu–O6 angle value (Table 2) is caused by the
relatively strong intramolecular hydrogen bonds O6–
H1O6ꢁ ꢁ ꢁO2i and O6i–H1O6iꢁ ꢁ ꢁO2 (i = ꢀx,ꢀy,ꢀz) between
H1O6 and H1O6i hydrogen atoms of the water molecules
and the other O2i and O2 atoms of 2-nitrobenzoato anions
˚
distances are 2.035(1) A). The coordination polyhedron
of the Cu1 atom is by two oxygen O4 atoms of the neigh-
bouring 3-pyridylmethanol hydroxy groups (Cu1–O4
˚
distances are 2.465(1) A) completely distorted octahedral
coordination sphere geometry. The pairs of 3-pyridyl-
methanol bridge each pair of adjacent copper atoms
(Fig. 4) and as a result an infinite linear chain of doubly
bridged copper atoms is formed. The strong intramolecu-
lar hydrogen bonds between each 3-pyridylmethanol OH
group and the oxygen O3 atom of the coordinated car-
boxylate group O4–H10ꢁ ꢁ ꢁO3 (O4–H10 distance is
i
˚
(O6–H1O6 distance of 0.835 A, and H1O6ꢁ ꢁ ꢁO2 distance
˚
of 1.869 A), that are together with intermolecular hydrogen
bonds keeping the water molecules slightly moved from
precise apical positions. The system of the intermolecular
hydrogen bonds is depicted in Fig. 2 and covers the O6,
H2O6, O5ii, H1O5ii and finally reaches the O6iv atom of
˚
˚
0.829 A, and H10ꢁ ꢁ ꢁO distance is 2.028 A) stabilize the
chain structure (Fig. 4). The infinite chains are collinear
with the a axis and the mutual position of chains within
the ab plane layer allows the p–p stacking of the coplanar
pyridine rings of the neighbouring infinite chains (Table
Table 2
Selected bond distances and angles for complexes under study
[Cu(2-NO2bz)2(3-pyme)2-
[Cu{3,5-(NO2)2bz}2(3- pyme)2]n
˚
4) with a plane–plane distance of 3.406(4) A and the
(H2O)2] (1)
(2)
‘‘displacement’’ angle d value of 20.0ꢁ. The mutual orien-
tation of pyridine ring within the chain is coplanar too,
showing a very small value of plane to plane distance
(Table 4), but the displacement angle is far beyond the
value accepted for the p–p stacking [15]. The polymeric
chains are within the ac plane fixed in the form of ‘‘zip-
like’’ structure by the coplanar 3,5-dinitrobenzoato anions
bonded to copper atoms of the neighbouring chains that
allow another p–p stacking of the neighbouring infinite
chains components (Table 4).
˚
˚
1.952(1) A
Cu–O1
Cu–N2
Cu–O6
1.971(1) A
Cu1–O1
Cu1–N6
Cu1–O4
O1–Cu1–N6
O1–Cu1–O4j
N6–Cu1–O4j
O3–O4j
˚
˚
2.056(1) A
2.035(1) A
˚
˚
2.392(1) A
2.465(1) A
O1–Cu–N2
O1–Cu–O6
O1–Cu–O6i
N2–Cu–O6
O6ꢁ ꢁ ꢁO2i
O6ꢁ ꢁ ꢁO5ii
O5ꢁ ꢁ ꢁO6iii
i
91.55(5)ꢁ
86.21(4)ꢁ
93.79(4)ꢁ
86.63(5)ꢁ
2.684
90.24(6)ꢁ
95.54(5)ꢁ
85.37(5)ꢁ
2.753
2.717
2.783
ꢀx, ꢀy, ꢀz; ii x, y + 1, z; ꢀx + 1, ꢀy ꢀ 1, ꢀz; x ꢀ 1, y, z.
iii
j

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P. Stachova´ et al. / Inorganica Chimica Acta 359 (2006) 1275–1281
Fig. 2. The view (approximately along the c axis) on the structure of [Cu(2-NO2bz)2(3-pyme)2(H2O)2] with the hydrogen bonds system.
Table 3
3.2. Magnetic and spectral properties
Mutual positions of coplanar aromatic rings in complex 1 structure
Aromatic
ring 1
Aromatic
ring 2
d(plane–plane)
(A)
d(centre–centre)
(A)
Anglea
d (ꢁ)
The data of susceptibility measurements are illustrated
in Figs. 5 and 6, in the form of vm and vmT versus T (vm
being the corrected molar magnetic susceptibility per CuII
and T the absolute temperature). The vmT value of the
monomeric Cu(2-NO2bz)2(3-pyme)2(H2O)2 complex is
equal to 0.422 cm3 K molꢀ1 (leff = 1.84 B.M.) at room
temperature and practically does not change with the low-
ering of temperature up to 5 K, but only a weak change in
the lowest temperatures (Fig. 5) to the value
0.411 cm3 K molꢀ1 (leff = 1.82 B.M.) at 1.8 K is observed.
The inverse magnetic susceptibility versus temperature of
this complex is in good agreement with the Curie–Weiss
law, v = C/(T ꢀ h) [9], and gives C = 0.423 cm3 K molꢀ1
and h = ꢀ0.06 K. This very small value of Weiss constant
h is not negligible because of the reach system of p–p inter-
actions, which connects complex molecules in the crystal
lattice. In order to obtain values of the magnetic exchange
parameters, the present magnetic data of complex (1) have
been fit using magnetic centres (S = 1/2) in the molecular
field model of magnetic interactions [16]:
˚
˚
Pyridinei
Pyridineii
Benzenei
Benzenevii
i
pyridineii
pyridinev
benzenevii
benzenevi
3.553(3)
3.516(3)
3.413(3)
3.124(3)
v
4.903(3)
3.745(3)
3.604(4)
5.643(5)
43.6
20.1
18.7
56.4
vi
ꢀx, ꢀy, ꢀz; ii x, y + 1, z; ꢀx + 1, ꢀy, ꢀz; vii x ꢀ 1, y, z + 1; ꢀx,
ꢀy + 1.
a
Angle d = angle between centre–centre line and normal to plane line.
In spite of differences in the size of both complex mole-
cules (molecular or polymeric chains), the presented struc-
tures are very similar from the point of view of copper to
copper distances (see Table 1 for comparison of structural
parameters) and exhibit nearly the same condition to p–p
stacking (compare Tables 3 and 4). The understanding of
a weak magnetic interaction transmitted through p–p
stacking, or via other interactions (C–Hꢁ ꢁ ꢁp interactions
or ion–p interactions) attracted considerable interests for
their role in crystal engineering and in the stability of metal
complexes, and it was proposed that such interactions can
play a role in the mechanism of enzymatic reactions [15,19].
The understanding and utilization of all non-covalent
interactions including p–p stacking is of fundamental
importance for the further development of inorganic supra-
molecular chemistry and our both complexes although
their structural differences seem to be a good subject for
the study of magnetic interactions.
Nb2g2
3kT
vm
vm ¼
SðS þ 1Þ;
vcmorr
¼
;
ð1Þ
2zJ0vm
1 ꢀ
Ng2b2
where zJ0 is the molecular exchange parameter and z
is the number of the nearest neighbours. A spectroscopic
splitting factor g was obtained in the fitting process. The
satisfactory least-squares fit to the experimental results

P. Stachova´ et al. / Inorganica Chimica Acta 359 (2006) 1275–1281
1279
Fig. 3. The structure of [Cu{3,5-(NO2)2bz}2(3-pyme)2]n with an independent part atom numbering. The neighbouring units OH groups are shown to
complete the coordination polyhedron (j = x ꢀ 1, y, z and jj = ꢀx + 1, ꢀy, ꢀz).
Fig. 4. The structure of [Cu{3,5-(NO2)2bz}2(3-pyme)2]n showing the chain (along the a axis) and intramolecular hydrogen bonds formation. (j = x ꢀ 1, y,
z and jjj = ꢀx, ꢀy, ꢀz).
(solid lines in Fig. 5) was obtained for zJ0 = ꢀ0.08 cmꢀ1
,
2
exp
n
ðvi T ꢀ vci alcTÞ
X
g = 2.13, with R = 3.13 · 10ꢀ5. R is the agreement factor
R ¼
.
ð2Þ
2
ðvT ei xp
Þ
defined as
i¼1

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P. Stachova´ et al. / Inorganica Chimica Acta 359 (2006) 1275–1281
Table 4
Weiss constant confirms the existence of a very weak ferro-
magnetic interaction among CuII ions in the crystal lattice.
The differences in the magnetic behaviour of (2) in com-
parison to the behaviour of complex (1) cannot be satisfac-
torily explained by the Cu–Cu distances within the
structures and by the p–p interactions, because those
parameters for both the studied complexes are nearly the
same. The main difference in their structures is that in com-
plex (2) each of the pairs of 3-pyridylmethanol bridge two
adjacent copper atoms (Fig. 4) and thus the infinite linear
chain of doubly bridged copper atoms is formed. Magnetic
data were analysed using the Ising expression [16]:
Mutual positions of coplanar aromatic rings in complex 2 structure
Aromatic
ring 1
Aromatic
ring 2
d(plane–plane)
(A)
d(centre–centre)
(A)
Anglea
d (ꢁ)
˚
˚
Pyridinejjj
Pyridinej
Benzenejjj
Benzenevjj
pyridinevj
pyridinejjj
benzenevjj
benzenejx
3.406(4)
2.641(3)
2.860(4)
3.558(5)
3.625(4)
5.626(3)
5.403(4)
3.826(5)
20.0
62.0
58.0
21.6
j x ꢀ 1, y, z; jjj ꢀx, ꢀy, ꢀz; vj x ꢀ 1, y + 1, z; vjj x, y, z + 1; jx ꢀx + 1, ꢀy, ꢀz.
a
Angle d = angle between centre–centre line and normal to plane line.
0.3
0.25
0.2
0.5
0.4
0.3
0.2
0.1
0
Ng2b2
4kT
vm ¼
expðꢀJ=kT Þ
ð3Þ
for infinite chains of CuII ions, the J value characterizes
intrachain interactions, the spin Hamiltonian is defined as
H = ꢀJRSiSi + 1. The molecular term vcmorr-the same as in
Eq. (1), was added to describe interchain interactions
through p–p stacking system, to compare it with that found
for complex (1). In this case, vm is the molar susceptibility
given by Isingꢀs expression, zJ0 characterizes interchain
interaction among z CuII neighbours. A least-square fit of
the data leads to the values of J = +0.12 cmꢀ1, zJ0 = ꢀ0.07
cmꢀ1, R = 1.53 · 10ꢀ4. Magnetic measurements and calcu-
lations agree well with the crystal structure parameters. In
the case of complex 2, copper(II) atoms form polymeric
chains and very weak ferromagnetic interactions within
the chain showing J = +0.12 cmꢀ1 (h = +1.1 K). Very
weak antiferromagnetic interactions in both complexes
(1) and (2) are related to similar Cu–Cu distances as well
as to nearly the same p–p distances and angles. However,
the interactions transmitted through p–p stacking are
now in the same range (|zJ0| values are in both cases below
0.1 cmꢀ1) and the calculations for a typical aromatic p–p
0.15
0.1
0.05
0
0
100
200
300
400
T (K)
Fig. 5. Plots of vm and vmT vs. T for [Cu(2-NO2bz)2(3-pyme)2(H2O)2]
complex. Solid lines present calculated curves using magnetic centres
(S = 1/2) in the molecular field model of magnetic interactions. Obtained
parameters are: g = 2.13, zJ0 = ꢀ0.08, R = 3.13 · 10ꢀ5
.
0.3
0.25
0.2
0.5
0.4
0.3
0.2
0.1
0
0.15
0.1
0.05
0
stacking [15,17–21] gave an energy of about 2 kJ molꢀ1
.
0
50
100 150 200 250 300 350
T (K)
Both complexes exhibit EPR spectra of axial symmetry
with g^ = 2.063 and gi = 2.400 for complex (1) or
g^ = 2.055 and gi = 2.350 for complex (2) and are in good
agreement with the data obtained by evaluation of mag-
netic data.
Fig. 6. Plots of vm and vmT vs. T for [Cu{3,5-(NO2}2bz)2(3-pyme)2]n
complex. Solid lines present magnetic calculated data to the model of Ising
chain expression. A molecular field term was added to describe interchain
interactions. Parameters obtained: g = 2.10, J = +0.12 cmꢀ1, zJ0 = ꢀ0.07
cmꢀ1, R = 1.53 · 10ꢀ4
.
The infrared as well as electronic spectra are different.
While the maximum of the d d transitions (for complex
(1) it was found at 672 nm, for the polymeric complex (2) it
was found at 630 nm). The difference between asymmetric
and symmetric COO vibrations of carboxylic group is
The magnetic measurements of the [Cu{3,5-(NO2)2bz}2(3-
pyme)2]n complex show very weak ferromagnetic interac-
tions among the CuII ions. The vmT value equals
0.405 cm3 K molꢀ1 at room temperature, and weakly but
systematically increases with the lowering of temperature
(Fig. 4) up to 0.428 cm3 K molꢀ1 at 1.8 K. This indicates
a very weak ferromagnetic interaction among CuII ions
within the structure. The magnetic susceptibility results
for complex (2) obey the Curie–Weiss law within the tem-
perature range 1.8–300 K, vm = C/(T ꢀ h), where the Curie
constant C = Ng2b2S(S + 1)/3k and S = 1/2. The best val-
ues of the Curie (C) and Weiss (h) constant values are:
C = 0.409 cm3 K molꢀ1 and h = +1.1 K. The positive
219 cmꢀ1 (mas(COO) = 1601 cmꢀ1, ms(COO) = 1382 cmꢀ1
)
for complex (1) and it is in good agreement with the
monodentate binding mode [22]. Similarly, for complex
(2) the observed value Dm(COO) = 194 cmꢀ1 (mas(COO) =
1633 cmꢀ1 ms(COO) = 1439 cmꢀ1
) also confirmed the
monodentate bonding mode. Mutual orientation of the
nitro-group to the aromatic ring could be evaluated on
the basis of NOO vibrations. Deviation of the nitro-group
from a coplanar position results in the decrease of symmet-
ric NOO vibration wavenumbers and for nearly coplanar
orientation of NO2 in complex (2) ms(NOO) was found at

P. Stachova´ et al. / Inorganica Chimica Acta 359 (2006) 1275–1281
1281
1345 cmꢀ1, while in the case of monomeric complex (1)
with the NO2-benzene ring angle of 62.7ꢁ the ms(NOO)
´ˇ
´
´
[5] N.N. Hoang, F. Valach, Lꢀ. Macaskova, M. Melnık, Acta Crystal-
logr. C48 (1992) 1933.
´
[6] J. Moncolꢀ, M. Koman, M. Melnık, T. Glowiak, CrystEngComm 3
was found at 1330 cmꢀ1
.
(2001) 262.
ˇ
´
ˇ
´
[7] S. Lo¨rincz, M. Koman, M. Melnık, J. Moncolꢀ, D. Ondrusova, Acta
4. Supplementary material
Crystallogr. E60 (2004) m590.
[8] J. Moncolꢀ, M. Mu´dra, P. Lonnecke, M. Koman, M. Melnik, J.
Chem. Cryst. 34 (2004) 423.
Supplementary material including all atomic coordinates
(104·), anisotropic displacement parameters for non–hydro-
gen atoms and all interatomic distances and bond angles
have been deposited with the Cambridge Crystallographic
Centre, CCDC No. 280607 for the compound [Cu-
(2-NO2bz)2(3-pyme)2(H2O)2] (1) and CCDC No. 280608
for the compound [Cu{3,5-(NO2)2bz}2(3-pyme)2]n (2). Cop-
ies of this information may be obtained free of charge from
The Director, CCDC, 12 Union Road, Cambridge, CB2
1EZ, UK: fax: +44 1223 366 033, e-mail: deposit@ccdc.
ac.uk or on the web www: http://www.ccdc.cam.ac.uk.
[9] E. Ko¨nig, Magnetic Properties of Coordination and Organometallic
Transition Metal Compounds, Springer, Berlin, 1966.
[10] Kuma Diffraction, KM4CCD System Software, Version 1.149 Kuma
Difraction Instruments and Universite de Lausanne Switzerland,
1998.
[11] G.M. Sheldrick, in: G.M. Sheldrick, C. Kruger, R. Goddard (Eds.),
¨
SHELXS86. Crystallographic Computing, vol. 3, Oxford University
Press, 1985, pp. 175–189.
[12] G.M. Sheldrick, SHELXL93. Program for Refinement of Crystal
Structure, Institut Anorg. Chemie, Univ. of Go¨ttingen, D37077
Go¨ttingen, Germany, 1993.
[13] G.M. Sheldrick, SHELXL97. Program for Refinement of Crystal
Structure, Institut Anorg. Chemie, Univ. of Go¨ttingen, D37077
Go¨ttingen, Germany, 1997.
Acknowledgements
[14] L.J. Farrugia, J. Appl. Cryst. 30 (1997) 565.
[15] C. Janiak, J. Chem. Soc., Dalton Trans. (2000) 3885.
[16] O. Kahn, Molecular Magnetism, VCV Publishers, New York,
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[17] A.J. Costa-Filho, O.R. Nascimento, L. Ghivelder, R. Calvo, J. Phys.
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[18] V. Ryzhov, R.C. Dunbar, J. Am. Chem. Soc. 121 (1999) 2259.
This work was supported by the VEGA Grant 1/2452/
05 and by the Polish Ministry of Science and Compute-
rization.
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