Oxalato complexes of copper(II) with chelating diamines. Crystal structure of [Cu(dmen)ox(H2O)]2[Cu(dmen)2] (ClO4)2

Article abstract of DOI:10.1016/S0277-5387(02)01000-8

Four new oxalato complexes of copper(II) of composition [Cu(dmen)ox(H₂O)]₂ [Cu(dmen)₂](ClO₄)₂ (1) (dmen = N,N-dimethylethylenediamine, H₂ox = oxalic acid), [(Cu(dmen)H₂O)₂ox](ClO₄)₂ ·H₂O (2), [Cu(tmen)(H₂O)(ox)Cu(aep)(H₂O)] (ClO₄)₂ (3) (tmen = N,N,N′,N′-tetramethylethylenediamine, aep = 2-(2-aminoethyl)pyridine) and [(Cu(dben)NO₃)₂ox] (4) (dben = N,N′-dibenzylethylenediamine) have been prepared and characterised by IR and UV-Vis spectroscopies and magnetic measurements. The crystal structure of [Cu(dmen)ox(H₂O)]₂[Cu(dmen)₂] (CO₄)₂ (1) has been determined by single-crystal X-ray analysis. The structure of 1 contains a neutral [Cu(dmen)ox(H₂O)] complex, a cationic [Cu(dmen)₂]²⁺ complex and perchlorate anions. The copper(II) atom of the neutral [Cu(dmen)ox(H₂O)] unit possesses a distorted square-pyramidal environment with two oxygen atoms of oxalate and two nitrogen atoms of dmen in the basal plane and an oxygen atom of a water molecule in the apical position. The copper(II) atom of the cationic [Cu(dmen)₂] unit shows a square-planar environment with four donor nitrogen atoms of two molecules of dmen. The temperature dependence of magnetic susceptibility for compounds 2-4 was measured. Magnetochemical measurements show that copper(II) ions in compounds 2-4 are antiferromagnetically coupled through the oxalate bridge, J = - 157, -175 and - 167 cm^-1 (H = -2JS₁S₂, S₁ = S₂ = 1/2) for 2, 3 and 4, respectively.

Full text of DOI:10.1016/S0277-5387(02)01000-8

Polyhedron 21 (2002) 1203ꢁ1209
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Oxalato complexes of copper(II) with chelating diamines. Crystal
structure of [Cu(dmen)ox(H2O)]2[Cu(dmen)2](ClO4)2
Zdeneˇk Sme´kal a,*, Jirˇ´ı Kamen´ıcˇek a, Petra Klasova´ a, Grzegorz Wrzeszcz b,
a
Zdeneˇk Sindela´rˇ , Pavel Kopel , Zdirad Za´k
a
c
ˇ
ˇ
a Department of Inorganic and Physical Chemistry, Palacky´ University, Krˇ´ızˇkovske´ho 10, 771 47 Olomouc, Czech Republic
b Faculty of Chemistry, Nicholas Copernicus University, Gagarina 7, 87-100 Torun´, Poland
c Department of Inorganic Chemistry, Masaryk University, Kotla´rˇska´ 2, 611 37 Brno, Czech Republic
Received 26 October 2001; accepted 19 February 2002
Abstract
Four new oxalato complexes of copper(II) of composition [Cu(dmen)ox(H2O)]2 [Cu(dmen)2](ClO4)2 (1) (dmenꢀ
dimethylethylenediamine, H2oxꢀoxalic acid), [(Cu(dmen)H2O)2ox](ClO4)2×H2O (2), [Cu(tmen)(H2O)(ox)Cu(aep)(H2O)](ClO4)2
(3) (tmenꢀN,N,N?,N?-tetramethylethylenediamine, aepꢀ2-(2-aminoethyl)pyridine) and [(Cu(dben)NO3)2ox] (4) (dbenꢀN,N?-
dibenzylethylenediamine) have been prepared and characterised by IR and UVꢁVis spectroscopies and magnetic measurements.
/N,N-
/
/
/
/
/
/
The crystal structure of [Cu(dmen)ox(H2O)]2[Cu(dmen)2](ClO4)2 (1) has been determined by single-crystal X-ray analysis. The
structure of 1 contains a neutral [Cu(dmen)ox(H2O)] complex, a cationic [Cu(dmen)2]2ꢂ complex and perchlorate anions. The
copper(II) atom of the neutral [Cu(dmen)ox(H2O)] unit possesses a distorted square-pyramidal environment with two oxygen atoms
of oxalate and two nitrogen atoms of dmen in the basal plane and an oxygen atom of a water molecule in the apical position. The
copper(II) atom of the cationic [Cu(dmen)2] unit shows a square-planar environment with four donor nitrogen atoms of two
molecules of dmen. The temperature dependence of magnetic susceptibility for compounds 2ꢁ
measurements show that copper(II) ions in compounds 2ꢁ4 are antiferromagnetically coupled through the oxalate bridge, Jꢀ
157, ꢃ175 and ꢃ 2JS1S2, S1ꢀS2ꢀ1/2) for 2, 3 and 4, respectively. # 2002 Elsevier Science Ltd. All rights
167 cmꢃ1 (Hꢀ
reserved.
/4 was measured. Magnetochemical
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ꢃ
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Keywords: Copper(II) complexes; Oxalato complexes; Oxalato-bridged complexes; Magnetic properties; Crystal structures
1. Introduction
structurally characterised and it was found copper(II)
can be five- or six-coordinated [2ꢁ30]. It was demon-
strated that m-oxalato-dicopper(II) complexes possesses
J-values approximately from 0 to ꢃ
200 cmꢃ1 (Hꢀ
2JS1S2, S1ꢀS2ꢀ1/2). Further, it is known that
/
Binuclear copper(II) complexes with the oxalate
dianion (ox) acting as a bis-bidentate bridging ligand
are suitable model compounds for magneto-structural
correlations. General trends of magnetic behaviour of
these compounds are well established, the oxalate bridge
being very efficient in transmission of the antiferromag-
netic interactions between the two copper(II) atoms.
Julve at al. [1,2] described a theory predicting the
magnetic interactions in oxalato bridged Cu(II) com-
plexes. Many binuclear copper(II) mixed-ligand com-
plexes with oxalate as bridging ligand have been
/
/
ꢃ
/
/
/
complexes with tetragonal pyramidal geometry at both
copper centres with oxalate coordinated in the basal
plane give rise to J-values near
[2,6,8,11,13,24,25,28ꢁ30]. A weak interaction (the ob-
served J-values are in the range from ꢂ1.1 to ꢃ37.4
ꢃ
200 cmꢃ1
/
/
/
/
cmꢃ1) was found in the case of octahedral, trigonal
bipyramidal or tetragonal pyramidal (with one oxygen
atom of oxalate coordinated in the basal plane and the
other in the apical position) arrangements of copper(II)
atoms [9,17,23,25]. Recently, we prepared and charac-
terised binuclear m-oxalato copper(II) complexes
* Corresponding author. Tel.: ꢂ
522-5737.
E-mail address: smekal@risc.upol.cz (Z. Sme´kal).
/
420-68-563-4352; fax: ꢂ420-68-
/
[(Cu(1,3-pn))2ox](ClO4)2 (1,3-pnꢀ1,3-diaminopropane)
/
0277-5387/02/$ - see front matter # 2002 Elsevier Science Ltd. All rights reserved.
PII: S 0 2 7 7 - 5 3 8 7 ( 0 2 ) 0 1 0 0 0 - 8

1204
Z. Sme´kal et al. / Polyhedron 21 (2002) 1203ꢁ1209
/
(Jꢀ
aminoethyl)-1,3-diaminopropane)
H2O)2ox](NO3)2 (aepꢀ2-(2-aminoethyl)pyridine) (Jꢀ
160 H2O [28],
cmꢃ1),
[(Cu(ept))2ox](NO3)2×
3,3?-diamino-N-
cmꢃ1),
[(Cu-
2.6 cmꢃ1),
(trimeenꢀ
172 cmꢃ1),
168 cmꢃ1
H2O (dietenꢀN,N?-
172 cmꢃ1) [30].
/
ꢃ
/
127 cmꢃ1), [(Cu(ept))2ox](ClO4)2 (eptꢀ
[31], [(Cu(aep)-
/
N-(2-
off and dried at 35 8C under an infralamp). N,N-
dimethylethylenediamine, N,N?-dibenzylethylenedia-
mine and 2-(2-aminoethyl)pyridine (Aldrich), sodium
oxalate and Cu(NO3)2×3H2O (Lachema Brno) and
KOCN (Fluka) were used without further purification.
Compound [Cu(tmen)ox]×4H2O was prepared according
to the literature [2].
Elemental analyses (C, H, N) were performed on a
Fisons EA1108 CHN instrument. Absorption UVꢁVis
spectra (33 000ꢁ
11 000 cmꢃ1) were recorded on a
SPECORD M40 instrument in Nujol, IR spectra
(4000ꢁ
400 cmꢃ1) on a SPECORD IR 80 instrument
/
/
ꢃ
/
/
/
[(Cu(medpt))2ox](ClO4)2
methyl-dipropylamine)
(medptꢀ
/
(Jꢀ 1.9
/
ꢂ
/
/
(medpt))2ox](NO3)2×
[(Cu(trimeen)H2O)2ox](ClO4)2×
N,N,N?-trimethylethylenediamine) (Jꢀ
[(Cu(trimeen)H2O)2ox](NO3)2×2H2O (Jꢀ
and [(Cu(dieten)H2O)2ox](ClO4)2×
diethylethylenediamine) (Jꢀ
/
2 2/3H2O [29] (Jꢀ
/
ꢃ
/
/2H2O
/
/
ꢃ
/
/
/
/
ꢃ
/
)
/
/
/
/
ꢃ
/
/
We have extended the series of amine ligands by dmen
(N,N-dimethylethylenediamine) and dben (N,N?-diben-
zylethylenediamine) with the aim to prepare new bi-
nuclear m-oxalato copper(II) complexes. Therefore, we
carried out the reaction of copper(II) perchlorate (or
copper(II) nitrate), the appropriate amine and sodium
oxalate and prepared binuclear m-oxalato copper(II)
using the Nujol technique. The magnetic susceptibilities
were measured in the temperature range liquid nitrogen
to room temperature (r.t.) by the Faraday method on
the balance constructed in Nicholas Copernicus Uni-
versity (complexes 3 and 4) and in Palacky´ University
(complex 2) with Hg[Co(NCS)4] as a calibrant [32]. The
molar susceptibilities of all complexes were corrected for
diamagnetism using Pascal’s constants [33].
complexes [(Cu(dmen)H2O)2ox](ClO4)2×
/
H2O (2) and
[(Cu(dben)NO3)2ox] (4). Our attempts to prepare the
analogous complexes [(Cu(dmen)H2O)2ox](NO3)2 and
[(Cu(dben)H2O)2ox](ClO4)2 led only to non-reproduci-
ble products. Surprisingly, the reaction of copper(II)
perchlorate, N,N-dimethylethylenediamine, sodium ox-
alate and potassium cyanate in aqueous solution did not
result in a complex with oxalato or cyanato bridging
ligands but the mononuclear oxalato complex [Cu(dme-
n)ox(H2O)]2[Cu(dmen)2](ClO4)2 (1).
Julve et al. [2] prepared an interesting binuclear
oxalato-bridged complex with non-equal copper(II)
centres (each copper atom is coordinated by a different
blocking ligand) of composition [Cu(tmen)(H2O)(ox)-
Crystals of [Cu(dmen)ox(H2O)]2[Cu(dmen)2](ClO4)2
(1) of X-ray quality were obtained from water by slow
evaporation of solvent at r.t. The reflections were
collected at 150 K on a four-circle k-axis KUMA
KM-4 diffractometer. The structure was solved by the
heavy method using atom the program SHELXS-97 [34].
All non-hydrogen atoms were refined anisotropically
[35] by a full-matrix least-squares with the weight
2
procedure wꢀ
/
[s2(Fo )ꢂ
/
(w1P)2ꢂ
/
w2P]ꢃ1, where Pꢀ
/
2
2
[Fo ꢂ2Fc ]/3, w1ꢀ
/
/
0.0740, w2ꢀ3.4700. Parameters of
/
all hydrogen atoms were refined isotropically. The
crystal data and structure refinement details for [Cu(d-
men)ox(H2O)]2[Cu(dmen)2](ClO4)2 (1) are given in Ta-
ble 1, whereas selected bond lengths and angles are listed
in Table 2.
Cu(dien)](ClO4)2 (tmenꢀ
lenediamine, dienꢀdiethylenetriamine). With the aim
to extend the series of these compounds we tried the
reaction [Cu(tmen)ox]×4H2O, copper(II) perchlorate
/
N,N,N?,N?-tetramethylethy-
/
/
2.2. Syntheses
and 2-(2-aminoethyl)pyridine (aep) that results in the
formation of the complex [Cu(tmen)(H2O)(ox)Cu(aep)-
(H2O)](ClO4)2 (3).
Caution! Perchlorates and perchlorate salts of metal
complexes with organic ligands are potentially explo-
sive. A small amount of material only should be
prepared and it should be handled with care.
The prepared compounds were characterised by
elemental analysis, IR and UVꢁVis spectroscopies and
/
magnetic susceptibility measurements. The crystal struc-
ture of the complex [Cu(dmen)ox(H2O)]2[Cu(dmen)2]-
(ClO4)2 (1) has been determined by a single-crystal X-
ray analysis.
2.2.1. [Cu(dmen)ox(H2O)]2[Cu(dmen)2](ClO4)2 (1)
A solution of 0.22 g (2.71 mmol) of KOCN and 0.36 g
(2.69 mmol) of sodium oxalate in 25 cm3 of water was
added to a solution of 2.00 g (5.40 mmol) of Cu(ClO4)2×
/
6H2O and 0.59 cm3 (5.37 mmol) of N,N-dimethylethy-
lenediamine in 10 cm3 of water. After 1 h of stirring the
reaction mixture was concentrated to crystallisation in a
water bath. The obtained dark blue crystals were filtered
off and dried in air. The yield was 0.6 g (45%).
2. Experimental
2.1. Chemicals and methods
The starting material Cu(ClO4)2×
/
6H2O was obtained
by the reaction of basic copper(II) carbonate and HClO4
(Carlo Erba) in aqueous solution (the reaction mixture
was concentrated to crystallisation, the solid was filtered
2.2.2. [(Cu(dmen)H2O)2ox](ClO4)2×
A solution of 0.18 g (1.34 mmol) of sodium oxalate in
15 cm3 of water was added to a solution of 1.00 g (2.70
/
H2O (2)

Z. Sme´kal et al. / Polyhedron 21 (2002) 1203ꢁ
/1209
1205
Table 1
Crystal data and structure refinement parameters for [Cu(dmen)-
ox(H2O)]2[Cu(dmen)2](ClO4)2 (1)
mmol) of Cu(ClO4)2×
/
6H2O and 0.30 cm3 (2.73 mmol) of
N,N-dimethylethylenediamine in 25 cm3 of water. The
resulting dark blue solution was concentrated to 15 cm3
to crystallisation by heating. A small amount of solid
formed was discarded. The filtrate was allowed to stand
overnight. The light blue microcrystals were filtered off,
washed with a small amount of water and dried in air.
The yield was 0.35 g (40%).
Formula
Formula weight (g molꢃ1
Temperature (K)
C10H26ClCu1.5N4O9
)
477.11
150(2)
0.71073
˚
Wavelength (A)
Crystal system
Space group
Unit cell dimensions
triclinic
¯
/ /
P
1
˚
a (A)
6.4920(10)
8.501(2)
17.079(3)
94.38(3)
100.68(1)
103.80(3)
892.3(3)
2
2.2.3. [Cu(tmen)(H2O)(ox)Cu(aep)(H2O)](ClO4)2
(3)
˚
b (A)
˚
c (A)
A solution of 0.50 g (1.35 mmol) of Cu(ClO4)2×
/
6H2O
and 0.16 cm3 (1.34 mmol) of 2-(2-aminoethyl)pyridine in
20 cm3 of water was added to a solution of 0.46 g (1.35
a (8)
b (8)
g (8)
V (A )
mmol) of [Cu(tmen)ox]×
/
4H2O in 15 cm3 of water. The
3
˚
resulting dark blue solution was concentrated to 10 cm3
to crystallisation by heating. A small amount of light
blue powder formed was discarded. The filtrate was
allowed to stand overnight. The obtained blue poly-
crystalline product was filtered off and dried in air. The
yield was 0.2 g (22%).
Z
Calculated density (Mg mꢃ3
)
1.776
2.006
Absorption coefficient (mmꢃ1
F(000)
Crystal size (mm)
)
493
0.35ꢄ0.30ꢄ0.25
u Range for data collection (8) 3.67ꢁ
Index ranges
/29.21
ꢃ55h 58, ꢃ115k 511,
ꢃ235l 523
Reflection collected/unique
Refinement method
7649/4279 [Rintꢀ0.0297]
full-matrix least-squares on F2
4279/0/258
2.2.4. [(Cu(dben)NO3)2ox] (4)
A solution of 0.14 g (1.04 mmol) of sodium oxalate in
a minimum amount of water was added to a solution of
Data/restraints/parameters
Goodness-of-fit on F2
Final R factor [I ꢀ2s(I)]
R factor (all data)
1.080
R1ꢀ0.0431, wR2ꢀ0.1440
R1ꢀ0.0461, wR2ꢀ0.1454
0.50 g (2.07 mmol) of Cu(NO3)2×
/
3H2O and 0.49 cm3
(2.08 mmol) of N,N?-dibenzylethylenediamine in etha-
nol (25 cm3) and water (10 cm3). The reaction mixture
was filtered and the filtrate was allowed to stand
overnight. The blue microcrystalline product was fil-
tered off, washed with water and ethanol and dried in
air. The yield was 0.7 g (85%).
Largest difference peak and hole 0.972 and ꢃ0.780
ꢃ3
˚
(e A
)
Table 2
˚
Selected bond lengths (A) and angles (8) for[Cu(dmen)ox(H2O)]2[Cu-
(dmen)2](ClO4)2 (1)
3. Results and discussion
Bond lengths
3.1. Structure of complex 1
Cu(1)ÃO(4)
Cu(1)ÃO(3)
Cu(1)ÃN(2)
Cu(1)ÃN(1)
Cu(1)ÃO(9)
Cu(2)ÃN(4)
Cu(2)ÃN(3)
1.940(3)
1.957(3)
2.015(3)
2.022(3)
2.345(3)
1.994(3)
2.095(3)
The
(dmen)2](ClO4)2 (1) is made up of neutral [Cu(dmen)-
structure
of
[Cu(dmen)ox(H2O)]2[Cu-
ox(H2O)] units, cationic [Cu(dmen)2]2ꢂ units and un-
Bond angles
O(4)ÃCu(1)ÃO(3)
O(4)ÃCu(1)ÃN(2)
O(3)ÃCu(1)ÃN(2)
O(4)ÃCu(1)ÃN(1)
O(3)ÃCu(1)ÃN(1)
N(2)ÃCu(1)ÃN(1)
O(4)ÃCu(1)ÃO(9)
O(3)ÃCu(1)ÃO(9)
N(2)ÃCu(1)ÃO(9)
N(1)ÃCu(1)ÃO(9)
N(4)ÃCu(2)ÃN(3)
N(4a) aÃCu(2)ÃN(3)
84.50(11)
95.18(12)
164.41(13)
175.16(11)
92.57(11)
86.61(12)
87.68(11)
105.97(11)
89.57(12)
96.84(11)
85.30(12)
94.70(12)
a
Symmetry transformations used to generate equivalent atoms:
ꢃx, ꢃyꢂ1, ꢃzꢂ1.
Fig. 1. A view (thermal ellipsoids are drawn at 40% probability level)
of [Cu(dmen)ox(H2O)]2[Cu(dmen)2](ClO4)2 (1).

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Z. Sme´kal et al. / Polyhedron 21 (2002) 1203ꢁ1209
/
Table 3
Elemental analysis of the complexes
Complex
Found (Calc.) (%)
C
H
N
[Cu(dmen)ox(H2O)]2[Cu(dmen)2](ClO4)2 (1)
[(Cu(dmen)H2O)2ox](ClO4)2×H2O (2)
[Cu(tmen)(H2O)(ox)Cu(aep)(H2O)](ClO4)2 (3)
[(Cu(dben)NO3)2ox] (4)
24.6 (25.2)
19.1 (18.6)
26.2 (26.4)
49.8 (49.2)
4.7 (5.5)
4.3 (4.7)
4.4 (4.6)
4.9 (5.2)
11.9 (11.8)
7.8 (8.7)
8.1 (8.2)
10.2 (9.5)
coordinated perchlorate anions (Fig. 1). The [Cu(dme-
n)ox(H2O)] complex, [Cu(dmen)2]2ꢂ cation and per-
chlorate anion, in a 2:1:2 molar ratio, coexist. The
copper atom of the neutral [Cu(dmen)ox(H2O)] unit
shows a distorted square-pyramidal environment with
the two oxygen atoms of oxalate and two nitrogen
atoms of dmen building the basal plane and an oxygen
atom of a water molecule in the apical position. The in-
cmꢃ1 (s), n4(ClO4) 624ꢁ
/
620 cmꢃ1 (s), nasym(OCO)
788 cmꢃ1 (m).
1642ꢁ
/
1668 cmꢃ1 (s) and d(OCO) 752ꢁ
/
These values are consistent with coordinated oxalate
[7,12,38,39] and uncoordinated perchlorate [28,29,40]
anions.
The UVꢁ
are characterised by a strong band in the range 11 000ꢁ
16 000 cmꢃ1 corresponding to a dꢁ
d transition [41]. In
/
Vis absorption spectra of Cu(II) complexes
/
/
plane CuÃ
/
N and CuÃ
/
O bond lengths ranges from
the present compounds, the maxima for 1 (16 250), 2
(16 450), 3 (14 900) and 4 (15 700 cmꢃ1) with omax (molꢃ1
dm3 cmꢃ1; per Cu) equal to 62 (1), 115 (2), 140 (3) and 103
(4), respectively, correspond to this band.
˚
1.940(3) to 2.022(3) A and the axial CuÃ
/
O bond
distance 2.345(3) A is significantly longer than the in-
plane CuÃN and CuÃO bond lengths. The value of the t
˚
/
/
parameter (17.9) [36] discloses a square-pyramidal shape
of the coordination polyhedron (ideal t value for
square-pyramidal situation is 0 and for trigonal bipyr-
amidal situation is 100). The copper atom of the cationic
[Cu(dmen)2]2ꢂ unit is situated on a crystallographic
centre of symmetry and shows a square-planar environ-
3.3. Magnetic properties
The magnetic susceptibility of the mononuclear com-
plex [Cu(dmen)ox(H2O)]2[Cu(dmen)2](ClO4)2 (1) was
measured at r.t. only. The observed value of the
magnetic moment (1.82mB per Cu) is in accordance
with the literature data for magnetically diluted com-
pounds of copper(II).
ment with four nitrogen atoms from two molecules of
˚
N bond length (1.994(3) A) is
dmen. The one CuÃ
/
shorter than the other CuÃ
/N bond length (2.095(3)
˚
A). This difference may be explained by steric hindrance
from the methyl groups bonded to donor nitrogen atom.
The neutral complex [Cu(dmen)ox(H2O)] has square-
pyramidal arrangement around the copper(II) atom
with the two oxygen atoms of oxalate and two nitrogen
atoms of N,N-dimethylethylenediamine forming the
basal plane and an oxygen atom of a water molecule
in the apical position as in the analogous complex
The variable-temperature magnetic moment and
magnetic susceptibility in the range 84ꢁ
pound 2) and 78ꢁ298 K (compounds 3 and 4) for solid
samples is shown in Figs. 2ꢁ4. The magnetic moment
are dependent on temperature and decreases from 1.31ꢁ
1.40 mB (per Cu) at 298 (or 295) K to 0.29ꢁ0.30 mB (per
/
295 K (com-
/
/
/
/
Cu) at 78 (or 84) K (see Tables 3 and 4). This implies
rather strong antiferromagnetic coupling mediated by
the oxalate bridge.
[Cu(L)ox(H2O)] (Lꢀ
/
N,N?-dimethylethylenediamine)
[37] (its structure has been known since 1973).
Magnetic measurements show that complexes 2ꢁ
behave like a common copper(II) dimers (Hꢀ 2JS1S2,
S1ꢀS2ꢀ1/2) (see Figs. 2ꢁ4). The molar magnetic
susceptibility was expressed by the modified Bleaneyꢁ
/
4
/
ꢃ
/
3.2. IR and UVꢁ
/Vis
/
/
/
/
The characteristic IR spectra group vibrations of the
complexes prepared are as follows: n3(ClO4) 1056ꢁ1100
Bowers equation allowing for the presence of paramag-
netic impurity [42]:
/
Table 4
Magnetic properties of the complexes
Complex
meff (per Cu)/T[mB] (K)
J (cmꢃ1
)
g
P (%)
[Cu(dmen)ox(H2O)]2[Cu(dmen)2](ClO4)2 (1)
[(Cu(dmen)H2O)2ox](ClO4)2×H2O (2)
[Cu(tmen)(H2O)(ox)Cu(aep)(H2O)](ClO4)2 (3)
[(Cu(dben)NO3)2ox] (4)
1.82/294
1.40/295ꢁ
1.31/298ꢁ
1.35/298ꢁ
/
0.30/84
0.30/78
0.29/78
ꢃ157
ꢃ175
ꢃ167
2.150
2.108
2.123
0
/
1.63
0.86
/

Z. Sme´kal et al. / Polyhedron 21 (2002) 1203ꢁ
/1209
1207
Fig. 2. Variation of corrected molar magnetic susceptibility (m) and effective magnetic moment (k) per mole of [(Cu(dmen)H2O)2ox](ClO4)2×
/H2O
(2) complex with temperature. The circles are the experimental points, the solid lines are theoretical lines.
xMcorr ꢀ2(Ng2b2=3kT)[1ꢂ1=3 exp(ꢃ2J=kT)]ꢃ1(1ꢃP)
ꢂ(Ngii2b2=4kT)PꢂNa
equal to 120ꢄ
10ꢃ6 cm3 molꢃ1 (per dimer), and the
other symbols have their usual meanings. The best fit
parameters J, g and P, were obtained by using a non-
linear least-squares program. The exchange integral
/
corr
where xM is the corrected molar magnetic suscept-
does not depend on the gi value within range 2.1ꢁ2.2
/
ibility per copper(II) dimer, P is the mole fraction of the
monomeric copper(II) impurities, gi is the average g
factor of the impurity which was fixed at 2.15 through-
and Na within the reasonable range, whereas changes
on g-value and P are negligible. As a convenient
statistical indicator of the quality of the least-squares
out the present study, ꢃ
/
2J is the singlet-triplet separa-
fits, the discrepancy index sdis (sdis
ꢀ
/
[a(xobs
ꢃ
xcalc)2/
/
tion, Na is the temperature independent paramagnetism
Fig. 3. Variation of corrected molar magnetic susceptibility (m) and effective magnetic moment (k) per mole of [Cu(tmen)(H2O)(ox)Cu-
(aep)(H2O)](ClO4)2 (3) complex with temperature. The circles are the experimental points, the solid lines are theoretical lines.

1208
Z. Sme´kal et al. / Polyhedron 21 (2002) 1203ꢁ1209
/
Fig. 4. Variation of corrected molar magnetic susceptibility (m) and effective magnetic moment (k) per mole of [(Cu(dben)NO3)2ox] (4) complex
with temperature. The circles are the experimental points, the solid lines are theoretical lines.
a(xobs)2]1/2) was employed. The least-square fit (see
Table 4) of the data yields Jꢀ
157 cmꢃ1 (sdis
3.99ꢄ 3.08ꢄ
10ꢃ3), Jꢀ 175 cmꢃ1 (sdis 10ꢃ3) and
Jꢀ 4.74ꢄ 2JS1S2,
167 cmꢃ1 (sdis 10ꢃ3) (Hꢀ
S1ꢀS2ꢀ1/2) for 2, 3 and 4, respectively.
Hence, the compounds 2ꢁ4 exhibit a strong antifer-
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/
ꢃ
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/
ꢀ
/
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