Thermal, vibrational and EPR studies of Cu(II) bromide bis(p-methylaniline) and bis(m-methylaniline) complexes.

Article abstract of DOI:10.1016/S1386-1425(03)00242-7

[CuBr(2)(pMA)(2)] and [CuBr(2)(mMA)(2)] complexes (pMA: p-methylaniline, mMA: m-methylaniline) have been prepared and characterized by elemental analyses, thermogravimetric analyses, magnetic moment measurements, and IR, Raman and EPR spectroscopic studies. Coordination effects on the vibrational spectra of the ligands have been investigated. The room temperature EPR spectra of the complexes and their simulated spectra are also discussed in detail. The vibrational and EPR spectral studies suggest that the coordination sphere around Cu(II) consist of a distorted tetragonal structure.

Full text of DOI:10.1016/S1386-1425(03)00242-7

Spectrochimica Acta Part A 60 (2004) 303–309
Thermal, vibrational and EPR studies of Cu(II) bromide
bis(p-methylaniline) and bis(m-methylaniline) complexes
K. Golcuka,∗, A. Altuna, S. Gunera, M. Kumrua, B. Aktasb
a
Department of Physics, Fatih University, 34900 B. Cekmece, Istanbul, Turkey
Department of Physics, Institute of Technology, PK 141, 41400 Gebze, Turkey
b
Received 3 February 2003; received in revised form 19 May 2003; accepted 19 May 2003
Abstract
[CuBr2(pMA)2] and [CuBr2(mMA)2] complexes (pMA: p-methylaniline, mMA: m-methylaniline) have been prepared and characterized
by elemental analyses, thermogravimetric analyses, magnetic moment measurements, and IR, Raman and EPR spectroscopic studies. Coordi-
nation effects on the vibrational spectra of the ligands have been investigated. The room temperature EPR spectra of the complexes and their
simulated spectra are also discussed in detail. The vibrational and EPR spectral studies suggest that the coordination sphere around Cu(II)
consist of a distorted tetragonal structure.
© 2003 Published by Elsevier B.V.
Keywords: Copper(II) bromide; p-Methylaniline; m-Methylaniline; IR; Raman and EPR spectra
1. Introduction
2. Experimental
Aniline and its derivatives are of great industrial im-
portance. Hence, investigations on the structures of these
compounds and related metal-complexes are very important
for a better understanding of their molecular properties. A
number of first row transition metal dihalides complexes
with aniline and its derivatives have been previously re-
ported [1–6]. However, there has been no complete study
on the spectroscopic and magnetic properties of these metal
halide compounds.
In this paper we report thermogravimetric behaviors, vi-
brational and EPR spectral studies of copper(II) bromide
complexes with pMA (4-C7H9N = para-methylaniline)
and mMA (3-C7H9N = meta-methylaniline). Spectral
and magnetic measurements have been used to char-
acterize each metal complex and to interpret the type
of coordination around Cu(II) metal. The theoreti-
cally simulated EPR spectra of the complexes are also
discussed.
The ligands (L: pMA and mMA) and CuBr2 were used
as received from Aldrich Co. without further purification. In
this report, we described the identity of the products obtained
from 1:2 CuBr2/L reaction. The complex of [CuBr2(pMA)2]
was prepared by adding pMA (2 mmol) in ethanolic solu-
tion to a solution of CuBr2 (1 mmol) in an equal volume
of the same solvent. The complex of [CuBr2(mMA)2] was
prepared by heating CuBr2 (1 mmol) directly with liquid
mMA (2 mmol). After stirring for an hour, the precipi-
tated complexes were collected by filtration, washed with
ether and dried under reduced pressure. Single crystals
of the complexes were not isolated. Composition and pu-
rity were determined by microanalysis (C, H, N and Cu)
(see Table 1).
The IR spectra were recorded using KBr discs over range
4000–400 cm−1 and using polyethylene discs over the range
500–200 cm−1 on a Perkin–Elmer Paragon 1000 FTIR and
a Mattson 2030 Galaxy FTIR spectrometer, respectively.
The Raman spectra were recorded on a Bruker RFS/100
Raman spectrometer in the range 4000–0 cm−1. The samples
were excited by a near IR Nd:YaG laser delivering excitation
wavelength of 1064 nm. A liquid nitrogen cooled Ge detector
was used.
∗
Corresponding author. Tel.: +90-212-889-0810;
fax: +90-212-889-0832.
E-mail address: kgolcuk@fatih.edu.tr (K. Golcuk).
1386-1425/$ – see front matter © 2003 Published by Elsevier B.V.
doi:10.1016/S1386-1425(03)00242-7

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K. Golcuk et al. / Spectrochimica Acta Part A 60 (2004) 303–309
Table 1
Analytical data of the complexes
Compound
Color
Found (calc.) %
Cu
C
N
H
[CuBr2(pMA)2]
[CuBr2(mMA)2]
Green
Dark green
14.70 (14.52)
14.71 (14.52)
38.44 (38.42)
38.43 (38.42)
6.35 (6.40)
6.37 (6.40)
4.17 (4.15)
4.19 (4.15)
Electronic spectra in EtOH were recorded on a Perkin–
Elmer Lambda 9 UV–VIS–NIR spectrometer in the range
190–1100 nm.
complex with pMA is more thermally stable than the com-
plex with mMA. The difference between the stabilities of the
complexes arises from the structural and electronic change
between meta and para isomers. The observed weight losses
for the decomposition processes in each of the complexes
compare favorably with the theoretical data listed in Table 2.
Thermal analyses were made on a Mettler Toledo TG50
thermobalance under N2 flow (flow rate, 30 cm3 min−1).
The samples were heated in an Al2O3 crucible at a rate of
10 ◦C min−1
.
Measurements of magnetic moments at room temperature
were made using the Evans method with a Sherwood Sci.
magnetic balance. The molar susceptibilities were corrected
for the diamagnetism of the constituent atoms using Pascal’s
constants.
3.2. UV–Vis, IR and Raman spectra
The bands (525–600 nm) in the visible region could orig-
inate either from charge transfer or d–d transitions bands [7]
and are present as shoulders on the tail of a strong charge
transfer band which extends across the visible region.
All the typical bands of the pMA and mMA ligands
appear in the FT-IR spectra of the metal complexes.
The Raman spectrum of free pMA and FT-IR spectra of
[CuBr2(pMA)2] and pMA are shown together in Fig. 1.
The Raman spectrum of free mMA and FT-IR spectra of
[CuBr2(mMA)2] and mMA are given together in Fig. 2.
The Raman spectra of copper complexes exhibit strong
The EPR experiments on Cu2+ (2D5/2) complexes have
been performed at room temperature. The field-derivative
EPR spectra have been registered by a conventional X-band
(␯ = 9.5–9.8 GHz) Bruker EMX model spectrometer em-
ploying an ac magnetic modulation technique.
3. Results and discussion
3.1. Thermal study
The major features of the thermal analysis of the com-
plexes are summarized in Table 2. Both complexes decom-
pose in a two-stage process. The first stage corresponds to
the loss of 2 mols of ligands. The DTG curve of the complex
with pMA reveals two overlapping reaction steps in which
the loss of two pMA occurs. One part of the two pMA is re-
moved in the 85–210 ◦C range. The remaining part is com-
pletely removed in the 210–340 ◦C range. In the first step
(50–370 ◦C range) of the complex with mMA, the maxi-
mum mass losses of the complex occur at 110 and 195 ◦C,
which correspond to the loss of mMA. The second decom-
position stage consists of the loss of the 1 mol of CuBr2,
leaving a very low percentage of a residue. We could not
say anything whether the decomposition steps are endother-
mic or exothermic due to the lack of DTA data. The initial
decomposition temperature of each complex reveals that the
Fig. 1. FT-Raman spectrum of (a) pMA and FT-IR spectra of (b) pMA
and (c) [CuBr2(pMA)2].
Table 2
Thermal decomposition process of the complexes
Compound
Process
Decomp. range (◦C)
DTG peaks (◦C)
Weight loss (%)
Found
Calculated
[CuBr2(pMA)2]
[CuBr2(mMA)2]
[CuBr2(pMA)2]→[CuBr2(pMA)]
[CuBr2(pMA)]→CuBr2
85–210
210–340
50–370
148
250
110, 195
21.12
25.82
46.02
24.48
24.48
48.97
[CuBr2(mMA)2]→CuBr2

K. Golcuk et al. / Spectrochimica Acta Part A 60 (2004) 303–309
305
florescence, causing disappearance of some bands. The re-
solvable bands and their assignments are listed in Table 3.
Vibrational mode assignments of free pMA and mMA are
based on ab initio and DFT studies and reported in [8,9].
The bands due to the ␯NH stretching vibrations are shifted
to lower wavenumber (150–120 cm−1) on the formation of
the complexes. This would confirm that the N atom of the
amine group coordinates to Cu(II) [1–3]. The shifting to the
lower frequencies can be explained as a weakening of the
N–H bonds resulting from the electron drainage from the
nitrogen atom due to its coordination to the metal atom [4].
The NH2 scissoring frequencies at 1621 and 1622 cm−1
in the pMA and mMA spectra, respectively, are lowered 40
cm−1 by coordination. The reason for this shift is the change
in nitrogen orbitals and its effect on the NH2 force constant
because of the change in HNH angle [6].
Fig. 2. FT-Raman spectrum of (a) mMA and FT-IR spectra of (b) mMA
and (c) [CuBr2(mMA)2].
Engelter et al. [2] reported an IR study of some metal(II)
halide complexes with mMA and oMA (o-methylaniline)
based on 15N-labelling study. This is an extremely useful
Table 3
Band assignments of IR and Raman spectra of the complexes
mMA
IR
pMA
IR
[CuBr2(mMA)2]
IR
[CuBr2(pMA)2]
IR
Assignment
Ra
Ra
Ra
Ra
3435 s
3354 s
3416 s
3333 s
3418 w
3337 w
3054 s
3013 s
2917 w
2861 m
1617 s
1581 m
3296 s
3286 s
3226 s
3056 w
3006 w
2916 m
2857 w
1562 s
1592 s
1508 s
1440 w
1347 w
1322 w
1238 w
1216 m
␯NH asym
␯NH sym
␯CH ring
3353 m
3046 s
3012 s
3353 m
3060 w
3020 w
2920 m
2857 w
1558 s
1592 m
1491 s
1463 s
1374 m
1312 w
1254 m
1230 vw
3220 w
3062 w
3034 m
3015 m,sh
2919 m
2857 w
1622 vs
1591 vs
1493 vs
1469 s
3056 w
3008 m
2912 m
2859 m
1621 vs
1582 m
1514 vs
1441 s
3053 w
2916 w
␯CH ring
2919 s
2913 w
2856 w
1561 vw
1596 m
1487 w
1445 m
␯CH3 (asym.)
2×1469 over
NH2 sciss
␯CC ring
2857 m
1622 s,b
1590 m
1493 vw
1577 w,b
1597 m
1513 w,sh
1455 m
␯CC ring
␤CH3 (asym.)
␤CH3 (sym.)
␤CH
␯CN
␯CN
1381 w
1314 m
1293 s
1378 m
1313 m
1293 s
1344 m
1324 m
1267 vs
1380 m
1324 w
1271 m
1355 w
1256 m
1232 m
1239 w
1216 w
1170 s
1077 w
1038 w
996 m
926 w
870 m
775 vs
726 m,sh
691 vs
655b
1166 m
1075 w
1218 m
␯CCH3
1072 w
1044 m
983 w
1130 vw
1032 w
1000 w
920 m
878 m
780 vs
724 m
693 s
1084 vs
537 m
440 m
474 w
389 w
322 s
1122 w
998 m
1144 w
1041 w
1145 m
NH2 rocka
␥CCH3
996 m
928 w
␤CCC ring
␤CCC ring
␥CH ring; ␥CCC
␥CH ring; ␥CCC
Breathing
␥CCC ring
NH2 waga
␤CCC ring
␤CCC ring
␯(Cu–N)
929 w,sh
934 w
844 s
645 s
466 s
877 w
784 w
738 s
763 m
641b
812 vs
738 m
739 w,sh
1093 m
692 w
1085 s
549 vw
1094 vs
537 w
443 m
487 m
383 m
332 s
557 m
431 w
466 m,b
360 m,b
480 vw,b
382 vw,b
␯(Cu–N)
324 m
212b
␥CCC ring
␤CNH2; ␤CH3
NH2 twista
␯(Cu–Br)t
␥CNH2
294 m
234 m
306 w
670 s
237 m
218 s
305 w
645 m,b
245 w
297 s
296 m,b
635 m
244 m
221 m
207 m
633 w,sh
251 vw,sh
222 vw,sh
216 m
224 m,b
202 m
␯(Cu–Br)t
Keys; vs, very strong; s, strong; m, medium; w, weak; vw, very weak; b, broad; sh, shoulder; ␯, stretch; ␤, in plane bend; ␥, out of plane.
a
Mode has been reassigned.
Mode has not been observed, but has been found based on ab initio and DFT calculations [10,11].
b

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K. Golcuk et al. / Spectrochimica Acta Part A 60 (2004) 303–309
criterion for distinguishing NH2 vibrations from phenyl
ring modes but it does not clarify the assignment of the
NH2 modes. They assigned the band around 733 cm−1
to NH2 wagging vibration of Cu(II) complexes although
this vibrational mode tends to appear in the 1200–1000
cm−1 region in aniline complexes, supported by –ND2 ex-
periments and normal coordinate analysis [3,5], similar to
the methylamine and p-phenylendiamine complexes [10].
We, therefore, prefer to reassign the strong bands in the
1093–1084 cm−1 region in the spectra of the title com-
plexes to the NH2 wagging mode instead of the assignment
of Engelter et al. [2] as NH2 twisting mode.
The NH2 wagging vibration has been theoretically found
based on ab initio and DFT calculations, at 641 and 655
cm−1 in free pMA and mMA, respectively [8,9]. However,
this mode has not been observed due to broad bands within
the range 750–530 cm−1 in the spectra of free mMA and
pMA. This upward shift of 450–500 cm−1 in NH2 wagging
mode on complex formation seems quite large but might be
due to the effect of the changes in hybridazition about the
nitrogen atom [3–5].
On the other hand, the NH2 rocking and twisting modes
have been also reassigned on taking into account the new
assignments [3–5,8–12]. The weak IR and Raman bands
at 1130 (IR)–1122 (Ra) and 1144(IR)–1145(Ra) cm−1 in
the spectra of [CuBr2(mMA)2] and [CuBr2(pMA)2], respec-
tively, have been attributed to the NH2 rocking mode. The
bands in the range of 670–633 cm−1 in the spectra of com-
plexes have been ascribed to the NH2 twisting mode.
In substituted anilines, the ␯C–N stretching appears
near 1270 cm−1, being relatively strong compared with
the nearby bands [2]. Hence, we have assigned the bands
observed at 1293 and 1267 cm−1 as the ␯C–N stretching
for the free mMA and pMA, respectively. Absorptions at-
tributed to this vibration occur at lower frequencies in the
=
complexes, in line with the decrease in the C N double
bond character [11].
In the low frequency region, especially below 500 cm−1
,
it is considered that the metal–ligand vibrations occur
[12,13]. Assignments of the metal–ligand vibrations, listed
in Table 3, have been given carefully by considering of
the internal modes of pMA and mMA and comparing with
the extensive literature reports [1–19]. The 500–200 cm−1
region spectra of [CuBr2(pMA)2] and [CuBr2(mMA)2]
complexes are shown in Fig. 3.
In the 480–360 cm−1 region, Engelter et al. [2] found
two ␯(Cu–N) vibrations showing 15N-sensitivity in chloro-
and bromo-complexes. The Ci site symmetry requires one
␯(M–N) and two ␯(M–X) (X: Cl, Br or I) IR active bands
[2,14]. But, some vibrational couplings among Cu–N vibra-
tions and some of the ring modes may occur [2,11]. For this
reason, the spectra of Cu(II) complexes reveals two ␯(Cu–N)
bands in the 487–360 cm−1 region. Consequently, the nor-
mal site symmetry criteria for determining the number of
expected IR active bands are not strictly applied to these
complexes.
The observed ␯(Cu–N) values are higher in pMA complex
than in those of mMA, suggesting that there is more signif-
icant distortion in [CuBr2(pMA)2] as is observed in the IR
spectra of chloro-and bromo-complexes of Cu(II) [2,6].
The terminal Cu–Br bond antisymmetric and symmet-
ric stretching vibrations, i.e. ␯(Cu–Br)t; were observed
in 237–251 and 202–207 cm−1 region, respectively. On
the other hand, the stretching vibrations of the bridging
Cu–Br–Cu bonds, i.e. ␯(Cu–Br)b; should appear below
200 cm−1 [16]. But, we could not observe any ␯(Cu–Br)b
Fig. 3. 500–200 cm−1 region spectra of (a) [CuBr2(pMA)2] and (b) [CuBr2(mMA)2].

K. Golcuk et al. / Spectrochimica Acta Part A 60 (2004) 303–309
307
vibrations in the Raman spectra of complexes. The possi-
ble Cu–Br (axial) interactions must be very weak, if the
bridging Cu–Br–Cu bonds exist [17–19].
Singh et al. [17] reported an X-ray study of [CuBr2(2-
methylpyridine)2]. The coordination type of CuBr2N2 chro-
mophore was a distorted tetragonal pyramid with bromine
and nitrogen atoms in the basal plane and the bridging
bromine atom from another molecule occupying the fifth
coordination site. The bond between the bridged bromide
and copper was considerably longer than other two termi-
nal Cu–Br bonds. The similar results were also observed in
several Cu(II) complexes [17–21]. Hence, the appearance of
the ␯(Cu–Br)t vibrations indicates tetragonal structure in-
stead of a polymeric octahedral structure with exclusively
bridging bromides for the title complexes. The difference
between this tetragonal type of complex and the almost reg-
ular octahedral structures is simply a matter of distortion
along the z-axis. By suitably elongating the bonds along this
axis it is passed from an octahedral to a tetragonal structure
with weak axial Cu–Br bonds. This distortion has been ob-
served in most Cu(II) complexes studied so far [2,7,17–21].
It is also related that the d9 nonbonding configuration of the
Cu atom is expected to give rise to tetragonal arrangement
of the ligands [20]. We, therefore, propose molecular struc-
ture of [CuBr2(mMA)2] and [CuBr2(pMA)2] complexes as
shown in Fig. 4. The coordination around Cu(II) ion con-
sists of four bonds in a square coplanar arrangement and
two weaker bonds normal to the plane which is represented
as thin dotted lines.
Fig. 4. Proposed molecular structure of Cu(II) complexes. The thin dotted
lines represent the weak interactions between Cu and Br (the coordination
occurs via the N atom of the ligands pMA or mMA).
3.3. EPR study
The first-derivative EPR signal taken from [CuBr2-
(pMA)2] was plotted together with the simulated ones in
Fig. 5. The experimental spectrum has a form that is char-
acteristic for a conventional powdered crystalline sample
containing a paramagnetic ion with an axially symmetric
where βe and S denote Bohr magneton and the electronic
spin angular momentum of magnetic ion, respectively.
The EPR spectrum of [CuBr2(pMA)2] complex has been
simulated by using Lorentzian and Gaussian lineshape func-
tions. The best fitted EPR spectrum to the experimental one
g factor with g > g (g = 2.18 and g = 2.05) [22] and
ꢀ
⊥
ꢀ
⊥
without any hyperfine splitting. Namely, the local symme-
try of the paramagnetic center giving this signal should be
axial or tetragonal. The trend g > g > 2 indicates that the
ꢀ
⊥
unpaired electron is located mainly in the dx2−y2 orbital
(2B1 as ground state) [23]. Here g and g denote effective
ꢀ
⊥
g-values when the dc field is applied, respectively, parallel
(B ) and perpendicular (B ) to the symmetry axis of the
ꢀ
⊥
crystalline field around the paramagnetic center.
Although one can observe a greater g value than g
in some powdered compounds, depending on the electronic
configuration of the magnetic center and symmetry type of
⊥
ꢀ
powder crystallites, the absorption that corresponds to g is
⊥
always more intensive than the absorption corresponds to g
ꢀ
in statistically and randomly oriented solids.
The Hamiltonian describing an axially symmetric Zeeman
interaction can be written as:
Haiso = βe(g (BxSx + BySy) + g (BzSz))
(1)
Fig. 5. X-band EPR spectrum of [CuBr2(pMA)2] at room temperature.
⊥
ꢀ

308
K. Golcuk et al. / Spectrochimica Acta Part A 60 (2004) 303–309
has been obtained by using Lorentzian lineshape function as
seen in Fig. 5.
A statistically and randomly oriented powder system con-
tains some crystallites in resonance at all fields, BR varying
between B and B . For a general orientation of a single
ꢀ
⊥
crystalline granular (or molecular unit) containing param-
agnetic center, the solution of the Eq. (1) gives a resonance
field as:
hf
hf
BR
=
[g⊥2 sin2 θ + gꢀ2 cos2 θ]−1/2
(2)
geffβe
βe
where θ is the angle between the magnetic field and the
symmetry axis direction of any particular spin species in the
powder complex. In Eq. (2) the symbol h and f represent
the Plank’s constant and the microwave frequency, respec-
tively. The number of the paramagnetic centers making an
angle θ with the field is proportional to sin θ. By using this
weighing factor together Eq. (2), one can obtain the follow-
ing expression [24] for the amplitude factor, A;
Fig. 6. X-band EPR spectrum of [CuBr2(mMA)2] at room temperature.
interaction between neighboring electronic spins, then any
spin on a particular Cu (II) ion can move around and interacts
with the nuclear spins of other Cu(II) ions having statistically
distributed different nuclear state. The average values of the
nuclear spin of different Cu(II) ion cancel out. Thus, the
observed EPR spectrum of [CuBr2(pMA)2] does not give
any hyperfine features. In this case, the hyperfine structure
is completely compressed. That is, the exchange interaction
is remarkably strong. The g and g values are related by an
B⊥2 (BR2 + Bꢀ2)
A =
(3)
B B2 [(B2 − B2 )(B2 − B2 )]1/2
ꢀ
R
R
⊥
ꢀ
⊥
that is proportional to the number of paramagnetic centers
giving a resonance absorption at BR.
⊥
ꢀ
On the other hand, the resonance curve of any individual
magnetic center has its own intrinsic line shape and width.
This curve reaches its maximum at the resonance field BR.
That is regardless how far from the exact resonance field,
BR, any center can give absorption at any field even it be-
comes unobservable experimentally. The contribution from
any center to the whole absorption line at any field depends
on intrinsic line width.
expression G = (g −2)/(g −2) and found to be less than 4,
ꢀ
⊥
supports the exchange interaction among Cu(II) ions [25] as
well.
The EPR signal taken from powdered [CuBr2(mMA)2]
complex and simulated spectra are shown in Fig. 6. The
X-band EPR spectrum shows isotropic character and does
not contain any hyperfine lines. The agreement of simulated
line with the experimental one supports the isotropic Zee-
man interaction between magnetic ion and static field. The
Hamiltonian describing the isotropic Zeeman interaction can
be written as:
By using Eq. (3) for amplitude factor, we have tried both
Lorentzian and Gaussian lineshape functions for intrinsic
line of randomly oriented centers to reproduce experimental
spectra. The fitting parameters are as follows: B = 3410
⊥
G, B = 3197 G, line width = 34 G. As can be seen from
ꢀ
Hiso = gβeB · J
(4)
Fig. 5, there is a satisfying agreement between experimental
and simulated spectra for Lorentzian line. The simulated
spectrum gives almost all the features of the experimental
one. That is the magnetic center has an axially symmetric
(or at most tetragonal) crystalline local electric field.
where g is Lande splitting factor, βe Bohr magneton and J
is total angular momentum of magnetic ion.
The best simulation for experimental spectrum was ob-
tained by using the first-derivative Lorentzian lineshape
function and line width of 200 G. But there is a significant
discrepancy between Gaussian line and experimental data.
The spectroscopic splitting parameter (g = 2.12) is com-
pletely symmetric. This situation may occur if the crystalline
field is cubic (or equivalently if there is perfect tetrahedrally
or octahedrally coordinated magnetic ion). We could not
observe any hyperfine structure in [CuBr2(mMA)2]. Since
the exchange interaction between Cu(II) electrons is quite
strong.
The spectra of the complexes do not exhibit any hyperfine
lines at both perpendicular and parallel parts of spectrum
as reported in some Cu(II) complexes [25,26]. The reason
must be the exchange-narrowing effect between Cu(II) ions.
It should be noted that the paramagnetic center in our case
is Cu(II) ion. Therefore, one can expect hyperfine structure
in the EPR spectra due to the magnetic interactions between
electronic S ( = 1/2) and nuclear spins, I ( = 3/2). Generally,
this interaction can give rise a splitting about a few tens
oersteds which is easily measurable in most of the cases.
The absence of hyperfine structure suggests the existence
of exchange interactions between electronic spins of Cu(II)
ions in the chain. If there is sufficiently strong exchange
The values of magnetic moment of [CuBr2(pMA)2] and
[CuBr2(mMA)2] have been found by using Evans method
as 1.68 and 1.62 ␮B, respectively. The magnetic moments
of the complexes are slightly lower than the spin-only value

K. Golcuk et al. / Spectrochimica Acta Part A 60 (2004) 303–309
309
of a d9 ion, showing Cu–Cu interaction [1]. The values of
the effective magnetic moments are also consistent with a
distorted tetragonal local environment around the Cu2+ ions
[1,6].
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In conclusion, all the spectral data reveal that the metal
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Cu(II) complexes are isotropic for [CuBr2(mMA)2] and
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