Molecular structure, vibrational and EPR spectra of Cu(II) chloride complex of 4-amino-1-methylbenzene combined with quantum chemical calculations

Article abstract of DOI:10.1016/j.molstruc.2013.09.025

Transition metal complex of CuCl₂ with L = 4-amino-1- methylbenzene, i.e., [CuCl₂L₂], has been synthesized and characterized by elemental analyses, FT-IR, dispersive Raman and EPR methods. The geometrical structure and vibrational spectra of L and [CuCl ₂L₂] have been investigated in terms of density functional calculations employing the 6-311G+(d,p) basis set. The normal modes have been assigned on the basis of the percent potential energy distribution (PED) of the internal motions in each vibrational modes. The effects of the coordination on vibrational modes have been investigated. The experimental vibrational and EPR spectral studies and theoretical calculations find the title complex as a doublet with one unpaired electron.

Full text of DOI:10.1016/j.molstruc.2013.09.025

Journal of Molecular Structure 1054–1055 (2013) 76–82
Contents lists available at ScienceDirect
Journal of Molecular Structure
journal homepage: www.elsevier.com/locate/molstruc
Molecular structure, vibrational and EPR spectra of Cu(II) chloride
complex of 4-amino-1-methylbenzene combined with quantum
chemical calculations
⇑
T. Bardakçı , M. Kumru, S. Güner
_
Department of Physics, Faculty of Arts and Sciences, Fatih University, 34500 Büyükçekmece, Istanbul, Turkey
g r a p h i c a l a b s t r a c t
h i g h l i g h t s
ꢀ
Frequencies and the geometry
parameters of L and [CuCl2L2] were
calculated.
ꢀ
The DFT results were compared with
FT-FIR, FT-IR, and dispersive Raman
data.
ꢀ
ꢀ
The normal modes have been
assigned on the basis of the PED.
EPR was performed to investigate the
molecular arrangement around the
copper atom.
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 19 July 2013
Received in revised form 11 September 2013
Accepted 18 September 2013
Available online 25 September 2013
Transition metal complex of CuCl2 with L = 4-amino-1-methylbenzene, i.e., [CuCl2L2], has been synthe-
sized and characterized by elemental analyses, FT-IR, dispersive Raman and EPR methods. The geomet-
rical structure and vibrational spectra of L and [CuCl2L2] have been investigated in terms of density
functional calculations employing the 6-311G+(d,p) basis set. The normal modes have been assigned
on the basis of the percent potential energy distribution (PED) of the internal motions in each vibrational
modes. The effects of the coordination on vibrational modes have been investigated. The experimental
vibrational and EPR spectral studies and theoretical calculations find the title complex as a doublet with
one unpaired electron.
Keywords:
IR and Raman spectra
EPR
DFT
Ó 2013 Elsevier B.V. All rights reserved.
4-Amino-1-methylbenzene
Aniline derivatives
Cu(II) complex
1. Introduction
sists of a methyl group attached to aniline at the para position. It is
also known as p-toluidine, p-methylaniline, 4-methylaniline, p-
Aniline and its derivatives are widely used in electro-optical
and microelectronic devices such as diodes and transistors, and
as pharmaceuticals [1–5]. The aniline derivative 4-amino-1-meth-
ylbenzene (4-C7H9N), which is abbreviated as L in this study, con-
aminotoluene and 4-aminotouluene. L and related compounds
have wide applications as an intermediate in the production of
dyes [6] and as ligands in coordination chemistry [7–16].
Despite extensive studies on vibrational spectra of transition
metal complexes of aniline and its derivatives [7–16], to the best
of our knowledge, neither complete vibrational or theoretical study
has been performed on CuCl2 complex of L, i.e., on [CuCl2L2]. In this
⇑
Corresponding author. Tel.: +90 212 8663300/2059; fax: +90 212 8890832.
E-mail address: tayyibe.b@gmail.com (T. Bardakçı).
0022-2860/$ - see front matter Ó 2013 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.molstruc.2013.09.025

T. Bardakçı et al. / Journal of Molecular Structure 1054–1055 (2013) 76–82
77
study, we investigate IR and Raman spectra of L and its [CuCl2L2]
complex experimentally. To assign the experimental vibrational
bands in terms of internal vibrations in the modes, we performed
density functional theory (DFT) calculations. We have already
shown that the hybrid DFT functional B3LYP is superior to the HF
and MP2 methods in investigating vibrational spectra of L [3].
The effects of coordination on the vibrational modes have also been
discussed. Moreover, we have investigated the structure of the
[CuCl2L2] complex based on the experimental vibrational and EPR
spectra as well as theoretical DFT studies.
was used to record the first-derivative absorption signals at the
room temperature. A cylindrical quartz tube was used to place
the powder sample in the cavity. Operating conditions were cho-
sen as 0.2 mW microwave power, 1 Oe modulation amplitude,
3300 Oe centerfield, 600 Oe sweep width, 81.92 ms time constant
and 83.89 s sweep time with multiple accumulations to enhance
the signal-to-noise ratio.
3. Quantum chemical calculations
Quantum chemical calculations were performed with Gaussian
03 software package [18] on a linux server cluster. The structures
and normal modes were visualized by Gausview 03 program [19].
The geometry optimizations, vibrational spectra calculations, and
percent potential energy distribution (PED) of free L and [CuCl2L2]
complex in the gas phase were performed by the DFT exchange-cor-
relation functionals BVP86 and B3LYP employing the 6-311G+(d,p)
basis set. BVP86 is a combination of Becke’s 1988 exchange func-
tional [20], Vosko’s correlation functional V for local spin density
part [21] and Perdew’s 1986 gradient correlation functional [22]
while B3LYP consists of Becke’s three-parameter exchange and
Lee–Yang–Parr’s correlation functional [23–25].
2. Experimental
2.1. Material and synthesis
The ligand, L and CuCl2 at the reagent grade were purchased
from Aldrich Chemical Company Inc., and used without further
purification.
[CuCl2L2] was synthesized by adding two moles of L to one mole
of CuCl2 in ethyl alcohol with constant stirring. The precipitated
complex was filtered, washed with diethylether and dried in vac-
uum. All these processes were carried out at room temperature.
The experimental C, H, N and Cu contents of the synthesis complex
agree very well with the theoretically expected contents of the
[CuCl2L2] (see Table 1).
4. Results and discussion
4.1. Molecular structure
2.2. FT-IR measurements
The optimized molecular structures of free L and [CuCl2L2] com-
plex in the gas phase at the room temperature (see Fig. 1 and Ta-
ble 2) have been obtained in terms of BVP86 and B3LYP density
functionals with the 6-311G+(d,p) basis set. The standard error S
and the mean absolute error MAE in the bond lengths relative to
the previous X-ray data of L [26] are respectively 0.183 and 0.014
with B3LYP, and 0.184 and 0.018 with BVP86. S and MAE for the
bond angles are respectively 0.464 and 1.213 with B3LYP, and
0.470 and 1.125 with BVP86. Therefore, B3LYP performs slightly
better than BVP86 both for the bond lengths and the bond angles.
DFT calculations predict some changes in the geometry param-
eters of L with coordination. For instance, C–N bond has been in-
creased from 1.404 Å to 1.439 Å with BVP86, and from 1.401 Å to
1.442 Å with B3LYP. N–H bond has also been increased 0.007 Å
with two of the methods. C–C bonds generally remain unchanged;
however bonds close to Nitrogen atom i.e. C2–C3 and C3–C4 have
been decreased because of coordination.
The 3500–500 cmꢁ1 region FT-IR spectra of L and [CuCl2L2] were
recorded on a Nicolet 6700 Fourier Transform IR (FT-IR) spectrom-
eter with attenuated total reflectance (ATR) sampling technique at
room temperature. The far region (650–50 cmꢁ1) FT-IR (FT-FIR)
spectra of L and [CuCl2L2] were recorded on the same spectrometer
but by preparing polyethylene (PE) pellets. PE pellets were pre-
pared as described previously taking the sample/PE ratio as 1/10
[17], i.e., ꢂ8 mg of PE and 0.8 mg of sample were mixed and
ground in a mortar. The metalic die was heated to 230 °C, and
the temperature of the die surface was expected to be 120–
140 °C (since the melting point of PE is 120–130 °C). The mixture
of PE and samples were added to the die, and put under 6-ton pres-
sure for 2 min. Then the die was disassembled and the PE pellet
was put in the pellet holder of FT-IR spectrometer to record the
far IR region of the spectrum. Since the expansion is big for far re-
gion, the spectra of the title molecules appear discontinuous.
[CuCl2L2] complex can in principle be found in doublet, quartet
and sextet spin states with one, three and five unpaired electrons,
respectively. The present DFT calculations exclusively predict dou-
blet ground state with one unpaired electron for the complex at the
room temperature (Table 3). The quartet and sextet spin states lie
ꢂ80 and ꢂ160 kcal/mol above the ground-state doublet, respec-
tively. Thus these two higher energy spin states are not accessible
at the room temperature. DFT calculations predict the Cu–N bonds
by 0.17 Å shorter than the Cu–Cl bonds (Table 4).
2.3. Dispersive Raman measurements
The room temperature 3500–50 cmꢁ1 region Raman spectra of L
and [CuCl2L2] were recorded with Dispersive Raman Microscope
(DXR) by using a laser of 532 nm wavelength. At the laser powers
that do not burn the present dark-colored complex, a good-re-
solved dispersive Raman spectrum could not be recorded.
2.4. EPR measurement
4.2. Vibrational assignments
A conventional X-Band Bruker EMX model EPR spectrometer
employing an AC magneticfield (5 kHz) modulation technique
All observed IR and Raman normal modes of L and [CuCl2L2]
(Figs. 2–4) have been assigned with the aid of DFT calculations (Ta-
ble 5). The DFT calculations overestimate generally the vibrational
frequencies due to the neglect of crystal packing effects and anhar-
monicity as well as the basis set and electronic correlation incom-
pleteness. Therefore, we derived scaling factors on L and applied
them to [CuCl2L2] to approximately account for the computational
errors. For the frequencies above and below 1623 cmꢁ1, the BVP86
scaling factors are 0.974 (R2 = 0.79) and 1.005 (R2 = 0.996) and, the
Table 1
Elemental analysis of the [CuCl2L2] as percentage.
Comp.
Found (cal.)%
Cu
C
N
H
[CuCl2L2]
(Theoretical)
18.49
(18.22)
48.16
(48.21)
7.84
(8.03)
5.17
(5.21)

78
T. Bardakçı et al. / Journal of Molecular Structure 1054–1055 (2013) 76–82
Fig. 1. The optimized geometries of (a) the ligand L (b) the complex [CuCl2L2].
Table 2
Geometry parameters of free L and [CuCl2L2].
Experimentala
BVP86 – 6-311G+(d,p)
L
B3LYP – 6-311G+(d,p)
L
[CuCl2L2]
[CuCl2L2]
Interatomic distance (Å)
C1AC2
C2AC3
C3AC4
C4AC5
C5AC6
C6AC1
CAN
CACH3
1.40
1.39
1.36
1.39
1.40
1.39
1.43
1.55
1.02
1.08
1.09
1.398
1.409
1.409
1.397
1.406
1.406
1.404
1.512
1.018
1.094
1.102
1.683
1.776
1.397
1.403
1.403
1.397
1.407
1.407
1.439
1.511
1.025
1.092
1.101
1.687
1.776
1.392
1.401
1.401
1.391
1.399
1.398
1.401
1.510
1.010
1.086
1.094
1.671
1.764
1.392
1.395
1.395
1.392
1.399
1.399
1.442
1.509
1.017
1.084
1.093
1.665
1.765
NAH
CAH (ring)
CAH (methyl)
Hꢃ ꢃ ꢃH (amino)
Hꢃ ꢃ ꢃH (methyl)
Angle (Degree)
C6AC1AC2
C1AC2AC3
C2AC3AC4
C3AC4AC5
121.5
119.2
120.3
120.5
120.5
117.8
121.8
120.6
118.0
120.6
121.8
117.2
120.9
121.4
111.6
111.5
107.2
115.0
121.5
119.6
119.9
119.6
121.5
117.8
120.0
121.1
110.8
111.4
108.1
112.0
121.7
120.6
118.1
120.6
121.7
117.2
120.9
121.4
111.7
111.4
107.5
115.3
120.6
118.1
120.6
121.7
121.7
117.2
120.9
121.4
111.7
111.4
107.5
115.3
C4AC5AC6
C5AC6AC1
N15AC3AC2 (C4)
C11AC6AC1 (C5)
HANAH
CACAH (methyl)
HACAH (methyl)
HANAC
113.0
109.5
a
Taken from Ref. [26].
B3LYP scaling factors are 0.952 (R2 = 0.79) and 0.976 (R2 = 0.996),
respectively. These scaling factors are similar to the previously de-
rived factors for L [3].
Table 3
Computed relative energies (kcal/mol) of different spin states of [CuCl2L2].
Relative energy (kcal/mol)
BVP86/6-311G+(d,p)
B3LYP/6-311G+(d,p)
4.2.1. NAH vibrations
Doublet
Quartet
Sextet
0.0
81.7
153.3
0.0
83.2
167.1
For primary amines, NAH strectching vibrations generally occur
at3500–3300 cmꢁ1 region [27,28]. In thisstudy, the asymmetricand
the symmetric N–H vibrations of L are observed at 3418 and
3337 cmꢁ1 in accordance with the literature. They downshift to
3301 and 3234 cmꢁ1, i.e., by 117 and 103 cmꢁ1, upon coordination.
The modes at ꢂ1600 and ꢂ1500 cmꢁ1 contain coupled C–C stretch-
ing and NH2 scissoring vibrations. They downshift by ꢂ15 cmꢁ1
upon coordination. The NH2 rocking vibration appears in the previ-
ous studies at 1074 cmꢁ1 for the free L and ꢂ1100 cmꢁ1 for its tran-
sition metal complexes [3,7,8,16,29]. Analogously, in this study, DFT
calculations show that NH2 rocking vibration (41%) occurs at
ꢂ1100 cmꢁ1 (scaled) for the complex, and at ꢂ1075 cmꢁ1 (scaled)
for the free L.
4.2.2. C–N vibrations
Mixing of the several bands makes the identification of C–N
vibrations difficult. Silverstein [30] assigned C–N stretching

T. Bardakçı et al. / Journal of Molecular Structure 1054–1055 (2013) 76–82
79
Table 4
Key geometry parameters of [CuCl2L2] complex in the gas phase around the coordination site at different spin states.
Interatomic distance (Å)
BVP86 6-311G+(d,p)
Cu–Cl
B3LYP 6-311G+(d,p)
Cu–Cl
Cu–N
Cu–N
Doublet
Quartet
Sextet
2.261–2.261
2.257–2.250
2.265–2.257
2.090–2.090
2.130–2.094
2.082–2.081
2.272–2.272
2.265–2.262
2.271–2.250
2.089–2.089
2.133–2.084
2.117–2.116
Fig. 2. The experimental mid region FT-IR spectra of L (top) and [CuCl2L2] (bottom).
Fig. 4. The experimental dispersive Raman spectra of
L (top) and [CuCl2L2]
(bottom).
for the complex. The symmetric C–H stretching appears at
2739 cmꢁ1 for L and at 2732 cmꢁ1 for the complex.
4.2.4. C–C vibrations
CC stretching modes are observed between the 1600 and
1200 cmꢁ1 region both for free L, and complex [CuCl2L2], as in line
with the previous study [3]. The CH in plane and out of plane bend-
ing vibrations usually couple with the C–C stretchings.
4.2.5. Metal–halogen and metal–ligand vibrations
The [ML2X2] complexes (M = metal; L = ligand; X = halogen)
with one M–L and two M–X stretching IR bands that are mostly
found below 600 cmꢁ1 [7,12,40] have molecular point group of Ci
and polymeric octahedral geometry around the metal center due
to packing in the solid state [41]. In the IR spectrum of the com-
plex, there is only one Cu–N stretching at 155 cmꢁ1 and two Cu–
Cl stretchings at 204 and 305 cmꢁ1. The present calculations find
the Cu–N and the Cu–Cl bond lengths of the complex different to
each other. These suggest distorted polymeric octahedral environ-
ment around the Cu(II) ion. It should be mentioned at this point
that the calculations are performed in the gas phase, i.e., for single
isolated molecules whereas the experiments refer to the solid-state
bridged polymerical samples. Therefore, the vibrational calcula-
tions are especially useful to examine how the coordination affects
the frequencies of the modes qualitatively.
Fig. 3. The experimental far region FT-IR spectra of L (top) and [CuCl2L2] (bottom).
vibration in the region 1382–1266 cmꢁ1 for aromatic amines.
Correspondingly to this information, in this study C–N stretching
vibration (11%) occurs at 1265 cmꢁ1 for the [CuCl2L2], and at
ꢂ1270 for the free L.
4.2.3. C–H vibrations
The aromatic C–H stretching vibrations appear in the region
3100–3000 cmꢁ1 [31–37]. They appear at ꢂ3200 cmꢁ1 for L, and
ꢂ3100 cmꢁ1 for the complex. The asymmetric and symmetric
methyl C–H stretchings appear usually in the regions of 2980–
2920 cmꢁ1 and 2870–2840 cmꢁ1, respectively [3,7–16,38,39]. Con-
sistent with these literature values, the asymmetric C–H stretch-
ings are at 2913 and 2860 cmꢁ1 for L and at 2915 and 2860 cmꢁ1
4.3. EPR study
The experimental and simulated EPR spectra of the [CuCl2L2]
complex recorded for its powder and ethyle alcohol solution forms
at the room temperature are shown in Fig. 5. Both spectra have
similar line shapes that are characteristic for a polycrystalline sam-
ple containing a paramagnetic ion with rhombic field symmetry.

80
T. Bardakçı et al. / Journal of Molecular Structure 1054–1055 (2013) 76–82
Table 5
Experimental and calculated wavenumbers of free L and [CuCl2L2].
Free L – 6-311G+(d,p)
[CuCl2L2] – 6-311G+(d,p)
Experimental
PED (%) assignments
Experimental
BVP86
B3LYP
BVP86
B3LYP
FT-IR
Disp.
Raman
Unscaled Scaled Unscaled Scaled FT-IR
Disp.
Raman
Unscaled Scaled Unscaled Scaled
3418 s
3337 s
3223 m
3419 m, sh 3572
3479 3660
3384 3564
3015 3166
3484 3301 s
3393 3234 s
3014 3158 w,
sh
3478
3385
3114
3388 3568
3297 3481
3033 3188
3397 100
3314 100
t
t
NH2 (asym.)
NH2 (sym.)
3336 s
3474
3095
3225 w
3035 91
t
CH ring
3096 w
3056 w,
sh
3092
3076
3012 3163
2996 3148
3011 3118 m
2997 3061 vw
3113
3092
3032 3187
3012 3165
3034 92
3013 90
t
t
CH ring
CH ring
3052 s
3010 m
2913 m
2860 m
3014 m, sh 3076
2996 3147
2954 3093
2926 3066
2996 3036 m
2945 2915 m
2919 2860 m,
sh
3092
3042
3013
3012 3164
2963 3102
2935 3075
3012 90
2953 97
2927 99
t
t
t
CH ring
CH3 (asym.)
CH3 (asym.)
2915 s
3033
3004
2860 m
2739 w
1623 vs
1581 w,
sh
2738 w
1615 s
2948
1618
1603
2871 3014
1626 1666
1611 1653
2869 2732 w
1626 1613 w
1613 1594 w
2954
1602
1581
2877 3021
1610 1653
1589 1638
2876 99
1613 81
1599 87 bNH2 (sciss.); 13 tCC
t
t
CH3 (sym.)
CC; 14 bNH2 (sciss.)
1607 sh
1456 vs
1572
1503
1453
1440
1580 1619
1511 1549
1460 1500
1447 1489
1580 1568 s
1512 1514 vs
1464
1580
1578
1495
1453
1588 1630
1586 1545
1502 1500
1460 1490
1591 68
1508 61 bCCH; 30 t
1464 62 bCH3 (asym.); 30 bCCH
1454 96 bCH3 (asym.)
t
CC; 17 bNH2 (rock.)
CC
1516 vs
1516 w
1381 m
1455 w,
sh
1453 1455 vw
1414
1363
1341
1421 1457
1370 1415
1348 1354
1422
1381 1379 w
1322
1440
1414
1363
1447 1459
1421 1415
1370 1363
1424 55 bCCH; 32 bCH3 (asym.); 13 bNH2
1381 93 bCH3 (sym.)
1330 63 bCCH; 21 bNH2; 12
1345 w,
sh
1354 s
tCC
1324 m
1270 s
1321 w
1275 m
1214 s
1298
1268
1202
1304 1331
1274 1294
1208 1232
1173 1204
1125 1151
1063 1090
1025 1061
1299 1327 w
1263
1349
1301
1214
1201
1168
1132
1093
1356 1335
1308 1239
1220 1231
1207 1207
1174 1168
1138 1130
1098 1061
1303 39 bCCH; 23 CC; 20 bCH3
t
1265 m
1209 48 bCCH; 21 bNH2; 11
1201 39 bCCH; 28 bCH3; 26
1178 80 bCCH
t
tCC
CC; 11
tCN
1202 1221 m
1175 1181 w
1123 1148 vw
1064 1091 s
1036 1044 m,
sh
1177 m
1124 m
1074 m
1044 vw
1178 w, sh 1167
1127 vw
1077 vw
1031 vw
1119
1058
1020
1140 41 bNH2 (rock.); 52 bCCH
1103 50 bCCH; 27 bNH2; 14 bCH3
1036 80
sCCC-CH3
1013 vw
998
1003 1030
1005 1022 m,
sh
976
1022 w
1019
1024 1038
1010 1022
1013 50 bCCH; 27 bNH2 (rock.); 13 bCCH3
954 w
931 vw
966
914
895
830
787
784
734
692
638
576
488
455
402
394
310
290
270
134
30
971
919
899
834
791
788
738
695
641
579
490
457
404
396
312
291
271
135
30
1000
961
939
850
824
820
750
718
659
592
508
469
418
410
321
299
264
139
28
1005
971
941
933
910
822
801
792
723
689
648
642
621
600
508
463
457
399
395
380
374
373
330
997
981
956
932
822
820
809
722
699
655
647
630
612
519
515
467
462
407
399
386
381
380
325
64
cNH2 (wag.); 33 cCCC
938
976
946
938
915
826
805
796
727
692
651
645
624
603
511
465
459
401
397
382
376
375
332
1005
979
955
842
840
829
740
716
671
663
645
627
532
528
478
473
417
409
395
390
389
333
65 bCH3; 25 bCH
83
66
916
830
804
800
732
701
643
578
496
458
408
400
313
292
258
136
27
963 vw
937 w
832 w, sh 843 w
c
c
CH; 15
CH; 13
c
c
CCC
CH3; 10
833 w, sh 840 vs
815 s
c
NH2
63 ring breath.; 18
t
CH3; 17 tCN
813 s
817 w
753 w
672 w
82
69
48
41
50
32
48
63
55
56
42
42
93
34
c
c
t
c
c
c
c
c
c
c
t
t
c
c
CH; 12
CCC; 16
c
c
t
c
CCC
CH3; 10
CCH3; 21
CCC; 20
750 sh
691 m
741 w
712 w
644 m
535 vw
c
t
NH2
CN
742 m
706 m
684 m
CC; 31
CH; 30
NH2 (wag.); 42
NH2 (wag.); 59
NH2 (wag.); 42
NH2 (wag.); 33
CCC; 17
CCC; 16
CCH3; 34
CCH3; 33
CCC
c
CH3
c
c
c
c
CCC
501 m
CCC
CCC
CCC
465 m
410 w
334 s
638 m
536 m
513 w, sh
486 w
473 vw
443 m
c
c
NH2 (wag.); 14
NH2 (wag.); 14
c
c
CH3
CH3
t
t
CN; 23
CN; 23
t
t
CC
CC
174 vw
131 w
460 w
412 w
CH; 33 cNH2; 23 cCH3
390 m
38 bCCH; 33 bCN; 27 bCCH3
39 bCCH; 32 bCN; 29 bCCH3
34
41 bCCH3; 27 bCCC; 16 bCN; 15
CuCl
374 vw
305 m
cCN; 31 cCCH3; 31 cCCC
t
281 m
270 vw
258 w
229 w
204 w
155 m
286
285
278
272
209
171
136
135
129
114
105
62
287
286
279
273
210
172
137
136
130
115
106
62
297
295
288
280
218
180
143
142
135
119
111
63
290
288
281
273
213
176
140
139
132
116
108
61
41 bCCH3; 37 bCN; 21 bCCC
38 bCCH3; 38 bCN; 21 bCCC
41
35
35
46
44
32
46
50
52
30
s
s
s
s
s
s
s
s
s
s
CCCH; 38
s
CCC-CH3; 19
s
s
t
t
CCCN
CCCN
CuCl
CuN
CCC-CH3; 36
CCC-CH3; 30
CCC-CH3; 25
CCCN; 25
CCC-CH3; 32
CCCN; 25 CCC-CH3; 22
CCC-CH3; 23
CCC-CH3; 25
CCC-CH3; 31
sCCCH; 23
sCCCN; 11
sCCCN; 11
s
CCC-CH3; 22 CCCH
s
137 w
123 w
107 w
92 w
s
CCCN; 18 cCuCl2
s
sCCCH
sCCCH
sCCCH
sCCCH
sCCCN; 19
sCCCN; 22
sCCCN; 34
76 w

T. Bardakçı et al. / Journal of Molecular Structure 1054–1055 (2013) 76–82
81
Table 5 (continued)
Free L – 6-311G+(d,p)
Experimental
[CuCl2L2] – 6-311G+(d,p)
PED (%) assignments
BVP86
B3LYP
Experimental
BVP86
B3LYP
FT-IR
Disp.
Unscaled Scaled Unscaled Scaled FT-IR
Disp.
Unscaled Scaled Unscaled Scaled
Raman
Raman
54
48
46
45
42
30
20
12
54
48
46
45
42
30
20
12
56
47
46
38
37
30
19
12
55
46
45
37
36
29
19
12
48
50
43
84
78
40
47
59
s
s
s
c
c
CCC-CH3; 27
CCC-CH3; 29
CCC-CH3; 41
CH3
CH3; 19 sCCCH
s
s
s
CCCN; 10
CCCN; 21
CCCH; 14
cCuCl2
sCCCH
s
CCCN
sCCC-CH3; 28
sCCC-CH3; 21
sCCC-CH3; 18
sCCCH; 15
sCCCN; 27
sCCCN; 18
s
s
CCCN
CCCH
c
CuCl2
t
, stretching; s, torsion; b in plane deformation; c out of plane deformation.
However, the crystallite symmetry axes of each powder molecule
are subjected to every possible direction of any externally applied
DC magnetic field. Hence, the overall paramagnetic system exhibits
resonances at all fields, BR varying between perpendicular and par-
allel aligments. For a general orientation of a single crystallite con-
taining a paramagnetic ion, the resonance field is obtained from Eq.
(1) [42,48–51] as
BR ¼ hf=geff be
h
i
¼
g2x sin2 h cos2 h þ gy2 sin2 h sin2 h þ gz2 cos2 h ꢁ1=2hf=be
ð2Þ
where the angles h and Ø describe the orientation of the magnetic
field H in the g-tensor principal axis, h and f are the Plank’s constant
and the microwave frequency, respectively. Exact theoretical fit of
experimental spectra requires summation from 0 to 90 degrees
both for h and Ø.
The probability of each spin center experiencing a resonant field
is proportional to Sinh. The intensities of the absorption resonance
peaks can be thus obtained by inserting a weighting factor in Eq.
(2) [11,52,53]. As the resonance curves of each individual magnetic
center have their own intrinsic line shapes and widths for the pow-
der systems, the line width and line shape characteristics of spec-
tra are analyzed in detail by EPR spectroscopy. These curves reach
to their maximum at the resonance field BR. That is, regardless of
how far it is from the exact resonance field, BR, any center can give
absorption at any field even if it becomes undetectable experimen-
tally. The contribution from any center to the whole absorption
line at any field depends on the intrinsic line width. Therefore,
an angle-dependent equation is used to describe the line width
characteristics [42,54].
Fig. 5. The experimental and simulated room temperature X-band EPR spectra of
[CuCl2L2] as powder and in EtOH solution.
Many Cu(II)-coordinated complexes exhibit hyperfine peaks or
quasi-isotropic behavior (almost a single peak) due to solvent ef-
fects [42,43]. Although any part of the recorded EPR spectra does
not include any hyperfine peak, the solution spectrum has a shoul-
der at its parallel part and the amplitude of perpendicular part is
smaller compared with the powder EPR spectrum. Each part would
have 4 peaks due to nuclear spin (I = 3/2) of copper atom. gx and gy
can be defined as the Lande splitting factors when the externally
applied DC field is in perpendicular while gz is in parallel align-
ment, respectively. They follow the trend gz > gy > gx and
g//>g\ > ge (ge is free electron g-value) suggesting Cu complexes
have approximate axial symmetry D4h (square planar, or octahe-
dral with tetragonal distortion) with B1g as the ground state of
Cu(II) ion [16,44]. The unpaired electron is located mainly on the
b1g antibonding molecular orbital, which is the linear combination
of d2x ꢁ y2 orbital of the copper and ØL ligand orbital of the adequate
symmetry [45–47]. The character of the Cu complexes can be esti-
mated from the g// (or gz) values which are sensitive to the bond
covalency [45]. The centers giving gz P 2.3 are ionic in their nature
and gz < 2.3 have the dominant covalent character. Our sample has
gz ꢄ 2.18 values for both powder and solution forms.
W2eff ¼ W2x sin2 h cos2 £ þ Wy2 sin2 h sin2 £ þ W2z cos2 h
ð3Þ
To simulate the experimental spectra, we wrote a software in
Matlab scientific language. The best fit is obtained by using the
Lorentzian line shape function for intrinsic line properties (see
Fig. 5). The simulations reveal that the solution and powder spectra
have almost the same magnitude of EPR and line width fit param-
eters (see Table 6) and exhibit all characteristics features of the EPR
peaks except the additional weak shoulder due to solvent. Since
the environment of paramagnetic ion is not affected much from
the solution due to its polymeric nature, the powder and solution
EPR spectra are quite similar.
ˆ
The anisotropic spin-Hamiltonian Haiso of rhombic symmetry is
given by the expression
b
b
b
b
Haiso ¼ beðgxBx Sx þ gyBy Sy þ gzBz SzÞ
ð1Þ
5. Conclusions
where be and S denote Bohr magneton and the electronic spin angu-
lar momentum of the magnetic ion, respectively.
The FT-IR (including mid and far regions) and dispersive Raman
spectral studies of free L and the synthesized [CuCl2L2] complex,
where L = 4-amino-1-methylbenzene, have been performed. The
In a randomly oriented powder system, each paramagnetic
center has similar properties as it would have in a large crystal.

82
T. Bardakçı et al. / Journal of Molecular Structure 1054–1055 (2013) 76–82
H.P. Hratchian, J.B. Cross, V. Bakken, C. Adamo, J. Jaramillo, R. Gomperts, R.E.
Table 6
Stratmann, O. Yazyev, A. J. Austin, R. Cammi, C. Pomelli, J.W. Ochterski, P.Y.
Ayala, K. Morokuma, G.A. Voth, P. Salvador, J.J. Dannenberg, V.G. Zakrzewski, S.
Dapprich, A.D. Daniels, M.C. Strain, O. Farkas, D.K. Malick, A.D. Rabuck, K.
Raghavachari, J.B. Foresman, J.V. Ortiz, Q. Cui, A.G. Baboul, S. Clifford, J.
Cioslowski, B.B. Stefanov, G. Liu, A. Liashenko, P. Piskorz, I. Komaromi, R.L.
Martin, D.J. Fox, T. Keith, M.A. Al-Laham, C.Y. Peng, A. Nanayakkara, M.
Challacombe, P.M.W. Gill, B. Johnson, W. Chen, M.W. Wong, C. Gonzalez, J.A.
Pople, Gaussian 03, Revision C.02, Gaussian, Inc., Wallingford CT, 2004.
[19] GaussView, Version 4.1, Roy Dennington II, Todd Keith and John Millam,
Semichem, Inc., Shawnee Mission, KS, 2007.
Anisotropic EPR and line width simulation parameters of [CuCl2L2].
Samples
gx
gy
gz
gave
Wx
Wy
Wz
(Oe)
(Oe)
(Oe)
Powder form 2.008 2.037 2.184 2.076 10
10
10
10
10
Solution
form
2.009 2.038 2.185 2.077 10
The average g-factor is calculated from expression, gave = (gx + gy + gz)/3.
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geometry and vibrational spectra of the isolated complex in the gas
phase have been calculated with BVP86 and B3LYP density func-
tionals using the 6-311G+(d,p) basis set. The calculated vibrational
frequencies of the free and complexed L after a scaling procedure
agree reasonably well with the corresponding experimental fre-
quencies. The experimental vibrational and EPR spectra suggest
that the [CuCl2L2] complex has distorted polymeric octahedral
geometry around the Cu(II) center and coordination takes place
through nitrogen atom of the free ligand, and the calculations find
the title complex as a doublet with one unpaired electron.
Acknowledgement
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Authors would like to thank Dr. Ahmet Altun for critically read-
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