Mono, bi- and trinuclear metal complexes derived from new benzene-1,4-bis(3-pyridin-2-ylurea) ligand. Spectral, magnetic, thermal and 3D molecular modeling studies

Article abstract of DOI:10.1016/j.saa.2013.03.016

New bis (pyridylurea) ligand, H₂L, was synthesized by the reaction of ethylpyridine-2-carbamate (EPC) and p-phenylenediamine. The ligand was characterized by elemental analysis, IR, ¹H NMR, electronic and mass spectra. Reaction of the prepared ligand with Co²⁺, Ni ²⁺, Cu²⁺, Fe³⁺, VO²⁺ and UO22+ ions afforded mono, bi- and trinuclear metal complexes. Also, new mixed ligand complexes of the ligand H₂L and 8-hydroxyquinoline (8-HQ) with Co²⁺, Ni²⁺, Cu²⁺ and Fe³⁺ ions were synthesized. The ligand behaves as bi- and tetradentate toward the transition metal ions, coordination via the pyridine N, the carbonyl O and/or the amidic N atoms in a non, mono- and bis-deprotonated form. The complexes were characterized by elemental and thermal analyses, IR, electronic and mass spectra as well as conductance and magnetic susceptibility measurements. The results showed that the metal complexes exhibited different geometrical arrangements such as square planar, tetrahedral, octahedral and square pyramidal arrangements. The Coats-Redfern equation was used to calculate the kinetic and thermodynamic parameters for the different thermal decomposition steps of some complexes. 3D molecular modeling of the ligand, H₂L and a representative complex were studied.

Full text of DOI:10.1016/j.saa.2013.03.016

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 110 (2013) 205–216
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Spectrochimica Acta Part A: Molecular and
Biomolecular Spectroscopy
journal homepage: www.elsevier.com/locate/saa
Mono, bi- and trinuclear metal complexes derived from new
benzene-1,4-bis(3-pyridin-2-ylurea) ligand. Spectral, magnetic,
thermal and 3D molecular modeling studies
⇑
Mosad A. El-ghamry , Akila A. Saleh, Saied M.E. Khalil, Amira A. Mohammed
Department of Chemistry, Faculty of Education, Ain Shams University, Roxy, Cairo, Egypt
h i g h l i g h t s
g r a p h i c a l a b s t r a c t
The optimized structure of the ligand, H2L.
ꢀ
ꢀ
New bis (pyridylurea) ligand was
prepared.
The structure of the ligand was
studied by different spectroscopic
techniques.
ꢀ
ꢀ
ꢀ
The solid complexes of the prepared
ligand with some metal ions were
isolated.
The spectral, magnetic and thermal
properties of these complexes were
studied.
3D molecular modeling of the ligand
and a representative complex were
studied.
a r t i c l e i n f o
a b s t r a c t
Article history:
New bis (pyridylurea) ligand, H2L, was synthesized by the reaction of ethylpyridine-2-carbamate (EPC)
and p-phenylenediamine. The ligand was characterized by elemental analysis, IR, 1H NMR, electronic
and mass spectra. Reaction of the prepared ligand with Co2+, Ni2+, Cu2+, Fe3+, VO2+ and UO22þ ions afforded
mono, bi- and trinuclear metal complexes. Also, new mixed ligand complexes of the ligand H2L and 8-
hydroxyquinoline (8-HQ) with Co2+, Ni2+, Cu2+ and Fe3+ ions were synthesized. The ligand behaves as
bi- and tetradentate toward the transition metal ions, coordination via the pyridine AN, the carbonyl
AO and/or the amidic AN atoms in a non, mono- and bis-deprotonated form. The complexes were char-
acterized by elemental and thermal analyses, IR, electronic and mass spectra as well as conductance and
magnetic susceptibility measurements. The results showed that the metal complexes exhibited different
geometrical arrangements such as square planar, tetrahedral, octahedral and square pyramidal arrange-
ments. The Coats–Redfern equation was used to calculate the kinetic and thermodynamic parameters for
the different thermal decomposition steps of some complexes. 3D molecular modeling of the ligand, H2L
and a representative complex were studied.
Received 12 November 2012
Received in revised form 18 February 2013
Accepted 3 March 2013
Available online 13 March 2013
Keywords:
Bis (pyridylurea) ligand
Mono-, bi- and trinuclear metal complexes
Magnetic
Thermal studies
Molecular modeling
Ó 2013 Elsevier B.V. All rights reserved.
Introduction
in electrochemical processes, antimicrobial and antitumour activi-
ties [1–6]. The coordination chemistry of pyridyl ureas is extremely
Heterocyclic nitrogen ligands have been studied well because
their interesting coordination chemistry and potential applications
rich. Such compounds act as multidentate ligands towards transi-
tion metals, coordination via the pyridine nitrogen atoms, the car-
bonyl oxygen atoms and the amide nitrogen atoms of the ligands in
a non-, mono- and bis-deprotonated form are known [7]. Also,
these ligands have been extensively used to construct various
⇑
Corresponding author. Tel.: +20 01007462713.
E-mail address: mosadelghamry@yahoo.com (M.A. El-ghamry).
1386-1425/$ - see front matter Ó 2013 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.saa.2013.03.016

206
M.A. El-ghamry et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 110 (2013) 205–216
structures and functions through cooperative binding of transition
metals and anions [8,9]. Pyridine amide compounds have been em-
ployed in catalysis [10,11]. Many derivatives of pyridine amide
show anti-flammatory, antipyretic and analgesic activities and
they are useful in the treatment of atherosclerosis [12]. Some Pt(II)
complexes with amide compounds demonstrated notable antitu-
mour and anticancer activity [13–17].
The work reported herein is focused on the synthesis and char-
acterization of mono, bi- and tri-nuclear Co2+, Ni2+, Cu2+, Fe3+, VO2+
and UO22þ complexes of new benzene-1,4-bis(3-pyridin-2-ylurea)
ligand, H2L, derived from the reaction between ethylpyridine-2-
carbamate (EPC) and p-phenylenediamine, Scheme 1. Also, new
mixed ligand complexes of the ligand, H2L and 8-hydroxyquinoline
(8-HQ) with Co2+, Ni2+, Cu2+ and Fe3+ ions are synthesized. The
structure of the complexes are characterized by elemental and
thermal analyses, IR, UV–Vis, ESR and mass spectra as well as con-
ductivity and magnetic susceptibility measurements. In addition,
the kinetic and thermodynamic characteristics of the decomposi-
tion steps of some complexes have been studied employing
Coats–Redfern equation.
were measured as a solution in DMF (10ꢁ3 M) using WTWD-812
Weilheium-conductivity meter model LBR, fitted with a cell model
LTA100. Microanalyses of carbon, hydrogen and nitrogen were car-
ried out at the microanalytical center, Cairo University, Giza, Egypt.
Analyses of the metals followed the dissolution of the solid com-
plex in concentrated HNO3 and titrating the metal solutions com-
plexometrically using 0.001 M EDTA solution [22]. ESR spectra of
the complexes were recorded on a Bruker, E500, X-band spectrom-
eter. TGA measurements were carried out on a shimadzu-50 ther-
mal analyzer. Melting points of the compounds were determined
using a Stuart melting points instrument.
Synthesis of the organic ligand, H2L
The ligand, H2L, was prepared in two steps, Scheme 1.
Preparation of ethylpyridine-2-carbamate (EPC)
Ethylchloroformate (1.09 g, 10 mmol) was added dropwise to 2-
aminopyridine (0.94 g, 10 mmol) with one drop of piperidine, the
reaction mixture was allowed to stand in ice-bath for few minutes
due to the exothermic behavior of the reaction, after that the reac-
tion mixture was fused on a hot plate under reflux for 6 h. The
product was allowed to cool till room temperature, solidified by
ethanol and diethylether, filtered off and recrystallized from etha-
nol then dried under vacuum to give buff crystals, yield 44%, m.p.
180 °C.
Experimental
Materials
Metal salts, ethylchloroformate, 2-aminopyridine, p-phenylene-
diamine, 8-hydroxyquinoline, EDTA, nitric acid were Aldrich, BDH
or Merck products. Organic solvents were either spectroscopically
pure or purified by the recommended methods [18–20] and tested
for their spectral purity.
Preparation of benzene-1,4-bis(3-pyridin-2-ylurea), the ligand, H2L
A mixture of EPC (3.32 g, 20 mmol) and p-phenylenediamine
(1.08 g, 10 mmol) in DMF (20 ml) was refluxed on a hot plate for
4 h. The reaction mixture was allowed to cool till room tempera-
ture, poured on crushed ice, filtered off and recrystallized from eth-
anol then dried under vacuum to give gray crystals, yield 58%,
m.p. > 300 °C. The molecular formula of the ligand (C18H16N6O2,
M.Wt = 348) is in good agreement with the stoichiometry con-
cluded from analytical data and mass spectra.
Physical measurements
FT-IR spectra were recorded on a Perkin–Elmer 293 spectrome-
ter (4000–400 cmꢁ1) in KBr pellets. Electronic spectra were re-
corded at room temperature on a Shimadzu model UV-1601 PC
spectrophotometer (200–800 nm) as solutions in DMF. The 1H
NMR spectrum of the ligand as a solution in DMSO-d6, were re-
corded on a Varian (FT-290), 90 MHz spectrometer at room tem-
perature using TMS as an internal standard. Mass spectra were
recorded at 300 °C and 70 ev on a shimadzu QP spectrometer mod-
el MS-5988. Magnetic susceptibilities of the complexes were mea-
sured by the Gouy method at room temperature using a Johnson
Matthey, Alfa products, Model MKI magnetic susceptibility bal-
ance. The effective magnetic moments were calculated from the
Synthesis of the metal complexes
Ethanolic solutions of the ligand, H2L, and the metal salt,
Cu(NO3)2ꢂ3H2O, Ni(NO3)2ꢂ6H2O, Co(NO3)2ꢂ6H2O, Fe(NO3)3ꢂ9H2O,
VOSO4ꢂH2O or UO2(CH3COO)2ꢂ2H2O were mixed in a 1:1, 1:2 and
1:3 (L:M) molar ratio. In the preparation of all complexes (except
Fe3+ and UO22þ complexes), 0.1 g of sodium acetate was added as
a buffering agent to raise the PH to 5. The resulting solutions were
stirred for about 1 h then refluxed on a hot plate from 6 to 8 h. The
solid complexes which separated out on hot were filtered off,
washed with hot ethanol and diethylether and finally dried in vac-
uum desiccator over anhydrous CaCl2.
expression l
eff = 2.828 (XMT)1/2 B.M., where XM is the molar suscep-
tibility corrected using Pascal’s constants for the diamagnetism of
all atoms in the compounds [21]. The conductivities of complexes
O
O
drop of piperidine
C
Cl
OC2H5
+
C
fussion
N
N
NH2
NH
(6 h)
N
NH
OC2H5
(EPC)
O
C
DMF
reflux (4 h)
2
H2N
NH2
+
OC2H5
O
O
N
H
N
H
N
N
N
H
N
H
ligand (H2L)
Scheme 1. Synthesis of the ligand, H2L.

M.A. El-ghamry et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 110 (2013) 205–216
207
Table 1
Analytical and physical data of the metal complexes.
Complex
Molecular
formula
Color
Yield
(%)
m. p. (°C) Elemental analysis, found
Formula weight
Xm
(X )
ꢁ1 cm2 molꢁ1
(calcd.)
C (%)
H
N (%)
M (%) Founda Calcd.
(%)
1
2
3
4
5
6
7
8
9
[Co2(HL)2](NO3)2
C36H30N14O10Co2
C54H45N19O9Co2
C36H28N10O10Co2
Brown
80.05
>300
>300
>300
>300
>300
>300
>300
>300
>300
>300
>300
>300
>300
>300
45.6
2.8
20.1
13.6
935.5
–
935.8 108.3
(46.2) (3.2) (20.9) (12.6)
52.4 2.9 21.1 10.2
(53.1) (3.7) (21.8) (9.6)
50.6 3.0 16.4 13.7
(49.2) (3.2) (16.0) (13.4)
44.9 3.1 18.6 11.2
(45.6) (3.8) (19.6) (11.7)
41.1 2.7 18.0 17.0
(41.4) (3.2) (19.0) (16.0)
48.4 2.9 17.5 13.7
(49.2) (3.2) (16.0) (13.4)
46.4 2.5 19.8 13.8
(45.7) (3.2) (20.7) (13.4)
42.8 2.4 19.4 18.7
(42.9) (2.8) (19.5) (18.9)
58.9 2.8 17.0 12.3
(58.4) (3.8) (17.6) (11.5)
52.6 3.1 21.7 6.5
(52.1) (3.9) (21.9) (6.7)
50.6 3.2 19.6 8.4
(50.9) (4.1) (20.5) (8.2)
57.3 3.2 21.8 6.4
(56.4) (3.9) (20.5) (5.8)
59.1 3.5 22.4
(56.8) (3.9) (22.1) (6.6)
44.2 2.8 17.7
(44.8) (3.1) (17.4) (24.6)
[Co2(HL)3]NO3
Pale brown 81.36
1220.8
877.8
69.4
96.4
[Co2(H2L)(8-HQ)2](NO3)2
Buff
86.34
88.34
877.0
1000.2
–
[Ni2(HL)2](NO3)2ꢂH2OꢂEtOH C38H38N14O12Ni2
Green
999.4 126.8
[Ni3(L)(HL)(NO3)3(EtOH)]
[Ni2(H2L)(8-HQ)2](NO3)2
[Cu2(HL)2](NO3)2
C38H35N15O14Ni3
C36H28N10O10Ni2
C36H30N14O10Cu2
C36H28N14O10Cu3
C54H42N14O6Cu2
C36H32N13O8Fe
Dark green 90.60
1101.1
877.4
25.7
91.7
Green
Brown
70.83
88.99
878.0
946.3
–
945.0 115.6
[Cu3(L)2(NO3)2]
Pale brown 85.32
1006.5
1109.0
830.0
1368.0
957
26.2
28.7
29.9
13.4
39.4
6.4
[Cu2(HL)2(8-HQ)2]
Green
Brown
Brown
94.40
71.84
70.28
75.12
85.55
78.80
–
10 [Fe(HL)2(NO3)(H2O)]
830.0
–
11 [Fe2(HL)2(L)(NO3)2(EtOH)2] C58H56N20O14Fe2
12 [Fe(H2L)(HL)(8-HQ)]NO3
13 [VO(HL)2]
C45H37N14O8Fe
C36H30N12O5V
C36H30N12O6U
Dark
brown
Green
957.5
760.3
964.4
–
760.9
964
14 [UO2(HL)2]
Pale gray
–
5.9
a
Value obtained from mass spectra.
Synthesis of mixed ligand complexes
1692 corresponding to t(C@O) amide and bands due to the
An ethanolic solution of the metal salt, Cu(NO3)2ꢂ3H2O,
Ni(NO3)2ꢂ6H2O, Co(NO3)2ꢂ6H2O or Fe(NO3)3ꢂ9H2O was added grad-
ually to an ethanolic solution of the ligand, H2L, in the molar ratio
1:2 (L:M). The resulting solutions were stirred for 0.5 h, then an
ethanolic solution of 8-hydroxyl-quinoline (8-HQ) was added to
the previous solution in the molar ratio 2:2 (8-HQ:M). The solu-
tions were continuously stirred for 2 h then refluxed on a hot plate
from 6 to 8 h. The solid complexes which separated out on hot
were filtered off, washed with hot ethanol then diethylether and fi-
nally dried in vacuum desiccator over anhydrous CaCl2. All of the
complexes prepared were stable at room temperature, non-hygro-
scopic, insoluble in common organic solvents except DMF. The
analytical and physical data for the metal complexes are collected
in Table 1.
stretching frequencies of the pyridine ring appeared at 1578 and
1503 [24,25]. 1H NMR spectral data (d ppm) of the ligand relative
to TMS in DMSO-d6 without and with D2O give further support
of the suggested structure of the ligand. The aromatic proton sig-
nals of phenylene and pyridine rings appeared at 6.41–8.24, the
proton signals of NH groups at 9.37 and 10.43 completely disap-
peared on adding D2O. The electronic spectrum of the ligand
(10ꢁ3 M in DMF), Table 3, kmax (nm). Three bands at 238, 285
and 376 were characterized and can be assigned to
p–
pꢃ transi-
tions within the aromatic rings,
p–
pꢃ transitions within C@O and
an intramolecular charge transfer (CT) transition within the whole
molecule. The mass spectrum of the ligand, Fig. 1, showed the
molecular ion peak at m/e = 348 amu, confirming its formula
weight (F. W. = 348). The mass fragmentation pattern, shown in
Scheme 2, supported the suggested structure of the ligand.
The optimized structure of the ligand was given in Fig. 2 and
structural parameters were evaluated by means of a semi-empiri-
cal molecular orbital calculations at the PM3 level provided by
Hyperchem 7.5 program. These data are found to be, surface area
(Å2) = 498.80, volume (Å3) = 1001.22, HOMO energy (ev) = ꢁ8.45,
LUMO energy (ev) = ꢁ0.45, heat of formation (Kcal/mol) = 28.66,
3D molecular modeling studies
The 3D molecular modeling of the ligand, H2L and a representa-
tive complex was carried out on a Hyperchem 7.5 program [23]. It
is an interactive graphics program that allows rapid structure
building, geometry optimization with minimum energy and
molecular display. It has ability to handle transition metal
compounds.
electronic energy (ev) = ꢁ668960.38, dipole moment
bye) = 4.76 and bonds length C@O (C9AO10
C21AO22) = 1.21 Å.
l
(De-
and
Results and discussion
Characterization of the metal complexes
Characterization of the ligand
On the basis of elemental analysis, the metal complexes of the
ligand, H2L, were assigned to posses the compositions and molec-
ular formulae listed in Table 1. The results reveal that the ligand,
H2L, acts as bi- and tetradentate towards the metal ions via the
pyridine AN, the carbonyl AO and/or the amide AN atoms in a
non, mono- and bis-deprotonated form.
The structure of the ligand, H2L, was investigated by elemental
analyses, IR, 1H NMR, UV–Vis and mass spectra. Anal. Calcd.%: C,
62.06; H, 4.59; N, 24.13. Found%: C, 61.50; H, 3.75; N, 23.50. The
IR spectrum (cmꢁ1) of the ligand, Table 2, showed characteristic
bands at 3291 and 3053 corresponding to t(NH), strong band at

208
M.A. El-ghamry et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 110 (2013) 205–216
Table 2
Important IR spectral data and their assignment for the ligand H2L and its metal complexes.
IR spectral bands (cmꢁ1
(OH) (H2O/ (NH)
No. Compound or complex
)
t
t
t
(C@O)
Pyridine stretching
vibrations
t
(MAO)
t
(MAN) Other bands
EtOH)
H2L
–
3291,
3053
3291,
3066
3294,
3069
3289,
3073
3289,
3057
3289,
3076
3290,
3072
3291,
3056
3291,
3058
3291,
3052
3289,
3054
3290,
3055
3292,
3055
3290,
3055
3294,
3056
1692
1578, 1503
1572, 1486
1573, 1482
1570, 1482
1579, 1495
1569, 1482
1572, 1477
–
–
–
1
[Co2(HL)2](NO3)2
–
–
–
1681,
1624
1681,
1623
1676,
1623
1689,
1625
1681,
1624
1680,
1623
519
521
516
519
522
513
516
517
518
–
425
422
427
423
437
424
457
432
411
435
433
411
418
416
t
t
t
t
t
NOꢁ3 ionic 1405
2
[Co2(HL)3]NO3
NOꢁ3 ionic 1405
3
[Co2(H2L)(8-HQ)2](NO3)2
NOꢁ3 ionic 1387
4
[Ni2(HL)2](NO3)2ꢂH2OꢂEtOH 3480 (br)
NOꢁ3 ionic 1409
5
[Ni3(L)(HL)(NO3)3(EtOH)]
[Ni2(H2L)(8-HQ)2](NO3)2
[Cu2(HL)2](NO3)2
3500 (br)
NOꢁ3 monodentate 1390, 1321,
1220
6
–
t
t
t
NOꢁ3 ionic 1383
7
–
1689,1617 1578, 1483
NOꢁ3 ionic 1412
8
[Cu3(L)2(NO3)2]
–
1673
1576, 1482
1579, 1474
1579, 1511
1580, 1509
1578, 1507
1580, 1505
1580, 1508
NOꢁ3 bidentate 1410, 1322, 1221,
1053
–
9
[Cu2(HL)2(8-HQ)2]
–
1693,
1623
1697
10
11
12
13
14
[Fe(HL)2(NO3)(H2O)]
3460 (br)
t
NOꢁ3 monodentate 1409, 1316,
1222
NOꢁ3 monodentate 1411, 1310,
1224
t
NOꢁ3 ionic 1411
[Fe2(HL)2(L)(NO3)2(EtOH)2] 3440 (br)
1696
–
t
[Fe(H2L)(HL)(8-HQ)]NO3
[VO(HL)2]
–
–
–
1694,
1632
1693
518
–
t
t
(V@O) 976
[UO2(HL)2]
1694
–
(O@U@O) 943
Table 3
Electronic absorption spectral data (in DMF solution) and magnetic moment values.
a
b
No. Compound or complex Electronic spectral bands k (nm)
leff
lcompl
(B.M.) (B.M.)
p
–
pꢃ
emax
p–
pꢃ
emax
CT
emax
d–d
emax
(aromatic (molꢁ1 cmꢁ1 L) (C@O) (molꢁ1 cmꢁ1 L)
(molꢁ1 cmꢁ1 L) transition (molꢁ1 cmꢁ1 L)
system)
H2L
238
245
249
237
109
161
1680
137
261
341
368
537
4408
260
262
570
278
158
150
285
316
301
321
303
297
321
307
312
316
318
298
307
297
298
375
436
3940
217
424
627
719
1116
10857
420
498
3840
544
330
351
376 44
390 520
399 211
405 214
416 82
404 75
410 681
412 758
410 6313
410 397
385 428
385 266
428 94
399 51
509 24
–
–
72
39
83
56
42
99
234
1703
147, 43
124
56
106
10
–
–
–
1
2
3
4
5
6
7
8
[Co2(HL)2](NO3)2
[Co2(HL)3]NO3
[Co2(H2L)(8-HQ)2](NO3)2
528
534
524
537
539
545
523
524
529, 746
536
545
539
568
–
3.67
4.32
3.83
2.74
2.83
2.51
1.81
1.64
1.98
2.80
3.97
2.43
2.24
–
5.20
6.11
5.42
3.88
4.93
3.55
2.56
2.83
2.80
2.80
5.61
2.43
2.24
–
[Ni2(HL)2](NO3)2ꢂH2OꢂEtOH 253
[Ni3(L)(HL)(NO3)3(EtOH)]
[Ni2(H2L)(8-HQ)2](NO3)2
[Cu2(HL)2](NO3)2
240
256
225
212
248
249
[Cu3(L)2(NO3)2]
[Cu2(HL)2(8-HQ)2]
[Fe(HL)2(NO3)(H2O)]
[Fe2(HL)2(L)(NO3)2(EtOH)2] 219
[Fe(H2L)(HL)(8-HQ)]NO3
[VO(HL)2]
[UO2(HL)2]
9
10
11
12
13
14
220
249
244
a
leff (B.M.) of one cationic species in the complexes.
leff (B.M.) the total magnetic moments of all cations in the complex.
b
Molar conductivities of the complexes were measured in DMF
(10ꢁ3 M solution), Table 1. The complexes 5, 8, 9, 10, 11, 13 and
14 have Xm values in the range 5.9–29.9
ꢁ1 cm2 molꢁ1 which fall
12 may be due to the low mobility of its bulk cations. The com-
plexes 1, 3, 4, 6 and 7 have Xm values in the range 91.7–126.8 Xꢁ1
-
X
cm2 molꢁ1 which fall in the range of 1:2 electrolytes [26].
within the range of non-electrolytes. The observed Xm values of
some complexes may be due to displacement of part of coordi-
nated NOꢁ3 ions by DMF solvent molecules. It has been reported
that DMF is a good donor solvent and can replace NOꢁ3 from the
coordination sphere of the metal complexes [26]. The Xm values
IR spectra and mode of bonding
The IR spectral data of the metal complexes and their tentative
assignments are listed in Table 2. Complexes 4, 5, 10 and 11
showed a broad band in the range 3500–3440 cmꢁ1 assigned to
of the complexes 2 and 12 are 69.4 and 39.4
X
ꢁ1 cm2 molꢁ1
,
t(OH) of the coordinated or uncoordinated H2O and/or EtOH mol-
respectively (1:1 electrolytes). The low value of Xm of complex
ecules associated with the complexes, which are confirmed by ele-

M.A. El-ghamry et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 110 (2013) 205–216
209
Fig. 1. Mass spectrum of the ligand, H2L.
(2) (1)
(3)
O
O
(1)
(2)
+
H
H
H
H
N
(3)
.
N
N
N
HNOCHN
-C5H4N
or - C6H6N2
N
H
N
H
HNOCHN
N
N
N
O
O
N
M m/z 348 (7.16%)
N
o
r
-
C
m/z 242 (2.76 %)
H
N
m/z 270 (3.46 %)
O
(1)
-C12H10N4O2
(2)
-C10H10N4
,
+
H
-2CO
-H2
.
.
+2H
+2H
H2
N
NH2
-C2H2
NH2
.
.
m/z 82 (100 %)
(base peak)
N
N
H
H
N
N
H
N
H
NH2
N
N
H2N
-2CO
m/z 184 (15.69 %)
O
O
m/z 94 (70.84 %)
m/z 108 (32.43 %)
-N2
m/z 164 (9.75 %)
-H2
+
HNOCHN
NHCONH2
HN
NH
N
N
N
N
m/z 186 (9.26 %)
m/z 193 (3.72 %)
.
m/z 156 (20.35 %)
-NHCONH2
-2C2H2
HN
O
C
N
HN
N
2
3
-
m/z 134 (36.46 %)
m/z 104 (17.11 %)
.
.
-C N
+H
.
+
+
NH2
-C H3
.
.
.
+H
-CH2NH2
+
-H2N-CO
HN
O
+
.
.
H2
N
N
+2H
+H
m/z 78 (15.68 %)
m/z 64 (73.82 %)
m/z 92 (4.59 %)
Scheme 2. Mass fragmentation pattern of the ligand.
m/z 135 (5.73 %)
Fig. 2. The optimized structure of the ligand, H2L.

210
M.A. El-ghamry et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 110 (2013) 205–216
mental and thermal analyses. Two bands appearing at 1578 and
1503 cmꢁ1 are assigned to pyridine ring stretching vibrations in
the free ligand, the 1578 cmꢁ1 band shows a slight shift to lower
or higher wavenumber but the 1503 cmꢁ1 band shows a shift to
lower frequency by 8–29 cmꢁ1 indicating the coordination of the
pyridine nitrogen atoms to the metal ions [27]. In case of com-
mixed ligand complex (9) showed two absorption bands at 746
and 529 nm, which can be assigned to 2B1g ? 2Eg and 2B1g ? 2B2g
transitions within octahedral structure [45]. The observed mag-
netic moment value of complex (9) is 1.98 B.M. which indicates
the presence of one unpaired electron per the Cu(II) ion, also con-
firming its octahedral geometry [46]. The values showed the pres-
ence of some spin–spin interaction between Cu(II) ions in the
different complexes.
The effective magnetic moment values of Co(II) complexes,
binuclear complexes [Co2(HL)2](NO3)2 (1), [Co2(HL)3]NO3 (2) and
[Co2(H2L)(8-HQ)2](NO3)2 (3) were found to be in the range 3.67–
4.32 B.M. These values are consistent with the presence of three
unpaired electrons per the Co(II) ion in tetrahedral geometry
[47]. The electronic spectra of the obtained Co(II) complexes in
DMF solution exhibit one band at 528, 534 and 524 nm, respec-
tively, the bands exhibit some shifts to lower wavelength than
the expected value for tetrahedral complexes (600–700 nm) [47]
which may be due to the formation of six coordinate species in
DMF which is a coordinating solvent and the d–d transition bands
shifted near 500 nm which the expected value for Co(II) ion in
octahedral complexes [47].
For Ni(II) complexes, binuclear complexes [Ni2(HL)2](NO3)2ꢂH2-
OꢂEtOH (4) and [Ni2(H2L)(8-HQ)2](NO3)2 (6) and a trinuclear com-
plex [Ni3(L)(HL)(NO3)3 EtOH] (5) were obtained. The effective
magnetic moment values of Ni(II) complexes were in the range
2.51–2.83 B.M. These values indicate the presence of two unpaired
electrons per Ni(II) ion and confirming tetrahedral geometry
around Ni(II) ion [48–50]. The results indicate some spin–spin cou-
pling due to antiferromagnetic interaction [48]. The electronic
spectra of all Ni(II) complexes (4, 5 and 6) in DMF solution showed
one band at 537, 539 and 545 nm, respectively, the shift of bands
to lower wavelength may be explained by the coordination of
DMF solvent with Ni(II) ions in the complexes and formation of
octahedral structures.
plexes 1, 2, 3, 4, 5, 6, 7, 9 and 12, the t(C@O) band of the coordi-
nated ligand is doubled, one band being nearly coincident with
the corresponding one of free ligand at 1692 cmꢁ1 and the other
occurring at a lower frequency by 60–75 cmꢁ1. This result has been
interpreted in terms of the presence of both coordinated and non-
coordinated (C@O) group in the same ligand molecules [28]. One of
the t(NH) bands of the coordinated ligand being nearly coincident
with corresponding one of free ligand and the other shows slightly
shift to a lower or a higher frequency and the intensity of this band
has decreased suggesting coordination of the ligand with deproto-
nation of the amidic hydrogens. For complexes 8, 10, 11, 13 and 14,
t(C@O) band of the coordinated ligand being nearly coincident
with the corresponding one of the free ligand confirming that
C@O group is not involved in complex formation and the intensity
of one NH (amidic) bands of the coordinated ligand has decreased
showing coordination of the ligand with deprotonation of the ami-
dic hydrogens. The nitrate vibrations in complexes 5, 10 and 11 at
1411–1390, 1321–1310 and 1224–1220 cmꢁ1 are indicative of the
presence of monodentate nitrato groups [29,30] since the separa-
tion of the two highest frequency bands (under C2V symmetry) is
small (<160 cmꢁ1). Complex 8 shows four bands at 1410, 1322,
1221 and 1053 cmꢁ1 assigned to the bidentate chelating nitrato
groups [31]. The presence of ionic NOꢁ3 ions in complexes 1, 2, 3,
4, 6, 7 and 12 confirming by the appearance of the stretching vibra-
tion mode of ionic nitrate at 1412–1383 cmꢁ1 [32]. Complex 13
showed strong absorption band at 976 cmꢁ1, which is assigned to
the
t(V@O) vibration [33]. Also, the characteristic band of the anti-
symmetric
t
3(O@U@O) is observed in the IR spectrum of the ura-
nyl complex (14) at 943 cmꢁ1 [34] indicating that the uranyl ion
is linear. Appearance of the new bands at 522–513 and 457–
411 cmꢁ1 which could be assigned to
respectively [35,36].
t(MAO) and t(MAN),
The IR spectrum of the free 8-hydroxyquinoline (8-HQ) shows a
strong band at 1586 cmꢁ1 due to the stretching vibration of the
C@N group [37]. This band is shifted to a higher wavenumber on
coordination for complexes 3, 6, 9 and 12 suggesting that the lone
pair on nitrogen is involved in the formation of a bond with the
metal ion. Moreover, the broad stretching vibration at 3242 cmꢁ1
due to OAH group of the free 8-HQ ligand [38] was found to be ab-
sent in the latter complexes, suggesting the formation of an MAO
bond with 8-hydroxyquinolinate. Thus, 8-hydroxyquinolinate in
all mixed ligand complexes 3, 6, 9 and 12 is a bidentate chelating
ligand.
Electronic spectra and magnetic moment measurements
The electronic absorption spectra measured in DMF solvent and
the effective magnetic moments of the prepared metal complexes
were determined. The data obtained are recorded in Table 3. The
bands at 238, 285 and 376 nm of the free ligand show small shifts
as a result of complex formation [39–41]. The band at 416–385 nm
in the spectra of the complexes may be due to intramolecular
LMCT [42]. Three different types of Cu(II) complexes were ob-
tained, a binuclear complex [Cu2(HL)2](NO3)2 (7), a trinuclear com-
plex [Cu3(L)2(NO3)2] (8) and a mixed ligand complex [Cu2(HL)2(8-
HQ)2] (9). The electronic spectra of Cu(II) complexes (7 and 8)
showed one band at 523 and 524 nm, respectively, corresponding
to the 2B1g ? 2Eg transition in square-planar geometry [43]. In
addition, the magnetic moments of the complexes (7 and 8) were
1.81 and 1.64 B.M., respectively, which are consistent with the pro-
posed square-planar structure [44] of the complexes. However, the
Fig. 3. X-band ESR spectra of Cu2+ complexes (7, 8, 9) and VO2+ complex (13).

M.A. El-ghamry et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 110 (2013) 205–216
211
Fig. 4. Mass spectra of the [Fe(HL)2(NO3)(H2O)] (10), [Co2(HL)2](NO3)2 (1) and [Co2(H2L)(8-HQ)2](NO3)2 (3) complexes.
Three Fe(III) complexes were obtained which have different for-
mulae, mononuclear complexes [Fe(HL)2(NO3)(H2O)] (10), [Fe
(H2L)(HL)(8-HQ)]NO3 (12) and a binuclear complex [Fe2(HL)2(-
L)(NO3)2(EtOH)2] (11). The electronic spectra of the Fe(III) com-
plexes showed one absorption band at 536–545 nm
corresponding to 6A1 ? 4T2 electronic transition [51], suggesting
an octahedral geometry around Fe(III) ion. The values of the mag-
netic moments of the mononuclear Fe(III) complexes (10 and 12)
were 2.80 and 2.43 B.M., respectively, these values are too near
from its being in a low spin (t2g5 eg0) where the magnetic moment
lies in the range 2.1–2.5 B.M. [52], which may be due to the effect
of the strong fields of the ligand, H2L and the additional ligand, 8-
HQ. This would lead to spin-pairing of the electrons and/or antifer-
romagnetic interactions between Fe(III) ions in neighboring mole-
cules. The magnetic moment of the binuclear complex (11) is 3.97
B.M., lower than expected value (which is around 5.92 B.M.), per-
haps due to antiferromagnetic interactions between Fe(III) ions in
the complex.
characteristic for the proposed structure [54]. The magnetic mo-
ment value of the VO2+ complex is 2.24 B.M. which is higher than
the expected for d1-system, suggesting an orbital contribution [55].
The electronic spectrum of the mononuclear UOþ2 2 complex
[UO2(HL)2] showed one absorption band at 509 nm, which is
attributed to an electronic transition from the apical oxygens to
f-orbitals of the uranium (VI) ion or due to charge transfer transi-
tion from the ligand to uranium (VI) ion [56].
ESR spectra of Cu2+ and VO2+ complexes
ESR spectra of the Cu(II) complexes (7, 8 and 9) and the V(IV) O
complex (13) were recorded in the solid state at room temperature
as shown in Fig. 3. The X-band ESR spectra of the Cu(II) complexes
(7 and 8) exhibit a single broad line with g = 2.077 and 2.078,
respectively. The g-values together with the shape of the ESR sig-
nals indicate the square-planar geometry around Cu(II) ions in
these complexes [57,58]. The spectrum of the Cu(II) complex (9)
exhibits two signals at g\ = 2.068 and g|| = 2.155, gav = 1/3
(g|| + 2g\) = 2.097. The shape of the ESR signals is consistent with
the octahedral geometry around the Cu(II) ions in this complex
[57,58]. From the observed g-values, it is clear that g|| > g\ which
indicates that the unpaired electron is predominantly in the dx2-
The electronic spectrum of the mononuclear VO2+ complex,
[VO(HL)2] showed a d–d transition band at 568 nm which can be
assigned to the 2B2 ? 2E ( 1) or 2B2 ? 2B1
t (t2) transition and indi-
cates that the geometry around VO2+ ion is square-pyramidal [53].
The band at 976 cmꢁ1 in the IR spectrum of the vanadyl complex is
2
y2 orbital [59–61] giving B1g as the ground state. The g value is

212
M.A. El-ghamry et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 110 (2013) 205–216
Table 4
Results of thermogravimetric analysis (TGA) of some complexes.
Complex
(2)
Molecular formula of the complex (M. Wt.)
Temperature range (°C)
Wt loss% found (calcd.)
Decomposed product lost
NO2 + C27H19N7O
[Co2(HL)3]NO3
(1220.8)
101–291
292–351
352–424
41.64(41.20)
24.12(23.75)
22.98(22.77)
11.12(12.27)
5.41(4.60)
80.86(80.45)
13.98(14.95)
4.48(4.18)
46.44(46.77)
25.02(24.70)
23.98(24.35)
43.33(42.54)
41.68(42.33)
15.00(15.13)
35.91(35.47)
40.77(40.83)
23.32(23.70)
53.62(53.75)
35.29(35.35)
11.10(10.90)
C17H12N3O2
C10H14N8O2
Residue, 2CoO
Lattice EtOH
Lattice H2O + 2NO2 + C36H30N12O4
Residue, 2NiO
(4)
(5)
[Ni2(HL)2](NO3)2ꢂH2OꢂEtOH
29–157
158–467
(999.4)
[Ni3(L)(HL)(NO3)3(EtOH)]
(1101.1)
38–174
175–347
348–453
Coordinated EtOH
3NO2 + C22H13N6O
C13H16N6O
Residue, 2NiOꢂNiCO3
2NO2 + C20H14N4
C16H16N8O5
Residue, Cu2O
2NO2 + O2 + C15H11N3
C21H17N9O
Residue, 3CuO
C22H15N7O2
C14H15N5O
(7)
[Cu2(HL)2](NO3)2
(945.0)
173–298
299–549
(8)
[Cu3(L)2(NO3)2]
(1006.5)
39–293
294–435
(13)
[VO(HL)2]
(760.9)
186–312
313–505
Residue, VO2
an important function for indicating covalent character of MAL
bonds [62], for ionic character, g|| < 2.0023 and for covalent charac-
ter g|| > 2.0023. In the present complex (9), the g is more than
2.0023 indicating appreciable covalent character for the CuAL
bond [63]. In addition, exchange coupling interaction between
the two copper centers is explained by the Hathaway expression
[G = (g|| ꢁ 2.0023/(g\ – 2.0023)], if G is greater than 4, the exchange
interaction in the solid state is negligible, whereas when it is less
than 4, a considerable exchange interaction is observed in the solid
complex. The calculated G-value of Cu(II) complex (9) is 2.324, sug-
gests some interaction between the Cu(II) centers.
The ESR spectrum of the [VO(HL)2] complex (13) showed a
sharp band with resolved hyperfine structure. The vanadium
hyperfine coupling with the nearby 51V (I = 7/2) nucleus showed
8-lines indicating that the VO2+-complex is mononuclear. The g-
values of VO2+-complex were g = 2.061 and g = 2.112. These values
agree with the g-tensor parameters reported for vanadium com-
plexes with square-pyramidal geometry [64,65].
[Ni3(C36H29N12O4)(NO3)3(EtOH)]
complex (5)
M. Wt. = 1101.1
-EtOH
o
38-174 C
4.48 % (4.18 %) found %(calcd %)
[Ni3(C36H29N12O4)(NO3)3]
-(3NO2 + C22H13N6O)
46.44 % (46.77 %)
o
175-347 C
[Ni3(C14H16N6O6)]
-C13H16N6O
25.02 % (24.70 %)
o
348-453 C
Mass spectra of the metal complexes
2NiO.NiCO3
The mass spectra for most of the complexes were performed to
confirm the molecular formulae. The molecular ion peaks are coin-
cident with the formula weights of the complexes (see Table 1).
This supports the identity of the structure. The mass spectra of
the complexes [Co2(HL)2](NO3)2, [Co2(H2L)(8-HQ)2](NO3)2 and
[Fe(HL)2(NO3)(H2O)], Fig. 4, are taken as representative examples.
The molecular ion peaks were observed at m/e 935.5, 877 and
830, respectively, which confirming the formula weights of these
complexes.
23.98 % (24.35 %)
Scheme 3. Proposed thermal decomposition pattern of [Ni3(L)(HL)(NO3)3(EtOH)].
4.48%) is the first step. The second step shows removal of the coordi-
nated nitrate groups in a form of NO2 and a fragment part
(C22H13N6O) of the ligand (calcd. 46.77%, found 46.44%). In the last
step, the complex undergoes decomposition of another part of the li-
gand (C13H16N6O) within the temperature range up to 453 °C, after
which a constant weight was observed and 2NiO. NiCO3 (calcd.
24.35%, found 23.98%) was the final residue.
Thermal studies
Thermogravimetric analysis (TGA) was used as a probe to proof
the associated water or solvent molecules to be in the coordination
sphere of the complexes or in the crystalline form, supports the
elemental analysis. The results of TGA of some complexes (2, 4,
5, 7, 8 and 13) were recorded in Table 4. The following detailed
description of the TG thermograms of the complexes (5, 8 and
13) is given as examples and the other TG thermograms were ob-
tained similarly.
TGA of [Cu3(L)2(NO3)2] complex (8). The TG thermogram of the
[Cu3(L)2(NO3)2] complex (8) involves two decomposition steps in
the ranges 39–293 and 294–435 °C, Scheme 4. The first step shows
removal of the coordinated nitrate groups in a form of NO2 and O2
in addition of a fragment part (C15H11N3) of the ligand (calcd.
35.47%, found 35.91%). In the second step, the complex undergoes
decomposition of another part of the ligand (C21H17N9O) within
the temperature range up to 435 °C leading to the formation of
3CuO (calcd. 23.70%, found 23.23%) as the final residue.
TGA of [Ni3(L)(HL)(NO3)3(EtOH)] complex (5). The TG thermogram of
[Ni3(L)(HL)(NO3)3(EtOH)]complex(5) involvesthree decomposition
steps in the ranges 38–174, 175–347 and 348–453 °C, Scheme 3.
Elimination of coordinated C2H5OH molecule (calcd. 4.18%, found
TGA of [VO(HL)2] complex (13). The thermal decomposition process
of [VO(HL)2] complex (13) started at 186 °C and finished at 505 °C

M.A. El-ghamry et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 110 (2013) 205–216
213
The thermodynamic and kinetic parameters for the different
thermal decomposition steps in the complexes (2, 4, 5, 7, 8 and
13) were evaluated graphically by employing the Coats–Redfern
equation [66]. The results of the order (n), the activation energy
[Cu3(C36H28N12O4)(NO3)2]
comples (8)
M. Wt. = 1006.5
-(2NO2 + O2 + C15H11N3)
35.91 %(35.47 %) found %(calcd %)
(Eꢃ), the activation enthalpy (
D
Hꢃ = Eꢃ ꢁ RT), the activation entropy
o
39-293 C
(
D
D
Sꢃ = R [ln(Ah/KT) ꢁ 1]) and the free energy of activation (
D
Gꢃ = -
Hꢃ-T Sꢃ) of the decomposition steps for the chosen complexes
D
are listed in Table 5, where A is a pre-exponential factor, K is Boltz-
mann’s constant and h is Plank’s constant, respectively. The
D
Sꢃ
[Cu3(C21H17N9O4)]
values were found to be negative which indicated that the acti-
vated complex is more ordered than the reactant and/or the ther-
mal decomposition reaction is slower than normal [67]. The
-C21H17N9O
o
294-435 C
positive sign of
non-spontaneous processes.
D
Gꢃ revealed that the decomposition steps are
40.77 % (40.79 %)
D
Gꢃ values increase with increasing
the order of the decomposition stages which indicates that at high
temperatures the ligand decomposes and requires more energy for
its rearrangement in the activated state [68] this may be attributed
to the structural rigidity of the remaining complex after the expul-
sion of one and more ligands, as compared with the precedent
complex, which required more energy for its rearrangement before
3CuO
23.32 %(23.70 %)
Scheme 4. Proposed thermal decomposition pattern of [Cu3(L)2(NO3)2].
undergoing any compositional change. The positive values of
means that the decomposition processes are endothermic.
D
Hꢃ
[VO(C36H30N12O4)]
complex (13)
M. Wt. = 760.9
3D Molecular modeling study
The molecular modeling of a representative complex, [Co2(H2-
L)(8-HQ)2] (NO3)2 (3) is shown in Fig. 5. The C@O bonds
(C9AO10 and C21AO22) are longer by 0.05 Å which indicate that
the coordination take place through carbonyl groups with two O,
N-donor of the ligand, H2L and two O, N-donor of the mixed ligand,
8-HQ at the equatorial positions in trans-arrangement to each
other, is based on its square planar structure.
Based on the above results gained from elemental and thermal
analyses, IR, electronic, mass and ESR spectra as well as conduc-
tance and magnetic moments studies, the geometrical structures
of the complexes can be formulated as follows:
186-312 oC
-C22H15N7O2
53.62 %(53.75 %)
found %(calcd %)
[VO(C14H15N5O2)]
313-505 oC
-C14H15N5O
35.29 %(35.35 %)
H
O
N
H
N
H
N
N
N
VO2
N
O
Y
X
M
11.10 %(10.90 %)
H
N
H
N
N
N
Scheme 5. Proposed thermal decomposition pattern of [VO(HL)2].
N
H
O
N
O
M
X
Y
and involves the removal of a fragment part (C22H15N7O2) of the li-
gand (calcd. 53.75%, found 53.62%) in the 186–312 °C temperature
range. In the second stage, the complex undergoes decomposition
of another part of the ligand (C14H15N5O) within the temperature
range up to 505 °C, leading to the formation of VO2 (calcd.
10.90%, found 11.10%) as the final residue, Scheme 5.
-
(10) Fe (III)
(13) VO (II)
(14) UO2 (II)
NO3
H2O
The proposed structures of the mononuclear complexes (10),
(13) and (14).
Table 5
The order (n), temperature of decomposition and activation parameters (Eꢃ,
D
Hꢃ,
D
Sꢃ,
D
Gꢃ) for decomposition steps of some of the complexes.
No.
(2)
Complex
Step
Order (n)
T (°k)
Eꢃ (KJ molꢁ1
)
D
Hꢃ (KJ molꢁ1
)
D
Sꢃ (JK molꢁ1
)
D )
Gꢃ (KJ molꢁ1
[Co2(HL)3]NO3
1st
0.66
0.66
0.66
0.66
0.66
0
0.66
0.66
0.66
0.66
0.66
0.66
0.66
0.66
389
537
636
413
603
326
412
605
531
677
531
588
551
660
13.57
15.93
14.49
6.47
18.9
6.78
10.34
11.47
9.20
3.04
13.89
4.07
12.27
8.77
12.53
9.011
14.69
9.71
ꢁ173.4
ꢁ181.6
ꢁ181.1
ꢁ166.3
ꢁ182.5
ꢁ167.8
ꢁ176.3
ꢁ180.4
ꢁ183.4
ꢁ181.7
ꢁ180.8
ꢁ180.2
ꢁ187.1
ꢁ182.6
77.79
108.99
124.38
71.72
123.94
58.77
2nd
3rd
1st
2nd
1st
2nd
3rd
1st
2nd
1st
(4)
(5)
[Ni2(HL)2](NO3)2ꢂH2OꢂEtOH
[Ni3(L)(HL)(NO3)3(EtOH)]
15.7
84.91
117.9
13.80
16.94
14.64
19.10
14.60
14.17
14.53
(7)
[Cu2(HL)2](NO3)2
[Cu3(L)2(NO3)2]
[VO(HL)2]
109.92
132.02
110.69
115.67
112.68
129.56
(8)
2nd
1st
2nd
(13)
9.59
9.04

214
M.A. El-ghamry et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 110 (2013) 205–216
H
N
H
N
NH
NH
O
NH
O
O
N
N
O
O
N
O
N
N
N
N
N
N
N
H
N
Cu
O
Cu
M
(NO3)2. Y. Z
M
O
N
O
N
O
N
O
N
N
N
H
O
Cu
NH
NH
NH
O
N
M
Y
Z
O
(1) Co (II)
(4) Ni (II)
(7) Cu (II)
H2O EtOH
The proposed structure of the trinuclear Cu(II) complex (8).
The proposed structures of the binuclear complexes (1), (4) and (7).
H
N
H
N
H
N
H
N
H
N
H
N
N
O
O
N
O
O
N
HN
N
N
N
N
M
M
NO3
2
Co
O
O
H
N
H
N
N
N
NO3
N
H
O
N
O
Co
M
H
N
H
N
N
N
(3)
(6)
Co (II)
Ni (II)
N
H
O
N
O
The proposed structure of the binuclear Co(II) complex (2).
The proposed structures of the mixed ligand complexes (3) and
(6).
H
N
H
N
H
N
O
H
N
H
N
O
O
N
O
N
N
N
HN
N
N
O
NO3
EtOH
Fe
N
N
Cu
Cu
NH
N
N
N
O
O
N
N
H
O
N
N
O
N
NO3
EtOH
Fe
H
N
H
N
N
H
N
N
O
N
H
N
H
N
H
O
N
O
The proposed structure of the binuclear Fe(III) complex (11).
The proposed structure of the mixed ligand complex (9)
H
N
H
N
H
N
H
N
H
N
H
N
O
O
N
O
O
N
N
N
N
N
N
N
N
NO3
Fe
Ni
Ni
O
H
N
H
N
O3N
OEt
H
H
N
H
N
N
N
N
H
O
O
N
N
O
N
O
H
Ni
O3N
NO3
The proposed structure of the trinuclear Ni(II) complex (5).
The proposed structure of the mixed ligand complex (12).

M.A. El-ghamry et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 110 (2013) 205–216
215
Fig. 5. 3D molecular modeling structure of complex (3).
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Conclusion
New bis (pyridylurea) ligand and its Co2+, Ni2+, Cu2+, Fe3+, VO2+
and UO22þ complexes were prepared and characterized by different
spectroscopic techniques. There are variety in the geometrical
structures of the prepared metal complexes: square planar, tetra-
hedral, octahedral and square pyramidal arrangements. The ther-
mal decomposition as well as the thermodynamic and kinetic
parameters were studied. 3D molecular modeling of the ligand
and a representative Co(II) complex indicate that the coordination
take place through carbonyl groups with two O, N-donor of the li-
gand, H2L and two O, N-donor of the mixed ligand, 8-HQ at the
equatorial positions in trans-arrangement to each other, is based
on its square planar structure.
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Appendix A. Supplementary material
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Supplementary data associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.saa.2013.03.016.
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