Spectral, coordination and thermal properties of 5-arylidene thiobarbituric acids

Article abstract of DOI:10.1016/j.saa.2013.01.022

Synthesis of 5-arylidine thiobarbituric acids containing different functional groups with variable electronic characters were described and their Co²⁺, Ni²⁺ and Cu²⁺ complexes. The stereochemistry and mode of bonding of 5-

Full text of DOI:10.1016/j.saa.2013.01.022

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 107 (2013) 179–187
Contents lists available at SciVerse ScienceDirect
Spectrochimica Acta Part A: Molecular and
Biomolecular Spectroscopy
journal homepage: www.elsevier.com/locate/saa
Spectral, coordination and thermal properties of 5-arylidene thiobarbituric acids
b
Mamdouh S. Masoud a, Adel El-Marghany b, Adel Orabi c, Alaa E. Ali d, , Reham Sayed
⇑
a Chemistry Department, Faculty of Science, Alexandria University, Egypt
b Chemistry Department, Faculty of Education, Suez Canal University, Egypt
c Chemistry Department, Faculty of Science, Suez Canal University, Egypt
d Chemistry Department, Faculty of Science, Damanhour University, Egypt
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
"
"
"
"
5-Arylidine thiobarbituric acids and
their complexes were synthesized.
The stereochemistry and mode of
bonding were investigated.
The ligands were of bidentate and
tridentate nature.
The complexes were of octahedral
configuration with certain thermal
stability.
H
C
O
H
S
N
X
O
N
H
5-Arylidene Thiobarbituric Acids
X = H, p-OCH3, p-NO2, p-Br, p-OH, m-CH3,
m-NO m-OH and o-OH
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 2 October 2012
Received in revised form 21 December 2012
Accepted 10 January 2013
Available online 23 January 2013
Synthesis of 5-arylidine thiobarbituric acids containing different functional groups with variable elec-
tronic characters were described and their Co2+, Ni2+ and Cu2+ complexes. The stereochemistry and mode
of bonding of 5-(substituted benzylidine)-2-TBA complexes were achieved based on elemental analysis,
spectral (UV–VIS, IR, 1H NMR, MS), magnetic susceptibility and conductivity measurements. The ligands
were of bidentate and tridentate bonding through S, N and O of pyrimidine nucleolus. All complexes were
of octahedral configuration. The thermal data of the complexes pointed to their stability. The mechanism
of the thermal decomposition is discussed. The thermodynamic parameters of the dissociation steps were
evaluated and discussed.
Keywords:
5-Arylidine thiobarbituric acids
Complexes
Ó 2013 Elsevier B.V. All rights reserved.
NMR
Thermal analysis
Introduction
barbiturate compounds using different instruments of investiga-
tions [4–30].
Pyrimidines are one of the most important compounds due to
their biological activity and are involved in the structure of nucleic
acid in living systems. The nucleic acid is related to antimetabolites
used in anticarcinogeic chemotherapy. Barbiturates and thiobarbi-
turates are used as hypnotic drugs and produce depressive effect
on central nervous system [1,2]. Most of the pyrimidines are with
antimicrobial, anti-inflammatory, and anti-tumor activities prop-
erties [2]. Serum lipid peroxidation was measured by thiobarbitu-
ric acid reactive material method during physical exercise of
different duration [3]. In our laboratory, a series of papers were ap-
peared concerning the structural chemistry of biologically active
In this paper, we prepare some substituted 5-(arylidine) thio-
barbituric acids and their complexes. The mode of invesitigation
is based on elemental analysis, magnetic moment, spectral meth-
ods (UV–VIS, IR), mass spectra, NMR and thermal analysis were re-
corded and the thermodynamic parameters were evaluated and
discussed.
Experimental
Synthesis of the ligands
5-Arylidenethiobarbituric acids were prepared by condensation
of thiobarbituric acid (0.1 mol) with the selected aromatic alde-
hydes (0.1 mol). Both were purchased from BDH Company and
were used with out further purification. The condensation was car-
⇑
Corresponding author. Tel.: +2 01115799866.
E-mail address: dralaae@yahoo.com (A.E. Ali).
1386-1425/$ - see front matter Ó 2013 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.saa.2013.01.022

180
M.S. Masoud et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 107 (2013) 179–187
H
C
O
Table 3
The bond distances for the optimized compounds using PM3 method.
H
S
N
Bond
Compound, X=
X
O
H
m-CH3
m-NO2
m-OH
o-OH
p-Br
N
H
R(1,2)
R(1,3)
R(1,9)
R(2,12)
R(3,4)
R(4,5)
R(4,6)
R(6,7)
R(7,8)
1.221
1.434
1.473
2.761
1.408
1.636
1.406
1.432
1.220
1.485
1.355
1.452
1.397
1.407
1.392
1.389
1.394
1.242
1.406
1.477
2.756
1.393
1.601
1.395
1.400
1.244
1.488
1.354
1.449
1.400
1.407
1.395
1.392
1.402
1.222
1.430
1.475
2.745
1.411
1.632
1.407
1.431
1.219
1.487
1.352
1.456
1.397
1.403
1.391
1.387
1.402
1.220
1.434
1.474
2.758
1.408
1.635
1.406
1.432
1.219
1.485
1.354
1.455
1.396
1.404
1.392
1.387
1.404
1.221
1.434
1.472
2.743
1.408
1.637
1.405
1.434
1.219
1.484
1.355
1.451
1.400
1.416
1.388
1.391
1.388
1.221
1.433
1.474
2.754
1.409
1.634
1.406
1.431
1.219
1.486
1.354
1.454
1.398
1.409
1.393
1.378
1.383
1.866
1.388
X= H, p-OCH3, p-NO2, p-Br, p-OH, m-CH3, m-
NO2, m-OH and o-OH
Fig. 1. A general skeleton of the 5-arylidine thiobarbituric acid.
ried out in EtOH. The obtained compounds were filtered off and
crystallized in 75% (v/v) EtOH, then dried in a vacuum desiccator
over (P4O10).
The elemental analysis of the compounds (C, H, N) were carried
out at the central micro-analytical laboratory, Faculty of Science,
Cairo University. A general skeleton of the prepared compounds
is given in Fig. 1.
The molecular structure of the investigated compounds was
optimized with PM3 semi-empirical method implemented in
Gaussian 03W package. The corresponding geometry was opti-
mized without any geometry constraints for full geometry optimi-
zation. Frequency calculation was executed simultaneously, and no
imaginary frequency was found, indicating minimal energy struc-
tures. The quantum chemical parameters such as the highest occu-
pied molecular orbital energy (EHOMO), the lowest unoccupied
R(7,9)
R(9,10)
R(10,11)
R(11,12)
R(11,16)
R(12,13)
R(13,14)
R(14,15)
R(14,17)
R(15,16)
R(15,17)
R(16,17)
R(17,18)
R(17,19)
1.386
1.395
1.481
1.396
1.501
1.397
1.369
1.402
1.365
1.214
1.215
(Pi), were calculated, Tables 1–3. The optimized structures for
the studied compounds are represented in Fig. 2.
molecular orbital energy (ELUMO), energy gap (
(TE), dipole moment (l), electronegativity (v), chemical potential
D
E), total energy
Table 1
The calculated quantum chemical parameters for the optimized compounds using PM3 method.
Compound, X=
Parameter
EHOMO (eV)
ELUMO (eV)
D
E (eV)
l
(D)
Hardness (eV)
Softness (eVÀ1
)
Chem. pot. (eV)
X
Total energy
H
À9.305
À9.240
À9.560
À9.314
À9.226
À9.383
À9.602
À9.245
À9.268
À1.969
À1.604
À2.347
À1.976
À1.836
À2.092
À2.503
À1.919
À1.945
7.336
7.636
7.212
7.338
7.390
7.291
7.099
7.327
7.323
5.240
4.612
2.865
5.601
6.593
4.046
2.751
6.606
5.314
3.668
3.818
3.606
3.669
3.695
3.646
3.550
3.663
3.662
0.273
0.262
0.277
0.273
0.271
0.274
0.282
0.273
0.273
À5.637
À5.422
À5.953
À5.645
À5.531
À5.738
À6.053
À5.582
À5.607
5.637
5.422
5.953
5.645
5.531
5.738
6.053
5.582
5.607
À0.106
À0.336
À0.414
À2.037
À2.024
0.259
À0.380
À1.788
À2.108
m-CH3
m-NO2
m-OH
o-OH
p-Br
p-NO2
p-OCH3
p-OH
Table 2
The calculated Mulliken atomic charge densities for the optimized compounds using PM3 method.
Atom
Compound, X=
H
m-CH3
m-NO2
m-OH
o-OH
0.316
p-Br
p-NO2
p-OCH3
p-OH
1 C
2 O
3 N
0.314
À0.336
0.049
0.354
À0.316
À0.336
0.140
À0.177
À0.331
0.344
0.310
À0.341
0.051
À0.110
À0.211
0.059
0.313
À0.333
0.048
À0.105
À0.232
0.056
0.312
À0.335
0.050
À0.106
À0.227
0.057
0.306
À0.332
0.051
À0.110
À0.207
0.058
0.317
À0.341
0.049
À0.105
À0.240
0.058
0.318
À0.345
0.050
À0.105
À0.239
0.059
À0.339
0.049
4 C
5 S
6 N
À0.105
À0.234
0.057
À0.103
À0.241
0.056
7 C
0.288
0.283
0.287
0.291
0.286
0.281
0.290
0.290
8 O
9 C
À0.331
À0.277
0.146
À0.128
À0.074
À0.110
À0.059
À0.119
À0.060
À0.326
À0.237
0.084
À0.321
À0.257
0.127
À0.138
À0.027
À0.126
0.020
À0.328
À0.271
0.140
À0.087
À0.119
À0.066
À0.155
0.085
À0.328
À0.288
0.163
À0.165
À0.045
À0.149
À0.018
À0.217
0.146
À0.328
À0.269
0.137
À0.119
À0.072
À0.088
À0.084
À0.098
À0.056
0.018
À0.321
À0.243
0.111
À0.059
À0.109
À0.009
À0.381
À0.025
À0.091
1.302
À0.336
À0.289
0.157
À0.170
À0.038
À0.154
0.133
À0.209
À0.012
À0.182
0.044
À0.335
À0.291
0.159
À0.174
À0.026
À0.212
0.147
À0.164
À0.017
À0.217
10 C
11 C
12 C
13 C
14 C
15 C
16 C
17 C,NÁO and Br
18 O
19 O
À0.106
À0.062
À0.135
À0.098
À0.078
À0.096
À0.181
À0.422
0.026
À0.110
1.308
À0.224
À0.228
À0.592
À0.593
À0.597
À0.590
0.133

M.S. Masoud et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 107 (2013) 179–187
181
H
m-CH3
m-NO2
m-OH
o-OH
p-Br
p-NO2
p-OCH3
p-OH
Fig. 2. The optimized structure for the compounds.
Table 4
Analytical data for the ligands.
Compound
Color
Formula
Melting point (°C) % Calculated/(found)
C
H
N
S
5-Benzylidine thiobarbituric acid
5-Salicylidine thiobarbituric acid
5-(3-Hydroxybenzylidine) thiobarbituric acid Orange
5-(3-Anisalidine) thiobarbituric acid
5-(3-Nitrobenzylidine) thiobarbituric acid
5-(4-Hydroxybenzylidine) thiobarbituric acid Orange
5-(4-Anisalidine) thiobarbituric acid
5-(4-Nitrobenzylidine) thiobarbituric acid
5-(4-Bromobenzylidine) thiobarbituric acid
Yellow
Pale yellow
C
C
C
C
C
C
C
C
C
11H8N2O2S
11H8N2O3S
11H8N2O3S
12H10N2O3S
11H7N3O4S
11H8N2O3S
12H10N2O3S
11H7N3O4S
250
300
264
238
260
>360
298
217
56.88 (56.60) 3.45 (3.60) 12.06 (12.10) 13.80 (13.75)
53.22 (53.10) 3.25 (3.20) 11.28 (11.00) 12.91 (12.90)
53.22 (53.50) 3.25 (3.35) 11.28 (11.10) 12.89 (12.91)
54.65 (55.10) 3.84 (3.50) 10.68 (10.50) 12.22 (12.21)
47.65 (47.90) 2.54 (2.30) 15.15 (15.10) 11.56 (11.54)
53.22 (52.90) 3.25 (3.10) 11.28 (11.40) 12.91 (12.85)
54.65 (54.30) 3.84 (3.70) 10.68 (10.30) 12.22 (12.19)
47.65 (47.40) 2.54 (2.40) 15.15 (15.15) 11.56 (11.52)
Yellow
Yellow
Orange
Yellowish white
Canary yellow
11H7N2O2SBr >360
42.46 (42.30) 2.27 (2.30) 9.00 (9.00)
10.30 (10.26)
Synthesis of complexes
Table 5 collects the analytical data for the prepared complexes,
where the metal contents were determined by the usual complex-
metric titration methods [31], after decomposition with H2O2 and
HNO3.
0.01 mol of each of cobalt(II), nickel(II), and copper(II) as chlo-
ride, were dissolved in mixed solvents of methanol and ammonical
solution. These were mixed with methanolic solution of 0.02 mol
of 5-arylidenethio-barbituric acid. The reaction mixture was re-
fluxed for 1hr and left over night where the complexes were pre-
cipitated and separated by filtration and washed by methanol
and dried in a vacuum desiccator over anhydrous CaCl2. The for-
mula, color and melting point of the ligands are given in Table 4.
Instruments and working procedures
Electronic absorption spectra
The spectrophotometric measurements of the ligands in the vis-
ible and ultraviolet regions in the wavelength range 190–600 nm

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M.S. Masoud et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 107 (2013) 179–187
Table 5
Analytical data for Co(II), Ni(II) and Cu(II) 5-(o, m and p hydroxybenzylidine)2-TBA complexes.
Complexes
Color
Formula
Conductance1
leff 298 K
m.p (°C)
%Calculated/(found)
N
M
S
Co-I
Ni-I
Cu-I
Co-II
Ni-II
Cu-II
Co-III
Ni-III
Cu-III
Pale brown
Pale brown
Gray
Pale brown
Pale burble
Pale gray
Purple
Co (C22H14N4O6S2)Á5H2O
11
7
41
9
11
5
11
4
5.32
3.10
2.10
5.11
3.07
2.07
5.28
3.01
2.13
333
338
285
>360
>360
>360
300
8.71 (8.74)
8.64 (8.70)
8.41 (8.50)
8.52 (8.58)
9.62 (9.50)
8.46 (8.50)
9.02 (9.10)
8.96 (9.11)
8.46 (8.50)
9.16 (8.217)
8.69 (7.46)
9.53 (9.39)
8.97 (9.30)
6.72 (7.45)
9.60 (9.26)
9.49 (9.40)
9.39 (7.21)
9.60 (9.39)
9.96 (9.58)
9.49 (9.47)
9.62 (9.59)
9.99 (9.93)
11.01 (11.00)
9.74 (9.69)
10.32 (10.28)
10.26 (10.22)
9.68 (9.43)
Ni (C22H14N4O6S2)Á5H–OÁCH3OH
Cu (C22H15N4O6S2)Á4H2OÁCl
Co (C22H14N4O6S2)Á4H2OÁCH3OH
Ni (C33H22N6O9S3)Á4H2O
Cu (C22H14N4O6S2)Á4H2OÁCH3OH
Co (C22H14N4O6S2)Á2H2OÁCH3OH
Ni (C22H14N4O6S2)Á4H2O
Purple
Dark violet
300
270
Cu (C22H14N4O6S2)Á4H2OÁCH3OH
9
1
Conductance of 10–3 M in DMSO (l
mho cm2 molÀ1).
Table 6
Assignment of electronic spectrum of Co(II), Ni(II) and Cu(II) complexes.a
Complexes
Bands (cmÀ1
)
Assignments
Co(II)-5-(salicylidine)-2-TBA
Ni(II)-5-(salicylidine)-2-TBA
18,000
15,455
1836
4T1g (F) ? 4T1g (P)
3A2g
3A2g
2T2g
4T1g
4T1g
3A2g
2T2g
4T1g
4T1g
3A2g
2T2g
?
?
?
?
?
?
?
?
?
?
?
3T1g (F)
3
T1g (P)
Cu(II)-5-(salicylidine)-2-TBA
Co(II)-5-(m-hydroxybenzylidine)-2-TBA 27,530
17,142
2Eg
4A2g (F)
4T1g (P)
3T1g (P)
2Eg
15,384
19,565
Ni(II)-5-(m-hydroxybenzylidine)-2-TBA
Cu(II)-5-(m-hydroxybenzylidine)-2-TBA 18,711
Co(II)-5-(p-hydroxybenzylidine)-2-TBA
Ni(II)-5-(p-hydroxybenzylidine)-2-TBA
15,544
18,405
17,006
4A2g (F)
4T1g (P)
3T1g (P)
2Eg
Cu(II)-5-(m-hydroxybenzylidine)-2-TBA 18,367
a
The geometries of all complexes are of octahedral configuration.
were made with computerized UV–visible spectrophotometer
(Shimadzu Corporation 1601 (PC).
Infrared spectra
Infrared spectra of the ligands and their complexes were re-
corded using Perkin–Elmer spectrophotometer model 1430 cover-
O
NH
S
CH
ing the frequency range 200–4000 cmÀ1
.
N
O
X
nH
Y
O.
2
M
Thermal analysis
2
Differential thermal analysis (DTA) and thermogravimetric
measurements (TGA) were performed on a DII Pont 9900 comput-
erized thermal analyzer at the Physics Department, Faculty of Sci-
ence, El-Moenofia University. The heating rate used was 10°/min.
60 mg of the sample was placed in a platinum crucible. Dry nitro-
gen was flowed over the sample at a rate 10 cc/min and a chamber
cooling water flow rate was 101/h. The speed was 5 mm/min.
Where
X
M
n
Y
o-OH
m-OH
p-OH
p-OH
o-OH
o-OH
Co
Co
Co
Ni
Ni
Cu
5
4
2
4
5
4
0
CH3OH
CH3OH
0
CH3OH
Cl
Mass spectra
O
N
Mass spectra of the ligands were obtained using a mass spectro-
photometer (EI) Q1MS LMR UP LR at the National Research Center,
Cairo.
NH
S
CH
O
X
Y
nH O
2
.
1H NMR
M
/2
1H NMR was recorded out in Ottawa-Carleton Chemistry Insti-
tute, Carleton University, Canada.
H2O
Where
X
M
n
Y
Magnetic susceptibility measurements
o-OH
p-OH
Cu
Cu
2
2
CH3OH
CH3OH
Hg[Co(SCN)4] complex was used for calibrating the Gouy tubes.
Some of the complexes were measured using the Faraday method.
Diamagnetic corrections were calculated from the data given by
Figgis and Lewis [32].
Fig. 3. Postulated structures of metal-5-(salicylidine)-2-thiobar-bituric acid
complexes.

M.S. Masoud et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 107 (2013) 179–187
183
Table 7
1H NMR signals of 5-(substituted benzylidine) thiobarbituric acid in DMSO-d6.
Table 8d
Mass spectra for 5-(3-anisylidine)2-thiobarbituric acid.
Compounds
d (ppm) for free
Assignments
Assignments
M.Wt.
M/e peak
ligand
SH + C@O
SH + C@O + NH
61
76
63
77.1
103
164.1
172
231
5-(Salicylidine) thiobarbituric acid
13.3
12.3
7.1
7.0, 7.25
5.0
OAH
NAH
CAH
C6AH4
Free OAH
phenolic
H-bond of OAH
SH
SH + C@O + NH + C@N
Hetero ring + CH
Hetero ring + C2H2
Ligand – OCH3 Group
Base peak of ligand
102
157
170
231
262
262.1
3.75–4.2 (br)
2.1
5-(3-Hydroxybenzylidine)
thiobarbituric acid
12.45
12.3
11.7
8.1
OAH
NAH enol
NAH keto
CAH
Table 8e
Mass spectra for 5-(3-nitrobenzylidine)2-thiobarbituric acid.
7.7, 7.4, 7, 6.5
C6AH4
5.9
2.0
OH phenolic
SH
Assignments
M.Wt.
M/e peak
C@S + NH
C@S + NH + OH
59
76
59
75
101.1
116
144.1
230
5-(4-Hydroxybenzylidine)
thiobarbituric acid
12.35
12.25
11.6
8.25
8.4, 6.9
5.85
OAH
NAH enol
NAH keto
CAH
C6AH4
OH phenolic
SH
HO + C@S + NH + C@N
Hetero ring – C@O
Hetero ring
Ligand – NO2 group
Ligand – OH group
Base peak of ligand
102
116
144
231
260
278
260.1
277.1
2.0
Table 8a
Mass spectra for 5-(benzylidine)2-thiobarbituric acid.
Table 8f
Mass spectra for 5-(4-hydroxybenzylidine)2-thiobarbituric acid.
Assignments
M.Wt.
M/e peak
C@S + NH
C@S + 2NH
59
76
59.1
76.1
102.1
116.1
144
Assignments
M.Wt.
M/e peak
SH + C@O
61
87
63
89.2
118
132.1
150
231.2
248
2NH + C@O + C@S
Hetero ring – C@O
Hetero ring
Hetero ring + C2H2 group
Base peak of ligand
102
116
144
172
232
C@O + NH + CSH
Hetero ring – C@O
Hetero ring – C
Hetero ring
Ligand – OH group
Base peak of ligand
116
132
144
231
248.27
172
232
Table 8b
Mass spectra for 5-(salicylidine)2-thiobarbituric acid.
Assignments
M.Wt.
M/e peak
C@S + NH
59
87
116
144
172
230
59
88
116
143
172.1
230
Table 8g
Mass spectra for 5-(4-anisylidine) 2-thiobarbituric acid.
2NH + NH + C@O
Hetero ring – C@O
Hetero ring
Hetero ring + C2H2 group
Ligand – H2O group
Assignments
M.Wt.
M/e peak
C@S + NH
59
87
59
89
C@S + NH + C@O
OH + C@S + NH + C@N
Hetero ring – C@O
Hetero ring
Hetero ring + C2H2
Ligand – OCH3 group
Base peak of ligand
102
116
144
170
231
262
102
117
145
172
230
262
Table 8c
Mass spectra for 5-(3-hydrozybenzylidine) 2-thiobarbituric acid.
Assignments
M.Wt.
M/e peak
C@S + NH
59
87
116
144
231
248
59
89
116.1
144
231
248
C@S + NH + C@O
Hetero ring – C@O
Hetero ring
Ligand – OH group
Base peak of ligand
Table 8h
Mass spectra for 5-(4-nitrobenzylidine)2-thiobarbituric acid.
Assignments
M.Wt.
M/e peak
C@S + NH
C@S + NH + OH
59
76
59
75
OH + C@S + NH + C@N
Hetero ring – C@O
Hetero ring
Hetero ring + C2H2
Ligand – NO2 group
Ligand – OH group
Base peak of ligand
102
116
144
170
231
260
277
101
116
149
179
230
260
277
Conductance measurements
The conductance measurements of 1 Â 10À3 M solution of the
compounds in DMSO were performed using a WTW model LF-42
Conductivity Bridge fitted with a LTA-100 conductivity cell.

184
M.S. Masoud et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 107 (2013) 179–187
t
C@S band appeared at 1444 cmÀ1 for the ligand is
Table 8i
(d) The
Mass spectra for 5-(bromobenzylidine)2-thiobarbituric acid.
unchanged or weakly shifted on complexation, with one
exception for Co(II) complex [32].
Assignments
M.Wt.
M/e peak
(e) Medium new bands in all complexes could be assigned as
C@S + NH
C@S + 2NH
59
76
59.1
75.2
101
153
172
t
MAO (522–539 cmÀ1) while the very weak one at (500–
517 cmÀ1) is assigned as
tMAN [36].
2NH + C@O + C@S
Hetero ring – C@O
Hetero ring
Hetero ring + C2H2 group
Base peak of ligand
102
144
170
231
312
231.1
312
5-(p-Hydroxybenzylidine)2-TBA complexes
Nearly similar spectral bands were recorded as the previous
complexes:
(a) Broad tH2O bands were given 3656-3-2655, 3677–2700 and
Results and discussions
3666–2678 cmÀ1 for Co(II), Ni(II) and Cu(II) complexes,
respectively.
Electrical conductivity
(b) The weak t
SAH at 2611 cmÀ1 band for the ligand gives posi-
tive shift to 2633 cmÀ1on complexation may be due to the
increasing of nucleophilisity of the sulfur atom.
The molar conductance of the synthesized complexes in DMSO,
Table 5, indicated non-electrolyte behavior except Cu-5-(salicyli-
dine)2-TBA behaves as AÀB+ electrolytes [33].
(c) The
ligand gives considerable change on complexation.
(d) The
of C@S appeared at 1444 cmÀ1 for the ligand gives
tC@N and t
C@O appeared at 1683–1522 cmÀ1 for the
t
Infrared spectra
slightly change in the formed complexes of Ni(II) and Cu(II),
meanwhile Co(II) complex remains unchanged.
It was necessary to investigate the infrared spectra of the pre-
pared metal complexes compared with those of the free ligand to
determine the mode of chelation [34]. The complexes may increase
or decrease the vibrational frequency of coordinated functional
groups depending on the strength of
tween the metal ion and -electron ‘of the functional group [16].
(e) The
t
of MAO appeared at 539 cmÀ1 as a weak appearance
for Co(II), at 537 cmÀ1 as a medium band for Ni(II) and at
522 cmÀ1as a medium band for Cu(II) complexes. The very
weak band at 500–512 cmÀ1 could be assigned as
band [36].
tMAN
p-interaction occurring be-
p
5-(Salicylidine)2-TBA complexes
Electronic spectroscopy and magnetic properties
(a) The broad bands appeared, at 3633–2722, 3633–2766 and
3633–2766 cmÀ1 for Co(II), Ni(II) and Cu(II) complexes,
respectively, may be due to the possible existence of water
molecule.
The Nujol mull electronic absorption spectrum for the Co(II),
Ni(II) and Cu(II) 5-(ortho, meta and para-hydroxybenzylidine)2-
TBA complexes are collected in Table 6. The magnetic properties
of the complexes proved the octahedral structures [37–41], Fig. 3
and Table 5.
(b) The
t of OAH and NAH groups not detected in the formed
complexes may be due to the involvement in the broad band
of H2O.
(c) The weak
t
SAH appeared at 2633 cmÀ1 for 5-(salicylidine)
Proton NMR spectroscopy and mass spectra
TBA becomes more weaker for Co(II), Ni(II), and Cu(II) com-
plexes, i.e. play some role in these complexes.
(d) The C@N and C@O groups appeared at the range 1544–
1677 cmÀ1 for the ligand undergoes considerable shift to
lower cmÀ1, which indicated their entrance in the complex-
ation process as a chelation site [35].
The signals of 1H NMR spectrum of 5-(salicylidine)2-TBA ligand
in (DMSO-d6) are given in Table 7. The SH proton appeared at
d = 2.1 ppm. The broad band at d = 3.75–4.2 ppm [42] is due to
the proton of OH group of salicylidine. The singlet band for the pro-
ton of CAH group appeared at d = 7.1 ppm, and those of the aro-
matic protons are detected at d = 7.0–7.25 ppm [43]. Singlet NAH
proton, at d = 12.3 ppm, and also the proton of the OH group of
TBA appeared at d = 13.3 ppm, are due to denote keto-enol forms
[44], (AC(O)ANHA M C(OH)@NA). The position of SAH band not
changed to indicate that S atom is not involved on complexation.
The absence of the broad band of aromatic OAH group may be
due to the breakdown of inter or intra hydrogen bond. Also the ab-
sence of the band of OAH of the TBA ring may be due to its involve-
ment on complexation. Generally, all the chemical shifts (d) of the
hydrogen in the free ligand were shifted to higher value in the
formed complex. The increasing (d) of the ligand in the complex,
pronounced the covalence nature of the complex and entrance
some of electron pair inside the metal ion orbital by some extent,
give de-shielding properties and hence increasing in chemical shift.
The NH proton has chemical shift equals 10.7 ppm on complexa-
tion, relatively lower than the suggested value, probably due to
breaking of intramolecular hydrogen bond gave decreasing in the
chemical shift with broadening.
(e) The C@S group appeared at 1456 cmÀ1 for the free ligand
subjected to positive shift to 1489 cmÀ1 for all complexes.
(f) New bands appeared at 597, 600, 600,594 and 592 cmÀ1 of
very weak appearance for all complexes, respectively, may
be due to the formation of MAO bond. Other medium new
band appeared at 533 cmÀ1, could be assigned as MAN band.
The MAS band is not detected due to the weak bond formed
and/or the hard-soft interaction behavior [36].
5-(m-Hydroxybenzylidine)2-TBA complexes
(a) Broad bands at 3656–2686, 3633–2766 and 3633–
2766 cmÀ1 for Co(II), Ni(II) and Cu(II) complexes, respec-
tively, could be due to H2O moiety.
(b) The weak t
SAH, at 2633 cmÀ1 for the ligand is not changed
in the formed complexes, and may be due to its stability in
the ligand and the complexes.
(c) The
t
of C@O and C@N appeared at 1644–1555 cmÀ1 for the
ligand gave negative shift in the formed complexes may be
due to the entrance of this group in the chelation processes.
Similar conclusions are deduced for 5-(m-hydroxybenzyli-
dine)2-TBA and 5-(p-hydroxybenzylidine)2-TBA. The signals of
mass spectra for the all ligands are collected in Tables 8a–8i).

M.S. Masoud et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 107 (2013) 179–187
185
Table 9
DTA and TGA analysis of Co(II), Ni(II) and Cu(II) complexes for 5-(salicylidine)2-thiobarbituric acid.
Complex
Type Tm (K)
D
E
n
am
D
SÃ
(kJ K1 molÀ1
D
HÃ
10À3
(sÀ1
Z
Temp.
TGA
Wt. loss %
Assignment
(kJ molÀ1
)
)
(kJ molÀ1
)
)
Found Calc
Co(L)2Á5H2O
29–183
183.8–
500
14.78
31.22
13.94 Dehydration of 5H2O elimination
30.68 of 2(HC„CNH2), CO2 and Benz.
Endo 334.97 0.046
Exo 751.02 0.210
0.37 2.05 À0.028
0.39 2.31 À0.021
À9.3950
À15.938
0.03
0.07
500–
1200
36.51
18.55
36.11 Elimination of 2(HC„CNH2), CO
and Benz. and formation of
cobalt oxide
Ni(L)2Á5H2OÁCH3OH
25.29–
301.27
18.01 Dehydration of 5H2O and
elimination of CH3OH
Endo 350.77 0.016
Endo 641.85 0.108
1.09 2.16 À0.036
1.15 2.26 À0.025
À12.905
À16.416
11.9
46.12
34.52
30.98
303.34– 21.30
443.34
443.34– 47.38
984.56
21.26 Elimination of 2(HC„CNH2) and
SO2
47.84 Elimination of 2(HC„CNH2), CO,
SO2 and 2 Benz. and formation of
nickel oxide
Endo 904.93 0.105
1.29 2.45 À0.027
1.30 2.47 À0.028
À25.324
À32.113
Exo
1111.8 0.115
Cu(L)2Á4H2OÁCl
20–206
10.97
29.16
10.77 Dehydration of 4H2O
Endo 341.58 0.0355
Endo 691.94 0.0621
1.51 2.67 À0.0282
0.39 2.30 À0.0307
À9.645
33.48
24.86
208–
409
28.73 Elimination of HCl, Benz., CH4
and SO2
À21.253
409–
508
45.70
45.80 Elimination of 4(HC„CH), 2NO,
N2 and Benz. And formation of
copper oxide
Endo 851.75 0.3630
Endo 1067.7 0.3750
3.37 3.37 À0.0140
2.18 3.08 À0.0169
À12.412
À18.080
173.28
130.38
Table 10
DTA and TGA analysis of Co(II), Ni(II) and Cu(II) complexes for 5-(m-hydroxybenzylidine)2-thiobarbituric acid.
Complex
Type Tm (K)
D
E
n
am
D
SÃ
(kJ K1 molÀ1
D
HÃ
10À3
(sÀ1
Z
Temp.
TGA
Wt. Loss %
Assignment
(kJ molÀ1
)
)
(kJ molÀ1
)
)
Found Calc
Co(L)2ÁH2OÁCH3OH
Endo 339.89 0.0743
1.64 2.78 À0.0217
1.31 2.48 À0.0175
1.59 2.74 À0.0151
À7.3888
0.0732 16.12–
93.5
15.33
15.77 Dehydration of 4H2O and
elimination of CH3OH
Exo
Exo
689.72 0.2797
745.54 0.3647
À12.109
À11.300
0.1210
93.5–
Elimination of 2(HCBCH), CO,
32.61 2NH2OH and Benz.
32.97
406.4
0.1615
406.4–
609.6
Elimination of 2(HCBCNH2),
35.04 CH4, SO2 and Benz. and
formation of cobalt oxide
35.48
10.63
Ni(L)3Á4H2O
Endo 355.00 0.0426
1.39 2.56 À0.027
À9.7300
37.004 20.45–
130.86
132.63– 8.93
291.03
22.456 292.55– 39.96
430.52
8.96
9.20
40.07
Dehydration of 4H2O
Elimination of C6H6
Elimination of 2(HCBCNH2), CO,
SO2 and 2 Benz.
Exo
692.80 0.0426
2.06 3.03 À0.031
1.30 2.46 À0.017
À21.865
À17.054
Endo 976.27 0.4030
122.31
Elimination of 2(HCBCH), CH4,
N2 and SO2 and formation of
nickel oxide
430.52– 18.26
550.58
17.71
Cu(L)2Á4H2OÁCH3OH
31.02–
87
9.16
10.27 Dehydration of 2H2O,
elimination of CH3OH
Endo 349.52 0.0317
1.14 2.25 À0.0307
À10.759
24.657
87–
232.66
5.69
5.44
Dehydration of 2H2O
Elimination of C6H6
Endo 415.83 0.1370
Endo 905.85 0.0360
1.07 2.13 À0.0204
0.75 1.35 À0.0418
À8.5234
À37.928
84.970 234.29– 20.54
356.29
6.4990
19.12
Elimination of (H3CC@CNH2),
H2S and CO.
356.29– 50.67
631.11
14.710
50.74 Elimination of 2(HC@CNH2),
CO2, SO2 and 2 Benz. and
Endo 905.85 0.0405
1.57 2.72 À0.0350
À31.776
formation of copper oxide
Thermal analysis
be assigned to the liberation of water molecule and methanol moi-
ety. However, the endothermic peaks for cobalt complexes at 29–
183 °C are with weight loss 14.78% corresponding to liberation of
5H2O. Meanwhile, the nickel complexes gave endothermic band
The DTA and TG data of 5-(salicylidine)2-TBA complexes, Ta-
ble 9, gave strong endothermic peaks started at 20 °C, which could

186
M.S. Masoud et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 107 (2013) 179–187
Table 11
DTA and TGA analysis of Co(II), Ni(II) and Cu(II) complexes for 5-(p-hydroxybenzylidine)2-thiobarbituric acid.
Complex
Type Tm (K)
D
E
n
am
D
SÃ HÃ 10À3
D
Z
Temp.
TGA
Wt. Loss %
Assignment
(kJ molÀ1
)
(kJ K1 molÀ1 (sÀ1
)
(kJ molÀ1
À7.1250
À12.411
À7.7581
)
)
Found Calc
Co(L)2Á2H2OÁCH3OH Endo 336.18 0.0791
1.61 2.76 À0.0211
1.07 2.13 À0.0177
1.47 2.64 À0.0103
0.0781 19.35–
133
10.67
39.04
10.9
Elimination of 2H2O and CH3OH
Exo
Exo
700.93 0.32380
750.83 0.68060
0.1188 135–
422.5
40.07 Elimination of 2(HC„CNH2), CO,
SO2 and Benz
0.2885 422.58– 31.54
1200
31.97 Elimination of 2(HC„CNH2), CO
and Benz. and formation of
cobalt oxide
Ni(L)2Á4H2O
Endo 348.59 0.050215
1.52 2.68 À0.0254
À8.8880
46.568 20.61–
116.62
12.26
11.48 Dehydration of 4H2O
Endo 493.00 0.094900
Endo 765.09 0.309100
Endo 974.94 0.105200
1.30 2.46 À0.0237
0.84 1.64 À0.0210
1.13 2.23 À0.0294
À11.727
À16.067
À28.705
57.207
79.976
28.972 118.48– 75.75
999.77
93.141
76.36 Elimination of 4(HC„CNH2),
CH4, CO, 2SO2 and 2 Benz. and
formation of nickel oxide
Exo
1190.4 0.397000
2.31 2.31 À0.0197
1.86 2.92 À0.0236
À23.492
À8.0680
Cu(L)2Á4H2OÁCH3OH Endo 341.15 0.0562
58.155 28.58–
122
10.27
5.44
10
Dehydration of 2H2O and
elimination of CH3OH
122–
5.51
Dehydration of 2H2O
253.42
Endo 607.36 0.0370
Endo 1214.7 0.0298
0.88 1.73 À0.0362
1.51 1.95 À0.0200
À22.041
À25.081
12.715 254.92– 14.99
365.23
14.15 Elimination of CO, CH4 and
HC„CH, N2
53.34 Elimination of 2(HC„CNH2),
2CO, SO2 and 2 Benz. And
formation of copper oxide
365.23– 53.31
834.00
83.458
at 25–301 °C and weight loss 18.55% corresponding to liberation of
5H2O and CH3OH molecules. Similarly an endothermic peak of cop-
per (II) complexes at 20–206 °C assigned to the liberation of 4H2O.
The other stepwise decomposition of the complexes started at 184,
303 and 208 °C as endothermic peaks for Co(II), Ni(II) and Cu(II)
complexes, respectively, with one exception where the last step
of Ni complexes proceed with exothermic reaction.
2. The low values of Z (collision factor) indicated the slow nature
of the reaction [45–50]. The degree of decomposition (
calculated and given in Tables 8a–11.
a) was
References
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molecule and methanol moiety. The peak at 16–93 °C for the Co(II)
complex with a weight loss 15.33% is due to liberation of 4H2O and
CH3OH molecules. Nickel complexes gave a peak at 20–130 °C with
a weight loss 10.63% corresponding to liberation of 4H2O. Mean-
while copper complexes gave a peak at 31–87 °C with a weight loss
9.16% equivalent to liberation of 2H2O and elimination of CH3OH
molecule. Other bands appeared at 87–232.66 °C due to liberation
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