Synthesis, characterization and quantum chemical ab initio calculations of new dimeric aminocyclodiphosph(V)azane and its Co(II), Ni(II) and Cu(II) complexes

Article abstract of DOI:10.1016/j.saa.2012.04.005

The complexes of type [M₂LCl₂] in which M = Co(II), Ni(II) and Cu(II) ions and L are 1,3-o-pyridyl-2,4-dioxo-2′,4′- bis(3-benzo[d]thiazol-2-yl-2-iminothiophene) cyclodiphosph(V)azane, were prepared and their structures were character

Full text of DOI:10.1016/j.saa.2012.04.005

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 95 (2012) 414–422
Contents lists available at SciVerse ScienceDirect
Spectrochimica Acta Part A: Molecular and
Biomolecular Spectroscopy
journal homepage: www.elsevier.com/locate/saa
Synthesis, characterization and quantum chemical ab initio calculations of
new dimeric aminocyclodiphosph(V)azane and its Co(II), Ni(II) and Cu(II) complexes
Abdel-Nasser M.A. Alaghaz a, , Abdullah G. Al-Sehemi , Tarek M. EL-Gogary
⇑
b
a,
⇑
a
Chemistry Department, Faculty of Science, Jazan University, Jazan, Saudi Arabia
Chemistry Department, Faculty of Science, King Khalid University, Abha, Saudi Arabia
b
a r t i c l e i n f o
a b s t r a c t
Article history:
Available online 21 April 2012
2 2
The complexes of type [M LCl ] in which M = Co(II), Ni(II) and Cu(II) ions and L are 1,3-o-pyridyl-2,4-
0
0
dioxo-2 ,4 -bis(3-benzo[d]thiazol-2-yl-2-iminothiophene) cyclodiphosph(V)azane, were prepared and
1
31
their structures were characterized by different physical techniques (IR, UV–Vis, H NMR, P NMR, mass,
TGA, DTA, XRD, SEM, magnetic moment and electrical conductance measurements). Ab initio calculations
at the level of DFT B3LYP/6-31G(d) were utilized to find the optimum geometry of the ligand. Spectral
characterization of the ligand was simulated using DT-DFT method. Infrared spectra of the complexes
indicate deprotonation and coordination of the imine NH. It also confirms that nitrogen atoms of the
pyridine group and thiazole group contribute to the complexation. NBO natural charges were computed
and discussed in the light of coordination centers. Electronic spectra and magnetic susceptibility mea-
surements as well as quantum chemical calculations reveal square planar geometry for Cu(II) and Ni(II)
complexes and tetrahedral geometry for Co(II) complex. The elemental analyses and mass spectral data
Keywords:
Cyclodiphosph(V)azane ligand
Metal complexes
IR
UV–Vis spectra
Ab initio calculations
NBO natural charges
2 2
have justified the M LCl composition of complexes.
Ó 2012 Elsevier B.V. All rights reserved.
1
. Introduction
Phosphazanes, which are the best known and most intensively
reaction of hexachlorocyclodiphosph(V)azanes with amino com-
pounds has been investigated in great details [12–14]. Transition
metal complexes with amino tetrachlorocyclodiphosph(V)azanes
as ligands have been amongst the widely studied coordination
compounds in the past few year, since they are found to be impor-
tant as biochemical, analytical and antimicrobial reagents [15,16].
The present-work aims chiefly to prepare the metal complexes of
studied phosphorus–nitrogen compounds, are materials with inter-
esting properties. For example, they exhibit fire-retardant proper-
ties, have high refractive indices, and might find application in
non-linear optics, as ferroelectric materials, as liquid crystals or as
photoactive materials [1–4]. They also possess a number of charac-
teristics such as biomedical properties and applications due to their
strong antitumor activity [5–7]. Their antimicrobial and biological
activities on bacterial and yeast cells have been studied [8–10].
Some applications include model compounds for polyphosphaz-
enes, starting materials for the preparation of cyclolinear and/or
cyclomatrix phosphazane substrates, commercial polymers with
carbon backbones containing pendant cyclophosphazane groups,
inorganic hydraulic fluids and lubricants, biologically important
substrates such as anticancer agents, insect chemosterilants,
pesticides and fertilizers, supports for catalysts, dyes, and crown
ether phase transfer catalysts for nucleophilic substitution reac-
tions, core substrates for dendrimers, thermal initiators for anionic
polymerization reactions and photosensitive materials [11]. The
2 2
ligand H L. In this work, novel ligand (H L) was prepared and its
behavior toward some transition metal ions was studied using dif-
1
31
ferent techniques such as elemental analyses, IR, H, P NMR, mass,
EPR, TGA, molar conductance, magnetic moment, UV–Vis spectra
and DFT quantum mechanical calculations.
2
. Experimental
2.1. Physiochemical studies
All reactions were carried out under purified nitrogen by stan-
dard Schlenk techniques [17]. All chemicals used in this investiga-
tion were of analytical grade, provided by B.D.H. chemicals.
Solvents were purified and dried by standard methods and distilled
5 5 2
under nitrogen prior to use. The [(C H N)NP(O)Cl] 1 synthesis was
⇑
Corresponding authors. Addresses: Department of Chemistry, Faculty of Science
Boys), Al-Azhar University, Nasr City, Cairo 11884, Egypt (A.-N.M.A. Alaghaz);
carried out according to Ref. [18] and 3-(benzo[d]thiazol-2-yl)-2-
aminothiophene 2 according to Ref. [19]. The stoichiometric
analyses (C, H, N, S, P, Cl and M) of the ligand and its metal
complexes were performed by the microanalytical center, Cairo
University, Giza, Egypt. The infrared spectra were recorded in Nujol
(
Department of Chemistry, Faculty of Science (Domyat), Mansoura University,
Domyat Al-Gideda, Egypt (T.M. EL-Gogary).
E-mail addresses: tarekelgogary@hotmail.com, tarekelgogary@yahoo.com
(
T.M. EL-Gogary).
1
386-1425/$ - see front matter Ó 2012 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.saa.2012.04.005

A.-N. M.A. Alaghaz et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 95 (2012) 414–422
415
mulls on a Shimadzu FT-IR spectrometer using KBr disks. Proton
nature as minima or transition states and to correct energies for
zero-point energy and thermal contribution. The frequencies are
scaled by a factor of 0.98. The vibrational modes were animated
using the ChemCraft program [24]. Electronic transitions were
computed within the time-dependent DFT (TD-DFT) formalism
[25] as implemented in Gaussian09 suite of programs [20]. Natural
charges were computed within full Natural Bond Orbital analysis,
using NBO version 3 implemented in Gaussian09 [20].
1
31
{
4
H} and
P {NMR} spectra were obtained on a JEOL JMTC
-DMSO solution in 5 mm diameter
00 MHz spectrometer using d
6
1
31
tubes. H spectra were referenced to TMS and P referenced to 85%
PO as external standards. Electronic spectra were recorded as
H
3
4
Nujol mulls and DMF saturated solutions on CARY 5 spectropho-
tometer. The molar conductance measurements were carried out
using a Sybron–Barnstead conductometer. Mass spectra were
recorded on GS/MS INCOS XL Finnegan MAT. The magnetic suscep-
tibilities of the complexes in the solid state were recorded on Sher-
wood Scientific magnetic susceptibility balance. The TGA were
recorded on a Shimadzu TGA-50H. TGA was carried out in a
4
. Results and discussion
4.1. The ligand
ꢀ1
dynamic nitrogen atmosphere (20 mL min ) with a heating rate
ꢀ1
of 10 °C min . EPR spectra of Cu(II) complex were recorded as
polycrystalline sample, at room temperature, on an E4-EPR spec-
trometer using the DPPH as the g-marker.
2
The analytically pure ligand H L (Fig. 1) was readily synthesized
with very good yield (86.74%) by the reaction of 1,3-(di-o-pyridyl)-
0
0
2
,4-(dioxo)-2 ,4 -dichlorocyclodiphosph(V)azane with two equiva-
lents of 3-(benzo[d]thiazol-2-yl)-2-aminothiophene in acetonitrile.
The purity of the ligand 98.68% has been checked by HPLC. Elemen-
tal analyses (Table 1) of the ligand reflected that the ligand has the
molecular formula that is given above. The EI-mass spectrum
2
2
.2. Synthesis of ligand (H L)
3
-(Benzo[d]thiazol-2-yl)-2-aminothiophene (4.64 g, 0.02 mol)
was added in small portions to a well stirred solution of 1,3-(di-
2
(Supplement Fig. S-1a) of the ligand (H L) shows a maxima peak
0
0
o-pyridyl)-2,4-(dioxo)-2 ,4 -dichlorocyclodiphosph(V)azane (3.47
g, 0.01 mol) in 100 ml acetonitrile during half an hour. After the
addition was completed, the reaction mixture was heated under
reflux for 12 h. After the completion of the reaction (HCl gas ceased
to evolve), the reaction mixture was filtered while hot and the solid
obtained was washed several times with acetonitrile, diethyl ether
and dried in vacuo to give the corresponding aminoacyclodiphaz-
at 740 u, corresponding to the aminocyclodiphosph(V)azane dimer
+
22 8 2 2 4
moiety ((C32H N O P S ) , calculated atomic mass 740 u) and a
number of peaks at 52, 223, 317, 368, 487 and 582 u, attributable
to different fragments of the ligand. The mass spectrum of the
ligand (H
Scheme S-1. The ligand H
cause it contains the phosphenous amide (–NH–P@O) bonds
26,27]. The IR spectrum (Fig. 2a, Table 2) does not show a (OH)
band at 3550 cm but shows the band at 3272 cm corresponding
to (NH) [26], indicating that in solid state, the ligand exists in the
keto form for the ligand H
2
L) shows the fragmentation pattern in Supplement
2
L may show keto-enol tautomerism be-
ane derivative (H
2
L), (yield 86.74%) with mp = 132–134 °C.
[
m
ꢀ1
ꢀ1
2
.3. Syntheses of metal complexes
m
1
2
L. However, the H NMR spectrum (Sup-
The metal complexes were prepared by adding dropwise a hot
aqueous (60 °C) solution (100 mL) of the metal chlorides
plement Fig. S-2a and Table S-1) of ligand exhibits a sharp singlet at
12.62 ppm due to enolic –OH which indicates that the amide
groups are transformed into iminol groups in solution [28]. The
(
0.1 mol) to a solution of H
2
L (0.1 mol) in tetrahydrofuran
3
1
(
100 mL) while stirring continuously. After complete addition of
P NMR (Supplement Fig. S-3) of the ligand records a signal at
the metal salt solution, the reaction mixture was heated under
reflux for about 18 h under dry conditions. The complexes obtained
were filtered, washed with water, ethanol, and tetrahydrofuran
and then dried in vacuo. The products obtained give elemental
analyses (Table 1) consistent with the proposed structures.
d = 64.63 ppm, which supports the phosphazo (P–N) nitrogen group
[5]. The electronic spectrum of H L (Supplement Fig. S-4a, Table 3)
2
ꢀ
1
in ethanol showed absorption bands at 40,818–21,932 cm
regions which is due to intra-ligand
⁄
⁄
p ? p and n ? p transitions
involving molecular orbital of the pyridine ring, a broad shoulder at
ꢀ1
approximately 22,831 cm was observed. The latter band is attrib-
⁄
uted to a n(oxygen) ?
p
transition of the dipolar zwitter ionic
3
. Computational methods
2
structure or keto-amine tautomer of H L [26,29].
All electronic structural calculations were performed using the
Gaussian09 suite of programs [20]. Geometry optimizations for
all tautomers have been performed using semi-empirical AM1
method and ab initio Density Functional Theory (DFT) at the
B3LYP functional [21–23], in conjunction with the 6-31G(d) basis
set. For each stationary point, we carried out a vibrational
frequency calculation at the same levels to characterize their
4.2. Quantum chemical calculations
4.2.1. Geometry
Since single crystal X-ray structure for the ligand is not avail-
able, quantum chemical calculations were utilized to find the
geometry optimized structures for the H
2
L at different quantum
Table 1
2
Elemental analyses, melting points, colours, yields and composition of ligand (H L) and its corresponding metal complexes (1–3).
Compd. No.
M.F. (M.Wt)
M.p. (°C)
Yield Elemental analyses Found (Calc.), %
(%)
aK
Colour
132–134 Yellow 86.74
M
Cl
–
C
H
N
P
S
H
2
L
–
51.87 (51.88) 2.94 (2.99) 15.07 (15.13) 8.39 (8.36) 17.30 (17.31) –
32 22 8 2 2 4
C H N O P S (740.78)
(
(
(
1) C32
Co
2) C32
Ni
3) C32
Cu
H
20Cl
LCl
20Cl
LCl
20Cl
LCl
2
2
2
Co
2
N
8
O
2
P
2
S
4
(927.53) 188–190 Orange 62.68 12.69 (12.71) 7.58 (7.64) 41.41 (41.44) 2.13 (2.17) 12.03 (12.08) 6.64 (6.68) 13.88 (13.83) 5.23
(927.05) 192–194 Brown 64.39 12.64 (12.66) 7.62 (7.65) 41.42 (41.46) 2.13 (2.17) 12.04 (12.09) 6.63 (6.68) 13.80 (13.84) 4.64
(936.76) 197–199 Brown 67.26 13.54 (13.57) 7.54 (7.57) 41.07 (41.03) 2.12 (2.15) 11.99 (11.96) 9.64 (6.61) 13.62 (13.69) 7.62
[
2
2
]
H
N
8
Ni O P S
2 2 2 4
[
2
2
]
H
Cu
2
N
8
O
2
P
2
S
4
[
2
2
]
a
(molar conductance X-1cm mol ).
2
ꢀ1
K

4
16
A.-N. M.A. Alaghaz et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 95 (2012) 414–422
N
N
S
O
N
N
S
H
N
H
N
P
P
S
O
S
N
N
N
N
N
N
S
S
OH
P
OH
P
N
N
S
N
N
S
H
N
P
N
N
P
N
S
S
OH
O
S
S
N
N
N
N
2
Fig. 1. Three possible isomeric forms in solution of ligand H L.
2
Fig. 2. (a) IR spectrum of H L ligand, (b) IR spectrum of Co(II) complex (1), (c) IR spectrum of Ni(II) complex (2), and (d) IR spectrum of Cu(II) complex (3).
mechanical levels. Fig. 3 shows the optimized structure of the H
2
L
2 2
no bonds are much shorter than P–N distances in the P N ring
cis-dione at B3LYP/6-31G(d). An inspection of the resulting struc-
ture easily shows two close contacts H-bonding interactions
between the amine-H and the thiazole-N of length 1.826 Å. This in-
(1.741 vs. 1.786 Å) which confirms the multiple PN connection in
P@N-thiophen derivative. The lengths of the thiophene-C–Nimino
bonds are also different from the classical thiophene-C–Nimino case.
The shortening of thiophene-C–Nimino bonds could be due to exten-
tra-molecular interaction is also shown by H
H-bond length (1-862 Å). Table 4 presents some selected com-
puted geometrical parameters of H L cis-dione. Since dispersion
2
L cis-ol with a longer
sion of the
p electron conjugation of the thiophene ring. Another
2
2
possible explanation is that the imino nitrogen atom with sp hy-
brid orbitals has more s-character and the maximum of the elec-
tron density is closer to the nuclei compared with the electron
energies do not play a considerable role in these types of struc-
tures, electron correlations are not so important consequently
3
DFT methods would provide a good quality structures. The P
2
N
2
density distribution at sp hybridized amino nitrogen, and this
ring is almost planar and P–N bonds in the ring are almost of equal
length (1.786 Å). The exocyclic phosphorus-nitrogen groups have
exo orientation relative to the phosphazane ring. The phosphoimi-
leads to shortening of the thiophene-C–Nimino bonds. Our
structural data given in Supplement Table S-2 agrees well with
the available X-ray data on P N ring-containing compounds
2 2

A.-N. M.A. Alaghaz et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 95 (2012) 414–422
417
Table 2
2
Important IR bands of H L ligand and its complexes (1–3) with their assignments.
Assignments
Ligand (H
2
L)
1
2
3
m
m
m
m
m
m
m
m
(NH)
3272
1631
1510, 595, 475
–
1613
1525, 614, 525
707
293
348
244
328
–
1613
1523, 612, 524
712
296
345
246
327
–
1612
1522, 610, 523
710
297
343
249
330
(C@N)thiazole
pyridine ring
(C–S–C)
(M–N) imine
(M–N)) pyridine
(M–N)thiazole
(M–Cl)
704s
–
–
–
–
Table 3
Molar conductance, magnetic moment and electronic spectral data of the complexes.
ꢀ
1
cm2 molꢀ1
ꢀ1
Complex
Molar conductance (
X
)
Geometry
Magnetic moments (
lB)
Band assignments
k
max (cm
)
a
b
l
compl.
l
eff
⁄
⁄
Ligand H
2
L
–
–
–
INCT (
INCT (
p
p
?
?
p
p
p
)
)
40,818
36,914
34,014
27,025
25,387
21,932
⁄
INCT (n ?
LMCT (n ?
LMCT (n ?
LMCT (n ?
4
)
⁄
p
p
p
)
)
)
⁄
⁄
[
[
[
Co
2
LCl2]
12.45
9.34
Tetrahedral
7.87
–
4.77
–
A
2
A
2
A
2
? 4
?
T
T
T
1
1
1
(P)
(F)
14,948
14,124
4500
4
4
4
4
?
1
1
2
? 1
?
Ni
2
LCl2]
Square planar
A
A
1
A
B
B
2
15,267
17,890
14,970
1
1
1
2
B
1
?
2
Cu
2
LCl2]
10.68
Square planar
3.32
1.73
2B
1
? 2
E
19,455
a
l
l
compl. is the magnetic moment of all metal ions present in the complex.
eff. is the magnetic moment of one metal ion in the complex.
b
2
from the local minimum for the ligand H L is presented in Fig. 4.
It also reflects the complexity of the potential energy surface as
well as its flatness.
4.2.2. Simulated spectra
2
Simulated IR spectra of different isomers of H L were calculated
at the level B3LYP/6-31G(d). Fig. 5a and b displays the simulated IR
spectra for the cis-dione and cis-ol tautomers scaled by 0.98 as a
scale factor [32]. Inspection of the calculated frequencies shows
that they agree with the experimentally measured IR spectra. The
vibrational frequencies were animated with ChemCraft to assign
frequencies to their normal modes.
DT-DFT calculations were done for the free ligand in the molec-
ular gas state. The computed UV–Vis spectra of H
three absorption bands at 218.8 (f = 0.0015), 273.3 (f = 0.5893) and
80.6 (f = 0.1185) nm. It is clear that the computed UV data could
be compared with the measured spectra.
2
L diketo cis gives
2
4.2.3. Natural charges
Natural charges were computed within full Natural Bond Orbi-
tal analysis, using NBO version 3 implemented in Gaussian09 [19].
Computed natural charges of H L cis-dione at b3lyp/6-31G(d) are
2
2
Fig. 3. Optimized structure of H L cis-dione at the level of B3LYP/6-31G(d).
shown in Table 4. Charges are distributed homogenously on the
molecular structure with a charge separation detected. The most
negative centers are ring-N (ꢀ1.16), amino-N (ꢀ1.06), the exo-cyc-
lic O (ꢀ1.04), thiazole-N (ꢀ0.59) and pyridine-N (ꢀ0.55). These
places of accumulated negative charges are the most likely coordi-
nated centers. On the other hand the positive charges are popu-
lated on the P (2.45), the amino-H (0.52) and C5,17 in the
pyridine rings (0.46) is between two more electronegative N
atoms. Sulfur atoms are also positively charged where the thio-
phene-S is more positive (0.4) than the thiazole-S (0.29). This is
possibly because of two reasons, the presence of more electroneg-
[
30,31]. It is obvious that these ligands with 70 atoms of which 48
heavy atoms are considered large systems for an optimization pro-
cess using a sophisticated ab initio method. They also have flexible
structures with large number of degrees of freedom. This would
provide a complex potential energy surface which is flat in nature.
Supplement Fig. S-5 shows the route of the optimization process
for H Lwhich exhibit a sharp decrease of energy at point 36. The
2
flatness of the potential energy surface can easily be detected in
the Supplement Fig. S-5. The deviation of every optimization step

4
18
A.-N. M.A. Alaghaz et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 95 (2012) 414–422
Table 4
4.3 Complexes
2
Computed natural charges of H L cis-dione at b3lyp/6-31G(d).
Atomic center
Natural charge
Atomic center
Natural charge
On the basis of elemental analyses, the complexes were as-
signed to possess the composition shown in Table 1. Nitrobenzene
solutions of the complexes show negligible conductance. Hence, it
is concluded that the anions are present in the coordination sphere
of the molecules [26]. Thus, these complexes may be formulated as
C1
C2
C3
N4
C5
C6
N7
P8
ꢀ0.15
ꢀ0.33
0.07
C36
C37
C38
C39
C40
N41
S42
0.14
ꢀ0.23
ꢀ0.22
ꢀ0.23
ꢀ0.24
ꢀ0.59
0.29
ꢀ0.55
0.46
[
2
[M
,4-(dioxo)-2 ,4 -bis(3-(benzo[d]thiazol-2-yl)-2-iminothiophene)
cyclodiphosph(V)azane.
2 2
LCl ], where M = Co(II), Ni(II) and Cu; L = 1,3-(di-o-pyridyl)-
ꢀ0.33
ꢀ1.16
2.45
0
0
C43
C44
C45
C46
C47
C48
H49
H50
H51
H52
H53
H54
H55
H56
H57
H58
H59
H60
H61
H62
H63
H64
H65
H66
H67
H68
H69
H70
ꢀ0.2
P9
2.45
0.14
N10
N11
C12
C13
C14
C15
S16
C17
C18
C19
C20
C21
N22
O23
N24
C25
C26
C27
C28
S29
C30
C31
O32
N33
S34
C35
ꢀ1.16
ꢀ1.06
0.16
ꢀ0.27
ꢀ0.22
ꢀ0.42
0.4
ꢀ0.23
ꢀ0.24
ꢀ0.23
ꢀ0.22
0.25
0.25
0.24
0.26
0.52
0.26
0.27
0.26
0.25
0.25
0.24
0.52
0.26
0.27
0.25
0.26
0.25
0.24
0.25
0.24
0.25
4.3.1. IR spectra and mode of bonding
The assignments of the main IR absorption bands of the free li-
gand and its metal complexes are given in Fig. 2, Table 2. The IR
ꢀ1
spectrum of the ligand shows a broad band at 3272 cm , which
can be attributed to (NH) group [33]. This band disappears in all
m
0.46
complexes, which can be attributed to the involvement NH in coor-
dination. In the IR spectra of the complexes (Fig. 2b and c) the most
useful vibrational bands of the complexes for establishing the
mode of coordination are reported in Table 2. All IR spectra of
ꢀ0.33
ꢀ0.15
ꢀ0.33
0.07
ꢀ0.55
ꢀ1.04
ꢀ1.06
0.16
ꢀ0.27
ꢀ0.22
ꢀ0.42
0.4
0.2
0.2
ꢀ1.04
ꢀ0.59
0.29
ꢀ0.2
the complexes exhibit medium to strong bands at about 1576–
ꢀ1
1
592 and 1465–1482 cm as expected for the highest pyridine
and thiazole ring vibrations [34]. In addition, the peak at
ꢀ1
704 cm attributed to the absorption of mC–S–C of the benzothiaz-
ꢀ1
olyl ring [35] appears in the range 707–712 cm in the M(II) com-
plexes, indicating that the S atom is not coordinated with the metal
ꢀ1
ion too. The C@N stretching vibration observed at 1631 cm for
ꢀ1
H
2
L is shifted to ca.1613 cm in the M(II) complexes, and the shift
extent is similar to the M(II)–imidazole complex [36,37]. These
facts indicated that H L is coordinated with M(II) via nitrogen atom
2
on the thiazole ring, which is similar to the binding of benzothia-
zole derivatives to a number of other metals reported previously
0.26
[
38–42]. The pyridine-ring-stretching, in-plane-ring-bending and
out of-plane-ring-bending vibrations are found at 1510, 595 and
ꢀ
1
4
75 cm , respectively. These absorptions are highly affected when
ative N atom and the engagement of the mobile electron cloud in
the delocalization of the extended benzothiazole system.
nitrogen atom of pyridine ring takes part in coordination. In the
complexes the position of these absorption bands is shifted to
2
Fig. 4. The deviation from local minimum geometry at every optimization step of H L cis-dione at the level of B3LYP/6-31G(d).

A.-N. M.A. Alaghaz et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 95 (2012) 414–422
419
2
Fig. 5a. Simulated IR spectrum of cis-dione H L at b3lyp/6-31G(d).
higher region. This indicates that the nitrogen of pyridine ring is in-
volved in coordination [43]. The low frequency pyridine
idine) and thiazole (M–NThiazole) modes lie in the ranges 348–343
comprise the two
data reveal to suggest that the ligand is hexadentate coordinating
through nitrogen only [N ].
6
m(M–Nimino) vibrations [26]. These IR spectral
m
(M–NPyr-
m
ꢀ
1
and 244–249 cm , respectively. This suggests the involvement
of pyridine [44] and thiazole [44] rings in coordination. The bands
4.3.2. Mass spectra
The FAB mass spectra of Co(II) (Supplement Fig. S-1b), Ni(II)
(Supplement Fig. S-1c) and Cu(II) (Supplement Fig. S-1d) com-
ꢀ1
at 327–330 cm are present in chloro complexes which are attrib-
ꢀ
1
uted to the
m(M–Cl) [45]. The bands at 293–297 cm
may
Fig. 5b. Simulated IR spectrum of cis-ol H2L at b3lyp/6-31g(d)

4
20
A.-N. M.A. Alaghaz et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 95 (2012) 414–422
+
plexes have been recorded. The mass spectra give [M] 927 for
downfield due to the drifting of environmental electrons toward
the nickel ion.
+
+
[
Co
2 2 2 2 2 2
LCl ] (1), [M+1] 929 for [Ni LCl ] (2) and [M] 936 [Cu LCl ]
(3). These data in good agreement with the proposed molecular
formula for these complexes. In addition to the peaks due to the
molecular ion, the spectra exhibit peaks assignable to various frag-
ments arising from the thermal cleavage of the complexes. The
peal intensity gives an idea of the stability of the fragments. The
pathway fragmentation pattern of the mass spectrum of the Co(II)
complex is described in Supplement Scheme S-2.
4.3.6. EPR spectra
The EPR spectrum of Co(II) complex was recorded as polycrys-
talline sample. No EPR signal was observed at room temperature
because the rapid spin lattice relaxation of Co(II) broadens the lines
at higher temperature. It shows a very broad signal at liquid nitro-
gen temperature. The deviation of ‘g’ values from the free electron
value (2.0023) may be due to angular momentum contribution in
the complexes [52,53]. The EPR spectrum of the copper(II) complex
4.3.3. Magnetic moment
(
g
Supplement Fig. S-6) shows two lines having g|| value at 2.11 and
at 2.04. g|| value being less than 2.3, witnesses more covalency
in metal–ligand interaction [52]. Further it is noteworthy that the
The magnetic moments for the complexes are shown in Table 1.
The magnetic moments of the copper(II) and cobalt(II) complexes
are 1.73 and 4.77 BM, respectively, which suggest square planar
geometry for copper(II) complex and tetrahedral geometry for co-
balt(II) complex [46,47]. For tetrahedral cobalt(II) complex, the
\
9
II
\ e
relation g|| > g g (2.0029) is typical of axially symmetric d Cu ion
having one unpaired electron in dx2
ꢀy2
orbital [53].
state acquires orbital angular momentum only indirectly through
4
the mixing of the T
2
state by a spin–orbit coupling perturbation.
4.3.7. Cyclic voltammetry studies
The nickel(II) complex is diamagnetic at room temperature reveal-
ing the square planar geometry for nickel(II) complex around the
metal (II) ion [46].
The cyclic voltammogram of the copper complex (Supplement
Fig. S-7) recorded at room temperature shows a quasi-reversible
peak for the Cu(II) ? Cu(III) couple at 0.72 V with a direct cathodic
peak for Cu(III) ? Cu(II) at 0.61 V. It also exhibits two irreversible
peaks in cathodic region characteristics for Cu(II) ? Cu(I) at
4.3.4. Electronic spectra
ꢀ0.74 V and Cu(I) ? Cu(0) at ꢀ0.92 V. These two peaks show their
The electronic spectra of the complexes are presented in Table
reduction behavior of copper in complex. In anodic region it
exhibits two peaks which correspond to oxidative behavior of
Cu(0) ? Cu(I) and Cu(I) ? Cu(II) is observed.
3
4
. Two very strong bands in the region 34,014–21,932 and
ꢀ1
0,818–36,914 cm in the spectra of the complexes, are attributed
⁄
⁄
to n ?
p and p ? p transitions in aromatic ring and C@N chro-
mophore [48]. Cobalt(II) complex (Supplement Fig. S-4b) shows
absorption bands at 14,948 cm assigned to A ? T (P) transi-
2 1
tion. The existence of spin–orbit coupling also allows some quar-
tet ? doublet spin transition to occur. Another band at
ꢀ1
4
4
4.3.8. X-ray diffraction and SEM analysis
No peaks have been observed in X-Ray diffraction (Fig. 6) pat-
terns of the powdered ligand (H
3) and this confirmed their amorphous nature. The morphology
and particle size of the ligand H L and Ni(II) metal complex have
2
L) and its metal complexes (1–
ꢀ
1
4
4
4
? 4T
1
4,124 cm is assigned to A
2
? T
1
(F). The expected A
2
1
ꢀ1
2
transition appearing at a 4500 cm is overlapped by ligand vibra-
tion transitions (i.e., the infrared bands) suggests tetrahedral
geometry of the complex [49,50] which is also corroborated by
magnetic moment value of the complex. Spectra of the nickel com-
plex (Supplement Fig. S-4c) show an absorption band at
been illustrated by the scanning electron micrography (SEM).
Supplement Fig. S-8 depicts the SEM photographs of the synthe-
sized ligand H L and Ni(II) metal complex. It was noted that there
2
is a uniform matrix of the synthesized complexes in the pictograph
which leads to a belief that it is a homogeneous phase material. An
ꢀ1
1
1
1
5,263 cm , assignable to a A
1
? A
2
transition and a shoulder
ꢀ1
1
1
ice rock like shape is observed in the ligand H
size of 10 m. However Ni(II) complex is an ice sponge shaped
morphology with 10 m particle size.
2
L with the particle
at 17,892 cm corresponding to a A
1
? B
1
transition which are
l
consistent with square planar stereochemistry about the nickel(II)
ion [40]. The visible spectrum of copper complex (Supplement
Fig. S-4d), shows two absorption bands at 14,970 and
l
ꢀ1
2
2
2
2
1
9,455 cm
assignable to
B
1
? B
2
and
1
B ? E transitions
respectively, which indicates the possibility of square planar
geometry of the metal complex [51].
1
31
4
.3.5. H NMR and P NMR spectral study
2
The proton NMR spectra of the ligand H L and its diamagnetic
Ni(II) complex (Supplement Fig. S-2a and b) were recorded in
DMSO-d solution using tetramethylsilane (TMS) as internal stan-
dard. The chemical shifts of the different types of protons of the li-
gand H L and its diamagnetic Ni(II) complex are listed in
Supplement Table S-1. The NH signal found at 3.03 ppm in the
spectrum of the ligand H L is completely disappeared in the spec-
6
2
2
tra of the Ni(II) complex. This indicates the involvement of the NH
group in chelation with Ni(II) through displacement of the NH
proton. The phosphorus thirty one NMR spectra of the ligand H
and its diamagnetic Ni(II) complex (Supplement Fig. S-3a and b)
were recorded in DMSO-d solution using H PO as internal stan-
dard. The P NMR study also supports the proposed structure of
2
L
6
3
4
3
1
31
the compounds. As reported earlier the position of the P chemical
shifts is not influenced by the paramagnetic nature of the metal
3
1
2
ions. The P spectra of H L showed signal at 64.63 ppm. In the case
3
1
of complex the P spectrum of Ni(II) complexes showed signal
at 59.23 ppm [26], respectively. This signal is actually shifted
Fig. 6. (a) XRD diagram of H
XRD diagram of Ni(II) complex (2), and (d XRD diagram of Cu(II) complex (3).
2
L ligand, (b) XRD diagram of Co(II) complex (1), (c)

A.-N. M.A. Alaghaz et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 95 (2012) 414–422
421
4
.3.9. Thermal analyses
Thermogravimetric (TG) and differential thermogravimetric
13. These quantum chemical calculations agree well with the
experimental findings of the spectral and magnetic observations.
(
DTG) analyses were carried out for Co(II), Ni(II) and Cu(II) com-
plexes in ambient conditions. The correlations between the differ-
ent decomposition steps of the complexes with the corresponding
weight losses are discussed in terms of the proposed formula of the
Appendix A. Supplementary data
Supplementary data associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.saa.2012.04.005.
complexes. The thermal decomposition of [Co
plement Fig. S-9a) with the molecular formula [C32
Co ] proceeds with two main degradation steps. The first step
2 2
LCl ] complex (Sup-
2 8 2 2 4-
H20Cl N O P S
2
References
occurs within the temperature range 480–585 K with an estimated
mass loss 49.62% (calculated mass loss = 49.66%) which is reason-
[1] L. Stahl, Coord. Chem. Rev. 210 (2000) 203–250.
ably accounted for the loss of two molecules of C22
H
12
N
4
S
4
frag-
[2] T.A. Mohamed, W.M. Zoghaib, I.A. Shaaban, R.S. Farag, A.M.A. Alajhaz,
Spectrochim. Acta A 83 (2011) 304–313.
ment. The DTG curve gives an exothermic peak at 640 K (the
maximum peak temperature). The second step occurs within the
temperature range 590–790 Kwith an estimated mass loss 34.13%
[
3] H. Abdel–Wahab, A. Abdel-Fattah, M.Y. Gabr, Prog. Org. Coat. 69 (2010) 272–
77.
2
[4] W.-K. Wong, X.-P. Chen, T.-W. Chik, W.-Y. Wong, J.-P. Guo, F.-W. Lee, Eur. J.
Inorg. chem. 2003 (2003) 3505–3667.
(
calculated mass loss = 34.18%), which is reasonably accounted
[
5] T.M. El-Gogary, A.M.A. Alaghaz, R.A.A. Ammar, J. Mol. Struct. 1011 (2012) 50–
8.
for the loss of rest of the ligand molecule, leaving CoO as residue.
The DTG curve gives an exothermic peak at 700 K (the maximum
peak temperature). Total estimated mass loss is 83.75% (calculated
5
[6] P. Chandrasekaran, J.T. Mague, R. Venkateswaran, M.S. Balakrishna, Eur. J.
Inorg. Chem. 2007 (2007) 4988–4997.
[
7] M. Sakamoto, K. Manseki, H. Okawa, Coord. Chem. Rev. 219–221 (2001) 379–
14.
[8] H.B. Gray, B.G. Malmstroem, Biochemistry 28 (1989) 7499–7505.
9] V. Konar, O. Yı lmaz, A.I. Ozturk, S. Kı rbag, M. Arslan, Bioorg. Chem. 28 (2000)
14–225.
mass loss = 83.84%). The thermal decomposition of [Ni
complex (Supplement Fig. S-9b) with the molecular formula
Ni ] also proceeds with two main degradation
2 2
LCl ]
4
[
[
C
32
H20Cl
2
N
8
O
P S
2 2 4
2
2
steps. The first estimated mass loss of 24.44% (calculated mass
loss = 24.84%) within the temperature range 590–620 K could be
[
10] O. Yılmaz, F. Aslan, A.I. Ozturk, N. Vanlı, S. Kırbag, M. Arslan, Bioorg. Chem. 30
(2002) 303–314.
attributed to the liberation of C11
gives an exothermic peak at 590 K (the maximum peak tempera-
ture). The second step occurs within the temperature range 650–
H
6
N
2
S
2
fragment. The DTG curve
[11] M. Gleria, R.D. Jaeger, J. Inorg. Organomet. Polym. 11 (2001) 1–45.
12] C.D. Flint, E.H.M. Ibrahim, R.A. Shaw, B.C. Smith, C.P. Thakur, J. Chem. Soc. A
1971) 3513.
[13] A.L. Odom, A.F. Heyduk, D.G. Nocera, Inorg. Chim. Acta 297 (2000) 330–337.
[14] T. Kniess, R. Bergmann, M. Kuchar, J. Steinbach, F. Wuest, Bioorg. Med. Chem.
[
(
8
20 K with an estimated mass loss 59.00% (calculated mass
loss = 59.04%), which is reasonably accounted for the decomposi-
tion of remaining part of the ligand molecule (C21
1
7 (2009) 7732–7742.
15] W.-Y. Wong, W.-K. Wong, C. Sun, W.-T. Wong, J. Organomet. Chem. 612 (2000)
60–171.
[
2 6 2 2
H14Cl N P S )
1
leaving NiO as residue. The DTG curve gives an exothermic peak
at 760 K (the maximum peak temperature). Total estimated mass
loss is 83.84% (calculated mass loss = 83.88). The complex
[16] W.-K. Wong, X.-P. Chen, J.-P. Guo, Y.-G. Chi, W.X. Pan, W.-Y. Wong, J. Chem.
Soc., Dalton Trans. (2002) 1139–1146.
[
17] D.F. Shriver, M.A. Drezdzon, The Manipulation of Air–Sensitive Compounds,
second ed., John-Wiley, New York, 1986.
[
Cu
2
LCl
2
] with the molecular formula [C32
H
20Cl
2
N
8
O
2
P
2
S
4
Cu
2
] is
[18] A.C. Chapmann, N.L. Paddock, H.T. Searle, J. Chem. Soc. 1825 (1961);
A.V. Kirsanov, I.N. Zhmurova, Zh. Obshch. Khim. 32 (1963) 2576–2588.
thermally decomposed in two successive decomposition steps
(
(
5
The DTG curve gives an exothermic peak at 553 K (the maximum
peak temperature). The second step occurs within the temperature
range 661–853 K with the estimated mass loss 48.54% (calculated
mass loss = 48.59%) which corresponds to the loss of
[
[
19] K. Gewald, E. Scinka, H. Bottcher, Chem. Ber. 99 (1966) 94–109.
20] M.J. Frisch, et al., Gaussian09, Revision A.02, Gaussian, Inc., Wallingford, CT,
2009.
Supplement Fig. S-9c). The first estimated mass loss of 34.38%
calculated mass loss = 34.41%) within the temperature range
40–590 K may be attributed to the loss of (C16H N S ) fragment.
10 4 2
[
[
[
21] A.D. Becke, J. Chem. Phys. 98 (1993) 5648–5652.
22] C. Lee, W. Yang, R.G. Parr, Phys. Rev. B 37 (1988) 785–789.
23] P.J. Stephens, F.J. Devlin, C.F. Chabalowski, M.J. Frisch, Phys.Chem. 98 (1994)
11623–11627.
[24] M.E. Casida, in: D.P. Chong (Ed.), Recent Advances in Density Functional
Methods Part 1, World Scientific, Singapore, 1995.
[
[
25] R.E. Stratmann, G.E. Scuseria, M.J. Frisch, J Chem Phys. 109 (1998) 8218–8224.
26] A.M.A. Alaghaz, Reda A.A. Ammar, Eur. J. Med. Chem. 45 (2010) 1314–1322.
16 10 4 2 2 2
C H N S Cl P fragment leaving CuO as residue. The DTG curve
gives an exothermic peak at 770 K (the maximum peak tempera-
ture). Total estimated mass loss is 83.00% (calculated mass
loss = 82.95%).
[27] B. Hoge, C. Thösen, T. Herrmann, P. Panne, I. Pantenburg, J. Fluor. Chem. 125
2004) 831–851;
(
P.R. Olivatoa, A. Rodriguesa, R. Rittner, J. Mol. Struct. 705 (2004) 91–99.
[
28] S. Chandra, L.K. Gupta, A.K. Sharma, Spectrochim. Acta A 60 (2004) 1563–1571.
The final product of decomposition at 875 K corresponds to the
formation of metal oxide as the end product, which was confirmed
by comparing the observed/estimated and the calculated mass of
the pyrolysis product. From the above thermogravimetric analyses,
the overall weight losses for the Co(II), Ni(II) and Cu(II) complexes
agree well with the proposed formulae obtained by elemental
analyses, IR, UV–Vis, H NMR, P NMR, Cyclic voltammetry, Mass,
and magnetic susceptibility measurements. Finally, the previous
findings indicated that the coordination occurs through the nitro-
gen of the pyridine ring and thiazole ring and the imine NH group
to give the structures shown in Supplement Fig. S-10.
[29] P.W. Alexander, R.J. Sleet, Aust. J. Chem. 23 (1970) 1183–1190.
[
30] K.V. Axenov, M. Leskelä, D. Timo Repo, Electronic Thesis Available at <http://
ethesis.helsinki.fi/julkaisut/mat/kemia/vk/axenov/chemistr.pdf>.
[
31] N.N. Bhuvan Kumar, K.C. Kumara Swamy, Polyhedron 26 (2007) 883–890.
[32] M. Alecu, J. Zheng, Y. Zhao, D.G. Truhlar, J. Chem. Theory Comput. 6 (2010)
872–2887.
33] R. Schoth, D. Sevenard, K. Pashkevich, G. Röschenthaler, Coord. Chem. Rev. 210
2000) 101–134.
2
[
(
1
31
[34] K. Nakamoto, Infrared and Raman Spectra of inorganic and coordination
compounds. Part B: applications in coordination, fifth ed., Organometallic and
Bioinorganic Chemistry, Wiley, New York, 1997.
[
35] W.W. Simons, The Sadtler Handbook of Infrared Spectra, Sadtler Research
Laboratories Inc., Pennsylvania, 1978.
[
36] W.-Y. Wong, X.-Z. Wang, Z. He, K.-K. Chan, A.B. Djuriši c´ , K.-Y. Cheung, C.-T. Yip,
A.M.-C. Ng, Y.Y. Xi, C.S.K. Mak, W.-K. Chan, J. Am. Chem. Soc. 129 (2007)
14372–14380.
[
37] W.-Y. Wong, C.-L. Ho, Acc. Chem. Res. 43 (2010) 1246–1256.
4
.3.10. Quantum chemical calculations on complexes
Geometry of Cu, Co and Ni complexes was investigated by semi-
[38] L. Li, C.-L. Ho, W-Y. Wong, J. Organomet. Chem. 703 (2012) 43–50.
[
[
39] W.-Y. Wong, K.-H. Choi, G.-L. Lu, Z. Lin, Organometallics 21 (2002) 4475–4481.
40] W. Wong, S. Chan, K. Choi, K. Cheah, W. Chan, Macromol. Rapid Commun. 21
empirical molecular orbital calculations using the PM3 Hamilto-
nian. The resulting structures prove square planar geometry for
Ni complex, distorted square planar geometry for Cu complex and
a tetrahedral geometry for the Co complex. These can be detected
in their optimized geometry present in Supplement Figs. S-11–S-
(
2000) 453–457.
[41] J. Yang, Z. Zhang, X. Xu, X. Zhu, X. Men, X. Zhou, J. Mater. Chem. 22 (2012) 643–
52.
[
[
6
42] X.F. He, C.M. Vogels, A. Decken, S.A. Westcott, Polyhedron 23 (2004) 155–160.
43] S. Chandra, A.K. Sharma, Spectrochim. Acta A 72 (2009) 851–857.
[44] D. Shukla, L. Kumar Gupta, S. Chandra, Spectrochim. Acta A 71 (2008) 746–750.

4
22
A.-N. M.A. Alaghaz et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 95 (2012) 414–422
[
[
45] S. Chandra, Sangeetika, Spectrochim. Acta A 60 (2004) 2153.
46] B.K. Singh, U.K. Jetley, R.K. Sharma, B.S. Garg, Spectrochim. Acta A 68 (2007)
[50] K. Nakamoto, S.J. McCarthy, Spectroscopy
Compounds, John Wiley & Sons, USA, 1968.
& Structure of Metal Chelate
6
3–73.
[51] T.P. Chessman, D. Hall, T.N. Waters, J. Chem. Soc. A (1966) 694–695.
[52] D. Kivelson, R. Nieman, J. Chem. Phys. 35 (1961) 149–155.
[53] V.F. Shulgin, A.N. Gusev, Ya. Zub, G.M. Larin, Russ. Chem. Bull. 51 (12) (2002)
2268–2273.
[
[
47] B.N. Figgs, Introduction to Ligand Fields, Interscience, New York, 1966.
48] D.H. Williams, I. Flemings, Spectrophotometric Methods in Organic Chemistry,
fourth ed., McGraw-Hill, London, 1989.
[
49] M. Ciampolini, Struct. Bond. 6 (1969) 52–93.