Complexation, thermal and catalytic studies of N-substituted piperazine, morpholine and thiomorpholine with some metal ions

Article abstract of DOI:10.1016/j.saa.2013.09.031

Several Cu(II), Pt(II) and Ni(II) complexes of N-substituted, piperazine (NN donor), morpholine (NO donor) and thiomorpholine (NS donor) derivatives were synthesized and their thermal behavior and catalytic activity in epoxidation reaction of cis-diphenylethylene were studied using oxygen sources NaOCl. The coordination compounds of Cu(II), Pt(II) and Ni(II) having general formula [MLCl]Cl, [ML₂l]Cl₂ or [ML]Cl₂ with tetra coordinated geometry around metal ions have been isolated as solid. All the ligands and complexes were identified by spectroscopic methods and elemental analysis, magnetic measurements, electrical conductance and thermal analysis. A square planer structures have been proposed for all complexes. The thermal stability of the complexes discussed in terms of ligands donor atoms, geometry and central metal ions. The complexes have a similar thermal behavior for the selected metal ions. The thermogravimetric analyses suggest high thermal stability for most complexes followed by thermal decomposition in different steps. The decomposition processes were observed as water elimination, chloride anion removal and degradation of the organic ligands. Catalytic ability of the complexes were examined and found that all the complexes can effectively catalyze the epoxidation of cis-stilbene with NaOCl.

Full text of DOI:10.1016/j.saa.2013.09.031

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 118 (2014) 572–577
Contents lists available at ScienceDirect
Spectrochimica Acta Part A: Molecular and
Biomolecular Spectroscopy
journal homepage: www.elsevier.com/locate/saa
Complexation, thermal and catalytic studies of N-substituted piperazine,
morpholine and thiomorpholine with some metal ions
Mesut Kacan b, Murat Turkyilmaz b, Ferhat Karabulut b, Ozlen Altun b, Yakup Baran a,
⇑
a University of Wollongong, Department of Chemistry, Wollongong 2522, NSW, Australia
b Trakya University, Science Faculty, Department of Chemistry, Edirne, Turkey
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
ꢀ
ꢀ
ꢀ
ꢀ
Nine new metal complexes were
prepared.
Catalytic activity of the complexes
were studied.
Thermal stabilities of the complexes
were determined.
Cataltytic epoxidation of
cis-diphenylethylene was studied.
a r t i c l e i n f o
a b s t r a c t
Article history:
Several Cu(II), Pt(II) and Ni(II) complexes of N-substituted, piperazine (NN donor), morpholine (NO
donor) and thiomorpholine (NS donor) derivatives were synthesized and their thermal behavior and cat-
alytic activity in epoxidation reaction of cis-diphenylethylene were studied using oxygen sources NaOCl.
The coordination compounds of Cu(II), Pt(II) and Ni(II) having general formula [MLCl]Cl, [ML2l]Cl2 or
[ML]Cl2 with tetra coordinated geometry around metal ions have been isolated as solid. All the ligands
and complexes were identified by spectroscopic methods and elemental analysis, magnetic measure-
ments, electrical conductance and thermal analysis. A square planer structures have been proposed for
all complexes. The thermal stability of the complexes discussed in terms of ligands donor atoms, geom-
etry and central metal ions. The complexes have a similar thermal behavior for the selected metal ions.
The thermogravimetric analyses suggest high thermal stability for most complexes followed by thermal
decomposition in different steps. The decomposition processes were observed as water elimination, chlo-
ride anion removal and degradation of the organic ligands. Catalytic ability of the complexes were exam-
ined and found that all the complexes can effectively catalyze the epoxidation of cis-stilbene with NaOCl.
Ó 2013 Elsevier B.V. All rights reserved.
Received 14 August 2013
Accepted 6 September 2013
Available online 16 September 2013
Keywords:
N-substituted piperazine
Morpholine
Thiomorpholine
Thermal stability
Complexes
Catalytic activity
Introduction
piperazine with an acetamide pendant group are known to be as
tridentate chelates. Nitrogen, oxygen and sulfur-containing
The chelate ligands that contain mixed donor groups compris-
ing morpholines, thiomorpholines, and symmetric donor pipera-
zines are some of the most important pharmacophores in
medicinal chemistry [1–3]. Morpholine, thiomorpholine and
heterocyclic frameworks are prevalent subunits in biologically ac-
tive molecules [4–6] in a variety of biologically active structures
such as the antidepressant drug [7] and the antifungal compounds
[8]. Similarly, the piperazine moiety is present in various
biologically active compounds including the antimicrobial [9]
and related quinolones, dopaminergic D3 agents [10], HIV-protease
inhibitors [11] and the antidepressants [12]. Piperazine derivatives
⇑
Corresponding author. Tel.: +61 2 42213555.
E-mail address: yakupbaran@yahoo.com (Y. Baran).
1386-1425/$ - see front matter Ó 2013 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.saa.2013.09.031

M. Kacan et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 118 (2014) 572–577
573
were extensively investigated and used as drugs in the field of
General syntheses of the ligands
medicinal sciences, and actively investigated in antibacterial, anti-
fungal and anti-cancer aspects. The structure of bis-pendant piper-
azine was published recently [13]. Thiomorpholine analogs are
associated with a variety of pharmacological activities including
anti mycobacterial [14], antibacterial [15], analgesic [16] and
anti-inflammatory [17]. Metal complexes of these compounds have
been reported to act as efficient catalyst for the epoxidation of al-
kenes. Coordination compounds catalyze the transfer of oxygen
atoms to organic substrates which are important in the develop-
ment of efficient catalyst in organic synthesis in laboratory and
industry. This fact has opened up of new channel in the field of
homogeneous catalysis [18–25]. Epoxidation of alkenes is one of
the most used methods in organic synthesis. Epoxides can easily
be transformed into a large variety of compounds via ring opening
reactions to give diols, amino alcohols, allylic alcohols and ketones
[26]. These reactions are important process in commercial poly-
mers like polyurethane, polyamide, epoxy resins, and polyesters.
Direct oxygen transfer to the alkene is the most common method
of epoxide synthesis. Epoxidation reactions of alkenes can be
achieved by a variety of oxidants [27]; NaOCl was used in epoxida-
tion of cis-diphenylethylene. A major breakthrough in this field
was the discovery by Jacobsen and co-workers [28]. Catalytic al-
kene epoxidation with mononuclear nickel complexes have been
developed [29]. The complexes of N-substituted morpholine, thi-
omorpholine and piperazine are of particular interest not only for
their ability to form complexes but also high thermodynamic sta-
bility and kinetic inertness. The thermal behavior of the complexes
with acetamide pendant derivatives of piperazine, morpholine and
thiomorpholine have attracted attention in the last years, this
attention being focused on the species that could have some prac-
tical applications. Here we describe the synthesis, characterization,
thermal behaviors and catalytic activity in alkene epoxidation of
some metal complexes. The details of synthetic, spectral, magnetic
and thermal behaviors of these compounds are described.
2,20-piperazine-1,4-diyldiacetamide, L1
(0.86 g, 10 mmol) piperazine was dissolved in THF and (2.76 g,
20 mmol) potassium carbonate was added and mixture was stirred
at room temperature for 20 min and then (2.90 g, 21 mmol) 2-
bromoacetamine was added. The mixture was stirred for 15 h
and the completion of the reaction was monitored by TLC analysis
and upon the completion, the solid was filtered with sintered glass
funnel. The filtrate was evaporated by rotary evaporator and the
residue was dried in vacuum desiccator. The best yields of the de-
sired products were obtained when the reaction was carried out in
THF at room temperature with a 1:2 mole ratio of the reagents.
Formation of HBr is eliminated with subsequent treatment of this
salt with saturated aqueous sodium carbonate. The white crystals
were obtained. The compound was characterized using different
spectroscopic techniques, including IR, NMR and MS, elemental
analyses. Reaction scheme is given in Scheme 1.
Yield: 77%, 1.6 g. Anal. calcd. for C8H16N4O2, (200.24 g/mol): C
47.99%; H 8.05%; N 27.98%. Found: C 47.83%; H 8.14%; N 27.82%.
FT-IR (KBr, cmꢁ1): 1675
m(C = 0, amide), 3323, 3213, 3146
m
(NAH). 1H NMR (d, ppm, CD3OD): 7.33 (NH2, s, 4H), 3.91(s, CH2AN,
4H), 3.50–3.60 (d t, piperazine ring, 8H), 13C NMR (d, ppm, CDCl3):
167.89 (C@O), 56.79 (CH2AN, 2C), and 49.74 (piperazine ring, 4C).
GS MS (EI, m/z): [M] +, 200.99.
_
2-morpholin-4-ylacetamide, L2
Yield: (73%) 2.11 g. Anal.calcd. for C6H12N2 O2 (144.17): C
49.98%; H 8.39%; N 19.43%. Found: C 49.81%; H 8.27%; N 19.34%.
IR (KBr, cmꢁ1): 1695 (C@O), 3369, 3154
m
(NAH) 1H NMR (d,
ppm, CD3OD): 7.32 (s, NH2), 3.95–4.45 (t, OACH2, 4H), 3.89 (s,
NACH2, 2H), 3.28–3.80 (t, NACH2 ring, 4H). 13C NMR (d, ppm,
CD3OD): 166.87 (C@O), 64.05 (OACH2, 2C), 57.37 (NACH2), and
52.78 (NACH2 ring, 2C). MS (m/z, EI): [M] +, 145.05.
_
2-thiomorpholin-4-ylacetamide, L3
Experimental
Yield: 58%, 1.85 g. Anal. calcd. for C6H12N2OS (160.24): C
44.97%; H 7.55%; N 17.48%. Found: C 45.11%; H 7.59%; N 17.37%.
Materials
FT-IR (KBr, cmꢁ1): 1686
m
(C@O). 1H NMR (d, ppm, CD3OD): 7.92
(s, NH2), 3.02 (s, NACH2, 2H), 2.79 (t, NACH2, 4H), 2.72 (t, SACH2
The high purity reagents were obtained commercially and used
as received without further purification. Spectroscopic grade and
argon saturated methanol was used for the syntheses of the
compounds.
ring, 4H). 13C NMR (d, ppm, CDCl3): 167.97 (C@O), 61.54 (NACH2),
+
_
55.25 (NACH2 ring, 2C), 27.40 SACH2 ring, 2C). MS (EI, m/z): [M] ,
161.97.
2.4 General synthesis of the complexes
Physical measurements
All the complexes of acetamide pendant piperazine, morpholine
and thiomorpholine with Pt(II), Ni(II) and Cu(II) were prepared by
following general method. The metal salt (10 mmol) was dissolved
in 40 mL argon saturated methanol and the solution was added to a
stirred solution of ligands (11 mmol) in 30 mL methanol solution
at room temperature. On addition of metal to ligand solution
immediate color change was observed according to the metal ions.
Then the solution was warmed up to 40 °C and stirred for 8 h and
then solution was concentrated on rotary evaporator. Solutions
were left for crystallization but amorphous powders were obtained
and dried at vacuum oven at room temperature. The proposed
structures of the complexes and ligands are given in Fig. 1.
IR spectra (KBr disks, 4000–400 cmꢁ1) were recorded using a
Perkin Elmer BXII spectrometer. 1H (300.0 MHz) and 13C NMR
spectra were recorded on a Varian NMR spectrometers. Chemical
shifts are referred to the detoured solvent chemical shift. Mass
spectra were acquired with GC–MS in Electron impact mode with
a Thermo Finnigan Trace DSQ. Molar conductance was measured
using a WTW inolab cond 720 conductivity meter where the cell
constant was calibrated with 0.001 M KCl solution, and nitrometh-
ane was used as solvents. Thermal studies were made with a Seiko
SII TG-DTA 6300 TG/DTA analyzer heated from 20 to 1200 °C under
dry air. The end products in thermogravimetric study were ana-
lyzed by a Bruker D2 Phaser XRD. UV–vis spectra were recorded
at 25 °C in aqueous solution on an Agilent 4583 diode array spec-
trometer. Solid-state magnetic susceptibility data were collected
on a powdered microcrystalline sample using a Sherwood Scien-
tific Magnetic Susceptibility Balance at room temperature. Elemen-
tal analysis for C, H and N were determined on dried samples using
a Perkin–Elmer 2400 CHN analyzer.
Ni-L1
Yield: 63%. FTIR (KBr cmꢁ1): 3270, 3174, 1663, 459 (MAN). UV–
vis (H2O nm; (e
, Mꢁ1 cmꢁ1)): 310(1466), 425(566), 490(510). Anal.
calcd. for C8H18N4O3Cl2Ni (Fw: 347.85): C 27.62, H 5.22, N 16.11.
Found: C 27.51, H 5.14, N 16.25.

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M. Kacan et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 118 (2014) 572–577
O
O
O
NH2
O
K2CO3
NH2
O
N
N
N
H2N
2HBr
N
+
H2N
HN
2
NH
NH2
Br
Scheme 1. Reaction scheme of the piperazine derivative.
Anal. calcd. for C12H28N4O6Cl2Cu (Fw: 458.83): C 31.41, H 6.15, N
12.21. Found: C 31.22, H 6.18, N 12.32. Paramagnetic with 1.81 BM.
O
O
N
N
H2 N
N
S
PtL2
H2 N
N
O
Yield: 61%. FTIR (KBr cmꢁ1): 3384, 3183, 1691, 576 (MAO), 472
NH2
H2 N
O
(MAN). UV–vis (H2O. nm; (e
, Mꢁ1 cmꢁ1)): 443(1020). Anal. calcd.
for C12H24N4O4Cl2Pt (Fw: 554.33): C 26.00, H 4.36, N 10.11. Found:
C 26.10, H 4.28, N 10.27.
O
L1
L2
L3
Ni-L3
O
Yield: 66%. FTIR (KBr cmꢁ1): 3399, 1568, 1418, 433 (MAN). UV–
O
vis (H2O nm; (e
, Mꢁ1 cmꢁ1)): 290(1277), 344(388), 466(371). Anal.
calcd. for C6H14O2Cl2N2NiS (Fw: 307.86): C 23.41, H 4.58, N 9.10.
Found: C 23.28, H 4.27, N 9.15.
NH
N
O
O
N
2
H
H
N
N
N
N
S
N
Pt
Pt
H N
2
Pt
N
H
O
O
H
H
H
Cl
O
Cu-L3
Yield: 79%. FTIR (KBr cmꢁ1): 3390, 3123, 1672, 446 (MAN). UV–
PtL1
PtL2
PtL3
vis (H2O nm; (e
, Mꢁ1 cmꢁ1)): 320(1231), 540(377). Anal. calcd. for
C6H12N2O2Cl2CuS (Fw: 294.70): C 24.45, H 4.10, N 9.51. Found: C
O
24.31, H 4.32, N 9.26. Paramagnetic 1.79 BM
NH
N
O
O
2
H
H
N
N
N
N
N
S
N
Cu
Pt–L3
Cu
H N
2
Cu
N
Yield: 56%. FTIR (KBr cmꢁ1): 3398, 3179, 1684, 442 (MAN).
O
O
H
H
H
UV–vis (H2O nm; (e
, Mꢁ1 cmꢁ1)): 448(1322). Anal. calcd. for
Cl
H
O
C6H14N2O2Cl2PtS (Fw: 445.25): C 16.19, H 3.14, N 6.29. Found: C
16.27, H 3.23, N 6.11.
CuL1
CuL2
CuL3
O
O
Epoxidation of cis-1,2-diphenylethylene
H
H
H
H
N
N
N
N
N
S
N
The epoxidation reactions were carried out in in CH2Cl2 at
room temperature with constant stirring. The composition of
reaction medium was 2 mmol cis-1,2-diphenylethylene, 6 mmol
NaOCl, 0.040 mol complex in 10 mL of dichloromethane. The solu-
tion was buffered to pH: 11 using a NaH2PO4–NaOH buffer. The
mixture was stirred at room temperature for 7 h. For each com-
plex the reaction time for the maximum epoxide yield was deter-
mined by withdrawing small amount of aliquots from reaction
mixture. The disappearance of cis-1,2-diphenylethylene was
checked with TLC. After the conversion of cis-1,2-diphenylethyl-
ene to epoxide, the mixture was loaded to a short celite column
and the filtrate was extracted twice with CH2Cl2 dried over anhy-
drous Na2SO4 and filtered. Reactions were run at least in dupli-
cate. The solvent was removed and the substance was analyzed
for the epoxide in CDCl3 with NMR. For the NMR experiments
epoxides were prepared following the procedure described [30].
The cis-1,2-diphenylethylene oxide has a singlet for the aliphatic
proton at d 4.21 and trans-1,2-diphenylethylene oxide has a sin-
glet at d 3.83 ppm.
N
N
Ni
Ni
Ni
O
O
Cl
O
Cl
H
H
H
H
NiL1
NiL2
NiL3
Fig. 1. Proposed structures of the ligands and complexes. Counter ions and waters
are omitted.
Cu-L1
Yield: 66%. FTIR (KBr cmꢁ1): 3502, 3309, 1675, 429 (MAN). UV–
vis (H2O nm; (e
, Mꢁ1 cmꢁ1)): 357(1240), 540(520). Anal. calcd. for
C8H20N4O4Cl2Cu (Fw: 370.72): C 25.91, H 5.44, N 15.11. Found: C
25.85, H 5.33, N 15.24. Paramagentic with 1.88 BM.
PtL1
Yield: 63%. FTIR (KBr cmꢁ1): 3313, 3167, 1676, 438 (MAN).
UV–vis (H2O nm; (e
, Mꢁ1 cmꢁ1)): 430(1125). Anal. calcd. for
C6H20N4O4Cl2Pt (Fw: 502.25): C 19.13, H 4.01, N 11.16. Found: C
19.01, H 3.96, N 11.23.
Result and discussion
Ni-L2
Yield: 71%. FTIR (KBr cmꢁ1): 3477, 3148, 1668, 1418, 549
Infrared spectra
(MAO), 466 (MAN). UV–vis (H2O nm; (e
, Mꢁ1 cmꢁ1)): 375(1355),
450(488), 480(390). Anal. calcd. for C6H24O8N2Cl2Ni (Fw: 381.87):
C 18.87, H 6.33, N 7.34. Found: C 18.79, H 6.45, N 7.39.
A high intensity bands observed in ligand in between 3370 and
3100 cmꢁ1 are attributed to the
m
(NAH) vibration for the ligands
L1, L2 and L3. The frequencies in between 1695 and 1675 cmꢁ1
are due to
(C@O) of the ligands. The frequency 718 cmꢁ1 is due
to
(CASAC) of L3, 1085 cmꢁ1 is due to (CAOAC) of L2 and
1023–1010 cmꢁ1 due to
(CANAC) of all ligands. In the case of
Cu-L2
m
Yield: 78%. FTIR (KBr cmꢁ1): 3366, 1656, 1578, 528 (MAO), 416
t
t
(MAN). UV–vis (H2O nm; (
e
, Mꢁ1 cmꢁ1)): 355(1113), 556(396).
t

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575
Table 1
Thermal analysis data of the complexes.
Complex
Step
Onset/°C
Endset/°C
Leaving group
H2O
Mass loss/%
Exp.
Residue Exp. (Calc.)
Calc.
5.1
[NiL1] Cl2ꢃH2O
1
2
3
25
298
478
298
478
609
5.1
L1 + Cl2
2H2O
77.2
6.6
77.9
7.1
NiO 17.7(16.9)
PtO 35.3/38.7
CuO 15.3/17.1
NiO 16.1/15.4
PtO 34.6/35.2
[PtL1]Cl2ꢃ2H2O
[CuL1]Cl2ꢃ2H2O
[NiL2Cl]Clꢃ6H2O
1
2
3
25
229
367
229
367
580
L1 + Cl2
2H2O
58.7
9.6
54.4
9.7
1
2
3
25
198
315
198
315
588
L1 + Cl2
6H2O
75.1
28.8
73.1
28.0
1
2
3
25
140
394
140
394
619
L1 + Cl2
55.3
56.3
½PtL22ꢄCl2
1
2
3
25
302
556
302
556
974
L23 þ Cl2
2H2O
65.3
7.6
64.8
7.8
½CuL22lꢄCl2 ꢃ 2H2O
1
2
3
1
2
1
2
3
1
2
3
25
274
486
25
92
25
97
463
25
189
359
274
486
652
92
406
97
463
546
189
359
585
L2 + Cl2
H2O
80.3
6.1
73.3
2.0
78.3
5.9
75.1
4.1
CuO 12.1/13.8
NiO 20.4/19.1
[NiL3Cl]ClꢃH2O
[PtL3Cl]ClꢃH2O
L3 + Cl2
H2O
L3 + Cl2
53.4
77.5
52.1
78.4
PtO 46.1/44.4
CuO 22.9/21.5
[CuL3Cl]Cl
L3 + Cl2
Pt(II), Ni(II) and Cu(II) complexes we observed the following
changes. The NAH bands in the ligands shift up on complexation.
The small shift to lower frequencies of the CAOAC, CASAC,
CANAC bands affords evidence of the coordination of O, S and N
atom of the morpholine, thiomorpholine and piperazine. In addi-
tion the Pt(II), Ni(II) and Cu(II) complexes exhibit a broad band at
ca. 3400 cmꢁ1; which was attributed to the AOH stretching fre-
quencies of coordinated water molecule. In the far IR spectra of
the complexes, the non-ligand bands were observed at 450–
500 cmꢁ1 region assigned to MAN stretch [31]. Another bands in
far IR region around 530–560 cmꢁ1 were observed which are as-
signed to MAO stretch [32]. The important features of the infrared
spectra of all the complexes are the appearance of two weak bands
er wavelengths indicates a large crystal field splitting is consistent
with square planer geometry of Ni(II) complexes [34,35].
1H and 13C NMR spectra
The 1H and 13C NMR spectra of the ligands were recorded at
room temperature in CD3OD. All the protons and carbons in NMR
spectra found to be in their expected regions. The data are summa-
rized in the synthesis of ligands. All the ligands show characteristic
carbon peak for C@O at 167.89, for L1, 166.87 for L2 and 167.97 for
L3 in 13C NMR
Molar conductance
at 536–554 cmꢁ1 region are assignable
m(MAO) and those in the
(MAN) vibrations, respectively. Thus,
region 462–499 cmꢁ1 to
m
The complexes of Cu(II), Ni(II) and Pt(II) were dissolved in nitro-
methane and the molar conductivities of 10ꢁ3 M of their solutions
at 25 2 °C were measured. It is concluded from the results that all
the complexes are considered 1:1 or 1:2 electrolytes with the mo-
the IR spectral results provide strong evidence for the complexa-
tion of the potentially tri and tetradentate ligands.
lar conductance values in between 73 and 112
cating the ionic nature of these complexes.
X
ꢁ1 molꢁ1 cm2 indi-
Electronic spectra
Electronic spectra of the complexes show high intensity band,
d–pꢂ Metal-Ligand Charge Transfer (MLCT) transitions were ob-
served in the region 320–375 nm. The third expected low-energy
ligand field bands observed in between 430 and 646 nm range
and are assigned as d–d transitions. The Ni(II) complexes are dia-
magnetic and the bands around 362–375 nm could be consistent
with low spin square-planar geometry. Pt(II) complexes are all four
coordinated; therefore square planer geometry around the metal is
expected. Cu(II) complexes show d–pꢂ metal-ligand charge transfer
(MLCT) transitions in the region 320–355 nm. A broad band around
540 nm which are attributed to 2B1g ? 2A1g transition strongly fa-
vors the square planer geometry around metal ion [33]. The elec-
tronic spectra show that absorption bands in Ni(II) complexes
observed below 550 nm. A lack of any electronic transition at long-
Thermal analysis
The molecular composition of the complexes has been verified
by thermogravimetric analyses. Thermal analysis data show that
some complexes follow similar type of decomposition pattern con-
firming their similar formulation. Complexes start losing water
first up to 200 °C and then ligands decompose in several steps.
Thermal stabilities increase as PtL2 > NiL2 > CuL2 but with the
different ligands this sequence will changes such as CuL1 > NiL1 >
CuL1 and CuL3 > PtL3 > NiL3. Complexes with L3 ligands much more
stable than L1 and L3 ligand complexes. The thermal behavior of the
PtL2complex is discussed as an example. Thermal analysis data of
the complexes are summarized in Table 1. The TG curves show
mainly three stages in the decomposition process. The first stage

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M. Kacan et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 118 (2014) 572–577
100.0
70
100.0
50.0
1.500
1.000
0.500
0.000
2
1
NiL
NiL
80.0
60
60.0
50
0.0
3
NiL
40.0
40
-50.0
-100.0
20.0
30
20
10
0
0.0
200 400 600 800 1000 1200
Temp Cel
Fig. 2. The TG–DTG–DTA curves of the NiL1 complex.
0
1
2
3
4
5
6
7
8
Time (h)
Fig. 5. The effect of time on epoxidation of cis-1,2-diphenylethylene using Ni(II)
complexes.
result of the thermal study, qualitative conclusion can be done
for the stability of the complexes. PtL2 complex is the most stable
one and NiL3 complex is the least stable one. The group TG, labeled
mass loss and TG–DTG–DTA curves of the complexes are given in
Figs. 2–4.
Magnetic susceptibility measurements
The measurement of the magnetic moment of a coordination
compounds containing unpaired electron spin is useful in the
establishment of the valency of the metal atom, and in many cases
also helps to determine the geometrical structure of the complex.
The magnetic susceptibilities of the solid-state complexes under
discussion were measured by the Gouy balance method. The mag-
netic moments of Ni(II) and Pt(II) complexes were measured at
room temperature and were found in the range 0.15–0.33 BM, con-
sistent with no unpaired electrons in the nickel(II) ion. The mag-
netic moment of copper complexes is in the range 1.79–1.88 BM.
Fig. 3. The labeled mass loss of the PtL2 complex.
Effect of time on the epoxidation of cis-1,2-diphenylethylene
The epoxidation of cis-1,2-diphenylethylene was carried out at
various times starting from 1 h up to 10 h at 25 °C. There is a gen-
eral trend of increasing conversion of cis-1,2-diphenylethylene
with increasing reaction time up to 7 h. After 7 h, the conversion
of epoxide does not change appreciably. The conversion of cis-
1,2-diphenylethylene as a function of time at 25 °C with different
catalyst was given in Fig. 5. The effect of the temperature on epox-
idation reaction was also studied. There is a gentle increase in con-
version of cis-1,2-diphenylethylene with increase in temperature
over room temperature. Blank experiments were carried out in
each case using the same experimental conditions without the cat-
alyst; no epoxide was formed under the same condition.
Fig. 4. TG curves of L2 complexes.
decomposition temperature is in the range of 25–302 °C, with a
mass loss of 30%, is probably attributed to the decomposition of
a group in the ligand. The second stage of decomposition was ob-
served in the 302–556 °C range and the third stage decompositions
take places in between 556 and 974 °C a with a mass loss of 12%
and 23.3%. Total mass loss is 65.3% (calculated 64.8%). The final
product is the PtO (34.6%, calcd.35.20%). These results are in good
agreement with the composition of the complexes. All thermal
events are exothermic process in dry air atmosphere. The thermo-
gravimetric analyses reveal greater thermal stability of the L2(N2O
donor set) complexes over the L1 and L3 complexes. It is confirmed
that most of the complexes contain water in the structure. As a
Epoxidation
Nine Ni(II), Cu(II) and Pt(II) complexes bearing N-substituted
piperazine, morpholine and thiomorpholine in square planer
coordination were tested as catalyst for cis-diphenylethylene
epoxidation. In the presence of complex, NaOCl reacts with cis-
1,2-diphenylethylene to produce trans and cis-epoxides. With
[NiL1Cl]Cl epoxides were produced in 53% yield with cis:
trans = 25:75, and with [NiL2]Cl2, epoxides were produced in 51%
yield with cis: trans = 18:82 and with [NiL3Cl]Cl is 39% yield with

M. Kacan et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 118 (2014) 572–577
577
Table 2
Cis-stilbene epoxidation with NaOCl catalyzed by complexes in CH2Cl2.
Appendix A. Supplementary material
Catalysts
Time/h
Tot. conversion (%)a
Epoxide Yield (%)b
Supplementary data associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.saa.2013.09.031.
[NiL1]Cl2ꢃH2O
[PtL1]Cl2ꢃ2H2O
[CuL1]Cl2ꢃ2H2O
[NiL2Cl]Clꢃ6H2O
6
7
7
6.5
6
58
48
53
66
54
53
44
46
51
48
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Acknowledgement
We thank the Trakya University TBAP 2010-113 for the finan-
cial support.