Epoxidation of cyclooctene by host (nanocavity of zeolite-Y) guest (copper(II) complexes with 16- and 17-membered diaza dioxa macrocyclic Schiff bases) nanocomposite materials

Article abstract of DOI:10.1080/00958972.2013.798655

This work reports the synthesis and characterization of macrocyclic copper(II) complexes encapsulated within the nanopores of zeolite-Y. The obtained nanoparticles entrapped in the nanopores of zeolite have been characterized by FT-IR, UV-Vis, Diffuse reflectance spectra, spectroscopic techniques, molar conductance, magnetic moment data, XRD, thermal, and elemental analysis. The complexes (neat and encapsulated) were used for the oxidation of cyclooctene with tert-butyl hydroperoxide as oxidant in different solvents. The supported Cu[L1]2+-Y exhibited a moderate 81.9% selectivity for epoxidation with 84.2% conversion. The catalytic activity and selectivity of the heterogeneous catalysts do not change after recycling five times.

Full text of DOI:10.1080/00958972.2013.798655

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Epoxidation of cyclooctene by host
(nanocavity of zeolite-Y) guest
(copper(II) complexes with 16- and 17-
membered diaza dioxa macrocyclic
Schiff bases) nanocomposite materials
Alireza Banaei a & Behnam Rezazadeh a
a Department of Chemistry , Payame Noor University , Tehran ,
Iran
Accepted author version posted online: 22 Apr 2013.Published
online: 30 May 2013.
To cite this article: Alireza Banaei & Behnam Rezazadeh (2013): Epoxidation of cyclooctene by
host (nanocavity of zeolite-Y) guest (copper(II) complexes with 16- and 17-membered diaza dioxa
macrocyclic Schiff bases) nanocomposite materials, Journal of Coordination Chemistry, 66:12,
2129-2140
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Journal of Coordination Chemistry, 2013
http://dx.doi.org/10.1080/00958972.2013.798655
Epoxidation of cyclooctene by host (nanocavity of zeolite-Y)
guest (copper(II) complexes with 16- and 17-membered diaza
dioxa macrocyclic Schiff bases) nanocomposite materials
ALIREZA BANAEI* and BEHNAM REZAZADEH
Department of Chemistry, Payame Noor University, Tehran, Iran
(Received 14 November 2012; in final form 18 February 2013)
This work reports the synthesis and characterization of macrocyclic copper(II) complexes encapsu-
lated within the nanopores of zeolite-Y. The obtained nanoparticles entrapped in the nanopores of
zeolite have been characterized by FT-IR, UV–Vis, Diffuse reflectance spectra, spectroscopic
techniques, molar conductance, magnetic moment data, XRD, thermal, and elemental analysis. The
complexes (neat and encapsulated) were used for the oxidation of cyclooctene with tert-butyl
hydroperoxide as oxidant in different solvents. The supported Cu[L1]2+-Y exhibited a moderate
81.9% selectivity for epoxidation with 84.2% conversion. The catalytic activity and selectivity of
the heterogeneous catalysts do not change after recycling five times.
Keywords: Nanoporous material; Epoxidation of cyclooctene; Copper(II); Schiff base; Macrocycle
1. Introduction
Epoxides are among the most widely used intermediates in organic synthesis, pharmaceuti-
cals as well as polymer production, acting as precursors for complex molecules due to the
strained oxirane ring [1], providing detergents, surfactants, antistatic agents, corrosion
protection agents, textiles, lubricating oils, and cosmetics [2]. Thus, epoxidation is an
important transformation undergone by alkenes. The use of transition metal complexes as
catalysts for this reaction has been the subject of interest [3], oxidation being carried out
by using oxidants, such as oxygen, hydrogen peroxide, and tert-butyl hydroperoxide
(TBHP) [4].
Heterogenization of homogeneous catalysts onto solid supports has been studied because
of the long catalytic lifetime, easy separation, thermal stability, high selectivity, and easy
recyclability [5, 6]. Many different solid catalysts such as metal oxides [7], zeolites [8],
and aluminophosphates [9] can be used to heterogenize homogeneous catalysts. Mixed
metal exchanged zeolite, ion exchange resins [10], and polymerized complexes [11] have
been used in liquid phase epoxidation of olefins [12]. Recent trends in immobilization of
catalyst complexes on clay-based materials such as montmorillonite, zeolites, and bentonite
heterogenize homogeneous catalysts [13, 14]. Encapsulation of transition metal complexes
in nanopores of zeolite has potential as biomimetic heterogeneous catalysts for oxidation
[15, 16].
*Corresponding author. Email: banaei@pnu.ac.ir
Ó 2013 Taylor & Francis

2130
A. Banaei and B. Rezazadeh
OH
Br
L'
Br
O
O
CHO
O
O
H
H
1)
2)
Cu(ClO4)2 . 6H2O
R
Comlexes
R
NH2
NH2
CuL1(ClO4)2
CuL1(ClO4)2
O
O
CuL1(ClO4)2
Cu2+
(ClO4)2.H2O
N
N
R
Scheme 1. Preparation of CuL1(ClO4)2, CuL2(ClO4)2 and CuL3(ClO4)2.
In this article, we report the synthesis and characterization of copper(II) complexes of 16-
and 17-membered diaza dioxa macrocycles [L1]; 3,4,11,12-dibenzo-1,14-diaza-5,10-dioxa
cyclohexadecane-1,13-diene, [L2]; 3,4,11,12-dibenzo-1,14-diaza-5,10-dioxacycloheptade-
cane-1,13-diene, and [L3]; 3,4,11,12,15,16,17-tribenzo-1,14-diaza,5,10-dioxa cycloheptade-
cane-1,13-diene; encapsulated within the nanopores of zeolite-Y by template condensation
of diamine and 1,4-bis(2-carboxyaldehydephenoxy)butane [L′]; Cu[L1]2+-Y, Cu[L2]2+-Y and
Cu[L3]2+-Y, shown in schemes 1 and 2, and used in the epoxidation of cyclooctene with
TBHP as oxygen donor.
2. Experimental
2.1. Materials and physical measurements
All materials were of commercial grade with the highest purity and used as received.
Solvents used were purified using known procedures. 1,2-Ethylenediamine, 1,3-propanedi-
amine, and 1,3-benzenediamine were purchased from Merck. Cyclooctene and cyclooctene
epoxide were purchased from Aldrich chemical company. Na-Y with Si : Al ratio of 2.53
was purchased from Aldrich (Lot No. 67812).
FT-IR spectra were recorded on a Shimadzu Varian 4300 Spectrophotometer in KBr
pellets. Electronic spectra of the neat complexes were taken on a Shimadzu UV–Vis
scanning spectrometer (Model 1601 PC). Diffuse reflectance spectra (DRS) were recorded
on a Scinco 4100 from 200–1100 nm using 6890 series. Elemental analyses (carbon,
hydrogen and nitrogen) of the materials were obtained from a Carlo ERBA model EA 1108
analyzer. XRD patterns were recorded by a Rigaku D-Max C III, X-ray diffractometer using

Epoxidation of cyclooctene
2131
Scheme 2. Encapsulation of copper(II) complex nanoparticles of 16- and 17-membered diaza dioxa Schiff base
within nanopores of zeolite-Y.
Ni-filtered Cu Kα radiation. The metal contents were measured by an atomic absorption
spectrophotometer (AAS-Perkin–Elmer 4100-1319) using
a flame approach. After
completely destroying the zeolitic framework with hot and concentrated HCl, sodium, alumi-
num, and copper were analyzed by AAS and SiO2 was determined by gravimetric analysis.
The products were analyzed by GC and GC-Mass spectra using a 6890 series, FID
detector, HP-5% 5-phenyl siloxane and Agilent 5973 network, mass selective detector, HP,
5MS 6890 network GC system.
2.2. Synthesis of 1,4-bis(2-carboxyaldehydephenoxy)butane [L′]
To a stirred solution of salicylaldehyde (6.6 g, 50 mM) and K2CO3 (12.2 g, 100 mM) in
DMF (60 mL) was added dropwise 1,4-dibromobutane (10.8 g, 50 mM) in DMF (20 mL).
The reaction was continued for 10 h at 150 °C and then for 5 h at room temperature. Then,
150 mL of distilled water was added and the mixture was put in the refrigerator. One hour
later the precipitate was filtered and washed with 300 mL of water, dried in air, recrystallized
from ethanol, and dried in vacuum. Yield: 11.3 g (76%), m.p: 105 °C, Color: bright brown.
IR (KBr, ν cmÀ1): 1677 ν(C = O), 1488, 1462 ν(Ar–C = C), 1285, 12.3 ν(Ar–O), 1170, 1040
ν(R–O). Anal. Calcd for C18H18O4: C, 72.54; H, 6.06. Found: C, 72.62; H, 6.15.

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A. Banaei and B. Rezazadeh
2.3. Preparation of CuL1(ClO4)2, CuL2(ClO4)2 and CuL3(ClO4)2
To a stirred solution of L′ [1,4-bis(2-carboxyaldehydephenoxy)butane] (3.6 g, 12 mM) and
Cu(ClO4)2·6H2O (4.44 g, 12 mM) in methanol (100 mL), various diamines (12 mM) in
methanol (60 mL) were added dropwise. After the addition was completed the stirring was
continued for another 2 h. Then the precipitate was filtered, washed with methanol, and
dried in air. The products were crystallized from methanol.
2.3.1. CuL1(ClO4)2·H2O. Anal. Calcd for C20H24O11Cl2N2Cu: C, 39.96; H, 3.74; N, 4.52;
Cu, 10.67; C/N, 8.84. Found: C, 39.83; H, 3.65; N, 4.64; Cu, 10.54; C/N, 8.58. IR (KBr,
ν cmÀ1): 1616 [νC = N], ΛM = 160 ΩÀ1 cm2 MÀ1 (in DMF), UV–Vis (λmax nm) (in DMF): 225,
264, 312, 550, μeff = 1.91BM.
2.3.2. CuL2(ClO4)2·H2O. Anal. Calcd for C21H26O11Cl2N2Cu: C, 40.96; H, 4.35; N,
4.64; Cu, 10.43; C/N, 9.20. Found: C, 40.87; H, 4.22; N, 4.54; Cu, 10.43; C/N, 9. IR
(KBr, ν cmÀ1): 1617 [νC = N], ΛM = 167 ΩÀ1 cm2 MÀ1 (in DMF), UV–Vis (λmax nm)
(DMF): 235, 270, 309, 643, μeff = 1.71 BM.
2.3.3. CuL3(ClO4)2·H2O. Anal. Calcd for C24H24O11Cl2N2Cu: C, 44.25; H, 4.07; N,
4.14; Cu, 9.85; C/N, 10.68. Found: C, 44.14; H, 3.98; N, 4.29; Cu, 9.73; C/N, 10.28. IR
(KBr, ν cmÀ1): 1616 [νC = N], ΛM = 161 ΩÀ1 cm2 MÀ1 (in DMF), UV–Vis (λmax nm)
(DMF): 221, 271, 344, 458, μeff = 1.73 BM.
2.4. Preparation of Cu(II)-Y
About 5 g of Na-Y zeolite was suspended in 300 mL of distilled water which contained
Cu(ClO4)2·6H2O (6.93 g, 18.75 mM). The mixture was then heated while stirring at 90 °C
for 24 h. The solid was then filtered, washed with hot distilled water till the filtrate was
free from any copper(II) ion (by AAS of filtrate) content, and dried for 10 h at 80 °C
under vacuum. The ionic exchange degree was determined by an atomic absorption
spectrophotometer.
2.4.1. Na-Y. Anal. Found: Si, 21.58; Al, 8.64; Na, 7.45; Si/Al, 2.53.
2.4.2. Cu(II)-Y. Anal. Found: Si, 21.56; Al, 8.52; Na, 4.42; Cu, 4.36; Si/Al, 2.53.
2.5. Preparation of CuL′-Y
Typically 10 g of Cu(II)-Y zeolite was mixed with 4 g of L′ suspended in 200 mL of
methanol and then refluxed for 8 h. The solid consisting of L′ coordinated with Cu(II) in
Cu(II)-Y and denoted as [CuL′]2+-Y was collected by filtration and washed with methanol.
The solid was Soxhlet extracted with chloroform (for 4 h) and then with ethanol (for 4 h).
The resulting solids were dried at 100 °C under vacuum for 24 h.

Epoxidation of cyclooctene
2133
2.6. Preparation of [CuL1]2+-Y, [CuL2]2+-Y and [CuL3]2+-Y
To a stirred methanol suspension (200 mL) of [CuL′]2+-Y (4 g) was slowly added diamine,
1,2-diaminobutane, 1,3-diaminopropane or 1,3-diaminobenzene (under N2). The mixture
was heated under reflux for 24 h, filtered, and the resulting zeolite-Y Soxhlet extracted
with chloroform (for 4 h) and then with ethanol (for 4 h). The resulting solids were dried
at 70 °C under vacuum for 12 h. The remaining [CuL′]2+ ions in zeolite-Y were removed
by exchanging with aqueous 0.01 M NaCl solution.
2.6.1. [CuL1]2+-Y. Anal. Found: C: 11.29, H: 1.26, N: 1.30, C/N: 8.68. Si: 21.21, Al:
8.38, Na: 5.39, Cu: 2.98, Si/Al: 2.53. IR (KBr, ν cmÀ1): 1617 [νC = N], DRS (λmax nm):
268, 318, 553.
2.6.2. [CuL2]2+-Y. Anal. Found: C: 11.73, H: 1.22, N: 1.27, C/N: 9.23. Si: 21.22, Al:
8.36, Na: 5.37, Cu: 2.94, Si/Al: 2.53. IR (KBr, ν cmÀ1): 1618 [νC = N], DRS (λmax nm):
265, 305, 633.
2.6.3. [CuL3]2+-Y. Anal. Found: C: 13.39, H: 1.16, N: 1.28, C/N: 10.46. Si: 21.19, Al:
8.37, Na: 5.31, Cu: 2.92, Si/Al: 2.53. IR (KBr, ν cmÀ1): 1617 [νC = N], DRS (λmax nm):
267, 337, 454.
2.7. General procedure for catalytic epoxidation of cyclooctene
A mixture of 5 Â 10À2 mM of catalyst and 20 mM cyclooctene in 5 mL CH3CN was stirred
under nitrogen reflux for 30 min. Then 24 mM of TBHP was added and the mixture was
refluxed for 4 h. The products were identified by GC–MS. After filtration (heterogeneous
catalysts) the solid was washed with acetonitrile. The filtrate was then injected to GC anal-
ysis. Internal standard 1,2-dichlorobenzene was used for cyclooctene.
3. Results and discussion
3.1. Synthesis and characterization of neat complexes
Reaction between 1,4-bis(2-carboxyaldehydephenoxy)butane, copper(II) perchlorate, and
amines in methanol gives the [1 + 1] macrocycle Schiff-base complexes as the major
product. The macrocyclic complexes were characterized by elemental analysis, UV, and IR
spectrometry. The molecular formulas of the complexes are assigned on the basis of
elemental analyses.
A strong band in the IR spectra of the Cu(II) metal complexes at 1616 cmÀ1 is attributed
to (C = N) stretch, indicating coordination of the azomethine nitrogen to copper [17]. Broad
bands at 3350 cmÀ1 for all complexes can be attributed to stretching vibrations of water
[18]. A new band at ꢀ1200 cmÀ1 was assigned to (R–O) [19]. Conclusive evidence of the
bonding is also shown by new bands in IR spectra of the Cu(II) metal complexes at 490
and 470 cmÀ1 assigned to (Cu–O) and (Cu–N) stretches [20]. Infrared spectra of the
copper(II) complexes exhibit an intense band between 1182 and 1110 cmÀ1 along with a

2134
A. Banaei and B. Rezazadeh
weak band between 651 and 625 cmÀ1 assigned to perchlorate complexes due to ν(Cl–O)
of uncoordinated perchlorate [21].
The metal/ligand mole ratio was 1 : 1, according to elemental analysis. Magnetic
moments of the Cu(II) complexes at room temperature range from 1.73–1.91 BM, typical
for mononuclear Cu(II) complexes with a S = 1/2 spin-state. The Cu(II) metal complexes
are in the ratio of 2 : 1 electrolytes as shown by their molar conductivities (ΛM) in DMF at
10À3 M, which are 160–167 ΩÀ1 cm2 MÀ1. The molar conductivities of the compounds in
DMF are in the range reported for 2 : 1 electrolytes [17] (scheme 1).
Electronic absorption spectra of all the complexes were recorded in DMF. The
absorption bands below 300 nm are identical and can be attributed to π→π⁄ transitions in
the benzene ring and azomethine. The absorption observed at ꢀ310 nm is probably due
to the π→π⁄ transitions of imines [22]. Electronic spectra also show absorption at
454–643 nm attributed to d–d transitions, characteristic for tetragonally elongated octahe-
dral or square planar geometry [23]. The energy of the band assigned to d–d transitions
provides a rough estimate of the ligand field strength.
3.2. Synthesis and characterization zeolite-Y encapsulated complexes
Copper(II) complex is encapsulated in the nanopores of zeolite-Y by the reaction of [Cu(L′)]2+-Y
with diamine (1,2-diaminoethane, 1,3-diaminopropane, 1,3-diaminobenzene). Soxhlet extraction
using ethanol and chloroform purified the impure complexes. The remaining uncomplexed metal
ions in zeolite-Y were removed by exchanging with aqueous 0.01 M NaCl solution. The parent
Na-Y zeolite has Si/Al molar ratio of 2.53 which corresponds to a unit cell formula
Na56[(AlO2)56(SiO2)136]. Initial metal loading in the zeolite lattice is 4.36%, whereas the metal
contents are considerably lower in zeolite-Y complexes. This decrease in metal content is
attributed to the formation of complexes inside the cavities. CHN analyses of the neat copper
complexes are similar to theoretical values. Copper contents of the zeolite-Y encapsulated
samples were estimated by dissolving known amounts of the catalyst in concentrated HCl and
using AAS. The analytical data of each complex indicate molar ratios of Cu : C : H, close to those
calculated for the mononuclear structure.
The IR spectrum of encapsulated complexes show major bands at 2980 cmÀ1 and
1616 cmÀ1 which are absent in the zeolite-Y. IR bands of all encapsulated complex
nanoparticles were weak due to their low concentration in zeolite-Y. Cu(II) complex
nanoparticles encapsulated in the zeolite cages did not show any significant shift in C = N
stretch. We did not notice any appreciable changes in the frequencies of copper(II)
complexes after incorporation into zeolite matrix. A comparison of the FT-IR spectra of
the encapsulated complex with that of the neat complex indicates the presence of the
complex inside the zeolite-Y cage (figure 1).
Comparison of the electronic spectral data of the encapsulated complexes in zeolite-Y
and neat complexes confirmed incorporation of Cu(II) complex into the zeolite-Y
supercages. The electronic spectral profiles of [CuL3]2+-Y and (CuL3)(ClO4)2·H2O are
reproduced in Supplemenatry material.
The X-ray diffraction (XRD) patterns of encapsulated complexes are shown in figure 2.
The encapsulated complex exhibits similar peaks to those of zeolite-Y, except for a slight
change in intensity of the peaks, no new crystalline pattern emerges, confirming that the
framework and crystallinity of zeolite were not destroyed during the preparation, and that
the complexes were well distributed in the cages. The relative peak intensities of the 220,
311, and 331 reflections correlate to the locations of cations. In zeolite-Y, the order of peak

Epoxidation of cyclooctene
2135
Figure 1. FT-IR spectra: (a) zeolite-Y, (b) (CuL1)(ClO4)2·H2O, (c) [CuL1]2+-Y, (d) (CuL2)(ClO4)2·H2O, (e)
[CuL2]2+-Y, (f) (CuL3)(ClO4)2·H2O, (g) [CuL3]2+-Y.

2136
A. Banaei and B. Rezazadeh
Figure 2. XRD patterns of (a) Na-Y, (b) Cu2+-Y, (c) [CuL1]2+-Y, (d) [CuL2]2+-Y, (e) [CuL3]2+-Y.
intensity is in the order: I331 > I220 > I311, while in encapsulated complexes, the order of peak
intensity became I331 > I311 > I220. The difference indicates that the ion-exchanged Cu2+,
which substitutes at the location of Na+, undergoes rearrangement during complexation.
The thermal stability of catalysts was studied by TGA; the TGA profile of [CuL3]2+-Y
is reproduced in Supplementary Material. The thermal decomposition of these materials
occurs in two steps. The endothermic loss in the first step starts above 140 °C and contin-
ues until the loss of all intrazeolite water. The exothermic loss in the two steps occurs in a
wide temperature range (450–800 °C) due to slow decomposition of the chelating ligand.
A very small weight percentage loss indicates the presence of only a small amount of
metal complex in the nanopores of zeolite-Y, in agreement with the low percentage of
metal content estimated by AAS. The thermal stability of the encapsulated complex is
confirmed.
3.3. Catalytic activity
Schiff base metal complex-catalyzed oxidation of organic compounds has been extensively
reported [24, 25]. Transition metal complex-based soluble catalysts are prone to deactiva-
tion by dimerization of active centers which is expected to be reduced by encapsulating
them in zeolites [26]. The most important advantage of heterogeneous catalysis over its
homogeneous counterpart is increase of complex stability in the reaction medium and the
possibility of reusing the catalyst after reaction by simple filtration [27].
The catalytic activities of neat and encapsulated complexes were evaluated for oxidation
of cyclooctene with TBHP. The major product of oxidation of cyclooctene is cyclooctane
epoxide. The selectivity and activity of zeolite-Y encapsulated and homogeneous catalysts
on the epoxidation of cyclooctene with TBHP are shown in table 1.

Epoxidation of cyclooctene
2137
Table 1. Epoxidation of cyclooctene with TBHP catalyzed by nanopores of zeolite encapsulated and neat copper
(II) complexes in CH3CN. Conditions: catalyst 0.05 mM, TBHP 24 mM, cyclooctene 20 mM, CH3CN 5 mL,
temperature 80 °C.
Selectivity (%)
O
O
OH
O
Bu
O
Catalyst
Time (h)
Conversion (%)
Cu(II)-Y
6
2
4
6
23.4
61.3
81.3
83
23.4
71.1
80.2
82.3
24.8
19.1
11.5
9.3
45.6
6.6
6.4
5.9
6.2
[Cu(L1)]2+-Y
[Cu(L1)]2+-Y
[Cu(L1)]2+-Y
2.2
1.9
2.5
[Cu(L1)]2+-Ya
[Cu(L1)]2+-Yb
[Cu(L1)]2+-Yc
8
8
8
84.2
83.7
84.1
81.9
82.5
81.3
9.5
9.4
9.9
6
5.7
6.1
2.6
2.4
2.7
[Cu(L2)]2+-Y
[Cu(L2)]2+-Y
[Cu(L2)]2+-Y
2
4
6
51.3
73.4
74.8
71.3
71.9
72.8
18.7
19.7
18.3
7.5
7.1
5.6
2.5
2.3
3.3
[Cu(L2)]2+-Ya
[Cu(L2)]2+-Yd
[Cu(L2)]2+-Yf
8
8
8
75.5
75
74.8
73.2
73.9
72.5
18.1
18.3
18.7
5.5
4.9
5.3
3.2
2.9
3.5
[Cu(L3)]2+-Y
[Cu(L3)]2+-Y
[Cu(L3)]2+-Y
2
4
6
53.7
68.9
71.2
63.1
65.3
68.8
29.2
27.6
22.1
5.6
4.8
6.1
2.1
2.3
3
[Cu(L3)]2+-Ya
[Cu(L3)]2+-Yc
[Cu(L3)]2+-Yf
8
8
8
72.3
72.1
71.8
69.7
70.3
69.5
21.7
21.4
21.4
5.8
5.2
5.6
2.8
3.1
3.5
CuL1(ClO4)2·H2O
CuL2(ClO4)2·H2O
CuL3(ClO4)2·H2O
4
4
4
70.8
59.9
56.6
70.2
64.7
61
23.2
27.4
28.7
4.2
5.3
7.1
2.4
2.6
3.2
c
f
aFirst reuse. bSecond reuse. Third reuse. dFourth reuse. Fifth reuse.
Comparing neat and encapsulated complexes shows that zeolite-Y encapsulated
catalysts gave higher conversion of cyclooctene than their corresponding neat com-
plexes. The higher activity of supported complexes is because of site isolation of the
complexes.
We examined reaction times of 2, 4, 6, and 8 h. The results are shown in table 1. At 4 h
maximum conversion takes place and longer times have no effect on reactivity. The obser-
vation of a plateau after 4 h is not unexpected because cyclooctene is depleted.
To investigate the role of solvent on the reaction and product distribution, we carried
out the reaction in protic and aprotic solvents. The results are given in tables 1–3.
Polar aprotic solvent such as acetonitrile is particularly efficient in providing both high
cyclooctene conversion and high-epoxide selectivity.
The zeolite-Y encapsulated complexes did not undergo any color change during the
reaction and could be separated and reused many times without major loss in activity. The
catalytic activity and selectivity of heterogeneous catalysts have not changed after five
times of reusing (figure 3 and table 1). In contrast, the neat complexes were completely
destroyed during the first run and changed color. Thus, the encapsulation of complexes in

2138
A. Banaei and B. Rezazadeh
Table 2. Epoxidation of cyclooctene with TBHP catalyzed by nanopores of zeolite encapsulated copper(II)
complexes in CH3OH. Conditions: catalyst 0.05 mM, TBHP 24 mM, cyclooctene 20 mM, CH3OH 5 mL,
temperature 80 °C.
Selectivity (%)
O
O
OH
O
Bu
O
Catalyst
Time (h)
Conversion (%)
[CuL1]2+-Y
[CuL2]2+-Y
[CuL3]2+-Y
4
4
4
70.5
63.2
61.5
65.8
56.3
55.2
26.9
36.6
38.9
3.9
4.2
3.5
3.4
2.8
2.4
Table 3. Epoxidation of cyclooctene with TBHP catalyzed by nanopores of zeolite encapsulated copper(II)
complexes in CH2Cl2. Conditions: catalyst 0.05 mM, TBHP 24 mM, cyclooctene 20 mM, CH3OH 5 mL,
temperature 80 °C.
Selectivity (%)
O
O
OH
O
Bu
O
Catalyst
Time (h)
Conversion (%)
[CuL1]2+-Y
[CuL2]2+-Y
[CuL3]2+-Y
4
4
4
55.3
53.8
50.2
62.4
55.8
50.8
20.4
27.9
34
12.5
11.2
9.3
4.7
5.1
5.9
Figure 3. The catalytic activity of the zeolite encapsulated copper (II) complexes in 5 runs of cyclooctene
epoxidation (catalyst 0.05 mM, TBHP 24 mM, cyclooctene 20 mM, CH3CN 5 mL, time 4 h, 80 °C).
zeolites increases the life of the catalyst by reducing dimerization due to the restriction of
internal framework structure.
Epoxidation of cyclooctene with TBHP over copper Schiff base catalysts under hetero-
geneous conditions has been studied. According to our results, expoxidation of cyclooctene
was carried out with 84.2% conversion and 81.9% selectivity (see table 1 and figure 4).

Epoxidation of cyclooctene
2139
Figure 4. Product selectivity for oxidation of cyclooctene catalyzed by heterogeneous Cu(II) complexes at
0.05 mM, TBHP 24 mM, cyclooctene 20 mM, CH3CN 5 mL, time 4 h, 80 °C.
As compared to the recently published system with Cu-salen immobilized on MCM-41
and MCM-48 giving 53–54% conversion of cyclooctene with 78–85% epoxide selectivity,
our system seems simpler, more economical, and more efficient [28].
4. Conclusion
Copper(II) complexes with 16- and 17-membered diaza dioxa Schiff base macrocyclic
ligands have been encapsulated in nanopores of zeolite-Y. The resulting catalysts have
been spectroscopically characterized (IR, DRS, UV–Vis), elemental analysis, etc. This
catalytic system showed high activity in epoxidation of cyclooctene under mild reaction
conditions. Encapsulated complexes can be recovered and reused without loss of catalytic
activity. As compared to the recently published system which worked with Mn-hydrazone
Schiff base immobilized on zeolite-Y, our system seems competitive [29].
Acknowledgment
The authors acknowledge the Payame Noor University of Ardabil for support of this work.
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