Metallo-hydrazone complexes immobilized in zeolite Y: Synthesis, identification and acid violet-1 degradation

Article abstract of DOI:10.1016/j.molstruc.2011.09.061

Copper(II), cobalt(II) and nickel(II) complexes of hydrazone ligand (SAPH) derived from salicylaldehyde and phenylhydrazine have been encapsulated in zeolite-Y super cages via ship-in-a-bottle synthesis. Detailed characterization of the intrazeolitic complexes were performed by elemental analysis, spectral (FT-IR, UV-Vis.) studies, magnetic measurements and X-ray diffraction. Furthers, surface texture and thermal analysis (TG, DTG, DTA) have provided further evidence for successful immobilization of the metal complexes inside zeolite Y. Investigation of the stereochemistry of these incorporated chelates pointed out that, SAPH ligand is capable to coordinate with the central metal through the (CN), phenolic (OH) and (NH) groups forming polynuclear structures. The involvement of zeolite oxygen in coordination was postulated in the hybrid materials. The intrazeolitic copper, cobalt and nickel-SAPH complexes have distorted tetrahedral, octahedral and square-pyramidal configurations, respectively. The zeolite encapsulated complexes are thermally stable up to 800 °C except Cu(II) sample which is thermally stable up to midpoint 428 °C. The assessment of the catalytic activity was performed by the use of the photo-degradation of acid violet-1 dye as a probe reaction in presence of H ₂O₂ as an oxidant. Decolorization of acid violet-1 dye was examined under the same conditions whereas the unpromoted zeolite and Cu ^II, Co^II, Ni^II-hydrazone complexes supported on zeolite showed 13% and 76%, 53%, 43% color removal, respectively. The results revealed that, the zeolite encapsulated Cu(II) complex generally exhibited better catalytic efficiency (76%) compared with other investigated zeolite encapsulated metal-hydrazone samples.

Full text of DOI:10.1016/j.molstruc.2011.09.061

Journal of Molecular Structure 1006 (2011) 527–535
Contents lists available at SciVerse ScienceDirect
Journal of Molecular Structure
journal homepage: www.elsevier.com/locate/molstruc
Metallo-hydrazone complexes immobilized in zeolite Y: Synthesis,
identification and acid violet-1 degradation
⇑
Ayman H. Ahmed , M.S. Thabet
Department of Chemistry, Faculty of Science, Al-Azhar University, Nasr City, Cairo, Egypt
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 15 May 2011
Received in revised form 27 September
Copper(II), cobalt(II) and nickel(II) complexes of hydrazone ligand (SAPH) derived from salicylaldehyde
and phenylhydrazine have been encapsulated in zeolite-Y super cages via ship-in-a-bottle synthesis.
Detailed characterization of the intrazeolitic complexes were performed by elemental analysis, spectral
2
011
(FT-IR, UV–Vis.) studies, magnetic measurements and X-ray diffraction. Furthers, surface texture and
Accepted 30 September 2011
Available online 8 October 2011
thermal analysis (TG, DTG, DTA) have provided further evidence for successful immobilization of the
metal complexes inside zeolite Y. Investigation of the stereochemistry of these incorporated chelates
pointed out that, SAPH ligand is capable to coordinate with the central metal through the (C@N), phenolic
Keywords:
Zeolites
(OH) and (NH) groups forming polynuclear structures. The involvement of zeolite oxygen in coordination
was postulated in the hybrid materials. The intrazeolitic copper, cobalt and nickel–SAPH complexes have
distorted tetrahedral, octahedral and square-pyramidal configurations, respectively. The zeolite encapsu-
lated complexes are thermally stable up to 800 °C except Cu(II) sample which is thermally stable up to
midpoint 428 °C. The assessment of the catalytic activity was performed by the use of the photo-degra-
Hydrazone complexes
Diffusion method
Catalytic activity
2 2
dation of acid violet-1 dye as a probe reaction in presence of H O as an oxidant. Decolorization of acid
II
II
violet-1 dye was examined under the same conditions whereas the unpromoted zeolite and Cu , Co ,
II
Ni –hydrazone complexes supported on zeolite showed 13% and 76%, 53%, 43% color removal, respec-
tively. The results revealed that, the zeolite encapsulated Cu(II) complex generally exhibited better cat-
alytic efficiency (76%) compared with other investigated zeolite encapsulated metal–hydrazone samples.
Ó 2011 Elsevier B.V. All rights reserved.
1
. Introduction
such hybrid materials have numerous applications including catal-
ysis, gas separation, artificial photosynthesis and photocatalysis
Zeolites are a class of crystalline aluminusilicates based on rigid
anionic frameworks with well-defined channels and cavities. The
[4–11]. Schiff bases contain the azomethine group (ARC@N),
including the employed hydrazone, can play a central role in devel-
opment of heterogeneous catalysis owing to the great synthetic
flexibility and they readily form stable complexes with most of
the transition metals taking into account their catalytic and biolog-
ical importance [12]. Thus, a substantial number of articles on the
preparation and characterization of M–Schiff base complexes in
the zeolite have been published [6–9,13]. A literature survey re-
vealed that salicylaldehyde phenylhydrazone (SAPH) has antioxi-
dant activity and can be used as an indicator for the titration of
organometallic species [14]. Nevertheless, some chelates of SAPH
+
+
2+
cavities contain exchangeable metal cations e.g., Na , K , Ca
,
etc. The synthetic faujasite (FAU) type zeolite (Y or X) has the most
widely studies on its utilizing as host materials. The FAU has a 12-
ring window of diameter 0.74 nm and internal cavity about
1
1.2 nm. Actually, entrapment of metal complexes into zeolite
leads to growing up the number of heterogeneous catalysts which
combine the advantages of homogeneous and heterogeneous cata-
lytic system, reduce the self-oxidation tendency of the complexes
and promote the catalytic activity by dispersion of the complexes
inside the zeolite pores. Heterogenization of metal complexes
known to be active in homogeneous catalysis can be achieved by
2
[M(SAPH) , M = Cu(II) and Ni(II)] were synthesized under tradi-
tional conditions and characterized on the basis of elemental anal-
ysis with confirming spectroscopically [15], no work on their
encapsulation in zeolite has been investigated besides the encap-
sulation process led to construction of different compositions and
structures.
(
i) polymerization of metal complex catalyst itself [1,2], (ii) immo-
bilization of the metal complex on insoluble support e.g., polymers
[
[
3], and (iii) encapsulating it in the nanocavity of e.g., zeolites
4–9]. Fortunately, a wide variety of metal complexes have been
successfully immobilized in a range of different zeolites where
Currently, to meet the demand of green chemistry, it is favor-
able to use H
reactions because H
water. The role of transition metal complexes is overviewed for the
2
O
2
as oxidant and H
2
O as solvent for the oxidation
⇑
Corresponding author.
E-mail address: ayman_haf5@yahoo.com (A.H. Ahmed).
2 2
O
does not produce any side-product besides
0
022-2860/$ - see front matter Ó 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.molstruc.2011.09.061

5
28
A.H. Ahmed, M.S. Thabet / Journal of Molecular Structure 1006 (2011) 527–535
iron, copper and chromium compounds, for which photoreactivity
is of crucial environmental importance. Attention is paid to these
complex systems, in which metal centers are photoreduced by or-
ganic matter under solar irradiation and re-oxidized by molecular
oxygen, i.e. to the systems, that play a part in the environmental
photocatalysis. The photoreduction is accompanied by simulta-
neous oxidation of organic matter, which plays a role of ligand
and/or sacrificial electron donor. Under favorable conditions a
complete photodegradation of the organic pollutants can be
achieved. The systems are more sophisticated due to concurrent
t
BET-plots and t-curves estimated the specific surface areas (SBET, S )
where the samples were thermally degassed at 200 °C for 2 h prior
to the adsorption measurements.
2.2. Preparations
2.2.1. Salicylaldehyde phenylhydrazone (SAPH)
The ligand is easily prepared in good yield from inexpensive
starting materials and is simple to isolate in pure form. It was pre-
pared according the method described in Ref. [14b]. Methanolic
solution of phenylhydrazine (11 mL, 0.1 mol) and salicylaldehyde
(10.5 mL, 0.1 mol) was refluxed for 2 h under constant stirring.
The immediately formed yellow–white solid was collected by vac-
uum filtration, washed repeatedly by ethanol to remove any excess
of reactants and finally dried in furnace at 80 °C for 3 h. The result-
Åꢀ
Å
Å
generation of active oxygen species, such as the O , HO , OH ,
2
2
ꢀ
2 2
2
H O , and HO , which are involved in the redox reactions of the
photocatalytic cycling and influence the pollutant degradation.
In this investigation, we described the synthesis and character-
ization of Y-zeolite encapsulated salicylaldehyde phenylhydrazone
(
SAPH) metal complexes [M = Co(II), Ni(II) and Cu(II)]. The struc-
ing ligand with the formula C13H12N O was recrystallized from
2
ture of the ligand chosen for the studies is depicted in Fig. 1. The
compositions and structures of the new zeolites, which are re-
garded as heterogeneous catalysts, were identified and tested for
photodecomposition of acid violet-1 dye. The texture of the zeo-
lites containing M(II)–SAPH complexes was described showing
the possibility of using them as heterogeneous catalysts in other
applications and in the same time to provide a conclusive evidence
for the successful occlusion of the metallocomplexes within the
zeolite matrix. The study is devoted on the zeolite encapsulated
SAPH complexes as they represent new materials did not study be-
EtOH and melted at 142 °C (lit.mp 140–142 °C) [15,17]. The ligand
structure was confirmed by IR spectroscopy and its purity was
checked by mass spectrometry. The mass spectrum of the free li-
+
gand exhibited a molecular ion peak (M value) at m/e = 212;
calc. = 212.25. SAPH is air stable and easily soluble in most of or-
ganic solvents e.g., ethanol, chloroform, acetone and benzene.
II
2
.2.2. Metal-exchanged zeolite (M –Y)
II
M –Y was generally prepared via the reversible ion exchange
process [9b,c], which can be described by the following chemical
equation.
II
fore in contrast to employed M –Y.
Na —ZeoliteðsÞ þ M2þðaqÞ ¡ M2þ—ZeoliteðsÞ þ 2Na ðaqÞ ½M
þ
þ
2
. Experimental
¼
Cu; Co and Niꢁ
2
.1. Materials and physical measurements
Seven grams of NaY was weighed out and treated at room tem-
perature with 1500 mL 0.01 M acetate solution of M(II) ion
[M = Cu, Co and Ni], the pH of the resulting heterogeneous mixture
was in the 5–6 range. The mixture was conducted for 48 h with
continuous stirring. After that, the powder was suction filtered
off using a büchner and washed thoroughly by distilled water to
remove the excess of adsorbed or unreacted ions till the washing
solution was free from any M(II) ion content. The zeolite sample
was then dried in air at room temperature for 24 h and finally
stored over saturated ammonium chloride solution to maintain a
constant humidity until required for use. The exchange level and
metal content for the obtained solids are shown in Table 1.
All the chemicals and solvents employed were of BDH or AR
quality and used without further purification. The chemicals in-
clude Cu(II), Co(II) and Ni(II) acetates, salicyalaldehyde and phen-
ylhydrazine. NaY zeolite (Lot No. D1-9915, HSZ-320N-NAA, Si/
Al = 5.6) was obtained from Toyota Company Ltd., Japan, and used
as received. The elemental analysis for carbon and nitrogen was
estimated on Perkin Elmer 2400 at Microanalytical Unit of Cairo
University, Egypt. The metal contents (w/w%) were determined
by complexometric titration of EDTA using xylenol orange indica-
tor, hexamine buffer and sodium fluoride as a masking agent for
the interfering aluminum ions result from disintegration of the
zeolite framework [16]. IR spectra were recorded as KBr pellet in
the range 200–4000 cm on a Mattson 5000 FT-IR spectrometer.
Mass spectrum of the ligand was recorded on Shimadzu-GC.MS-
QP 1000 EX using the direct inlet system at Cairo University, Egypt.
UV–Vis. spectra of the samples in Nujol mull were measured in the
range 200–1100 nm using a Perkin–Elmer lambda 35 UV–Vis.
Spectrophotometer. The mass susceptibility of the solid materials
(v) was measured with a magnetic susceptibility balance of mod-
els Johnson Metthey and Sherwood. X-ray diffractograms were re-
corded using a Philips PW1840 X-ray powder diffractometer with
Cu Ka target (k = 1.54 Å). Thermal analyses (TG, DTG, and DTA) un-
der flowing of dry nitrogen were carried out with a DTG-60 H ther-
mal analyzer at Cairo University, Egypt. The surface texture
characteristics obtained from nitrogen adsorption isotherms were
determined at ꢀ196 °C using a conventional volumetric apparatus.
II
II
II
2
.2.3. Zeolite encapsulated metal complexes (Cu , Co and Ni (SAPH)/
ꢀ1
Y)
The intrazeolitic metallocomplexes were prepared using a so-
lid–solid interaction technique by diffusing the ligand through
II
the pores of preactivated M –Y to form a large and rigid complex
becomes unable to escape from the zeolite cage (FL method). For
II
this purpose, an amount of M –Y (2.0 g) was first activated by
heating in a Pyrex shrink tube to 200 °C for 2 h in a vacuum of
ꢀ4
1
1
0
Torr and then cooled to room temperature. Approximately
II
.0 g of activated M –Y was intimately mixed with an excess of
SAPH ligand (2.0 g) in a glove bag under nitrogen atmosphere.
The finely powdered mixture was placed horizontally in a Pyrex
ꢀ4
shrink tube, evacuated again to 10 Torr for 10 min. and heated
with constant stirring at 135 °C for 4 h. After the reaction was com-
pleted whereby the ligand diffuses freely through the channels and
coordinates with metal ions, the furnace tube was cooled to room
temperature, carefully opened and the products were washed in a
beaker with successive portions of hot solvents (ethanol, acetone
and methylene chloride, respectively). The product sample was
then Soxhlet-extracted with acetone for 48 h at normal conditions
to remove excess ligand that remained in the cavities of zeolite as
well as located on the surface of zeolite along with neat complexes
Fig. 1. Chemical structure of SAPH ligand.

A.H. Ahmed, M.S. Thabet / Journal of Molecular Structure 1006 (2011) 527–535
529
Table 1
Physical and analytical data of SAPH and the zeolites used under investigation.
*
Sample label
Color
M.p /Dec. temp. (°C)
M (wt.%)
Exchange level (%)
M/C, M/N found/calcd.
v
g
(c.g.s.)
Product assignment
*
SAPH
NaY
White
White
142
–
–
–
–
77
57
68
–
–
–
–
–
–
–
Y
>300
>300
>300
>300
>300
>300
>300
Diamag.
II
ꢀ5
ꢀ5
ꢀ5
2 6
O) ]
2+–Y
Cu –Y
Pale blue
Pale pink
Pale green
Dark green
Pale brown
Buff
6.8
5.0
5.9
8.4
6.2
5.4
1.14 ꢂ 10
1.04 ꢂ 10
0.44 ꢂ 10
[Cu(H
[Co(H
[Ni(H
[Cu
[Co
[Ni
II
2+
Co –Y
2
O)
O) ]
2 6
6
]
–Y
–Y
II
2+
Ni –Y
–
II
ꢀ5
Cu (SAPH)/Y
0.16/0.15, 1.04/1.0
0.26/0.23, 1.8/1.5
0.25/0.23, 1.7/1.5
0.004 ꢂ 10
2
(SAPH)(H
(SAPH)(H
(SAPH)(H
2
O/O
O/O
O/O
z
)
z
)
z
)
4
]–Y
13]–Y
11]–Y
II
ꢀ5
Co (SAPH)/Y
–
–
1.02 ꢂ 10
0.42 ꢂ 10
3
2
II
ꢀ5
Ni (SAPH)/Y
3
2
*
Melting without decomposition.
formed on the surface, if any. Finally, the solid was dried for 4 h at
00 °C in oven.
In comparison to the colors of M –Y and SAPH, new colors of
M (SAPH)/Y composites have been acquired (Table 1). This observation
beside the final preparation showed a nonextractable color related to
SAPH complex by vigorous washing can be regarded as a direct evi-
dence of encapsulation of SAPH complexes inside the zeolite pores.
work interaction is usually weak in such case [18]. This fact in addition
to the postulated large diameter of 12-ring window belong to faujasite-
1
II
II
Y suggest the existence of the prepared M –Y samples (M = Cu, Co and
II
2+
2 6
Ni) in zeolite as aquo-complexes ([M(H O) ] ) [9c]. Furthers, inspec-
tion of Table 2 showed that there is a somewhat distortion or dealumi-
nation in the zeolite lattice upon encapsulation of SAPH complexes
owing to the changes in the positions, features and multiplicity of some
structure-sensitive bands related to NaY [18]. This can be elucidated as
follows: (1) The very weak pore opening band in NaY was varied to
2.3. Photocatalytic activity measurement
II
II
II
medium in Cu (SAPH)/Y, strong in Co (SAPH)/Y and weak with Ni (-
SAPH)/Y. (2) The most significant shoulder band attributed to
Photodecomposition experiments of acid violet-1 dye at kmax
ꢀ
1
m
asymTAO in NaY was shifted to lower frequency by 7 and 11 cm
for Cu (SAPH)/Y and Ni (SAPH)/Y respectively, in addition, it was split-
5
50 nm, (100 mL, 100 ppm) were carried out using UV Lamp
II
II
(
254 nm) of intensity 6 W. The suspension (catalyst + dye) that
ꢀ1
II
ted into two strong bands (1143 and 1099 cm ) in case of Co (SAPH)/
Y. As the zeolite-Y containing the complex is still retaining its crystal-
linity as observed from the IR spectra and demonstrated by XRD later,
the most probable to occur is the distortion. Perhaps the lower shift in
the position of the structure sensitive bands results from the weak
deformation in the framework. This deformation in the zeolite topol-
was stirred vigorously was left to equilibrate for 40 min in dark
prior to illumination with UV Lamp, to ensure attaining complete
adsorption and to monitor the change in dye concentration due
to adsorption. Exposing the suspension to UV irradiation was then
attained to stand on the photocatalytic activities of the catalysts.
The UV–Vis. spectrophotometer JASCO V-570 unit, serial No.
II
ogy arise from generation of MAO(zeolite) linkage in M (SAPH)/Y
2
9635 at scanning speed 4000 nm/mm was used for the determi-
samples.
nation of color intensity in the range of 190–700 nm. The calibra-
tion based on Beer–Lambert law was linear and used to quantify
the dye concentration. Control experiments were carried out using
UV irradiation without catalyst to check whether a direct photoly-
sis for the dye occurred or not. In fact, the obtained activity of this
experiment showed a very little effect on the dye degradation.
3.1.2. In comparison to free SAPH ligand
The bands due to the encapsulated complexes are weaker due
to a low concentration as seen from the metal contents (Table 1).
Thereby, the encapsulated complexes can only be observed in the
regions where the zeolite matrix does not absorb (1200–
3
. Results and discussion
Physical and analytical data of NaY, free SAPH, M –Y and M (-
ꢀ1
1
600 cm ). Indeed, FT-IR data pointed out SAPH can coordinate
to the metal ions via the azomithinic nitrogen (AC@NA), phenolic
oxygen (CAO) and (NH) group. This was concluded based on: (1)
the lower shift in the azomethine (C@N) group upon complexation
substantiates the involvement of the azomethine in coordination.
II
II
II
II
II
SAPH)/Y (MCu ,Co and Ni ) are listed in Table 1. The new hybrid
materials are insoluble in common organic solvents. The slightly
difference between the calculated and found (M/C, M/N) ratios in
case of M (SAPH)/Y samples (Table 1) is plausibly due to insignif-
icant unreacted part of M(II) ions in zeolite voids.
(
m
2) The higher frequency shift of the band assigned to phenolic
(CAO) stretching by chelation suggests the coordination through
II
the phenolic oxygen. Note the large shift to the higher frequencies
of the phenolic (CAO) is going from a hydrogen bonded structure
to a covalent metal bonded structure. In addition to the above,
3.1. Spectral and magnetic studies
the observation of
of Cu (SAPH)/Y reflects the deprotonation of OH which is proton-
ated in cases of Co (SAPH)/Y and Ni (SAPH)/Y owing to its disap-
pearance. (3) The obscure of
m
(OH)phenolic at nearly the same position in case
The IR spectra in the (4000–200 cmꢀ1) region provide informa-
II
II
II
tion regarding the coordination mode in the modified zeolites and
were analyzed by comparison with data of ligand (SAPH). The most
relevant bands and proposed assignments for free ligand along
II
m,d(NH) in Co (SAPH)/Y indicates the
deprotonation of this group while its shift towards lower side in
II
II
II
with its corresponding M (SAPH)/Y (M = Cu, Co and Ni) as well as
Cu (SAPH)/Y and Ni (SAPH)/Y suggests its deprotonation. In the
low frequency region of the spectra there are bands of moderate
intensity, which can probably assigned to the MAO and MAN
the host matrix are given in Table 2.
ꢀ
1
3
.1.1. In comparison to NaY
It was noticed that the IR spectra of M –Y and M (SAPH)/Y are dom-
vibrations at nearly 400–450 and 500–550 cm , respectively.
Occasionally, some of these bands are merged with the Y bands
(Table 2). The appearance of these bands supports the coordination
mode of ligand and confirms its interaction with the exchanged
metal ions. Bands appearing at 1496, 1418 (SAPH), 1457, 1435
II
II
inated by the Y zeolite bands assignable to surface hydroxyl groups,
internal and external vibrations of tetrahedral geometry of the type
(
4
Si, Al)O without any collapse in their crystallinity. As speculated,
+
II
II
ion exchange of Na ions by divalent cations would not change the
infrared spectral feature of the hydrated zeolite since cation-frame-
(Cu (SAPH)/Y), 1492, 1478, 1457 (Co (SAPH)/Y), and 1491, 1465
II
ꢀ1
(Ni (SAPH)/Y) cm are the usual modes of phenyl ring vibrations.

5
30
A.H. Ahmed, M.S. Thabet / Journal of Molecular Structure 1006 (2011) 527–535
Table 2
IR spectral data of SAPH, NaY and the encapsulated metallo-hydrazone complexes.
Sample
Internal vibrations
External vibrations
Adsorbed
water
m,d (NH)
d (OH)
phenolic
m(C@N)
m
(CAO)
d(OH) in
plane
phenolic
masymTAO
msymTAO TAObend DAR
Pore
msymTAO
masymTAO
opening
SAPH
NaYa
–
1032
–
720
–
463
–
–
–
–
–
3288, 1538 1360
1602
–
1272
–
–
–
576m 390vw
576m 381m
578m 354s
583m 371w
787m
1140sh
3456br,
1
3460br,
1623
3460br,
1623
–
–
638
II
3247,1520b 1353
Cu (SAPH)/ 1018
Y
716
722
713
458
462
460
787m
791m
789m
1133sh
1540
1556
1556
1321
1307
1319
1400
1400
1400
II
Co (SAPH)/ 1011
1143s,
1099s
1129sh
–
–
–
Y
II
3240c,
1524
Ni (SAPH)/ 1023
3430br,
1635
Y
a
b
c
Reported in literature [9a,c].
Emerged with (C@N).
Dominated by zeolite bands.
m
The previously bands corresponding to phenyl ring reveal small
shifts in the resulted complexes than free ligand, this is usual
due to the expected symmetry and electronic structure changes
upon complexation. Coordinated water in the host–guest materi-
transition showing the configuration around the metal ion of the
II
encapsulated complex. Cu (SALSC)/Y showed two bands at 553
and 824 nm assigned to charge-transfer (L ? M) and 2
B
2
? E
2
2
transition in a pseudo tetrahedral structure around the Cu(II) ions
II
II
als, M (SAPH)/Y, was supposed based on the appearance of the
[20]. Co (SAPH)/Y sample exhibited two absorption bands at 544
ꢀ1
2
4
bands attributed to d(OH) in plane at 1400 cm [19]. Other bands
and 741 nm which are probably assigned to
T
1g ? T1g(P) and
2
4
ascribed to coordinated water that would be expected to appear at
T1g ? A2g in an octahedral geometry around the Co(II) ions
[21a,b]. Ni (SAPH)/Y sample revealed two bands at 719 and
515 nm attributed to E(P) ? B (F) and E(P) ? E(F) transitions,
2
ꢀ1
II
6
00–1100 and 1600–1680 cm have not been noticed owing to
3
3
3
3
their overlap with Y bands.
The UV–Vis. Spectra confirm the incorporation of metalloSAPH
complexes into the zeolite NaY super cages. Fig. 2. shows the
absorption spectra of ligand (SAPH) along with its related M (-
respectively. The observation of these bands suggests a prevailing
square-pyramidal configuration around Ni(II) ion [21a].
II
Indeed, magnetic measurements for this type of materials give
limited information because the molecular weights for these heter-
ogonous samples are undetermined and the encapsulated com-
plexes are not neutral by which we can ignore the diamagnetic
effect of zeolite. We have encapsulated cationic complexes neutral-
ized by the negative charges on the crystalline aluminuslicates
SAPH)/Y. The main characteristic bands for SAPH ligand are ob-
served at 399, 349, 324 and 245 nm, which are assigned to
ꢃ
ꢃ
ꢃ
n ?
p
(AC@NA),
p ? p (AC@NA), p ? p (phenolic ring) and
ꢃ
p?p
(phenyl ring), respectively. Apart from L and NaY bands,
II
the investigated M (SAPH)/Y exhibited new bands related to d–d
(
zeolite-Y) and connected in the same time with the zeolite oxygen
as confirmed from the IR data. Thereby, it becomes impracticable
to calculate the effective magnetic moments ( eff) that require
the knowledge of the molecular weight assigned to the occluded
complexes [9a,b,d,e]. The very low paramagnetic value of for
l
v
g
II
Cu (SAPH)/Y (Table 1) indicates that the Cu(II) ions are so close
to each other that leads to incomplete quenching of the spin mo-
ments of the ions. This means that the supposition of CuACu bond
in the molecular structure is not excluded specially the obtained
v
g
value agrees to a great extent with this conclusion. But the pro-
posed structure shown in Scheme 2 grants the formation of stable
five membered chelate ring around the copper ion along with
approaching of the two copper ions that quenches of the spin mo-
II
515
ments. The paramagnetic value of
v
g
in case of Co (SAPH)/Y
719
(d)
(Table 1) is consistent with high spin octahedral geometry around
5
44
the Co (II) ion. This configuration is preferred than the low spin on
the basis: (1) the ligand has strongly electronegative donor atoms
7
41
553
(oxygen, nitrogen) and has little tendency to form
p bonds with the
(
c)
metal ions, (2) if the low spin octahedral complex was formed, the
6
1
high energy e
g g
orbitals must contain one electron [(t2g) (e ) ] and
8
24
this makes the octahedral complex too unstable to exist. This fact
(
b)
II
3ꢀ
allows [Co (CN)
5
]
is formed instead of an octahedral
II
4ꢀ
[
Co (CN)
6
]
in case of p acceptor ligand as cyanide ion. Indeed,
(
a)
1000
thermal analysis (DTA curve) studied later supports this point
II
referring to the high thermal stability of Co (SAPH)/Y. Accordingly,
the room temperature magnetic moment assigned to the high spin
4
00
600
800
II
5
2
Co (SAPH)/Y [(t2g
)
(e
g
) ] is expected to be found near 3.9 B.M.
Wavelength (nm)
(
spin only moment) owing to the existence of three unpaired elec-
II
II
trons.
Also,
the
paramagnetic
nature
of
square-
Fig. 2. Electronic spectra of (a) SAPH, (b) Cu (SAPH)/Y, (c) Co (SAPH)/Y and (d)
II
II
Ni (SAPH)/Y.
pyramidal Ni (SAPH)/Y that indicated from the v value (Table 1)
g

A.H. Ahmed, M.S. Thabet / Journal of Molecular Structure 1006 (2011) 527–535
531
Scheme 1. Synthesis and postulated structures of zeolite encapsulated metallo-hydrazone complexes.
(d)
331
220
(c)
331
220
(b)
331
220
Scheme 2. Proposed mechanism of the photocatalysis.
(a)
220
331
4m
suggests a high spin arrangement (S = 1). This C symmetry is also
proposed on the basis of the most favorable ligands for high spin 5-
coordinate nickel complexes have strongly electronegative donor
0
20
40
atoms (oxygen, nitrogen, halogens) and are weak
[
p
acceptor
21c]. Expected magnetic moment for Ni (SAPH)/Y sample is be-
lieved to be correct near 2.8 B.M. (spin only value). The comparable
2θ
II
II
II
Fig. 3. X-ray diffraction patterns of (a) NaY, (b) Cu (SAPH)/Y, (c) Co (SAPH)/Y and
II
(
d) Ni (SAPH)/Y.
II
II
values of
g
v assigned to Co , Ni –Y with that of their corresponding
complexes may be taken as an argument for the absence of MAM
bond in such cases.
In the light of the forgoing results discussed above, the diffusion
synthesis method showing the most likely structures of accommo-
dated metalloSAPH chelates inside the zeolite matrix can be
represented by Scheme 1. Negative zeolite oxygen and deproto-
nated ligand compensate the positive charges on the metal ions.
At the first glance, the resulting structures may be unacceptable
due to the presence of more than one metal ion. But in fact they

5
32
A.H. Ahmed, M.S. Thabet / Journal of Molecular Structure 1006 (2011) 527–535
B
A
co dta
Exo.
↑
↓
DTA
Exo.
↑
↓
DTcAu
Endo.
Endo.
DTG
0.0
200
600 DT8G00
400
cu tg
TG
TG
dtg cu
0
.0
200
400
600
800
0.0
200
400
600
800
Temp. (°C)
Temp. (°C)
C
Ni dta
Exo.
↑
↓
DTA
Endo.
2
00
400
600
800
DTG
TG
0
.0
200
400
600
800
Temp. (°C)
II
II
II
Fig. 4. TG, DTG and DTA curves of (A) Cu (SAPH)/Y, (B) Co (SAPH)/Y and (C) Ni (SAPH)/Y.
were presumed on the basis: (1) the elemental analysis was re-
peated, (2) an excess of ligand was added, (3) the washing process
was performed vigorously (4) the ligand has versatile coordination
sites and (5) the preparation circumstances are untraditional. In
spit of the chemical structures are well authenticated by single
crystal X-ray, we cannot isolate a single crystal from heterogonous
materials. Otherwise, if we try to separate the encapsulated meta-
l(II)SAPH complexes or prepare them in free state, we expect to ob-
tain differ complexes since (1) the resulting data ascertained the
involvement of zeolite oxygen in coordination, (2) the encapsu-
lated metal(II)SAPH complexes are cationic complexes neutralized
by negative charges on zeolite framework and not neutral com-
plexes, (3) In many cases, the entrapment of the complex in the
zeolite leads to construction of new composition and structure
differs from the free one owing to the zeolite restriction, (4) the
spatial constraints imposed by the dimensions of the zeolite cage
leads to the distortion in the immobilized complex structure and
allow approaching of ligand to the metal ions thus the probability
of polynucleating bonding increases specially when number of me-
tal ions presented in zeolite cavities are in excess compared with
the ligand molecules considering the size of ligand molecule is
larger.
3.2. XRD studies
II
Further arguments confirming the accommodation of M (SAPH)
complexes (M = Cu, Co and Ni) inside the zeolite cages were pro-
vided by XRD technique. X-ray diffraction patterns (Fig. 3) of NaY

A.H. Ahmed, M.S. Thabet / Journal of Molecular Structure 1006 (2011) 527–535
533
2
20 peaks. This of course indicates that the entrapped large metal-
locomplexes displaced the sodium ions from their random posi-
tions in the super cages to locations of sodalite and center of a
single six-ring (S6R) [24] residing inside the large cavity of zeolite
Y. Worthy mention, the changes in the charge distribution within
the cavities and channels leads to alter the adsorption behavior
as well as the catalytic activity.
3.3. TGA and DTA studies
In fact, execution the percentage decomposition of components
of Cu(II), Co(II) and Ni(II) complexes and correlate it with total
molecular weight of complexes would expect to be inaccurate
and the calculations are not adequate. The reason for this arises
from the fact that the molecular weights of the samples are unde-
termined as we deal with composite materials. We may have sev-
eral numbers of encapsulated complex molecules dispersed in one
supercage or one unite cell of zeolite. Nonetheless, thermal analy-
sis can provide some information about the influence of zeolite
shielding on the thermal stability of metalloSAPH complexes. Ther-
mograms (TG, DTG and DTA) of the investigated hybrid materials
II
(
M (SAPH)/Y, M = Cu, Co and Ni) have been studied and shown in
Fig. 4.
II
TG curve of Cu (SAPH)/Y showed two sets of bands in the 35–
1
50 and 150–450 °C regions. DTA curve agreed with the above
result and showed one endothermic peak at 75 °C and another
exothermic peak at 428 °C. The former is due to water removal
from the zeolite-Y voids while the latter reflects the complex
decomposition because it is accompanied by weight loss as clear
II
from the TG curve. For Co (SAPH)/Y, TG curve exhibited also two
decomposition stages starting at 50 and 200 °C for the desorp-
tion of water from the interacrystalline voids of zeolite. DTA
curve did not show any weight loss exothermic peak assignable
II
II
2
Fig. 5. N -adsorption–desorption isotherms of (a) Cu (SAPH)/Y, (b) Co (SAPH)/Y
and (c) Ni (SAPH)/Y.
II
II
to the decomposition of Co (SAPH) up to 800 °C referring to its
II
high thermal stability. In the case of Ni (SAPH)/Y, TG curve
as well as the zeolite encapsulated metallocomplexes were
recorded at 2h values between 6° and 70°. The peaks observed in
all patterns are essentially similar and no new peaks were de-
tected. As the XRD is a surface analytical technique and there is a
showed three stages of decomposition starting at 30, 110 and
270 °C related to the removal of trapped and intra-zeolite water.
The first two peaks are accompanied by endothermic effect
while the third was not observed. No exothermic effect has been
noticed by DTA measurement within the range 30–800 °C con-
sidering the high thermal stability of the occluded Ni(II)
complex.
Thermal analysis conspicuously indicates that the formation of
the complexes inside the zeolite cages increases their thermal sta-
bility up to a noticeable degree due to the zeolite shielding effect.
II
difference in colors of SAPH, NaY and M –Y by encapsulation (Ta-
ble 1), the obscure of new peaks attributed to neat complexes pro-
vides an evidence to the residing of the metallocomplexes inside
the zeolite cavity and not on the external zeolite surface. Interpre-
tation of the obtained XRD data in accordance to the published NaY
[
9e] can be shown as follows. It was reported that the diffraction
pattern for NaY could be fitted in terms of a cubic lattice with
220 > I311 [9e,22]. Our data showed that the crystallinity of zeolite
I
3.4. Surface studies
Y is almost preserved after entrapment of the SAPH complexes in
it. The relative intensities of the 311, 220 reflections in published
The texture of a catalyst surface, namely, the specific surface
area and pore geometry are of prime importance in determining
the activity, sometimes, also the selectivity of the solid catalyst
NaY (I220 > I311) was varied upon inserting the complexes, i.e.
II
I
311 > I220 in case of M (SAPH)/Y patterns. This can be explained
on the basis the replacement of sodium cations in NaY by large
[
25]. From this point of view, surface texture of the synthesized
II
complex molecules (M (SAPH)) leads to disturb the random distri-
samples is necessary to be considered.
II
bution of small extra framework cations [23] and this change in the
location of small cations influences the relative intensities of 311,
Nitrogen isotherms of M (SAPH)/Y (M = Cu, Co and Ni), Fig. 5,
have been carried out and compared with that of the published
Table 3
Some surface characteristic data of NaY and its corresponding zeolite encapsulated complexes.
2
2
3
mic (cm3 g)
2
2
2
2
Sample label
BET (m /g)
S
t
(m /g)
V
p
(cm /g)
í (Å)
V
V
mes (cm /g)
S
mic (m /g)
S
wide (m /g)
S
ext (m /g)
Microporsaty %
a
NaY
902
502
606
597
758
455
606
598
0.80
0.56
0.68
0.59
22.2
27.7
28.1
24.7
0.59
0.30
0.66
0.49
0.21
0.26
0.02
0.10
226
268
588
156
676
234
18
90
74
54
97
83
II
Cu (SAPH)/Y
Co (SAPH)/Y
Ni (SAPH)/Y
212
201
101
II
II
18
t p
Note: (SBET) BET-surface area; (S ) surface area derived from Vl–t plots; (Smic) surface area of micropores; (Smes) surface area of mesopores; (Sext) external surface area; (V ) total
pore volume; (Vmic) pore volume of micropores; (Vmes) pore volume of mesopores; (í) mean pore radius.
a
Reported in literature [9c].

5
34
A.H. Ahmed, M.S. Thabet / Journal of Molecular Structure 1006 (2011) 527–535
NaY [9c] which is typical of microporous solid and type I of Bru-
nauer classification [26]. Some surface parameters of NaY and its
related encapsulated complexes have been collected in Table 3.
80
60
40
C ua /Y
N bi /Y
Co c/ Y
Yd
II
II
The obtained data showed that Cu (SAPH)/Y, Co (SAPH)/Y and
II
Ni (SAPH)/Y materials have a Brunauer classification of type II
(
without hystresis loop), type II (with hystresis loop) and a med-
ium type between I and II (without hystresis loop), respectively.
Perhaps, the absence of hystresis loop indicates the nonporous nat-
ure due to the filling of the zeolite pores by SAPH complexes, but
their large computed surface areas (Table 3) ascertain they still
have porous natures. In comparison to the published NaY iso-
2
0
0
II
therms, all the prepared M (SAPH)/Y solids exhibited a decrease
0
10
20
30
40
50
60
70
in the N
2
adsorption capacity pointing to filling of the zeolite pores
Time (min)
by metal complexes. On the other hand, the Vl–t construction of
II
Fig. 6. Effect of time on the degradation of acid violet-1 dye in the presence of (a)
Cu (SAPH)/Y, (b) Ni (SAPH)/Y, (c) Co (SAPH)/Y and (d) NaY zeolites.
M (SAPH)/Y samples exhibited (i) a little upward deviation in cases
II
II
II
II
II
of Cu (SAPH)/Y and Ni (SAPH)/Y acquiring a wide porosity while
(
II
ii) an upward and downward deviation for Co (SAPH)/Y indicating
the existence of wide and narrow pores mixture. The specific sur-
face areas (S ) for these composite materials were determined from
t
1
00
the Vl–t plots and are in close agreement with (SBET) indicating the
correct choice of the standard t-curves. As the zeolite framework
structure did not collapse by encapsulation as shown from the IR
and XRD patterns, the reduction of surface areas and total pore vol-
umes of modified zeolites upon introducing the metallohydrazone
complexes provides a direct evidence for the existence of the com-
plexes inside the cavities and in the same time refers to the filling
degree of the zeolite pores.
8
6
4
2
0
0
0
0
0
Cua /Y
Coc/Y
Nib/Y
Y d
3.5. Photocatalytic activity
0
10
20
30
40
50
60
70
No disappearance of acid dye was observed without UV irradi-
Time (min)
ation. A diverse disappearance of acid dye could only be observed
with the simultaneous presence of different samples and of UV
light, as shown in Fig. 6. This indicates that the system is working
II
II
Fig. 7. Decolorization of acid violet-1 dye by (a) Cu (SAPH)/Y, (b) Ni (SAPH)/Y, (c)
Co (SAPH)/Y and (d) NaY samples.
II
II
in a real photocatalytic regime. Co (SAPH)/Y sample showed a pho-
II
tocatalytic activity close to that has been exhibited by Ni (SAPH)/Y
complex. This may be due to the immobilization on the interior
and external surface of the support. Under the same conditions,
0
.5
II
II
II
the parent zeolite and Cu , Co , Ni (SAPH)/Y showed 13% and
6%, 53%, 43% color removal of acid dye, respectively. It is worth
0
7
to mention that, degradation of azo-dye by some transition metal
oxides supported on ZSM-5 zeolite characterized by a similar
behavior [27]. Under UV, Fig. 7, acid violet dye gets excited and
can cede an electron to the valence band of metal-centered orbital
-0.5
-1
-1.5
Å
via an attack by OH radicals [28]. Under visible light, only acid vio-
a
b
c
d
let dye becomes excited with the promotion of an electron in an
upper orbital, whose relative energy level enables the transfer of
one electron into the conduction band of the iron in the catalyst.
The present photo-bleaching of acid violet dye only corresponds
to decolorization by loss of conjugation of the double bonds in
the whole molecule induced by the electron transfer to complex.
The data obtained within the first 30 min, Fig. 8, were used for ki-
netic correlation according to pseudo first-order equation [ln(C/
-2
0
5
10
15
30
40
50
60
Time (min)
II
II
II
Fig. 8. Pseudo first-order plots of (a) Cu (SAPH)/Y, (b) Ni (SAPH)/Y, (c) Co (SAPH)/Y
and (d) NaY for acid violet degradation at specific conditions.
C
o
) = k
a
t] [29,30], and the apparent first-order rate constants (k
a
)
Table 4
Kinetics rate of the dye removal using the catalytic oxidation.
are listed in Table 4. The catalytic activities follow the order of
II
II
II
II
K (min 1
ꢀ
)
R2 correlation coefficient
Cu (SAPH)/Y > Co (SAPH)/Y > Ni (SAPH)/Y > NaY. The Cu (SAPH)/
Y sample has the highest acid dye decolorization capacity, whose
Sample
NaY
0.0341
0.2593
0.1708
0.1441
0.9694
0.9708
0.9652
0.9739
ꢀ
1
ꢀ1
k
a
is 2.59 ꢂ 10 min , which is higher than reactions catalyzed
CuII(SAPH)/Y
II
II
II
by Co (SAPH)/Y and Ni (SAPH)/Y. The main reaction mechanism
for decolorization of dye can be described by Scheme 2 and eluci-
dated by the following equations [29–32]:
Co (SAPH)/Y
II
Ni (SAPH)/Y
Dye þ h
v
! dyeꢃ
ð1Þ
ð2Þ
ꢀ
H
2
O
2
þ CuðIIÞ sites ðe Þ ! CuðIÞ sites
þ Highly oxidative radicals
ꢀ
Å
þ
ð3Þ
MðIIÞ site þ dye ! MðIÞ sites ðe Þ þ dye

A.H. Ahmed, M.S. Thabet / Journal of Molecular Structure 1006 (2011) 527–535
535
Å
þ
Highly oxidative radicals þ dye
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[
!
CO
2
þ H
2
O þ Mineralization Product
ð4Þ
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[
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(
(
(
b) A.H. Ahmed, J. Appl. Sci. Res. 3 (12) (2007) 1663;
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!
deactivated radicals þ CuðIIÞ sites
ð5Þ
ð6Þ
Ådyeþ þ CuðIÞ sites ! dye þ CuðIIÞ sites
Eqs. (1)–(4) describe the formation of highly oxidative radicals
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[
gand [M = Cu(II), Co(II) and Ni(II)] can be accommodated in the
super cages of zeolite-Y by FL method without any strain. Spectro-
scopic techniques, chemical analysis, magnetism, thermogravimet-
ric and XRD patterns as well as surface area and nitrogen
adsorption measurements prove to be essential tools for identify-
ing and characterizing the metal(II) species formed inside the zeo-
lite-Y. The results showed that, SAPH can coordinate to Cu(II),
Co(II) and Ni(II) ions through the (C@N), phenolic (OH) and (NH)
groups forming numerous structures around the central metal
atom. The resulting compositions and structures for the encapsu-
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conditions. The involvement of zeolite oxygen (Oz) in coordination
was suggested assuming the change in the positions and features
of some zeolite sensitive bands. The immobilized SAPH complexes
have greater thermal stability due to the zeolite shielding. It is
authenticated by catalytic activity results that, decolorization of
dye is facilitated by presence of zeolite encapsulated Cu(II), Co(II)
(
(
5) (2001) 793;
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[
[
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showed that Cu (SAPH)/Y is better photocatalyst for decolorization
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